Consumption of baits containing raccoon pox-based plague vaccines protects black-tailed prairie dogs (Cynomys ludovicianus).
Baits containing recombinant raccoon poxvirus (RCN) expressing plague antigens (fraction 1 [F1] and a truncated form of the V protein-V307) were offered for voluntary consumption several times over the course of several months to a group of 16 black-tailed prairie dogs (Cynomys ludovicianus). For comparison, another group of prairie dogs (n = 12) was injected subcutaneously (SC) (prime and boost) with 40 microg of F1-V fusion protein absorbed to alum, a vaccine-adjuvant combination demonstrated to elicit immunity to plague in mice and other mammals. Control animals received baits containing RCN without the inserted antigen (n = 8) or injected diluent (n = 7), and as there was no difference in their survival rates by Kaplan-Meier analysis, all of them were combined into one group in the final analysis. Mean antibody titers to Yersinia pestis F1 and V antigen increased (p < 0.05) in the vaccinated groups compared to controls, but titers were significantly higher (p < 0.0001) in those receiving injections of F1-V fusion protein than in those orally vaccinated with RCN-based vaccine. Interestingly, upon challenge with approximately 70,000 cfu of virulent Y. pestis, oral vaccination resulted in survival rates that were significantly higher (p = 0.025) than the group vaccinated by injection with F1-V fusion protein and substantially higher (p < 0.0001) than the control group. These results demonstrate that oral vaccination of prairie dogs using RCN-based plague vaccines provides significant protection against challenge at dosages that simulate simultaneous delivery of the plague bacterium by numerous flea bites.
USGS National Wildlife Health Center, Madison, Wisconsin 53711, USA. trocke@usgs.gov
Tonie E
TE
Rocke
Nicola
N
Pussini
Susan R
SR
Smith
Judy
J
Williamson
Bradford
B
Powell
Jorge E
JE
Osorio
D000284:Administration, Oral; D000818:Animals; D000835:Animals, Wild; D000907:Antibodies, Bacterial / Q000097:blood*; D005260:Female; D053208:Kaplan-Meier Estimate; D008297:Male; D010930:Plague / Q000517:prevention & control / Q000662:veterinary*; D010931:Plague Vaccine / Q000008:administration & dosage*; D011212:Poxviridae / Q000276:immunology; D011821:Raccoons / Q000821:virology; D012376:Rodent Diseases / Q000401:mortality / Q000517:prevention & control*; D012589:Sciuridae / Q000276:immunology*; D014611:Vaccination / Q000662:veterinary; D015010:Yersinia pestis / Q000276:immunology / Q000472:pathogenicity
D000907:Antibodies, Bacterial; D010931:Plague Vaccine