cell culture best practices - virus immortalized and non-immortalized cells (Apr/29/2009 )
My question has to do with cell culture best practices.
I thought that it was always a bad practice to culture virus transformed (immortalized) cell line(s) and non-transformed cells in the same culture laboratory or, at least in the same incubator. This is because of the possibity of cross contamination of the virus from the transformed cells to the non-transformed cell line(s). This contamination might lead to a transformation of the previous normal replicating
Because recombinant methods are evolving, I suppose it is possible to construct a viral vector that cannot be unintentionally transferred
to another cell line. But, I do not think that this is yet a normal practice.
Any comments would be appreciated.
Ordinary cell culture lines, are pretty much all transformed unless they are true primary cell lines. Some of these will have been transformed by virus, others by mutation of a variety of genes, but they are all immortalised. Infecting these cells with virus will not affect how "much" they are transformed, as they will survive without the aid of a virus. Viral transformation of a normal cell type (i.e. primary cells) happens at a very low frequency (less than 10-5 chances per cell) and requires a number of steps to take place, the first of which is the virus inserting itself into the genome of the host, and some of the viral proteins being expressed (e.g E1b55k for adenovirus) that inhibit the action of p53 and Rb. Even then the cell will not immortalise, it still needs a telomere mainentance mechanism to be activated so that the DNA doesn't get all mixed up and unreadable due to unregulated recombination events
The vast majority of cells that are virally transformed do not shed any virus, and are surprisingly common. Common ones you might have come across include HeLa, HepG2, Hep3B, and HEK293. Most cervical cancer lines are transformed by HPV, and most liver ones by hepatitis. There is some evidence that viruses mediate about 15% of the total cancers incidence worldwide.
It is fine to culture cells that do not shed live virus in the same incubator as other cell lines, ones that do shed should of course be kept in separate incubators and with appropriate conditions to ensure that you don't infect your other cells.
Edited to add: you should of course quarantine any cell lines that you get into the lab to ensure that they aren't infected with anything, not just viruses.