Testing for Human Cytomegalovirus
5th December 2013
By: Dr Daniel Galbraith, CSO
Human cytomegaloviruses (and simian) are members of a virus family that are specifically identified by the biologics safety guidelines as a specific concern. Most recently the 2010 FDA guidelines for testing of vaccine cell substrate included a recommendation that if there is the possibility of contamination with Human and Simian cytomegalovirus then the in vitro assay should be a minimum of 28 days long with the possibility that this should be passaged for a further period of time. Cytomegaloviruses are singled out for this as they are known to have a slow growth rate using in vitro culture in contrast to the vast majority of other viruses that are detected during cell culture over a much shorter period, often less than 5 days. The advent of Polymerase Chain Reaction (PCR) and Next Generation Sequencing (NGS) technologies has raised the possibility of detecting this family of viruses using a shorter assay and/or to improve the sensitivity of the methods to detect the virus. Recently at the FDA/PDA conference in Washington Dr Seimon Ng a scientist working at Sanofi Pasteur presented a very interesting research project to improve the detection of hCMV in samples. The study contrasted the in vitro detection of the virus on MRC-5 cells with the molecular techniques of PCR and NGS. The results of the study showed conclusively that the molecular techniques were more sensitive at the detection of virus than the in vitrocytopathic method [the in vitro method having a Detection Limit of 10 infectious units and requiring up to 28 days for detection whereas the molecular techniques were able to push the sensitivity to 1 infectious unit and in addition was able to detect 10 infectious units without cultivation]. Therefore moving forward it is clear from this data that to improve the sensitivity of the current method of detection of hCMV there should be a sensitive molecular detection of the virus at the end of the in vitrocultivation. At BioOutsource we offer in vitro cultivation methods for the detection of Human and Simian cytomegalovirus as well as sensitive PCR methods for the specific detection of these viruses. We would propose that all studies used for the detection of hCMV would include a PCR end point to detect the virus on MRC-5 cells harvested at the end of the in vitro cultivation period.