Bovine
anaplasmosis is a hemoparasitic disease that causes considerable economic loss to the dairy and beef industries. Cattle immunized with the Anaplasma marginale
MSP1 outer
membrane protein complex presents a protective humoral immune response; however, its efficacy is variable.
Immunodominant epitopes seem to be a key-limiting factor for the adaptive immunity. We have successfully demonstrated that critical motifs of the MSP1a functional
epitope are essential for antibody recognition of infected animal sera, but its protective immunity is yet to be tested. We have evaluated two
synthetic vaccine formulations against A. marginale, using
epitope-based approach in mice. Mice
infection with bovine
anaplasmosis was demonstrated by qPCR analysis of erythrocytes after 15-day exposure. A proof-of-concept was obtained in this murine model, in which
peptides conjugated to
bovine serum albumin were used for immunization in three 15-day intervals by
intraperitoneal injections before challenging with live bacteria. Blood samples were analyzed for the presence of specific
IgG2a and
IgG1 antibodies, as well as for the rickettsemia analysis. A panel containing the
cytokines' transcriptional profile for innate and adaptive immune responses was carried out through qPCR. Immunized BALB/c mice challenged with A. marginale presented stable
body weight, reduced number of infected erythrocytes, and no mortality; and among control groups mortality rates ranged from 15% to 29%. Additionally,
vaccines have significantly induced higher
IgG2a than
IgG1 response, followed by increased expression of pro-inflammatory
cytokines. This is a successful demonstration of
epitope-based
vaccines, and protection against
anaplasmosis may be associated with elicitation of effector functions of humoral and cellular immune responses in murine model.