IPD-MHC: nomenclature requirements for the non-human major histocompatibility complex in the next-generation sequencing era

Organisation and evolution of the major histocompatibility complex class I genes in cetaceans

A quarter of marine mammals are at risk of extinction, with disease and poor habitat quality contributing to population decline. Investigation of the Major Histocompatibility Complex (MHC) provides insight into species' capacity to respond to immune and environmental challenges. The eighteen available cetacean chromosome level genomes were used to annotate MHC Class I loci, and to reconstruct the phylogenetic relationship of the described loci. The highest number of loci was observed in the striped dolphin (Stenella coeruleoalba), while the least was observed in the pygmy sperm whale (Kogia breviceps) and rough toothed dolphin (Steno bredanensis). Of the species studied, Mysticetes had the most pseudogenes. Evolutionarily, MHC Class I diverged before the speciation of cetaceans. Yet, locus one was genomically and phylogenetically similar in many species, persisting over evolutionary time. This characterisation of MHC Class I in cetaceans lays the groundwork for future population genetics and MHC expression studies.

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

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

High-Resolution Genotyping of Expressed Equine MHC Reveals a Highly Complex MHC Structure

The Major Histocompatibility Complex (MHC) genes play a key role in a number of biological processes, most notably in immunological responses. The MHCI and MHCII genes incorporate a complex set of highly polymorphic and polygenic series of genes, which, due to the technical limitations of previously available technologies, have only been partially characterized in non-model but economically important species such as the horse. The advent of high-throughput sequencing platforms has provided new opportunities to develop methods to generate high-resolution sequencing data on a large scale and apply them to the analysis of complex gene sets such as the MHC. In this study, we developed and applied a MiSeq-based approach for the combined analysis of the expressed MHCI and MHCII repertoires in cohorts of Thoroughbred, Icelandic, and Norwegian Fjord Horses. The approach enabled us to generate comprehensive MHCI/II data for all of the individuals (n = 168) included in the study, identifying 152 and 117 novel MHCI and MHCII sequences, respectively. There was limited overlap in MHCI and MHCII haplotypes between the Thoroughbred and the Icelandic/Norwegian Fjord horses, showcasing the variation in MHC repertoire between genetically divergent breeds, and it can be inferred that there is much more MHC diversity in the global horse population. This study provided novel insights into the structure of the expressed equine MHC repertoire and highlighted unique features of the MHC in horses.

High functional allelic diversity and copy number in both MHC classes in the common buzzard

BACKGROUND

The major histocompatibility complex (MHC), which encodes molecules that recognize various pathogens and parasites and initiates the adaptive immune response in vertebrates, is renowned for its exceptional polymorphism and is a model of adaptive gene evolution. In birds, the number of MHC genes and sequence diversity varies greatly among taxa, believed due to evolutionary history and differential selection pressures. Earlier characterization studies and recent comparative studies suggest that non-passerine species have relatively few MHC gene copies compared to passerines. Additionally, comparative studies that have looked at partial MHC sequences have speculated that non-passerines have opposite patterns of selection on MHC class I (MHC-I) and class II (MHC-II) loci than passerines: namely, greater sequence diversity and signals of selection on MHC-II than MHC-I. However, new sequencing technology is revealing much greater MHC variation than previously expected while also facilitating full sequence variant detection directly from genomic data. Our study aims to take advantage of high-throughput sequencing methods to fully characterize both classes and domains of MHC of a non-passerine bird of prey, the common buzzard (Buteo buteo), to test predictions of MHC variation and differential selection on MHC classes.

RESULTS

Using genetic, genomic, and transcriptomic high-throughput sequencing data, we established common buzzards have at least three loci that produce functional alleles at both MHC classes. In total, we characterize 91 alleles from 113 common buzzard chicks for MHC-I exon 3 and 41 alleles from 125 chicks for MHC-IIB exon 2. Among these alleles, we found greater sequence polymorphism and stronger diversifying selection at MHC-IIB exon 2 than MHC-I exon 3, suggesting differential selection pressures on MHC classes. However, upon further investigation of the entire peptide-binding groove by including genomic data from MHC-I exon 2 and MHC-IIA exon 2, this turned out to be false. MHC-I exon 2 was as polymorphic as MHC-IIB exon 2 and MHC-IIA exon 2 was essentially invariant. Thus, comparisons between MHC-I and MHC-II that included both domains of the peptide-binding groove showed no differences in polymorphism nor diversifying selection between the classes. Nevertheless, selection analysis indicates balancing selection has been acting on common buzzard MHC and phylogenetic inference revealed that trans-species polymorphism is present between common buzzards and species separated for over 33 million years for class I and class II.

CONCLUSIONS

We characterize and confirm the functionality of unexpectedly high copy number and allelic diversity in both MHC classes of a bird of prey. While balancing selection is acting on both classes, there is no evidence of differential selection pressure on MHC classes in common buzzards and this result may hold more generally once more data for understudied MHC exons becomes available.

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.

Transcriptomic analysis elucidates evolution of the major histocompatibility complex class I in neotropical bats

The Order Chiroptera comprises more than 1,400 species, each with its evolutionary history and under unique selective pressures, among which are the host–pathogen interactions. Bats have coped with complex interactions with a broad spectrum of microbes throughout their evolutionary history, prompting the development of unique adaptations that allow them to co-exist with microbes with pathogenic potential more efficiently than other nonadapted species. In this sense, an extraordinary immune system with unique adaptations has been hypothesized in bats. To explore this, we focused on the major histocompatibility complex (MHC), which plays a crucial role in pathogen recognition and presentation to T cells to trigger the adaptive immune response. We analyzed MHC class I transcripts in five species, each from different families of New World bats. From RNA-seq data, we assembled a partial region of the MHC-I comprising the α1 and α2 domains, which are responsible for peptide binding and recognition. We described five putative functional variants, two of which have two independent insertions at the α2 domain. Our results suggest that this insertion appeared after the divergence of the order Chiroptera and may have an adaptive function in the defense against intracellular pathogens, providing evidence of positive selection and trans-specific polymorphism on the peptide-binding sites.

Intra-specific copy number variation of MHC class II genes in the Siamese fighting fish

Duplicates of genes for major histocompatibility complex (MHC) molecules can be subjected to selection independently and vary markedly in their evolutionary rates, sequence polymorphism, and functional roles. Therefore, without a thorough understanding of their copy number variation (CNV) in the genome, the MHC-dependent fitness consequences within a species could be misinterpreted. Studying the intra-specific CNV of this highly polymorphic gene, however, has long been hindered by the difficulties in assigning alleles to loci and the lack of high-quality genomic data. Here, using the high-quality genome of the Siamese fighting fish (Betta splendens), a model for mate choice studies, and the whole-genome sequencing (WGS) data of 17 Betta species, we achieved locus-specific amplification of their three classical MHC class II genes - DAB1, DAB2, and DAB3. By performing quantitative PCR and depth-of-coverage analysis using the WGS data, we revealed intra-specific CNV at the DAB3 locus. We identified individuals that had two allelic copies (i.e., heterozygous or homozygous) or one allele (i.e., hemizygous) and individuals without this gene. The CNV was due to the deletion of a 20-kb-long genomic region harboring both the DAA3 and DAB3 genes. We further showed that the three DAB genes were under different modes of selection, which also applies to their corresponding DAA genes that share similar pattern of polymorphism. Our study demonstrates a combined approach to study CNV within a species, which is crucial for the understanding of multigene family evolution and the fitness consequences of CNV.

PredMHC: An Effective Predictor of Major Histocompatibility Complex Using Mixed Features

The major histocompatibility complex (MHC) is a large locus on vertebrate DNA that contains a tightly linked set of polymorphic genes encoding cell surface proteins essential for the adaptive immune system. The groups of proteins encoded in the MHC play an important role in the adaptive immune system. Therefore, the accurate identification of the MHC is necessary to understand its role in the adaptive immune system. An effective predictor called PredMHC is established in this study to identify the MHC from protein sequences. Firstly, PredMHC encoded a protein sequence with mixed features including 188D, APAAC, KSCTriad, CKSAAGP, and PAAC. Secondly, three classifiers including SGD, SMO, and random forest were trained on the mixed features of the protein sequence. Finally, the prediction result was obtained by the voting of the three classifiers. The experimental results of the 10-fold cross-validation test in the training dataset showed that PredMHC can obtain 91.69% accuracy. Experimental results on comparison with other features, classifiers, and existing methods showed the effectiveness of PredMHC in predicting the MHC.

Preimplantation Endometrial Transcriptomics in Natural Conception Cycle of the Rhesus Monkey

There is no report on preimplantation phase endometrial transcriptomics in natural conception cycles of primates. In the present study, the whole-genome expression array of endometrium on Days 2, 4, and 6 post-ovulation (pov) in proven natural conception (Group 1; n = 12) and non-mated, ovulatory (Group 2; n = 12) cycles of rhesus monkeys was examined, compared, and validated. Of fifteen (15) genes showing differential expression (>2-fold; pFDR < 0.05), six genes (CHRND, FOXD3, GJD4, MAPK8IP3, MKS1, and NUP50) were upregulated, while eight genes (ADCY5, ADIPOR1, NNMT, PATL1, PIGV, TGFBR2, TOX2, and VWA5B1) were down regulated on Day 6 pov as compared to Day 2 pov in conception cycles. On Day 6 pov, four genes (ADCY5, NNMT, TOX2, and VWA5B1) were down regulated, and AVEN was upregulated in conception cycles compared with the non-conception cycle. These observations were orthogonally validated at protein expression level. Group-specifically expressed unique genes in conception cycles influence the process of induction of immune-tolerance, while the genes expressed in both groups influence processes of protein targeting and metabolism. A triad of timed-actions of progesterone, seminal plasma, and preimplantation embryo putatively regulate several input molecules to CREB, NF-kB, and STAT regulatory networks during secretory phase towards evolution of endometrial receptivity in the rhesus monkey.

Laboratory Codes in Nomenclature and Scientific Communication (Advancing Organism Nomenclature in Scientific Communication to Improve Research Reporting and Reproducibility)

Laboratory registration codes, also known as laboratory codes or lab codes, are a key element in standardized laboratory animal and genetic nomenclature. As such they are critical to accurate scientific communication and to research reproducibility and integrity. The original committee on Mouse Genetic Nomenclature published nomenclature conventions for mice genetics in 1940, and then conventions for inbred strains in 1952. Unique designations were needed, and have been in use since the 1950s, for the sources of animals and substrains, for the laboratories that identified new alleles or mutations, and then for developers of transgenes and induced mutations. Current laboratory codes are typically a 2- to 4-letter acronym for an institution or an investigator. Unique codes are assigned from the International Laboratory Code Registry, which was developed and is maintained by ILAR in the National Academies (National Academies of Sciences Engineering and Medicine and previously National Academy of Sciences). As a resource for the global research community, the registry has been online since 1997. Since 2003 mouse and rat genetic and strain nomenclature rules have been reviewed and updated annually as a joint effort of the International Committee on Standardized Genetic Nomenclature for Mice and the Rat Genome and Nomenclature Committee. The current nomenclature conventions (particularly conventions for non-inbred animals) are applicable beyond rodents, although not widely adopted. Ongoing recognition, since at least the 1930s, of the research relevance of genetic backgrounds and origins of animals, and of spontaneous and induced genetic variants speaks to the need for broader application of standardized nomenclature for animals in research, particularly given the increasing numbers and complexities of genetically modified swine, nonhuman primates, fish, and other species.

Diversity of the BoLA-DRB3 gene in cattle breeds from tropical and subtropical regions of Argentina

Bovine leukocyte antigens (BoLA) have been widely studied because of their primary function in the recognition of pathogens by the immune system. To date, however, the characterization of the BoLA-DRB3 gene in Latin American Zebu and mixed zebuine breeds is scarce. By a sequence-based typing method, here we sequenced exon 2 of BoLA class II DRB3 gene in 264 animals from the five most commonly used breeds in northern Argentina (Creole, Brahman, Braford, Brangus, and Nellore).The Bos taurus, Bos indicus, and mixed breeds analyzed here contained 61 previously reported alleles. Genetic diversity was high at both allelic and nucleotide sequence levels, particularly in the mixed breeds Braford and Brangus. In contrast to previous reports on DRB3 diversity, no evidence of balancing selection was found in our data. Differentiation among breeds was highly significant, as shown by FST (F_ST = 0.052, P < 0.001) and cluster analyses. In accordance with historical origin of the breeds, UPGMA trees and metric multidimensional scaling (MDS) analyses showed that Creole is distantly related to the other zebuine breeds. Among them, Brahman, Braford, and Brangus exhibited the closest affiliations. Despite the overall differentiation of the breeds, analysis of the peptide binding regions at the aminoacid level revealed that the key aminoacids involved in peptide recognition are greatly conserved suggesting little influence of domestication and breeding in functional MHC variability. In sum, this is the first report of BoLA-DRB3 diversity in pure and mixed Bos indicus cattle breeds from Argentina. Knowledge of BoLA-DRB3 variability in breeds adapted to tropical and subtropical environments contributes not only to the characterization of MHC diversity but also to the design of peptide-based vaccines.

Highly-contiguous bovine genomes underpin accurate functional analyses and updated nomenclature of MHC class I

The major histocompatibility complex (MHC) class I region of cattle is both highly polymorphic and, unlike many species, highly variable in gene content between haplotypes. Cattle MHC class I alleles were historically grouped by sequence similarity in the more conserved 3' end of the coding sequence to form phylogenetic allele groups. This has formed the basis of current cattle MHC class I nomenclature. We presently describe and compare five fully assembled MHC class I haplotypes using the latest cattle and yak genome assemblies. Of the five previously described "pseudogenes" in the cattle MHC class I region, Pseudogene 3 is putatively functional in all haplotypes and Pseudogene 6 and Pseudogene 7 are putatively functional in some haplotypes. This was reinforced by evidence of transcription. Based on full gene sequences as well as 3' coding sequence, we identified distinct subgroups of BoLA-3 and BoLA-6 that represent distinct genetic loci. We further examined allele-specific expression using transcriptomic data revealing that certain alleles are consistently weakly expressed compared to others. These observations will help to inform further studies into how MHC class I region variability influences T cell and natural killer cell functions in cattle.

High throughput analysis of MHC-I and MHC-DR diversity of Brazilian cattle populations

The major histocompatibility complex (MHC) contains many genes that play key roles in initiating and regulating immune responses. This includes the polymorphic MHCI and MHCII genes that present epitopes to CD8+ and CD4+ T-cells, respectively. Consequently, the characterisation of the repertoire of MHC genes is an important component of improving our understanding of the genetic variation that determines the outcomes of immune responses. In cattle, MHC (BoLA) research has predominantly focused on Holstein-Friesian animals (as the most economically important breed globally), although the development of high-throughput approaches has allowed the BoLA-DRB3 repertoire to be studied in a greater variety of breeds. In a previous study we reported on the development of a MiSeq-based method to enable high-throughput and high-resolution analysis of bovine MHCI repertoires. Herein, we report on the expansion of this methodology to incorporate analysis of the BoLA-DRB3 and its application to analyse MHC diversity in a large cohort of cattle from Brazil (>500 animals), including representatives from the three major Bos indicus breeds present in Brazil - Guzerat, Gir and Nelore. This large-scale description of paired MHCI-DRB3 repertoires in Bos indicus cattle has identified a small number of novel DRB3 alleles, a large number of novel MHCI alleles and haplotypes, and provided novel insights into MHCI-MHCII association - further expanding our knowledge of bovine MHC diversity.

MHC class I evolution; from Northern pike to salmonids

Background

Salmonids are of major importance both as farmed and wild animals. With the changing environment comes changes in pathogenic pressures so understanding the immune system of all salmonid species is of essence. Major histocompatibility complex (MHC) genes are key players in the adaptive immune system signalling infection to responding T-cells populations. Classical MHC class I (MHCI) genes, defined by high polymorphism, broad expression patterns and peptide binding ability, have a key role in inducing immunity. In salmonids, the fourth whole genome duplication that occurred 94 million years ago has provided salmonids with duplicate MHCI regions, while Northern Pike, a basal sister clade to salmonids, represent a species which has not experienced this whole genome duplication.

Results

Comparing the gene organization and evolution of MHC class I gene sequences in Northern pike versus salmonids displays a complex picture of how many of these genes evolved. Regional salmonid Ia and Ib Z lineage gene duplicates are not orthologs to the Northern pike Z lineage sequences. Instead, salmonids have experienced unique gene duplications in both duplicate regions as well as in the Salmo and Oncorhynchus branch. Species-specific gene duplications are even more pronounced for some L lineage genes.

Conclusions

Although both Northern pike as well as salmonids have expanded their U and Z lineage genes, these gene duplications occurred separately in pike and in salmonids. However, the similarity between these duplications suggest the transposable machinery was present in a common ancestor. The salmonid MHCIa and MHCIb regions were formed during the 94 MYA since the split from pike and before the Oncorhynchus and Salmo branch separated. As seen in tetrapods, the non-classical U lineage genes are diversified duplicates of their classical counterpart. One MHCI lineage, the L lineage, experienced massive species-specific gene duplications after Oncorhynchus and Salmo split approximately 25 MYA. Based on what we currently know about L lineage genes, this large variation in number of L lineage genes also signals a large functional diversity in salmonids.

An Illumina approach to MHC typing of Atlantic salmon

The IPD-MHC Database represents the official repository for non-human major histocompatibility complex (MHC) sequences, overseen and supported by the Comparative MHC Nomenclature Committee, providing access to curated MHC data and associated analysis tools. IPD-MHC gathers allelic MHC class I and class II sequences from classical and non-classical MHC loci from various non-human animals including pets, farmed and experimental model animals. So far, Atlantic salmon and rainbow trout are the only teleost fish species with MHC class I and class II sequences present. For the remaining teleost or ray-finned species, data on alleles originating from given classical locus is scarce hampering their inclusion in the database. However, a fast expansion of sequenced genomes opens for identification of classical loci where high-throughput sequencing (HTS) will enable typing of allelic variants in a variety of new teleost or ray-finned species. HTS also opens for large-scale studies of salmonid MHC diversity challenging the current database nomenclature and analysis tools. Here we establish an Illumina approach to identify allelic MHC diversity in Atlantic salmon, using animals from an endangered wild population, and alter the salmonid MHC nomenclature to accommodate the expected sequence expansions.

The IPD Project: a centralised resource for the study of polymorphism in genes of the immune system

The Immuno Polymorphism Database (IPD), https://www.ebi.ac.uk/ipd/, is a set of specialist databases that enable the study of polymorphic genes which function as part of the vertebrate immune system. The major focus is on the hyperpolymorphic major histocompatibility complex (MHC) genes and the killer-cell immunoglobulin-like receptor (KIR) genes, by providing the official repository and primary source of sequence data. Databases are centred around humans as well as animals important for food security, for companionship and as disease models. The IPD project works with specialist groups or nomenclature committees who provide and manually curate individual sections before they are submitted for online publication. To reflect the recent advance of allele sequencing technologies and the increasing demands of novel tools for the analysis of genomic variation, the IPD project is undergoing a progressive redesign and reorganisation. In this review, recent updates and future developments are discussed, with a focus on the core concepts to better future-proof the project.

Importance of the Major Histocompatibility Complex (Swine Leukocyte Antigen) in Swine Health and Biomedical Research

In pigs, the major histocompatibility complex (MHC), or swine leukocyte antigen (SLA) complex, maps to Sus scrofa chromosome 7. It consists of three regions, the class I and class III regions mapping to 7p1.1 and the class II region mapping to 7q1.1. The swine MHC is divided by the centromere, which is unique among mammals studied to date. The SLA complexspans between 2.4 and 2.7 Mb, depending on haplotype, and encodes approximately 150 loci, with at least 120 genes predicted to be functional. Here we update the whole SLA complex based on the Sscrofa11.1 build and annotate the organization for all recognized SLA genes and their allelic sequences. We present SLA nomenclature and typing methods and discuss the expression of SLA proteins, as well as their role in antigen presentation and immune, disease, and vaccine responses. Finally, we explore the role of SLA genes in transplantation and xenotransplantation and their importance in swine biomedical models.

A potential nomenclature for the Immuno Polymorphism Database (IPD) of chicken MHC genes: progress and problems

Among the genes with the highest allelic polymorphism and sequence diversity are those encoding the classical class I and class II molecules of the major histocompatibility complex (MHC). Although many thousands of MHC sequences have been deposited in general sequence databases like GenBank, the availability of curated MHC sequences with agreed nomenclature has been enormously beneficial. Along with the Immuno Polymorphism Database-IMunoGeneTics/human leukocyte antigen (IPD-IMGT/HLA) database, a collection of databases for curated sequences of immune importance has been developed. A recent addition is an IPD-MHC database for chickens. For many years, the nomenclature system for chicken MHC genes has been based on a list of standard, presumed to be stable, haplotypes. However, these standard haplotypes give different names to identical sequences. Moreover, the discovery of new recombinants between haplotypes and a rapid increase in newly discovered alleles leaves the old system untenable. In this review, a new nomenclature is considered, for which alleles of different loci are given names based on the system used for other MHCs, and then haplotypes are named according to the alleles present. The new nomenclature system is trialled, first with standard haplotypes and then with validated sequences from the scientific literature. In the trial, some class II B sequences were found in both class II loci, presumably by gene conversion or inversion, so that identical sequences would receive different names. This situation prompts further suggestions to the new nomenclature system. In summary, there has been progress, but also problems, with the new IPD-MHC system for chickens.

Nomenclature report 2019: major histocompatibility complex genes and alleles of Great and Small Ape and Old and New World monkey species

The major histocompatibility complex (MHC) is central to the innate and adaptive immune responses of jawed vertebrates. Characteristic of the MHC are high gene density, gene copy number variation, and allelic polymorphism. Because apes and monkeys are the closest living relatives of humans, the MHCs of these non-human primates (NHP) are studied in depth in the context of evolution, biomedicine, and conservation biology. The Immuno Polymorphism Database (IPD)-MHC NHP Database (IPD-MHC NHP), which curates MHC data of great and small apes, as well as Old and New World monkeys, has been upgraded. The curators of the database are responsible for providing official designations for newly discovered alleles. This nomenclature report updates the 2012 report, and summarizes important nomenclature issues and relevant novel features of the IPD-MHC NHP Database.

Identification of the amino acids in the Major Histocompatibility Complex class II region of Scottish Blackface sheep that are associated with resistance to nematode infection

Lambs with the Major Histocompatibility Complex DRB1*1101 allele have been shown to produce fewer nematode eggs following natural and deliberate infection. These sheep also possess fewer adult Teladorsagia circumcincta than sheep with alternative alleles at the DRB1 locus. However, it is unclear if this allele is responsible for the reduced egg counts or merely acts as a marker for a linked gene. This study defined the MHC haplotypes in a population of naturally infected Scottish Blackface sheep by PCR amplification and sequencing, and examined the associations between MHC haplotypes and faecal egg counts by generalised linear mixed modelling. The DRB1*1101 allele occurred predominately on one haplotype and a comparison of haplotypes indicated that the causal mutation or mutations occurred in or around this locus. Additional comparisons with another resistant haplotype indicated that mutations in or around the DQB2*GU191460 allele were also responsible for resistance to nematode infections. Further analyses identified six amino acid substitutions in the antigen binding site of DRB1*1101 that were significantly associated with reductions in the numbers of adult T. circumcincta.

The Marine Mammal Class II Major Histocompatibility Complex Organization

Sirenians share with cetaceans and pinnipeds several convergent traits selected for the aquatic lifestyle. Living in water poses new challenges not only for locomotion and feeding but also for combating new pathogens, which may render the immune system one of the best tools aquatic mammals have for dealing with aquatic microbial threats. So far, only cetaceans have had their class II Major Histocompatibility Complex (MHC) organization characterized, despite the importance of MHC genes for adaptive immune responses. This study aims to characterize the organization of the marine mammal class II MHC using publicly available genomes. We located class II sequences in the genomes of one sirenian, four pinnipeds and eight cetaceans using NCBI-BLAST and reannotated the sequences using local BLAST search with exon and intron libraries. Scaffolds containing class II sequences were compared using dotplot analysis and introns were used for phylogenetic analysis. The manatee class II region shares overall synteny with other mammals, however most DR loci were translocated from the canonical location, past the extended class II region. Detailed analysis of the genomes of closely related taxa revealed that this presumed translocation is shared with all other living afrotherians. Other presumptive chromosome rearrangements in Afrotheria are the deletion of DQ loci in Afrosoricida and deletion of DP in E. telfairi. Pinnipeds share the main features of dog MHC: lack of a functional pair of DPA/DPB genes and inverted DRB locus between DQ and DO subregions. All cetaceans share the Cetartiodactyla inversion separating class II genes into two subregions: class IIa, with DR and DQ genes, and class IIb, with non-classic genes and a DRB pseudogene. These results point to three distinct and unheralded class II MHC structures in marine mammals: one canonical organization but lacking DP genes in pinnipeds; one bearing an inversion separating IIa and IIb subregions lacking DP genes found in cetaceans; and one with a translocation separating the most diverse class II gene from the MHC found in afrotherians and presumptive functional DR, DQ, and DP genes. Future functional research will reveal how these aquatic mammals cope with pathogen pressures with these divergent MHC organizations.

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).

An official nomenclature for the major histocompatibility complex allele sequences from the domestic goat (Capra hircus)

Official allelic nomenclature and corresponding databases of validated major histocompatibility complex (MHC) alleles from most of the major species of farmed livestock are now represented on the IPD-MHC Database. The major exception is the domestic goat (Capra hircus) which can lead to confusion in the research community. Here, we propose to start the process of developing such a resource which will support the research community's interests in livestock population genetics, infectious disease research, vaccine development and comparative studies. In this manuscript, we assign the official nomenclature for the major transcribed and highly polymorphic MHC class II DRB1 locus. Additional class II loci including DRA and DQ and MHC class I loci will be added in the future.

Allelic nomenclature for the duplicated MHC class II DQ genes in sheep

The principal MHC class II molecules involved in the presentation of peptides to the antigen specific receptors on CD4⁺ T cells genes in sheep are derived from DR and DQ genes. Allelic nomenclature systems for the DRB1 and its partner DRA loci are available for Ovid's; however, no official nomenclature is available for the DQ genes which creates ambiguity within the research community. Ovine MHC haplotypes include at least two pairs of DQA and DQB genes, termed DQA1, DQB1 and DQA2, DQB2 and both sets are polymorphic and both seem to be functional. In a number of haplotypes, the DQA1 locus appears to be absent (DQA1-null) and is replaced by a second locus termed DQA2-like. Here, we identify families of alleles based on sequence similarity and phylogenetic clustering which correspond to each of the DQA and DQB genes identified in previous genomic and transcript analyses of homozygous animals. Using such criteria to cluster sequences, we have named 82 full-length and partial cDNA transcripts derived from domestic sheep (Ovis aries) which correspond to alleles at the Ovar-DQA1, DQA2, DQA2-like, DQB1, DQB2 and DQB2-like genes and provide associated sequence resources available to the research community through the IPD-MHC Database. This sets the basis for naming and annotation of DQ genes within the ovine MHC and may be used as a template for DQ genes in other ruminant species which will ultimately support research in livestock infectious disease.

Comparative MHC nomenclature: report from the ISAG/IUIS-VIC committee 2018

Significant progress has been made over the last decade in defining major histocompatibility complex (MHC) diversity at the nucleotide, allele, haplotype, diplotype, and population levels in many non-human species. Much of this progress has been driven by the increased availability and reduced costs associated with nucleotide sequencing technologies. This report provides an update on the activities of the comparative MHC nomenclature committee which is a standing committee of both the International Society for Animal Genetics (ISAG) and the International Union of Immunological Societies (IUIS) where it operates under the umbrella of the Veterinary Immunology Committee (VIC). A previous report from this committee in 2006 defined the role of the committee in providing guidance in the development of a standardized nomenclature for genes and alleles at MHC loci in non-human species. It described the establishment of the Immuno Polymorphism Database, IPD-MHC, which continues to provide public access to high quality MHC sequence data across a range of species. In this report, guidelines for the continued development of a universal MHC nomenclature framework are described, summarizing the continued development of each species section within the IPD-MHC project.