Comparative efficacies of three commercially available vaccines against West Nile Virus (WNV) in a short-duration challenge trial involving an equine WNV encephalitis model.
We used a severe challenge model that produces clinical West Nile virus (WNV) disease to test the efficacy of three commercially available equine WNV vaccines in horses. Twenty-four healthy, WNV-seronegative horses of varying ages and genders were placed, in random and blind manner, into three trial groups consisting of eight horses each; two horses in each group received (i) an inactivated WNV vaccine (K-WN), (ii) a modified-live vaccine (CP-WN) containing the WNV prM and E proteins expressed by a canarypox vector, (iii) a live-chimera vaccine (WN-FV) containing WNV prM and E proteins expressed in a YF17D vector, or (iv) a diluent control. Challenge by this model caused grave neurological signs, viremia, moderate to severe histopathologic lesions in the brain and spinal cord, and an outcome of 0% survivorship in all six control horses. In contrast, challenge in horses at between 28 days postvaccination with the chimera vaccine and 56 days postvaccination with the commercial inactivated or modified-live vaccine resulted in 100% survivorship (protection from the onset of WNV encephalitis and viremia). Horses vaccinated with the live-chimera vaccine showed significantly fewer clinical signs than did the control horses (P </= 0.01) and the horses vaccinated with inactivated vaccine (P = 0.035). Mild residual inflammatory lesions were seen in a few of the vaccinated horses.
Seino
K K
KK
College of Veterinary Medicine, University of Florida, 2015 SW 16th Avenue, Gainesville, FL 32610, USA. seinok@mail.vetmed.ufl.edu
Long
M T
MT
Gibbs
E P J
EP
Bowen
R A
RA
Beachboard
S E
SE
Humphrey
P P
PP
Dixon
M A
MA
Bourgeois
M A
MA
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D006734:Horse Diseases / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D006736:Horses; D014901:West Nile Fever / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary* / Q000821:virology; D053060:West Nile Virus Vaccines / Q000008:administration & dosage / Q000276:immunology; D014902:West Nile virus / Q000276:immunology* / Q000302:isolation & purification
D000914:Antibodies, Viral; D053060:West Nile Virus Vaccines