Characterization of Antigenic Sites on the Rinderpest Virus N Protein Uusing Monoclonal Antibodies

The N protein of the rinderpest virus (RPV) was analyzed topologically and antigenically by using anti-N monoclonal antibodies (Mabs). Ten Mabs were raised against the N protein of the RPV. At least six non-overlapping antigenic sites (sites A-F) were delineated by competitive binding assays using biotinylated Mabs. Of them 5 sites (A, C, D, E and F) on the N protein were recognized by RPV-specific Mabs in ELISA and IFA while site B was recognized by Mabs reacting with both RPV and PPRV. Non- reciprocal competition was found among sites C, D and E. Recombinant RPV N protein after exposure to 0.2% SDS exhibited higher ELISA titers in all Mabs recognizing 6 sites. Four sites (A, B, E and F) on 2% SDS-treated N protein lost completely reactivity with Mabs while the remaining sites (C and D) on the protein retained their antigenicity to some degree. It indicates that two sites (C and D) were sequential. Six representative Mabs bound to each site exhibited competition with rinderpest antibodies in a blocking ELISA, indicating that the sites were actively involved in antigenicity in cattle.

Characterisation of rinderpest virus RNA and the action of actinomycin D on its replication.

RNA extracted from purified rinderpest virus was characterised by sucrose gradient sedimentation and polyacrylamide gel electrophoresis. The predominant virion RNA species had a sedimentation constant of 46S and its estimated molecular weight was 4·8 × 106 daltons. Consistently high amounts of UMP and AMP were detected. The melting-temperature profile of the virion RNA suggested absence of secondary structure. The effect of actionomycin D on the replication of rinderpest virus in Vero cells was studied by following the viral RNA synthesis using labelled uridine as well as by infectivity titration. The viral RNA synthesis was not affected until 12 h following infection and was inhibited thereafter between 18 and 48 h to an extent of 25% at 5 and 10 μg levels of the drug. A 100 to 1000-fold reduction in the infectivity titres was observed in the presence of the drug. These results suggest that actinomycin D inhibits rinderpest viral RNA replication. Sedimentation analysis of viral RNA extracted from drug-treated cultures showed inhibition of the genome RNA of rinderpest virus.