title: Evaluation of the Efficacy, Potential for Vector Transmission, and Duration of Immunity of MP-12, an Attenuated Rift Valley Fever Virus Vaccine Candidate, in Sheep.
abstract: Rift Valley fever virus (RVFV) causes serious disease in ruminants and humans in Africa. In North America, there are susceptible ruminant hosts and competent mosquito vectors, yet there are no fully licensed animal vaccines for this arthropod-borne virus, should it be introduced. Studies in sheep and cattle have found the attenuated strain of RVFV, MP-12, to be both safe and efficacious based on early testing, and a 2-year conditional license for use in U.S. livestock has been issued. The purpose of this study was to further determine the vaccine's potential to infect mosquitoes, the duration of humoral immunity to 24 months postvaccination, and the ability to prevent disease and viremia from a virulent challenge. Vaccination experiments conducted in sheep found no evidence of a potential for vector transmission to 4 North American mosquito species. Neutralizing antibodies were elicited, with titers of >1:40 still present at 24 months postvaccination. Vaccinates were protected from clinical signs and detectable viremia after challenge with virulent virus, while control sheep had fever and high-titered viremia extending for 5 days. Antibodies to three viral proteins (nucleocapsid N, the N-terminal half of glycoprotein GN, and the nonstructural protein from the short segment NSs) were also detected to 24 months using competitive enzyme-linked immunosorbent assays. This study demonstrates that the MP-12 vaccine given as a single dose in sheep generates protective immunity to a virulent challenge with antibody duration of at least 2 years, with no evidence of a risk for vector transmission.
authors.affiliation: University of Wyoming, Laramie, Wyoming, USA millermm@uwyo.edu.
authors.forename: Myrna M
authors.initials: MM
authors.lastname: Miller
authors.affiliation: Arthropod-Borne Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Manhattan, Kansas, USA (previously ABADRL, Laramie, Wyoming, USA).
authors.forename: Kristine E
authors.initials: KE
authors.lastname: Bennett
authors.affiliation: Arthropod-Borne Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Manhattan, Kansas, USA (previously ABADRL, Laramie, Wyoming, USA).
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Drolet
authors.affiliation: Zoonotic Diseases and Special Pathogens, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Robbin
authors.initials: R
authors.lastname: Lindsay
authors.affiliation: Arthropod-Borne Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Manhattan, Kansas, USA (previously ABADRL, Laramie, Wyoming, USA).
authors.forename: James O
authors.initials: JO
authors.lastname: Mecham
authors.affiliation: Arthropod-Borne Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Manhattan, Kansas, USA (previously ABADRL, Laramie, Wyoming, USA).
authors.forename: Will K
authors.initials: WK
authors.lastname: Reeves
authors.affiliation: National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Winnipeg, Manitoba, Canada.
authors.forename: Hana M
authors.initials: HM
authors.lastname: Weingartl
authors.affiliation: Arthropod-Borne Animal Diseases Research Unit, Agricultural Research Service, United States Department of Agriculture, Manhattan, Kansas, USA (previously ABADRL, Laramie, Wyoming, USA).
authors.forename: William C
authors.initials: WC
authors.lastname: Wilson
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000276:immunology; D009033:Culicidae / Q000821:virology*; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D004797:Enzyme-Linked Immunosorbent Assay; D009500:Neutralization Tests; D012295:Rift Valley Fever / Q000276:immunology / Q000517:prevention & control*; D012296:Rift Valley fever virus / Q000276:immunology*; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology / Q000517:prevention & control*; D013997:Time Factors; D016896:Treatment Outcome; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology*; D014766:Viremia / Q000517:prevention & control
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000956:Antigens, Viral; D014613:Vaccines, Attenuated; D014765:Viral Vaccines