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Abstract: The emergence of lineage 2 strains of WNV in Europe as a cause of clinical disease and mortality in horses raised the question whether the existing WNV vaccines, all based on lineage 1 strains, protect against circulating lineage 2 strains of WNV. In the present paper we have determined the level of cross protection provided by the recombinant ALVAC®-WNV vaccine in a severe challenge model that produces clinical signs of WNV type 2 disease. Ten horses were vaccinated twice at 4 weeks interval with one dose of the ALVAC-WNV vaccine formulated at the minimum protective dose. A further 10 horses served as controls. Two weeks after the second vaccination, all horses were challenged intrathecally with a recent neurovirulent lineage 2 strain of WNV. The challenge produced viraemia in 10 out of 10 and encephalitis in 9 out of 10 control horses. Three horses had to be euthanized for humane reasons. In contrast, none of the vaccinated horses developed WNV disease and only 1 vaccinated horse became viraemic at a single time point at low titre. The prevalence of WNV disease and viraemia were significantly lower in the vaccinated horses than in the control horses (P <0.0001 for both). Based on these results, the ALVAC-WNV vaccine will provide veterinarians with an effective tool to control infections caused by lineage 1 and 2 strains of WNV. [Copyright &y& Elsevier]

The objective of this study was to determine the effect of vaccination with commercially-available multivalent vaccines containing either modified-live (MLV) bovine herpesvirus-1 (BHV-1) (Bovishield) or MLV plus killed (MLV + K) BHV-1 (Reliant Plus) on protection against challenge at 5 days after a single vaccination. An additional objective was to determine whether cell-mediated immunity as measured by virus-specific interferon gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMC) was associated with any early protection induced by vaccination. Clinical signs, serum neutralizing (SN) titers, and nasal virus isolation (VI) titers were also measured. The 12-16-week-old dairy cross-calves seronegative for antibodies to BHV-1 were vaccinated with a multivalent vaccine containing MLV BHV-1 (n = 19), a multivalent vaccine containing MLV + K BHV-1 (n = 19), or a control multivalent vaccine not containing BHV-1 (n = 10) on day 0 and challenged intranasally on day 5. PBMC were isolated on days 0, 3, 5, 8, 10, 14 and 19. PBMC were incubated in vitro with spent media, live BHV-1, or heat-inactivated BHV-1 for 72 h. Supernatants were assayed for bovine IFN-gamma by ELISA. Bovine herpesvirus-1-specific IFN-gamma production was expressed as percent of the kit positive control, with value for spent media subtracted. Clinical signs were monitored daily. Serum VN titers were measured on days 0-5 and 19. Nasal VI titer was measured every other day from days 5 to 19. Interferon gamma production was higher on day 5, and was significantly increased post-challenge, in both vaccine groups compared to controls. There was no difference between vaccine groups on any day. There was no significant difference in SN titer among groups on any day. Virus isolation titer was significantly higher in controls on days 6 and 8 compared to both vaccine groups. Temperatures were significantly higher and nasal discharge was present more often post-challenge in controls compared to vaccine groups. Vaccination 5 days prior to challenge with commercially-available vaccine containing MLV or MLV + K BHV-1 was associated with increased BHV-1-specific IFN-gamma production, decreased viral shedding, lower temperatures and less nasal discharge post-challenge. Cell mediated immune responses as measured by IFN-gamma production are stimulated rapidly following BHV-1 vaccination of calves., (Copyright 2002 Elsevier Science Ltd.)