Many cell lines undergo multiple passages in different laboratories. The history of such
lines is rarely recorded and thus the risk of cross-infection with infectious agents from
other cell lines and contaminated reagents cannot be assessed. For primary cells isolated
directly from tissue the risk of infection is related directly to contamination from the tissue
of origin (ie: microbiological status of the animal or colony of origin) and the culture
medium used. Probably the most likely organisms to pass between cell lines and establish
an infection are mycoplasmas and acholeplasmas. These organisms survive well in the
environment and unfortunately are commonplace in animal cell cultures and can be
extremely difficult to eradicate. Some of the most common contaminant species in cell
cultures (eg Mycoplasma orale, M. salivarum, M. hominus, M. fermentans) probably
originate from the commensal flora of laboratory workers and feotal bovine serum (Del
Giudice and Gardella, 1984). While mycoplasma infection can have drastic effects on
cells, the species identified in cell culture are not generally associated with human disease
except for M. pneumoniae. Thus, although the presence of adventitious agents can have
serious consequences for infected cell lines, they are unlikely to represent a serious health
threat to laboratory workers using good aseptic technique.
A more insidious problem, is the potential for cell lines to harbour and secrete virus while
showing no overt signs of infection. This unrecognised factor and the need to prevent the
spread of contaminants between cultures are the primary indicators for care in cell lines
containment (see below). The situation is simplified (in terms of risk assessment only)
when a hazardous virus is used to infect cells. The culture as a whole then assumes the
higher hazard level for the virus. Published literature and the experience of other workers
regarding a particular cell culture of interest may also be valuable in risk assessment.
However, direct transcription of specific data (eg virus testing) should be supported by
proof of the common origin of cells in use and those in the literature utilized in risk
assessment.
3) Cell products
Cell products naturally released from animal cell cultures do not usually represent a
hazard. Generally, this is a problem relating to direct exposure to purified products which
can be alleviated if direct exposure of the body surfaces and respiratory tracts of laboratory
workers is minimised. Cell products produced at high concentration, for example from
some recombinant organisms, demand a higher priority in risk assessments and should be
assessed for their toxic properties, persistence in the environment and their ability to cause
adverse immune reactions. The potential for exposure to transforming proteins, such as
E1A adenovirus protein and SV4 T antigen, is also an important consideration. It should be
borne in mind that scale-up procedures that are aimed to produce high and concentrated
yields of product may represent significant hazards which were of lesser consequence at
research and development stages. Control of products released inadvertently into the