Comparing Class II MHC DRB3 Diversity in Colombian Simmental and Simbrah Cattle Across Worldwide Bovine Populations.

Diego Ordoñez,Catalina Avendaño,Manuel Alfonso Patarroyo,Michel David Bohórquez,Manuel Alfonso Patarroyo,Michel David Bohórquez,Manuel Alfonso Patarroyo

doi:10.3389/fgene.2022.772885

Abstract

The major histocompatibility complex (MHC) exerts great influence on responses to infectious diseases and vaccination due to its fundamental role in the adaptive immune system. Knowledge about MHC polymorphism distribution among breeds can provide insights into cattle evolution and diversification as well as population-based immune response variability, thus guiding further studies. Colombian Simmental and Simbrah cattle’s BoLA-DRB3 genetic diversity was compared to that of taurine and zebuine breeds worldwide to estimate functional diversity. High allele richness was observed for Simmental and Simbrah cattle; nevertheless, high homozygosity was associated with individual low sequence variability in both the β1 domain and the peptide binding region (PBR), thereby implying reduced MHC-presented peptide repertoire size. There were strong signals of positive selection acting on BoLA-DRB3 in all populations, some of which were poorly structured and displayed common alleles accounting for their high genetic similarity. PBR sequence correlation analysis suggested that, except for a few populations exhibiting some divergence at PBR, global diversity regarding potential MHC-presented peptide repertoire could be similar for the cattle populations analyzed here, which points to the retention of functional diversity in spite of the selective pressures imposed by breeding.

Highlights

The major histocompatibility complex (MHC) plays an important effector role in the adaptive immune response (Rock et al, 2016)
MHC class I proteins are expressed by all nucleated cells and are related to presenting antigens to CD8+ T-lymphocytes processed in the intracellular compartment, thereby eliciting cytotoxic responses (Neefjes et al, 2011; Rock et al, 2016)
BoLADR consists of the DRA monomorphic locus and three DRB loci, of which bovine leukocyte antigen (BoLA)-DRB3—characterized by a high degree of polymorphism, with 330 different alleles reported to date—is the only one which has been described as functional (Maccari et al, 2017)

Summary

Introduction

The major histocompatibility complex (MHC) plays an important effector role in the adaptive immune response (Rock et al, 2016). BoLADR consists of the DRA monomorphic locus and three DRB loci, of which BoLA-DRB3—characterized by a high degree of polymorphism, with 330 different alleles reported to date—is the only one which has been described as functional (Maccari et al, 2017). Such polymorphisms are concentrated in the second exon which encodes the peptide binding region (PBR) β1 domain and has been used for determining BoLA-DRB3 alleles (Sigurdardóttir et al, 1991). BoLA-DRB3 diversity could be used for estimating potential peptide-binding repertoire size, based on the assumption that highly divergent alleles are associated with broader peptide spectra (Klein et al, 2007)

Methods

Results

Conclusion