ARS | Publication request: Assessment of bovine immunoprotecion against Rhipicephalus microplus using Bm86-CG antigen expressed in Pichia pastoris

Submitted to: Livestock Insect Worker's Conference Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: May 13, 2011
Publication Date: N/A

Technical Abstract: The cattle tick Rhipicephalus microplus is a major pest of cattle in tropical and subtropical parts of the world. In addition to direct effects associated with its obligate parasitic way of life, R. microplus also transmits the pathogens that cause bovine babesiosis and anaplasmosis. Commercially available anti-R. microplus vaccines based on the antigen Bm86 represent a method that provides a sustainable option for integrated tick control programs that don’t rely solely on the use of acaricides. However, there seems to be variation in the level of field efficacy achieved with commercial Bm86-based vaccines. Work presented here involves cloning the Bm86-CG gene into the vector pPICZaA and transformation of the yeast P. pastoris to express the recombinant form of Bm86-CG (rBm86CG), which could be used to try to enhance the efficacy of vaccines against R. microplus infesting cattle in Mato Grosso do Sul state in Brazil. The rBm86CG yield achieved using P. pastoris was 870 mg/L of medium. rBm86CG was recognized in Western-blots by antibodies in serum from mice immunized with Gavac®, TickGardPLUS, larval extract, and rBm86CG. Cattle were inoculated three times every two weeks to assess the efficacy of rBm86CG. Each inoculation (2 ml) contained 100 µg of rBm86CG and Montanide ISA as adjuvant. Antibody responses in the treated and negative control groups were measured using an ELISA. Upon tick challenge, the antibody response in cattle immunized with rBm86CG was associated with a 28% reduction in tick numbers relative to the control group. A lack of effect on tick reproductive parameters was observed. The immunization of cattle with rBm86CG expressed in P. pastoris resulted in an overall efficacy of 39% against R. microplus.