WO2022049409A1 - Express diagnosticum for sars-cov-2 - Google Patents

Express diagnosticum for sars-cov-2 Download PDF

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WO2022049409A1
WO2022049409A1 PCT/IB2020/058162 IB2020058162W WO2022049409A1 WO 2022049409 A1 WO2022049409 A1 WO 2022049409A1 IB 2020058162 W IB2020058162 W IB 2020058162W WO 2022049409 A1 WO2022049409 A1 WO 2022049409A1
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antibody
antibodies
cov
zone
sars
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PCT/IB2020/058162
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French (fr)
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Ilya Vladimirovich DUKHOVLINOV
Ekaterina Alekseevna FEDOROVA
Anna Igorevna SAENKO
Evgenii Leonidovich CHIRAK
Vladimir Vladislavovich KOPAT
Nikolai Nikolaevich KOLMAKOV
Aleksandrs MEZECKIS
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Sia Terragen
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Priority to PCT/IB2020/058162 priority Critical patent/WO2022049409A1/en
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K39/00—Medicinal preparations containing antigens or antibodies
    • A61K39/12—Viral antigens
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/005—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from viruses
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/08—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from viruses
    • C07K16/10—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material from viruses from RNA viruses
    • C07K16/1002—Coronaviridae
    • C07K16/1003—Severe acute respiratory syndrome coronavirus 2 [SARS‐CoV‐2 or Covid-19]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
    • G01N33/54366—Apparatus specially adapted for solid-phase testing
    • G01N33/54386—Analytical elements
    • G01N33/54387—Immunochromatographic test strips
    • G01N33/54388—Immunochromatographic test strips based on lateral flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/569—Immunoassay; Biospecific binding assay; Materials therefor for microorganisms, e.g. protozoa, bacteria, viruses
    • G01N33/56983—Viruses
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2319/00—Fusion polypeptide
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2319/00—Fusion polypeptide
    • C07K2319/40—Fusion polypeptide containing a tag for immunodetection, or an epitope for immunisation
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N2770/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses positive-sense
    • C12N2770/00011—Details
    • C12N2770/20011—Coronaviridae
    • C12N2770/20022—New viral proteins or individual genes, new structural or functional aspects of known viral proteins or genes
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N2770/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses positive-sense
    • C12N2770/00011—Details
    • C12N2770/20011—Coronaviridae
    • C12N2770/20034—Use of virus or viral component as vaccine, e.g. live-attenuated or inactivated virus, VLP, viral protein

Definitions

  • the invention relates to molecular biology, biotechnology, medicine and can be used for express diagnostics of SARS-CoV-2.
  • Coronaviruses are a large family of viruses that cause illness from a common cold to more serious illnesses, such as the Middle East respiratory syndrome (MERS-CoV) and severe acute respiratory syndrome (SARS-CoV).
  • MERS-CoV Middle East respiratory syndrome
  • SARS-CoV severe acute respiratory syndrome
  • the new coronavirus (nCoV, COVID-19, SARS-CoV-2) is a new strain that has never been detected in humans before [https://www.who.int/ru/health-topics/coronavirus/coronavirus].
  • a feature of this strain is the rapid spread from person to person, as well as the complex course of the disease.
  • SARS-CoV-2 belongs to Coronaviridae family of the Beta-CoV B line. It is a single-stranded RNA-containing virus. The epithelium of the upper respiratory tract and epithelial cells of the stomach and intestines are the entrance gate of the pathogen. The penetration of SARS-CoV-2 into target cells that have angiotensin converting enzyme type II (ACE2) receptors is the initial stage of infection. However, the type II alveolar cells of lungs (AT2) are the main target of the virus is, which is decisive in the development of pneumonia [World Health Organization. Clinical guidelines for the management of patients with severe acute respiratory infection suspected of being infected with a novel coronavirus (2019-nCoV). Interim recommendations.
  • ACE2 angiotensin converting enzyme type II
  • the reverse transcription PCR method has limitations for clinical diagnosis and treatment despite its wide applicability [Yu F., Yan L., Wang N. Quantitative Detection and Viral Load Analysis of SARS-CoV-2 in Infected Patients // Clin. Infect. Dis. 2020]. Its relatively low sensitivity, duration and labor intensity are the disadvantages of this method. A potentially high level of false negative results is reported for this testing method [Li Y., Yao L., Li J. Stability Issues of RT-PCR Testing of SARS-CoV-2 for Hospitalized Patients Clinically Diagnosed with COVID-19 // J. Med. Virol. 2020]. The specified disadvantages do not allow using the PCR-based method for rapid diagnosis of coronavirus infection.
  • the purpose of the present invention is to create a test for rapid diagnostics of SARS-CoV-2, which will allow from the first days of infecting to detect infected patients and asymptomatic carriers quickly, simply and reliably, for preventing transmission of the virus and ensuring timely treatment of patients.
  • test strip and an express diagnosticum containing it for express diagnostics of SARS-CoV-2.
  • the test for antibodies to coronavirus described above can be considered a prototype with a long stretch of imagination.
  • the technical result consists mainly in identifying the presence or absence of the virus from the first days of infection assumption due to the fact that the test is aimed to detect SARS-CoV-2 directly, and not the immune response to it, which appears later, and is sensitive even to low concentrations of the virus.
  • the technical result of the proposed invention is the ability to obtain an accurate result within 10-15 minutes.
  • the mentioned technical result is achieved by the fact that the test system for determining SARS-CoV-2 according to the invention is based on the method of immunoprecipitation, in which viral particles are detected using stained specific antibodies. It is also achieved by the fact that there is no long-term pre-preparation of a sample for analysis, only 10-15 minutes pass from the intention to conduct a test, if it is available, till getting the result, unlike the 15 minutes for test for antibodies, which is preceded by at least another 15 minutes for blood sampling and preparation of sample for analysis.
  • the technical result is also the ability to determine the presence of SARS-CoV-2 even at home – out of laboratory - for self-monitoring of health.
  • This technical result is achieved by the fact that a sample of fluid from the nasopharynx and/or oropharynx is the main type of biomaterial for research, but other biological liquids can also be studied.
  • the technical result is also in the accuracy of determining the presence or absence of coronavirus in the test sample. This is achieved by the fact that the test is aimed at detecting the virus by a direct method - i.e. the technology is used which allows to evaluate exactly the virus presence, and not the immune response induced by it.
  • the technical result also consists in specificity, due to the specificity of antibodies used in the test exclusively for SARS-CoV-2. What is important is that these antibodies will not interact with the body's molecules that bind to ACE2, which means the absence of probability of a false positive result.
  • the technical result also consists in reliable functioning, reducing the number of false positive and false negative results by increasing the specificity and accuracy of the test, due to the technical characteristics of the test system elements.
  • the technical result also consists in simplifying and reducing the production cost of the test system by avoiding the establishment of large-scale production and processes of purification and folding of the recombinant protein in vitro due to the fact that a large amount of antibodies is required for the production of the test.
  • the production of antibodies using animals is more cost effective than of a recombinant protein being correctly folded with sites available for antibody binding; they can be produced in large amounts at a lower cost.
  • the technical result is also in the increasing of the self-diagnostics availability in the population, due to the simplicity of the analysis, especially by using only a test strip with an insulating coating in one of the variants, without using any additional objects. This also leads to a technical result of reducing the amount of waste.
  • the technical result also consists in expanding the range of methods for diagnosing coronavirus.
  • This test system will allow to detect coronavirus in case of unwilling or impossibility of using analogues due to their disadvantages described above, or banal logistical problems or policy features.
  • New original objects used to obtain test strips and diagnosticum are proposed also.
  • the technical result from the use of these objects is the obtaining of the test strip and the express diagnosticum according to the invention.
  • a fusion protein and a genetic construct are also proposed that provide the synthesis of this fusion protein in a producing organism for use in diagnosing coronavirus infection.
  • An antibody of the invention binds to such fusion protein. Binding occurs to a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
  • This group of inventions will increase the chances of accelerating the fight against this infection due to the fact that the problem of the new coronavirus is very acute, and not many manage to bring a test system to the market, and the effectiveness and accuracy of analogues allow to consider the creation of alternatives actual.
  • the present invention is an express diagnosticum for SARS-COV-2, which allows to determine the presence of SARS-CoV-2 in a sample of biological material by the immunoprecipitation method.
  • Any biological liquid for example, material obtained by taking a swab from the nose, nasopharynx and/or oropharynx, bronchial lavage water obtained by fibrobronchoscopy (bronchoalveolar lavage), (endo) tracheal, nasopharyngeal aspirate, sputum, biopsy or autopsy lung material, whole blood, serum, urine can be the biological material for research.
  • the material obtained by taking a swab from the nasopharynx and/or oropharynx, or simply saliva is the main type of biomaterial.
  • Whole blood must be coagulated prior to testing, and serum can be applied directly to the test strip.
  • Express diagnosticum contains a test strip described in detail below, enclosed in a case, a device for taking a sample, and, in one of the embodiments – a container with a liquid for dissolving the sample. It can be a kit of 2 to 3 mentioned components, or a device.
  • the case of the test strip can be connected to a device for collecting a sample, the latter can be connected with a removable container with a liquid to dissolve the sample.
  • the container with a liquid for dissolving the sample may have a conical lid, which, after dissolving the sample, can be cut off and used for the convenience of applying the obtained liquid to the test strip.
  • the sampling device is represented, for example, by a cotton swab, a cotton bud, a spatula or a pipette, but is not limited to them. It can be used to collect saliva, blood, and other biological fluids.
  • the diagnosticum may also contain a scarifier and disinfectant material, such as an alcohol wipe, for blood sampling.
  • the liquid for dissolving the sample can be a buffer solution, such as isotonic saline (0.9%NaCl) or PBS (0.9% NaCl in a phosphate buffer), but is not limited to them.
  • the transfer of viral particles from a sample collection device, such as a swab, into the liquid phase is the purpose of the sample dissolving liquid – the washout solution.
  • a sample collection device such as a swab
  • blood is the sample, then either a mixture of preferably coagulated blood with a buffer is applied, or a buffer is applied to a drop of blood applied to the test.
  • TCID 50/ml value which shows the viral load.
  • the average viral RNA load when a sample is taken from nasopharynx/oropharynx, is 6,76 ⁇ 10 5 copies per investigated sample up to 5 days, maximum 7,11 ⁇ 10 8 copies per investigated sample.
  • the average viral load in sputum is 7 ⁇ 10 6 copies per ml, with a maximum of 2,35 ⁇ 10 9 copies per ml.
  • the test will be sensitive with a sample viral load of 10 3 copies or more.
  • the test strip is represented by a strip of the underlying material, on which functional zones represented by carriers and active agents are located.
  • the layout of the functional zones on the test strip is shown in FIG. 1 (A): zone 1, with an overlap on zone 2 or up to it; zone 2, with an overlap on zone 3 or up to it; zone 3, with the edges under zones 2 and 4 or up to them; zone 4, with an overlap on zone 3 or up to it.
  • the fluid flow is carried out by capillary forces.
  • the low wettability of the material - hydrophobicity – is the main requirement for the strip of the underlying material – for the substrate.
  • a plastic with a wetting angle greater than 80 is considered a hydrophobic material.
  • the first functional zone - sample application zone - is represented by a hydrophilic material that comes into contact with the sample for analysis.
  • the separation of large contaminating particles (cells and their debris), capture of viral particles from the sample and their transfer with the fluid flow further to the conjugation zone are the tasks of this zone.
  • a high capillary absorbency determined by the migration distance more than 10 mm/min is the main criterion for the material used in this zone. For example, it can be a "pillow" of cellulose, obtained by pressing layers of filter paper, or just chromatographic paper, but not limited to them.
  • the second functional zone, or conjugation zone is represented by a carrier made of a hydrophilic material that transfers liquids well, while weakly adsorbing proteins, which is coated with specific colored antibodies, such as, rabbit antibodies, conjugated with chromatophore particles – complexes of specific antibody(ies) with a chromatophore.
  • a carrier material has an antibody binding value of less than 30 ⁇ g/cm 2 , optimally - about 20-25 ⁇ g/cm 2 , and is represented, for example, by cellulose acetate.
  • this parameter is >200 ⁇ g/cm 2 for antibodies and about 120 ⁇ g/cm 2 for proteins among the materials binding protein molecules well, such as nitrocellulose and nylon.
  • Specific antibodies are obtained from the serum of animals, such as rabbits, but not limited to them, immunized with a recombinant polypeptide consisting of several SARS-CoV-2 antigens - a fusion protein of the invention - or a genetic construct for its synthesis in the cells of the producing organism.
  • the polypeptide, or plasmid or viral DNA is produced in the culture of bacteria, for example, E. coli, B. subtilis, but not limited to them, the linear genetic construct - by PCR using plasmid or viral DNA as a matrix, then they are purified and used to immunize animals.
  • Specific monoclonal or polyclonal antibodies are isolated from the serum obtained from animals, such as goat or rabbit. In this way, it is possible to obtain antibodies in large amounts.
  • a composition is obtained comprising antibodies in an effective amount for use in diagnostics of the presence of SARS-COV-2 by mixing them with the target additive.
  • the resulting antibody composition is divided into two aliquots, one of which is marked with a chromatophore, for example, with colloidal gold or colored latex beads, but not limited to them - these are specific colored polyclonal or monoclonal antibodies for the second functional zone. Another aliquot is used for the third functional zone, more precisely, for 3.1 zone.
  • a liquid containing viral particles wets the second zone and dissolves the complexes of antibodies with a chromatophore particle, leading to the formation of colored complexes of antibody with viral particle, which, with a stream of liquid, enter the further – the precipitation zone.
  • the chromatophore-antibody complex is a “ball” of the chromatophore, “covered” with antibodies (see Fig. 1 A, zone 2). If there is a virus in the test sample, these particles form a complex with the virus through the bound antibodies, in the conjugate zone (see Fig. 1 B, zone 2). If colloidal gold is used as a chromatophore, there are approximately 50-100 antibody molecules per particle.
  • the third functional zone consists of a nitrocellulose membrane, represented by two regions - one (see Fig. 1A, zone 3.1) is coated with unlabeled antibodies from the second aliquot - specific to the proteins of the new coronavirus, another one (see Fig. 1 A, zone 3.2) is coated with the secondary antibodies specific to antibodies of an animal, in which specific antibodies for zone 2 are obtained, - for example, goat secondary antibodies to rabbit, mouse immunoglobulins, but not limited to such.
  • Exactly nitrocellulose is used in this zone, since only such a material makes it possible to preserve the functional activity of the proteins deposited on it while simultaneously blocking nonspecific binding with the preservation of transport function with the fluid flow.
  • the binding of antibodies on nitrocellulose membrane from zone 3 is higher than for a standard protein, for example, BCA (200 ⁇ g/cm 2 against 120 ⁇ g/cm 2 ).
  • the stained chromatophore-antibody-viral particle complex will linger in 3.1 zone during the test, and the stained chromatophore-antibody complex not having bound the virus - in 3.2 zone (see Fig. 1 B, zone 3).
  • the stained complex immobilized on secondary antibodies of 3.2 zone serves as a control for the correct performance of the test (see Fig. 1B, 3.2 zone).
  • 3.2 zone - of internal control the chromatophore particles are held in place by the binding of secondary antibodies with primary antibodies. This demonstrates the integrity of the conjugate of the chromatophore with specific antibodies.
  • the fourth functional zone or the capillary pump zone, consists of the same material as zone 1, for example, of filter paper, and provides fluid flow and maximum transfer of molecules from the first functional zone to the third – to the precipitation zone, including the formed viral particle-stained specific antibody complexes.
  • the test strip may additionally contain a coating that isolates the conjugation, precipitation, capillary pump zones from the external environment. In one embodiment, such a coating also isolates a part of the sample application zone.
  • a test strip can be used without additional elements (case, etc.) for diagnosing SARS-COV-2.
  • a positive test result is the presence of coloration in both areas in the third zone of the test strip - in the precipitation zone.
  • the presence of coloration only in the zone of secondary antibodies (zone 3.2) indicates the absence of viral particles in an amount sufficient for detection.
  • test based on immunoprecipitation on a test strip is of high quality, therefore it is not sensitive to an excess of the tested antigen. Any amount of antigen above the detection threshold will stain 3.1 zone, and conjugate, whether bound with the virus or not, will stain 3.2 zone.
  • a composition containing a complex of antibodies with chromatophore particles is applied to the conjugation zone, as well as a composition containing specific antibodies in an effective amount - to the first region of the precipitation zone (3.1), a composition containing secondary antibodies to specific antibodies - to the second region of the precipitation zone (3.2).
  • drying is carried out, preferably freeze-drying.
  • a stabilizing buffer containing any of the sugars - to protect it from aggregation by adding sugars, for example, mannitol, trehalose or sucrose.
  • a plate is made which is formed of zones with applied reagents, additionally covered with an isolating material partially or completely, as described above, and then cut into test strips.
  • An antibody contained in the test strip and diagnosticum was also proposed to detect SARS-COV-2. It is an active agent of the test strip for diagnostics of SARS-COV-2 presence. Such antibody binds to a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
  • the antibody binds to SARS-COV-2 coronavirus protein with an affinity of at least 1 ⁇ 10 8 l/mol, measured as an Association constant (Ka), as determined by the Scatchard analysis.
  • This antibody is obtained as a result of the introduction to the animal of the developed fusion protein or genetic construct according to the invention (see below) - immunization. It can be a rabbit antibody, but is not limited to it.
  • a composition containing such an antibody in an effective amount for use in diagnostics of SARS-COV-2 presence is also proposed.
  • Such a composition is used in the manufacture of a test strip and diagnosticum - it is applied on the appropriate areas to form the functional zones of the test strip.
  • Such a composition is obtained by introducing the developed fusion protein or genetic construct (see below) to an animal, taking blood, isolating specific antibodies from it and mixing with the target additive.
  • a fusion protein and a genetic construct including a polynucleotide encoding the specified fusion protein and other elements that provide synthesis of this fusion protein in the producing organism, for use in the diagnostics of coronavirus infection are also proposed.
  • a fusion protein for use in the diagnostics of infection caused by SARS-COV-2 comprises fragments of M, S, N, E proteins of such coronavirus connected by flexible bridges, and is set forth as SEQ ID NO:1 or SEQ ID NO:2 amino acid sequence.
  • the antibody of the invention binds to such fusion protein and to SARS-COV-2. Binding occurs with a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
  • genetic construct primarily a linear DNA fragment or a recombinant vector is meant, which can be represented by a viral or plasmid vector.
  • the recombinant vector must comprise elements essential for the organisms of its maintenance and use, together with the corresponding regulatory sequences.
  • Regulatory sequences are nucleotide sequences which can affect gene expression at the level of transcription and/or translation, as well as mechanisms that ensure the existence and maintenance of the recombinant vector functioning.
  • An origin of replication for maintaining in a cell with medium and preferably high copy number, and a marker gene for a producer strain selection are essential to the prokaryotic system.
  • Bacterial elements of a plasmid DNA should not adversely affect expression in mammalian cells and cause a side effect of using the plasmid DNA.
  • a suitable origin of replication is represented by pM1 (der.), ColE1 (der.), and F1, pUC, and F1, but is not limited to such.
  • a suitable marker gene is represented by a reporter gene or antibiotic resistance gene, for example, ampicillin, mainly kanamycin, but is not limited to such.
  • Elements for efficient functioning, for expression of the encoded gene, - a promoter, including transcription initiation signals, mRNA leader sequence, a termination sequence, regulatory sequences, - are essential elements of a recombinant vector for use in mammals.
  • a promoter is an important component of a vector that triggers the expression of a gene of interest.
  • Human CMV / immediate early or CMV-chicken- ⁇ actin (CAGG) promoter are classic promoters for recombinant vectors - drug components.
  • CMV promoters are used for most DNA vaccines, as they mediate high levels of constitutive expression in a wide range of mammalian tissues [Manthorpe M, Cornefert-Jensen F, Hartikka J, et al. Gene therapy by intramuscular injection of plasmid DNA: studies on firefly luciferase gene expression in mice. Hum. Gene Ther. 1993; 4 (4): 419–431] and do not inhibit downstream expression.
  • CMV promoter is changed, for example, by incorporating HTLV-1R-U5 downstream the cytomegalovirus promoter or when using the chimeric SV40-CMV promoter [Williams JA, Carnes AE, Hodgson CP. Plasmid DNA vaccine vector design: impact on efficacy, safety and upstream production. Biotechnol. Adv. 2009; 27 (4): 353-370].
  • Tissue-specific host promoters which allow avoiding constitutive expression of antigens in inappropriate tissues are an alternative to CMV promoters [Cazeaux N, Bennasser Y, Vidal PL, Li Z, Paulin D, Bahraoui E.
  • the promoter can be with corresponding regulatory sequences from natural promoters with its own regulatory elements (CaM kinase II,CMV, nestin, L7, BDNF, NF, MBP, NSE, p-globin, GFAP, GAP43, tyrosine hydroxylase, subunit 1 of the kainate receptor, and subunit B of glutamate receptor, and others), or from synthetic promoters with regulatory sequences to obtain the desired expression rate (ratio of duration and expression level) of a target gene at the transcription level.
  • natural promoters with its own regulatory elements CaM kinase II,CMV, nestin, L7, BDNF, NF, MBP, NSE, p-globin, GFAP, GAP43, tyrosine hydroxylase, subunit 1 of the kainate receptor, and subunit B of glutamate receptor, and others
  • synthetic promoters with regulatory sequences to obtain the desired expression rate (ratio of duration and expression level) of a target gene at the
  • Regulatory sequences are nucleotide sequences that may affect gene expression at the level of transcription and/or translation, as well as mechanisms that ensure the existence and maintenance of the genetic construct functioning.
  • the recombinant vector, the plasmid or viral DNA of the present invention contains at least one of the abovementioned regulatory sequences, depending on the DNA variant, based on the selection of promoter and the desired expression parameters of the target gene. Based on the existing level of technology and known and obvious variants of such elements and their use, the recombinant vector according to the present invention may contain any combinations meeting the above-mentioned criteria, using which synthesis of the developed fusion gene is performed from it, in cells of a target organism – a human or an animal. When using a silencer or an insulator in the construct, it is possible to regulate the expression of the target gene.
  • the recombinant vector of the present invention in one embodiment additionally comprises such a regulatory element.
  • the recombinant vector of the present invention also contains such an important element as mRNA leader sequence containing translation initiation signals, a start codon.
  • Translation initiation signals is Kozak sequence in eukaryotes [Kozak M. (1986) "Point mutations define a sequence flanking the AUG initiator codon that modulates translation by eukaryotic ribosomes", Cell 44, 283-292].
  • the recombinant vector also contains a site, mainly different sites, for cloning of the target gene, for the correct target gene orientation in the recombinant vector, and a site, mainly sites, for primers annealing for its sequencing.
  • the recombinant vector also contains the polynucleotide encoding the fusion protein of the invention.
  • the amino acid sequence of a protein is known, one skilled in the art will be able to obtain the nucleotide sequence.
  • This can be a sequence either based on fragments of the native nucleotide sequence of viral proteins, or artificially optimized by codon composition. Codon optimization can be carried out independently, using information on the frequency of codons occurrence in a producer, for example, in a database [for example, Nakamura Y, Gojobori T, Ikemura T. Codon usage tabulated from international DNA sequence databases: status for the year 2000. Nucleic Acids Res . 2000 Jan 1; 28 (1): 292], or using specialized programs, for example, available at http://www.encorbio.com/protocols/Codon.htm or molbiol.ru or other resources.
  • a polynucleotide may not contain (e.g., SEQ ID NO.:5 or 6) or contain (e.g., SEQ ID NO.:7 or 8) a heterologous secretory sequence optimized in codon composition for the target organism - for example, such of TPA (tissue-type plasminogen activator), hGH (human growth hormone), IGF (insulin-like growth factor), EPO (erythropoietin), but not limited to such.
  • TPA tissue-type plasminogen activator
  • hGH human growth hormone
  • IGF insulin-like growth factor
  • EPO erythropoietin
  • the recombinant vector also contains a termination sequence containing sequentially a stop codon, a 3 ⁇ untranslated region with a polyadenylation signal and site, a stop codon; due to which mRNA stability is maintained, and transcription is terminated appropriately, and mRNA is exported from the nucleus.
  • Gene expression can be influenced by changing the termination sequence, which is necessary for mRNA stability maintaining, for proper transcription termination and mRNA export from the nucleus, including by its shortening.
  • the bovine growth hormone transcriptional terminator sequence is used [Montgomery DL, Shiver JW, Leander KR, et al. Heterologous and homologous protection against influenza A by DNA vaccination: optimization of DNA vectors. DNA Cell Biol.
  • polyA Polyadenylation
  • pVAX1 plasmid Invitrogen, Carlsbad, Calif., the bovine growth hormone terminator region contains a homopurin region which is sensitive to nuclease.
  • the recombinant vector according to the present invention may contain any termination sequence meeting the above-mentioned criteria, using which synthesis of a target protein is performed in cells of a human or animal.
  • An example of a termination sequence for mammalian cells is that of bovine growth hormone (BGH).
  • a safe vector such as, i.e. a recombinant adeno-associated virus, but not limited to such.
  • a DNA fragment is meant containing a promoter, an mRNA leader sequence, the polynucleotide described above, a termination sequence, including 1 or 2 stop codons, regulatory sequences. Specification described above is applicable to the elements. Such elements are crucial, but other elements may also be contained. A fusion protein is synthesized from such a fragment in the cells of a target organism. The arrangement sequence of the described elements is clear to the average person skilled in the art.
  • the corresponding and additional elements may be contained.
  • An element for integrating the construct into the genome of the producer may also be contained - for example, 3 'AOX1 or 18S rRNA for yeast.
  • the selective marker may be represented, for example, by the gene of resistance to ampicillin or kanamycin, or tetracycline; yeast - for example, the gene LEU2 or TRP1, or URA3; fungi - for example, the gene of resistance to bialaphos or hygromycin or aureobasidin or bleomycin; plants - for example, the gene of resistance to kanamycin or bialaphos.
  • promoter can be represented, for example, by the promoter of the lactose operon, tryptophan operon; yeast - for example, promoter of the gene of acid phosphatase, alcohol dehydrogenase gene, the gene of glyceraldehyde-3-phosphate dehydrogenase, the gene of the galactose metabolism; fungi – for example, promoter of the gene of cellobiohydrolase, either ⁇ -amylase or glucoamylase, or glyceraldehyde-3-phosphate dehydrogenase, or the gene abp1; plants – for example, CaMV 19S RNA promoter or the CaMV 35S RNA promoter or a gene nepalisite promoter.
  • NOS T nopalin synthase gene
  • a signal peptide suitable for the used producer organism is placed at the N-end of a polynucleotide encoding the target gene.
  • Examples of such secretory sequences are described in the literature [for example, for E. coli in the patent of Russian Federation No2198179, priority date 15.09.1999 for yeast - in the patent of Russian Federation No2143495, priority date 08.07.1994, U.S. patent No.
  • Plant Sci 122 101-108, Stiefel, V., Ruiz-Avila, L., Raz, R., Valles, M.P., Ghez, J., Pages, M., Martinez-lzquierdo, J.A., Ludevid, M.D., Langdale, J.A., Nelson, ⁇ ., and Puigdoménech, P. (1990). Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation. Plant Cell 2, 785-793].
  • genetic construct according to the present invention may contain any combinations meeting the above-mentioned criteria, using which expression of the fusion gene is performed in producer organism.
  • E. coli cells are selected as a producer
  • the gene can be a part of a bacteriophage, for example, on the basis of phage ⁇ , or plasmids, for example, on the basis of the pBR or pUC, and the like.
  • Bacillus subtilis is used as a producer organism
  • the gene can be, for example, in a plasmid based on pUB.
  • yeast are used as a producer, a genetic structure can be represented, for example, by a plasmid-based YEp or YRp or YCp or YIp. etc.
  • a prokaryotic producer is represented, for example, by Escherichia coli, Bacillus subtilis, eukaryotic producer - fungi, cells of plants, mammals.
  • the named objects of the invention apart from express diagnosticum and test strips directly, can also be used for other types of diagnostics of infection caused by SARS-COV-2.
  • Zone 2 is colored entirely - it contains the antibody-chromatophore conjugate, in the final diagnosticum it will be hidden under the part of the strip packaging - the case.
  • the strip between zones 3 and 4 is the shadow at the border of the zones, in commercial kits this place is usually hidden.
  • Example 1 Obtaining antibodies specific to coronavirus
  • fusion protein comprising fragments of M, S, N, E proteins of coronavirus connected by flexible bridges for the full functioning of each domain. It is shown that when using flexible bridges slightly different in length, which is reflected in the amino acid sequence SEQ ID NO:1 or 2, the domains retained full functioning.
  • I-Tasser algorithm was used to model proteins.
  • the modelled fusion protein in one embodiment consists of 422 aa, with methionine at the N-terminus - 423 aa, is represented by the amino acid sequence SEQ ID NO:1.
  • SEQ ID NO:1 The amino acid sequence of this protein using the ProtParam program (http://au.expasy.org/tools/protparam.html) has shown that the fusion protein has a molecular mass of 46.4 kDa, pI 9.61, the protein is stable, the half-life in mammals is about 100 hours, in yeast is more than 20 hours, in E. coli is more than 10 hours.
  • methionine at the N-terminus - 46.5 kDa, pI 9.61 the protein is stable, the half-life in yeast and E.coli is as mentioned above, in mammals is about 30 hours.
  • a variant was also evaluated when for immunization of animals to obtain antibodies, a genetic construct was used for the synthesis of the developed fusion antigen in mammalian cells.
  • the protein construct was also evaluated with the addition of a heterologous signal sequence for secretion from protein-producing cells in the body.
  • the fusion protein When adding the secretory sequence of IGF (GKISSLPTQLFKCCFCDFLK), with methionine at the N-terminus, the fusion protein consists of 443 aa, has a molecular weight of 48.8 kDa, pI 9.55, the protein is stable.
  • the fusion protein When adding the hGH secretory sequence (ATGSRTSLLLAFGLLCLPWLQEGSA), with methionine at the N-terminus, the fusion protein consists of 448 aa, molecular mass is 49.1 kDa, pI 9.57, the protein is stable.
  • the fusion protein By adding the TPA secretory sequence (MDAMKRGLCCVLLLCGAVFVSPS), the fusion protein consists of 445 aa, molecular mass is 48.8 kDa, pI 9.53, the protein is stable.
  • the modelled fusion protein in one embodiment consists of 424 aa, with methionine at the N-terminus - 425 aa, is represented by SEQ ID NO:2 amino acid sequence.
  • SEQ ID NO:2 amino acid sequence is represented by SEQ ID NO:2 amino acid sequence.
  • Analysis of the amino acid sequence of this protein using the ProtParam program http://au.expasy.org/tools/protparam.html has shown that the fusion protein has a molecular mass of 46.5 kDa, pI 9.61, the protein is stable, the half-life in mammals is about 100 hours, in yeast is more than 20 hours, in E. coli is more than 10 hours.
  • methionine at the N-terminus – 46,6 kDa, pI 9,61 the protein is stable, the half-life in yeast and E.coli is as mentioned above, in mammals is about 30 hours.
  • the fusion protein When adding the secretory sequence of IGF, with methionine at the N-terminus, the fusion protein consists of 445 aa, molecular mass is 48.9 kDa, pI 9.55, the protein is stable.
  • the fusion protein When adding the secretion sequence of hGH, with methionine at the N-terminus, the fusion protein consists of 450 aa, molecular mass is 49.2 kDa, pI 9.57, the protein is stable.
  • the fusion protein When adding the secretory sequence of TPA, the fusion protein consists of 447 aa, has a molecular mass of 48.9 kDa, pI 9.53, the protein is stable.
  • the indicators change.
  • a protein When a fusion polynucleotide is expressed in any cell, a protein is synthesized with methionine at the N-terminus, since translation always starts from the start codon. Further, methionine can be cleaved naturally, for example, if the protein is secreted, as part of the secretory peptide. Or, when purifying the protein obtained in bacterial cells, methionine can be cleaved, for example, by aminopeptidase.
  • the amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, while performing codon optimization for expression in E. coli cells using the molbiol.ru service and adding restriction sites flanking the gene. Sequences were received characterized by SEQ ID NO:3 or 4. The calculated genes were synthesized chemically.
  • E. coli cells of the BL21 Star (DE3) strain (Invitrogen, USA), with the F-ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) genotype, containing ⁇ De3 lysogen in the genome and the rne131 mutation were used for creating a producer strain.
  • the mutated rne (rne131) gene encodes a truncated form of RNase E, which decreases intracellular destruction of mRNA, leading to an increase in its enzymatic stability. lon- and ompT-mutations in protease genes make it possible to obtain non-proteolyzed recombinant proteins in large amounts.
  • Cells of E. coli BL21 strain with F-ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) genotype were prepared as follows. The cells were incubated at +37°C for 16 h in 5 ml of L-broth containing 1% tryptone, 1% yeast extract and 1% sodium chloride. The culture was diluted with fresh L-broth 50-100 times and grown on a shaker at +37°C to an optical density of 0.2-0.3 at a wavelength of 590 nm. Upon reaching an optical density of more than 0.3, the culture was diluted with fresh L-broth to an optical density of 0.1 and grown for 30 min.
  • the transformation of competent cells was performed by electroporation. To do this, 1 ml of tenfold dilute ligase mixture was added to 12 ml of competent cells, mixed and electroporation was performed on an Eporator electroporator (Eppendorf, Germany) in sterile electroporation cuvettes (Eppendorf, Germany) of 100 ml volume, 1 mm gap, with an electric pulse of 1.7 kV intensity lasting 5 msec.
  • Eporator electroporator Eppendorf, Germany
  • sterile electroporation cuvettes Eppendorf, Germany
  • the cells were incubated in a SOC medium (2% bacto-trypton, 0.5% yeast extract, 10 mm NaCl, 2.5 mm KCl, 10 mm MgCl 2 , 10 mm MgSO 4 , 20 mm glucose) for 40 minutes at +37°C. 10-100 ⁇ l of cell suspension was sown on a selective LB medium (Gibko BRL, USA) containing ampicillin (50 ⁇ g/ml) to select clones containing plasmids (producer strains).
  • SOC medium 2% bacto-trypton, 0.5% yeast extract, 10 mm NaCl, 2.5 mm KCl, 10 mm MgCl 2 , 10 mm MgSO 4 , 20 mm glucose
  • Standard agarized LB medium containing ampicillin at a concentration of 100 ⁇ g/ml and glucose at a concentration of 1% was used for cultivation of the resulting producer strains to block non-specific expression.
  • the PYP-5052 medium consisting of 1% peptone (Gibco, USA), 0.5% yeast extract (Gibco, USA), 50 m ⁇ Na 2 HPO 4 , 50 m ⁇ K 2 HPO 4 , 25 m ⁇ (NH 4 ) 2 SO 4 , 2 m ⁇ MgSO 4 , 0.5% glycerol, 0.05% glucose and 0.2% lactose was used for autoinduction of expression by the Studier method (Studier, 2005).
  • a single colony of the producer strain was inoculated in the PYP-5052 medium containing ampicillin at a concentration of 50 ⁇ g/ml. Fermentation was carried out at +37°C in a temperature-controlled rotary shaker at 250 rpm. within 20 hours until there is no significant change in the OD 600 for 1 hour. An aliquot of cells was taken for analysis of the expression of the gene encoding the fusion protein, by PAGE, and the remaining biomass was precipitated by centrifugation at 9000g.
  • the precipitated cells were lysed using 3 sonication cycles of 30 sec with a break of 2 min on ice. Then, the destruction of inclusion bodies was carried out by incubation for an hour with a lysing buffer containing 500 mM sodium phosphate buffer, pH 8.0, 6M guanidine hydrochloride, 500 mM sodium chloride. 8 ml of the lysing buffer were added to cells collected by centrifugation from 50 ml of culture.
  • a column containing Ni-NTA Sepharose was pre-equilibrated with application buffer (500 mM sodium phosphate buffer, pH 8.0, 8 M urea, 500 mM sodium chloride, 10 mM imidazole). The destroyed inclusion bodies were applied on the column. The column was then washed with two volumes of the application buffer. The column was then washed with three volumes of wash buffer (500 mM sodium phosphate buffer, pH 8.0, 8 M urea, 500 mM sodium chloride, 30 mM imidazole). The protein was eluted with 5 ml of elution buffer (500 mM sodium phosphate buffer, pH 8.0, 8M urea, 500 mM sodium chloride, 200 mM imidazole). Fractions of 1 ml were collected, analyzed in 12% SDS-PAGE, fractions with the target protein were combined, the protein concentration in them was determined with the Bradford method.
  • application buffer 500 mM sodium phosphate buffer, pH 8.0, 8 M
  • Protein preparations (SEQ ID NO:1, 2) were obtained with a purity of about 97-98%, according to SDS-PAGE, the concentration of the fusion protein in each preparation was 1-2 mg / ml.
  • Fusion proteins were also obtained using E. coli RosettaPLys strains, as well as Bacillus subtilus strains and other vectors.
  • the amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, simultaneously codon optimization for expression in Pichia pastoris yeast cells was carried out using http://molbiol.ru/scripts/01_19.html program and adding regions flanking the gene to obtain the secreted protein, according to the manual for cloning vector.
  • the calculated genes were synthesized chemically.
  • the resulting genes were cloned in pHIL-S1 eukaryotic expression vector, according to the vector manual.
  • Yeast cells were prepared for transformation. Cultivation and freezing of Pichia pastoris cells of SMD1163 strain, defective in several yeast proteases, which ensures the stability of the secreted protein, were carried out. The cells were seeded in sterile conditions on agar in YPD medium (1% yeast extract, 2% peptone, 2% glucose, 1 mM dithiothreitol), cultured at 30° C, then subcultured into suspension and cultured for 16 h. Some of the cells were resuspended in YPD medium with 15% glycerol addition and frozen at -86° C. To obtain competent cells, cell colonies were preliminarily grown on an agar plate in YPD medium at 30° C for two days.
  • YPD medium 1% yeast extract, 2% peptone, 2% glucose, 1 mM dithiothreitol
  • the contents of one colony were grown in 10 ml of YPD medium at 30° ⁇ for 16 h.
  • the suspension was diluted in YPD to an OD 600 0.2 and to final volume of 10 ml and the culture was grown to an OD 600 0-8 for 4 hours.
  • the cell suspension was centrifuged for 5 min at 500 g, the supernatant was poured, the precipitate was resuspended in 10 ml of solution I from the EasyComp Transformation Kit, centrifugation was performed again, and the precipitate was resuspended in solution I.
  • Aliquots of competent cells of 50-200 ⁇ l were poured into 1.5 ml sterile tubes, which then were stored at a temperature of -90° C before use.
  • the EasyComp Transformation Kit included in the Pichia Easy Select Kit (Invitrogen) was used for transformation; the reaction was carried out according to the manual for the kit.
  • the resulting cell suspension was plated into a sterile plate on an agar gel prepared in YPD medium supplemented with 1 M sorbitol and ampicillin antibiotic at a final concentration of 100 ⁇ g/ml. After 3 days, several dozen colonies were obtained per plate. The cells from the grown colonies were transferred onto a plate with MMD (minimal medium dextrose) agar and the plate was cultured for 2 days at 30°C.
  • MMD minimum medium dextrose
  • the cells of the colonies grown on the selective medium were transferred into flasks and cultured in 5 ml of MGY medium on a shaker (250 rpm) for 1 day until OD 600 5. After that, the cells were pelleted by centrifugation at 3000 g for 10 min. Control of target gene expression was performed by SDS-PAGE.
  • the culture medium was filtered (pore diameter 45 ⁇ m), then Tris-HCl pH 6.0 was added to a final concentration of 20 mM.
  • the culture medium containing the fusion protein was 5-10 fold concentrated using Millipore concentrators for proteins with a molecular weight of more than 10 kDa.
  • CM-Sepharose Ion exchange chromatography was carried out on CM-Sepharose.
  • the column with CM-Sepharose was equilibrated with a buffer containing 20 mM Tris-HCl pH 6.0.
  • the fusion protein preparation was applied at a rate of 60 ml/hour.
  • the column was washed with 20 mM Tris-HCl pH 6.0; 20 mM Tris-HCl pH 6.0, 200 mM NaCl. Elution was performed with 20 mM Tris-HCl pH 6.0, 1 M NaCl, and fractions of 1 ml were collected.
  • the preparation of the obtained fusion protein was 2-fold diluted, phosphate pH 8.0 was added to a concentration of 50 mM and applied to the column. After washing the column with application buffer, ballast proteins were removed by washing with 20 mM imidazole solution in the same buffer. The protein was eluted with a solution containing 200 mM imidazole.
  • Fusion proteins were also obtained using other fungi and other vectors.
  • a nucleotide sequence of a gene collinear to the amino acid sequence of the fusion protein encoded by it was calculated, set forth as SEQ ID NO:1 or 2, with the target gene flanking by restriction sites, as well as with the addition of the Kozak sequence before the start codon to initiate translation, and after the start codon – a signal sequence, for example, of TPA (tissue-type plasminogen activator isoform 1 preproprotein [Homo sapiens], NCBI Reference Sequence: NP_000921.1), hGH, IGF, EPO, or represented by aa MLLLLLLLLALALA, for secretion of the synthesized protein from an eukaryotic cell, with simultaneous optimization by codon composition for expression in human cells, the tool on the site molbiol.ru was used. For example, sequences set forth as SEQ ID NO:5,6 and set forth as SEQ ID NO:8, respectively were obtained.
  • the corresponding nucleotide sequences of the new coronavirus were taken to obtain a genetic construct, since these sequences are expressed in mammals, the remaining fragments were optimized as described above.
  • the nucleotide sequence set forth as SEQ ID NO:7 was obtained.
  • the calculated nucleotide sequences were synthesized by a chemical method using ASM-800 DNA synthesizer (BIOSSET, Russia).
  • the synthesized gene was cloned in the pcDNA3.1 (+) vector according to the vector manual.
  • a producer strain of this plasmid DNA was created, according to the Protocol described in 1.4.1.1 paragraph.
  • the transfection of mammalian cells with the created plasmids was performed by the method of calcium phosphate precipitation.
  • CHO mammalian cells
  • the cells were seeded in 12-well plates (Costar, USA) with a seeding density of 5 ⁇ 10 4 cells/cm 2 .
  • the culture medium was changed to synchronize cell division.
  • calcium phosphate-precipitated plasmid DNA was added to the cells.
  • 250 ⁇ l of the solution containing 50 ⁇ g of DNA in 250 mM CaCl 2 were slowly mixed with 250 ⁇ l of a solution (1.64% NaCl, 1.13% HEPES pH 7.12, and 0.04% Na 2 HPO 4 ).
  • the medium was replaced with a similar medium containing 100 ⁇ g/ml of neomycin to select clones containing plasmids with an insert of the target gene and, therefore, expressing fusion proteins
  • the selection was carried out for 20 days, in wells containing live cells, the medium was changed (the previous culture medium was not poured out, but was used to determine the amount of secreted proteins by ELISA), and after another day the cells were removed from the substrate and analyzed for expression of the transformed genes.
  • the analysis of the efficiency of transfection was carried out on an EPICS XL Beckman Coulter flow cytometer (Beckman Coulter, USA).
  • the level of fusion proteins in the culture medium of the obtained stable CHO line transfectoms was evaluated using a standard solid-phase ELISA.
  • the cultivation of producer cells was carried out using BIOSTAT® Bplus bioreactor and an autoclaved IMDM medium supplemented with 45 g of DFBS (0.5%) and 25.8 g (100 mM) of zinc heptahydrate (ZnSO 4 x 7H 2 O) per 9 L of medium.
  • the working mode was set up as: temperature 37°C, pH 6.9-7.2, oxygen concentration 50% of air saturation.
  • the bioreactor was inoculated, for which the inoculum was introduced into it under aseptic conditions.
  • the cultivation time was 3 days.
  • the culture fluid was filtered through a sterile Sartopure capsule (Sartorius, Germany), with a pore diameter of 1.2 ⁇ m, at a rate of 1 L/min. Then the clarified liquid was concentrated on Viva Flow 200 system (Sartorius, Germany) using a filter. Concentration was carried out until a total volume of 200 ml was reached.
  • Chromatographic purification was carried out in two stages using sterile solutions.
  • BioLogic DuoFlow Pathfinder Bio-Rad
  • BioFract fraction collector an automatic BioFract fraction collector and YMC TriArt semi-preparative chromatographic column, 250x4.6 mm, C18 sorbent were used.
  • the column was equilibrated using 200 ml of buffer (1 kg of water for injection and 1 g of trifluoroacetic acid) in manual mode through a chromatograph pump at a rate of 2 ml/min.
  • the prepared material in a volume of 200 ml was introduced into the chromatograph through the chromatograph pump at a rate of 0.5 ml/min. Elution was performed with a buffer (2 kg of acetonitrile, 2 g of trifluoroacetic acid) at a rate of 0.5 ml per minute. The fraction was collected at the maximum absorption at 260 nm. The volume of the fraction was approximately 500 ml.
  • the second stage of purification was carried out using BioSil SEC 125-5 gel-chromatographic column, 300x7.8 mm.
  • the column was pre-equilibrated with 0.02 M PBS buffer.
  • the resulting material was introduced into the chromatograph through the chromatograph pump at a rate of 0.5 ml/min. Elution was performed with a buffer (0.6 M NaCl solution) with a concentration gradient from 0.1 to 0.6 M.
  • a fraction was collected with an absorption of at least 3.4 optical units at A280 nm.
  • the fraction was collected in vials.
  • the volume of the resulting solution for each protein preparation was approximately 1 L with the fusion protein concentration of 2-2.7 mg per ml.
  • fusion proteins according to the invention can also be obtained using other mammalian cells, for example HEK293, COS, and other plasmids, for example, pVAX, but not limited to such.
  • HEK cells use to produce the developed fusion protein.
  • HEK293 cells were cultured at 37C in a CO 2 incubator (5% CO 2 , 100% humidity) in a DMEM medium containing 10% embryonic veal serum, without antibiotics, with L-glutamine. The transfection was performed at 70% confluence of the monolayer. 2 micrograms of plasmid DNA were used in the volume of 5 ml of culture medium, the medium was replaced with a fresh one 24 hours after transfection, and cells were cultured for 5 days.
  • the amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, simultaneously the codon optimization for expression in Nicotiana benthamiana cells was carried out using http://molbiol.ru/scripts/01_19.html program and adding regions flanking the gene according to the manual of vector for cloning.
  • the calculated genes were synthesized chemically and cloned into the pTRV1 eukaryotic expression vector. It is also possible to use a viral vector (for example, described in the article of Komarov T.V., Skulachev M.V., Zverev A.S., Schwartz AM, Dorokhov Yu.L., Atabekov I.G. New viral vector for efficient production of target proteins in plants. Biochemistry, 2006, 71 (8), 1043-1049).
  • the resulting vector was introduced into the Agrobaterium tumefaciens GV3101 strain, which was used for infiltration of N. benthamiana leaves.
  • the resulting Agrobaterium tumefaciens strain carrying the fusion gene was cultured for 12 h at 30°C in a shaker. Cells (1.5 ml) were pelleted by centrifugation (4000g, 5 min), the pellet was resuspended in buffer (1.5 ml: 10 mM MgCl 2 , 10 mM MES (pH 5.5)), OD 600 was adjusted to 0.2. The suspension of agrobacteria was applied with a needle-free syringe to the leaves of growing plants of N. benthamiana. The maximum level of protein synthesis was observed on 7-11 days after infiltration.
  • fusion proteins in leaf cells of producing plants was analyzed using SDS-PAGE.
  • a leaf fragment was triturated in buffer (10 mM KCl, 50 mM Tris pH 8.0, 5 mM MgCl 2 , 10 mM ⁇ -mercaptotanol, 0.4 M sucrose, 10% glycerol) on day 10 after infection.
  • the obtained extract was subjected to centrifugation (14000g, 10 min), the pellet and supernatant were analyzed using SDS-PAGE. Proteins were revealed on electrophoretogram, in molecular weight corresponding to the fusion proteins according to the invention, in the membrane fraction of cells. In control plants that did not undergo transformation, the corresponding proteins were not identified.
  • the protein yield was about 12-14% of the fraction of insoluble proteins.
  • the claimed fusion protein can be obtained using both prokaryotic and eukaryotic cell systems, a highly purified preparation of each protein can be obtained using various types of protein purification. These conditions for isolation and purification were selected experimentally and may vary in values known to the average specialist in this field.
  • the synthesized genes were cloned in pVAX1 (Invitrogen), pcDNA3.1+ (Invitrogen) eukaryotic expression vectors at restriction sites flanking the target genes, according to the vector manual.
  • a pcDNA3.1+ vector, incapable of expressing neomycin, was also obtained by exposing this vector to NsiI restriction enzyme in the SV40 promoter region (-71 bp).
  • the mixture was heated at +95°C for 10 min and purified from salts by dialysis on nitrocellulose filters with a pore diameter of 0.025 ⁇ m (Millipore, USA). Dialysis was performed against a solution containing 0.5 mM EDTA in 10% glycerol for 10 minutes.
  • E. coli cells of DH10B/R strain F-mcrA, ⁇ (mrr-hsdRMS-mcrBC), ⁇ 80dlacZ ⁇ M 15, ⁇ lacX74, deoR, recA1, endA1, araD139, ⁇ (ara, leu) 769, galU, galK ⁇ -, rpsL, nupG
  • This strain does not contain methylase, which allows to minimize the possibility of mutations occurrence in the DNA, including the gene cloned in the plasmid maintained in this strain.
  • 1 ⁇ l of dialyzed ligase mixture was added to 12 ⁇ l of competent cells, placed between the electrodes of an electroporation cuvette and processed by a current pulse.
  • the cells were placed in 1 ml of SOC broth (2% bacto-tryptone, 0.5% yeast extract, 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl 2 , 10 mM MgSO 4 , 20 mM glucose) and incubated for 40 min at + 37°C.
  • SOC broth 2% bacto-tryptone, 0.5% yeast extract, 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl 2 , 10 mM MgSO 4 , 20 mM glucose
  • Clones of E. coli cells containing the obtained plasmid DNA were detected on a selective medium containing LB agar, 50 ⁇ g/ml of kanamycin, or ampicillin, based on the resistance gene of a vector.
  • Plasmid DNA was isolated from the grown clones. Plasmid DNA was isolated using the Wizard Minipreps DNA Purification System kit (Promega, USA). Purified recombinant plasmid DNA was checked by sequencing.
  • a PCR reaction was performed, then the reaction mixture was purified from free labeled ddNTP according to the manual for the BigDye X-Terminator Purification Kit (Applied Biosystems, USA) and the products of the sequencing reaction were separated using an Applied Biosystems 3500 / 3500xL Genetic Analyzer capillary sequencer (Applied Biosystems, USA) and 3500/3500xL Genetic Analyzer Polymer “POP-6 TM” reagent (Applied Biosystems, USA).
  • E. coli cell clones were selected containing the full-length sequences of the target genes in the plasmids - DNA sequences encoding the developed fusion proteins. Such clones were used as the producer strain of the plasmids according to the present invention. In one embodiment, this is Escherichia coli DH10B/R bacterial strain, containing the pcDNA3.1(+) vector, which contains the nucleotide sequence of SEQ ID NO:5-8.
  • the values determined in the experiment corresponded to the values of the ratios A 260 /A 280 and A 260 /A 230 for pure preparations, for all obtained preparations of plasmid DNA.
  • Protein impurities in the resulting plasmid DNA preparations were also quantified using the microBCA assay [Smith, P.K., et all, Measurement of protein using bicinchoninic acid. Analyt. Biochem. 150, 76-85 (1985)], measuring the optical density of the resulting colored protein complexes with copper and bicinchoninic acid with a wavelength of 562 nm.
  • the sensitivity of the microBCA assay method is 0.5-20 ⁇ g/ml of protein. The concentration of total protein in none of the studied plasmid DNA preparations exceeded the norm.
  • the content of bacterial lipopolysaccharide in plasmid DNA preparations was also determined using a gel-thrombus version of the LAL test with a sensitivity of >0.25 EU/ml (ToxinSensor, GenScript, USA). Limulus polyphemus horseshoe crab amebocytes lysate was used as the LAL reagent.
  • the LAL reagent specifically reacts with bacterial endotoxins; as a result of the enzymatic reaction, the reaction mixture changes in proportion to the concentration of endotoxin.
  • the results were evaluated by the presence or absence of a dense clot at the bottom of the tube by inverting the tube.
  • a gel clot did not form when examining a sample diluted 10 times, for all obtained plasmid DNA preparations, i.e. when the sensitivity of the method is 2.5 EU/ml, which, given the concentration of plasmid DNA in the sample, indicates an acceptable rate of endotoxin removal.
  • the yield of plasmid DNA ranged from 3.1 mg to 4.7 mg per liter of culture medium. The process took about 4 days.
  • the synthesized genes were cloned into a vector based on the pAAVK-EF1 ⁇ -MCS (System Biosciences (SBI)) adeno-associated virus, on the basis of which a producer strain of this vector was created using E. coli cells (RecA-). Bacillus subtilis bacteria cells were also successfully used as producer.
  • SBI System Biosciences
  • a vector was isolated for use in mammals, all according to the vector manual.
  • the yield of the vector ranged from 2 mg to 3.2 mg per liter of culture medium.
  • the plasmid DNA obtained according to 2.1.2., or the viral vector of item 2.2., or a fragment amplified from them was used.
  • the DNA fragment was amplified containing a promoter, an mRNA leader sequence, and also regulatory sequences for these elements, a polynucleotide - a fusion gene, a termination sequence.
  • the solution may contain also other elements, and the elements indicated in the previous sentence are the key ones.
  • Amplification of this sequence was carried out in a volume of 50 ⁇ l, in 650 ⁇ l thin-walled polypropylene tubes containing 5 ⁇ l of 10x Taq buffer (700 mM Tris-HCl, pH 8.6/25oC, 166 mM (NH 4 ) 2 SO 4 ), 5 ⁇ l of MgCl 2 (1.25 mM), 1 ⁇ l of dNTP, 31.5 ⁇ l of water, 1 ⁇ l of forward and 1 ⁇ l of reverse primers, 5 ⁇ l of plasmid DNA and 0.5 ⁇ l Taq polymerase (Fermentas, Lithuania).
  • 10x Taq buffer 700 mM Tris-HCl, pH 8.6/25oC, 166 mM (NH 4 ) 2 SO 4
  • 1 ⁇ l of dNTP 31.5 ⁇ l of water
  • 1 ⁇ l of forward and 1 ⁇ l of reverse primers 5 ⁇
  • the reaction mixture was warmed for 5 minutes at 95°C for DNA denaturation.
  • 30 ⁇ l of Bayol F mineral oil (Sigma, USA) were layered onto a reaction mixture of 50 ⁇ l volume.
  • the amplification reaction was carried out in a C1000 Thermal Cycler (Bio-Rad, USA) thermal cycler. 35 cycles were carried out: 95° ⁇ - 20 sec, 50-62° ⁇ (depending on the primers) - 20 sec, 72° ⁇ - 1 min.
  • an additional cycle was carried out: 5 min at 72°C.
  • Amplified DNA fragments were concentrated and purified using preparative electrophoresis in 0.8-1.2% agarose gel (Gibko BRL, USA).
  • a sample of the mixture after PCR was mixed with 6x buffer (0.25% bromophenol blue, 30% glycerin) (ThermoScientific, USA) and loaded into the gel wells, 18 ⁇ l per well.
  • Electrophoresis was carried out in a horizontal apparatus in TAE buffer (40 mM Tris-acetate, 2 mM EDTA pH 8.0, 0.5 ⁇ g/ml ethidium bromide) at a voltage of 5-10 V/cm.
  • the result of DNA separation was recorded in transmitted UV light (302 nm) of the Macrovue transilluminator (LKB, Sweden).
  • the length of the amplified fragment was determined by the logarithmic dependence of DNA mobility on the length of the fragments in the marker.
  • markers a proprietary mixture of DNA fragments “GeneRuler 1000 bp DNA Ladder” (Fermentas, Lithuania) was used.
  • a plot of agarose containing DNA strip of the required size was excised and the DNA fragment was purified using the DNA & Gel Band Purification Kit (GE Healthcare, UK) according to the manual.
  • polynucleotide according to the invention is expressed from such constructs in mammalian cells.
  • the isolated genetic construct was used in mammals.
  • mice of inbred lines (“Rappolovo” Laboratory animal kennels). Animals weighing 19-22 g were kept under standard conditions, at an ambient temperature of +27 ⁇ 2°C with 55% constant humidity, with a 12-hour daylight. They received dry standardized food and water without restriction.
  • mice were injected intramuscularly with pcDNA3.1(+)seqidno7 plasmid DNA in the amount of 50 ⁇ g in PBS, animals not injected with any substance were used as a negative control. Animals were sacrificed on days 2, 5, and 7, blood was taken to prepare the serum. Some animals of all groups were not withdrawn from the experiment to assess the safety of the agent.
  • the obtained serums were analyzed by PAGE followed by transfer of proteins to the nitrocellulose membrane and visualization of the target protein using chemiluminescence.
  • a “sandwich” was assembled on a Semi-phor TE70 Semi-dry transfer unit apparatus for horizontal transfer: 6 Whatman papers fragments soaked in Solution I, 3 Whatman papers fragments soaked in Solution II, BioRad nitrocellulose membrane soaked in Solution II, PAGE after electrophoresis, which was located on the membrane and immobilized, 9 fragments of Whatman paper soaked in Solution III.
  • the lid of the device was closed, the power was connected, 100 V for an hour, Constant current PS unit model PS50, Hoefler Scentific Instruments (HSI) was the current source.
  • a fusion protein a specific antibody — a secondary antibody — horseradish peroxidase.
  • the membrane was treated with 1% dry skim milk in phosphate-buffered saline with the addition of 0.5% Tween-20 (125 ⁇ l of a 20% aqueous solution in 50 ml of milk), incubation was carried out for 15 minutes at room temperature. Then the mixture was poured, antibodies were added to the coronavirus proteins - Anti-SARS-CoV-2 spike glycoprotein monoclonal antibody (CABT-RM321) rabbit antibodies to S protein of the coronavirus in 1% skimmed milk at a dilution of 1: 3000, then incubated for 16 hours at +4°C, after which it was heated to room temperature.
  • Tween-20 125 ⁇ l of a 20% aqueous solution in 50 ml of milk
  • the formed membrane-immobilized complexes were developed using the Amersham ECL Western Blotting Detection Reagent (GE Healthcare) chemiluminescence kit. A mixture of equal volumes of 1 and 2 reagents from this kit was applied to a wet membrane with immobilized complexes of a fusion protein with specific antibody with a secondary antibody with horseradish peroxidase, all was packed between layers of a transparent plastic paper folder (slide). This construct was placed in an X-ray cassette (Kodak). Amersham Hyperfilm ECL X-ray film fragment was glued on top and fixed. The cassette was closed and kept for 12 hours. The film was developed using commercial solutions of developer and fixer (Krok-rentgen) according to the manual and dried. These actions were carried out in the dark in the light of a red lamp.
  • the ability of the developed genetic construct to express the encoded target gene after introduction into the muscles, as well as the functioning of the domains of the developed fusion protein, in particular, represented by the new coronavirus S and N proteins, were evaluated.
  • the synthesis of the fusion protein was demonstrated already on the second day after the introduction of the developed genetic construct carrying the gene encoding it, and within a week, with the maximum level of synthesis being detected on the 5th day after immunization. This suggests that the used genetic construct allows the expression of the target gene in mammalian cells.
  • Antigenicity and immunogenicity depend on the heterogeneity of the molecules: the more heterogeneous it is, the better it is recognized by the immune system; and also on the size of the molecule - the protein must be more than 10 kDa - and on the degree of foreignness. This may explain the effectiveness of the developed fusion protein.
  • the immunization of 3 rabbits at the age of 9 months was carried out with the obtained fusion protein in an amount of 200 ⁇ g, concentration 100 ⁇ g/ml, in a volume of 2 ml, with complete Freund's adjuvant, adjuvant - 1/10 of the volume of the solution for immunization.
  • immunization was carried out with the obtained genetic construct in an amount of 250 ⁇ g, a concentration of 123 ⁇ g/ml, in a volume of 2 ml. Immunization was carried out three times, with an interval of two weeks, subcutaneously in the thigh, blood sampling from the ear vein was carried out two weeks after the third immunization.
  • the titers of antibodies in the blood serum of the studied animals were measured.
  • the antibody titer of the sera of immunized animals was determined using enzyme-linked immunosorbent assay (ELISA).
  • ELISA enzyme-linked immunosorbent assay
  • the results were analyzed using Microsoft Excel.
  • the fusion protein obtained by any of the methods described in example 1 caused the formation of a high antibody titer.
  • any genetic construct described and obtained as described in Example 1 caused the formation of a high titer of antibodies.
  • antibody titers were higher. Similar results were obtained using other animals, including mice and a goat.
  • the Association constant (Ka) of obtained antibodies was also measured by ELISA according to Scatchard.
  • the minimum detected value was1 ⁇ 10 8 L/mol, and large values were also detected - for example, 5,5 ⁇ 10 8 , 6,8 ⁇ 10 9 , 7,2 ⁇ 10 9 , 8,5 ⁇ 10 9 L/mol.
  • a system for obtaining antibodies was subsequently chosen - rabbits were immunized with pcDNA3.1 (+) seqidno7 plasmid DNA due to the greater convenience and less labor intensity, as well as similar results on the induction of the antibody response.
  • the rabbit was boosted - 2 ml of vector with a concentration of 0.123 mg/ml was injected by electroporation or with a concentration of 1 mg/ml by the usual administration. Blood sampling was performed once a month. ⁇ 25 ml of blood was taken, from which ⁇ 15 ml of serum was obtained. A composition with antibodies was obtained from the obtained serum, then antibodies were isolated.
  • Antibodies were isolated from the serum in the following way.
  • the serums were thawed on ice.
  • 500 ⁇ l of PBS was added to 500 ⁇ l of serum, centrifuged at 3000g for 15 minutes at +4°C. 820 ⁇ l of saturated ammonium sulfate solution was added.
  • the solution was placed on a shaker for 30 minutes in ice, centrifuged at 1000g for 15 minutes at +4°C.
  • the precipitate was washed with 45% ammonium sulfate solution and again centrifuged at 1000g for 15 minutes at + 4°C.
  • the precipitate was dissolved in 1 ml of PBS and centrifuged at 5000 g for 15 minutes at + 4°C. 670 ⁇ l of saturated ammonium sulfate solution was added.
  • the solution was placed on a shaker for 30 minutes in ice, centrifuged at 1000g for 15 minutes at + 4°C.
  • the precipitate was dissolved in 500 ⁇ l of PBS and dialyzed for 16 h against ⁇ 5 l of PBS at + 4° ⁇ .
  • the solution was centrifuged at 5000g for 15 minutes at + 4°C.
  • the supernatant, a purified solution of antibodies, was placed in a new test tube, and a sample was taken for analysis with PAGE. The main part was frozen.
  • the fusion protein of the invention can be used in other diagnostic procedures to detect SARS-COV-2. For example, using immunoblot or ELISA to detect antibodies and virus, respectively, but not limited to them.
  • a test strip was prepared by placing on a strip of hydrophobic material from one edge to another the materials of functional zones - hydrophilic material, hydrophilic material antibody binding value of which is less than 30 ⁇ g/cm 2 , nitrocellulose membrane, hydrophilic material.
  • a variant of the test strip was made, where the materials of the functional zones are located on the hydrophobic material butt-to-butt, as well as a variant - "with overlap".
  • the layout of the functional zones on the test strip is shown in FIG. 1 (A): zone 1, with an overlap on zone 2 or up to it; zone 2, with an overlap on zone 3 or up to it; zone 3, with the edges under zones 2 and 4 or up to them; zone 4, with an overlap on zone 3 or up to it.
  • the antibody solution obtained by example 1.7 was applied on the corresponding zones.
  • such a solution was premixed with a chromatophore – colloidal gold or latex balls and, in one of the variants, any of the sugars was added – to protect against aggregation, for example, mannitol, trehalose or sucrose.
  • This test strip was tested – a solution washed off from a saliva sample of a healthy person and a patient with the new coronavirus infection were applied. The state of people was confirmed by the result of PCR diagnostics and additionally by CT for the sick patient.
  • One strip was detected in 3.2 zone of the test strip with a sample of the healthy person, which corresponds to a negative analysis for the new coronavirus, two strips were detected in 3.1. and 3.2 zones on a test strip with a sample of the sick person, which corresponds to a positive test for coronavirus.
  • saliva was collected and the zone 1 of the strip was placed at the collected saliva sample, as well as when a drop of saliva was placed directly in zone 1 of the test strip. This indicates the convenience of the test strip for use.
  • the resulting test strip was laminated - covered with a material that isolates the zones from the external environment, except for the sample application zone, or partially covers it and leaves a place for the sample application.
  • the sample was applied not only as indicated above, but also the test strip itself abundantly touched the mucous membrane of the nose and mouth. The results showed that the application of an isolating material that permits to see the test result - 1 or 2 strips, as well as the type of sample application - did not affect the performance, which also allows considering the variant of using such a test strip without any additional objects.
  • test strip was also tested using samples of other biological liquids, and the results were also accurate – they corresponded to similar results shown by other test systems.
  • test strips on people when testing test strips on people, a positive result – two strips – was shown in some of people who considered themselves healthy, and who were not diagnosed using other tests. Such people self-isolated themselves and monitored their condition. Several people were subsequently diagnosed with the new coronavirus infection. This means that the developed test strip and the diagnosticum containing it can also detect asymptomatic carriers of infection, as well as the disease in the early stages.
  • the test strip was placed in a case, preferably a plastic one, while zone 1 was available for applying a sample, partially or completely, 3.1 and 3.2 zones were covered with a transparent film, zones 2 and 4 were covered with a case.
  • the express diagnostieredum included a plastic spatula or a pipette connected to the case, for collecting saliva and its direct contact with zone 1 of the strip.
  • saliva was collected using a device with cotton - cotton bud, cotton swab. Then it touched zone 1. In all variants a reliable result was obtained.
  • an additional container with a liquid to dissolve the sample for example, 0.9% NaCl or 0.9% NaCl in phosphate buffer, but not limited to them
  • a sample taken by device for taking a sample from the mouth and/or nasopharynx was dissolved and applied to zone 1.
  • the container with the liquid had a conic form, and after placing and stirring the sample or device with the sample, its tip was cut off and the contents were squeezed out dropwise onto zone 1 of the test strip.
  • actions were taken after sampling to promote mixing of the liquid and the sample, while the liquid did not enter the mouth and nose.
  • test strip and express diagnosticum is high and detects the virus if it is present in quantities of 10 3 .
  • the proposed group of inventions can be successfully used in the diagnosis of infection caused by SARS-COV-2.
  • N domain from 216 to 360 amino acid residues of N protein of the new coronavirus
  • N domain from 216 to 360 amino acid residue of N protein of the new coronavirus

Abstract

Inventions relate to molecular biology, biotechnology, medicine. An express diagnosticum, a test strip that is part of it or is an independent diagnostic unit are proposed. The advantages are detection of virus from the first days of infection, ease of use, quick detection of coronavirus (up to 10-15 minutes), accuracy, reliable functioning, specificity, the ability to determine the presence of SARS-CoV-2 even at home conditions. The invention allows to detect the presence of the virus directly in the test sample - mainly in saliva. Also, an antibody being an active agent of the test strip and binding to proteins of SARS-COV-2 and to fusion protein of the invention, a composition containing this antibody, fusion protein including fragments of M, S, N, E proteins of the SARS-COV-2 and genetic construct providing its synthesis in a producing organism are proposed for use in the diagnostics of SARS-COV-2.

Description

Express diagnosticum for SARS-COV-2
The invention relates to molecular biology, biotechnology, medicine and can be used for express diagnostics of SARS-CoV-2.
Coronaviruses (CoV) are a large family of viruses that cause illness from a common cold to more serious illnesses, such as the Middle East respiratory syndrome (MERS-CoV) and severe acute respiratory syndrome (SARS-CoV). The new coronavirus (nCoV, COVID-19, SARS-CoV-2) is a new strain that has never been detected in humans before [https://www.who.int/ru/health-topics/coronavirus/coronavirus]. A feature of this strain is the rapid spread from person to person, as well as the complex course of the disease.
The first cases of COVID-19 infection were recorded in China in December of 2019 year. On April 9, 2020, a total of 1,589,256 cases of COVID-19 and 94,949 deaths were registered in the world. Most cases and deaths were in USA (459,981 and 16,372, respectively), Italy (143,626 and 18,279, respectively), Spain (152,446 and 15,238, respectively). As of mid-July 2020, 10.8 million cases and about 520,000 deaths were registered in the world, the United States are on the first place for morbidity and fatalities cases (2.7 million and 130,850, respectively), followed by Brazil (1.45 million and 60,813, respectively). At the same time, at the beginning of August, the number of cases is 18.3 million, deaths – about 700 thousand. Cases of coronavirus and deaths due to it have already been recorded in 213 countries of the world [https://www.worldometers.info/coronavirus/]. Obviously, the infection rate is extremely high, despite the measures taken.
Among the conditions observed in sick people there are ARDS, acute kidney injury, cardiac injury, liver dysfunction, arrhythmia, lethal outcome is not uncommon. The external support for respiratory function is required for majority of patients [Arabi, Y.M., Murthy, S. & Webb, S. COVID-19: a novel coronavirus and a novel challenge for critical care. Intensive Care Med (2020)].
SARS-CoV-2 belongs to Coronaviridae family of the Beta-CoV B line. It is a single-stranded RNA-containing virus. The epithelium of the upper respiratory tract and epithelial cells of the stomach and intestines are the entrance gate of the pathogen. The penetration of SARS-CoV-2 into target cells that have angiotensin converting enzyme type II (ACE2) receptors is the initial stage of infection. However, the type II alveolar cells of lungs (AT2) are the main target of the virus is, which is decisive in the development of pneumonia [World Health Organization. Clinical guidelines for the management of patients with severe acute respiratory infection suspected of being infected with a novel coronavirus (2019-nCoV). Interim recommendations. Published Date: January 25, 2020 URL: http://www.euro.who.int/__data/assets/pdf_file/0020/426206/RUS-Clinical-Management-ofNovel_CoV_Final_without-watermark.pdf?ua=1].
It is known that a reverse transcription PCR has become a standard method for laboratory diagnostics of COVID-19. Material obtained by taking a swab from the nasopharynx and/or oropharynx is the main type of biomaterial for laboratory research.
However, the reverse transcription PCR method has limitations for clinical diagnosis and treatment despite its wide applicability [Yu F., Yan L., Wang N. Quantitative Detection and Viral Load Analysis of SARS-CoV-2 in Infected Patients // Clin. Infect. Dis. 2020]. Its relatively low sensitivity, duration and labor intensity are the disadvantages of this method. A potentially high level of false negative results is reported for this testing method [Li Y., Yao L., Li J. Stability Issues of RT-PCR Testing of SARS-CoV-2 for Hospitalized Patients Clinically Diagnosed with COVID-19 // J. Med. Virol. 2020]. The specified disadvantages do not allow using the PCR-based method for rapid diagnosis of coronavirus infection.
It is reported about the development and clinical application of a rapid combined IgM-IgG antibody test for diagnosing SARS-CoV-2 infection [Li Z., Yi Y., Luo X. Development and Clinical Application of A Rapid IgM-IgG Combined Antibody Test for SARS-CoV-2 Infection Diagnosis // J. Med. Virol. 2020]. The overall test sensitivity was 88.66% and the specificity was 90.63%. The combined IgM-IgG assay can be used for the rapid screening of SARS-CoV-2 carriers, being symptomatic or asymptomatic, in hospitals, clinics and testing laboratories, however, it cannot be used at home. This is an ELISA on test strips, not quantitative, for the analysis of liquids such as whole blood, serum and plasma. Also, a feature of this type of testing is that the virus is not detected directly, but indirectly - through antibodies to it. Considering that IgM antibodies are detected in the patient's blood after 3-6 days, and IgG - after 8 days [Lee HK, Lee BH, Seok SH, et al. Production of specific antibodies against SARS-coronavirus nucleocapsid protein without cross reactivity with human coronaviruses 229E and OC43. J Vet Sci. 2010;11(2):165-167, Wan ZY ZX, Yan XG IFA in testing specific antibody of SARS coronavirus. South China J Prev Med 2003;29(3):36-37], this test is unambiguously inapplicable within first 1 to 3 days after infection even in the presence of symptoms, partially applicable from 3 (better 6) to day 8 – IgM antibodies will be shown, and completely applicable only starting from day 9. It is also worth considering that antibodies formed at such time period have low affinity. Also, considering that the blood is required for the test, such a test does not seem applicable for home use even from day 9, especially that a person may already be in the hospital at that time.
The purpose of the present invention is to create a test for rapid diagnostics of SARS-CoV-2, which will allow from the first days of infecting to detect infected patients and asymptomatic carriers quickly, simply and reliably, for preventing transmission of the virus and ensuring timely treatment of patients.
We propose a test strip and an express diagnosticum containing it for express diagnostics of SARS-CoV-2. The test for antibodies to coronavirus described above can be considered a prototype with a long stretch of imagination.
The technical result consists mainly in identifying the presence or absence of the virus from the first days of infection assumption due to the fact that the test is aimed to detect SARS-CoV-2 directly, and not the immune response to it, which appears later, and is sensitive even to low concentrations of the virus.
The technical result of the proposed invention is the ability to obtain an accurate result within 10-15 minutes. The mentioned technical result is achieved by the fact that the test system for determining SARS-CoV-2 according to the invention is based on the method of immunoprecipitation, in which viral particles are detected using stained specific antibodies. It is also achieved by the fact that there is no long-term pre-preparation of a sample for analysis, only 10-15 minutes pass from the intention to conduct a test, if it is available, till getting the result, unlike the 15 minutes for test for antibodies, which is preceded by at least another 15 minutes for blood sampling and preparation of sample for analysis.
The technical result is also the ability to determine the presence of SARS-CoV-2 even at home – out of laboratory - for self-monitoring of health. This technical result is achieved by the fact that a sample of fluid from the nasopharynx and/or oropharynx is the main type of biomaterial for research, but other biological liquids can also be studied.
The technical result is also in the accuracy of determining the presence or absence of coronavirus in the test sample. This is achieved by the fact that the test is aimed at detecting the virus by a direct method - i.e. the technology is used which allows to evaluate exactly the virus presence, and not the immune response induced by it.
The technical result also consists in specificity, due to the specificity of antibodies used in the test exclusively for SARS-CoV-2. What is important is that these antibodies will not interact with the body's molecules that bind to ACE2, which means the absence of probability of a false positive result.
The technical result also consists in reliable functioning, reducing the number of false positive and false negative results by increasing the specificity and accuracy of the test, due to the technical characteristics of the test system elements.
The technical result also consists in simplifying and reducing the production cost of the test system by avoiding the establishment of large-scale production and processes of purification and folding of the recombinant protein in vitro due to the fact that a large amount of antibodies is required for the production of the test. The production of antibodies using animals is more cost effective than of a recombinant protein being correctly folded with sites available for antibody binding; they can be produced in large amounts at a lower cost.
The technical result is also in the increasing of the self-diagnostics availability in the population, due to the simplicity of the analysis, especially by using only a test strip with an insulating coating in one of the variants, without using any additional objects. This also leads to a technical result of reducing the amount of waste.
The technical result also consists in expanding the range of methods for diagnosing coronavirus. This test system will allow to detect coronavirus in case of unwilling or impossibility of using analogues due to their disadvantages described above, or banal logistical problems or policy features.
In the situation of a pandemic, it is extremely important to implement the testing quickly and on a large scale, which will allow to detect the patients and carriers of infection timely and to protect against the spread and severe course of the disease, and fatal outcomes. The proposed express diagnosticum and the test strip on which it is based meet this requirement as no other test systems currently known.
New original objects used to obtain test strips and diagnosticum are proposed also. The technical result from the use of these objects is the obtaining of the test strip and the express diagnosticum according to the invention.
It is an animal antibody for use in diagnosing the presence of SARS-COV-2. It is contained in a test strip and diagnosticum for detecting coronavirus. A composition is also proposed containing such antibody in an effective amount for use in the diagnostics of the presence of SARS-COV-2.
A fusion protein and a genetic construct are also proposed that provide the synthesis of this fusion protein in a producing organism for use in diagnosing coronavirus infection. An antibody of the invention binds to such fusion protein. Binding occurs to a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
This group of inventions will increase the chances of accelerating the fight against this infection due to the fact that the problem of the new coronavirus is very acute, and not many manage to bring a test system to the market, and the effectiveness and accuracy of analogues allow to consider the creation of alternatives actual.
The present invention is an express diagnosticum for SARS-COV-2, which allows to determine the presence of SARS-CoV-2 in a sample of biological material by the immunoprecipitation method. Any biological liquid, for example, material obtained by taking a swab from the nose, nasopharynx and/or oropharynx, bronchial lavage water obtained by fibrobronchoscopy (bronchoalveolar lavage), (endo) tracheal, nasopharyngeal aspirate, sputum, biopsy or autopsy lung material, whole blood, serum, urine can be the biological material for research. For the convenience of diagnosticum use, the material obtained by taking a swab from the nasopharynx and/or oropharynx, or simply saliva is the main type of biomaterial. Whole blood must be coagulated prior to testing, and serum can be applied directly to the test strip.
Express diagnosticum contains a test strip described in detail below, enclosed in a case, a device for taking a sample, and, in one of the embodiments – a container with a liquid for dissolving the sample. It can be a kit of 2 to 3 mentioned components, or a device. In the second variant, the case of the test strip can be connected to a device for collecting a sample, the latter can be connected with a removable container with a liquid to dissolve the sample. In the case of a kit, the container with a liquid for dissolving the sample may have a conical lid, which, after dissolving the sample, can be cut off and used for the convenience of applying the obtained liquid to the test strip.
The sampling device is represented, for example, by a cotton swab, a cotton bud, a spatula or a pipette, but is not limited to them. It can be used to collect saliva, blood, and other biological fluids. The diagnosticum may also contain a scarifier and disinfectant material, such as an alcohol wipe, for blood sampling.
It may include a container, such as a test tube, with a liquid to dissolve the sample. A volume of 1-2 ml is sufficient for these purposes. The liquid for dissolving the sample can be a buffer solution, such as isotonic saline (0.9%NaCl) or PBS (0.9% NaCl in a phosphate buffer), but is not limited to them. The transfer of viral particles from a sample collection device, such as a swab, into the liquid phase is the purpose of the sample dissolving liquid – the washout solution. Depending on the design of the strip, either an aliquot of the obtained sample is applied to a specific zone, or the edge of the strip is immersed in the prepared sample. The express diagnosticum contains the user manual also.
If blood is the sample, then either a mixture of preferably coagulated blood with a buffer is applied, or a buffer is applied to a drop of blood applied to the test.
It is correctly to use the TCID 50/ml value, which shows the viral load. It is known that the average viral RNA load, when a sample is taken from nasopharynx/oropharynx, is 6,76 × 105 copies per investigated sample up to 5 days, maximum 7,11 × 108 copies per investigated sample. The average viral load in sputum is 7×106 copies per ml, with a maximum of 2,35 × 109 copies per ml. The test will be sensitive with a sample viral load of 103 copies or more.
The test strip is represented by a strip of the underlying material, on which functional zones represented by carriers and active agents are located. The layout of the functional zones on the test strip is shown in FIG. 1 (A): zone 1, with an overlap on zone 2 or up to it; zone 2, with an overlap on zone 3 or up to it; zone 3, with the edges under zones 2 and 4 or up to them; zone 4, with an overlap on zone 3 or up to it. The fluid flow is carried out by capillary forces.
The low wettability of the material - hydrophobicity – is the main requirement for the strip of the underlying material – for the substrate. A plastic with a wetting angle greater than 80 is considered a hydrophobic material. Most plastics, such as polycarbonate, pvc, and polyethylene, meet this condition.
The first functional zone - sample application zone - is represented by a hydrophilic material that comes into contact with the sample for analysis. The separation of large contaminating particles (cells and their debris), capture of viral particles from the sample and their transfer with the fluid flow further to the conjugation zone are the tasks of this zone. A high capillary absorbency determined by the migration distance more than 10 mm/min is the main criterion for the material used in this zone. For example, it can be a "pillow" of cellulose, obtained by pressing layers of filter paper, or just chromatographic paper, but not limited to them.
The second functional zone, or conjugation zone, is represented by a carrier made of a hydrophilic material that transfers liquids well, while weakly adsorbing proteins, which is coated with specific colored antibodies, such as, rabbit antibodies, conjugated with chromatophore particles – complexes of specific antibody(ies) with a chromatophore. Such a carrier material has an antibody binding value of less than 30 μg/cm2, optimally - about 20-25 μg/cm2, and is represented, for example, by cellulose acetate. For example, this parameter is >200 μg/cm2 for antibodies and about 120 μg/cm2 for proteins among the materials binding protein molecules well, such as nitrocellulose and nylon.
Specific antibodies are obtained from the serum of animals, such as rabbits, but not limited to them, immunized with a recombinant polypeptide consisting of several SARS-CoV-2 antigens - a fusion protein of the invention - or a genetic construct for its synthesis in the cells of the producing organism. The polypeptide, or plasmid or viral DNA, is produced in the culture of bacteria, for example, E. coli, B. subtilis, but not limited to them, the linear genetic construct - by PCR using plasmid or viral DNA as a matrix, then they are purified and used to immunize animals. Specific monoclonal or polyclonal antibodies are isolated from the serum obtained from animals, such as goat or rabbit. In this way, it is possible to obtain antibodies in large amounts. Thus, a composition is obtained comprising antibodies in an effective amount for use in diagnostics of the presence of SARS-COV-2 by mixing them with the target additive.
The resulting antibody composition is divided into two aliquots, one of which is marked with a chromatophore, for example, with colloidal gold or colored latex beads, but not limited to them - these are specific colored polyclonal or monoclonal antibodies for the second functional zone. Another aliquot is used for the third functional zone, more precisely, for 3.1 zone.
During the test, a liquid containing viral particles (see Fig. 1 A, zone 1) wets the second zone and dissolves the complexes of antibodies with a chromatophore particle, leading to the formation of colored complexes of antibody with viral particle, which, with a stream of liquid, enter the further – the precipitation zone. The chromatophore-antibody complex is a “ball” of the chromatophore, “covered” with antibodies (see Fig. 1 A, zone 2). If there is a virus in the test sample, these particles form a complex with the virus through the bound antibodies, in the conjugate zone (see Fig. 1 B, zone 2). If colloidal gold is used as a chromatophore, there are approximately 50-100 antibody molecules per particle.
The third functional zone, the precipitation zone, consists of a nitrocellulose membrane, represented by two regions - one (see Fig. 1A, zone 3.1) is coated with unlabeled antibodies from the second aliquot - specific to the proteins of the new coronavirus, another one (see Fig. 1 A, zone 3.2) is coated with the secondary antibodies specific to antibodies of an animal, in which specific antibodies for zone 2 are obtained, - for example, goat secondary antibodies to rabbit, mouse immunoglobulins, but not limited to such. Exactly nitrocellulose is used in this zone, since only such a material makes it possible to preserve the functional activity of the proteins deposited on it while simultaneously blocking nonspecific binding with the preservation of transport function with the fluid flow. In addition, the binding of antibodies on nitrocellulose membrane from zone 3 is higher than for a standard protein, for example, BCA (200 μg/cm2 against 120 μg/cm2).
The stained chromatophore-antibody-viral particle complex will linger in 3.1 zone during the test, and the stained chromatophore-antibody complex not having bound the virus - in 3.2 zone (see Fig. 1 B, zone 3).
In 3.1 zone - of specific antibodies, - the specific antibodies on the membrane keep the chromatophore conjugates with the same specific antibodies, due to bonds through the epitopes of the virus (see Fig. 1 B, zone 3.1).
The stained complex immobilized on secondary antibodies of 3.2 zone serves as a control for the correct performance of the test (see Fig. 1B, 3.2 zone). In 3.2 zone - of internal control - the chromatophore particles are held in place by the binding of secondary antibodies with primary antibodies. This demonstrates the integrity of the conjugate of the chromatophore with specific antibodies.
The development of a specific coloration depends on the connection of the virus-antibody-chromatophore complex with antibodies immobilized on the membrane. There are less of antibodies immobilized on the membrane, both specific and secondary, than antibody-chromatophore conjugates. In terms of the test strip, the difference is about 10 times between immobilized and conjugated antibodies: about 150 ng against 1 μg. If there is a big amount of virus, and thereby of complexes, then not all the complexes will stay on the membrane in 3.1 zone, and some of them will pass to 3.2 zone. If there is a little amount of virus or no virus, then the unbound conjugate will also pass to 3.2 zone.
Finally, the fourth functional zone, or the capillary pump zone, consists of the same material as zone 1, for example, of filter paper, and provides fluid flow and maximum transfer of molecules from the first functional zone to the third – to the precipitation zone, including the formed viral particle-stained specific antibody complexes.
The test strip may additionally contain a coating that isolates the conjugation, precipitation, capillary pump zones from the external environment. In one embodiment, such a coating also isolates a part of the sample application zone. Such a test strip can be used without additional elements (case, etc.) for diagnosing SARS-COV-2.
A positive test result is the presence of coloration in both areas in the third zone of the test strip - in the precipitation zone. The presence of coloration only in the zone of secondary antibodies (zone 3.2) indicates the absence of viral particles in an amount sufficient for detection.
The presence of coloration only in the zone of specific antibodies (zone 3.1) or blurring of the coloration zones indicate a technical problem of the test - for example, the destruction of the antibody-chromatophore conjugate.
The test based on immunoprecipitation on a test strip is of high quality, therefore it is not sensitive to an excess of the tested antigen. Any amount of antigen above the detection threshold will stain 3.1 zone, and conjugate, whether bound with the virus or not, will stain 3.2 zone.
When making a test strip, a composition containing a complex of antibodies with chromatophore particles is applied to the conjugation zone, as well as a composition containing specific antibodies in an effective amount - to the first region of the precipitation zone (3.1), a composition containing secondary antibodies to specific antibodies - to the second region of the precipitation zone (3.2). In this case, after applying the complex of antibodies with chromatophore particles, drying is carried out, preferably freeze-drying. To dry the conjugate, it is desirable to apply it in the composition of a stabilizing buffer containing any of the sugars - to protect it from aggregation by adding sugars, for example, mannitol, trehalose or sucrose.
In a large-scale production, in one embodiment a plate is made which is formed of zones with applied reagents, additionally covered with an isolating material partially or completely, as described above, and then cut into test strips.
An antibody contained in the test strip and diagnosticum was also proposed to detect SARS-COV-2. It is an active agent of the test strip for diagnostics of SARS-COV-2 presence. Such antibody binds to a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue. The antibody binds to SARS-COV-2 coronavirus protein with an affinity of at least 1×108 l/mol, measured as an Association constant (Ka), as determined by the Scatchard analysis. This antibody is obtained as a result of the introduction to the animal of the developed fusion protein or genetic construct according to the invention (see below) - immunization. It can be a rabbit antibody, but is not limited to it.
A composition containing such an antibody in an effective amount for use in diagnostics of SARS-COV-2 presence is also proposed. Such a composition is used in the manufacture of a test strip and diagnosticum - it is applied on the appropriate areas to form the functional zones of the test strip. Such a composition is obtained by introducing the developed fusion protein or genetic construct (see below) to an animal, taking blood, isolating specific antibodies from it and mixing with the target additive.
A fusion protein and a genetic construct including a polynucleotide encoding the specified fusion protein and other elements that provide synthesis of this fusion protein in the producing organism, for use in the diagnostics of coronavirus infection are also proposed. A fusion protein for use in the diagnostics of infection caused by SARS-COV-2 comprises fragments of M, S, N, E proteins of such coronavirus connected by flexible bridges, and is set forth as SEQ ID NO:1 or SEQ ID NO:2 amino acid sequence.
The antibody of the invention binds to such fusion protein and to SARS-COV-2. Binding occurs with a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
By genetic construct primarily a linear DNA fragment or a recombinant vector is meant, which can be represented by a viral or plasmid vector.
The recombinant vector must comprise elements essential for the organisms of its maintenance and use, together with the corresponding regulatory sequences. Regulatory sequences are nucleotide sequences which can affect gene expression at the level of transcription and/or translation, as well as mechanisms that ensure the existence and maintenance of the recombinant vector functioning.
An origin of replication, for maintaining in a cell with medium and preferably high copy number, and a marker gene for a producer strain selection are essential to the prokaryotic system. Bacterial elements of a plasmid DNA should not adversely affect expression in mammalian cells and cause a side effect of using the plasmid DNA. A suitable origin of replication is represented by pM1 (der.), ColE1 (der.), and F1, pUC, and F1, but is not limited to such. A suitable marker gene is represented by a reporter gene or antibiotic resistance gene, for example, ampicillin, mainly kanamycin, but is not limited to such.
Elements for efficient functioning, for expression of the encoded gene, - a promoter, including transcription initiation signals, mRNA leader sequence, a termination sequence, regulatory sequences, - are essential elements of a recombinant vector for use in mammals.
A promoter is an important component of a vector that triggers the expression of a gene of interest. Human CMV / immediate early or CMV-chicken-β actin (CAGG) promoter are classic promoters for recombinant vectors - drug components. CMV promoters are used for most DNA vaccines, as they mediate high levels of constitutive expression in a wide range of mammalian tissues [Manthorpe M, Cornefert-Jensen F, Hartikka J, et al. Gene therapy by intramuscular injection of plasmid DNA: studies on firefly luciferase gene expression in mice. Hum. Gene Ther. 1993; 4 (4): 419–431] and do not inhibit downstream expression. An increase in the expression level is observed when the CMV promoter is changed, for example, by incorporating HTLV-1R-U5 downstream the cytomegalovirus promoter or when using the chimeric SV40-CMV promoter [Williams JA, Carnes AE, Hodgson CP. Plasmid DNA vaccine vector design: impact on efficacy, safety and upstream production. Biotechnol. Adv. 2009; 27 (4): 353-370]. Tissue-specific host promoters which allow avoiding constitutive expression of antigens in inappropriate tissues are an alternative to CMV promoters [Cazeaux N, Bennasser Y, Vidal PL, Li Z, Paulin D, Bahraoui E. Comparative study of immune responses induced after immunization with plasmids encoding the HIV- 1 Nef protein under the control of the CMV-IE or the muscle-specific desmin promoter. Vaccine 2002; 20 (27–28): 3322–3331].
The promoter can be with corresponding regulatory sequences from natural promoters with its own regulatory elements (CaM kinase II，CMV, nestin, L7, BDNF, NF, MBP, NSE, p-globin, GFAP, GAP43, tyrosine hydroxylase, subunit 1 of the kainate receptor, and subunit B of glutamate receptor, and others), or from synthetic promoters with regulatory sequences to obtain the desired expression rate (ratio of duration and expression level) of a target gene at the transcription level.
Possible regulatory sequences in relation to the promoter:
- enhancer, to increase the level of expression through improve of RNA polymerase and DNA interaction.
- insulator, to modulate the functions of the enhancer,
- silencers, or fragments thereof, to reduce the level of transcription, for example, for tissue-specific expression,
- 5` untranslated region upstream promoter, including an intron.
Regulatory sequences are nucleotide sequences that may affect gene expression at the level of transcription and/or translation, as well as mechanisms that ensure the existence and maintenance of the genetic construct functioning. The recombinant vector, the plasmid or viral DNA of the present invention, contains at least one of the abovementioned regulatory sequences, depending on the DNA variant, based on the selection of promoter and the desired expression parameters of the target gene. Based on the existing level of technology and known and obvious variants of such elements and their use, the recombinant vector according to the present invention may contain any combinations meeting the above-mentioned criteria, using which synthesis of the developed fusion gene is performed from it, in cells of a target organism – a human or an animal. When using a silencer or an insulator in the construct, it is possible to regulate the expression of the target gene.
Other regulatory sequences:
- untranslated region downstream the promoter, including an intron, to increase mRNA stability and the target gene expression.
The recombinant vector of the present invention in one embodiment additionally comprises such a regulatory element.
The recombinant vector of the present invention also contains such an important element as mRNA leader sequence containing translation initiation signals, a start codon. Translation initiation signals is Kozak sequence in eukaryotes [Kozak M. (1986) "Point mutations define a sequence flanking the AUG initiator codon that modulates translation by eukaryotic ribosomes", Cell 44, 283-292].
The recombinant vector also contains a site, mainly different sites, for cloning of the target gene, for the correct target gene orientation in the recombinant vector, and a site, mainly sites, for primers annealing for its sequencing.
The recombinant vector also contains the polynucleotide encoding the fusion protein of the invention. When the amino acid sequence of a protein is known, one skilled in the art will be able to obtain the nucleotide sequence. This can be a sequence either based on fragments of the native nucleotide sequence of viral proteins, or artificially optimized by codon composition. Codon optimization can be carried out independently, using information on the frequency of codons occurrence in a producer, for example, in a database [for example, Nakamura Y, Gojobori T, Ikemura T. Codon usage tabulated from international DNA sequence databases: status for the year 2000. Nucleic Acids Res . 2000 Jan 1; 28 (1): 292], or using specialized programs, for example, available at http://www.encorbio.com/protocols/Codon.htm or molbiol.ru or other resources.
A polynucleotide may not contain (e.g., SEQ ID NO.:5 or 6) or contain (e.g., SEQ ID NO.:7 or 8) a heterologous secretory sequence optimized in codon composition for the target organism - for example, such of TPA (tissue-type plasminogen activator), hGH (human growth hormone), IGF (insulin-like growth factor), EPO (erythropoietin), but not limited to such.
The recombinant vector also contains a termination sequence containing sequentially a stop codon, a 3` untranslated region with a polyadenylation signal and site, a stop codon; due to which mRNA stability is maintained, and transcription is terminated appropriately, and mRNA is exported from the nucleus. Gene expression can be influenced by changing the termination sequence, which is necessary for mRNA stability maintaining, for proper transcription termination and mRNA export from the nucleus, including by its shortening. In many modern DNA vaccines the bovine growth hormone transcriptional terminator sequence is used [Montgomery DL, Shiver JW, Leander KR, et al. Heterologous and homologous protection against influenza A by DNA vaccination: optimization of DNA vectors. DNA Cell Biol. 1993; 12 (9): 777–783]. Polyadenylation (polyA) is necessary to stabilize the transcript. Alterations to the polyA sequence can lead to the increase of gene expression [Norman JA, Hobart P, Manthorpe M, Felgner P, Wheeler C. Development of improved vectors for DNA-based immunization and other gene therapy applications. Vaccine 1997; 15 (8): 801–803]. In pVAX1 plasmid (Invitrogen, Carlsbad, Calif.), the bovine growth hormone terminator region contains a homopurin region which is sensitive to nuclease. It is shown that an alternative polyA sequence may significantly improve plasmid stability to nuclease [Azzoni AR, Ribeiro SC, Monteiro GA, Prazeres DMF. The impact of polyadenylation signals on plasmid nuclease-resistance and transgene expression. J Gene Med. 2007; 9: 392–402]. The introduction of two stop codons preceding the 3` untranslated region allows to increase the efficiency of the transcription terminator. Based on the existing art and known and obvious variants of such an element, the recombinant vector according to the present invention may contain any termination sequence meeting the above-mentioned criteria, using which synthesis of a target protein is performed in cells of a human or animal. An example of a termination sequence for mammalian cells is that of bovine growth hormone (BGH).
Other elements may also be contained for the functioning of the expression system. The sequence of arrangement of the described elements in a recombinant vector is clear to the average person skilled in the art.
By a virus-based vector in which the polynucleotide is cloned, a safe vector is meant, such as, i.e. a recombinant adeno-associated virus, but not limited to such.
By a linear DNA fragment a DNA fragment is meant containing a promoter, an mRNA leader sequence, the polynucleotide described above, a termination sequence, including 1 or 2 stop codons, regulatory sequences. Specification described above is applicable to the elements. Such elements are crucial, but other elements may also be contained. A fusion protein is synthesized from such a fragment in the cells of a target organism. The arrangement sequence of the described elements is clear to the average person skilled in the art.
For a recombinant vector for expression of the polynucleotide encoding the fusion protein of the invention in an organism other than a mammal, the corresponding and additional elements may be contained. An element for integrating the construct into the genome of the producer may also be contained - for example, 3 'AOX1 or 18S rRNA for yeast. When using bacteria as a producer, the selective marker may be represented, for example, by the gene of resistance to ampicillin or kanamycin, or tetracycline; yeast - for example, the gene LEU2 or TRP1, or URA3; fungi - for example, the gene of resistance to bialaphos or hygromycin or aureobasidin or bleomycin; plants - for example, the gene of resistance to kanamycin or bialaphos.
When Escherichia coli organism is used as a producer, promoter can be represented, for example, by the promoter of the lactose operon, tryptophan operon; yeast - for example, promoter of the gene of acid phosphatase, alcohol dehydrogenase gene, the gene of glyceraldehyde-3-phosphate dehydrogenase, the gene of the galactose metabolism; fungi – for example, promoter of the gene of cellobiohydrolase, either α-amylase or glucoamylase, or glyceraldehyde-3-phosphate dehydrogenase, or the gene abp1; plants – for example, CaMV 19S RNA promoter or the CaMV 35S RNA promoter or a gene nepalisite promoter.
Signals of the initiation of translation is the sequence of Shine — Dalgarno [Kapp L. D., Lorsch J. R. The molecular mechanics of eukaryotic translation // Annual Review of Biochemistry 73/2004, 657—704] in prokaryotes and the Kozak sequence in eukaryotes.
An example of a terminating sequence for the plant cells is such of nopalin synthase gene (NOS T).
For secretion of the fusion proteins according to the invention, at the N-end of a polynucleotide encoding the target gene a signal peptide suitable for the used producer organism is placed. Examples of such secretory sequences are described in the literature [for example, for E. coli in the patent of Russian Federation №2198179, priority date 15.09.1999 for yeast - in the patent of Russian Federation №2143495, priority date 08.07.1994, U.S. patent No. 4546082, the priority date of 17.06.1982, the European patent №116201, 123294, 123544, 163529, 123289, the application for the invention of Denmark 3614/83, the priority date of 08.08.1983 for plants – in articles Kapila J, Rycke RD, Van Montagu M, Agenon G (1997) An Agrobacterium-mediated transient gene expression system for intact leaves. Plant Sci 122: 101-108, Stiefel, V., Ruiz-Avila, L., Raz, R., Valles, M.P., Ghez, J., Pages, M., Martinez-lzquierdo, J.A., Ludevid, M.D., Langdale, J.A., Nelson, Т., and Puigdoménech, P. (1990). Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation. Plant Cell 2, 785-793].
Additional elements required for the functioning of an expression system of a producer organism and a recombinant vector may also be contained. Based on the existing level of technology and the known and obvious variants of such elements and their use, genetic construct according to the present invention may contain any combinations meeting the above-mentioned criteria, using which expression of the fusion gene is performed in producer organism.
If E. coli cells are selected as a producer, the gene can be a part of a bacteriophage, for example, on the basis of phage λ, or plasmids, for example, on the basis of the pBR or pUC, and the like. When Bacillus subtilis is used as a producer organism, the gene can be, for example, in a plasmid based on pUB. When yeast are used as a producer, a genetic structure can be represented, for example, by a plasmid-based YEp or YRp or YCp or YIp. etc.
Producers of fusion proteins described are also given, based on a prokaryotic or an eukaryotic organism except humans comprising the given genetic construct. A prokaryotic producer is represented, for example, by Escherichia coli, Bacillus subtilis, eukaryotic producer - fungi, cells of plants, mammals.
The named objects of the invention, apart from express diagnosticum and test strips directly, can also be used for other types of diagnostics of infection caused by SARS-COV-2.
The invention is illustrated by the following drawings.
Fig.1
Scheme of the test stripe: 1 - sample application zone, 2 - conjugation zone, 3 – zone of result, precipitation zone: 3.1 - specific antibodies zone, 3.2. - internal control zone, 4 - capillary pump zone, A - before applying a sample for analysis, B - after applying a sample for analysis containing new coronavirus.
Fig.2
Photo of a test strip prototype: 1 - sample application zone, 2 - conjugate zone, 3 - result zone, 4 - capillary pump area. Zone 2 is colored entirely - it contains the antibody-chromatophore conjugate, in the final diagnosticum it will be hidden under the part of the strip packaging - the case. The strip between zones 3 and 4 is the shadow at the border of the zones, in commercial kits this place is usually hidden.
Examples
The authors of the present invention have conducted laboratory studies confirming the feasibility of the characterized inventions. The obtained research results are illustrated by the following examples (1,2).
Example 1. Obtaining antibodies specific to coronavirus
1.1. Protein development for animal immunization
The authors of the present invention have developed a fusion protein comprising fragments of M, S, N, E proteins of coronavirus connected by flexible bridges for the full functioning of each domain. It is shown that when using flexible bridges slightly different in length, which is reflected in the amino acid sequence SEQ ID NO:1 or 2, the domains retained full functioning.
To model proteins, the following actions have been performed:
1. Search for components of a fusion protein
2. Building a model of the whole protein to determine the orientation of the domains
3. Building models for each domain (using samples of 3D structures and ab initio)
4. Docking of models using the whole protein model.
To obtain the most realistic results in automatic mode, I-Tasser algorithm was used to model proteins.
The modelled fusion protein in one embodiment consists of 422 aa, with methionine at the N-terminus - 423 aa, is represented by the amino acid sequence SEQ ID NO:1. Analysis of the amino acid sequence of this protein using the ProtParam program (http://au.expasy.org/tools/protparam.html) has shown that the fusion protein has a molecular mass of 46.4 kDa, pI 9.61, the protein is stable, the half-life in mammals is about 100 hours, in yeast is more than 20 hours, in E. coli is more than 10 hours. With methionine at the N-terminus - 46.5 kDa, pI 9.61, the protein is stable, the half-life in yeast and E.coli is as mentioned above, in mammals is about 30 hours.
At the same time, a variant was also evaluated when for immunization of animals to obtain antibodies, a genetic construct was used for the synthesis of the developed fusion antigen in mammalian cells. For such a variant, the protein construct was also evaluated with the addition of a heterologous signal sequence for secretion from protein-producing cells in the body.
When adding the secretory sequence of IGF (GKISSLPTQLFKCCFCDFLK), with methionine at the N-terminus, the fusion protein consists of 443 aa, has a molecular weight of 48.8 kDa, pI 9.55, the protein is stable. When adding the hGH secretory sequence (ATGSRTSLLLAFGLLCLPWLQEGSA), with methionine at the N-terminus, the fusion protein consists of 448 aa, molecular mass is 49.1 kDa, pI 9.57, the protein is stable. By adding the TPA secretory sequence (MDAMKRGLCCVLLLCGAVFVSPS), the fusion protein consists of 445 aa, molecular mass is 48.8 kDa, pI 9.53, the protein is stable.
The modelled fusion protein in one embodiment consists of 424 aa, with methionine at the N-terminus - 425 aa, is represented by SEQ ID NO:2 amino acid sequence. Analysis of the amino acid sequence of this protein using the ProtParam program (http://au.expasy.org/tools/protparam.html) has shown that the fusion protein has a molecular mass of 46.5 kDa, pI 9.61, the protein is stable, the half-life in mammals is about 100 hours, in yeast is more than 20 hours, in E. coli is more than 10 hours. With methionine at the N-terminus – 46,6 kDa, pI 9,61, the protein is stable, the half-life in yeast and E.coli is as mentioned above, in mammals is about 30 hours.
When adding the secretory sequence of IGF, with methionine at the N-terminus, the fusion protein consists of 445 aa, molecular mass is 48.9 kDa, pI 9.55, the protein is stable. When adding the secretion sequence of hGH, with methionine at the N-terminus, the fusion protein consists of 450 aa, molecular mass is 49.2 kDa, pI 9.57, the protein is stable. When adding the secretory sequence of TPA, the fusion protein consists of 447 aa, has a molecular mass of 48.9 kDa, pI 9.53, the protein is stable.
When using other secretory signals, the indicators change.
When a fusion polynucleotide is expressed in any cell, a protein is synthesized with methionine at the N-terminus, since translation always starts from the start codon. Further, methionine can be cleaved naturally, for example, if the protein is secreted, as part of the secretory peptide. Or, when purifying the protein obtained in bacterial cells, methionine can be cleaved, for example, by aminopeptidase.
1.2. Obtaining a highly purified fusion protein using a prokaryotic organism
The amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, while performing codon optimization for expression in E. coli cells using the molbiol.ru service and adding restriction sites flanking the gene. Sequences were received characterized by SEQ ID NO:3 or 4. The calculated genes were synthesized chemically.
The resulting genes were cloned into pET22b (+) bacterial expression vector according to the vector manual.
E. coli cells of the BL21 Star (DE3) strain (Invitrogen, USA), with the F-ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) genotype, containing λDe3 lysogen in the genome and the rne131 mutation were used for creating a producer strain. The mutated rne (rne131) gene encodes a truncated form of RNase E, which decreases intracellular destruction of mRNA, leading to an increase in its enzymatic stability. lon- and ompT-mutations in protease genes make it possible to obtain non-proteolyzed recombinant proteins in large amounts.
Cells of E. coli BL21 strain with F-ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) genotype were prepared as follows. The cells were incubated at +37°C for 16 h in 5 ml of L-broth containing 1% tryptone, 1% yeast extract and 1% sodium chloride. The culture was diluted with fresh L-broth 50-100 times and grown on a shaker at +37°C to an optical density of 0.2-0.3 at a wavelength of 590 nm. Upon reaching an optical density of more than 0.3, the culture was diluted with fresh L-broth to an optical density of 0.1 and grown for 30 min. 100 ml of culture were transferred into a sterile centrifuge tube and cells were pelleted at + 4°C at 5000g for 10 min. The supernatant was discarded, the cells were resuspended in deionized water in the original volume, followed by centrifugation. The washing procedure was repeated three times. After washing, the cell pellet was resuspended in a small volume of deionized water and centrifuged for 30 sec. at 5000 rpm. on a microcentrifuge.
The transformation of competent cells was performed by electroporation. To do this, 1 ml of tenfold dilute ligase mixture was added to 12 ml of competent cells, mixed and electroporation was performed on an Eporator electroporator (Eppendorf, Germany) in sterile electroporation cuvettes (Eppendorf, Germany) of 100 ml volume, 1 mm gap, with an electric pulse of 1.7 kV intensity lasting 5 msec.
After transformation, the cells were incubated in a SOC medium (2% bacto-trypton, 0.5% yeast extract, 10 mm NaCl, 2.5 mm KCl, 10 mm MgCl2, 10 mm MgSO4, 20 mm glucose) for 40 minutes at +37°C. 10-100 µl of cell suspension was sown on a selective LB medium (Gibko BRL, USA) containing ampicillin (50 μg/ml) to select clones containing plasmids (producer strains).
Grown E. coli colonies were tested for the presence of plasmids with the insertion of the target gene. A clone of cells containing the desired plasmid DNA was considered a fusion protein-producing strain. Thus, two producer strains of fusion proteins characterized by SEQ ID NO:1, 2 were obtained.
Standard agarized LB medium containing ampicillin at a concentration of 100 μg/ml and glucose at a concentration of 1% was used for cultivation of the resulting producer strains to block non-specific expression.
Expression was induced when the cell culture reached an optical density of 0.6-0.8 optical units at a wavelength of 600 nm. 0.2% lactose was used as an inducer (Studier, 2005).
The PYP-5052 medium consisting of 1% peptone (Gibco, USA), 0.5% yeast extract (Gibco, USA), 50 mМ Na2HPO4, 50 mМ K2HPO4, 25 mМ (NH4)2SO4, 2 mМ MgSO4, 0.5% glycerol, 0.05% glucose and 0.2% lactose was used for autoinduction of expression by the Studier method (Studier, 2005).
A single colony of the producer strain was inoculated in the PYP-5052 medium containing ampicillin at a concentration of 50 μg/ml. Fermentation was carried out at +37°C in a temperature-controlled rotary shaker at 250 rpm. within 20 hours until there is no significant change in the OD600 for 1 hour. An aliquot of cells was taken for analysis of the expression of the gene encoding the fusion protein, by PAGE, and the remaining biomass was precipitated by centrifugation at 9000g.
The precipitated cells were lysed using 3 sonication cycles of 30 sec with a break of 2 min on ice. Then, the destruction of inclusion bodies was carried out by incubation for an hour with a lysing buffer containing 500 mM sodium phosphate buffer, pH 8.0, 6M guanidine hydrochloride, 500 mM sodium chloride. 8 ml of the lysing buffer were added to cells collected by centrifugation from 50 ml of culture.
A column containing Ni-NTA Sepharose was pre-equilibrated with application buffer (500 mM sodium phosphate buffer, pH 8.0, 8 M urea, 500 mM sodium chloride, 10 mM imidazole). The destroyed inclusion bodies were applied on the column. The column was then washed with two volumes of the application buffer. The column was then washed with three volumes of wash buffer (500 mM sodium phosphate buffer, pH 8.0, 8 M urea, 500 mM sodium chloride, 30 mM imidazole). The protein was eluted with 5 ml of elution buffer (500 mM sodium phosphate buffer, pH 8.0, 8M urea, 500 mM sodium chloride, 200 mM imidazole). Fractions of 1 ml were collected, analyzed in 12% SDS-PAGE, fractions with the target protein were combined, the protein concentration in them was determined with the Bradford method.
Protein preparations (SEQ ID NO:1, 2) were obtained with a purity of about 97-98%, according to SDS-PAGE, the concentration of the fusion protein in each preparation was 1-2 mg / ml.
Fusion proteins were also obtained using E. coli RosettaPLys strains, as well as Bacillus subtilus strains and other vectors.
1.3. Obtaining a highly purified fusion protein using an eukaryotic organism
1.3.1. Obtaining a highly purified fusion protein using yeast cells
The amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, simultaneously codon optimization for expression in Pichia pastoris yeast cells was carried out using http://molbiol.ru/scripts/01_19.html program and adding regions flanking the gene to obtain the secreted protein, according to the manual for cloning vector. The calculated genes were synthesized chemically.
The resulting genes were cloned in pHIL-S1 eukaryotic expression vector, according to the vector manual.
Yeast cells were prepared for transformation. Cultivation and freezing of Pichia pastoris cells of SMD1163 strain, defective in several yeast proteases, which ensures the stability of the secreted protein, were carried out. The cells were seeded in sterile conditions on agar in YPD medium (1% yeast extract, 2% peptone, 2% glucose, 1 mM dithiothreitol), cultured at 30° C, then subcultured into suspension and cultured for 16 h. Some of the cells were resuspended in YPD medium with 15% glycerol addition and frozen at -86° C. To obtain competent cells, cell colonies were preliminarily grown on an agar plate in YPD medium at 30° C for two days. Then, the contents of one colony were grown in 10 ml of YPD medium at 30° С for 16 h. The suspension was diluted in YPD to an OD600 0.2 and to final volume of 10 ml and the culture was grown to an OD600 0-8 for 4 hours. The cell suspension was centrifuged for 5 min at 500 g, the supernatant was poured, the precipitate was resuspended in 10 ml of solution I from the EasyComp Transformation Kit, centrifugation was performed again, and the precipitate was resuspended in solution I. Aliquots of competent cells of 50-200 µl were poured into 1.5 ml sterile tubes, which then were stored at a temperature of -90° C before use.
The EasyComp Transformation Kit included in the Pichia Easy Select Kit (Invitrogen) was used for transformation; the reaction was carried out according to the manual for the kit. The resulting cell suspension was plated into a sterile plate on an agar gel prepared in YPD medium supplemented with 1 M sorbitol and ampicillin antibiotic at a final concentration of 100 μg/ml. After 3 days, several dozen colonies were obtained per plate. The cells from the grown colonies were transferred onto a plate with MMD (minimal medium dextrose) agar and the plate was cultured for 2 days at 30°C.
The cells of the colonies grown on the selective medium were transferred into flasks and cultured in 5 ml of MGY medium on a shaker (250 rpm) for 1 day until OD600 5. After that, the cells were pelleted by centrifugation at 3000 g for 10 min. Control of target gene expression was performed by SDS-PAGE.
After the cells were precipitated, the culture medium was filtered (pore diameter 45 μm), then Tris-HCl pH 6.0 was added to a final concentration of 20 mM. The culture medium containing the fusion protein was 5-10 fold concentrated using Millipore concentrators for proteins with a molecular weight of more than 10 kDa.
After concentration, the fusion protein preparation was heated on a water bath to boiling (t = 100°C) and boiled for 2 minutes, afterwards it was centrifuged at 4°C, 15000g for 15 minutes.
Ion exchange chromatography was carried out on CM-Sepharose. The column with CM-Sepharose was equilibrated with a buffer containing 20 mM Tris-HCl pH 6.0. The fusion protein preparation was applied at a rate of 60 ml/hour. The column was washed with 20 mM Tris-HCl pH 6.0; 20 mM Tris-HCl pH 6.0, 200 mM NaCl. Elution was performed with 20 mM Tris-HCl pH 6.0, 1 M NaCl, and fractions of 1 ml were collected.
The preparation of the obtained fusion protein was 2-fold diluted, phosphate pH 8.0 was added to a concentration of 50 mM and applied to the column. After washing the column with application buffer, ballast proteins were removed by washing with 20 mM imidazole solution in the same buffer. The protein was eluted with a solution containing 200 mM imidazole.
As a result, preparations of fusion proteins with a purity of more than 95% were obtained. The presence of bands on the electropherograms corresponding to the molecular weight of the target proteins was revealed. The obtained strains are characterized by a high level of expression of the target proteins.
Fusion proteins were also obtained using other fungi and other vectors.
1.3.2. Obtaining highly purified fusion proteins using mammalian cells
A nucleotide sequence of a gene collinear to the amino acid sequence of the fusion protein encoded by it was calculated, set forth as SEQ ID NO:1 or 2, with the target gene flanking by restriction sites, as well as with the addition of the Kozak sequence before the start codon to initiate translation, and after the start codon – a signal sequence, for example, of TPA (tissue-type plasminogen activator isoform 1 preproprotein [Homo sapiens], NCBI Reference Sequence: NP_000921.1), hGH, IGF, EPO, or represented by aa MLLLLLLLLLLALALA, for secretion of the synthesized protein from an eukaryotic cell, with simultaneous optimization by codon composition for expression in human cells, the tool on the site molbiol.ru was used. For example, sequences set forth as SEQ ID NO:5,6 and set forth as SEQ ID NO:8, respectively were obtained.
In one embodiment, instead of artificial optimization, the corresponding nucleotide sequences of the new coronavirus were taken to obtain a genetic construct, since these sequences are expressed in mammals, the remaining fragments were optimized as described above. For example, the nucleotide sequence set forth as SEQ ID NO:7 was obtained.
The calculated nucleotide sequences were synthesized by a chemical method using ASM-800 DNA synthesizer (BIOSSET, Russia).
The synthesized gene was cloned in the pcDNA3.1 (+) vector according to the vector manual. On the basis of E. coli DH10B/R cells, a producer strain of this plasmid DNA was created, according to the Protocol described in 1.4.1.1 paragraph.
The transfection of mammalian cells with the created plasmids was performed by the method of calcium phosphate precipitation.
For transforming mammalian cells (CHO) with plasmid DNAs, the cells were seeded in 12-well plates (Costar, USA) with a seeding density of 5×104 cells/cm2. The next day, the culture medium was changed to synchronize cell division. Three hours later, calcium phosphate-precipitated plasmid DNA was added to the cells. To prepare a precipitate, 250 μl of the solution containing 50 μg of DNA in 250 mM CaCl2 were slowly mixed with 250 μl of a solution (1.64% NaCl, 1.13% HEPES pH 7.12, and 0.04% Na2HPO4). After 24 hours of incubation at 37°C in an atmosphere of 5% CO2, the medium was replaced with a similar medium containing 100 μg/ml of neomycin to select clones containing plasmids with an insert of the target gene and, therefore, expressing fusion proteins, the selection was carried out for 20 days, in wells containing live cells, the medium was changed (the previous culture medium was not poured out, but was used to determine the amount of secreted proteins by ELISA), and after another day the cells were removed from the substrate and analyzed for expression of the transformed genes. The analysis of the efficiency of transfection was carried out on an EPICS XL Beckman Coulter flow cytometer (Beckman Coulter, USA).
The level of fusion proteins in the culture medium of the obtained stable CHO line transfectoms was evaluated using a standard solid-phase ELISA.
As a result of cloning, stable CHO transfectomes were obtained, which were accumulated for cryopreservation and production of an experimental batch of fusion proteins. The productivity of created CHO transfectomes expressing fusion proteins was 420-540 μg/107 cells/day.
The cultivation of producer cells was carried out using BIOSTAT® Bplus bioreactor and an autoclaved IMDM medium supplemented with 45 g of DFBS (0.5%) and 25.8 g (100 mM) of zinc heptahydrate (ZnSO4 x 7H2O) per 9 L of medium. The working mode was set up as: temperature 37°C, pH 6.9-7.2, oxygen concentration 50% of air saturation. After reaching the specified mode, the bioreactor was inoculated, for which the inoculum was introduced into it under aseptic conditions. The cultivation time was 3 days.
At the end of the cultivation, the culture fluid was filtered through a sterile Sartopure capsule (Sartorius, Germany), with a pore diameter of 1.2 µm, at a rate of 1 L/min. Then the clarified liquid was concentrated on Viva Flow 200 system (Sartorius, Germany) using a filter. Concentration was carried out until a total volume of 200 ml was reached.
Chromatographic purification was carried out in two stages using sterile solutions. At the first stage, BioLogic DuoFlow Pathfinder (Bio-Rad) system with an automatic BioFract fraction collector and YMC TriArt semi-preparative chromatographic column, 250x4.6 mm, C18 sorbent were used. Before starting work, the column was equilibrated using 200 ml of buffer (1 kg of water for injection and 1 g of trifluoroacetic acid) in manual mode through a chromatograph pump at a rate of 2 ml/min.
The prepared material in a volume of 200 ml was introduced into the chromatograph through the chromatograph pump at a rate of 0.5 ml/min. Elution was performed with a buffer (2 kg of acetonitrile, 2 g of trifluoroacetic acid) at a rate of 0.5 ml per minute. The fraction was collected at the maximum absorption at 260 nm. The volume of the fraction was approximately 500 ml.
The second stage of purification was carried out using BioSil SEC 125-5 gel-chromatographic column, 300x7.8 mm. The column was pre-equilibrated with 0.02 M PBS buffer. The resulting material was introduced into the chromatograph through the chromatograph pump at a rate of 0.5 ml/min. Elution was performed with a buffer (0.6 M NaCl solution) with a concentration gradient from 0.1 to 0.6 M. A fraction was collected with an absorption of at least 3.4 optical units at A280 nm. The fraction was collected in vials. The volume of the resulting solution for each protein preparation was approximately 1 L with the fusion protein concentration of 2-2.7 mg per ml.
The fusion proteins according to the invention can also be obtained using other mammalian cells, for example HEK293, COS, and other plasmids, for example, pVAX, but not limited to such.
An example of HEK cells use to produce the developed fusion protein.
Transient transfection of HEK293 cells conducted by calcium transfection method was used for the expression of the recombinant fusion protein. HEK293 cells were cultured at 37C in a CO2 incubator (5% CO2, 100% humidity) in a DMEM medium containing 10% embryonic veal serum, without antibiotics, with L-glutamine. The transfection was performed at 70% confluence of the monolayer. 2 micrograms of plasmid DNA were used in the volume of 5 ml of culture medium, the medium was replaced with a fresh one 24 hours after transfection, and cells were cultured for 5 days.
1.3.3. Obtaining highly purified fusion proteins using plants
The amino acid sequences of the calculated fusion proteins were converted into nucleotide ones, simultaneously the codon optimization for expression in Nicotiana benthamiana cells was carried out using http://molbiol.ru/scripts/01_19.html program and adding regions flanking the gene according to the manual of vector for cloning. The calculated genes were synthesized chemically and cloned into the pTRV1 eukaryotic expression vector. It is also possible to use a viral vector (for example, described in the article of Komarov T.V., Skulachev M.V., Zverev A.S., Schwartz AM, Dorokhov Yu.L., Atabekov I.G. New viral vector for efficient production of target proteins in plants. Biochemistry, 2006, 71 (8), 1043-1049).
The resulting vector was introduced into the Agrobaterium tumefaciens GV3101 strain, which was used for infiltration of N. benthamiana leaves. The resulting Agrobaterium tumefaciens strain carrying the fusion gene was cultured for 12 h at 30°C in a shaker. Cells (1.5 ml) were pelleted by centrifugation (4000g, 5 min), the pellet was resuspended in buffer (1.5 ml: 10 mM MgCl2, 10 mM MES (pH 5.5)), OD600 was adjusted to 0.2. The suspension of agrobacteria was applied with a needle-free syringe to the leaves of growing plants of N. benthamiana. The maximum level of protein synthesis was observed on 7-11 days after infiltration.
The expression of fusion proteins in leaf cells of producing plants was analyzed using SDS-PAGE. A leaf fragment was triturated in buffer (10 mM KCl, 50 mM Tris pH 8.0, 5 mM MgCl2, 10 mM β-mercaptotanol, 0.4 M sucrose, 10% glycerol) on day 10 after infection. The obtained extract was subjected to centrifugation (14000g, 10 min), the pellet and supernatant were analyzed using SDS-PAGE. Proteins were revealed on electrophoretogram, in molecular weight corresponding to the fusion proteins according to the invention, in the membrane fraction of cells. In control plants that did not undergo transformation, the corresponding proteins were not identified. The protein yield was about 12-14% of the fraction of insoluble proteins.
Based on the results obtained, the claimed fusion protein can be obtained using both prokaryotic and eukaryotic cell systems, a highly purified preparation of each protein can be obtained using various types of protein purification. These conditions for isolation and purification were selected experimentally and may vary in values known to the average specialist in this field.
1.4. Obtaining highly purified genetic constructs according to the invention
Nucleotide sequences were obtained according to the method described in paragraph 1.3.2.
1.4.1. Obtaining a plasmid DNA
1.4.1.1. Creating a plasmid DNA producer strain
The synthesized genes were cloned in pVAX1 (Invitrogen), pcDNA3.1+ (Invitrogen) eukaryotic expression vectors at restriction sites flanking the target genes, according to the vector manual. A pcDNA3.1+ vector, incapable of expressing neomycin, was also obtained by exposing this vector to NsiI restriction enzyme in the SV40 promoter region (-71 bp). A pcDNA3.1+ vector, where ampicillin resistance gene had been replaced by kanamycin resistance gene, was also obtained. The obtained fragments were also cloned into the resulting vectors.
3 μl of the synthesized DNA solution, 1 μl of obtained vector solution, 5 μl of buffer for ligation x2 and 1 μl of T4 ligase were taken for the ligation reaction. The reaction was carried out at +20° C for 2 hours.
After this, the mixture was heated at +95°C for 10 min and purified from salts by dialysis on nitrocellulose filters with a pore diameter of 0.025 μm (Millipore, USA). Dialysis was performed against a solution containing 0.5 mM EDTA in 10% glycerol for 10 minutes.
Then E. coli cells of DH10B/R strain (F-mcrA, Δ (mrr-hsdRMS-mcrBC), φ80dlacZΔM 15, ΔlacX74, deoR, recA1, endA1, araD139, Δ (ara, leu) 769, galU, galKλ-, rpsL, nupG) were transformed with the obtained plasmid DNA by electroporation using a MicroPulser electroporator (BioRad). This strain does not contain methylase, which allows to minimize the possibility of mutations occurrence in the DNA, including the gene cloned in the plasmid maintained in this strain. 1 μl of dialyzed ligase mixture was added to 12 μl of competent cells, placed between the electrodes of an electroporation cuvette and processed by a current pulse.
After transformation, the cells were placed in 1 ml of SOC broth (2% bacto-tryptone, 0.5% yeast extract, 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl2, 10 mM MgSO4, 20 mM glucose) and incubated for 40 min at + 37°C.
Clones of E. coli cells containing the obtained plasmid DNA were detected on a selective medium containing LB agar, 50 μg/ml of kanamycin, or ampicillin, based on the resistance gene of a vector.
Plasmid DNA was isolated from the grown clones. Plasmid DNA was isolated using the Wizard Minipreps DNA Purification System kit (Promega, USA). Purified recombinant plasmid DNA was checked by sequencing.
Sequencing of the cloned fragments was performed according to the Sanger method using the Applied Biosystems BigDye® Terminator (BDT) v3.1 Cycle Sequencing Kit (Applied Biosystems, USA) according to the manual attached to it. To label the reaction products, ddNTP labeled with a fluorescent dye were used, with each ddNTP corresponding to its own dye. For sequencing, unlabeled plasmid specific primers were used. A PCR reaction was performed, then the reaction mixture was purified from free labeled ddNTP according to the manual for the BigDye X-Terminator Purification Kit (Applied Biosystems, USA) and the products of the sequencing reaction were separated using an Applied Biosystems 3500 / 3500xL Genetic Analyzer capillary sequencer (Applied Biosystems, USA) and 3500/3500xL Genetic Analyzer Polymer “POP-6 ™” reagent (Applied Biosystems, USA).
The results of the products separation of the sequencing reaction were recorded by laser scanning and detection of four fluorescent dyes included in all types of ddNTP.
Computer analysis of DNA sequences was performed on PC using Chromas and BioEdit programs. The nucleotide sequences of the studied DNA fragments were aligned with the calculated ones, the identity of the synthesized fragments with the calculated ones was demonstrated. As a result, E. coli cell clones were selected containing the full-length sequences of the target genes in the plasmids - DNA sequences encoding the developed fusion proteins. Such clones were used as the producer strain of the plasmids according to the present invention. In one embodiment, this is Escherichia coli DH10B/R bacterial strain, containing the pcDNA3.1(+) vector, which contains the nucleotide sequence of SEQ ID NO:5-8.
Cells of the Bacillus subtilis bacterium have also been successfully used as a producer of the genetic construct.
1.4.1.2. The production of plasmid DNA encoding a fusion protein
A separate colony of E. coli producer cells grown on LB agar in a Petri plate with the addition of kanamycin or ampicillin, depending on the contained plasmid DNA, was placed in 10 ml of selective medium. Cells were grown for 12 hours at + 37°C under constant stirring (250 rpm). The resulting cells were harvested by centrifugation at 4000g. Further isolation and purification of plasmid DNA was carried out using the EndoFree Plasmid Mega Kit (Qiagen), allowing to obtain pyrogen-free DNA. The isolated plasmid DNA was analyzed by electrophoresis in 0.8% agarose gel, and its concentration was measured using fluorimetry. Other methods for plasmid purification, in particular, chromatography, were also used.
The values determined in the experiment corresponded to the values of the ratios A260/A280 and A260/A230 for pure preparations, for all obtained preparations of plasmid DNA.
Protein impurities in the resulting plasmid DNA preparations were also quantified using the microBCA assay [Smith, P.K., et all, Measurement of protein using bicinchoninic acid. Analyt. Biochem. 150, 76-85 (1985)], measuring the optical density of the resulting colored protein complexes with copper and bicinchoninic acid with a wavelength of 562 nm. The sensitivity of the microBCA assay method is 0.5-20 μg/ml of protein. The concentration of total protein in none of the studied plasmid DNA preparations exceeded the norm.
The content of bacterial lipopolysaccharide in plasmid DNA preparations was also determined using a gel-thrombus version of the LAL test with a sensitivity of >0.25 EU/ml (ToxinSensor, GenScript, USA). Limulus polyphemus horseshoe crab amebocytes lysate was used as the LAL reagent. The LAL reagent specifically reacts with bacterial endotoxins; as a result of the enzymatic reaction, the reaction mixture changes in proportion to the concentration of endotoxin. The results were evaluated by the presence or absence of a dense clot at the bottom of the tube by inverting the tube. A gel clot did not form when examining a sample diluted 10 times, for all obtained plasmid DNA preparations, i.e. when the sensitivity of the method is 2.5 EU/ml, which, given the concentration of plasmid DNA in the sample, indicates an acceptable rate of endotoxin removal.
The yield of plasmid DNA ranged from 3.1 mg to 4.7 mg per liter of culture medium. The process took about 4 days.
1.4.2. Obtaining a vector based on adeno-associated virus encoding a fusion protein
The synthesized genes were cloned into a vector based on the pAAVK-EF1α-MCS (System Biosciences (SBI)) adeno-associated virus, on the basis of which a producer strain of this vector was created using E. coli cells (RecA-). Bacillus subtilis bacteria cells were also successfully used as producer.
A vector, further, was isolated for use in mammals, all according to the vector manual. The yield of the vector ranged from 2 mg to 3.2 mg per liter of culture medium.
1.4.3. Obtaining a short linear construct encoding a fusion protein of the invention
To produce a short linear construct, the plasmid DNA obtained according to 2.1.2., or the viral vector of item 2.2., or a fragment amplified from them was used. Using specific primers and PCR, and the DNA specified in the previous sentence as a matrix, the DNA fragment was amplified containing a promoter, an mRNA leader sequence, and also regulatory sequences for these elements, a polynucleotide - a fusion gene, a termination sequence. After amplification the solution may contain also other elements, and the elements indicated in the previous sentence are the key ones.
Amplification of this sequence was carried out in a volume of 50 μl, in 650 μl thin-walled polypropylene tubes containing 5 μl of 10x Taq buffer (700 mM Tris-HCl, pH 8.6/25ºC, 166 mM (NH4)2SO4), 5 μl of MgCl2 (1.25 mM), 1 μl of dNTP, 31.5 μl of water, 1 μl of forward and 1 μl of reverse primers, 5 μl of plasmid DNA and 0.5 μl Taq polymerase (Fermentas, Lithuania).
The reaction mixture was warmed for 5 minutes at 95°C for DNA denaturation. To prevent evaporation, 30 μl of Bayol F mineral oil (Sigma, USA) were layered onto a reaction mixture of 50 μl volume. The amplification reaction was carried out in a C1000 Thermal Cycler (Bio-Rad, USA) thermal cycler. 35 cycles were carried out: 95°С - 20 sec, 50-62°С (depending on the primers) - 20 sec, 72°С - 1 min. To complete the formed DNA chains, an additional cycle was carried out: 5 min at 72°C.
The result of PCR was analyzed by electrophoresis in agarose gel. Upon a positive result, preparative electrophoresis was performed.
Amplified DNA fragments were concentrated and purified using preparative electrophoresis in 0.8-1.2% agarose gel (Gibko BRL, USA). A sample of the mixture after PCR was mixed with 6x buffer (0.25% bromophenol blue, 30% glycerin) (ThermoScientific, USA) and loaded into the gel wells, 18 μl per well. Electrophoresis was carried out in a horizontal apparatus in TAE buffer (40 mM Tris-acetate, 2 mM EDTA pH 8.0, 0.5 μg/ml ethidium bromide) at a voltage of 5-10 V/cm. The result of DNA separation was recorded in transmitted UV light (302 nm) of the Macrovue transilluminator (LKB, Sweden). The length of the amplified fragment was determined by the logarithmic dependence of DNA mobility on the length of the fragments in the marker. As markers, a proprietary mixture of DNA fragments “GeneRuler 1000 bp DNA Ladder” (Fermentas, Lithuania) was used. A plot of agarose containing DNA strip of the required size was excised and the DNA fragment was purified using the DNA & Gel Band Purification Kit (GE Healthcare, UK) according to the manual.
Modern methods of DNA purification, in particular using silicon dioxide, make it possible to get rid of all impurities and to obtain DNA suitable for use in animals and a human. It is also possible to purify the amplified DNA without the use of preparative electrophoresis, using other methods, for example, with chromatography, on a column. Thus, it is possible to obtain a preparation ready for use in 2-3 hours.
Other genetic constructs according to the invention were also obtained, including those containing other components, in addition to the above key ones, as well as other variants of the polynucleotide according to the invention than set forth as SEQ ID NO:5-8, polynucleotide according to the invention is expressed from such constructs in mammalian cells.
The isolated genetic construct was used in mammals.
1.5. Demonstration of the suitability of using a genetic construct to obtain antibodies – of the synthesis of a developed fusion protein from a developed genetic construct in a mammalian body and induction of specific antibodies synthesis
The experiment was conducted on white mice of inbred lines (“Rappolovo” Laboratory animal kennels). Animals weighing 19-22 g were kept under standard conditions, at an ambient temperature of +27±2°C with 55% constant humidity, with a 12-hour daylight. They received dry standardized food and water without restriction.
The animals were injected intramuscularly with pcDNA3.1(+)seqidno7 plasmid DNA in the amount of 50 μg in PBS, animals not injected with any substance were used as a negative control. Animals were sacrificed on days 2, 5, and 7, blood was taken to prepare the serum. Some animals of all groups were not withdrawn from the experiment to assess the safety of the agent.
The obtained serums were analyzed by PAGE followed by transfer of proteins to the nitrocellulose membrane and visualization of the target protein using chemiluminescence.
After PAGE, proteins were transferred to the membrane. The following solutions were used: Solution I - 10 ml of ethanol, 17 ml Tris-HCl 1M pH10.4, up to 50 ml dH2O, Solution II - 10 ml ethanol, 1.25 ml Tris-HCl 1M pH10.4, up to 50 ml dH2O, Solution III - 10 ml of ethanol, 1.25 ml of Tris-HCl 1M pH9.4, up to 50 ml dH2O. A “sandwich” was assembled on a Semi-phor TE70 Semi-dry transfer unit apparatus for horizontal transfer: 6 Whatman papers fragments soaked in Solution I, 3 Whatman papers fragments soaked in Solution II, BioRad nitrocellulose membrane soaked in Solution II, PAGE after electrophoresis, which was located on the membrane and immobilized, 9 fragments of Whatman paper soaked in Solution III. The lid of the device was closed, the power was connected, 100 V for an hour, Constant current PS unit model PS50, Hoefler Scentific Instruments (HSI) was the current source.
Further, the complex immobilized on the membrane was formed: a fusion protein — a specific antibody — a secondary antibody — horseradish peroxidase.
For this, the membrane was treated with 1% dry skim milk in phosphate-buffered saline with the addition of 0.5% Tween-20 (125 μl of a 20% aqueous solution in 50 ml of milk), incubation was carried out for 15 minutes at room temperature. Then the mixture was poured, antibodies were added to the coronavirus proteins - Anti-SARS-CoV-2 spike glycoprotein monoclonal antibody (CABT-RM321) rabbit antibodies to S protein of the coronavirus in 1% skimmed milk at a dilution of 1: 3000, then incubated for 16 hours at +4°C, after which it was heated to room temperature. After that, 3 washes were performed with 1% skimmed milk powder with the addition of 0.5% Tween-20, each for 10 minutes. After the last wash, secondary antibodies conjugated with horseradish peroxidase, - Goat Anti-Rabbit IgG H&L (HRP) (Abcam), - were added in 1% skimmed milk powder, diluted 1: 6000, then incubated for 1 h, after which they were washed 3 times (each for 10 minutes) with phosphate-buffered saline.
The formed membrane-immobilized complexes were developed using the Amersham ECL Western Blotting Detection Reagent (GE Healthcare) chemiluminescence kit. A mixture of equal volumes of 1 and 2 reagents from this kit was applied to a wet membrane with immobilized complexes of a fusion protein with specific antibody with a secondary antibody with horseradish peroxidase, all was packed between layers of a transparent plastic paper folder (slide). This construct was placed in an X-ray cassette (Kodak). Amersham Hyperfilm ECL X-ray film fragment was glued on top and fixed. The cassette was closed and kept for 12 hours. The film was developed using commercial solutions of developer and fixer (Krok-rentgen) according to the manual and dried. These actions were carried out in the dark in the light of a red lamp.
Then, under normal lighting, a picture with the best quality was selected and scanned in parallel with the original membrane, on which molecular weight markers and track markings were located. The resulting images were combined using PhotoFiltre 7.
A similar experiment was performed using antibodies to the coronavirus N protein - Rabbit anti-SARS-CoV-2 NP monoclonal antibody, clone 120 (CABT-RM320).
In both experiments, it was demonstrated that the target gene encoded in pcDNA3.1(+)seqidno7 plasmid DNA is expressed, the maximum expression level being observed on the fifth day after the plasmid DNA injection, and the protein is present after a week, and this protein can bind to antibodies to coronavirus S, N proteins.
Similar results were also demonstrated using other declared genetic constructs, including a linear construct, a viral vector, and using other polynucleotides of the present invention, including with and without a fragment encoding a secretory sequence, and in both variants of the fusion protein, and with both standard and electroporation methods of administration. A higher level of polynucleotide expression and a stronger immune response were demonstrated, as it was shown in earlier studies of the introduction of genetic constructs into a body by electroporation, carried out by the authors of the present invention, for example, described in the article “In vivo production of insulin-like growth factor 1 encoded by plasmid DNA”, Medical Academic Journal, 2017.
Thus, the ability of the developed genetic construct to express the encoded target gene after introduction into the muscles, as well as the functioning of the domains of the developed fusion protein, in particular, represented by the new coronavirus S and N proteins, were evaluated. The synthesis of the fusion protein was demonstrated already on the second day after the introduction of the developed genetic construct carrying the gene encoding it, and within a week, with the maximum level of synthesis being detected on the 5th day after immunization. This suggests that the used genetic construct allows the expression of the target gene in mammalian cells.
Since rabbit antibodies to the S and N proteins of the new coronavirus were used in this analysis, and since it was shown that they bind to the fusion protein of the invention synthesized in mouse cells, it is possible to speak about the full functioning of the S and N domains in the composition of the fusion protein, as well as of the fusion protein synthesized from the developed genetic construct, due to the production in a form recognizable specifically by the immune system. Accordingly, it may be said, that both availability of the protein synthesized from the developed plasmid DNA to be recognized by the immune system and the formation of an adequate immune response have been demonstrated.
Antigenicity and immunogenicity depend on the heterogeneity of the molecules: the more heterogeneous it is, the better it is recognized by the immune system; and also on the size of the molecule - the protein must be more than 10 kDa - and on the degree of foreignness. This may explain the effectiveness of the developed fusion protein.
1.6. Obtaining antibodies for use in a test strip and diagnosticum
The immunization of 3 rabbits at the age of 9 months was carried out with the obtained fusion protein in an amount of 200 μg, concentration 100 μg/ml, in a volume of 2 ml, with complete Freund's adjuvant, adjuvant - 1/10 of the volume of the solution for immunization.
Also, immunization was carried out with the obtained genetic construct in an amount of 250 μg, a concentration of 123 μg/ml, in a volume of 2 ml. Immunization was carried out three times, with an interval of two weeks, subcutaneously in the thigh, blood sampling from the ear vein was carried out two weeks after the third immunization.
Whole blood was collected from all the studied animals in the volume of 200-300 µl from the retroorbital sinus. The blood was incubated in a thermostat at 37° C for 30 minutes, then it was centrifuged for 10 minutes at 2000 g. Serums were taken in a separate test tube without touching the blood clot. To avoid hemolysis, serums were obtained no later than 2 hours after blood sampling. For storage, the test tubes were frozen and left at a temperature of minus 20°C.
The titers of antibodies in the blood serum of the studied animals were measured. The antibody titer of the sera of immunized animals was determined using enzyme-linked immunosorbent assay (ELISA). The results were analyzed using Microsoft Excel.
It was found that the fusion protein obtained by any of the methods described in example 1 caused the formation of a high antibody titer. Also, any genetic construct described and obtained as described in Example 1 caused the formation of a high titer of antibodies. In addition, when the genetic construct was introduced by electroporation, antibody titers were higher. Similar results were obtained using other animals, including mice and a goat.
The Association constant (Ka) of obtained antibodies was also measured by ELISA according to Scatchard. The minimum detected value was1×108 L/mol, and large values were also detected - for example, 5,5×108, 6,8×109, 7,2×109, 8,5×109 L/mol.
The safety of the proposed immunogen was also demonstrated: animals of the corresponding groups survived, no side effects were observed during the tests.
It was also possible to obtain specific antibodies during the immunization of other animals - mice, goats. Such antibodies bind with an affinity of at least 1 × 108 L/mol also.
A system for obtaining antibodies was subsequently chosen - rabbits were immunized with pcDNA3.1 (+) seqidno7 plasmid DNA due to the greater convenience and less labor intensity, as well as similar results on the induction of the antibody response.
1.7. Obtaining a composition containing antibodies to the developed fusion protein for use in diagnostics of SARS-COV-2 presence
2 weeks before blood sampling, the rabbit was boosted - 2 ml of vector with a concentration of 0.123 mg/ml was injected by electroporation or with a concentration of 1 mg/ml by the usual administration. Blood sampling was performed once a month. ~ 25 ml of blood was taken, from which ~ 15 ml of serum was obtained. A composition with antibodies was obtained from the obtained serum, then antibodies were isolated.
Antibodies were isolated from the serum in the following way.
The serums were thawed on ice. 500 μl of PBS was added to 500 μl of serum, centrifuged at 3000g for 15 minutes at +4°C. 820 μl of saturated ammonium sulfate solution was added. The solution was placed on a shaker for 30 minutes in ice, centrifuged at 1000g for 15 minutes at +4°C. The precipitate was washed with 45% ammonium sulfate solution and again centrifuged at 1000g for 15 minutes at + 4°C. The precipitate was dissolved in 1 ml of PBS and centrifuged at 5000 g for 15 minutes at + 4°C. 670 μl of saturated ammonium sulfate solution was added. The solution was placed on a shaker for 30 minutes in ice, centrifuged at 1000g for 15 minutes at + 4°C. The precipitate was dissolved in 500 μl of PBS and dialyzed for 16 h against ~ 5 l of PBS at + 4°С. The solution was centrifuged at 5000g for 15 minutes at + 4°C. The supernatant, a purified solution of antibodies, was placed in a new test tube, and a sample was taken for analysis with PAGE. The main part was frozen.
It was also demonstrated that the fusion protein of the invention, the genetic construct used for its production, and the composition based on antibodies to it can be used in other diagnostic procedures to detect SARS-COV-2. For example, using immunoblot or ELISA to detect antibodies and virus, respectively, but not limited to them.
Example 2. Production and testing of test stripe and express diagnosticum
A test strip was prepared by placing on a strip of hydrophobic material from one edge to another the materials of functional zones - hydrophilic material, hydrophilic material antibody binding value of which is less than 30 μg/cm2, nitrocellulose membrane, hydrophilic material. A variant of the test strip was made, where the materials of the functional zones are located on the hydrophobic material butt-to-butt, as well as a variant - "with overlap". The layout of the functional zones on the test strip is shown in FIG. 1 (A): zone 1, with an overlap on zone 2 or up to it; zone 2, with an overlap on zone 3 or up to it; zone 3, with the edges under zones 2 and 4 or up to them; zone 4, with an overlap on zone 3 or up to it.
Then, the antibody solution obtained by example 1.7 was applied on the corresponding zones. Moreover, for zone 2, such a solution was premixed with a chromatophore – colloidal gold or latex balls and, in one of the variants, any of the sugars was added – to protect against aggregation, for example, mannitol, trehalose or sucrose.
A solution of commercial secondary antibodies was used for 3.2 zone.
Then, drying was carried out to fix the conjugate and antibodies on the test strip - with or without freeze drying. The resulting test strip is shown in FIG. 2.
This test strip was tested – a solution washed off from a saliva sample of a healthy person and a patient with the new coronavirus infection were applied. The state of people was confirmed by the result of PCR diagnostics and additionally by CT for the sick patient. One strip was detected in 3.2 zone of the test strip with a sample of the healthy person, which corresponds to a negative analysis for the new coronavirus, two strips were detected in 3.1. and 3.2 zones on a test strip with a sample of the sick person, which corresponds to a positive test for coronavirus. Interestingly, the same result was obtained when saliva was collected and the zone 1 of the strip was placed at the collected saliva sample, as well as when a drop of saliva was placed directly in zone 1 of the test strip. This indicates the convenience of the test strip for use.
In one embodiment, the resulting test strip was laminated - covered with a material that isolates the zones from the external environment, except for the sample application zone, or partially covers it and leaves a place for the sample application. In this case, the sample was applied not only as indicated above, but also the test strip itself abundantly touched the mucous membrane of the nose and mouth. The results showed that the application of an isolating material that permits to see the test result - 1 or 2 strips, as well as the type of sample application - did not affect the performance, which also allows considering the variant of using such a test strip without any additional objects.
The test strip was also tested using samples of other biological liquids, and the results were also accurate – they corresponded to similar results shown by other test systems.
Meanwhile, when testing test strips on people, a positive result – two strips – was shown in some of people who considered themselves healthy, and who were not diagnosed using other tests. Such people self-isolated themselves and monitored their condition. Several people were subsequently diagnosed with the new coronavirus infection. This means that the developed test strip and the diagnosticum containing it can also detect asymptomatic carriers of infection, as well as the disease in the early stages.
The test strip was placed in a case, preferably a plastic one, while zone 1 was available for applying a sample, partially or completely, 3.1 and 3.2 zones were covered with a transparent film, zones 2 and 4 were covered with a case. In one of the variants, the express diagnostiсum included a plastic spatula or a pipette connected to the case, for collecting saliva and its direct contact with zone 1 of the strip. In another variant, saliva was collected using a device with cotton - cotton bud, cotton swab. Then it touched zone 1. In all variants a reliable result was obtained. Also, when using an additional container with a liquid to dissolve the sample - for example, 0.9% NaCl or 0.9% NaCl in phosphate buffer, but not limited to them, a sample taken by device for taking a sample from the mouth and/or nasopharynx was dissolved and applied to zone 1. In one embodiment, the container with the liquid had a conic form, and after placing and stirring the sample or device with the sample, its tip was cut off and the contents were squeezed out dropwise onto zone 1 of the test strip. In the case of a single device, also with the sample dissolution liquid, actions were taken after sampling to promote mixing of the liquid and the sample, while the liquid did not enter the mouth and nose.
When examining other biological liquids by this express diagnosticum, the results were correct and reliable.
It should be noted that the sensitivity of the test strip and express diagnosticum is high and detects the virus if it is present in quantities of 103.
Thus, the proposed group of inventions can be successfully used in the diagnosis of infection caused by SARS-COV-2.
<110> SIA TERRAGEN
<120> Express diagnosticum for SARS-COV-2
<160> 8
<210> SEQ ID NO: 1
<211> 422
<212> PRT
<213> Artificial sequence
<220>
<221> domain
<222> from 1 to 121 amino acid residue
<223> M domain, from 60 to 180 amino acid residues of M protein of the new coronavirus
<220>
<221> domain
<222> from 128 to 202 amino acid residue
<223> S domain, from 306 to 380 amino acid residues of S protein of the new coronavirus
<220>
<221> domain
<222> from 208 to 352 amino acid residue
<223> N domain, from 216 to 360 amino acid residues of N protein of the new coronavirus
<220>
<221> domain
<222> from 358 to 422 amino acid residue
<223> E domain, from 6 to 70 amino acid residues of E protein of the new coronavirus
<400> 1
Val Thr Leu Ala Cys Phe Val Leu Ala Ala Val Tyr Arg Ile Asn Trp
1 5 10 15
Ile Thr Gly Gly Ile Ala Ile Ala Met Ala Cys Leu Val Gly Leu Met
20 25 30
Trp Leu Ser Tyr Phe Ile Ala Ser Phe Arg Leu Phe Ala Arg Thr Arg
35 40 45
Ser Met Trp Ser Phe Asn Pro Glu Thr Asn Ile Leu Leu Asn Val Pro
50 55 60
Leu His Gly Thr Ile Leu Thr Arg Pro Leu Leu Glu Ser Glu Leu Val
65 70 75 80
Ile Gly Ala Val Ile Leu Arg Gly His Leu Arg Ile Ala Gly His His
85 90 95
Leu Gly Arg Cys Asp Ile Lys Asp Leu Pro Lys Glu Ile Thr Val Ala
100 105 110
Thr Ser Arg Thr Leu Ser Tyr Tyr Lys Gly Gly Gly Gly Gly Gly Phe
115 120 125
Thr Val Glu Lys Gly Ile Tyr Gln Thr Ser Asn Phe Arg Val Gln Pro
130 135 140
Thr Glu Ser Ile Val Arg Phe Pro Asn Ile Thr Asn Leu Cys Pro Phe
145 150 155 160
Gly Glu Val Phe Asn Ala Thr Arg Phe Ala Ser Val Tyr Ala Trp Asn
165 170 175
Arg Lys Arg Ile Ser Asn Cys Val Ala Asp Tyr Ser Val Leu Tyr Asn
180 185 190
Ser Ala Ser Phe Ser Thr Phe Lys Cys Tyr Gly Gly Gly Gly Gly Asp
195 200 205
Ala Ala Leu Ala Leu Leu Leu Leu Asp Arg Leu Asn Gln Leu Glu Ser
210 215 220
Lys Met Ser Gly Lys Gly Gln Gln Gln Gln Gly Gln Thr Val Thr Lys
225 230 235 240
Lys Ser Ala Ala Glu Ala Ser Lys Lys Pro Arg Gln Lys Arg Thr Ala
245 250 255
Thr Lys Ala Tyr Asn Val Thr Gln Ala Phe Gly Arg Arg Gly Pro Glu
260 265 270
Gln Thr Gln Gly Asn Phe Gly Asp Gln Glu Leu Ile Arg Gln Gly Thr
275 280 285
Asp Tyr Lys His Trp Pro Gln Ile Ala Gln Phe Ala Pro Ser Ala Ser
290 295 300
Ala Phe Phe Gly Met Ser Arg Ile Gly Met Glu Val Thr Pro Ser Gly
305 310 315 320
Thr Trp Leu Thr Tyr Thr Gly Ala Ile Lys Leu Asp Asp Lys Asp Pro
325 330 335
Asn Phe Lys Asp Gln Val Ile Leu Leu Asn Lys His Ile Asp Ala Tyr
340 345 350
Gly Gly Gly Gly Gly Ser Glu Glu Thr Gly Thr Leu Ile Val Asn Ser
355 360 365
Val Leu Leu Phe Leu Ala Phe Val Val Phe Leu Leu Val Thr Leu Ala
370 375 380
Ile Leu Thr Ala Leu Arg Leu Cys Ala Tyr Cys Cys Asn Ile Val Asn
385 390 395 400
Val Ser Leu Val Lys Pro Ser Phe Tyr Val Tyr Ser Arg Val Lys Asn
405 410 415
Leu Asn Ser Ser Arg Val
420
<210> SEQ ID NO: 2
<211> 424
<212> PRT
<213> Artificial sequence
<220>
<221> domain
<222> from 1 to 121 amino acid residue
<223> M domain, from 60 to 180 amino acid residue of M protein of the new coronavirus
<220>
<221> domain
<222> from 128 to 202 amino acid residue
<223> S domain, from 306 to 380 amino acid residues of S protein of the new coronavirus
<220>
<221> domain
<222> from 209 to 353 amino acid residue
<223> N domain, from 216 to 360 amino acid residue of N protein of the new coronavirus
<220>
<221> domain
<222> from 360 to 424 amino acid residue
<223> E domain, from 6 to 70 amino acid residue of E protein of the new coronavirus
<400> 2
Val Thr Leu Ala Cys Phe Val Leu Ala Ala Val Tyr Arg Ile Asn Trp
1 5 10 15
Ile Thr Gly Gly Ile Ala Ile Ala Met Ala Cys Leu Val Gly Leu Met
20 25 30
Trp Leu Ser Tyr Phe Ile Ala Ser Phe Arg Leu Phe Ala Arg Thr Arg
35 40 45
Ser Met Trp Ser Phe Asn Pro Glu Thr Asn Ile Leu Leu Asn Val Pro
50 55 60
Leu His Gly Thr Ile Leu Thr Arg Pro Leu Leu Glu Ser Glu Leu Val
65 70 75 80
Ile Gly Ala Val Ile Leu Arg Gly His Leu Arg Ile Ala Gly His His
85 90 95
Leu Gly Arg Cys Asp Ile Lys Asp Leu Pro Lys Glu Ile Thr Val Ala
100 105 110
Thr Ser Arg Thr Leu Ser Tyr Tyr Lys Gly Gly Gly Gly Gly Gly Phe
115 120 125
Thr Val Glu Lys Gly Ile Tyr Gln Thr Ser Asn Phe Arg Val Gln Pro
130 135 140
Thr Glu Ser Ile Val Arg Phe Pro Asn Ile Thr Asn Leu Cys Pro Phe
145 150 155 160
Gly Glu Val Phe Asn Ala Thr Arg Phe Ala Ser Val Tyr Ala Trp Asn
165 170 175
Arg Lys Arg Ile Ser Asn Cys Val Ala Asp Tyr Ser Val Leu Tyr Asn
180 185 190
Ser Ala Ser Phe Ser Thr Phe Lys Cys Tyr Gly Gly Gly Gly Gly Gly
195 200 205
Asp Ala Ala Leu Ala Leu Leu Leu Leu Asp Arg Leu Asn Gln Leu Glu
210 215 220
Ser Lys Met Ser Gly Lys Gly Gln Gln Gln Gln Gly Gln Thr Val Thr
225 230 235 240
Lys Lys Ser Ala Ala Glu Ala Ser Lys Lys Pro Arg Gln Lys Arg Thr
245 250 255
Ala Thr Lys Ala Tyr Asn Val Thr Gln Ala Phe Gly Arg Arg Gly Pro
260 265 270
Glu Gln Thr Gln Gly Asn Phe Gly Asp Gln Glu Leu Ile Arg Gln Gly
275 280 285
Thr Asp Tyr Lys His Trp Pro Gln Ile Ala Gln Phe Ala Pro Ser Ala
290 295 300
Ser Ala Phe Phe Gly Met Ser Arg Ile Gly Met Glu Val Thr Pro Ser
305 310 315 320
Gly Thr Trp Leu Thr Tyr Thr Gly Ala Ile Lys Leu Asp Asp Lys Asp
325 330 335
Pro Asn Phe Lys Asp Gln Val Ile Leu Leu Asn Lys His Ile Asp Ala
340 345 350
Tyr Gly Gly Gly Gly Gly Gly Ser Glu Glu Thr Gly Thr Leu Ile Val
355 360 365
Asn Ser Val Leu Leu Phe Leu Ala Phe Val Val Phe Leu Leu Val Thr
370 375 380
Leu Ala Ile Leu Thr Ala Leu Arg Leu Cys Ala Tyr Cys Cys Asn Ile
385 390 395 400
Val Asn Val Ser Leu Val Lys Pro Ser Phe Tyr Val Tyr Ser Arg Val
405 410 415
Lys Asn Leu Asn Ser Ser Arg Val
420
<210> SEQ ID NO: 3
<211> 1272
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide codon-optimized for E. coli encoding a fusion protein of 422 aa
<400> 3
atggtgaccc tggcgtgctt tgtgctggcg gcggtgtatc gtattaattg gattaccggc 60
ggcattgcga ttgcgatggc gtgcctggtg ggcctgatgt ggctgtccta ttttattgcg 120
tcctttcgtc tgtttgcgcg tacccgttcc atgtggtcct ttaatccgga aaccaatatt 180
ctgctgaatg tgccgctgca tggcaccatt ctgacccgtc cgctgctgga atccgaactg 240
gtgattggcg cggtgattct gcgtggccat ctgcgtattg cgggccatca tctgggccgt 300
tgcgatatta aagatctgcc gaaagaaatt accgtggcga cctcccgtac cctgtcctat 360
tataaaggcg gcggcggcgg cggctttacc gtggaaaaag gcatttatca gacctccaat 420
tttcgtgtgc agccgaccga atccattgtg cgttttccga atattaccaa tctgtgcccg 480
tttggcgaag tgtttaatgc gacccgtttt gcgtccgtgt atgcgtggaa tcgtaaacgt 540
atttccaatt gcgtggcgga ttattccgtg ctgtataatt ccgcgtcctt ttccaccttt 600
aaatgctatg gcggcggcgg cggcgatgcg gcgctggcgc tgctgctgct ggatcgtctg 660
aatcagctgg aatccaaaat gtccggcaaa ggccagcagc agcagggcca gaccgtgacc 720
aaaaaatccg cggcggaagc gtccaaaaaa ccgcgtcaga aacgtaccgc gaccaaagcg 780
tataatgtga cccaggcgtt tggccgtcgt ggcccggaac agacccaggg caattttggc 840
gatcaggaac tgattcgtca gggcaccgat tataaacatt ggccgcagat tgcgcagttt 900
gcgccgtccg cgtccgcgtt ttttggcatg tcccgtattg gcatggaagt gaccccgtcc 960
ggcacctggc tgacctatac cggcgcgatt aaactggatg ataaagatcc gaattttaaa 1020
gatcaggtga ttctgctgaa taaacatatt gatgcgtatg gcggcggcgg cggctccgaa 1080
gaaaccggca ccctgattgt gaattccgtg ctgctgtttc tggcgtttgt ggtgtttctg 1140
ctggtgaccc tggcgattct gaccgcgctg cgtctgtgcg cgtattgctg caatattgtg 1200
aatgtgtccc tggtgaaacc gtccttttat gtgtattccc gtgtgaaaaa tctgaattcc 1260
tcccgtgtgt aa 1272
<210> SEQ ID NO: 4
<211> 1278
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide codon-optimized for E. coli encoding a fusion protein of 424 аa
<400> 4
atggtgaccc tggcgtgctt tgtgctggcg gcggtgtatc gtattaattg gattaccggc 60
ggcattgcga ttgcgatggc gtgcctggtg ggcctgatgt ggctgtccta ttttattgcg 120
tcctttcgtc tgtttgcgcg tacccgttcc atgtggtcct ttaatccgga aaccaatatt 180
ctgctgaatg tgccgctgca tggcaccatt ctgacccgtc cgctgctgga atccgaactg 240
gtgattggcg cggtgattct gcgtggccat ctgcgtattg cgggccatca tctgggccgt 300
tgcgatatta aagatctgcc gaaagaaatt accgtggcga cctcccgtac cctgtcctat 360
tataaaggcg gcggcggcgg cggctttacc gtggaaaaag gcatttatca gacctccaat 420
tttcgtgtgc agccgaccga atccattgtg cgttttccga atattaccaa tctgtgcccg 480
tttggcgaag tgtttaatgc gacccgtttt gcgtccgtgt atgcgtggaa tcgtaaacgt 540
atttccaatt gcgtggcgga ttattccgtg ctgtataatt ccgcgtcctt ttccaccttt 600
aaatgctatg gcggcggcgg cggcggcgat gcggcgctgg cgctgctgct gctggatcgt 660
ctgaatcagc tggaatccaa aatgtccggc aaaggccagc agcagcaggg ccagaccgtg 720
accaaaaaat ccgcggcgga agcgtccaaa aaaccgcgtc agaaacgtac cgcgaccaaa 780
gcgtataatg tgacccaggc gtttggccgt cgtggcccgg aacagaccca gggcaatttt 840
ggcgatcagg aactgattcg tcagggcacc gattataaac attggccgca gattgcgcag 900
tttgcgccgt ccgcgtccgc gttttttggc atgtcccgta ttggcatgga agtgaccccg 960
tccggcacct ggctgaccta taccggcgcg attaaactgg atgataaaga tccgaatttt 1020
aaagatcagg tgattctgct gaataaacat attgatgcgt atggcggcgg cggcggcggc 1080
tccgaagaaa ccggcaccct gattgtgaat tccgtgctgc tgtttctggc gtttgtggtg 1140
tttctgctgg tgaccctggc gattctgacc gcgctgcgtc tgtgcgcgta ttgctgcaat 1200
attgtgaatg tgtccctggt gaaaccgtcc ttttatgtgt attcccgtgt gaaaaatctg 1260
aattcctccc gtgtgtga 1278
<210> SEQ ID NO: 5
<211> 1281
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide codon-optimized for mammals encoding a fusion protein of 422 aa
<400> 5
gccgccacca tggtgaccct ggcctgcttc gtgctggccg ccgtgtaccg gatcaactgg 60
atcaccggcg gcatcgccat cgccatggcc tgcctggtgg gcctgatgtg gctgtcctac 120
ttcatcgcct ccttccggct gttcgcccgg acccggtcca tgtggtcctt caaccccgag 180
accaacatcc tgctgaacgt gcccctgcac ggcaccatcc tgacccggcc cctgctggag 240
tccgagctgg tgatcggcgc cgtgatcctg cggggccacc tgcggatcgc cggccaccac 300
ctgggccggt gcgacatcaa ggacctgccc aaggagatca ccgtggccac ctcccggacc 360
ctgtcctact acaagggcgg cggcggcggc ggcttcaccg tggagaaggg catctaccag 420
acctccaact tccgggtgca gcccaccgag tccatcgtgc ggttccccaa catcaccaac 480
ctgtgcccct tcggcgaggt gttcaacgcc acccggttcg cctccgtgta cgcctggaac 540
cggaagcgga tctccaactg cgtggccgac tactccgtgc tgtacaactc cgcctccttc 600
tccaccttca agtgctacgg cggcggcggc ggcgacgccg ccctggccct gctgctgctg 660
gaccggctga accagctgga gtccaagatg tccggcaagg gccagcagca gcagggccag 720
accgtgacca agaagtccgc cgccgaggcc tccaagaagc cccggcagaa gcggaccgcc 780
accaaggcct acaacgtgac ccaggccttc ggccggcggg gccccgagca gacccagggc 840
aacttcggcg accaggagct gatccggcag ggcaccgact acaagcactg gccccagatc 900
gcccagttcg ccccctccgc ctccgccttc ttcggcatgt cccggatcgg catggaggtg 960
accccctccg gcacctggct gacctacacc ggcgccatca agctggacga caaggacccc 1020
aacttcaagg accaggtgat cctgctgaac aagcacatcg acgcctacgg cggcggcggc 1080
ggctccgagg agaccggcac cctgatcgtg aactccgtgc tgctgttcct ggccttcgtg 1140
gtgttcctgc tggtgaccct ggccatcctg accgccctgc ggctgtgcgc ctactgctgc 1200
aacatcgtga acgtgtccct ggtgaagccc tccttctacg tgtactcccg ggtgaagaac 1260
ctgaactcct cccgggtgtg a 1281
<210> SEQ ID NO: 6
<211> 1287
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide codon-optimized for mammals encoding a fusion protein of 424 aa
<400> 6
gccgccacca tggtgaccct ggcctgcttc gtgctggccg ccgtgtaccg gatcaactgg 60
atcaccggcg gcatcgccat cgccatggcc tgcctggtgg gcctgatgtg gctgtcctac 120
ttcatcgcct ccttccggct gttcgcccgg acccggtcca tgtggtcctt caaccccgag 180
accaacatcc tgctgaacgt gcccctgcac ggcaccatcc tgacccggcc cctgctggag 240
tccgagctgg tgatcggcgc cgtgatcctg cggggccacc tgcggatcgc cggccaccac 300
ctgggccggt gcgacatcaa ggacctgccc aaggagatca ccgtggccac ctcccggacc 360
ctgtcctact acaagggcgg cggcggcggc ggcttcaccg tggagaaggg catctaccag 420
acctccaact tccgggtgca gcccaccgag tccatcgtgc ggttccccaa catcaccaac 480
ctgtgcccct tcggcgaggt gttcaacgcc acccggttcg cctccgtgta cgcctggaac 540
cggaagcgga tctccaactg cgtggccgac tactccgtgc tgtacaactc cgcctccttc 600
tccaccttca agtgctacgg cggcggcggc ggcggcgacg ccgccctggc cctgctgctg 660
ctggaccggc tgaaccagct ggagtccaag atgtccggca agggccagca gcagcagggc 720
cagaccgtga ccaagaagtc cgccgccgag gcctccaaga agccccggca gaagcggacc 780
gccaccaagg cctacaacgt gacccaggcc ttcggccggc ggggccccga gcagacccag 840
ggcaacttcg gcgaccagga gctgatccgg cagggcaccg actacaagca ctggccccag 900
atcgcccagt tcgccccctc cgcctccgcc ttcttcggca tgtcccggat cggcatggag 960
gtgaccccct ccggcacctg gctgacctac accggcgcca tcaagctgga cgacaaggac 1020
cccaacttca aggaccaggt gatcctgctg aacaagcaca tcgacgccta cggcggcggc 1080
ggcggcggct ccgaggagac cggcaccctg atcgtgaact ccgtgctgct gttcctggcc 1140
ttcgtggtgt tcctgctggt gaccctggcc atcctgaccg ccctgcggct gtgcgcctac 1200
tgctgcaaca tcgtgaacgt gtccctggtg aagccctcct tctacgtgta ctcccgggtg 1260
aagaacctga actcctcccg ggtgtga 1287
<210> SEQ ID NO: 7
<211> 1350
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide based on viral seq-s encoding a fusion protein of 424 aa with the addition of IGF secretory seq.
<400> 7
gccgccacca tgggcaagat cagcagcctg cccacccagc tgttcaagtg ctgcttctgc 60
gacttcctga aggtaacttt agcttgtttt gtgcttgctg ctgtttacag aataaattgg 120
atcaccggtg gaattgctat cgcaatggct tgtcttgtag gcttgatgtg gctcagctac 180
ttcattgctt ctttcagact gtttgcgcgt acgcgttcca tgtggtcatt caatccagaa 240
actaacattc ttctcaacgt gccactccat ggcactattc tgaccagacc gcttctagaa 300
agtgaactcg taatcggagc tgtgatcctt cgtggacatc ttcgtattgc tggacaccat 360
ctaggacgct gtgacatcaa ggacctgcct aaagaaatca ctgttgctac atcacgaacg 420
ctttcttatt acaaaggagg aggaggagga ggattcactg tagaaaaagg aatctatcaa 480
acttctaact ttagagtcca accaacagaa tctattgtta gatttcctaa tattacaaac 540
ttgtgccctt ttggtgaagt ttttaacgcc accagatttg catctgttta tgcttggaac 600
aggaagagaa tcagcaactg tgttgctgat tattctgtcc tatataattc cgcatcattt 660
tccactttta agtgttatgg aggaggagga ggaggagatg ctgctcttgc tttgctgctg 720
cttgacagat tgaaccagct tgagagcaaa atgtctggta aaggccaaca acaacaaggc 780
caaactgtca ctaagaaatc tgctgctgag gcttctaaga agcctcggca aaaacgtact 840
gccactaaag catacaatgt aacacaagct ttcggcagac gtggtccaga acaaacccaa 900
ggaaattttg gggaccagga actaatcaga caaggaactg attacaaaca ttggccgcaa 960
attgcacaat ttgcccccag cgcttcagcg ttcttcggaa tgtcgcgcat tggcatggaa 1020
gtcacacctt cgggaacgtg gttgacctac acaggtgcca tcaaattgga tgacaaagat 1080
ccaaatttca aagatcaagt cattttgctg aataagcata ttgacgcata cggaggagga 1140
ggaggaggat cggaagagac aggtacgtta atagttaata gcgtacttct ttttcttgct 1200
ttcgtggtat tcttgctagt tacactagcc atccttactg cgcttcgatt gtgtgcgtac 1260
tgctgcaata ttgttaacgt gagtcttgta aaaccttctt tttacgttta ctctcgtgtt 1320
aaaaatctga attcttctag agtttaatga 1350
<210> SEQ ID NO: 8
<211> 1356
<212> DNA
<213> Artificial sequence
<220>
<223> polynucleotide codon-optimized for mammals encoding a fusion protein of 422 aa with the addition of HGH secretory seq.
<400> 8
gccgccacca tggccaccgg ctcccggacc tccctgctgc tggccttcgg cctgctgtgc 60
ctgccctggc tgcaggaggg ctccgccgtg accctggcct gcttcgtgct ggccgccgtg 120
taccggatca actggatcac cggcggcatc gccatcgcca tggcctgcct ggtgggcctg 180
atgtggctgt cctacttcat cgcctccttc cggctgttcg cccggacccg gtccatgtgg 240
tccttcaacc ccgagaccaa catcctgctg aacgtgcccc tgcacggcac catcctgacc 300
cggcccctgc tggagtccga gctggtgatc ggcgccgtga tcctgcgggg ccacctgcgg 360
atcgccggcc accacctggg ccggtgcgac atcaaggacc tgcccaagga gatcaccgtg 420
gccacctccc ggaccctgtc ctactacaag ggcggcggcg gcggcggctt caccgtggag 480
aagggcatct accagacctc caacttccgg gtgcagccca ccgagtccat cgtgcggttc 540
cccaacatca ccaacctgtg ccccttcggc gaggtgttca acgccacccg gttcgcctcc 600
gtgtacgcct ggaaccggaa gcggatctcc aactgcgtgg ccgactactc cgtgctgtac 660
aactccgcct ccttctccac cttcaagtgc tacggcggcg gcggcggcga cgccgccctg 720
gccctgctgc tgctggaccg gctgaaccag ctggagtcca agatgtccgg caagggccag 780
cagcagcagg gccagaccgt gaccaagaag tccgccgccg aggcctccaa gaagccccgg 840
cagaagcgga ccgccaccaa ggcctacaac gtgacccagg ccttcggccg gcggggcccc 900
gagcagaccc agggcaactt cggcgaccag gagctgatcc ggcagggcac cgactacaag 960
cactggcccc agatcgccca gttcgccccc tccgcctccg ccttcttcgg catgtcccgg 1020
atcggcatgg aggtgacccc ctccggcacc tggctgacct acaccggcgc catcaagctg 1080
gacgacaagg accccaactt caaggaccag gtgatcctgc tgaacaagca catcgacgcc 1140
tacggcggcg gcggcggctc cgaggagacc ggcaccctga tcgtgaactc cgtgctgctg 1200
ttcctggcct tcgtggtgtt cctgctggtg accctggcca tcctgaccgc cctgcggctg 1260
tgcgcctact gctgcaacat cgtgaacgtg tccctggtga agccctcctt ctacgtgtac 1320
tcccgggtga agaacctgaa ctcctcccgg gtgtga 1356

Claims (28)

  1. A fusion protein for use in the diagnostics of infection caused by SARS-COV-2 set forth as SEQ ID NO:1 or SEQ ID NO:2 amino acid sequence comprising fragments of M, S, N, E proteins of such coronavirus connected by flexible bridges.
  2. A genetic construct for use in the diagnostics of infection caused by SARS-COV-2, comprising a polynucleotide encoding the fusion protein of claim 1 and other elements providing synthesis of fusion protein of claim 1 in a producer organism.
  3. The genetic construct of claim 2, providing for the synthesis of the fusion protein of claim 1 in an eukaryotic producer organism, wherein it also contains a fragment encoding a heterologous secretory sequence.
  4. The genetic construct of claim 3, wherein the heterologous secretory sequence is from that of TPA, EPO, hGH or IGF.
  5. An animal antibody that specifically binds to the fusion protein of claim 1 for use in diagnosing the presence of SARS-COV-2.
  6. The antibody of claim 5, wherein it is obtained as a result of the introduction to an animal of the fusion protein of claim 1 or the genetic construct of any one of claims 2 to 4.
  7. The antibody of claim 6, wherein it binds to a fragment of SARS-COV-2 M protein from 60 to 180 amino acid residue, and/or S protein from 306 to 380 amino acid residue, and/or N protein from 216 to 360 amino acid residue and/or E protein from 6 to 70 amino acid residue.
  8. The antibody of claim 7, wherein it binds with an affinity of at least 1×108 l/mol, measured as an Association constant (Ka), as determined by the Scatchard analysis.
  9. The antibody of any one of claims 7 or 8, wherein it is a rabbit antibody.
  10. The antibody of any one of claims 5 to 8, wherein it is an active agent of a test strip for diagnosing the presence of SARS-COV-2.
  11. A composition comprising the antibody of any one of claims 5 to 9 in an effective amount for use in diagnosing the presence of SARS-COV-2.
  12. Composition of claim 11, wherein it is obtained as a result of the administration to an animal of the fusion protein of claim 1 or the genetic construct of any one of claims 2 to 4, blood sampling, isolation of antibodies of any one of claims 5 to 9 from it and mixing with the target additive.
  13. A test strip for diagnosing the presence of SARS-COV-2, containing a strip of a hydrophobic material, on which the following zones are sequentially located: a sample application zone, represented by a hydrophilic material, a conjugation zone, represented by a hydrophilic material, the antibody binding value of which is less than 30 μg/cm2 and which contains complexes of antibody or antibodies according to any one of claims 5-10 with a chromatophore particle, a precipitation zone represented by a nitrocellulose membrane containing a region with an immobilized antibody or antibodies according to any one of claims 5-10, then a region with immobilized secondary antibodies to antibodies according to any one of claims 5-10, a zone of the capillary pump, represented by a hydrophilic material.
  14. The test strip of claim 13, further comprising a coating that isolates the conjugation, precipitation, capillary pump zones from the external environment.
  15. The test strip of claim 14, wherein the coating also isolates a part of the sample application zone.
  16. The test strip of claim 13, wherein the hydrophilic material of the sample application zone is a chromatographic paper, not less than 1 layer.
  17. The test strip of claim 13, wherein the hydrophilic conjugation zone material is cellulose acetate.
  18. The test strip of claim 13, wherein the chromatophore is a colloidal gold or colored latex beads.
  19. The test strip of claim 13, wherein the amount of antibodies immobilized on the membrane is less than of the antibody-chromatophore complexes.
  20. The test strip of claim 13, wherein the secondary antibodies are goat antibodies to rabbit antibodies.
  21. The test strip of any one of claims 13 to 20, wherein during its production, the complex of antibody or antibodies of any one of claims 5 to 9 with chromatophore particles is applied to the conjugation zone, as well as the antibody or antibodies of any one of claims 5 to 9, as a part of the composition of claim 11, is applied to the first region of the precipitation zone, and secondary antibodies to antibodies according to any one of claims 5-9 are applied to the second region of the precipitation zone.
  22. The test strip of claim 21, wherein a freeze drying is performed after applying the complex of the antibody or antibodies of any one of claims 5 to 9 with the chromatophore particles.
  23. An express diagnosticum for SARS-COV-2, comprising the test strip of any one of claims 13 to 22 enclosed in a case and a device for taking a sample.
  24. The express diagnosticum of claim 23, wherein the device for taking a sample is a cotton swab, a cotton bud, a spatula or a pipette.
  25. The express diagnosticum of claim 24, wherein the sample is a saliva.
  26. The express diagnosticum of claim 23, additionally comprising a container with a liquid for dissolving the sample.
  27. The express diagnosticum of claim 26, wherein the liquid is 0.9% NaCl or 0.9% NaCl in phosphate buffer.
  28. The express diagnosticum of any one of claims 23 to 27, represented by a kit or a single device.
PCT/IB2020/058162 2020-09-02 2020-09-02 Express diagnosticum for sars-cov-2 WO2022049409A1 (en)

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CN116574195A (en) * 2023-07-07 2023-08-11 北京市疾病预防控制中心 Novel coronavirus antibody and application thereof in detection of oral liquid without transmission risk
CN116574195B (en) * 2023-07-07 2023-09-29 北京市疾病预防控制中心 Novel coronavirus antibody and application thereof in detection of oral liquid without transmission risk

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