[Enhancement of alphavirus reproduction in cell cultures at an alkaline pH]

Replication of different alphaviruses, among them Semliki Forest, Sindbis, and Venezuelan equine encephalomyelitis viruses, was studied in chick embryo fibroblasts and hamster BHK cells at different pH in a range of 6.8 to 7.9. Incubation of the infected cell cultures in a mild alkaline medium (pH 7.5-7.9) resulted in a marked activation of both one-cycle and multi-cycle reproduction of the alphaviruses under study as compared with that in the neutral medium (pH 6.8-7.2). At an alkaline pH, the rate of amplification and level of synthesis of viral proteins in the infected cells increased markedly, while virus adsorption on cell receptors decreased by 30-50%. It is recommended to use nutrient media with mild alkaline pH for stabilization of alphaviruses reproduction in cell cultures.