Types of tissue culture in Virology

Primary tissue culture: this is made directly from tissue. It may involve one or two

passage. In primary tissue culture, there are mixed cell types. It is good for isolation of

influenza virus, parainfluenza virus and enteroviruses. Three types are recognized:

monolayer, suspension and organ culture.

a. Monolayer: derived from tissue taken directly from the susceptible host (monkey

kidney, mouse embryo). The tissue is cut into very small pieces and digested into cells

by proteolytic enzymes such as trypsin or collagenase. The cells are grown on glass or

plastic surface as monolayer in as artificial medium containing growth factors

supplemented with foetal calf serum and antibiotics.

Type of artificial medium:

 Growth medium: for cell cultivation. Its constituents include salts at physiological

concentration, glucose, amino acids, vitamins, antibiotics and antifungal agents and 10-

20% foetal calf serum. It is maintained at pH 7.2-7.4. After formation of confluent

monolayer, the growth medium is changed to maintenance medium.

 Maintenance medium: contains similar constituents as growth medium except that the

foetal calf serum is 2 -5% for survival of cells and no further division.

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b. Suspension culture: cells are grown in form of suspensions in growth medium and not

monolayer. Lymphocyte cultures are cultivated in suspension.

c. Organ culture: organ culture are not trypsinized into cell but grown as whole. Examples

include tracheal ring organ culture.

Secondary culture: they are obtained from primary culture by passages or subcultivation.

Repeated passages of primary culture will produce cell lines with almost homogenous

cell type. Types of secondary culture include semi continuous cell line and

continuous/established cell line.

a. Semi continuous cell line: this is derived from fibroblastic cell of animal or human foetal

tissue. They have been subcultured through about 50 passages (generations of repeated

subcultivation). They have diploid number of chromosome. They are used for vaccine

production. They have limited life span. Examples include HDCS, MRC-9, WI-38. This

type of cell culture is good for herpes simplex and rhinovirus.

b. Continuous cell line: this is also called established cell line. Hey are widely used fro

diagnostic purposes. They are derived from neoplastic cells or from normal cells that

have been transformed by repeated subcultivation to behave like tumour cells.

Continuous cell line can grow indefinitely. They have heteroploid (aneuploid)

chromosome (variable/abnormal number of chromosome). It is good for vaccine

production and research purposes. Examples include Mardin Darby bovine kidney

(MDBK), MDCK, Vero cell (African green monkey kidney cells), Hep, HeLa, Crandell feline

kidney (CRFK).