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

Abstract

The genes that encode merozoite surface antigens (MSAs) in Babesia bovis are genetically diverse. In this study, we analyzed the genetic diversity of B. bovis MSA-1, MSA-2b, and MSA-2c genes in Vietnamese cattle and water buffaloes. Blood DNA samples from 258 cattle and 49 water buffaloes reared in the Thua Thien Hue province of Vietnam were screened with a B. bovis-specific diagnostic PCR assay. The B. bovis-positive DNA samples (23 cattle and 16 water buffaloes) were then subjected to PCR assays to amplify the MSA-1, MSA-2b, and MSA-2c genes. Sequencing analyses showed that the Vietnamese MSA-1 and MSA-2b sequences are genetically diverse, whereas MSA-2c is relatively conserved. The nucleotide identity values for these MSA gene sequences were similar in the cattle and water buffaloes. Consistent with the sequencing data, the Vietnamese MSA-1 and MSA-2b sequences were dispersed across several clades in the corresponding phylogenetic trees, whereas the MSA-2c sequences occurred in a single clade. Cattle- and water-buffalo-derived sequences also often clustered together on the phylogenetic trees. The Vietnamese MSA-1, MSA-2b, and MSA-2c sequences were then screened for recombination with automated methods. Of the seven recombination events detected, five and two were associated with the MSA-2b and MSA-2c recombinant sequences, respectively, whereas no MSA-1 recombinants were detected among the sequences analyzed. Recombination between the sequences derived from cattle and water buffaloes was very common, and the resultant recombinant sequences were found in both host animals. These data indicate that the genetic diversity of the MSA sequences does not differ between cattle and water buffaloes in Vietnam. They also suggest that recombination between the B. bovis MSA sequences in both cattle and water buffaloes might contribute to the genetic variation in these genes in Vietnam.

Type-specific PCR assays for Babesia bovis msa-1 genotypes in Asia: Revisiting the genetic diversity in Sri Lanka, Mongolia, and Vietnam

“…Out of nine samples that were positive for the type-specific PCR assays in Vietnam, six and three were from cattle and water buffaloes, respectively. In agreement with the previous studies (Sivakumar et al, 2013b;Yokoyama et al, 2015), five (C, AS1, AS4, AS5, AS7, and AS8) and four (AS1, AS4, AS6, and AS8) different genotypes were detected in the DNA samples from Sri Lanka and Vietnam, respectively. In contrast, in addition to the previously described genotype C (Altangerel et al, 2012), three novel genotypes (AS1, AS4, and AS6) were detected in the DNA samples from…”

“…Vietnam (Yokoyama et al, 2015). Among the nine genotypes analyzed, seven were detected in the DNA samples.…”

“…Detection of a band at the appropriate size (Table 1) and non-infected bovine blood (Sivakumar et al, 2012b) were also used to analyze the specificity of each type-specific PCR assay. In total, 109 B. bovis-positive blood DNA samples from Sri Lanka (44 cattle) (Sivakumar et al, 2013b), Mongolia (26 cattle) (Altangerel et al, 2012), and Vietnam (23 cattle and 16 water buffalo) (Yokoyama et al, 2015) extracted using a commercial kit (QIAamp DNA Blood Mini Kit, Qiagen, Hilden, Germany) were then screened by the type-specific PCR assays.…”

“…Among the msa genes, msa-1, msa-2b, and msa-2c have been well studied in terms of their genetic diversity. Phylogenetic analyses in previous investigations 6 showed that both the MSA-2b and MSA-2c sequences lack geographical sub-structuring and that the msa-1 sequences often cluster phylogenetically according to their continents of origin (Sivakumar et al, 2013b;Yokoyama et al, 2015). In the present study, therefore, we developed type-specific PCR assays for Asian msa-1 genotypes of B. bovis, and then evaluated their performances using B. bovis-positive DNA samples that had been previously characterized for MSA genetic diversity in Sri Lanka (Sivakumar et al, 2013b), Mongolia (Altangerel et al, 2012), and Vietnam (Yokoyama et al, 2015).…”

“…Therefore, fully elucidating the genetic diversity of MSA genes may prove crucial in developing effective immune control strategies against B. bovis infection. For this reason, the genetic diversity of MSA genes has been investigated in several B. bovis-endemic countries, including Australia (Berens et al, 2005;Leroith et al, 2005), Sri Lanka (Sivakumar et al, 2013b), Mongolia (Altangerel et al, 2012), Vietnam (Sivakumar et al, 2013a;Yokoyama et al, 2015), the Philippines (Tattiyapong et al, 2014), Thailand (Nagano et al, 2013Simking et al, 2013), Israel (Molad et al, 2014,…”