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• • 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
  • C12N7/00—Viruses; Bacteriophages; Compositions thereof; Preparation or purification thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/12—Antivirals
  • A61P31/14—Antivirals for RNA viruses
  • A61P31/16—Antivirals for RNA viruses for influenza or rhinoviruses
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P37/00—Drugs for immunological or allergic disorders
  • A61P37/02—Immunomodulators
  • A61P37/04—Immunostimulants
• • 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
  • C12N2760/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses negative-sense
  • C12N2760/00011—Details
  • C12N2760/16011—Orthomyxoviridae
  • C12N2760/16111—Influenzavirus A, i.e. influenza A virus
  • C12N2760/16151—Methods of production or purification of viral material
• • 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
  • C12N2760/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses negative-sense
  • C12N2760/00011—Details
  • C12N2760/16011—Orthomyxoviridae
  • C12N2760/16111—Influenzavirus A, i.e. influenza A virus
  • C12N2760/16151—Methods of production or purification of viral material
  • C12N2760/16152—Methods of production or purification of viral material relating to complementing cells and packaging systems for producing virus or viral particles
• • 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
  • C12N2760/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses negative-sense
  • C12N2760/00011—Details
  • C12N2760/16011—Orthomyxoviridae
  • C12N2760/16211—Influenzavirus B, i.e. influenza B virus
  • C12N2760/16251—Methods of production or purification of viral material
• • 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
  • C12N2760/00—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA ssRNA viruses negative-sense
  • C12N2760/00011—Details
  • C12N2760/16011—Orthomyxoviridae
  • C12N2760/16311—Influenzavirus C, i.e. influenza C virus
  • C12N2760/16351—Methods of production or purification of viral material

Definitions

• the present invention relates to animal cells which can be infected by viruses and are adapted to growth in suspension in medium free of animal-derived components, such as serum-free medium, and to processes for the replication of viruses in cell culture using these cells.
• the present invention further relates to the viruses obtainable by the process described and to vaccines which contain viruses of this type or constituents thereof.
• influenza vaccine for the treatment of humans and animals consist of one or more virus strains which have been replicated in embryonated hens' eggs. These viruses are isolated from the allantoic fluid of infected hens' eggs and their antigens are used in vaccines as intact virus particles, as virus particles disintegrated by detergents and/or solvents, as chemically or physically inactivated viruses, or as isolated, defined virus proteins as in subunit vaccines. The viruses are often inactivated by processes known to the person skilled in the art. The replication of live attenuated viruses, which are tested in experimental vaccines, is also carried out in embryonated hens' eggs.
• the use of embryonated hens' eggs for vaccine production is time-, labor- and cost-intensive.
• the eggs, from healthy flocks of hens monitored by veterinarians, have to be incubated before infection, customarily for 12 days. Before infection, the eggs have to be selected with respect to living embryos, as only these eggs are suitable for virus replication. After infection the eggs are again incubated, customarily for 2 to 3 days. The embryos still alive at this time are killed by subjecting them to a cold environment, and the allantoic fluid is then obtained from the individual eggs by aspiration.
• laborious purification processes substances from the hen's egg that lead to undesired side effects of the vaccine are separated from the viruses, and the viruses are concentrated.
• eggs are not sterile (pathogen-free), it is additionally necessary to remove and/or to inactivate pyrogens and all pathogens that are possibly present.
• Viruses of other vaccines such as, for example, rabies viruses, mumps, measles, rubella, polio viruses, tick bourne encephalits viruses such as Friihsommer-Meningo Ecephalitis (FSME) virus can be replicated in cell cultures.
• rabies viruses mumps, measles, rubella, polio viruses, tick bourne encephalits viruses
• FSME Friihsommer-Meningo Ecephalitis
• influenza viruses can be replicated in cell cultures. Beside hens' embryo cells and hamster cells (BHK21-F and HKCC), MDBK and MDCK cells have been described as suitable cells for the in-vitro replication of influenza viruses (Kilbourne, E. D., in: Influenza, pages 89-110, Plenum Medical Book Company-New York and London, 1987).
• a prerequisite for a successful infection is the addition of proteases to the infection medium, preferably trypsin or similar serine proteases, as these proteases extracellularly cleave the precursor protein of hemagglutinin [HA 0 ] into active hemagglutinin [HA 1 and HA 2 ].
• a more cost-effective alternative is cell proliferation in systems where the cells do not need to be grown adherently to the culture container or on the surface of micro carriers.
• U.S. Pat. No. 6,656,720 which is wholly incorporated by reference herein, provides an example of one such method wherein MDCK cells that are grown in suspension are infected with influenza virus.
• additional cell lines and methodologies are needed that provide alternative means of growing viruses to increase efficiencies and reduce overall costs.
• the present invention is directed to a method of replicating virus in a culture of sCLDK cells comprising: a) inoculating a suspension of sCLDK cells with a virus, thereby infecting the sCLDK cells; b) allowing the virus to reproduce in the infected sCLDK cells; and c) harvesting the virus from the suspension culture of sCLDK cells.
• the virus can be an influenza virus, such as a human influenza virus, an avian influenza virus, an equine influenza virus, a swine influenza virus, a canine influenza virus, or a feline influenza virus.
• influenza virus can be an H1 influenza virus, an H2 influenza virus, an H3 influenza virus, an H5 influenza virus or an H7 influenza virus.
• influenza virus can be an H5N1 influenza virus, an H3N8 influenza virus, an H1N1 influenza virus, an H3N2 influenza virus, an H2N3 influenza virus, an H7N8 influenza virus or an H3N1 influenza virus.
• a protease to cleave the precursor protein of hemagglutinin is added to the suspension of sCLDK cells.
• the protease can be trypsin.
• the present invention is also directed to a process of adapting substrate-dependent CLDK cells for growth in suspension comprising a) inoculating a sample of substrate-dependent CLDK cells in a medium comprising serum substitutes; b) growing the cells in suspension in the medium; c) serially passaging the CLDK cells in suspension in fresh batches of the medium; and d) weaning the CLDK cells in suspension off of the serum substitutes by reducing the amount of the serum substitutes in the medium to zero.
• This process is also referred to as “the adaptation process.”
• the medium can be serum-free.
• the medium can also be free of any animal derived components.
• the cells are serially passaged in step (c) until the seven day growth factor is at least from about 3 to 20, preferably greater than about 5, more preferably greater than about 7, most preferably greater than about 10.
• the CLDK cells in suspension can be weaned off of the serum substitutes over the subsequent 3 to 6 passages.
• CLDK cells are serially passaged in suspension until the average growth factor of at least 5-10 passages in suspension is greater than about 5, at which point they are weaned off of the serum substitute over the subsequent 6 or fewer passages.
• the CLDK cells are serially passaged in suspension until the average growth factor of at least 10 passages in suspension is greater than about 8, at which point they are weaned off of the serum substitute over the subsequent 6 or fewer passages.
• the CLDK cells are serially passaged in suspension until the average growth factor of at least 5 passages in suspension is greater than about 12, at which point they are weaned off of the serum substitute over the subsequent 6 or fewer passages.
• the CLDK cells can successfully be weaned off of the serum substitutes in the adaptation process providing that the 7 day growth factor of the passage immediately prior to the first weaning passage is at least 5.
• the 7 day growth factor of the last passage immediately prior to the weaning passage is at least 7, more preferably at least 10, even more preferably at least about 13.
• the present invention is also directed to a method of continuously propagating sCLDK cells in suspension comprising: a) inoculating sCLDK cells into a medium; b) growing the sCLDK cells in suspension for a period of from about 4 to 10 days; c) transferring a sample of cultured material from (b) into fresh cell-free medium; d) and repeating (b) and (c) for a period of continuous growth.
• the medium can be serum-free.
• the medium can be animal protein-free.
• the sample can be transferred to the fresh cell-free medium without the prior addition of any protease.
• the cell density after transferring the sample according to (c) can be at least 3 ⁇ 10 5 cells/mL, and is preferably at least 5 ⁇ 10 5 cells/mL.
• the sCLDK cells can have a growth factor greater than 3 over a 4-10 day period, preferably a growth factor greater than about 5, most preferably greater than about 10, over a 4-10 day period.
• the present invention is also directed to sCLDK cells capable of growing in suspension obtainable by the adaptation process.
• the adaptation process is the process of adapting substrate-dependent CLDK cells for growth in suspension comprising a) inoculating a sample of substrate-dependent CLDK cells in a medium comprising serum substitutes; b) growing the cells in suspension in the medium; c) serially passaging the CLDK cells in suspension in fresh batches of the medium; and d) weaning the CLDK cells in suspension off of the serum substitutes by reducing the amount of the serum substitutes in the medium to zero.
• the medium can be serum-free.
• the serum substitutes can be animal-protein free.
• the present invention is also directed to use of such sCLDK cells obtained by this process for replicating virus.
• the present invention is also directed to use of such virus replicated in such sCLDK cells obtained by this process in the manufacture of a vaccine.
• the present invention is also directed to a composition comprising cell culture medium and sCLDK cells.
• the present invention also relates to a method of making a vaccine comprising a) inoculating medium with sCLDK cells; b) growing the sCLDK cells in suspension in the medium, thereby generating a suspension of sCLDK cells; c) incubating the suspension of sCLDK cells with virus thereby generating a suspension of infected sCLDK cells; d) allowing the virus to reproduce in the infected sCLDK cells; e) harvesting or isolating the virus; and f) mixing the harvested or isolated virus with one or more pharmaceutically acceptable carrier thereby making a vaccine.
• the present invention relates to making available cells and processes that make possible simple and economical virus replication in cell culture.
• the invention thus relates to animal cells that can be infected by viruses and that are adapted to growth in suspension in serum-free or animal protein-free medium. It was found that it is possible with the aid of cells of this type to replicate viruses in cell culture in a simple and economical manner. Because the cells are adapted for growth in suspension, production batches yield greater numbers of cells and subsequently higher titers of virus. A greater yield of virus reduces overall costs of production. A further advantage is that the consumption of media is markedly decreased, thereby reducing total media costs.
• an advantage of the present invention is growth of cells (and subsequent replication of viruses) in medium that is free of any animal derived components, such as bovine serum or fetal calf serum, thereby eliminating the risk of various pathogens including without limitation TSE (transmissible spongiform encephalopathy).
• TSE transmissible spongiform encephalopathy
• the cells used according to the invention are derived from substrate-dependent Cutter Laboratory Dog Kidney (CLDK) cells.
• CLDK substrate-dependent Cutter Laboratory Dog Kidney
• “substrate-dependent CLDK cells” and like terms are used interchangeably with “adherent CLDK cells,” “aCLDK cells” or like terms.
• aCLDK cells are different from suspension CLDK cells. Whereas the former grow adherently, the latter grow in suspension, such as in a shaker flask or other large-scale production container including without limitation disposable or non-disposable bioreactors or biocontainers.
• aCLDK cells require a surface on which to grow, such as the surface of a roller bottle or microcarriers or beads added to the medium. aCLDK cells do not grow in suspension. When inoculated into medium in a shaker flask placed on an oscillating platform, aCLDK cells may maintain some viability, but do not grow. Rather, aCLD
• Suspension CLDK cells are also termed “sCLDK” cells or “sCLDK-SF” cells to indicate that they grow in a serum-free media.
• sCLDK cells are derived from aCLDK cells by passaging through serum-free medium in suspension as described herein. On account of these properties and their ability to serve as host cells for replicating viruses, sCLDK cells are suitable for economical replication of viruses in cell culture by means of a simple and cost-effective process.
• sCLDK cells do grow in a shaker flask placed on an oscillating platform or in other suspension growth means. Not only do sCLDK cells maintain viability in such suspended growth conditions, but they can multiply in number without aggregating or clumping as is the case with aCLDK cells.
• sCLDK cells have several advantages over aCLDK cells.
• sCLDK cells grow in suspension.
• sCLDK cells have a growth factor of at least three (3) when passed into fresh media for growth in suspension over a 4-10 day period.
• the sCLDK cells described herein grow in suspension by a factor of greater than 3, preferably greater than 5, in a 4-10 day period. More preferably, the sCLDK cells described herein grow in suspension by a factor of greater than about 6, most preferably greater than about 10, in a 4-10 day period.
• sCLDK cells are also able to grow continuously in suspension.
• sCLDK cells can grow continuously in suspension by a factor of greater than 3, preferably greater than 5, when passed into fresh media every 4-10 days. More preferably, the sCLDK cells described herein can grow continuously in suspension by a factor of greater than about 6, most preferably greater than about 10, when passed into fresh media every 4-10 day period.
• sCLDK cells can grow in the absence of serum or other animal derived media supplements.
• sCLDK cells on average at least triple when passed into fresh media containing no serum or other animal derived media supplements over a 4-10 day period.
• the sCLDK cells described herein grow in media containing no serum or other animal derived media supplements by a factor of greater than 3, preferably greater than 5, in a 4-10 day period. More preferably, the sCLDK cells described herein grow when passed into fresh media containing no serum or other animal derived media supplements by a factor of greater than about 6, most preferably greater than about 10, in a 4-10 day period.
• sCLDK cells are also able to grow continuously in media containing no serum or other animal derived components.
• sCLDK cells can grow continuously in media containing no serum or other animal derived components by a factor of greater than 3, preferably greater than 5 when passed into fresh media every 4-10 days. More preferably, the sCLDK cells described herein can grow continuously in media containing no serum or other animal derived components by a factor of greater than about 6, most preferably greater than about 10, when passed into fresh media every 4-10 days.
• an advantage of sCLDK cells is their ability to grow continuously in suspension in media containing no serum or other animal derived components.
• sCLDK cells can grow continuously in suspension in media containing no serum or other animal derived components by a factor of greater than 3, preferably greater than 5, when passed into fresh media every 4-10 days. More preferably, the sCLDK cells described herein can grow continuously in suspension in media containing no serum or other animal derived components by a factor of greater than about 6, most preferably greater than about 10, when passed into fresh media every 4-10 day period.
• growth factor or like terms refer to the multiplicative value by which an initial cell population has grown over a period of time.
• a growth factor of 2 or 3 indicates that the cell density has respectively doubled or tripled relative to the starting cell density when cells were passed (i.e., inoculated or planted) into the fresh media.
• a growth factor of 10 or 20 indicates that the cell density has respectively multiplied by a factor of 10 or 20 relative to the starting cell density when the cells were passed into the fresh media.
• a growth factor of 1 or less indicates that the cell density did not increase or that the cell population has declined.
• the present invention therefore also relates to a process for the replication of viruses in cell culture in which cells according to the invention are used.
• the process that comprises the following steps: i) proliferation of the cells according to the invention described above in serum-free medium in suspension; ii) infection of the cells with viruses; iii) culturing of the infected cells; and iv) isolation of the replicated viruses.
• titer can be increased as in the case of influenza virus
• protease can be added shortly before, simultaneously to or shortly after infection.
• sCLDK cells are grown in a serum free media to replicate influenza virus.
• the skilled artisan is aware of other viruses that can be replicated in the sCLDK cells described herein, and is not limited to replication of influenza viruses.
• the present invention is also directed to a method of replicating virus in a culture of sCLDK cells comprising: a) inoculating a suspension of sCLDK cells with a virus, thereby infecting the sCLDK cells; b) allowing the virus to reproduce in the infected sCLDK cells; and c) harvesting the virus from the suspension culture of sCLDK cells.
• the virus can be harvested through centrifugation, filtration or other mechanical or biochemical separation means of the infected cell suspension.
• harvested virus can include virus in the presence of sCLDK cells or sCLDK cell debris.
• Harvested virus can also include virus in the absence of sCLDK cells or sCLDK cell debris.
• the cells according to the invention can preferably be cultured in media free of animal derived components (e.g., serum-free media, animal protein-free media) known to the person skilled in the art.
• animal derived components e.g., serum-free media, animal protein-free media
• Non-limiting examples of such media include Iscove's medium, ultra CHO medium (BioWhittaker), EX-CELLTM MDCK serum-free medium (JRH Biosciences, Lenexa, Kans.)).
• Other serum-free media that may be used according to the present invention include EX-CELLTM 520 medium (JRH Biosciences, Lenexa, Kans.) and HyQ PF CHO medium (Hyclone, Logan, Utah).
• EX-CELLTM 302 medium JRH Biosciences, Lenexa, Kans.
• HyQ PF CHO MPS medium Hyclone, Logan, Utah
• Rencyte BHK medium Medicult, Jyllinge, Denmark
• Other soy- or yeast-based animal protein-free media that may be used according to the invention include those described in U.S. Pat. No. 7,160,699 or U.S. Published Patent Applications No. 2003/0203448, 2004/0077086, 2004/0087020, 2004/0171152, 2005/0089968, 2006/0094104, 2006/0286668, which are all hereby incorporated by reference in their entirety.
• Serum substitutes can be added to the animal-derived component-free media. Such substitutes are themselves free of any animal-derived components, yet may contain recombinant animal proteins expressed in cells that were preferably cultured in media free of animal-derived components. Serum substitutes can contain recombinant growth factors, transferrin substitutes or recombinant transferrin substitutes, synthetic hormones and/or other recombinant proteins. Serum substitutes are free of any adventitious viruses because the recombinant protein components are manufactured in a controlled environment in pathogen-free or viral-free cells. Hence, serum substitutes have no virus or TSE (transmissible spongiform encephalopathy) risk.
• TSE transmissible spongiform encephalopathy
• Serum substitutes are preferably used to adapt adherent CLDK cells for growth in suspension (i.e., transform aCLDK cells to sCLDK cells). However, such substitutes can also be used for culturing sCLDK cells in suspension for growth of virus according to the present invention.
• a non-limiting example of a serum substitute includes LIPUMINTM serum substitute (PAA Laboratories GmbH, Pasching, Austria).
• the temperature for the proliferation of the cells before infection as in the case with influenza viruses is preferably 37° C.
• Culturing for proliferation of the cells can be carried out in a perfusion system, e.g. in a stirred vessel fermenter, using cell retention systems known to the person skilled in the art, such as, for example, centrifugation, filtration, spin filters and the like, using batch processes or using other techniques well known to the skilled artisan.
• the cells are in this case preferably proliferated for 2 to 18 days, particularly preferably for 3 to 11 days. Exchange of the medium is carried out in the course of this, increasing from 0 to approximately 1 to 3 volumes per day.
• the cells are proliferated up to very high cell densities in this manner, preferably up to approximately 2 ⁇ 10 7 cells/ml.
• Perfusion rates during culture in a perfusion system can be regulated both via the cell count, the content of glucose, glutamine or lactate in the medium and via other parameters known to the person skilled in the art.
• In the case of infection with influenza viruses about 85% to 99%, preferably 93 to 97%, of the fermenter volume is transferred with cells to a further fermenter.
• the cells remaining in the first fermenter can in turn be mixed with medium and replicated further in the perfusion system. In this manner, continuous cell culture for virus replication is available.
• the pH of the culture medium used can be regulated during culturing and is in the range from pH 6.6 to pH 7.8, preferably in the range from pH 6.8 to pH 7.3.
• the pO 2 value is advantageously regulated in this step of the process and is preferably between 25% and 95%, in particular between 35% and 60% (based on the air saturation).
• the infection of the cells cultured in suspension is preferably carried out when the cells in the batch process have achieved a cell density of about 8 to 25 ⁇ 10 5 cells/ml or about 5 to 20 ⁇ 10 6 cells/ml in the perfusion system.
• the infection of the cells in the case of influenza viruses is carried out at an m.o.i. (multiplicity of infection) of about 0.0001 to 10, preferably of 0.002 to 0.5.
• the addition of the protease which brings about the cleavage of the precursor protein of hemagglutinin [HA 0 ] and thus the adsorption of the viruses on the cells, can be carried out according to the invention shortly before, simultaneously to or shortly after the infection of the cells with influenza viruses. If the addition is carried out simultaneously with the infection, the protease can either be added directly to the cell culture to be infected or, for example, as a concentrate together with the virus inoculate.
• the protease is preferably a serine protease, and particularly preferably trypsin.
• trypsin is added to the cell culture to be infected to a final concentration of 1 to 200 ⁇ g/ml, preferably 5 to 50 ⁇ g/ml, and particularly preferably 5 to 30 ⁇ g/ml in the culture medium.
• trypsin reactivation can be carried out by fresh addition of trypsin in the case of the batch process or in the case of the perfusion system by continuous addition of a trypsin solution or by intermittent addition. In the latter case, the trypsin concentration is preferably in the range from 1 ⁇ g/ml to 80
• the infected cell culture is cultured further to replicate the viruses, in particular until a maximum cytopathic effect or a maximum amount of virus antigen can be detected.
• the culturing of the cells is carried out for 2 to 10 days, in particular for 3 to 7 days.
• the culturing can in turn preferably be carried out in the perfusion system or in the batch process.
• the cells can be cultured at a temperature of 30° C. to 37° C. in an incubator set at 5-15% CO 2 , most preferably around 10% CO 2 .
• the culturing of the cells after infection as in the case of influenza viruses is in turn preferably carried out at regulated pH and pO 2 .
• the pH in this case is preferably in the range of from 6.6 to 7.8, particularly preferably from 6.8 to 7.2, and the pO 2 in the range of from 25% to 150%, preferably from 30% to 75%, and particularly preferably in the range of from 35% to 60% (based on the air saturation).
• the cells After infection as in the case with influenza viruses, the cells can either be slowly diluted by further addition of medium or medium concentrate over several days or can be incubated during further perfusion with medium or medium concentrate decreasing from approximately 1 to 3 to 0 fermenter volumes/day.
• the perfusion rates can in this case in turn be regulated by means of the cell count, the content of glucose, glutamine, lactate or lactate dehydrogenase in the medium or other parameters known to the person skilled in the art.
• the harvesting and isolation of the replicated virus is carried out within 2 to 10 days, preferably 3 to 7 days, after infection.
• the cells or cell residues are separated from the culture medium by means of methods known to the person skilled in the art, for example by centrifugation, separators or filters.
• the concentration of the virus present in the culture medium is carried out by methods known to the person skilled in the art, such as, for example, gradient centrifugation, filtration, precipitation and the like.
• influenza viruses that are obtainable by a process according to the invention. They can be harvested and formulated by known methods to give a vaccine for administration to humans or animals.
• the immunogenicity or efficacy of a vaccine comprising the influenza viruses obtained can be determined by methods known to the person skilled in the art, e.g., by means of the protection imparted in the loading experiment or as antibody titers of neutralizing antibodies.
• the determination of the amount of virus or antigen produced can be carried out, for example, by the determination of the amount of hemagglutinin according to methods known to the person skilled in the art. It is known, for example, that cleaved hemagglutinin binds to erythrocytes of various species, e.g. to chicken erythrocytes. This makes possible a simple and rapid quantification of the viruses produced or of the antigen formed.
• the invention also relates to vaccines that contain virus obtainable from the process according to the invention.
• Vaccines of this type can optionally contain the additives customary for vaccines, in particular substances that increase the immune response, i.e., adjuvants, e.g. hydroxide of various metals, carbomers, constituents of bacterial cell walls, oils or saponins, and customary pharmaceutically tolerable excipients.
• adjuvants e.g. hydroxide of various metals, carbomers, constituents of bacterial cell walls, oils or saponins, and customary pharmaceutically tolerable excipients.
• viruses can be present in the vaccines as intact virus particles, in particular as live attenuated viruses.
• virus concentrates are adjusted to the desired titer and either lyophilized or stabilized in liquid form.
• the vaccines according to the invention can contain disintegrated, inactivated or intact but inactivated viruses.
• the infectiousness of the virus is destroyed by means of chemical and/or physical methods (e.g., by detergents or formaldehyde).
• the vaccine is then adjusted to the desired amount of antigen and after possible admixture with adjuvants or after possible vaccine formulation, dispensed, for example, in liposomes, microspheres or other “slow release” formulations.
• the vaccines according to the invention can finally be present as subunit vaccine, i.e. they can contain defined, isolated virus constituents, preferably isolated proteins of the influenza or other virus. These constituents can be isolated from the virus by methods known to the person skilled in the art.
• influenza or other viruses obtained by the process according to the invention can be used for diagnostic purposes.
• the present invention also relates to diagnostic compositions that contain influenza or other viruses according to the invention or constituents of such viruses, if appropriate, in combination with additives customary in this field and suitable detection agents.
• CLDK cells are anchorage dependent, and hence require a substrate or surface on which to grow.
• Suitable substrates include the interior surfaces of containers such as T-flasks or roller bottles, or upon the surface of beads or microcarriers that can be added to a culturing container.
• these cells form monolayers on the substrate, and can be grown in static culture and roller bottle. These cells require serum to grow and are epithelial in morphology.
• EX-CELLTM MDCK serum-free medium refers to a mixture of EX-CELLTM MDCK serum-free medium (SAFC Biosciences, Lenexa, Kans.) supplemented with L-glutamine (20 mLs of 200 mM solution/L of medium) and gentamicin (0.5 mL of 100 g/mL solution for every liter of medium).
• the resuspended cells were transferred to a 125 mL shaker flask fitted with a 0.2 ⁇ vented cap (Corning Inc., Corning, NY), to which 30 mLs of additional supplemented EX-CELLTM MDCK serum-free medium was added to bring the total volume to 50 mLs. These cells correspond to passage no. 1 in Table 1 below and were placed on an orbital shaker plate in a 37° C. water jacketed incubator with a 10% CO 2 feed for a week.
• the next 14 passages also included 1% LipuminTM ADCF (animal derived component free) serum substitute (PAA Laboratories GmbH, Pasching, Austria) in the media.
• the average growth factor (as shown in Table 1) was greater than 12 and the cells were >95% viable.
• cells were weaned to 0.5% Pluronic® F68 surfactant and 0.5% LipuminTM ADCF serum substitute.
• Pluronic® F68 surfactant and 0.25% LipuminTM ADCF serum substitute In the next passage, cells were weaned to 0.25% Pluronic® F68 surfactant and 0.25% LipuminTM ADCF serum substitute.
• the subsequent 6 passages had the cells completely free of Pluronic® F68 surfactant and LipuminTM ADCF serum substitute. During these last 6 passages, the cells had a growth factor on average greater than 17 (as shown in Table 1) and continued to have high viability.
• Table 1 shows the passage history described in this example.
• Supplemented EX-CELLTM MDCK serum-free medium was used in every passage with the indicated amount of Pluronic® F68 surfactant or LipuminTM ADCF serum substitute as shown, for a total volume of 50 mLs.
• Each passage was into a 125 mL shaker flask and placed on an orbital shaker plate in a 37° C. water jacketed incubator with a 10% CO 2 feed for a week.
• the “Cell Plant Density” refers to the concentration of cells in the 50 mLs of medium at the beginning of the passage (i.e., the beginning of the week) and is given in cells/mL.
• the cells were counted from a sample of material to determine the “Cell count/mL.”
• the “7-Day Growth Factor” was determined by dividing the “Cell count/mL” value by the “Cell Plant Density” value.
• a small cell stock (15-20 cryovials) was frozen in ampoules and stored in liquid nitrogen (LN) with 10% DMSO (Sigma-Aldrich Co., St. Louis, Mo.). The designation was changed to sCLDK-SF, referring to “s” as suspension and “-SF” as serum free during this process. No serum was utilized in the freezing of this cell line.
• Example 1L of supplemented EX-CELLTM MDCK serum-free medium was prepared using an aseptic technique. Thereafter, 2-3 mLs of cells from the frozen ampoules of passage 41 of Example 1A were retrieved from liquid nitrogen and allowed to thaw. The thawed ampoules were sprayed with 70% alcohol and allowed to dry. A sterile ampoule snapper was used to break open all vials. Thereafter, a sterile pipette was used to transfer an ampoule of cells to a small sterile tube with cap (sterile 4.5 mL cryovial or equivalent). This step was repeated for the second and third ampoules.
• EX-CELLTM MDCK serum free media was then added to the 125 mL shaker flask, which was then placed on an orbital shaker (100-110 RPM) inside a 3TC incubator set at 10% CO 2 .
• the cells were incubated four to seven days. Seven days yielded the highest cell growth factors without a substantial loss in viability. Cell and viability count were performed using an automated mammalian cell counter.
• the following procedure was optimized for continuous growth of sCLDK-SF cells. This process begins after recovering cells as in Example 1C, and can be repeated every 7 days to maintain continuous cell growth. Cells are grown in supplemented EX-CELLTM MDCK serum-free medium.
• a sterile pipette is used to transfer a cell sample from the shaker flask to a sample vial.
• Cell and viability count is performed using an automated or manual means of counting. Once counts are performed, the total volume of cells needed to plant a new shaker flask with 50 mLs at a cell density of 5.0 ⁇ 10 5 cells/mL (or, 2.5 ⁇ 10 7 cells/125 mL shaker flask) is calculated.
• the calculated volume of cells is transferred via sterile pipette to a new 125 mL shaker flask. After adding the appropriate volume of supplemented EX-CELLTM MDCK serum-free medium for a total volume of 50 mL, the shaker flask is placed on an orbital shaker (100-110 RPM). Cells are maintained undisturbed at 37° C. in the incubator with 10% CO 2 for a seven day period. This process can be repeated once every 4-10 days to maintain cells constantly. The following data is representative of serial passages for continuous cell growth. Passages 1-16 occurred weekly, and passages 17-34 occurred every four days.
• aCLDK cells were taken out of storage in liquid nitrogen and were grown in a 75 cm 2 flask for approximately 48 hours using 10% FBS in Eagle's Minimum Essential Medium (EMEM). The cells were then transferred to an 850 cm 2 roller bottle with 5% Fetal Bovine Serum and EMEM media. This roller was then trypsinized; cells were harvested and planted into two different 125 ml shaker flasks at a cell density of 5.0 ⁇ 10 5 cells/mL. Of these two flasks, one flask contained supplemented EX-CELLTM MDCK serum-free medium and the other flask contained EMEM medium.
• EX-CELLTM MDCK serum-free medium the other flask contained EMEM medium.
• a third flask containing sCLDK-SF cells (from an available continuous stock) were planted at a cell density of 5.0 ⁇ 10 5 cells/mL in supplemented EX-CELLTM MDCK serum-free medium. The three suspension flasks were then placed on an orbital shaker in a 37° C. water jacketed incubator and sampled daily (see results below) for cell and viability counts.
• aCLDK cells in EMEM medium do not grow in suspension culture.
• the data also shows that aCLDK in supplemented EX-CELLTM MDCK serum-free medium do not grow at a sufficient rate to be considered a viable alternative for production. Typically a growth factor of at least 5 is required to be considered useful for production. Instead, these cells simply maintained their cell density and viability.
• the sCLDK-SF cells in supplemented EX-CELLTM MDCK serum-free medium grow very well serum free in suspension with an average split ratio above 10 and maintain a high (>99%) viability.
• both tissue flasks were observed under microscope and found to be 90-100% confluent. Both flasks were trypsinized and cells were transferred to appropriate 490 cm 2 roller bottles and placed in a total volume of 150 mL of media/roller bottle. Both rollers were placed onto a roller cart (0.3 rpm) in a 35° C. incubator. Three days later, cells in both roller bottles were observed microscopically and found to be 30% confluent. Another three days later, cell and viability counts were performed. The cells in the MEMH were found to contain 1.02 ⁇ 10 7 cells/mL that were 99.5% viable.
• the cells in the supplemented EX-CELLTM MDCK serum-free medium with 5% FBS were found to contain 1.09 ⁇ 10 7 cells/mL that were 99.83% viable. Both roller bottles were trypsinized and cells were passed into new 490 cm 2 roller bottles at a cell density of 3.16 ⁇ 10 5 cells/mL and placed in a total volume of 150 mL of media/roller bottle. Both rollers were placed into a 35° C. incubator.
• the material in the Hanks MEM was found to contain 2.00 ⁇ 10 5 cells/mL (corresponding to a growth factor of 0.63) with 95.0% of the cells being viable.
• the material in the supplemented EX-CELLTM MDCK serum-free medium with 5% FBS was found to contain 3.03 ⁇ 10 6 cells/mL (corresponding to a growth factor of 9.58) with 99.8% viable of the cells being viable.
• the CLDK cells in the supplemented EX-CELLTM MDCK serum-free medium with 5% FBS medium were then planted in a new 125 mL shaker flask at a cell density of 3.16 ⁇ 10 5 cells/mL and placed on an orbital shaker in 35° C. incubator to determine whether the cells would continue to grow and placed in a total volume of 50 mL of media/shaker flask.
• CLDK cells in the supplemented EX-CELLTM MDCK serum-free medium with 5% FBS media were found to contain less than 1.5 ⁇ 10 5 cells/mL.
• the viability count could not be performed with the nucleocounter because values were too low. Visually, cells were very clumpy, and the cell culture was discarded.
• the sCLDK-SF cell line was infected with Canine flu (CIV, A/canine/Miami/05), a cold-adapted temperature sensitive H3N8 influenza (A/equine/2/Kentucky/1/91, described in U.S. Pat. No. 6,177,082, which is hereby wholly incorporated by reference), and a third H3N8 influenza virus (KY02, equine/Kentucky/02).
• CIV Canine flu
• A/canine/Miami/05 cold-adapted temperature sensitive H3N8 influenza
• KY02 equine/Kentucky/02
• all three harvested viruses tested returned positive HA results, with CIV and KY02 showing a significant amount of titer. Titer data was not collected for the cold-adapted temperature sensitive H3N8 influenza virus tested.
• sCLDK-SF cells were grown in supplemented EX-CELLTM MDCK serum-free medium prior to planting, most typically for 5-7 days.
• Cells were harvested from shaker flasks and planted at desired densities (1.0 ⁇ 10 6 cells/mL), in supplemented EX-CELLTM MDCK serum-free medium media at 50.0 mL per shaker flask (one flask per each virus) and incubated at 37° C. on a shaker orbital with 10% CO 2 .
• shakers were infected with appropriate virus and multiplicity of infection (MOI), see table below. Trypsin is added, 1 mL per liter (50 microliters per 50 mL).
• CIV and KY02 are incubated at 37° C., Flu-Avert at 34° C. Infected shaker flask(s) were observed daily and percent of infection was monitored and recorded. Daily samples were taken and frozen at ⁇ 70° C. to screen later for HA titer. Once it was determined that 90-100% of cells were infected, cells were harvested and frozen at ⁇ 70° C. Frozen samples were taken daily and tested for HA.

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