Cultivation of Viruses
Virus multiply only in living cells.
They can't grow on any artificial culture medium.
Methods used for cultivation of Viruses
1. Animal Inoculation
2. Chicken embryo (fertilized Hen's egg)
3. Tissue culture
1. Animal Inoculation
Monkey, mice (infant), Guinea pig and rabbit used for virus isolation.
After inoculation, animals are observed for signs of disease of death.
The growth of virus is inoculated animals may be indicated by its death, disease or visible lesion in animal tissue.
Advantage
It is used for study of Viruses and immune response.
Note; Laws forbid use of animal for experimental purpose.
2. Embryonated egg Inoculation
Embryonated Hen's eggs are inoculated with infected material using pressure syringes.
The opening is sealed and eggs are incubated.
They are observed at regular interval for growth of organism.
Advantages
Sites of cultivation of Viruses;
1. CAM (chick embryo chorioallantoic membrane) is incubated mainly for growing pox viruses inoculation.
It produce visible lesions.
2. Amniotic sac;
Inoculation into amniotic sac is mainly used for primary isolation of Influenza virus.
3. Allantoic activity
For growing influenza Viruses for vaccine production.
4. Yolk sac Inoculation
It is inoculated for cultivation of some virus and certain bacteria (for example; Chlamydiae, rickettsiae.
5. Yellow fever and Rabies vaccines are also made from chick eggs.
3. Tissue culture
In tissue culture, human or animal cells are used for cultivation of Viruses.
There are mainly three types of tissue culture;
1. Organ culture
2. Explant culture
3. Cell structure
1. Organ culture
Organs can be maintained in laboratory for few day or weeks.
Advantages
It is useful for isolation of some Viruses.
For example; tracheal ring organ culture is used for isolation of coronavirus pathogen of respiratory tract.
2. Explant culture
Rarely used in virology.
3. Cell culture
Commonly used method for cultivation of virus.
Tissue are split into cell.
Growth factor for virus are added.
Cell culture are classified into three types;
1. Primary cell culture
2. Diploid cell strains
3. Continous cell lines
Cell cultures in common use;
Type;
1. Primary cell culture
Normal cells, freshly taken from body and cultured.
Name of cell culture
Chick embryo fibroblast cell culture.
Rhesus monkey kidney cell culture.
Uses;
It is used for isolation of virus and for vaccine cultivation.
2. Diploid cell strains (single type cells)
Human embryonic lung cell strain
Rhesus embryo cell strain
For example; Human fibroblast
Uses; Used for isolation of fastidious pathogen and production of viral vaccines.
3. Continuous cell lines
Single type cell, which derived from cancer cells that are capable of continous uncontrolled growth.
Human carcinoma of cervix cell line.
Human larynx cell line.
Vervet monkey kidney cell line.
Human synovial carcinoma cell line.
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