Effect of heterogeneity of rabies virus strain and challenge route on efficacy of inactivated rabies vaccines in mice.

OBJECTIVE To determine effect of route of challenge and strain of rabies virus on efficacy of inactivated rabies vaccines in mice. ANIMALS 3,056 mice. PROCEDURE Challenge was performed with fixed and street rabies virus strains by use of footpad and intracerebral routes as well as IM injection into the hip, shoulder, neck, and masseter muscles. Intraperitoneal and IM vaccination was performed with 1 or 2 doses of 1 of 3 vaccine-strain inactivated rabies vaccines. For 2 of the vaccine strains, the vaccines were adjuvanted and nonadjuvanted. RESULTS Incubation periods were dependent on route, dose, and virus strain used for challenge. Use of an intramasseter challenge route with challenge virus-strain rabies virus, which more accurately models natural exposure to rabies virus, resulted in reproducible mortality rates in mice. Use of this route revealed that differences among vaccines and challenge virus strains affected mortality rate less than that observed in the National Institutes of Health potency test, even when street isolates of widely variant origin were used for challenge. CONCLUSIONS AND CLINICAL RELEVANCE These results, combined with earlier data, support a proposal for a new rabies potency test that more closely models current vaccine administration practices and natural infection routes.