What is Cell Culture?
Cell Culture began in the early twentieth century with whole organ cultures,then progressed to involving individual cells, either primary cell cultures or immortalized lines which continue to grow in a culture continually given the proper environment.
John Enders,in 1949, with his colleagues were able to grow a poliovirus in primary human cell cultures.This achievement led to what many refer to as the "Golden Age of Virology" and also to the identification and the isolation during the 1950s and 1960s of many viruses and their association with human diseases. Widespread virus isolation led to the realization that subclinical virus infections were very common. Even epidemics of the most violent strains of poliovirus there are approximately 100 subclinical infections for each paralytic case of poliomyelitis.
Applying a suitable dilution of a virus preparation to a confluent or semiconfluent sticky monolayer of susceptible cells is called a "plaque assay." After allowing time for virus attachment to and infection of the cells, the liquid medium is replaced by a semisolid culture medium containing a polymer such as algorose or carboxymethyl cellulose,that restricts diffusion of virus particles from infected cells. Then, only direct cell to cell spread can occur resulting in localized destruction of the monolayer.
After a suitable period, the medium is usually removed and the cells stained to make the holes in the monolayer more easily visable. Each plaque results from infection by a single certain circumstance. For example, viruses that do not replicate in culture or are not cytopathic and do not produce plaques. (ex.HIV human immunedeficiency virus).