The effects of formalin on the infectivity and immunogenicity of vesicular stomatitis virus (VSV) serotype Indiana were investigated. We found that formalin inactivation of VSV prevents infection of Vero cells in a concentration- and time-dependent manner, as shown by fluorometric cell analysis and inhibition of plaque formation. Inactivated VSV failed to induce significant cytotoxic T-lymphocyte responses in vivo or after restimulation in vitro. In contrast, the early immunoglobulin M (IgM) ...