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Vaccination challenge studies with variants of street rabies virus isolated in Nigeria
A E Okoh1, J U Umoh, C D Ezeokoli
1University of Jos, Makurdi, Nigeria.
Abstract:
In a preliminary study it was observed that adult ICR mice immunized with serial dilutions of an inactivated experimental human rabies vaccine from the Pitman-Moore (PM) vaccine virus were well protected against challenge with homologous virulent PM virus and challenge virus standard (CVS). However only one of five variant representatives in five of seven groups of 41 isolates of street rabies virus from Nigeria characterized by hybridoma monoclonal antibodies specific for the nucleocapsid and glycoprotein antigens of rabies virion was protected for by the vaccine. Guinea pigs immunized with a live attenuated low egg passage (LEP, Flury strain) vaccine currently used in canine vaccination in Nigeria protected against challenge with all five variants. The LEP vaccine protected against the variants and CVS quite well even when 1:125 dilution of the vaccine was used.
Insights
An experimental human rabies vaccine protected mice against homologous virus but not Nigerian street rabies variants. A live attenuated canine vaccine (LEP) effectively protected guinea pigs against these variants.
Area of Science:
- Veterinary Virology
- Immunology
- Public Health
Background:
- Rabies remains a significant global health concern, necessitating effective vaccines.
- Street rabies virus strains, particularly from regions like Nigeria, can exhibit antigenic variations.
- Existing vaccines require evaluation against diverse circulating viral isolates.
Purpose of the Study:
- To assess the efficacy of an experimental inactivated human rabies vaccine (Pitman-Moore strain) against Nigerian street rabies virus variants.
- To compare the protective potential of the experimental vaccine with a live attenuated low egg passage (LEP) Flury strain vaccine.
Main Methods:
- Adult ICR mice were immunized with serial dilutions of an inactivated experimental human rabies vaccine (Pitman-Moore strain).
- Vaccinated mice and guinea pigs were challenged with homologous virulent rabies virus (PM virus), challenge virus standard (CVS), and five Nigerian street rabies virus variants.
- Viral isolates were characterized using hybridoma monoclonal antibodies targeting nucleocapsid and glycoprotein antigens.
Main Results:
- The experimental Pitman-Moore vaccine conferred excellent protection in mice against homologous PM virus and CVS.
- However, this vaccine showed limited protection against the Nigerian street rabies virus variants, with only one of five variants showing protection in some groups.
- In contrast, the live attenuated LEP vaccine effectively protected guinea pigs against all five Nigerian variants and CVS, even at a 1:125 dilution.
Conclusions:
- The experimental inactivated rabies vaccine may not provide broad-spectrum protection against diverse circulating street rabies virus strains.
- The live attenuated LEP vaccine demonstrates superior efficacy against antigenically varied rabies virus isolates, suggesting its potential utility in rabies control programs in Nigeria and similar regions.