Calf serum content of various viral vaccines and possibilities for its reduction

Abstract

A total of 26 inactivated or live virus vaccines obtained from different sources and prepared on different cell cultures were examined, by a semiquantitative procedure of immunoprecipitation, for their concentrations of calf serum albumin and calf serum globulin. The highest serum protein concentrations (≈ 2 to > 10 μg/ml) were found in single (first) harvest vaccines from large enveloped viruses. The serum content of single harvest vaccines from small, naked viruses was intermediate (< 1–2 μg/ml) and lowest for multiple harvest or single second harvest vaccines (usually < 1 μg/ml). Using a similar evaluation system the effectiveness of different washing and refeeding procedures for the removal of serum proteins from cultures of permanent monkey cells was studied. The conventional washing procedures proved rather ineffective even if the washing fluid was kept on the cells for a prolonged period. Serum proteins could be almost completely removed only by refeeding the cell cultures once for 24 h with serum-free medium. It was concluded from these results that serum proteins (especially the globulin fraction) are adsorbed onto the cells and possibly also onto the surface of larger, enveloped viruses and are not completely removed by the conventional washing procedures. The importance of the contamination of vaccines with residual calf serum for evoking allergic reactions and the possibility of eliminating such serum from vaccines are discussed briefly.