Detection and characterization of pestivirus contaminations in human live viral vaccines

In view of the use of potentially contaminated foetal calf serum (FCS) in cell cultures pestiviruses may be present in live viral vaccines. Thirty-six lots of human live viral vaccines produced by three manufacturers were tested for the presence of pestiviruses. Bovine viral diarrhoea virus (BVDV) RNA was detected in 33% of the vaccine lots. All positive results were caused by the mumps component of a single manufacturer. Partial sequences of the 5' untranslated region of BVD viral RNA were determined. The sequences were closely related to that of the NADL strain of BVDV. The amount of BVDV RNA in the vaccines was determined by real-time RT-PCR using the LightCycler. Between 3.3*10(2) and 6.2*10(5) RNA copies per dose were found to be present in the vaccine samples.Additionally, culture tests were done with FCS and human diploid cells used in the vaccine production of the manufacturer whose vaccines were positive by PCR. All attempts to detect virus antigen in MRC-5 human diploid cells or to infect these cells with BVDV failed. This suggests that BVDV RNA detected in human live viral vaccines represents passive carry over of BVDV from contaminated FCS rather than active virus replication in human diploid cells. Our results indicate that contamination with BVDV of FCS used in vaccine production does not appear to be of immediate concern to human health. Furthermore, our results indicate that gamma-irradiation of FCS destroys BVDV particles and is also effective in preventing the presence of BVDV RNA in the vaccines.