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

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Abstract
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.