Evaluation of host immune responses following immunization with MSP4 antigen adsorbed onto poly(lactic-co-glycolic acid) microparticles in a BALB/c murine model

Tick-borne diseases lead to millions of dollars in losses annually in livestock and associated industries. The tick-borne bacterium Anaplasma phagocytophilum causes diseases in most livestock and has demonstrated zoonosis. Currently there are no effective prophylaxes against this bacterium. MSP4 (major surface protein 4) has been identified as a promising vaccine candidate. Currently, data on the expression of this antigen in tick and host cells is lacking to establish it as an antigen accessible to the host immune response. When designing a vaccine against Anaplasma, it must be considered that the life cycle includes both free circulating and intracellular stages, and as such both Th1 and Th2 responses will most likely be needed for protection. This study provides evidence of the expression of MSP4 on tick and host cells, as well as T and B cell responses following immunisation with soluble and MSP4 coated PLGA microparticles in a murine model (BALB/c mice). This paves the way forward to rational improvement of vaccines against Anaplasma.