Abstract:
BACKGROUND: The cattle ticks, Boophilus spp., affect cattle production in tropical and subtropical
regions of the world. Tick vaccines constitute a cost-effective and environmentally friendly
alternative to tick control. The recombinant B. microplus Bm86 protective antigen has been shown
to protect cattle against tick infestations. Recently, the gene coding for B. annulatus Bm86 ortholog,
Ba86, was cloned and the recombinant protein was secreted and purified from the yeast Pichia
pastoris.
RESULTS: Recombinant Ba86 (Israel strain) was used to immunize cattle to test its efficacy for the
control of B. annulatus (Mercedes, Texas, USA strain) and B. microplus (Susceptible, Mexico strain)
infestations. Bm86 (Gavac and Mozambique strain) and adjuvant/saline were used as positive and
negative controls, respectively. Vaccination with Ba86 reduced tick infestations (71% and 40%),
weight (8% and 15%), oviposition (22% and 5%) and egg fertility (25% and 50%) for B. annulatus and
B. microplus, respectively. The efficacy of both Ba86 and Bm86 was higher for B. annulatus than for
B. microplus. The efficacy of Ba86 was higher for B. annulatus (83.0%) than for B. microplus (71.5%).
The efficacy of Bm86 (Gavac; 85.2%) but not Bm86 (Mozambique strain; 70.4%) was higher than
that of Ba86 (71.5%) on B. microplus. However, the efficacy of Bm86 (both Gavac and Mozambique
strain; 99.6%) was higher than that of Ba86 (83.0%) on B. annulatus.
CONCLUSION: These experiments showed the efficacy of recombinant Ba86 for the control of B.
annulatus and B. microplus infestations in cattle and suggested that physiological differences between
B. microplus and B. annulatus and those encoded in the sequence of Bm86 orthologs may be
responsible for the differences in susceptibility of these tick species to Bm86 vaccines.
