The major histocompatibility complex in bovines: a review

Genetic advancements and future directions in ruminant livestock breeding: from reference genomes to multiomics innovations

Ruminant livestock provide a rich source of products, such as meat, milk, and wool, and play a critical role in global food security and nutrition. Over the past few decades, genomic studies of ruminant livestock have provided valuable insights into their domestication and the genetic basis of economically important traits, facilitating the breeding of elite varieties. In this review, we summarize the main advancements for domestic ruminants in reference genome assemblies, population genomics, and the identification of functional genes or variants for phenotypic traits. These traits include meat and carcass quality, reproduction, milk production, feed efficiency, wool and cashmere yield, horn development, tail type, coat color, environmental adaptation, and disease resistance. Functional genomic research is entering a new era with the advancements of graphical pangenomics and telomere-to-telomere (T2T) gap-free genome assembly. These advancements promise to improve our understanding of domestication and the molecular mechanisms underlying economically important traits in ruminant livestock. Finally, we provide new perspectives and future directions for genomic research on ruminant genomes. We suggest how ever-increasing multiomics datasets will facilitate future studies and molecular breeding in livestock, including the potential to uncover novel genetic mechanisms underlying phenotypic traits, to enable more accurate genomic prediction models, and to accelerate genetic improvement programs.

Evaluation of tick salivary and midgut extracellular vesicles as anti-tick vaccines in White-tailed deer (Odocoileus virginianus)

Current tick control measures are focused on the use of synthetic acaricides and personal protective measures. However, the emergence of acaricide resistance and the maintenance of tick populations in wildlife has precluded the efficient management of ticks. Thus, host-targeted, non-chemical control measures are needed to reliably reduce ticks parasitizing sylvatic reservoirs. This project aimed to evaluate extracellular vesicles (EVs) from Amblyomma americanum as vaccine candidates for white-tailed deer (Odocoileus virginianus; WTD). Salivary gland (SG) and midgut (MG) EVs were isolated by ultracentrifugation. Three deer were vaccinated with SG and MG EVs and received two boosters at days 28 and 50. Two control deer were injected with adjuvant and PBS only. On day 58, WTD were infested with 100 A. americanum nymphs, 50 females, and 50 males that were allowed to feed to repletion. On-host and off-host mortality, tick engorgement weight, nymph molting, time to oviposition, and egg hatchability were evaluated. Serum samples were recovered every seven days until the last day of tick drop off, and then at one year (Y1) and 1-year and 1-month (Y1M1). Vaccination resulted in seroconversion and significant increases in total IgG levels that remained significantly higher than controls and pre-vaccination levels at Y1 and Y1M1. No negative effects were observed in nymphs, but on-host mortality of female A. americanum was significantly higher in vaccinated animals. No effects were observed on reproductive parameters. These results indicate that proteins within female tick SG and MG vesicles are not good candidates for vaccine design against nymphs; however, the on-host adult mortality suggests that tick EVs harbor protective antigens against A. americanum females.

Vaccine candidates based on MVA viral vectors expressing VP2 or VP7 confer full protection against Epizootic hemorrhagic disease virus in IFNAR(-/-) mice

Epizootic hemorrhagic disease (EHD), caused by Epizootic hemorrhagic disease virus (EHDV), is an emerging and severe livestock disease. Recent incursion and distribution of EHDV in Europe have outlined the need for vaccine research against this viral disease. In this work, we report modified vaccinia virus Ankara (MVA)-vectored vaccines designed to express protein VP2 of EHDV-8 or protein VP7 of EHDV-2. Prime boost immunization of adult IFNAR(-/-) mice with the MVA-VP2 vaccine candidate induced high titers of EHDV-8-specific neutralizing antibodies (NAbs) and conferred full protection against homologous lethal challenge with EHDV-8. However, no heterologous protection was observed after lethal challenge with EHDV-6. In contrast, the MVA-VP7 vaccine candidate elicited strong cytotoxic CD8+ T-cell responses against VP7 and conferred complete protection against lethal challenge with either EHDV-8 or EHDV-6 in IFNAR(-/-) mice in the absence of NAbs, being the first multiserotype vaccine candidate against EHDV. Moreover, we expressed recombinant proteins VP2 and VP7 of EHDV in the baculovirus expression system, which were used to analyze the potential DIVA (differentiating infected from vaccinated animals) character of these vaccine candidates.IMPORTANCEEmergence and re-emergence of arthropod-borne viruses are major concerns for both human and animal health. The most recent example is the fast expansion of EHDV-8 through Europe. Besides, EHDV-8 relates with a high prevalence of pathologic cases in cattle populations. No vaccine is currently available in Europe, and vaccine research against this arboviral disease is negligible. In this work, we present novel DIVA vaccine candidates against EHDV, and most importantly, we identified the protein VP7 of EHDV as an antigen capable of inducing multiserotype protection, one of the major challenges in vaccine research against orbiviruses.

Graduate Student Literature Review: The DRB3 gene of the bovine major histocompatibility complex-Discovery, diversity, and distribution of alleles in commercial breeds of cattle and applications for development of vaccines

The bovine major histocompatibility complex (MHC), also known as the bovine leukocyte antigen (BoLA) complex, is the genomic region that encodes the most important molecules for antigen presentation to initiate immune responses. The first evidence of MHC in bovines pointed to a locus containing 2 antigens, one detected by cytotoxic antiserum (MHC class I) and another studied by mixed lymphocyte culture tests (MHC class II). The most studied gene in the BoLA region is the highly polymorphic BoLA-DRB3, which encodes a β chain with a peptide groove domain involved in antigen presentation for T cells that will develop and co-stimulate cellular and humoral effector responses. The BoLA-DRB3 alleles have been associated with outcomes in infectious diseases such as mastitis, trypanosomiasis, and tick loads, and with production traits. To catalog these alleles, 2 nomenclature methods were proposed, and the current use of both systems makes it difficult to list, comprehend and apply these data effectively. In this review we have organized the knowledge available in all of the reports on the frequencies of BoLA-DRB3 alleles. It covers information from studies made in at least 26 countries on more than 30 breeds; studies are lacking in countries that are important producers of cattle livestock. We highlight practical applications of BoLA studies for identification of markers associated with resistance to infectious and parasitic diseases, increased production traits and T cell epitope mapping, in addition to genetic diversity and conservation studies of commercial and Creole and locally adapted breeds. Finally, we provide support for the need of studies to discover new BoLA alleles and uncover unknown roles of this locus in production traits.

Comprehensive time-course gene expression evaluation of high-risk beef cattle to establish immunological characteristics associated with undifferentiated bovine respiratory disease

Bovine respiratory disease (BRD) remains the leading infectious disease in beef cattle production systems. Host gene expression upon facility arrival may indicate risk of BRD development and severity. However, a time-course approach would better define how BRD development influences immunological and inflammatory responses after disease occurrences. Here, we evaluated whole blood transcriptomes of high-risk beef cattle at three time points to elucidate BRD-associated host response. Sequenced jugular whole blood mRNA from 36 cattle (2015: n = 9; 2017: n = 27) across three time points (n = 100 samples; days [D]0, D28, and D63) were processed through ARS-UCD1.2 reference-guided assembly (HISAT2/Stringtie2). Samples were categorized into BRD-severity cohorts (Healthy, n = 14; Treated 1, n = 11; Treated 2+, n = 11) via frequency of antimicrobial clinical treatment. Assessment of gene expression patterns over time within each BRD cohort was modeled through an autoregressive hidden Markov model (EBSeq-HMM; posterior probability ≥ 0.5, FDR < 0.01). Mixed-effects negative binomial models (glmmSeq; FDR < 0.05) and edgeR (FDR < 0.10) identified differentially expressed genes between and across cohorts overtime. A total of 2,580, 2,216, and 2,381 genes were dynamically expressed across time in Healthy, Treated 1, and Treated 2+ cattle, respectively. Genes involved in the production of specialized resolving mediators (SPMs) decreased at D28 and then increased by D63 across all three cohorts. Accordingly, SPM production and alternative complement were differentially expressed between Healthy and Treated 2+ at D0, but not statistically different between the three groups by D63. Magnitude, but not directionality, of gene expression related to SPM production, alternative complement, and innate immune response signified Healthy and Treated 2+ cattle. Differences in gene expression at D63 across the three groups were related to oxygen binding and carrier activity, natural killer cell-mediated cytotoxicity, cathelicidin production, and neutrophil degranulation, possibly indicating prolonged airway pathology and inflammation weeks after clinical treatment for BRD. These findings indicate genomic mechanisms indicative of BRD development and severity over time.

First characterization of major histocompatibility complex class II DRB3 diversity in cattle breeds raised in Egypt

Genes encoding bovine leukocyte antigen (BoLA) enable the immune system to identify pathogens. Therefore, these genes have been used as genetic markers for infectious and autoimmune diseases as well as for immunological traits in cattle. Although BoLA polymorphisms have been reported in various cattle breeds worldwide, they have not been studied in cattle populations in Egypt. In this study, we characterized BoLA-DRB3 in two local Egyptian populations and one foreign population using polymerase chain reaction-sequence-based typing (PCR-SBT) method. Fifty-four previously reported BoLA-DRB3 alleles and eight new alleles (BoLA-DRB3*005:08, *015:07, *016:03, *017:04, *020:02:02, *021:03, *164:01, and *165:01) were identified. Alignment analysis of the eight new alleles revealed 90.7-98.9 %, and 83.1-97.8 % nucleotide and amino acid identities, respectively, with the BoLA-DRB3 cDNA clone NR-1. Interestingly, BoLA-DRB3 in Egyptian cattle showed a high degree of allelic diversity in native (na = 28, hE > 0.95), mixed (na = 61, hE > 0.96), and Holstein (na = 18, hE > 0.88) populations. BoLA-DRB3*002:01 (14.3 %), BoLA-DRB3*001:01 (8.5 %), and BoLA-DRB3*015:01 (20.2 %) were the most frequent alleles in native, mixed, and Holstein populations, respectively, indicating that the genetic profiles differed in each population. Based on the allele frequencies of BoLA-DRB3, genetic variation among Egyptian, Asian, African, and American breeds was examined using Nei's distances and principal component analysis. The results suggested that native and mixed cattle populations were most closely associated with African breeds in terms of their gene pool, whereas Holstein cattle were more distinct from the other breeds and were closely related to Holstein cattle populations from other countries.

Co-expression of VP2, NS1 and NS2-Nt proteins by an MVA viral vector induces complete protection against bluetongue virus

Introduction

Bluetongue (BT), caused by bluetongue virus (BTV), is an important arthropod-borne livestock disease listed by the World Organization for Animal Health. Live-attenuated and inactivated vaccines have permitted to control BT but they do not simultaneously protect against the myriad of BTV serotypes. Recently, we identified the highly conserved BTV nonstructural protein NS1 and the N-terminal region of NS2 as antigens capable of conferring multiserotype protection against BTV.

Methods

Here, we designed Modified Vaccinia Ankara (MVA) viral vectors that expressed BTV-4 proteins VP2 or VP7 along with NS1 and NS2-Nt as well as MVAs that expressed proteins VP2, VP7 or NS1 and NS2-Nt.

Results

Immunization of IFNAR(-/-) mice with two doses of MVA-NS1-2A-NS2-Nt protected mice from BTV-4M infection by the induction of an antigen-specific T cell immune response. Despite rMVA expressing VP7 alone were not protective in the IFNAR(-/-) mouse model, inclusion of VP7 in the vaccine formulation amplified the cell-mediated response induced by NS1 and NS2-Nt. Expression of VP2 elicited protective non-cross-reactive neutralizing antibodies (nAbs) in immunized animals and improved the protection observed in the MVA-NS1-2A-NS2-Nt immunized mice when these three BTV antigens were co-expressed. Moreover, vaccines candidates co-expressing VP2 or VP7 along with NS1 and NS2-Nt provided multiserotype protection. We assessed protective efficacy of both vaccine candidates in sheep against virulent challenge with BTV-4M.

Discussion

Immunization with MVA-VP7-NS1-2A-NS2-Nt partially dumped viral replication and clinical disease whereas administration of MVA-VP2-NS1-2A-NS2-Nt promoted a complete protection, preventing viraemia and the pathology produced by BTV infection.

Generation and characterization of cytochrome P450 3A74 CRISPR/Cas9 knockout bovine foetal hepatocyte cell line (BFH12)

In human, the cytochrome P450 3A (CYP3A) subfamily of drug-metabolizing enzymes (DMEs) is responsible for a significant number of phase I reactions, with the CYP3A4 isoform superintending the hepatic and intestinal metabolism of diverse endobiotic and xenobiotic compounds. The CYP3A4-dependent bioactivation of chemicals may result in hepatotoxicity and trigger carcinogenesis. In cattle, four CYP3A genes (CYP3A74, CYP3A76, CYP3A28 and CYP3A24) have been identified. Despite cattle being daily exposed to xenobiotics (e.g., mycotoxins, food additives, drugs and pesticides), the existing knowledge about the contribution of CYP3A in bovine hepatic metabolism is still incomplete. Nowadays, CRISPR/Cas9 mediated knockout (KO) is a valuable method to generate in vivo and in vitro models for studying the metabolism of xenobiotics. In the present study, we successfully performed CRISPR/Cas9-mediated KO of bovine CYP3A74, human CYP3A4-like, in a bovine foetal hepatocyte cell line (BFH12). After clonal expansion and selection, CYP3A74 ablation was confirmed at the DNA, mRNA, and protein level. The subsequent characterization of the CYP3A74 KO clone highlighted significant transcriptomic changes (RNA-sequencing) associated with the regulation of cell cycle and proliferation, immune and inflammatory response, as well as metabolic processes. Overall, this study successfully developed a new CYP3A74 KO in vitro model by using CRISPR/Cas9 technology, which represents a novel resource for xenobiotic metabolism studies in cattle. Furthermore, the transcriptomic analysis suggests a key role of CYP3A74 in bovine hepatocyte cell cycle regulation and metabolic homeostasis.

Identifying major histocompatibility complex class II-DR molecules in bovine and swine peripheral blood monocyte-derived macrophages using mAb-L243

Major histocompatibility complex class II (MHC-II) molecules are involved in immune responses against pathogens and vaccine candidates' immunogenicity. Immunopeptidomics for identifying cancer and infection-related antigens and epitopes have benefited from advances in immunopurification methods and mass spectrometry analysis. The mouse anti-MHC-II-DR monoclonal antibody L243 (mAb-L243) has been effective in recognising MHC-II-DR in both human and non-human primates. It has also been shown to cross-react with other animal species, although it has not been tested in livestock. This study used mAb-L243 to identify Staphylococcus aureus and Salmonella enterica serovar Typhimurium peptides binding to cattle and swine macrophage MHC-II-DR molecules using flow cytometry, mass spectrometry and two immunopurification techniques. Antibody cross-reactivity led to identifying expressed MHC-II-DR molecules, together with 10 Staphylococcus aureus peptides in cattle and 13 S. enterica serovar Typhimurium peptides in swine. Such data demonstrates that MHC-II-DR expression and immunocapture approaches using L243 mAb represents a viable strategy for flow cytometry and immunopeptidomics analysis of bovine and swine antigen-presenting cells.

Transcriptome analysis reveals immune function-related mRNA expression in donkey mammary glands during four developmental stages

The low susceptibility to mastitis of female donkey (jenny) mammary glands and the strong immune properties of donkey milk are acknowledged, but little is known about the genes involved in mammary gland immunity in jennies. Herein, we used RNA-sequencing and bioinformatics analyses to explore jenny mammary gland transcriptomes and detect potential functional differentially expressed (DE) mRNAs related to immunity during four specific developmental stages: foetal (F), pubertal (P), adult parous nonlactation (N) and lactation (L). A total of 2497, 583 and 1820 DE mRNAs were identified in jenny mammary glands at F vs. P, P vs. N, and N vs. L, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) analyses revealed numerous GO terms related to immune function, especially between F and P. Seven significantly enriched profiles were identified, among which 497 and 1261 DE mRNAs were upregulated in profiles 19 and 17. Eleven mRNAs were enriched in over 10 KEGG pathways. β-2-microglobulin (B2M), immunoglobulin heavy constant mu (IGHM), toll like receptor 2 (TLR2), toll like receptor 4 (TLR4) and myeloid differentiation factor 88 (MYD88) were mainly involved in phosphoinositide 3-kinase (PI3K)-Akt signalling, phagosome and nuclear factor kappa-B (NF-kappa B) signalling pathways. The findings provide insight into the molecular features underpinning the low prevalence of intramammary infections (i.e., mastitis) in donkeys.

Evidence for selective sweeps in the MHC gene repertoire of various cattle breeds

Major Histocompatibility Complex (MHC) genes are among the immune genes that have been extensively studied in vertebrates and are necessary for adaptive immunity. In the immunological response to infectious diseases, they play several significant roles. This research paper provides the selection signatures in the MHC region of the bovine genome as well as how certain genes related to innate immunity are undergoing a positive selective sweep. Here, we investigated signatures of historical selection on MHC genes in 15 different cattle populations and a total of 427 individuals. To identify the selection signatures, we have used three separate summary statistics. The findings show potential selection signatures in cattle from whom we isolated genes involved in the MHC. The most significant regions related to the bovine MHC are BOLA, non-classical MHC class I antigen (BOLA-NC1), Microneme protein 1 (MIC1) , Cluster of Differentiation 244 (CD244), Gap Junction Alpha-5 Protein (GJA5). It will be possible to gain new insight into immune system evolution by understanding the distinctive characteristics of MHC in cattle.

A case of forensic genomics in Uganda reveals animal ownership and low exotic genetic introgression in indigenous cattle

BACKGROUND

The cattle industry contributes to Uganda's agricultural output. It faces challenges that include theft and parentage ascertainment. These challenges can benefit from recent molecular genomics and bioinformatics technologies.

OBJECTIVES

We employed genomic analyses to establish potential ownership of a group of nine cattle that were being claimed by two farmers in Uganda. We investigated the genetic relationship of Ugandan cattle with regional indigenous breeds as well as exotic breeds that are currently present in Uganda. In addition, we investigated regions that are likely to be under selection in the Ugandan cattle.

METHODS

Hair samples were collected from seven and two animals from farmers A and B, respectively. They were genotyped for 53,218 Single Nucleotide Polymorphism markers. To establish genetic relationships between the sampled animals, we performed genomic analyses including, principal component analysis (PCA), hierarchical clustering analysis and identity by state/descent. We also performed admixture and runs of homozygosity analyses to assess the ancestry composition and identify regions potentially under selection in Ugandan cattle, respectively.

RESULTS

The seven animals from Farmer A were genetically close to each other but showed minimal relationship with the disputed animals. The two animals from Farmer B were genetically distant from each other but showed greater similarity to four of the disputed animals. Four of the disputed animals showed great dissimilarity from the animals of both farmers. Comparison of these with the reference breeds revealed minimal European exotic genetic introgression into these animals, but rather high similarity to the Sheko. Results also revealed high homozygosity in the major histocompatibility complex regions.

CONCLUSIONS

Our results demonstrate the use of currently available genomic tools to empirically establish the ownership of cattle; these could be scaled up as a resourceful and viable tool that could be employed to support conflict resolution where reliable livestock identification is unavailable.

Genes related to heat tolerance in cattle-a review

Heat stress is described as the cumulative detrimental effect caused by an imbalance between heat production within the body and heat dissipation. When cattle are exposed to heat stress with skin surface temperatures exceeding 35 °C, gene networks within and across cells respond to environmental heat loads with both intra and extracellular signals that coordinate cellular and whole-animal metabolism changes to store heat and rapidly increase evaporative heat loss. In this study, we examined evidence from genes known to be associated with heat tolerance (Hsp70, HSF1, HspB8, SOD1, PRLH, ATP1A1, MTOR, and EIF2AK4). This information could serve as valuable resource material for breeding programs aimed at increasing the thermotolerance of cattle.

Transcriptome-wide mapping of milk somatic cells upon subclinical mastitis infection in dairy cattle

BACKGROUND

Subclinical intramammary infection (IMI) represents a significant problem in maintaining dairy cows' health. Disease severity and extent depend on the interaction between the causative agent, environment, and host. To investigate the molecular mechanisms behind the host immune response, we used RNA-Seq for the milk somatic cells (SC) transcriptome profiling in healthy cows (n = 9), and cows naturally affected by subclinical IMI from Prototheca spp. (n = 11) and Streptococcus agalactiae (S. agalactiae; n = 11). Data Integration Analysis for Biomarker discovery using Latent Components (DIABLO) was used to integrate transcriptomic data and host phenotypic traits related to milk composition, SC composition, and udder health to identify hub variables for subclinical IMI detection.

RESULTS

A total of 1,682 and 2,427 differentially expressed genes (DEGs) were identified when comparing Prototheca spp. and S. agalactiae to healthy animals, respectively. Pathogen-specific pathway analyses evidenced that Prototheca's infection upregulated antigen processing and lymphocyte proliferation pathways while S. agalactiae induced a reduction of energy-related pathways like the tricarboxylic acid cycle, and carbohydrate and lipid metabolism. The integrative analysis of commonly shared DEGs between the two pathogens (n = 681) referred to the core-mastitis response genes, and phenotypic data evidenced a strong covariation between those genes and the flow cytometry immune cells (r² = 0.72), followed by the udder health (r² = 0.64) and milk quality parameters (r² = 0.64). Variables with r ≥ 0.90 were used to build a network in which the top 20 hub variables were identified with the Cytoscape cytohubba plug-in. The genes in common between DIABLO and cytohubba (n = 10) were submitted to a ROC analysis which showed they had excellent predictive performances in terms of discriminating healthy and mastitis-affected animals (sensitivity > 0.89, specificity > 0.81, accuracy > 0.87, and precision > 0.69). Among these genes, CIITA could play a key role in regulating the animals' response to subclinical IMI.

CONCLUSIONS

Despite some differences in the enriched pathways, the two mastitis-causing pathogens seemed to induce a shared host immune-transcriptomic response. The hub variables identified with the integrative approach might be included in screening and diagnostic tools for subclinical IMI detection.

Comparative expression analysis of water buffalo (Bubalus bubalis) to identify genes associated with economically important traits

The milk, meat, skins, and draft power of domestic water buffalo (Bubalus bubalis) provide substantial contributions to the global agricultural economy. The world's water buffalo population is primarily found in Asia, and the buffalo supports more people per capita than any other livestock species. For evaluating the workflow, output rate, and completeness of transcriptome assemblies within and between reference-free (RF) de novo transcriptome and reference-based (RB) datasets, abundant bioinformatics studies have been carried out to date. However, comprehensive documentation of the degree of consistency and variability of the data produced by comparing gene expression levels using these two separate techniques is lacking. In the present study, we assessed the variations in the number of differentially expressed genes (DEGs) attained with RF and RB approaches. In light of this, we conducted a study to identify, annotate, and analyze the genes associated with four economically important traits of buffalo, viz., milk volume, age at first calving, post-partum cyclicity, and feed conversion efficiency. A total of 14,201 and 279 DEGs were identified in RF and RB assemblies. Gene ontology (GO) terms associated with the identified genes were allocated to traits under study. Identified genes improve the knowledge of the underlying mechanism of trait expression in water buffalo which may support improved breeding plans for higher productivity. The empirical findings of this study using RNA-seq data-based assembly may improve the understanding of genetic diversity in relation to buffalo productivity and provide important contributions to answer biological issues regarding the transcriptome of non-model organisms.

The eQTL colocalization and transcriptome-wide association study identify potentially causal genes responsible for economic traits in Simmental beef cattle

BACKGROUND

A detailed understanding of genetic variants that affect beef merit helps maximize the efficiency of breeding for improved production merit in beef cattle. To prioritize the putative variants and genes, we ran a comprehensive genome-wide association studies (GWAS) analysis for 21 agronomic traits using imputed whole-genome variants in Simmental beef cattle. Then, we applied expression quantitative trait loci (eQTL) mapping between the genotype variants and transcriptome of three tissues (longissimus dorsi muscle, backfat, and liver) in 120 cattle.

RESULTS

We identified 1,580 association signals for 21 beef agronomic traits using GWAS. We then illuminated 854,498 cis-eQTLs for 6,017 genes and 46,970 trans-eQTLs for 1,903 genes in three tissues and built a synergistic network by integrating transcriptomics with agronomic traits. These cis-eQTLs were preferentially close to the transcription start site and enriched in functional regulatory regions. We observed an average of 43.5% improvement in cis-eQTL discovery using multi-tissue eQTL mapping. Fine-mapping analysis revealed that 111, 192, and 194 variants were most likely to be causative to regulate gene expression in backfat, liver, and muscle, respectively. The transcriptome-wide association studies identified 722 genes significantly associated with 11 agronomic traits. Via the colocalization and Mendelian randomization analyses, we found that eQTLs of several genes were associated with the GWAS signals of agronomic traits in three tissues, which included genes, such as NADSYN1, NDUFS3, LTF and KIFC2 in liver, GRAMD1C, TMTC2 and ZNF613 in backfat, as well as TIGAR, NDUFS3 and L3HYPDH in muscle that could serve as the candidate genes for economic traits.

CONCLUSIONS

The extensive atlas of GWAS, eQTL, fine-mapping, and transcriptome-wide association studies aid in the suggestion of potentially functional variants and genes in cattle agronomic traits and will be an invaluable source for genomics and breeding in beef cattle.

Functional immune diversity in reindeer reveals a high Arctic population at risk

Climate changes the geographic range of both species as well as pathogens, causing a potential increase in the vulnerability of populations or species with limited genetic diversity. With advances in high throughput sequencing (HTS) technologies, we can now define functional expressed genetic diversity of wild species at a larger scale and identify populations at risk. Previous studies have used genomic DNA to define major histocompatibility complex (MHC) class II diversity in reindeer. Varying numbers of expressed genes found in many ungulates strongly argues for using cDNA in MHC typing strategies to ensure that diversity estimates relate to functional genes. We have used available reindeer genomes to identify candidate genes and established an HTS approach to define expressed MHC class I and class II diversity. To capture a broad diversity we included samples from wild reindeer from Southern Norway, semi-domesticated reindeer from Northern Norway and reindeer from the high Artic archipelago Svalbard. Our data show a medium MHC diversity in semi-domesticated and wild Norwegian mainland reindeer, and low MHC diversity reindeer in Svalbard reindeer. The low immune diversity in Svalbard reindeer provides a potential risk if the pathogenic pressure changes in response to altered environmental conditions due to climate change, or increased human-related activity.

Bovine leukemia virus: a perspective insight into the infection and immunity

Bovine leukemia virus (BLV) is a member of the Retroviridae family and belongs to the Deltaretrovirus genus. It has a close relationship with human T-cell leukemia virus type I. BLV is responsible for causing enzootic bovine leukosis (EBL), a contagious disease that affects the bovine lymphatic system. This virus poses challenges for the global cattle industry, as it impacts cattle populations all over the world. Despite being widespread and impactful, BLV often goes unnoticed, with many researchers unaware of its presence and the potential consequences it carries. BLV demonstrates varying levels of pathogenicity. The majority of cattle (around 70%) become seropositive asymptomatic carriers, displaying no noticeable clinical symptoms. However, a smaller proportion of infected animals experience persistent lymphocytosis, characterized by an elevated number of lymphocytes in the bloodstream. If not monitored and managed, a subset of these persistently infected cattle may advance to lymphosarcoma. This condition typically presents as tumors in different lymphoid tissues, impacting various organs and overall health and productivity. Furthermore, recent research has highlighted the potential association between the occurrence of breast and lung cancer in humans and the presence of BLV. This review will delve into the recent discoveries concerning BLV, specifically exploring its epidemiology, the economic impact it has on the global cattle industry, its implications for human medicine, and the association between different alleles of the major histocompatibility complex (MHC) and susceptibility or resistance to BLV. Bovine leukemia virus, Enzootic bovine leukosis, Major histocompatibility complex, Retroviridae.

Unravelling the genetics of non-random fertilization associated with gametic incompatibility

In the dairy industry, mate allocation is dependent on the producer's breeding goals and the parents' breeding values. The probability of pregnancy differs among sire-dam combinations, and the compatibility of a pair may vary due to the combination of gametic haplotypes. Under the hypothesis that incomplete incompatibility would reduce the odds of fertilization, and complete incompatibility would lead to a non-fertilizing or lethal combination, deviation from Mendelian inheritance expectations would be observed for incompatible pairs. By adding an interaction to a transmission ratio distortion (TRD) model, which detects departure from the Mendelian expectations, genomic regions linked to gametic incompatibility can be identified. This study aimed to determine the genetic background of gametic incompatibility in Holstein cattle. A total of 283,817 genotyped Holstein trios were used in a TRD analysis, resulting in 422 significant regions, which contained 2075 positional genes further investigated for network, overrepresentation, and guilt-by-association analyses. The identified biological pathways were associated with immunology and cellular communication and a total of 16 functional candidate genes were identified. Further investigation of gametic incompatibility will provide opportunities to improve mate allocation for the dairy cattle industry.

Detection of potential functional variants based on systems-biology: the case of feed efficiency in beef cattle

BACKGROUND

Potential functional variants (PFVs) can be defined as genetic variants responsible for a given phenotype. Ultimately, these are the best DNA markers for animal breeding and selection, especially for polygenic and complex phenotypes. Herein, we described the identification of PFVs for complex phenotypes (in this case, Feed Efficiency in beef cattle) using a systems-biology driven approach based on RNA-seq data from physiologically relevant organs.

RESULTS

The systems-biology coupled with deep molecular phenotyping by RNA-seq of liver, muscle, hypothalamus, pituitary, and adrenal glands of animals with high and low feed efficiency (FE) measured by residual feed intake (RFI) identified 2,000,936 uniquely variants. Among them, 9986 variants were significantly associated with FE and only 78 had a high impact on protein expression and were considered as PFVs. A set of 169 significant uniquely variants were expressed in all five organs, however, only 27 variants had a moderate impact and none of them a had high impact on protein expression. These results provide evidence of tissue-specific effects of high-impact PFVs. The PFVs were enriched (FDR < 0.05) for processing and presentation of MHC Class I and II mediated antigens, which are an important part of the adaptive immune response. The experimental validation of these PFVs was demonstrated by the increased prediction accuracy for RFI using the weighted G matrix (ssGBLUP+wG; Acc = 0.10 and b = 0.48) obtained in the ssGWAS in comparison to the unweighted G matrix (ssGBLUP; Acc = 0.29 and b = 1.10).

CONCLUSION

Here we identified PFVs for FE in beef cattle using a strategy based on systems-biology and deep molecular phenotyping. This approach has great potential to be used in genetic prediction programs, especially for polygenic phenotypes.

Genetic Diversity and Selective Signature in Dabieshan Cattle Revealed by Whole-Genome Resequencing

Simple Summary

To protect the genetic resources of Chinese native cattle breeds, we investigated the genetic structure, genetic diversity and genetic signature from artificial or natural selection by sequencing 32 bovine genomes from the breeding farm of the Dabieshan population. We discovered that the ancestral contributions of Dabieshan originated from Chinese indicine and East Asian taurine on the autosomal genome, which had abundant genomic diversity. Some candidate genes associated with fertility, feed efficiency, fat deposition, immune response, heat resistance and the coat color were identified by a selective sweep. The SNPs data were based on genomics, which could establish a foundation for breed amelioration and support conservation for indigenous cattle breeds.

Abstract

Dabieshan cattle are a typical breed of southern Chinese cattle that have the characteristics of muscularity, excellent meat quality and tolerance to temperature and humidity. Based on 148 whole-genome data, our analysis disclosed the ancestry components of Dabieshan cattle with Chinese indicine (0.857) and East Asian taurine (0.139). The Dabieshan genome demonstrated a higher genomic diversity compared with the other eight populations, supported by the observed nucleotide diversity, linkage disequilibrium decay and runs of homozygosity. The candidate genes were detected by a selective sweep, which might relate to the fertility (GPX5, GPX6), feed efficiency (SLC2A5), immune response (IGLL1, BOLA-DQA2, BOLA-DQB), heat resistance (DnaJC1, DnaJC13, HSPA4), fat deposition (MLLT10) and the coat color (ASIP). We also identified the “East Asian taurine-like” segments in Dabieshan cattle, which might contribute to meat quality traits. The results revealed by the unique and valuable genomic data can build a foundation for the genetic improvement and conservation of genetic resources for indigenous cattle breeds.

Transcriptional changes in the peripheral blood leukocytes from Brangus cattle before and after tick challenge with Rhipicephalus australis

Background

Disease emergence and production loss caused by cattle tick infestations have focused attention on genetic selection strategies to breed beef cattle with increased tick resistance. However, the mechanisms behind host responses to tick infestation have not been fully characterised. Hence, this study examined gene expression profiles of peripheral blood leukocytes from tick-naive Brangus steers (Bos taurus x Bos indicus) at 0, 3, and 12 weeks following artificial tick challenge experiments with Rhipicephalus australis larvae. The aim of the study was to investigate the effect of tick infestation on host leukocyte response to explore genes associated with the expression of high and low host resistance to ticks.

Results

Animals with high (HR, n = 5) and low (LR, n = 5) host resistance were identified after repeated tick challenge. A total of 3644 unique differentially expressed genes (FDR < 0.05) were identified in the comparison of tick-exposed (both HR and LR) and tick-naive steers for the 3-week and 12-week infestation period. Enrichment analyses showed genes were involved in leukocyte chemotaxis, coagulation, and inflammatory response. The IL-17 signalling, and cytokine-cytokine interactions pathways appeared to be relevant in protection and immunopathology to tick challenge. Comparison of HR and LR phenotypes at timepoints of weeks 0, 3, and 12 showed there were 69, 8, and 4 differentially expressed genes, respectively. Most of these genes were related to immune, tissue remodelling, and angiogenesis functions, suggesting this is relevant in the development of resistance or susceptibility to tick challenge.

Conclusions

This study showed the effect of tick infestation on Brangus cattle with variable phenotypes of host resistance to R. australis ticks. Steers responded to infestation by expressing leukocyte genes related to chemotaxis, cytokine secretion, and inflammatory response. The altered expression of genes from the bovine MHC complex in highly resistant animals at pre- and post- infestation stages also supports the relevance of this genomic region for disease resilience. Overall, this study offers a resource of leukocyte gene expression data on matched tick-naive and tick-infested steers relevant for the improvement of tick resistance in composite cattle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08686-3.

Phenotypic Selection of Dairy Cattle Infected with Bovine Leukemia Virus Demonstrates Immunogenetic Resilience through NGS-Based Genotyping of BoLA MHC Class II Genes

Characterization of the bovine leukocyte antigen (BoLA) DRB3 gene has shown that specific alleles associate with susceptibility or resilience to the progression of bovine leukemia virus (BLV), measured by proviral load (PVL). Through surveillance of multi-farm BLV eradication field trials, we observed differential phenotypes within seropositive cows that persist from months to years. We sought to develop a multiplex next-generation sequencing workflow (NGS-SBT) capable of genotyping 384 samples per run to assess the relationship between BLV phenotype and two BoLA genes. We utilized longitudinal results from milk ELISA screening and subsequent blood collections on seropositive cows for PVL determination using a novel BLV proviral load multiplex qPCR assay to phenotype the cows. Repeated diagnostic observations defined two distinct phenotypes in our study population, ELISA-positive cows that do not harbor detectable levels of provirus and those who do have persistent proviral loads. In total, 565 cows from nine Midwest dairy farms were selected for NGS-SBT, with 558 cows: 168 BLV susceptible (ELISA-positive/PVL-positive) and 390 BLV resilient (ELISA-positive/PVL-negative) successfully genotyped. Three BoLA-DRB3 alleles, including one novel allele, were shown to associate with disease resilience, *009:02, *044:01, and *048:02 were found at rates of 97.5%, 86.5%, and 90.3%, respectively, within the phenotypically resilient population. Alternatively, DRB3*015:01 and *027:03, both known to associate with disease progression, were found at rates of 81.1% and 92.3%, respectively, within the susceptible population. This study helps solidify the immunogenetic relationship between BoLA-DRB3 alleles and BLV infection status of these two phenotypic groupings of US dairy cattle.

Bos taurus haplotypes segregating in Nellore (Bos indicus) cattle

Brazil is the largest exporter of beef in the world, and most of that beef derives from Nellore cattle. Although considered a zebu breed (Bos indicus), the history of Nellore cattle in Brazil is marked by the importation of bulls from India, the use of a Creole taurine (Bos taurus) maternal lineage to quickly expand the herds and backcrossing to Nellore bulls to recover zebu ancestry. As a consequence, the current Brazilian Nellore population carries an average taurine ancestry of approximately 1%. Although that percentage seems small, some taurine variants deviate substantially from that average, with the better-known cases being the PLAG1-Q haplotype involved with body size variation and the Guarani (P_G ) polled variant producing hornless animals. Here, we report taurine haplotypes in 9074 Nellore animals genotyped for 539 657 imputed SNP markers. Apart from PLAG1-Q and P_G , our analysis further revealed common taurine haplotypes (>3%) spanning genes related to immunity, growth, reproduction and hair and skin phenotypes. Using data from 22 economically important traits, we showed that many of the major QTL previously reported in the breed are at least partially driven by taurine haplotypes. As B. taurus and B. indicus haplotypes are highly divergent, presenting widely different sets of functional variants, our results provide promising targets for future scrutiny in Nellore cattle.

Allelic diversity at BoLA DRB3 locus and association with predisposition to clinical mastitis in indicus and crossbred cattle

Bovine lymphocyte antigen (BoLA) DRB3 locus in healthy and mastitis affected cattle has been genotyped by a polymerase chain reaction and restriction fragment length polymorphisms (PCR-RLFP) using RsaI restriction enzyme, followed by sequencing. In 130 farm animals, 25 BoLA DRB3 alleles have been detected by PCR-RFLP. Three distinct allelic patterns significantly associated with mastitis in Karan Fries crossbred and Sahiwal indicus cattle have been identified, whereas, four other allelic patterns were significantly high in frequency among healthy animals. Sequencing of RFLP genotypes revealed 25 and 47 alleles among healthy Sahiwal and Karan Fries, respectively, while 17 and 38 patterns observed in mastitis affected Sahiwal and Karan Fries animals, respectively. From Tajima's D-test of neutrality, it was concluded that alleles associated with mastitis were expanding in the population, whereas those of healthy were under contraction. Phylogenetic analysis carried out to delineate the evolutionary relationship of the farm and field animals at DRB3 locus, differentiating allelic patterns into six different clusters. Among the phylogenetic lineages, five patterns DRB3*028:01, DRB3*011:03, DRB3*031:01, DRB3*001:01 and DRB3*043:01, were previously reported, whereas one novel allelic variant was observed in indicus and crossbred cattle. This information will help in further exploring the association between BoLA-DRB3 genetic diversity and disease resistance in distinct cattle breeds, important in designing breeding strategies for increasing the distribution of favorable alleles.

Molecular and phylogenetic analysis of MHC class I exons 7-8 in a variety of cattle and buffalo breeds

The present study was conducted on the MHC class I (BoLA-A/BuLA-A) gene in Sahiwal, Jersey, Hariana, and Tharparkar breeds of cattle and Murrah, Mehsana, and Bhadawari breeds of buffalo to study the polymorphism. Exons 7-8 of the MHC class I gene was first characterized for polymorphism study in buffalo and the results reveal that this gene has a higher level of nucleotide changes than the cattle. Genes were investigated for polymorphisms in 285 animals of cattle and buffalo breeds. Molecular characterization of the MHC class I (BoLa-A/Bula-A) gene reveals a higher degree of polymorphism at the nucleotide level in cattle and buffalo. Results revealed this region has a higher level of polymorphisms in buffalo as campared to the cattle. Alul restriction patterns were monomorphic except for three different patterns but it was able to illustrate the differences in buffalo and cattle. SSCP analysis of exons 7-8 showed remarkable differences in cattle and buffalo. Sequence analysis revealed more closeness of Murrah breed with crossbred and indigenous cattle than Holstein Friesian. Exon 8 had more deletion and stop codon as compared to exon 7. The investigation confirmed that MHC class I BoLa-A/Bula-A exons 7-8 is highly polymorphic in buffalo as compared to cattle.

Adaptive selection signatures in river buffalo with emphasis on immune and major histocompatibility complex genes

River buffalo is an agriculturally important species with many traits, such as disease tolerance, which promote its use worldwide. Highly contiguous genome assemblies of the river buffalo, goat, pig, human and two cattle subspecies were aligned to study gene gains and losses and signs of positive selection. The gene families that have changed significantly in river buffalo since divergence from cattle play important roles in protein degradation, the olfactory receptor system, detoxification and the immune system. We used the branch site model in PAML to analyse single-copy orthologs to identify positively selected genes that may be involved in skin differentiation, mammary development and bone formation in the river buffalo branch. The high contiguity of the genomes enabled evaluation of differences among species in the major histocompatibility complex. We identified a Babesia-like L1 LINE insertion in the DRB1-like gene in the river buffalo and discuss the implication of this finding.

Association Between BoLA-DRB3.2 Polymorphism and Bovine Papillomavirus Infection for Bladder Tumor Risk in Podolica Cattle

Blood samples from 260 unrelated cattle (132 animals affected by papillomavirus-associated bladder tumors and 128 healthy) were genotyped using the classic polymerase chain reaction/restriction fragment length polymorphism method to screen MHC class II bovine leukocyte antigen-DRB3. 2 polymorphism. The DRB3^*22 allele was significantly (p ≤ 0.01) detected in healthy cattle, thus appearing to have a negative association (protective effect) with virus infection of the urinary bladder known to represent a bladder tumor risk for cattle living free at pasture. Considering the two sequence alleles identified in animals carrying DRB3^*22, DRB3^*011:01 allele from samples of animals harboring the unexpressed bovine papillomaviruses (BPV)-2 E5 gene was characterized by amino acid residues believed to have a protective effect against BPV infection such as arginine at position 71 (R⁷¹) in pocket 4, histidine at position 11 (H¹¹) in pocket 6, and both glutamine at position 9 (Q⁹) and serine at position 57 (S⁵⁷) in pocket 9 of the antigen-binding groove. The DRB3^*011:02v allele from affected animals was characterized by amino acids believed to be susceptibility residues such as lysine (K⁷¹), tyrosine (Y¹¹), glutamic acid (E⁹), and aspartic acid (D⁵⁷) in these pockets. These results suggest that animals harboring the DRB3^*011:01 allele may have a lower risk of BPV infection and, consequently, a reduced risk of bladder tumors.

Genetic Variation and Population Differentiation in the Bovine Lymphocyte Antigen DRB3.2 Locus of South African Nguni Crossbred Cattle

Simple Summary

Indigenous cattle breeds are important to their native environment as they confer significant and often unique adaptability traits. The Nguni is one such breeds that is indigenous to the Southern African region. This breed confers resistance to thermal stress and diseases, amongst other factors. The bovine major histocompatibility complex is an important region, which codes for alleles that have been associated with a plethora of diseases. In the current study, the genetic diversity within this region was assessed in Nguni crossbred cattle. This was done to detect the gene pool of the Nguni breed, and to identify genes that might be important within this breed. The populations displayed a high degree of genetic diversity, and some alleles were common throughout the populations and accounted for a significant portion of the total alleles. This high genetic diversity could account for the great adaptability of the Nguni breed to Southern Africa.

Abstract

The bovine lymphocyte antigen (BoLA-DRB3) gene is an important region that codes for glycoproteins responsible for the initiation of an immune response. BoLA-DRB3 alleles have been demonstrated to be associated with disease resistance/tolerance. Therefore, great genetic diversity is correlated with better adaptation, fitness, and robustness. The current study was conducted to assess the population genetic structure of the BoLA-DRB3 gene in Nguni crossbred cattle using polymerase chain reaction-sequence based typing (PCR-SBT). High genetic diversity was detected, with 30 alleles, 11 of which are novel to the study. Alleles DRB3*0201, DRB3*0701, DRB*0901, and DRB*1601 were present in all populations and accounted for nearly around 50% of all observed alleles. A mean genetic diversity (H_E) of 0.93 was detected. The high overall genetic diversity is possibly associated with pathogen-assisted selection and heterozygote advantage. Such high diversity might explain the hardiness of the Nguni crossbred cattle to the Southern African region. Low population genetic structure was identified (F_ST = 0.01), suggesting possible gene flow between populations and retention of similar alleles. The study was undertaken to bridge the dearth of such studies in South African breeds and it is imperative for effective sustainability of indigenous breeds and the implementation of effective breeding strategies.

Integral Use of Immunopeptidomics and Immunoinformatics for the Characterization of Antigen Presentation and Rational Identification of BoLA-DR-Presented Peptides and Epitopes

MHC peptide binding and presentation is the most selective event defining the landscape of T cell epitopes. Consequently, understanding the diversity of MHC alleles in a given population and the parameters that define the set of ligands that can be bound and presented by each of these alleles (the immunopeptidome) has an enormous impact on our capacity to predict and manipulate the potential of protein Ags to elicit functional T cell responses. Liquid chromatography-mass spectrometry analysis of MHC-eluted ligand data has proven to be a powerful technique for identifying such peptidomes, and methods integrating such data for prediction of Ag presentation have reached a high level of accuracy for both MHC class I and class II. In this study, we demonstrate how these techniques and prediction methods can be readily extended to the bovine leukocyte Ag class II DR locus (BoLA-DR). BoLA-DR binding motifs were characterized by eluted ligand data derived from bovine cell lines expressing a range of DRB3 alleles prevalent in Holstein-Friesian populations. The model generated (NetBoLAIIpan, available as a Web server at www.cbs.dtu.dk/services/NetBoLAIIpan) was shown to have unprecedented predictive power to identify known BoLA-DR-restricted CD4 epitopes. In summary, the results demonstrate the power of an integrated approach combining advanced mass spectrometry peptidomics with immunoinformatics for characterization of the BoLA-DR Ag presentation system and provide a prediction tool that can be used to assist in rational evaluation and selection of bovine CD4 T cell epitopes.

Genetic assessment of BoLA-DRB3 polymorphisms by comparing Bangladesh, Ethiopian, and Korean cattle

Attributable to their major function in pathogen recognition, the use of bovine leukocyte antigens (BoLA) as disease markers in immunological traits in cattle is well established. However, limited report exists on polymorphism of the BoLA gene in zebu cattle breeds by high resolution typing methods. Thus, we used a polymerase chain reaction sequence-based typing (PCR-SBT) method to sequence exon 2 of the BoLA class II DRB3 gene from 100 animals (Boran, n = 13; Sheko, n = 20; Fogera, n = 16; Horro, n = 19), Hanwoo cattle (n = 18) and Bangladesh Red Chittagong zebu (n = 14). Out of the 59 detected alleles, 43 were already deposited under the Immuno Polymorphism Database for major histocompatibility complex (IPD-MHC) while 16 were unique to this study. Assessment of the level of genetic variability at the population and sequence levels with genetic distance in the breeds considered in this study showed that Zebu breeds had a gene diversity score greater than 0.752, nucleotide diversity score greater than 0.152, and mean number of pairwise differences higher than 14, being very comparable to those investigated for other cattle breeds. Regarding neutrality tests analyzed, we investigated that all the breeds except Hanwoo had an excess number of alleles and could be expected from a recent population expansion or genetic hitchhiking. Howbeit, the observed heterozygosity was not significantly (p < 0.05) higher than the expected heterozygosity. The Hardy Weinberg equilibrium (HWE) analysis revealed non-significant excess of heterozygote animals, indicative of plausible over-dominant selection. The pairwise FST values suggested a low genetic variation among all the breeds (FST = 0.056; p < 0.05), besides the rooting from the evolutionary or domestication history of the cattle. No detached clade was observed in the evolutionary divergence study of the BoLA-DRB3 gene, inferred from the phylogenetic tree based on the maximum likelihood model. The investigation herein indicated the clear differences in BoLA-DRB3 gene variability between African and Asian cattle breeds.

Genetic variability and biodiversity of Ukrainian Gray cattle by the BoLA-DRB3 gene

At the current stage of genetic studies of cattle, more and more attention is being drawn to autochthonous breeds. Native cattle have a number of prominent phenotypic traits and have preserved unique genes and their combinations lost by modern commercial breeds, which would be valuable to use in selective programs. We surveyed polymorphism of the Ukrainian autochthonous Gray breed according to alleles of exon 2 of the BoLA-DRB3 gene. The uniqueness of the gene lies in the broad variability of its allele variants. Significant informativeness at DNA level is quite important for genetic studies. We surveyed allele polymorphism using the PCR-RLFP method on DNA isolated from 88 samples of blood of cows and 5 samples of sperm. We identified 28 alleles, of which 23 variants were nomenclature ones and 5 (jba, *jab, *jbb, *nad and *nda) were “without established nomenclature”, their share accounting for 8.9%. Four alleles *06, *12, *16 and *jba had a frequency above 5% and occupied 69.9% of the breed’s allele fund overall. The commonest allele was BoLA-DRB3.2*16 (44.1%). In total, we found 40 genotypes. Considering the significant dominance of variant *16, as expected, 5 genotypes with its inclusion occurred: *16/*16, *12/*16, *06/*16, *16/*24 and *jba/*16. It was present in the genotype of two out three studied animals. Parameters of heterozygosity, effective number of alleles, Shannon and Pielou indices indicate that Ukrainian Gray cattle are characterized by lowest level of genetic variability and biodiversity according to the BoLA-DRB3 gene compared with other breeds. Due to significant dominance of allele *16, the breed has no inbred motifs. We noted deviation toward increase in homozygosity without deviations from the norm of the distribution according to Hardy-Weinberg equilibrium. The obtained results will be used for genetic-populational programs with the purpose of improving the genetic potential of cattle breeds in terms of economically beneficial traits and diseases of cattle.

The Tip Region on VP2 Protein of Bluetongue Virus Contains Potential IL-4-Inducing Amino Acid Peptide Segments

Bluetongue is an infectious viral hemorrhagic disease of domestic and wild ruminants that has a considerable economic impact on domestic ruminants. There are currently at least 29 serotypes of bluetongue virus (BTV) in the world. Noteworthily, the pathogenesis among BTV serotypes is different, even in the same animal species. In this study, BTV2/KM/2003 and BTV12/PT/2003 were used to investigate the differential immunological effects on bovine peripheral blood mononuclear cells (PBMCs). The BTV viral load and the expression of cytokine messenger RNA (mRNA) in PBMCs were measured by fluorescence-based real-time reverse-transcription PCR (qRT-PCR). The immunofluorescence assay (IFA) was applied to detect BTV signals in monocyte-derived macrophages (MDMs). The SWISS-MODEL and IL-4pred prediction tools were used to predict the interleukin 4 (IL-4)-inducing peptides in BTV-coat protein VP2. Synthetic peptides of VP2 were used to stimulate PBMCs for IL-4-inducing capability. This study demonstrated that the cytokine profiles of BTV-induced PBMCs were significantly different between BTV2/KM/2003 and BTV12/PT/2003. BTV2 preferentially activated the T helper 2 (Th2) pathway, represented by the early induction of IL-4, and likely fed back to inhibit the innate immunity. In contrast, BTV12 preferentially activated the innate immunity, represented by the induction of tumor necrosis factor -α (TNF-α) and interleukin 1 (IL-1), with only minimal subsequent IL-4. The BTV nonstructural protein 3 antibody (anti-BTV-NS3) fluorescent signals demonstrated that monocytes in PBMCs and MDMs were the preferred targets of BTV replication. Bioinformatics analysis revealed that the capability to induce IL-4 was attributed to the tip region of the VP2 protein, wherein a higher number of predicted peptide segments on BTVs were positively correlated with the allergic reaction reported in cattle. Synthetic peptides of BTV2-VP2 induced significant IL-4 within 12-24 h post-infection (hpi) in PBMCs, whereas those of BTV12 did not, consistent with the bioinformatics prediction. Bovine PBMCs and synthetic peptides together seem to serve as a good model for pursuing the BTV-induced IL-4 activity that precedes the development of an allergic reaction, although further optimization of the protocol is warranted.

Immunoinformatic-Based Prediction of Candidate Epitopes for the Diagnosis and Control of Paratuberculosis (Johne's Disease)

Paratuberculosis is an infectious disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). MAP is an intracellular pathogen with a possible zoonotic potential since it has been successfully isolated from the intestine and blood of Crohn’s disease patients.Since no cure is available, after the detection of the disease, animal culling is the sole applicable containment strategy. However, the difficult detection of the disease in its subclinical form, facilitates its spread raising the need for the development of effective diagnosis and vaccination strategies. The prompt identification and isolation of the infected animals in the subclinical stage would prevent the spread of the infection.In the present study, an immunoinformatic approach has been used to investigate the immunogenic properties of 10 MAP proteins. These proteins were chosen according to a previously published immunoproteomics approach. For each previously-described immunoreactive protein, we predicted the epitopes capable of eliciting an immune response by binding both B-cells and/or class I MHC antigens. The retrieved peptide sequences were analyzed for their specificity and cross-reactivity. The final aim is to employ the discovered peptides sequences as a filtered library useful for early-stage diagnosis and/or to be used in novel multi-subunit or recombinant vaccine formulations.

Genetic Basis of Blood-Based Traits and Their Relationship With Performance and Environment in Beef Cattle at Weaning

The objectives of this study were to explore the usefulness of blood-based traits as indicators of health and performance in beef cattle at weaning and identify the genetic basis underlying the different blood parameters obtained from complete blood counts (CBCs). Disease costs represent one of the main factors determining profitability in animal production. Previous research has observed associations between blood cell counts and an animal’s health status in some species. CBC were recorded from approximately 570 Angus based, crossbred beef calves at weaning born between 2015 and 2016 and raised on toxic or novel tall fescue. The calves (N = ∼600) were genotyped at a density of 50k SNPs and the genotypes (N = 1160) were imputed to a density of 270k SNPs. Genetic parameters were estimated for 15 blood and 4 production. Finally, with the objective of identifying the genetic basis underlying the different blood-based traits, genome-wide association studies (GWAS) were performed for all traits. Heritability estimates ranged from 0.11 to 0.60, and generally weak phenotypic correlations and strong genetic correlations were observed among blood-based traits only. Genome-wide association study identified ninety-one 1-Mb windows that accounted for 0.5% or more of the estimated genetic variance for at least 1 trait with 21 windows overlapping across two or more traits (explaining more than 0.5% of estimated genetic variance for two or more traits). Five candidate genes have been identified in the most interesting overlapping regions related to blood-based traits. Overall, this study represents one of the first efforts represented in scientific literature to identify the genetic basis of blood cell traits in beef cattle. The results presented in this study allow us to conclude that: (1) blood-based traits have weak phenotypic correlations but strong genetic correlations among themselves. (2) Blood-based traits have moderate to high heritability. (3) There is evidence of an important overlap of genetic control among similar blood-based traits which will allow for their use in improvement programs in beef cattle.

Association of BoLA-DRB3.2 alleles with fusobacteriosis in cows

The Major Histocompatability Complex (MHC) determines the immune response to pathogens, and its genes are promising candidates for the search of associations with diseases. A special role is played by BoLA-DRB3 gene, the product of which directly participates in the binding of alien antigens and conditions the specificity of the immune response. The second exon of this gene codes β1-domain of class II antigens, which is necessary for binding a broad spectrum of alien antigens. Exon 2 of BoLA-DRB3 gene is extremely polymorphic, giving the possibility to search the associations of its alleles with various diseases. The article provides the results of the study on polymorphism of alleles of BoLA-DRB3.2 gene for detection of its associations with sensitivity to fusobacteriosis (necrobacteriosis) of cows. The survey was performed using PCR-RFLP method with DNA of blood from 176 cows of two herds of Ukrainian black-and-white dairy breed. As a result of the studies, in the first herd, 25 BoLA-DRB3.2 alleles were found. In the selections of nectobacteriosis susceptible and resistant cows, we found 22 and 21 variants respectively. In the second herd, in the general selection and group of healthy animals, 27 alleles were typed, and 22 in the group of susceptible cows. BoLA-DRB3.2*22 allele was the commonest in both herds in both general selections and groups of nectobacteriosis-resistant cows. In the selection of susceptible animals, the commonest was the variant BoLA-DRB3.2*16. We determined statistically significant associations of BoLA-DRB3.2 alleles with sensitivity to nectobacteriosis of cattle. BoLA-DRB3.2*03 and *22 alleles associate with nectobacteriosis-resistant, while *16 and *23 – with nectobacteriosis-susceptible cows of the both studied groups. Also, in the first herd, another allele was found – *24, indicating close relationship with the disease. The studies of polymorphism of BoLA-DRB3 gene expand the knowledge about genetic peculiarities of the Ukrainian black-and-white dairy breed. The identified molecular-genetic markers could be useful for breeders whose work is oriented towards the formation of herds which are resistant to diseases of the limbs in cattle.

Continuous chromosome-scale haplotypes assembled from a single interspecies F1 hybrid of yak and cattle

BACKGROUND

The development of trio binning as an approach for assembling diploid genomes has enabled the creation of fully haplotype-resolved reference genomes. Unlike other methods of assembly for diploid genomes, this approach is enhanced, rather than hindered, by the heterozygosity of the individual sequenced. To maximize heterozygosity and simultaneously assemble reference genomes for 2 species, we applied trio binning to an interspecies F1 hybrid of yak (Bos grunniens) and cattle (Bos taurus), 2 species that diverged nearly 5 million years ago. The genomes of both of these species are composed of acrocentric autosomes.

RESULTS

We produced the most continuous haplotype-resolved assemblies for a diploid animal yet reported. Both the maternal (yak) and paternal (cattle) assemblies have the largest 2 chromosomes in single haplotigs, and more than one-third of the autosomes similarly lack gaps. The maximum length haplotig produced was 153 Mb without any scaffolding or gap-filling steps and represents the longest haplotig reported for any species. The assemblies are also more complete and accurate than those reported for most other vertebrates, with 97% of mammalian universal single-copy orthologs present.

CONCLUSIONS

The high heterozygosity inherent to interspecies crosses maximizes the effectiveness of the trio binning method. The interspecies trio binning approach we describe is likely to provide the highest-quality assemblies for any pair of species that can interbreed to produce hybrid offspring that develop to sufficient cell numbers for DNA extraction.

RNA-seq differential gene expression analysis in mammary tissue from lactating dairy cows supplemented with sunflower oil

Context Nutrition is the main environmental factor that regulates the composition and secretion of milk fat. For this reason, supplementation of ruminant feed with lipid sources is proposed as a strategy to improve the milk fatty acid profile. However, incorporation of these compounds in milk depends not only on the structure of the diet but also on the efficient capture of nutrients by the mammary tissue and the coordination in the expression and regulation of multiple genes. Aim To evaluate the effect of supplementation with sunflower oil, on gene expression in the mammary gland of Holstein cows under grazing and in the first third of lactation, by using RNA sequencing technology. Methods Six Holstein cows were divided into two groups: a control group, and a group supplemented with 700 g/day of sunflower oil (unsaturated fatty acid) for 25 days. On the last day, a sample of mammary tissue was taken for RNA-seq analysis. Raw data were analysed by using the CLC Genomics Workbench software. Key results Milk protein genes CSN1S1, CSN2, PAEP (LGB), CSN3, CSN1S2 and LALBA were the most abundant in all samples. In the supplemented group, 13 genes were differentially expressed with a false discovery rate &lt;0.15 of which six were upregulated (PRSS2, BEST3, LOC618633, ASB5, NTS and C2CD4B) and seven downregulated (BOLA, DEFB, CLIC6, ATP6V1B1, DCHS2, EYA4 and CYP4B1). These were related to immune-response processes, cell differentiation and membrane transport. Conclusions Supplementation with sunflower oil affects metabolism and other cellular functions in mammary tissue, influencing the expression of genes associated with lipid metabolism, and genes involved in cell–cell interactions, cell morphology, cell death and immune response. Implications These results help to highlight the mechanisms underlying in vivo responses to dietary factors such as supplementation with seed oil in lactating cows. This will serve as a basis for the future development of strategies that improve the fatty acid profile of milk.

Genetic mechanisms regulating the host response during mastitis

Mastitis is a very costly and common disease in the dairy industry. The study of the transcriptome from healthy and mastitic milk somatic cell samples using RNA-Sequencing technology can provide measurements of transcript levels associated with the immune response to the infection. The objective of this study was to characterize the Holstein milk somatic cell transcriptome from 6 cows to determine host response to intramammary infections. RNA-Sequencing was performed on 2 samples from each cow from 2 separate quarters, one classified as healthy (n = 6) and one as mastitic (n = 6). In total, 449 genes were differentially expressed between the healthy and mastitic quarters (false discovery rate <0.05, fold change >±2). Among the differentially expressed genes, the most expressed genes based on reads per kilobase per million mapped reads (RPKM) in the healthy group were associated with milk components (CSN2 and CSN3), and in the mastitic group they were associated with immunity (B2M and CD74). In silico functional analysis was performed using the list of 449 differentially expressed genes, which identified 36 significantly enriched metabolic pathways (false discovery rate <0.01), some of which were associated with the immune system, such as cytokine-cytokine interaction and cell adhesion molecules. Seven functional candidate genes were selected, based on the criteria of being highly differentially expressed between healthy and mastitic groups and significantly enriched in metabolic pathways that are relevant to the inflammatory process (GLYCAM1, B2M, CD74, BoLA-DRA, FCER1G, SDS, and NFKBIA). Last, we identified the differentially expressed genes that are located in quantitative trait locus regions previously known to be associated with mastitis, specifically clinical mastitis, somatic cell count, and somatic cell score. It was concluded that multiple genes within quantitative trait locus regions could potentially affect host response to mastitis-causing agents, making some cows more susceptible to intramammary infections. The identification of potential candidate genes with functional, statistical, biological, and positional relevance associated with host defense to infection will contribute to a better understanding of the underlying genetic architecture associated with mastitis. This in turn will improve the sustainability of agricultural practices by facilitating the selection of cows with improved host defense leading to increased resistance to mastitis.

Polymorphisms in major histocompatibility complex genes and its associations with milk quality in Murrah buffaloes

Animal breeding programs have used molecular genetic tools as an auxiliary method to identify and select animals with superior genetic merit for milk production and milk quality traits as well as disease resistance. Genes of the major histocompatibility complex (MHC) are important molecular markers for disease resistance that could be applied for genetic selection. The aim of this study was to identify single nucleotide polymorphisms (SNPs) and haplotypes in DRB2, DRB3, DMA, and DMB genes in Murrah breed and to analyze the association between molecular markers and milk, fat, protein and mozzarella production, fat and protein percentage, and somatic cell count. Two hundred DNA samples from Murrah buffaloes were used. The target regions of candidate genes were amplified by polymerase chain reaction (PCR) followed by sequencing and identification of polymorphisms. Allele and genotype frequencies, as well as linkage disequilibrium between SNPs, were calculated. Genotypes were used in association analyses with milk production and quality traits. Except for the DMA gene, identified as monomorphic, the other genes presented several polymorphisms. The DMB, DRB2, and DRB3 genes presented two, six, and seven SNPs, respectively. Fifty-seven haplotype blocks were constructed from 15 SNPs identified, which was used in association analyses. All the studied traits had at least one associated haplotype. In conclusion, it is suggested that the haplotypes found herein can be associated with important traits related to milk production and quality.

Molecular characterization of MHC II DRB3 gene of swamp- and riverine-type water buffaloes

Objective

Major histocompatibility complex (MHC) is a set of molecular proteins on the surface of antigen presenting cells encoded by a large gene family which are important parts of the immune system. This study was conducted to convey information on the genetic characteristics of the MHC II DRB3 gene in riverine and swamp buffaloes.

Materials and Methods

Characterization of MHC II DRB3 gene was carried out using polymerase chain reaction (PCR)-based assay. Thirty-milliliter milk samples were collected from 10 swamp-type and 10 riverine-type buffaloes. RNA from milk samples were extracted using Trizol and then followed by reverse transcription-PCR (RT-PCR).

Results

The phylogenetic analysis with 1,000 bootstrap replications clearly showed complex parsimony in MHC II DRB3 gene between 10 riverine- and 10 swamp-type but also confirmed that the samples are similar to Bubalus bubalis. Aligned sequences of the 20 water buffaloes were compared with three other ruminants (Bos taurus, Ovis aries, and Capra hircus) and non-ruminant (Sus scrofa) that serve as an outgroup. MHC sequences from GenBank show that there was an average of 705 identical pairs, with 22 transitional pairs and 30 transversional pairs with a ratio of 0.7.

Conclusion

Based on the molecular data, the current study conforms to other works of literature that this gene is highly polymorphic which can be due to its function in the immune responsiveness and disease resistance. Further study on the immunological response of MHC II DRB3 to infection may elucidate its underlying function and role in the protection against specific disease of animals.

Sequence diversity of major histo-compatibility complex class II DQA1 in Indian Tharparkar cattle: novel alleles and in-silico analysis

Exon 2 of MHC class II gene codes for the first domain of the molecule that forms the peptide-binding groove and its polymorphism partly explains functional MHC diversity. A 850 bp DQA1 gene fragment spanning from intron I to exon III was typed by sequencing of 40 Tharparkar cattle of various agro-climatic zones of northern India along with 10 Tharparkar crossbreds. On analysis of nucleotide sequences, a total of 30 polymorphic sites (1 insertion and 29 SNPs) were identified in 14 MHC alleles leading to amino acid changes in 5 places in 249 bp (exon 2). Five new BoLa DQA1 alleles were identified and reported. The within group mean distance was highest in Tharparkar herd of Bikaner (0.045) and lowest (0.020) in that of Surathgarh (breeding tract) whereas, between groups mean distance was highest in Bikaner Tharparkar-Suratgarh Tharparkar pair. There was excess of nonsynonymous over synonymous nucleotide substitutions in the present study. The effects of these substitutions were predicted using I-Mutant and Panther online resources. The mean ratio of dN/dS was found to be >1.0 at 12 codons with two mutation hotspots at 13th codon (P = 0.002) and 64th codon (P = 0.01). The phylo-geographic analysis revealed that alleles 5, 7 and 13 formed a different cluster with alleles 7 and 13 grouped by the most frequent allele (BoLa-DQA*1401).

Chromosome-level assembly of the water buffalo genome surpasses human and goat genomes in sequence contiguity

Rapid innovation in sequencing technologies and improvement in assembly algorithms have enabled the creation of highly contiguous mammalian genomes. Here we report a chromosome-level assembly of the water buffalo (Bubalus bubalis) genome using single-molecule sequencing and chromatin conformation capture data. PacBio Sequel reads, with a mean length of 11.5 kb, helped to resolve repetitive elements and generate sequence contiguity. All five B. bubalis sub-metacentric chromosomes were correctly scaffolded with centromeres spanned. Although the index animal was partly inbred, 58% of the genome was haplotype-phased by FALCON-Unzip. This new reference genome improves the contig N50 of the previous short-read based buffalo assembly more than a thousand-fold and contains only 383 gaps. It surpasses the human and goat references in sequence contiguity and facilitates the annotation of hard to assemble gene clusters such as the major histocompatibility complex (MHC).

Despite technological advances, chromosome-level assemblies of mammalian genomes are still rare. Here, the authors use PacBio, Chicago and Hi-C approaches to generate a highly contiguous and partially-phased genome assembly for the water buffalo, Bubalus bubalis

Association of bovine major histocompatibility complex (BoLA) gene polymorphism with colostrum and milk microbiota of dairy cows during the first week of lactation

BACKGROUND

The interplay between host genotype and commensal microbiota at different body sites can have important implications for health and disease. In dairy cows, polymorphism of bovine major histocompatibility complex (BoLA) gene has been associated with susceptibility to several infectious diseases, most importantly mastitis. However, mechanisms underlying this association are yet poorly understood. In the present study, we sought to explore the association of BoLA gene polymorphism with the dynamics of mammary microbiota during the first week of lactation.

RESULTS

Colostrum and milk samples were collected from multiparous Holstein dairy cows at the day of calving and days 1 and 6 after calving. Microbiota profiling was performed using high-throughput sequencing of the V1-V2 regions of the bacterial 16S rRNA genes and ITS2 region of the fungal ribosomal DNA. Polymorphism of BoLA genes was determined using PCR-RFLP of exon 2 of the BoLA-DRB3. In general, transition from colostrum to milk resulted in increased species richness and diversity of both bacterial and fungal communities. The most dominant members of intramammary microbiota included Staphylococcus, Ruminococcaceae, and Clostridiales within the bacterial community and Alternaria, Aspergillus, Candida, and Cryptococcus within the fungal community. Comparing the composition of intramammary microbiota between identified BoLA-DRB3.2 variants (n = 2) revealed distinct clustering pattern on day 0, whereas this effect was not significant on the microbiota of milk samples collected on subsequent days. On day 0, proportions of several non-aureus Staphylococcus (NAS) OTUs, including those aligned to Staphylococcus equorum, Staphylococcus gallinarum, Staphylococcus sciuri, and Staphylococcus haemolyticus, were enriched within the microbiota of one of the BoLA-DRB3.2 variants, whereas lactic acid bacteria (LAB) including Lactobacillus and Enterococcus were enriched within the colostrum microbiota of the other variant.

CONCLUSION

Our results suggest a potential role for BoLA-gene polymorphism in modulating the composition of colostrum microbiota in dairy cows. Determining whether BoLA-mediated shifts in the composition of colostrum microbiota are regulated directly by immune system or indirectly by microbiota-derived colonization resistant can have important implications for future development of preventive/therapeutic strategies for controlling mastitis.

Invited review: Microbiota of the bovine udder: Contributing factors and potential implications for udder health and mastitis susceptibility

Various body sites of vertebrates provide stable and nutrient-rich ecosystems for a diverse range of commensal, opportunistic, and pathogenic microorganisms to thrive. The collective genomes of these microbial symbionts (the microbiome) provide host animals with several advantages, including metabolism of indigestible carbohydrates, biosynthesis of vitamins, and modulation of innate and adaptive immune systems. In the context of the bovine udder, however, the relationship between cow and microbes has been traditionally viewed strictly from the perspective of host-pathogen interactions, with intramammary infections by mastitis pathogens triggering inflammatory responses (i.e., mastitis) that are often detrimental to mammary tissues and cow physiology. This traditional view has been challenged by recent metagenomic studies indicating that mammary secretions of clinically healthy quarters can harbor genomic markers of diverse bacterial groups, the vast majority of which have not been associated with mastitis. These observations have given rise to the concept of "commensal mammary microbiota," the ecological properties of which can have important implications for understanding the pathogenesis of mastitis and offer opportunities for development of novel prophylactic or therapeutic products (or both) as alternatives to antimicrobials. Studies conducted to date have suggested that an optimum diversity of mammary microbiota is associated with immune homeostasis, whereas the microbiota of mastitic quarters, or those with a history of mastitis, are considerably less diverse. Whether disruption of the diversity of udder microbiota (dysbiosis) has a role in determining mastitis susceptibility remains unknown. Moreover, little is known about contributions of various biotic and abiotic factors in shaping overall diversity of udder microbiota. This review summarizes current understanding of the microbiota within various niches of the udder and highlights the need to view the microbiota of the teat apex, teat canal, and mammary secretions as interconnected niches of a highly dynamic microbial ecosystem. In addition, host-associated factors, including physiological and anatomical parameters, as well as genetic traits that may affect the udder microbiota are briefly discussed. Finally, current understanding of the effect of antimicrobials on the composition of intramammary microbiota is discussed, highlighting the resilience of udder microbiota to exogenous perturbants.

Detection of quantitative trait loci and putative causal variants affecting somatic cell score in dairy sheep by using a 50K SNP chip and whole-genome sequencing

This study presents a scan of the ovine genome to identify quantitative trait loci (QTL) influencing the somatic cell score (SCS), a classical indicator of subclinical mastitis in sheep, and a subsequent high-resolution analysis of one of the identified QTL regions based on the analysis of whole-genome sequence data sets. A half-sib commercial population of Churra sheep genotyped with a 50K SNP chip was analyzed using linkage analysis (LA) and combined linkage and linkage disequilibrium analysis (LDLA). By LA, 2 5% chromosome-wide significant QTL on OAR5 and OAR25 and one 5% genome-wide significant QTL on ovine chromosome 20 (OAR20) were detected, whereas 22 significant associations were identified by LDLA. Two of the associations detected by LDLA replicated LA-detected effects (OAR20, OAR25). We compared the detected associations with previously reported QTL in sheep and cattle, and functional candidate genes were identified within the estimated confidence intervals. We then performed a high-resolution analysis of the OAR20 QTL region, the most significant QTL region identified by LA that replicated a QTL previously described in Churra sheep for SCS using microsatellite markers. For that, 2 segregating trios of 2 segregating families for the OAR20 QTL (each including the Qq sire and 2 daughters, QQ and qq) were selected for whole-genome sequencing. The bioinformatic analysis of the 6 sequenced samples performed across the genomic interval considered (14.2-41.7 Mb) identified a total of 227,030 variants commonly identified by 2 independent software packages. For the 3 different concordance tests considered, due to discrepancies regarding the QTL peak in the segregating families, the list of mutations concordant with the QTL segregating pattern was processed to identify the variants identified in immune-related genes that show a moderate/high impact on the encoded protein function. Among a list of 85 missense variants concordant with the QTL segregation pattern that were within candidate immune-related genes, 13 variants distributed across 7 genes [PKHD1, NOTCH4, AGER, ENSOARG00000009395 (HLA-C, Homo sapiens), ENSOARG00000015002 (HLA-B, H. sapiens), MOG, and ENSOARG00000018075 (BoLA, Bos taurus, orthologous to human HLA-A] were predicted to cause deleterious effects on protein function. Future studies should assess the possible associations of the candidate variants identified herein in commercial populations with indicator traits of udder inflammation (SCS, clinical mastitis).

Genetic Diversity of Bovine Major Histocompatibility Complex Class II DRB3 locus in cattle breeds from Asia compared to those from Africa and America

Genetic polymorphisms and diversity of BoLA-DRB3.2 are essential because of DRB3 gene's function in innate immunity and its association with infectious diseases resistance or tolerance in cattle. The present study was aimed at assessing the level of genetic diversity of DRB3 in the exon 2 (BoLA-DRB3.2) region in African, American and Asian cattle breeds. Amplification of exon 2 in 174 cattle revealed 15 haplotypes. The breeds with the highest number of haplotypes were Brangus (10), Sokoto Gudali (10) and Dajal (9), while the lowest number of haplotypes were found in Holstein and Sahiwal with 4 haplotypes each. Medium Joining network obtained from haplotypic data showed that all haplotypes condensed around a centric area and each sequence (except in H-3, H-51 and H-106) representing almost a specific haplotype. The BoLA-DRB3.2 sequence analyses revealed a non-significant higher rate of non-synonymous (dN) compared to synonymous substitutions (dS). The ratio of dN/dS substitution across the breeds were observed to be greater than one suggesting that variation at the antigen-binding sites is under positive selection; thus increasing the chances of these breeds to respond to wide array of pathogenic attacks. An analysis of molecular variance revealed that 94.01 and 5.99% of the genetic variation was attributable to differences within and among populations, respectively. Generally, results obtained suggest that within breed genetic variation across breeds is higher than between breeds. This genetic information will be important for investigating the relationship between BoLADRB3.2 and diseases in various cattle breeds studied with attendant implication on designing breeding programs that will aim at selecting individual cattle that carry resistant alleles.