Detection of growth in cell culture
A. Cytopathic effect
- Many viruses produce morphological changes in the cells in which they grow. These are called as cytopathic effects.
- Rounding and degeneration of cells: picornaviruses
- Rounding and aggregation of cells: adenoviruses
- Syncytium formation: measles virus, RSV
- Inclusion bodies: intracellular or intranuclear aggregates of products of viral replication.
- Nucleus: herpes virus
- Cytoplasmic: poxvirus, rabies virus
- Both: measles virus, CMV
Some orthomyxoviruses and paramyxoviruses code for red cell agglutinins that are incorporated in the host cell membrane during infection. When erythrocytes are added to the infected cell layer, they adhere to the surface of the infected cells. This is called as hemadsorption.
The growth of the non cytopathogenic virus in cell culture can be detected by subsequent challenge with a known cytopathogenic virus. The growth of the first virus will inhibit the infection with the second virus by interference.
Oncogenic viruses induce cell transformation, so that growth of cells appears in the piled up fashion due to the formation of micro tumors
Cells from virus infected cultures can be staining with fluorescent-conjugated antiserum and examined under UV light for detection of viral antigen. Most sensitive and specific method for detection of viruses in tissue culture.
Shell vial culture is a rapid modification of conventional cell cultures for viruses. The infected cell monolayer is stained for viral antigen using virus specific immunofluorescence conjugates, soon after infection before development of CPE. Viruses that take days to weeks to produce CPE can be detected within 1-2 days