Exoantigens of an attenuated strain of Babesia bovis used as a vaccine against bovine babesiosis.
Bovine babesiosis caused by Babesia bovis remains a significant constraint to beef and milk cattle production throughout the world. Exoantigens released by the parasites in culture supernatants are a potential source of antigen to induce protective immunity. An attenuated strain of B. bovis from Brazil, catalogued as BbUFV1, was maintained in vitro by the MASP method, and exoantigen-containing supernatant fluids were collected daily to form a pool representing a 72-h culture cycle for preparation of the vaccine. Exoantigen concentration was estimated using a two-site EIA. Three groups of susceptible non-splenectomised male Bos taurus cattle, 14 months old, were used. Group A (vaccinated) received two subcutaneous immunizations with a 21-day interval of B. bovis supernatant, content 6500 EIA units of exoantigens plus 1.5 mg saponin, and Group B (adjuvant control) received two injections of adjuvant alone. Four weeks after the second immunization, Groups A, B and C (control) were challenged intravenously with 10(8) virulent parasites of a heterologous B. bovis strain. The results showed that exoantigens present in in vitro cultures can induce a high degree of protection against virulent heterologous challenge exposure. In Group A only one animal showed discrete parasitaemia; all developed a fever and slight decreases in PCV, with a rapid return to normal values. One animal of Group B died; the survivors showed fever, anaemia and parasitaemia. All animals of Group C died between 7 and 13 days after challenge. Vaccination elicited both humoral and cell-mediated immune responses. In Group A, after the challenge, the maximum antibody titer was 12,800. When vaccinated, cattle were tested at the moment of challenge for B. bovis-specific cell-mediated immunity by the monocytemigration inhibition test. A mean inhibition index of 60 +/- 0.33 was observed. Preliminary Western blot analysis of the immunogen revealed at least four proteins of molecular weight ranging between 30 and 160 kDa.
Laboratorio de Biologia e Controle de Hematozoários-BIOAGRO, Departamento de Veterinária, Universidade Federal de Viçosa, MG, Brazil.
J H
JH
Patarroyo
A A
AA
Prates
C A
CA
Tavares
C L
CL
Mafra
M I
MI
Vargas
D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis / Q000097:blood; D000917:Antibody Formation; D000953:Antigens, Protozoan / Q000276:immunology*; D016793:Babesia bovis / Q000276:immunology*; D001404:Babesiosis / Q000276:immunology* / Q000517:prevention & control; D015153:Blotting, Western; D002417:Cattle; D002418:Cattle Diseases; D005260:Female; D007111:Immunity, Cellular; D008214:Lymphocytes / Q000276:immunology*; D008297:Male; D008460:Meat; D008892:Milk; D016052:Protozoan Vaccines; D014611:Vaccination; D014613:Vaccines, Attenuated
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D016052:Protozoan Vaccines; D014613:Vaccines, Attenuated