Abstract
A DNA vaccine for West Nile virus (WNV) was evaluated to determine whether its use could protect fish crows (Corvus ossifragus) from fatal WNV infection. Captured adult crows were given 0.5 mg of the DNA vaccine either orally or by intramuscular (IM) inoculation; control crows were inoculated or orally exposed to a placebo. After 6 weeks, crows were challenged subcutaneously with 105 plaque-forming units of WNV (New York 1999 strain). None of the placebo inoculated–placebo challenged birds died. While none of the 9 IM vaccine–inoculated birds died, 5 of 10 placebo-inoculated and 4 of 8 orally vaccinated birds died within 15 days after challenge. Peak viremia titers in birds with fatal WNV infection were substantially higher than those in birds that survived infection. Although oral administration of a single DNA vaccine dose failed to elicit an immune response or protect crows from WNV infection, IM administration of a single dose prevented death and was associated with reduced viremia.
Highlights
A DNA vaccine for West Nile virus (WNV) was evaluated to determine whether its use could protect fish crows (Corvus ossifragus) from fatal WNV infection
Serologic Response While neutralizing antibodies developed in 5 of the 9 fish crows that received the vaccine by the IM route at the 80% neutralization level for WNV by 14 days after vaccination, neutralizing antibodies to WNV did not develop in any of the remaining fish crows (8 orally exposed to vaccine and 20 placebo-exposed) in the same time period (Table 1)
A veterinary pathologist examined all crows that died during these studies, and signs typical of WNV infection in avian hosts were observed in all of these birds. (These data will be described in a separate article on WNV viral pathogenesis in fish crows.) Viremias were detected in all 10 crows that received the placebo inoculation, 7 of 8 fish crows that received the oral vaccine, and 6 of 9 fish crows that received the vaccine by the IM route (Table 1)
Summary
A DNA vaccine for West Nile virus (WNV) was evaluated to determine whether its use could protect fish crows (Corvus ossifragus) from fatal WNV infection. While none of the 9 IM vaccine–inoculated birds died, 5 of 10 placebo-inoculated and 4 of 8 orally vaccinated birds died within 15 days after challenge. Oral administration of a single DNA vaccine dose failed to elicit an immune response or protect crows from WNV infection, IM administration of a single dose prevented death and was associated with reduced viremia. Vaccination may protect birds from lethal WNV infections. We examined a DNA vaccine developed for use in horses [13] for its ability to protect crows, a species known to be highly susceptible to lethal infection with this virus [8,10]
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