title: 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.
abstract: Although experimental data regarding cross-protection of horse West Nile virus (WNV) vaccines against lineage 2 infections exist, the cross-protective efficacy of these vaccines under field conditions has not been demonstrated. This study was conducted to evaluate the capability of an inactivated lineage 1 vaccine (Equip WNV) to protect against natural infections from the Nea Santa-Greece-2010 lineage 2 strain. In total, 185 WNV-seronegative horses in Thessaloniki, Greece, were selected during 2 consecutive years (2011 and 2012); 140 were immunized, and 45 were used as controls. Horses were examined for signs compatible with WNV infection. Neutralizing antibody titers against the Greek strain and the PaAn001/France lineage 1 strain were determined in immunized horses. WNV circulation was detected during both years in the study area. It was estimated that 37% and 27% of the horses were infected during 2011 and 2012, respectively. Three control animals developed clinical signs, and the WNV diagnosis was confirmed. Signs related to WNV infection were not observed in the vaccinated animals. The nonvaccinated animals had a 7.58% ± 1.82% higher chance of exhibiting signs than immunized animals (P < 0.05). Neutralizing antibodies raised against both strains in all immunized horses were detectable 1 month after the initial vaccination course. The cross-protective capacity of the lowest titer (1:40) was evident in 19 animals which were subsequently infected and did not exhibit signs. Neutralizing antibodies were detectable until the annual booster, when strong anamnestic responses were observed (geometrical mean titer ratio [GMTR] for lineage 1 of 30.2; GMTR for lineage 2 of 27.5). The results indicate that Equip WNV is capable of inducing cross-protection against natural infections from a virulent lineage 2 WNV strain in horses.
authors.affiliation: Diagnostic Laboratory, Department of Clinical Sciences, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Serafeim C
authors.initials: SC
authors.lastname: Chaintoutis
authors.affiliation: Equine Unit, Companion Animal Clinic, Department of Clinical Sciences, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Diakakis
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Papanastassopoulou
authors.affiliation: Department of Animal Production, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece SRUC, Easter Bush, Midlothian, Scotland, United Kingdom The Roslin Institute, Royal (Dick) School of Veterinary Science, Easter Bush, Midlothian, Scotland, United Kingdom.
authors.forename: Georgios
authors.initials: G
authors.lastname: Banos
authors.affiliation: Diagnostic Laboratory, Department of Clinical Sciences, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece dovas@vet.auth.gr.
authors.forename: Chrysostomos I
authors.initials: CI
authors.lastname: Dovas
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood / Q000276:immunology; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D056738:Cross Protection; D006115:Greece; D006734:Horse Diseases / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D006736:Horses; D007115:Immunization Schedule; D016415:Sequence Alignment; D013997:Time Factors; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000276:immunology; 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 / Q000145:classification / Q000276:immunology* / Q000472:pathogenicity*
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D015164:Vaccines, Inactivated; D014759:Viral Envelope Proteins; D053060:West Nile Virus Vaccines