Bm86 antigen induces a protective immune response against Boophilus microplus following DNA and protein vaccination in sheep

Vaccination of sheep with a plasmid bearing the full length gene for the ti ck antigen Bm86 either alone or co-administered with plasmid carrying the o vine genes for the cytokines, granulocyte and macrophage colony stimulating factor (GM-CSF) or interleukin (IL)-1 beta induced a relatively low level of protection against subsequent tick infestation. This tick damage reached statistical significance only for the groups which were vaccinated with pl asmid encoding for Bm86, coadministered with plasmid encoding for ovine GM- CSF Antibody titres measured against Bm86 were also low in all groups injec ted with the Bm86 DNA vaccine. Antibody production and anti-tick effect wer e significantly less than that achieved by two vaccinations with recombinan t Bm86 protein. In all cases only a low level of antigen-specific stimulati on of peripheral blood lymphocytes was recorded, as measured either by the incorporation of tritiated thymidine or the release of IFN-gamma, Injection of DNA encoding for Bm86, either alone or with co-administered cytokine ge nes, did however prime for a strong subsequent antibody response following a single injection of recombinant Bm86 protein in adjuvant, Antibody produc tion nevertheless appeared to be slightly less effective than following two vaccinations with recombinant protein. The persistence of antibody followi ng vaccination was the same regardless of the method of primary sensitizati on. In all cases the half-life of the antibody response was approximately 4 0-50 days indicating that, in contrast to results reported in mice, DNA vac cination in sheep did not result in sustained antibody production. (C) 1999 Elsevier Science B.V. All rights reserved.