DNA Vaccination of the American Crow (Corvus brachyrhynchos) Provides Partial Protection Against Lethal Challenge with West Nile Virus

Abstract

The New York 1999 strain of West Nile virus (WNV) is nearly 100% fatal in the American crow (Corvus brachyrhynchos). We evaluated four WNV vaccine formulations in American crows, including intramuscular (i.m.) DNA vaccine, i.m. DNA vaccine with adjuvant, orally administered microencapsulated DNA vaccine, and i.m. killed vaccine. Neutralizing antibodies developed in approximately 80% of crows that received the DNA vaccine i.m. (with or without adjuvant), and in 44% that received the killed vaccine. However, no crows that received the oral microencapsulated DNA vaccine or the placebo developed WNV antibodies. All crows were challenged 10 wk after initial vaccination. No unvaccinated crows survived challenge, and survival rates were 44% (i.m. DNA vaccine), 60% (i.m. DNA vaccine with adjuvant), 0% (oral microencapsulated DNA vaccine), and 11% (killed vaccine). Peak viremia titers in the birds that survived were significantly lower as compared to titers in birds that died. Parenteral administration of a WNV DNA vaccine was associated with reduced mortality but did not provide sterile immunity.

Efficacy of Three Vaccines in Protecting Western Scrub-Jays (Aphelocoma californica) from Experimental Infection with West Nile Virus: Implications for Vaccination of Island Scrub-Jays (Aphelocoma insularis)

“…These results differed from previous studies that utilized pCBWN with multiple vaccinations and lower PRNT cut-off values. In one study (Bunning et al 2007), where American Crows received two vaccinations at 21-day intervals, 80% of the birds were PRNT 70 positive for WNV antibodies at a serum dilution of 1:10 six weeks postvaccination. However, by 9 weeks postvaccination the percent PRNT 70 antibody positive dropped to 50%.…”

“…Because of the difficulty of capturing and vaccinating free-ranging Island Scrub-Jays more than once per year (Boyce et al 2011), we chose to evaluate the efficacy of a single inoculation with one of three vaccines to protect Western Scrub-Jays from experimental infection with WNV. Although some of the evaluated vaccines have been tested in other corvids, including Fish Crows (Corvus ossifragus) (Turell et al 2003) and American Crows (Corvus brachyrhynchos) (Bunning et al 2007), this is the first evaluation of these vaccines in the genus Aphelocoma.…”

DNA Vaccination of American Robins (Turdus migratorius) Against West Nile Virus

“…One of these vaccines, first licensed for horses, is based on recombinant DNA plasmid technology and has been shown to be efficacious and safe in mice and horses (Davis et al 2001) as well as four species of wild birds, American crows (Corvus brachyrhynchos), fish crows (Corvus ossifragus), California condors (Gymnogyps californianus), and Andean condors (Vultur gryphus) (Turell et al 2003, Bunning et al 2007, Chang et al 2007, and has been used to vaccinate two others, Sandhill cranes (Grus canadensis) and Whooping cranes (Grus americana) without ill effects (Stehn 2002). The cells that uptake the plasmid DNA in the vaccine express the premembrane and envelope proteins of WNV, and the host immune system mounts a response to these expressed antigens (Davis et al 2001).…”

“…The cells that uptake the plasmid DNA in the vaccine express the premembrane and envelope proteins of WNV, and the host immune system mounts a response to these expressed antigens (Davis et al 2001). In the studies where vaccination was followed by experimental challenge with WNV, vaccinated birds had increased survival and reduced viremias compared to the nonvaccinated group (Turell et al 2003, Bunning et al 2007.…”

Evaluation of Cross-Protection of a Lineage 1 West Nile Virus Inactivated Vaccine against Natural Infections from a Virulent Lineage 2 Strain in Horses, under Field Conditions

“…Experimental vaccinations in birds have been applied outside Europe (although bird vaccines against WNV are not commercially available) to a limited extent, especially in endangered bird species (e.g., in California condors) to protect them from fatal WNV infection or in bird reservoir hosts (e.g., American crows and robins), with the aim of reducing WNV viremia in them and preventing subsequent transmission of the virus to competent vectors (22)(23)(24)(25)(26). With regard to dead-end hosts, for humans only passive immunization (intravenous immunoglobulin or hyperimmune gammaglobulin administration) has been used to a limited extent for treatment of patients with WNND (27).…”