Progresses in immunization against Anaplasma marginale

Abstract

The current immunization against anaplasmosis in cattle is derived from the blood of infected animals, as live or dead organisms. Nevertheless, efforts have been made to develop a new generation of vaccines. The outer membrane of Anaplasma marginale induces a protective immune response against challenge with homologous isolates and a partially protective response against heterologous challenge. In this membrane, six major surface proteins (MSPs) have been identified, which have been targeted for the development of immunogens against anaplasmosis. From those proteins, MSP1a and MSP2 have shown the greatest potential as immunogens, protecting cattle against challenge with virulent homologous and heterologous isolates of A marginale, despite the size polymorphism of the former protein and the variability of the gene that encodes the latter protein. Another alternative of immunogen is the in vitro culture of A marginale. Inactivated organisms originating from Dermacentor variabilis IDE8 cell culture were tested as immunogen. Cattle immunized with cell culture-derived A. marginale had a significantly lower reduction in the packed cell volume after challenge exposure and did not display clinical anaplasmosis. Besides the protection afforded by this type of immunogen, cell culture derived organisms are free from bovine cells and pathogens, what is a major advantage as compared with traditional immunization procedures.