Virus Cultivation Methods

Cultivation of Viruses

• Viruses, unlike bacteria, require a living host cell for replication.
• Infected host cells (eukaryotic or prokaryotic) can be cultured and harvested to produce virus.
• Virions can be separated from host cells through centrifugation or filtration.
• Filters remove larger particles than virions, allowing viruses to be collected in the filtrate.

Virus Cultivation Methods

• In vivo: Viruses can be grown within a whole living organism (animal, plant), or in an artificial environment.
• In vitro: Viruses can be grown in a test tube, cell culture flask, or an agar plate.
• Bacteriophages: Grown in a bacterial lawn (dense layer of bacteria) on a Petri dish. Plaque formation indicates areas where bacteriophages have lysed bacterial cells.
• Plaque Assay: Clear zones (plaques) in the bacterial lawn indicate where bacteriophages have replicated.

Animal Virus Cultivation

• Animal viruses require cells within a host animal or tissue culture cells derived from an animal.
• Animal virus cultivation is crucial for identifying and diagnosing pathogenic viruses, producing vaccines, and basic research.
• In vivo source examples: Embryonated bird eggs (chickens, turkeys) or whole animals.
• The embryo or animal functions as an incubator for viral replication.
• Specific tissue location is critical, as viruses have a tissue tropism requiring specific sites for growth.

In Vitro Culture of Viruses

• Primary cell culture: Freshly prepared from animal organs/tissues.
• Cells are released using mechanical scraping, mincing, or enzymes (trypsin, collagenase).
• Primary cells need a solid surface (glass, plastic) for attachment and growth.
• Primary cells have a limited lifespan.

In Vitro Culture of Viruses (cont'd)

• Secondary cell culture: Cells enter contact inhibition when their density becomes too high and growth must be sustained with transfer to a new medium and thus creating a secondary cell culture.
• Continuous cell lines: Derived from transformed cells/tumors, they can be subcultured repeatedly, growing indefinitely (immortal). A notable example is the HeLa cell line.

Assays for Virus Identification

• Hemagglutination Inhibition (HAI): Identifies specific viruses using an indirect method.
• Antibodies bind to virus components like hemagglutinins preventing erythrocytes from interacting directly with the virus.
• No agglutination indicates successful antibody binding to the viral components.

Explore the fascinating world of virus cultivation techniques. This quiz covers both in vivo and in vitro methods, including the specific procedures used for bacteriophages and animal viruses. Test your knowledge on how viruses are harvested and grown in various environments.