Stability of Rift Valley fever virus at 4 C.

The preparation of virus vaccines in monkey kidney tissue cultures may be complicated by the presence of adventitious agents in tissues of some of the animals (J. L. Bittle et al., J. Infect. Diseases 116:215, 1966). The problem is compounded when fluids derived from the cell cultures of several monkeys are pooled, since one contaminated animal would spoil the entire lot. This situation may be avoided if tests for adventitious agents are done prior to pooling the fluid harvests from each pair of monkey kidneys. During the development of production methods for formalin-inactivated Rift Valley fever (RVF) vaccine (R. Randall et al., J. Immunol. 89:660, 1962), studies were undertaken to determine the stability (infectivity and immunogenicity) of the RVF virus in tissue culture fluids stored at 4 C for 30 days while tests for adventitious agents were conducted. The 184th mouse passage of the pantropic RVF, Entebbe strain, described by K. C. Smithburn et al. (Brit. J. Exptl. Pathol. 29:107, 1948),