Construction of a multi-epitope in silico vaccine against Anaplasma Marginale using immunoinformatics approach

Anaplasma Marginale, a rickettsial gram-negative bacterium, is responsible for causing bovine anaplasmosis which has widely spread among the different parts of the world causing death among cattle. It is mainly spread through the transmission of infected ticks. The manifestation of infected ticks could be controlled to a limited extent. However, subsequently, it is very much necessary for the cattle to develop strong immunity against A. marginale. It could be possible if a subunit vaccine is created against the rickettsial bacteria and introduced into the blood of the cattle for trials. In this paper, we have conducted a study to develop a multi-epitope subunit vaccine against A.marginale by using reverse vaccinology process. Five highly immunogenic outer membrane proteins of A. marginale were selected such as MSP1a, MSP2, Vir B10, OMP1 and OMP11. These proteins bind to the MHC class I molecules of the epithelial cells of mammals and MHC class II molecules of the antigen-presenting cells such as B-cells. The MHC class I molecules present antigens to the cytotoxic t-lymphocytes whereas the MHC class II molecules present antigens to the helper t-lymphocytes thus, initiating a strong immune response among the bovine species. We constructed three vaccine sequences from which two vaccine constructs V2 and V3, were found to be stable with high solubility and negative allergenicity. We also performed molecular docking of the two refined vaccine constructs with Rp-105 (30% resemblance in sequence to TLR4) and TLR-9. The vaccines interacted with the receptors with high binding energy. The best-designed vaccine construct was then reverse transcribed and adapted for the host E.coli K12 strain. The reverse transcribed sequence was later inserted into the pET28a (+) vector for the cloning and expression of the vaccine. The study could be a better initiative for in vitro and in vivo practice in developing an effective vaccine against A. marginale.