The effect of gold sodium thiomalate and its constituent part, thiomalate, on the virus titres and the lysosomal enzyme activity in peritoneal macrophages of Swiss/A2G mice infected with the avirulent strain of Semliki Forest virus.

Treatment of adult mice with gold sodium thiomalate made the normally non-lethal Semliki Forest virus infection lethal. Associated with this was a significant increase in brain virus titre and a depression of peritoneal macrophage lysosomal enzyme activity. In contrast, treatment of adult mice with the constituent part, thiomalate, did not make the non-lethal Semliki Forest virus infection lethal. Brain virus titre and peritoneal macrophage lysosomal enzyme activity were comparable to the controls. The mechanism by which gold sodium thiomalate increases the virulence of Semliki Forest virus is discussed.