Cross-Reactivity and Cross-Protection: Rabies Variants and Rabies-Related Viruses

Summary

Antigenic differences among strains of rabies virus can be easily detected using a panel of monoclonal antibodies (MCAb) directed against the nucleocapsid (NC) and glycoprotein (GP) antigens of the virion. It is possible, using a limited panel of anti-NC MCAb, to distinguish the rabies-related viruses (Mokola, Lagos bat, Duvenhage) from true rabies virus strains and to identify each of the rabies-related viruses.

Mice immunized intraperitoneally with inactivated rabies vaccine (Pasteur-derived strain) were only partially protected when challenged with field isolates whose antigenic compositions differed markedly from that of the vaccine strain. The epitope site III of the rabies virus GP appears to be the major antigen responsible for protection. No difference in protection, however, could be demonstrated in guinea pigs immunized and challenged intramuscularly.

Mokola virus isolated during an epidemic in Bulawayo, Zimbabwe, was neutralized by two MCAb derived from mice immunized against Mokola virus, but not by 42 MCAb that neutralize rabies virus strains. Mokola virus, however, was neutralized with polyclonal anti-Mokola serum and to a lesser extent, by three high-titer anti-rabies sera. Immunization of mice with a rabies vaccine at a concentration 30-fold higher than that required for complete protection against homologous challenge with rabies virus was not protective against Mokola infection. No crossreact-ivity between Mokola and rabies was seen with cytotoxic T lymphocytes.