CN111549064A

CN111549064A - Method for preparing transgenic non-human animal capable of expressing human ACE2 by using adenovirus transduction, and application of obtained animal

Info

Publication number: CN111549064A
Application number: CN202010249813.XA
Authority: CN
Inventors: 赵金存; 孙静; 刘冬兰; 陈春可; 庄珍; 朱爱如; 肇静娴; 陈钊; 张昭勇; 陈锭彬; 黄小芳; 王俊翔; 赖小敏; 李芳�; 文李艳; 卓健芬; 张艳君
Original assignee: First Affiliated Hospital of Guangzhou Medical University
Current assignee: First Affiliated Hospital of Guangzhou Medical University
Priority date: 2020-04-01
Filing date: 2020-04-01
Publication date: 2020-08-18

Abstract

The invention relates to the field of animal models, in particular to a method for preparing a transgenic non-human animal capable of expressing human ACE2 by adenovirus transduction and application of the animal. Wherein the adenovirus is rescued in AD293 cells by a recombinant vector obtained by recombining pShuttle-hACE2 and pAdEasy-1, and the pShuttle-hACE2 is pShuttle inserted with the DNA sequence of the human ACE 2; after the adenovirus is transduced into the animal, respiratory tract cells of the animal express human ACE2 protein. The method has the advantages of rapidness, easy obtaining and preparation and the like.

Description

Method for preparing transgenic non-human animal capable of expressing human ACE2 by using adenovirus transduction, and application of obtained animal

Technical Field

The invention relates to the field of animal models, in particular to a method for preparing a transgenic non-human animal capable of expressing human ACE2 by adenovirus transduction and application of the animal.

Background

Human coronavirus infection can cause mild to severe respiratory diseases. Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) and Middle East Respiratory Syndrome coronavirus (MERS-CoV) are two highly pathogenic coronaviruses. The SARS-CoV-2 and SARS-CoV have 79.5% homology, strong infectivity and lower fatality rate than SARS-CoV. Animal models are essential for the study of pathogenic mechanisms, the evaluation of vaccines and antiviral drugs.

Coronaviruses widely infect mammals and birds, their tropism depends primarily on the binding of Spike (S) proteins to cell surface receptors, and thus receptor distribution determines the host range and cross-species infection of the virus. Some coronaviruses employ cell surface enzymes as receptors, such as 229E using aminopeptidase N (APN) as a receptor, SARS-CoV, NL63 and SARS-CoV-2 using angiotensin-converting enzyme 2(angiotensin-converting enzyme2, ACE2) as a receptor, and MRES-CoV using dipeptidyl peptidase 4 (DPP 4) as a receptor. The first MERS mouse model was successfully developed by using adenovirus-transduced mice expressing human hDPP4 to construct MERS-CoV animal models in the earlier stage of Zhao et al, the applicant company showed that the method is rapid and effective in constructing animal models.

However, there is no animal model for SARS-CoV-2 infected mice with short operation cycle and simple operation, which hinders the research on this new virus.

Disclosure of Invention

The invention relates to a method for preparing a non-human animal capable of expressing human ACE2 transgene by using adenovirus transduction, wherein the adenovirus is rescued in AD293 cells by a recombinant vector obtained by recombining pShuttle-hACE2 and pAdEasy-1, and the pShuttle-hACE2 is pShuttle inserted with a DNA sequence of the human ACE 2;

after the adenovirus is transduced into the animal, respiratory tract cells of the animal express human ACE2 protein.

According to a further aspect of the invention, the invention also relates to the use of the transgenic non-human animals obtained according to the method as described above for the construction of a SARS-CoV-2 infectious disease model.

The invention utilizes a pAdEasy system to recombine SARS-CoV-2 receptor gene humanized ACE2 to a 5-type adenovirus vector, and rescues Ad5-ACE2 recombinant adenovirus in AD293 cells, thereby transducing the adenovirus into a non-human animal, leading the respiratory tract, particularly the lung, to express human ACE2 receptor, and then carrying out virus infection. The SARS-CoV-2 infected mouse animal model can be widely applied to vaccine and therapeutic drug evaluation and pathogenic mechanism research. The method has the advantages of rapidness, easy obtaining and preparation and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 shows the restriction enzyme digestion identification results of the recombinant adenovirus plasmids Ad5-hACE2 and Ad5-Empty successfully constructed by the pAdEasy system in one embodiment of the present invention;

FIG. 2 shows the results of Ad5-hACE2 and Ad5-Empty for CsCl-purified adenoviruses according to an embodiment of the present invention;

FIG. 3 shows the identification of hACE2 expression in vitro in one embodiment of the present invention;

FIG. 4 shows the results of immunohistochemical characterization of ACE2 expression in mouse lung according to one embodiment of the present invention;

FIG. 5 is a graph showing the replication of the novel coronavirus in the lungs after infection in a model mouse according to one embodiment of the present invention;

statistical difference analysis used the values of upaired t test, P < 0.05 as the criteria for statistically significant differences between groups, P < 0.0332(, P < 0.0021(, P < 0.0002(, P), P < 0.0001(, P).

Detailed Description

Reference will now be made in detail to embodiments of the invention, one or more examples of which are described below. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment.

It is therefore intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are apparent from the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.

The method for constructing the mouse model by transduction of the adenovirus expressing the humanized ACE2 is faster and easier to operate, can fight against virus 5 days after transduction, can quickly construct the mouse model when a new outbreak respiratory infectious disease is outbreaked, and is beneficial to emergency in-vivo verification of antiviral drugs, protective neutralizing antibodies and vaccines and research on in-vivo immune response and pathogenic mechanisms.

In the present invention, the term "respiratory tract" may include the following three parts:

upper respiratory tract: nose, nasal passages, sinuses, larynx and pharynx.

Trachea: laryngeal prominences, trachea, bronchi, and secondary bronchi.

Lung: bronchioles, alveolar ducts and alveoli.

The term "transgene" as used herein describes genetic material that is artificially inserted into the genome of a cell, particularly a mammalian cell, for implantation into a viable animal. For certain countries, it may be necessary to specifically exclude certain subjects from this aspect, such as human totipotent stem cells, fertilized eggs, etc.

"transgenic animal" refers to a non-human animal, typically a mammal, preferably a rodent, more preferably a mouse (Mus musculus), and most preferably a BALB/C and C57BL/6 mouse, having in part of its cells a non-endogenous (i.e., heterologous) nucleic acid sequence as an extrachromosomal element.

Plasmid pAdEasy-1 is a genome plasmid of 5 type wild adenovirus (Ad5dE1/3) with deletion of E1 region and E3 region, and has an ampicillin resistance gene.

In some embodiments, the recombinant vector is constructed by a method comprising:

co-transforming pAdEasy-1 with linearized pShuttle-hACE2 into BJ5183 competent cells;

wherein the linearized pShuttle-hACE2 is the pShuttle-hACE2 cleaved from the PmeI cleavage site.

In some embodiments, the pAdEasy-1 is co-transformed with the linearized pShuttle-hACE2 in a mass ratio of 1 (1-5); the transformation can also be carried out by the mass ratio of 1:2, 1:3 and 1: 4.

In some embodiments, the BJ5183 competent cells are cultured for 8-16 h, and then 10-20 minimal single clones are selected to be inoculated into an LB culture medium containing Kana + for culture less than or equal to 8 h.

In some embodiments, the recombinant vector rescues adenovirus in AD293 cells after amplification in XL-Blue competent cells, and the rescued virus is amplified and purified.

In some embodiments, the amplification process employs D2 medium.

In some embodiments, the step of rescuing the adenovirus comprises:

culturing the AD293 cells in a culture container until the cell fusion degree is 50% -70%, then cleaning, replacing with an Opti-MEM culture medium, dripping cell transfection liquid into a cell culture solution for transfection for 3.5-4.5 h after the cells are adapted;

after transfection, changing the culture solution and culturing until cytopathic effect appears, and collecting viruses;

wherein, the transfection final system of each bottle of cells comprises the following components by taking the culture container as a T75 culture bottle:

8.5-12.5 mL of Opti-MEM culture medium, 9-13 mug of linearized recombinant vector and 30-36 mug of PEI.

In some embodiments, the medium used for the liquid change culture after the end of transfection is D10 medium.

In some embodiments, the transfection system comprises, for each flask of cells, based on the culture vessel being a T75 flask:

9.5-11.5 mL of Opti-MEM culture medium, 10-12 mu g of linearized recombinant vector and 32-34 mu g of PEI.

The adenovirus can be administered to the animal by a variety of routes, preferably by nasal instillation.

In some embodiments, the nasal drip has a drip size of (1-4) × 10⁸FFU/(50. mu.l-100. mu.l) adenovirus.

SARS-CoV-2 can be administered to the animal by a variety of routes, preferably by nasal instillation.

In some embodiments, the amount of the nasal drip SARS-CoV-2 is (0.5-1.5) × 10⁵PFU/(20μl～70μl)。

Embodiments of the present invention will be described in detail with reference to examples.

EXAMPLE 1 construction of recombinant vectors

Generally, the longer the length of the foreign gene that an adenoviral vector can accommodate, the lower the efficiency of recombination. The hACE2 is constructed into a shuttle plasmid pShuttle and then recombined with a skeleton plasmid pAdEasy-1, and the method has certain probability, optimizes each step, improves the recombination efficiency of the pShuttle-hACE2 and the pAdEasy-1, and comprises the following specific steps:

1. kit large-extraction pAdEasy-1 plasmid

The molecular weight of the pAdEasy-1 skeleton plasmid is about 33kb, the pAdEasy-1 is extracted by a large-scale plasmid extraction kit for extracting macromolecules of NucleoBondBAC100 from Macherey-Nagel company, and the plasmid of the high-quality pAdEasy-1 is obtained, wherein the operation steps are shown in the kit specification.

Construction and extraction of pShuttle-hACE2 vector

2.1PCR amplification of hACE2 gene (GenBank: AB046569.1)

The hACE2 gene was amplified using pcDNA3.1-hACE-C9 plasmid as a template, and the length of the target fragment was about 2500bp, according to the Q5 High-Fidelity 2X Master Mix kit (NEB).

PCR amplification System:

PCR reaction procedure: pre-denaturation at 98 ℃ for 30 s; denaturation at 98 ℃ for 10s, annealing at 60 ℃ for 30s, extension at 72 ℃ for 1min for 30s, and 30 cycles; extension at 72 ℃ for 2 min.

2.2 purification of PCR products according to kit instructions

2.3 cleavage of pShuttle vector with hACE2

The fragment was digested at 37 ℃ for 2h, and the vector hACE2 fragment was recovered by electrophoresis and quantified, respectively.

2.4 ligation, transformation, selection of monoclonal colonies for identification

Connecting a reaction system: connecting the vector and the target gene in a molar ratio of 1: 5;

the cells were ligated overnight at 16 ℃ and transformed into Stbl3 competent cells, and the next day, single colonies were selected for PCR identification of the cells. And finally, sequencing to verify whether the construction is successful.

2.5 extraction of the pShuttle-hACE2 vector

The integrity of the pShuttle vector is important for efficient recombination, and small extraction with conventional column extraction kits easily results in significant numbers of single-stranded nicks, resulting in recombination failure, so this experiment used a hand-held method to extract the pShuttle plasmid. The method comprises the following steps:

(1) the strain containing the plasmid is inoculated into a 15mL centrifuge tube containing 3mL LB culture solution (Kana +) and is shake-cultured for 12-16h at 37 ℃.

(2) Centrifugation was carried out at 10000 Xg for 1min, and the cells were collected.

(3) The medium was discarded and left behind on absorbent paper to drain the residual. Add 250. mu.L of Buffer P1/RNase A mixture and vortex to resuspend the bacteria.

(4) Add 250. mu.L of Buffer P2 to the resuspension and gently invert the tube 8-10 times.

(5) 350 μ L of Buffer P3 was added and the solution was neutralized thoroughly by immediately inverting 8-10 times. The Buffer uses reagents provided by a plasmid extraction kit of Tiangen corporation.

(6) Centrifuge at 12000 Xg for 10min at 4 ℃.

(7) Weighing the supernatant into a new EP tube, adding 0.7 times volume of isopropanol, mixing well, and standing at-20 deg.C for 15-30min (which may be longer than 1 h).

(8) Centrifuge at 12000 Xg for 10min at 4 ℃ and carefully remove the supernatant and aspirate all droplets from the tube wall.

(9) Add 500. mu.L of 75% ethanol, centrifuge at 12000 Xg for 10min at 4 ℃, carefully remove the supernatant and aspirate all droplets from the tube wall.

(10) The EP tube was uncapped and placed on a lab bench at room temperature to evaporate the remaining liquid to dryness.

(11) The precipitate was dissolved by adding an appropriate amount (usually 20. mu.L) of sterile water (preheated at 55 ℃ C.).

3. Linearized pShuttle and pShuttle-hACE2 plasmids

1) The pShuttle-hACE2 plasmid was linearized with PmeI as follows

And (4) carrying out enzyme digestion at 37 ℃ for 1h, and purifying the product after enzyme digestion.

4. Enzyme digestion product purification (ethanol precipitation method)

Ethanol precipitation method is adopted, column purification is not needed, and single-chain gaps are avoided.

(1) Adding 0.1 time volume of sodium acetate (3mol/L, pH 5.2) into the DNA solution, and mixing well to obtain a final concentration of 0.3 mol/L;

(2) adding 2.5 times volume of pre-cooled ethanol, mixing, and standing at-20 deg.C for 15-30min (which may be longer than 1 hr);

(3) centrifuging at 12000 Xg for 10min at 4 deg.C, carefully removing supernatant, and removing all droplets on the tube wall;

(4) adding 500 μ L of 75% ethanol, centrifuging at 12000 × g for 2min, carefully removing the supernatant, and aspirating all droplets on the tube wall;

(5) placing the uncapped EP tube in a fume hood at room temperature for about 5min to evaporate the residual liquid to dryness;

(6) adding appropriate amount of sterilized water (preheated at 55 deg.C) to dissolve DNA precipitate;

5. linearized pShuttle-hACE2 and pShuttle plasmids were co-transformed with pAdEasy-1 to BJ5183 heat-transfer competent cells, respectively

The transformation efficiency of BJ5183 heat-labile cells is an important factor in determining recombination, and therefore BJ5183 heat-labile cells of high quality were purchased. Meanwhile, the addition ratio of the linearized pShuttle plasmid to the pAdEasy-1 needs to be considered, when the recombination is unsuccessful, the addition ratio of the linearized pShuttle plasmid to the pAdEasy-1 can be adjusted, and the transformation is carried out according to the BJ5183 competence instruction, wherein the addition ratio of the plasmids is as follows:

after recovery, Kana + plates (2-5 plates) were smeared and cultured overnight (16-20h) in an inverted manner.

6. Extracting plasmid for enzyme digestion identification

After transformation, overnight culture, 10-20 minimal single clones were selected on plates and inoculated into Kana + LB medium for 8h (no more than 8h, to prevent excessive recombination) for plasmid lifting, and the procedures were as described in reference to 2.5 for plasmid lifting. And (3) identifying whether the plasmid is successfully recombined by using PacI endonuclease, wherein pShuttle and pAdEasy-1 have two recombination modes, if recombination is carried out between the replication initiation site Ori and the right arm, 30kb and 4.5kb fragments are generated after the plasmid is cut by the PacI endonuclease, and if recombination is carried out between the left arm and the right arm, 30kb and 3kb fragments are generated after the plasmid is cut by the PacI endonuclease, and the two recombination modes are correct. The results are shown in FIG. 1, and the enzyme digestion verification shows that the recombination is successful.

The enzyme digestion system is as follows:

carrying out enzyme digestion at 37 ℃ for 30min, and carrying out electrophoresis identification.

7. Transformation into XL-Blue competent cells for plasmid amplification

BJ5183 is suitable for recombinant plasmid and not suitable for amplification plasmid, the plasmid subjected to enzyme digestion identification recombination is transformed into XL-Blue competent cells, monoclonal antibody is selected, plasmid is extracted, PacI enzyme digestion identification is carried out again, and finally sequencing is carried out to verify whether recombination is correct or not.

Example 2 recombinant adenovirus rescue, amplification and purification

Rescue of recombinant adenoviruses Ad5-hACE2 and Ad5-Empty in AD293 cells and 3-4 rounds of amplification

The recombinant adenovirus plasmids Ad5-hACE2 and Ad5-Empty can rescue the adenovirus in AD293 cells, generally requiring 14-20 days for a long time.

Success in rescue depends on cell status, transfection efficiency, and the need for tolerance to the disease.

The method comprises the following specific steps:

1) AD293 cells as 3 × 10⁶Spreading to T75 culture bottle, culturing for about 20 hr, and culturing at cell density of about 70% (50% -70% density transfection is preferable);

2) transfection: solution A, 1.5mL of Opti-MEM and 11. mu.g of linearized plasmid are mixed evenly and incubated for 5min at room temperature; solution B, 1.5ml of LOpti-MEM and 33 mu g of PEI are mixed evenly and incubated for 5min at room temperature; and C, adding the solution A into the solution B, uniformly mixing by vortex, and incubating at room temperature for 15-30 min.

3) During the incubation, cells were washed once with 12mL of preheated DMEM, the DMEM was discarded, preheated 7.5mL of LOpti-MEM was added, and the mixture was incubated at 37 ℃ for 10 min.

4) After incubation for 10min at 37 ℃, the incubated solution C is slowly added into T75 cells dropwise, and the mixture is gently mixed.

5) After 4h of transfection, the solution was changed and 12mL of preheated D10 was added.

6) 3mL of D10 was supplemented every 4 days and observed for lesion formation.

7) Cytopathic effects were observed after 18 days (typically 14-20 days), cells were blown down, 800g, centrifuged at 4 ℃ for 10min, most of the supernatant was discarded, and 3mL of the supernatant was left to resuspend the pellet.

8)4 rounds of repeated freeze thawing (-80 ℃/37 ℃), 800g, centrifuging at 4 ℃ for 10min, collecting supernatant, which is P0 generation virus, and subpackaging and freezing at-80 ℃.

P1 generation adenovirus amplification

1) AD293 cells as 3 × 10⁶Spread to a T25 culture bottle, and cultured for about 24h, and the cell density is about 80-90%.

2) And (3) virus inoculation: mixing 500 mu L P0 generation virus with 500 mu L D2 culture medium at a ratio of 1:1, mixing the mixture totally to 1mL, discarding cell supernatant, inoculating virus to cells, incubating at 37 ℃ for 1h, supplementing 5mL D2 after 1h, and culturing in a 37 ℃ incubator.

3) The lesions were observed daily, and when more than 90% of the cells became diseased, it took approximately 1 week, the cells were harvested, 800g centrifuged at 4 ℃ for 10min, most of the supernatant was discarded, and 1.5mL of the supernatant was left to resuspend the pellet.

4)4 rounds of repeated freeze thawing (-80 ℃/37 ℃), releasing the virus to the supernatant, centrifuging for 10min at 4 ℃, collecting the supernatant, removing the precipitate, namely the P1 generation virus, and subpackaging and freezing at-80 ℃.

P2-P4 generation adenovirus amplification

The recombinant adenovirus is amplified by P1 generation, the virus titer is increased, the virus needs to be diluted for amplification culture, and the virus titer is increased by 10-100 times in each amplification round. The virus is diluted by 10 times of the D2 culture medium in a gradient way, and the diluted virus is respectively diluted by 10 times, 100 times, 1000 times and 10000 times, so that the dilution ratio of 90 percent of cells with pathological changes after inoculation is about 72 hours, the dilution ratio is the optimal dilution ratio (MOI is about equal to 10), and the dilution ratio is inoculated for higher toxin yield. The adenovirus is amplified to P4 generation, and the adenovirus is amplified in large quantity.

Mass amplification of Ad5-hACE2 and Ad5-Empty

1) AD293 cells were cultured at 1.2 × 10⁷Spread to a 150mm dish culture dish, and culture cells of 80 dishes for 24 hours or so, wherein the cell density is about 90%.

2) The optimal dilution ratio is inoculated in advance (about 72 hours after inoculation, the dilution ratio of 90 percent of cells with pathological changes is the optimal dilution ratio, the MOI is about equal to 10), each dish is inoculated with 6mL of diluted adenovirus, the incubation is carried out for 1 hour at 37 ℃, and 24mLD2 culture medium is supplemented after 1 hour.

3) After about 72 hours after inoculation, when 90% of cells are diseased, the cells are centrifuged at 800g and 4 ℃ for 10min, the cells are collected, and 40ml PBS is used for resuspending the cells.

4) Transferring to a 2mL centrifuge tube at 12000rpm for 10min at 4 ℃ after 4 rounds of repeated freeze thawing (-80 ℃/37 ℃), and taking the supernatant for purification.

Ad5-hACE2 and Ad5-Empty virus purification

1) Preparation of CsCl discontinuous density gradient: 5mL of CsCl heavy liquid and 5mL of CsCl light liquid were slowly added to an ultracentrifuge tube (Beckman ultra-ClearTMcentrifuge tubes, 14X 95 mm). The formulas of the CsCl heavy liquid and the CsCl light liquid are shown in the appendix.

2) Slowly adding the concentrated solution onto the liquid surface of the CsCl light solution, balancing each tube, and ultracentrifuging at 30000rpm and 4 ℃ for 3 h;

3) viral bands (approximately 3mL) were collected into Slide-A-Lyzer^TMG2 dialysis device (dialysis device needs to be balanced in dialysate for 2min in advance, and the dialysis device is used according to the instruction).

4) The dialysis apparatus was placed in a beaker containing 1L of adenovirus dialysate (A195/PBS/5% Sucrose) for dialysis, the beaker was placed in a magnetic stirrer and dialyzed at 4 ℃ with slow stirring at a low speed. The formula of the dialysate is shown in appendix, and the dialysate is changed every 2h and then 2 times.

5) Taking out the virus liquid after dialysis, filtering with 0.22 μm filter membrane for sterilization, subpackaging with 50 μ L/tube, and storing at-80 deg.C.

The P0 generation recombinant adenovirus undergoes 3-4 rounds of amplification in AD293 cells, the virus titer gradually rises, the 4 th round is subjected to a large amount of amplification, the obtained cell lysis supernatant is subjected to ultracentrifugation purification by CsCl, clear upper and lower 2 bands can be seen between CsCl heavy liquid and CsCl light liquid, the lower band is infectious virus particles, and the lower band is collected to indicate the successful purification, which is shown in figure 2.

Ad5-hACE2 and Ad5-Empty Virus Titers assay

Adenovirus titer was determined by plaque formation assay (FFA) with reference to Takara kit (Adeno-X)^TMRapid Titer Kit).

1) AD293 cells were cultured at 2.5 × 10⁴Spread to a 96-well plate, and cultured for about 24h, with the cell density of about 95%.

2) And (3) virus dilution: adenovirus was lysed on ice and the virus was diluted in D2 medium in a ten-fold gradient from 10^-1Diluting to 10^-9The titer of the purified adenovirus can reach 10¹⁰FFU/mL, therefore, it can be diluted to 10^-9。

3) And (3) virus incubation: cell supernatants were discarded by vacuum pump and blanked (D2), 10)^-9-10^-5The virus is added to the cell wells in 4-6 replicate wells per dilution (typically 10)^-5-10^-1After 48h the lesion was severe and unable to count plaques), 50 μ L/well. The plates were shaken every 15min in a 37 ℃ incubator to promote infection.

4) Liquid supplementing: after 1h of infection, 100. mu.L/well D2 was directly supplemented without discarding the solution.

6) And after the inoculation for 48 hours, completely sucking the liquid by using a vacuum pump, then opening the cover, and blowing for 10min in the biological safety cabinet.

7) Fixing: placing anhydrous alcohol in advance, pre-cooling at-20 deg.C, adding pre-cooled anhydrous alcohol gently, 100 μ L/hole, and fixing at-20 deg.C for 20 min.

8) And (3) sealing: wash 3 times with PBS containing 1% BSA, 150 μ Ι/well.

9) Incubating the primary antibody: primary antibodies (adenovirus type 5 immunized mouse sera) were diluted with 1% BSA in PBS, diluted 1:400, 50. mu.L/well and incubated for 1h at 37 ℃.

10) Washing: discard primary antibody, wash 3 times with PBS containing 1% BSA, 150. mu.L/well.

11) Incubation of secondary antibody: secondary antibodies (Anti-mouse-HRP) were diluted in PBS containing 1% BSA at 1:1250, 50. mu.L/well and incubated for 1h at 37 ℃.

12) The secondary antibody was discarded and washed 3 times with PBS containing 1% BSA at 150. mu.L/well.

13) DAB color development: the reaction is stopped when the reaction is observed under a microscope after developing for about 10min, and the reaction is stopped when the reaction is observed with obvious brown spots, background is easy to appear when the reaction is too dark, and spots are not clear when the reaction is too light.

14) Stopping developing color, discarding developing liquid, adding ddH₂Wash 2 times O and then spin dry the plate thoroughly.

15) Spots were scanned on an enzyme linked spot scanner and virus titers were calculated.

The virus titer can reach 10 by adopting a spot formation experiment to determine the adenovirus titer¹⁰FFU/mL or more, the results are shown in the following table.

Results of recombinant adenovirus titer

Western-blot and flow results showed that ACE2 was correctly expressed in vitro.

17Cl-1 cells were transduced with Ad5-hACE2 and Ad5-Empty (negative control) at MOI of 100, respectively, and expression of hACE2 was identified by Western-blot after 48h of transduction, indicating successful expression of hACE2, as shown in A of FIG. 3. The localization of hACE2 was confirmed by flow cytometry, and positive cell populations were visualized by staining, indicating that hACE2 was localized to the cell surface, as shown in B of fig. 3.

EXAMPLE 3 construction of animal models of recombinant adenovirus and SARS-CoV-2 Virus-transduced mice

Ad5-hACE2 and Ad5-Empty transduced mice

The mice were moved to a biosafety cabinet and anesthetized with isoflurane (isoflurane). Placing a plastic dryer in a biological safety cabinet, and adding isoflurane into the plastic dryer; the mice are placed in a dryer for anesthesia, and the respiration of the mice is observed until the anesthesia effect is achieved.

The anesthetized mice were removed and instilled nasally 2.5 × 10⁸FFU/75. mu.l Ad5-hACE2 or Ad 5-Empty.

Mice were waited for recovery from anesthesia and returned to their cages. Feeding for 5 days.

After mice were transduced with Ad5-hACE2, in immunohistochemical identification results, both the anti-hACE 2 antibody and the anti-tag antibody C9 indicated successful expression of hACE2 in the mouse lung (FIG. 4).

After the Ad5-hACE2 adenovirus is transduced into the mouse lung, the mouse lung has certain timeliness and can be eliminated by the mouse immune system. The invention selects the transduction receptor to attack the virus after 5 days, on one hand, the natural immune reaction initiated by the adenovirus in the mouse body is mostly dissipated after 5 days, which is beneficial to the replication of the virus; on the other hand, after 5 days of transduction, the adenovirus receptor is highly expressed in the lung and is not cleared by the immune system.

Mice transduced with SARS-CoV2 infection (to be done in biosafety level 3 laboratories)

All mice were infected in biosafety cabinets. Mice were anesthetized with isoflurane (isoflurane). Danger: the mice bite or escape. The operation key points are as follows: the mouse was gently and slowly grabbed without frightening. And (3) detecting the anesthesia effect of the mouse in real time by adopting a mode of extruding the sole and the like, and performing downstream operation after complete anesthesia. )

Diluting SARS-CoV-2 virus, taking out the frozen tube containing SARS-CoV-2 virus from-80 deg.C refrigerator, and diluting SARS-CoV-2 virus to 1 × 10 with DMEM⁵PFU/50. mu.l. (danger: spill and aerosol generation. operational points: use of cryogenic vial and secondary containment box; slow lid opening and gentle dilution.)

The anesthetized mice were removed and 50 μ l of diluted virus was instilled intranasally. (danger: splash. operating point: mouse firmly grabs and immobilizes, instillation liquid is continuous and gentle.)

Mice were waited for recovery from anesthesia and placed in new cages to reduce possible intra-cage contamination.

The unused virus stock and diluent were inactivated with 10% freshly prepared available chlorine disinfectant and autoclaved.

Clinical signs (respiratory depression, arch back, no semen, inability to stand and dehydration) were observed daily for infected mice.

After 5 days from the transduction of mice with Ad5-hACE2, SARS-CoV-2 was nasally infected, and two days after infection, lung tissues were harvested and the virus titer was determined. The novel coronavirus can be replicated in the lung of a mouse at a high titer, and the titer of the virus in each gram of tissue can reach 10⁷PFU (fig. 5), mice developed corresponding clinical and pathological manifestations of pneumonia. The result shows that the invention successfully constructs an nCoV infection animal model transduced by Ad5-hACE2 and can support the virus to replicate in the lung.

Appendix

1. Cell culture solution formula

CsCl light and heavy liquid formulations

3. Adenovirus dialysate and stock formulation (A-195/PBS/5% Sucrose)

Mixing the above reagents, stirring well on a magnetic stirrer, filtering with a 0.22 μm filter flask, and storing at 4 deg.C.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1.A method for preparing a non-human animal capable of expressing human ACE2 transgene by using adenovirus transduction, wherein the adenovirus is rescued in AD293 cells by a recombinant vector obtained by recombining pShuttle-hACE2 and pAdEasy-1, and the pShuttle-hACE2 is pShuttle inserted with a DNA sequence of the human ACE 2;

2. The method of claim 1, wherein the recombinant vector is constructed by a method comprising:

3. The method of claim 2, wherein the pAdEasy-1 is co-transformed with the linearized pShuttle-hACE2 in a mass ratio of 1 (1-5).

4. The method of claim 2, wherein after transformation, the BJ5183 competent cells are cultured for 8-16 h, and then 10-20 minimal single clones are selected and inoculated to an LB culture medium containing Kana + for culture less than or equal to 8 h.

5. The method of claim 1, wherein the recombinant vector rescues adenovirus in AD293 cells after amplification in XL-Blue competent cells, and the rescued virus is amplified and purified.

6. The method of claim 5, wherein the step of rescuing the adenovirus comprises:

7. The method of claim 1, wherein the method of transducing the animal with the adenovirus is by nasal instillation.

8. The method according to claim 7, wherein the nasal drip is performed at a drip rate of (1-4) × 10⁸FFU/(50. mu.l-100. mu.l) adenovirus.

9. The method of any one of claims 1 to 8, wherein the animal is a rodent.

10. The method of claim 9, wherein the animal is a mouse (Mus musculus).

11. Use of the transgenic non-human animal obtained according to the method of any one of claims 1 to 10 for constructing a SARS-CoV-2 infectious disease model.

12. The use of claim 11, wherein the animal is subjected to simultaneous nasal instillation of SARS-CoV-2.

13. The use according to claim 12, wherein the amount of SARS-CoV-2 for nasal drip is (0.5-1.5) × 10⁵PFU/(20μl～70μl)。