cultivation of virus | microbiology

Cultivation of virus

Viruses are obligate intracellular parasites. For their survival, they depend on host. They don’t have capability to grown in non-living culture media or on agar plates alone, they need living cells to support their replication.

The primary purpose of virus cultivation is:

1: To identify and isolate viruses in clinical samples.

2: For research on viral structure, replication, genetics and effects on host cell. 

3: For preparing viruses to produce vaccine.

Viruses can be cultivated by following ways

•  Animal Inoculation 
• Inoculation into embryonated 
• egg Cell Culture 

1. Animal  Inoculation

Viruses which are cultivated in laboratory animals such as mice, guinea pig, hamster, rabbits and primates are used. The selected animals must be healthy and must not have any communicable diseases. Most commonly suckling mice (less than 48 hours old) are used. Suckling mice are vulnerable to coxsackie and togavirus viruses, which are inoculated by intranasal and intracerebral route. Viruses can also be inoculated by subcutaneous and intraperitoneal route. Viruses multiply in host and develop disease, after inoculation. The animals are noticed for symptoms of disease and death. Then from the tissue of these animals, the virus is isolated and purified. For the study of yellow fever virus, live inoculation was first used on human volunteers. 

2. Inoculation into embryonated egg

Good pasture first made use of the embryonated hen’s egg for the virus cultivation in 1931. Cultivation in embryonated eggs depends on egg type which is used. Chick embryo of 7-12 days old is used for virus inoculation. Viruses are inoculated in these eggs. for inoculation, eggs are made prepare for cultivation. First with iodine the shell surface is disinfected and then penetrated with a small sterile drill.. After inoculation, the opening is sealed with paraffin or gelatin and incubated at thirty-six degree for two to three days. After incubation, the egg is broken, and virus is isolated from egg tissue. growth of virus and its multiplication in the egg embryo is revealed by embryo cell damage, by the death of the embryo, or by the formation of typical pocks or lesions on the egg membranes.

3. Cell Culture (Tissue Culture)

Cultures are mainly done for highly specialized parasites of particular organs. For example, for isolation of coronavirus, tracheal ring culture is done.