Polymorphism of bovine major histocompatibility complex (MHC) class I genes revealed by polymerase chain reaction (PCR) and restriction enzyme analysis

Genetic Diversity and Sequence Conservation of Peptide-Binding Regions of MHC Class I Genes in Pig, Cattle, Chimpanzee, and Human

Comparative analyses of MHC gene diversity and evolution across different species could offer valuable insights into the evolution of MHC genes. Intra- and inter-species sequence diversity and conservation of 12 classical major histocompatibility complex (MHC) class I genes from cattle, chimpanzees, pigs, and humans was analyzed using 20 representative allelic groups for each gene. The combined analysis of paralogous loci for each species revealed that intra-locus amino-acid sequence variations in the peptide-binding region (PBR) of MHC I genes did not differ significantly between species, ranging from 8.44% for SLA to 10.75% for BoLA class I genes. In contrast, intraspecies differences in the non-PBRs of these paralogous genes were more pronounced, varying from 4.59% for SLA to 16.89% for HLA. Interestingly, the Shannon diversity index and rate of nonsynonymous substitutions for PBR were significantly higher in SLA and BoLA than those in Patr and HLA. Analysis of peptide-binding pockets across all analyzed MHC class I genes of the four species indicated that pockets A and E showed the lowest and highest diversity, respectively. The estimated divergence times suggest that primate and artiodactyl MHC class I genes diverged 60.41 Mya, and BoLA and SLA genes diverged 35.34 Mya. These results offer new insights into the conservation and diversity of MHC class I genes in various mammalian species.

Association of bovine major histocompatibility complex class I (BoLA-A) alleles with immune response to Brucella abortus strain 19 in calves

In the present study, we analyzed the immune response of calves to Brucella abortus strain 19 vaccine (S19) and its association with MHC class I (BoLA-A) alleles (exons 2-3 and 4-5). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for typing of BoLA-A exon 2-3 with DdeI and TaqI restriction enzymes; and exon 4-5 with HinfI in 45 crossbred calves. The PCR-RFLP analysis revealed five BoLA-A alleles each for exon 2-3 (A10/A19, A19, A18/19, A18 and A31) and exon 4-5 (A, B, C, D and E). Immune response against B. abortus S19 was assessed at the 4^th week post vaccination; antibody response by standard tube agglutination test (STAT) and cell-mediated immunity by lymphocyte proliferation and lymphocyte-mediated cytotoxicity assays. Further, the macrophage function in terms of nitrite production was also analyzed. The association analysis of various BoLA-A alleles with the elicitation of immune response revealed that calves with certain defined genotypes induced significantly higher cell-mediated immune response in terms of lymphocyte proliferation with higher stimulation indices (S.I.) of 1.59 (BoLA-A19), 1.49 (A18/19) and 1.52 (HinfI-D); lymphocyte mediated cytotoxicity (55.52 % in A19) and nitrite production (43.40 μM in A31). It is assumed that allelic variants of BoLA-A (exons 2-3 and 4-5) were associated with the differential immune response of calves to B. abortus S19 vaccination. Therefore, further studies on association analysis of MHC class-I genes in large number of cattle may generate more information and might be useful for adapting the alternative approach of exploring genetic resistance in the cattle herd against bovine brucellosis.

Novel classical MHC class I alleles identified in horses by sequencing clones of reverse transcription-PCR products

Improved typing of horse classical MHC class I is required to more accurately define these molecules and to extend the number identified further than current serological assays. Defining classical MHC class I alleleic polymorphism is important in evaluating cytotoxic T lymphocyte (CTL) responses in horses. In this study, horse classical MHC class I genes were analyzed based on reverse transcription (RT)-PCR amplification of sequences encoding the polymorphic peptide binding region and the more conserved alpha 3, transmembrane and cytoplasmic regions followed by cloning and sequencing. Primer sets included a horse classical MHC class I-specific reverse primer and a forward primer conserved in all known horse MHC class I genes. Sequencing at least 25 clones containing MHC class I sequences from each of 13 horses identified 25 novel sequences and three others which had been described. Of these, nine alleles were identified from different horses or different RT-PCR and 19 putative alleles were identified in multiple clones from the same RT-PCR. The primer pairs did not amplify putative non-classical MHC class I genes as only classical MHC class I and related pseudogenes were found in 462 clones. This method also identified classical MHC class I alleles shared between horses by descent, and defined differences in alleles between horses varying in equine leukocyte antigen (ELA)-A haplotype as determined by serology. However, horses sharing ELA-A haplotypes defined by serotyping did not always share cDNA sequences, suggesting subhaplotypic variations within serologically defined ELA-A haplotypes. The 13 horses in this study had two to five classical MHC class I sequences, indicating that multiple loci code for these genes. Sequencing clones from RT-PCR with classical MHC class I-specific primers should be useful for selection of haplotype matched and mismatched horses for CTL studies, and provides sequence information needed to develop easier and more discriminating typing procedures.