Porcine Circovirus Detection by q-PCR
Recent press releases reported the presence of Porcine circovirus Type-1 & 2 (PCV-1 & PCV-2) DNA in two Rotavirus vaccines. One of the companies confirmed its presence in both the Vero cell bank used and the virus seed from which the vaccine is derived, suggesting its presence from the early stages of vaccine development.
 
PCV is a single stranded DNA virus that is non-enveloped with a non-segmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. It is robust and difficult to remove or inactivate by physico-chemical means. Studies have shown that the virus is resistant to low pH and gamma irradiation treatment (1). Members of the Circoviridae have been identified in cattle, dogs and cats.
 
Human cell lines can be infected with porcine circovirus type 1&2. Infection of PCV1 was observed with HEK 293 & HeLa cells. PCV1 replicates well in PK15 cells. PCV1 can persist in cell lines without causing any visible changes, while PCV2-transfected cells can show a cytopathogenic effect. PCV contamination could possibly occur from the use of porcine trypsin in a cell lines history, since most cell lines have been exposed to this reagent. The screening of all such cell substrates used for manufacture of clinical material is recommended.
 
To assist biotech companies in ensuring the absence of PCV-1 and PCV-2 and Bovine Circovirus (BCV) Vitrology’s team of QPCR experts offer a highly sensitive, fully validated, cGMP compliant, nucleic acid based test capable of sensitively detecting PCV-1, PCV-2 and BCV in biological samples.

Infectivity studies on SPF pigs and testing for sero-conversion/PCR would be the most sensitive assay route for PCV-1 and PCV-2 detection. Other potential viruses are of particular concern as they are often present in porcine material and can contaminate any material exposed to porcine products, such as porcine trypsin.

Such PCV Infectivity assays on SPF pigs or on cell lines can also be proposed.

1 - Plavsic, Z. Mark, Bolin, Steve. “Resistance of porcine circovirus to gamma irradiation.” BioPharm International, April 2001.

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