title: Protective immunity induced by immunization with a live, cultured Anaplasma marginale strain.
abstract: Despite significant economic losses resulting from infection with Anaplasma marginale, a tick-transmitted rickettsial pathogen of cattle, available vaccines provide, at best, only partial protection against clinical disease. The green-fluorescent protein expressing mutant of the A. marginale St. Maries strain is a live, marked vaccine candidate (AmStM-GFP). To test whether AmStM-GFP is safe and provides clinical protection, a group of calves was vaccinated, and clinical parameters, including percent parasitized erythrocytes (PPE), packed cell volume (PCV) and days required to reach peak bacteremia, were measured following inoculation and following tick challenge with wild type St. Maries strain (AmStM). These clinical parameters were compared to those obtained during infection with the A. marginale subsp. centrale vaccine strain (A. centrale) or wild type AmStM. AmStM-GFP resulted in similar clinical parameters to A. centrale, but had a lower maximum PPE, smaller drop in PCV and took longer to reach peak bacteremia than wild type AmStM. AmStM-GFP provided clinical protection, yielding a stable PCV and low bacteremia following challenge, whereas A. centrale only afforded partial clinical protection.
authors.affiliation: Program in Genomics, Department of Veterinary Microbiology and Pathology, Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99164-7040, USA.
authors.forename: G Kenitra
authors.initials: GK
authors.lastname: Hammac
authors.forename: Pei-Shin
authors.initials: PS
authors.lastname: Ku
authors.forename: Maria F
authors.initials: MF
authors.lastname: Galletti
authors.forename: Susan M
authors.initials: SM
authors.lastname: Noh
authors.forename: Glen A
authors.initials: GA
authors.lastname: Scoles
authors.forename: Guy H
authors.initials: GH
authors.lastname: Palmer
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Brayton
mesh_terms: D042322:Anaplasma marginale / Q000235:genetics / Q000276:immunology*; D000712:Anaplasmosis / Q000276:immunology* / Q000382:microbiology / Q000517:prevention & control; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D016470:Bacteremia / Q000382:microbiology; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000517:prevention & control; D056738:Cross Protection / Q000276:immunology; D004912:Erythrocytes / Q000382:microbiology; D049452:Green Fluorescent Proteins / Q000235:genetics; D008297:Male; D012290:Rickettsial Vaccines / Q000009:adverse effects / Q000276:immunology*; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D012290:Rickettsial Vaccines; D049452:Green Fluorescent Proteins
keywords: AmStM; AmStM-GFP; Anaplasma marginale St. Maries strain; Bovine; GFP-transformed AmStM; OM; Tick-borne disease; outer membrane