Inhibition of transcription by immunoglobulins directed against the ribonucleoprotein of homotypic and heterotypic vesicular stomatitis viruses.

Specific antisera were raised by immunization of rabbits with purified nucleocapsids containing only RNA and N protein (ribonucleoprotein, RNP) obtained from vesicular stomatitis (VS) virions of the Indiana (VSInd) and the New Jersey (VSNJ) serotypes. The specificity of anti-RNPInd serum was demonstrated by selective precipitation of homotypic RNPInd devoid of L and NS proteins; anti-RNPInd serum also selectively precipitated soluble N protein present in cytoplasm of infected cells, but co-precipitated a limited amount of contaminating soluble NS protein. Immunoglobulins prepared from each homotypic antiserum markedly inhibited in vitro transcription of VSInd and VSNJ virions. Anti-RNPInd and anti-RNPNJ immunoglobulins also exhibited cross-reactivity by inhibiting transcription of heterotypic virions, but only to a much lesser degree than in the homotypic reaction. Anti-RNPInd immunoglobulin did not inhibit transcription of the antigenically unrelated Chandipura rhabdovirus, but anti-RNPNJ immunoglobulin did to a very limited extent. The transcription inhibitory activity of anti-RNPInd immunoglobulin was not dependent on RNP immunoprecipitation activity, which could be diluted out well before loss of antitranscriptase activity. Anti-RNPind immunoglobulin appeared to exert its effect on transcription by blocking elongation rather than initiation or reinitiation of RNA transcripts.