msa‐1 and msa‐2c Gene Analysis and Common Epitopes Assessment in Mexican Babesia bovis Isolates

Abstract

Babesia bovis msa-1 and msa-2c genes belong to the variable merozoite surface antigen gene family. These genes code for antigenic proteins present on the merozoite surface (MSA) and are involved in the parasite invasion to the bovine erythrocyte. Previous studies carried out on MSA-1 have evidenced antigen allelic variation in B. bovis isolates from similar endemic regions, as well as in isolates from different geographic regions of the world (Argentina, Australia, Israel). Studies conducted on MSA-2c, however, have shown that this antigen is widely conserved on isolates from distinct geographic regions. In this study, it was hypothesized that MSA-1 and MSA-2c antigens would contain common epitopes despite the presence of nucleotide sequence differences found in 13 B. bovis isolates and strains collected in geographically distant regions of Mexico. Bioinformatics analysis of the primary structure from DNA fragments derived from PCR amplification, cloning, and sequencing of msa-1 and msa-2c genes from the 13 B. bovis populations revealed that the msa-1 gene product present in the various isolates tested is less conserved among isolates obtained within a similar geographic region in Mexico (51-99.7% sequence identity). Results obtained by immunoblot analysis of B. bovis protein extracts reacted with a monoclonal antibody to MSA-1 42-kDa antigen, conclusively showed cross-reactive common epitopes only in Mexican isolates having high sequence identity (>/=99%, eight isolates). Sequence analysis and multiple alignment of deduced MSA-2c demonstrated a high degree of sequence identity (90-100%) among the Mexican B. bovis isolates and strains. Immunoblot results using a polyclonal antibody to MSA-2c reacted against the protein extracts recognized conserved epitopes in at least nine of the B. bovis isolates. The results obtained in this study agree with those previously reported by other researchers and confirm that, based in sequence identity conservation in Mexican B. bovis isolates and strains so far collected and analyzed, MSA-2c represents an ideal antigen worth evaluating as a vaccine candidate.

Genetic variations in merozoite surface antigen genes of Babesia bovis detected in Vietnamese cattle and water buffaloes

“…The involvement of genetic diversity in the immune evasion of B. bovis is well documented in the literature (Berens et al, 2005;Leroith et al, 2005). Consequently, the genetic diversity among the MSA genes has been studied in several endemic countries (Altangeral et al, 2012;Berens et al, 2005;Borgonio et al, 2008;Genis et al, 2008Genis et al, , 2009Leroith et al, 2005;Molad et al, 2014;Nagano et al, 2013;Sivakumar et al, 2013b;Tattiyapong et al, 2014). Almost all these studies invariably focused on the genetic diversity of the MSA genes of B. bovis derived from cattle, whereas B. bovis in buffaloes has rarely been investigated, although this host species is considered to play a significant role in its epidemiology (da Silva et al, 2013;Elsify et al, 2015;He et al, 2012;Sivakumar et al, 2013a).…”

Sequence Conservation of the 12D3 Gene in Mexican Isolates of Babesia bovis

“…Previous studies conducted on the Tamaulipas‐2 and Yucatan B. bovis isolate have shown nucleotide sequence diversity when merozoite surface antigen gene sequences ( msa‐1, msa‐2b, and msa‐2c ) were analysed (Borgonio et al, 2008; Genis et al., 2008, 2009). It is not known, however, if this sequence polymorphism is associated to a particular biological feature for these particular isolates.…”

“…The recombinant version of the 12D3 protein derived from a Mexican isolate has been recently cloned and expressed as a fusion protein with thioredoxin in our laboratory. By combining the recombinant 12D3 protein along with the recombinant version of the merozoite surface antigen 1 (MSA‐1) and MSA‐2c, two antigens widely conserved in B. bovis Mexican isolates (Borgonio et al., 2008), cattle immunized with this antigen cocktail showed partial protection when challenged with a field isolate (Alvarez et al., 2009).…”

Genome-Based Vaccinology Applied to Bovine Babesiosis

“…It could be due to the fact that msa-1 gene has an important allelic variation in strains from the nearby geographical regions. This variation suggests that the antibodies generated could not have a cross-reaction between different strains [34,35].…”