Abstract
Oral rabies vaccination (ORV) is highly effective in foxes and raccoon dogs, whereas for unknown reasons the efficacy of ORV in other reservoir species is less pronounced. To investigate possible variations in species-specific cell tropism and local replication of vaccine virus, different reservoir species including foxes, raccoon dogs, raccoons, mongooses, dogs and skunks were orally immunised with a highly attenuated, high-titred GFP-expressing rabies virus (RABV). Immunofluorescence and RT-qPCR screenings revealed clear differences among species suggesting host specific limitations to ORV. While for responsive species the palatine tonsils (tonsilla palatina) were identified as a main site of virus replication, less virus dissemination was observed in the tonsils of rather refractory species. While our comparison of vaccine virus tropism emphasizes the important role that the tonsilla palatina plays in eliciting an immune response to ORV, our data also indicate that other lymphoid tissues may have a more important role than originally anticipated. Overall, these data support a model in which the susceptibility to oral live RABV vaccine infection of lymphatic tissue is a major determinant in vaccination efficacy. The present results may help to direct future research for improving vaccine uptake and efficacy of oral rabies vaccines under field conditions.
Highlights
Oral rabies vaccination (ORV) is highly effective in foxes and raccoon dogs, whereas for unknown reasons the efficacy of ORV in other reservoir species is less pronounced
While our comparison of vaccine virus tropism emphasizes the important role that the tonsilla palatina plays in eliciting an immune response to ORV, our data indicate that other lymphoid tissues may have a more important role than originally anticipated
We focused on the red fox as the species, which is very responsive to oral rabies vaccination
Summary
Oral rabies vaccination (ORV) is highly effective in foxes and raccoon dogs, whereas for unknown reasons the efficacy of ORV in other reservoir species is less pronounced. While our comparison of vaccine virus tropism emphasizes the important role that the tonsilla palatina plays in eliciting an immune response to ORV, our data indicate that other lymphoid tissues may have a more important role than originally anticipated Overall, these data support a model in which the susceptibility to oral live RABV vaccine infection of lymphatic tissue is a major determinant in vaccination efficacy. While wildlife rabies in Eurasia is mainly associated with foxes and raccoon dogs[3], in the Americas, raccoons and skunks both serve as major reservoir species and potent transmitter of the disease to domestic animals[4] Another important reservoir in the Caribbean and Southern Africa are mongooses[5]. Despite the broad application of oral rabies vaccines over the last decades, it is still not fully understood if and where oral rabies vaccine viruses replicate in the oral cavity of the target species
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