Within the past 4-6 weeks, both GSK and Merck have reported finding fragments of the PCV virus in their rotavirus vaccines - Rotarix and Rotateg respectively. As a result, my colleague Misa Gray wrote a mini-primer on PCV testing in raw materials. I have extracted a portion that talks about the use of PCR for screening.
Porcine circovirus (PCV) is a member of the family, Circoviridae. it is a single-stranded, non-enveloped DNA virus. There are two strains PCV1 and PCV2. PCV1 is not known to cause any disease in pigs, while PCV2 does cause a disease known as Postweaning Multisystemic Wasting Syndrome (PMWS).
Photo courtesy Dr. Stewart McNulty.
The FDA suspended Rotarix usage on March 22,2010 due to finding PCV1 DNA in the vaccine. GSK confirmed the presence of the virus in Rotarix. Trypsin was a suspected possible source of the virus (unconfirmed). The source of the PCV remains under investigation by GSK and the FDA.
Raw materials, like trypsin, could be assessed for PCV presence by PCR testing assuming one can get a reasonable DNA preparation. Nested PCR (two sets of primers) could be utlized in cases where inhibiting materials might be present in the raw material sample. Multi-plex PCR ca nbe applied to test both for PCV1 and PCV2 simultaneously - this of course requires two independent set of primers.
Several commercial labs offer PCV2 screening - presumably due to its potential impact on animal health and the food chain. PCV1 is not normally offered by these same commercial test labs. Since the PCV1 sequence has been publoished and is available in GenBank, we believe that it would be relatively straightforward to develop a screening assay.
For more on PCV, see the FDA site.