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.
Rocke
Tonie E
TE
USGS National Wildlife Health Center, Madison, Wisconsin 53711, USA. trocke@usgs.gov
Pussini
Nicola
N
Smith
Susan R
SR
Williamson
Judy
J
Powell
Bradford
B
Osorio
Jorge E
JE
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