Recombinant vaccinia virus (RVV) containing the full-length cDNA of rinderpest virus (RV)-haemagglutinin (H) gene was constructed. The H gene was inserted into the attenuated vaccine strain of vaccinia virus (VV), Le 16 m0, with two different promoters, namely cowpox virus A-type inclusion body (ATI) promoter or VV 7.5 kilodalton (P7.5) promoter. These RVVs produced the same sized fully glycosylated RV-H protein in RK 13 cells as that of the authentic RV-H. Their heat stability in the lyophylized state was similar to that of the parental VV. All rabbits immunized with these RVVs produced virus neutralizing (VN) antibody to RV as well as anti RV-H antibody. Four weeks after immunization, these animals were challenged with RV intravenously. None of the RVV-immunized rabbits developed any clinical signs of RV infection except one which was immunized with RVV containing the ATI promoter and developed low VN titer. These results indicate the possibility of developing a heat-stable recombinant vaccine for the eradication of rinderpest in tropical countries without cold storage systems.

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We constructed a recombinant vaccinia virus (RVV) expressing rinderpest virus (RPV) hemagglutinin (H) by modifying the promoter region of the original RVV. The promotor region was modified at three points, i.e., an outframe ATG was eliminated, the sequence between the promoter and initiation codon was shortened and the base sequence just upstream of the initiation codon was changed. As compared with the original RVV, the modified RVV was found to produce a remarkably large amount of H protein in infected rabbit kidney cells cultured in vitro and to induce high titers of anti-RPV-H antibodies in rabbits. The median protective doses in rabbits of the modified and of the original RVVs were 10(2) pfu and 10(3.5) pfu, respectively, indicating that the modified RVV was at least 10-times more effective in protection than the original. The neurovirulence of the modified RVV and the parental LC16mO strain was roughly at the same level, and was much lower than that of WR strain. The modified RVV was as heat-stable as the original one. These results indicate that the modified RVV could be a candidate rinderpest vaccine for further examinations including cattle.