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Vasoya D, Tzelos T, Benedictus L, Karagianni AE, Pirie S, Marr C, Oddsdóttir C, Fintl C, Connelley T. High-Resolution Genotyping of Expressed Equine MHC Reveals a Highly Complex MHC Structure. Genes (Basel) 2023; 14:1422. [PMID: 37510326 PMCID: PMC10379315 DOI: 10.3390/genes14071422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/29/2023] [Accepted: 07/04/2023] [Indexed: 07/30/2023] Open
Abstract
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.
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Affiliation(s)
- Deepali Vasoya
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Roslin EH25 9RG, UK
| | - Thomas Tzelos
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Roslin EH25 9RG, UK
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK
| | - Lindert Benedictus
- Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands
| | - Anna Eleonora Karagianni
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Roslin EH25 9RG, UK
| | - Scott Pirie
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Roslin EH25 9RG, UK
| | - Celia Marr
- Rossdales Equine Hospital, Cotton End Road, Exning, Newmarket CD8 7NN, UK
| | - Charlotta Oddsdóttir
- The Institute for Experimental Pathology at Keldur, University of Iceland Keldnavegur 3, 112 Reykjavík, Iceland
| | - Constanze Fintl
- Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway
| | - Timothy Connelley
- The Roslin Institute, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Roslin EH25 9RG, UK
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Kremling V, Loll B, Pach S, Dahmani I, Weise C, Wolber G, Chiantia S, Wahl MC, Osterrieder N, Azab W. Crystal structures of glycoprotein D of equine alphaherpesviruses reveal potential binding sites to the entry receptor MHC-I. Front Microbiol 2023; 14:1197120. [PMID: 37250020 PMCID: PMC10213783 DOI: 10.3389/fmicb.2023.1197120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 04/18/2023] [Indexed: 05/31/2023] Open
Abstract
Cell entry of most alphaherpesviruses is mediated by the binding of glycoprotein D (gD) to different cell surface receptors. Equine herpesvirus type 1 (EHV-1) and EHV-4 gDs interact with equine major histocompatibility complex I (MHC-I) to initiate entry into equine cells. We have characterized the gD-MHC-I interaction by solving the crystal structures of EHV-1 and EHV-4 gDs (gD1, gD4), performing protein-protein docking simulations, surface plasmon resonance (SPR) analysis, and biological assays. The structures of gD1 and gD4 revealed the existence of a common V-set immunoglobulin-like (IgV-like) core comparable to those of other gD homologs. Molecular modeling yielded plausible binding hypotheses and identified key residues (F213 and D261) that are important for virus binding. Altering the key residues resulted in impaired virus growth in cells, which highlights the important role of these residues in the gD-MHC-I interaction. Taken together, our results add to our understanding of the initial herpesvirus-cell interactions and will contribute to the targeted design of antiviral drugs and vaccine development.
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Affiliation(s)
- Viviane Kremling
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, Berlin, Germany
| | - Bernhard Loll
- Laboratory of Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Szymon Pach
- Institute of Pharmacy (Pharmaceutical Chemistry), Freie Universität Berlin, Berlin, Germany
| | - Ismail Dahmani
- Universität Potsdam, Institut für Biochemie und Biologie, Potsdam, Brandenburg, Germany
| | - Christoph Weise
- BioSupraMol Core Facility, Bio-Mass Spectrometry, Freie Universität Berlin, Berlin, Germany
| | - Gerhard Wolber
- Institute of Pharmacy (Pharmaceutical Chemistry), Freie Universität Berlin, Berlin, Germany
| | - Salvatore Chiantia
- Universität Potsdam, Institut für Biochemie und Biologie, Potsdam, Brandenburg, Germany
| | - Markus C. Wahl
- Laboratory of Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography, Berlin, Germany
| | - Nikolaus Osterrieder
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, Berlin, Germany
- Department of Infectious Diseases and Public Health, City University of Hong Kong, Kowloon, Hong Kong SAR, China
| | - Walid Azab
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, Berlin, Germany
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Obara I, Nijhof A, Atimnedi P, Mijele D, Nanteza A, Elati K, Bishop R. The antigen recognition portion of African buffalo class I MHC is highly polymorphic, consistent with a complex pathogen challenge environment, and the 3' region suggests distinct haplotype configurations. Immunogenetics 2023; 75:115-132. [PMID: 36512055 PMCID: PMC10039833 DOI: 10.1007/s00251-022-01287-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 11/24/2022] [Indexed: 12/15/2022]
Abstract
African buffalo (Syncerus caffer) have been distinct from the Auroch lineage leading to domestic cattle for 5 million years, and are reservoirs of multiple pathogens, that affect introduced domestic cattle. To date, there has been no analysis of the class I MHC locus in African buffalo. We present the first data on African buffalo class I MHC, which demonstrates that gene and predicted protein coding sequences are approximately 86-87% similar to that of African domestic cattle in the peptide binding region. The study also shows concordance in the distribution of codons with elevated posterior probabilities of positive selection in the buffalo class I MHC and known antigen binding sites in cattle. Overall, the diversity in buffalo class I sequences appears greater than that in cattle, perhaps related to a more complex pathogen challenge environment in Africa. However, application of NetMHCpan suggested broad clustering of peptide binding specificities between buffalo and cattle. Furthermore, in the case of at least 20 alleles, critical peptide-binding residues appear to be conserved with those of cattle, including at secondary anchor residues. Alleles with six different length transmembrane regions were detected. This preliminary analysis suggests that like cattle, but unlike most other mammals, African buffalo appears to exhibit configuration (haplotype) variation in which the loci are expressed in distinct combinations.
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Affiliation(s)
- Isaiah Obara
- Freie Universität Berlin, Institute for Parasitology and Tropical Veterinary Medicine, Department of Veterinary Medicine, Berlin, Germany.
- Freie Universität Berlin, Veterinary Centre for Resistance Research, Department of Veterinary Medicine, Berlin, Germany.
| | - Ard Nijhof
- Freie Universität Berlin, Institute for Parasitology and Tropical Veterinary Medicine, Department of Veterinary Medicine, Berlin, Germany
- Freie Universität Berlin, Veterinary Centre for Resistance Research, Department of Veterinary Medicine, Berlin, Germany
| | | | | | - Anne Nanteza
- College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Uganda
| | - Khawla Elati
- Freie Universität Berlin, Institute for Parasitology and Tropical Veterinary Medicine, Department of Veterinary Medicine, Berlin, Germany
- Freie Universität Berlin, Veterinary Centre for Resistance Research, Department of Veterinary Medicine, Berlin, Germany
- Laboratoire de Parasitologie, Institution de La Recherche Et de L'Enseignement Supérieur Agricoles &, Univ. Manouba, École Nationale de Médecine Vétérinaire de Sidi Thabet, Sidi Thabet, Tunisia
| | - Richard Bishop
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
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Azab W, Osterrieder K. Initial Contact: The First Steps in Herpesvirus Entry. ADVANCES IN ANATOMY EMBRYOLOGY AND CELL BIOLOGY 2018; 223:1-27. [PMID: 28528437 DOI: 10.1007/978-3-319-53168-7_1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The entry process of herpesviruses into host cells is complex and highly variable. It involves a sequence of well-orchestrated events that begin with virus attachment to glycan-containing proteinaceous structures on the cell surface. This initial contact tethers virus particles to the cell surface and results in a cascade of molecular interactions, including the tight interaction of viral envelope glycoproteins to specific cell receptors. These interactions trigger intracellular signaling and finally virus penetration after fusion of the viral envelope with cellular membranes. Based on the engaged cellular receptors and co-receptors, and the subsequent signaling cascades, the entry pathway will be decided on the spot. A number of viral glycoproteins and many cellular receptors and molecules have been identified as players in one or several of these events during virus entry. This chapter will review viral glycoproteins, cellular receptors and signaling cascades associated with the very first interactions of herpesviruses with their target cells.
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Affiliation(s)
- Walid Azab
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, Robert-von-Ostertag-Str. 7-13, 14163, Berlin, Germany.
| | - Klaus Osterrieder
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, Robert-von-Ostertag-Str. 7-13, 14163, Berlin, Germany
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Siva Subramaniam N, Morgan EF, Wetherall JD, Stear MJ, Groth DM. A comprehensive mapping of the structure and gene organisation in the sheep MHC class I region. BMC Genomics 2015; 16:810. [PMID: 26480943 PMCID: PMC4613773 DOI: 10.1186/s12864-015-1992-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 10/06/2015] [Indexed: 11/13/2022] Open
Abstract
Background The major histocompatibility complex (MHC) is a chromosomal region that regulates immune responsiveness in vertebrates. This region is one of the most important for disease resistance because it has been associated with resistance or susceptibility to a wide variety of diseases and because the MHC often accounts for more of the variance than other loci. Selective breeding for disease resistance is becoming increasingly common in livestock industries, and it is important to determine how this will influence MHC polymorphism and resistance to diseases that are not targeted for selection. However, in sheep the order and sequence of the protein coding genes is controversial. Yet this information is needed to determine precisely how the MHC influences resistance and susceptibility to disease. Methods CHORI bacterial artificial chromosomes (BACs) known to contain sequences from the sheep MHC class I region were sub-cloned, and the clones partially sequenced. The resulting sequences were analysed and re-assembled to identify gene content and organisation within each BAC. The low resolution MHC class I physical map was then compared to the cattle reference genome, the Chinese Merino sheep MHC map published by Gao, et al. (2010) and the recently available sheep reference genome. Results Immune related class I genes are clustered into 3 blocks; beta, kappa and a novel block not previously identified in other organisms. The revised map is more similar to Bovidae maps than the previous sheep maps and also includes several genes previously not annotated in the Chinese Merino BAC assembly and others not currently annotated in the sheep reference chromosome 20. In particular, the organisation of nonclassical MHC class I genes is similar to that present in the cattle MHC. Sequence analysis and prediction of amino acid sequences of MHC class I classical and nonclassical genes was performed and it was observed that the map contained one classical and eight nonclassical genes together with three possible pseudogenes. Conclusions The comprehensive physical map of the sheep MHC class I region enhances our understanding of the genetic architecture of the class I MHC region in sheep and will facilitate future studies of MHC function. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1992-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- N Siva Subramaniam
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, GPO Box U1987, Perth, 6845, WA, Australia.
| | - E F Morgan
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, GPO Box U1987, Perth, 6845, WA, Australia.
| | - J D Wetherall
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, GPO Box U1987, Perth, 6845, WA, Australia.
| | - M J Stear
- Department of Animal Production and Public Health, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, UK. .,Institute of Biodiversity, Animal Health and Comparative Medicine, Garscube Estate, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, UK.
| | - D M Groth
- School of Biomedical Sciences, CHIRI Biosciences Research Precinct, Faculty of Health Sciences, Curtin University, GPO Box U1987, Perth, 6845, WA, Australia.
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Azab W, Harman R, Miller D, Tallmadge R, Frampton AR, Antczak DF, Osterrieder N. Equid herpesvirus type 4 uses a restricted set of equine major histocompatibility complex class I proteins as entry receptors. J Gen Virol 2014; 95:1554-1563. [PMID: 24722677 DOI: 10.1099/vir.0.066407-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Equid herpesvirus type 1 (EHV-1) was shown to use an unusual receptor for cellular entry - MHC-I molecules. Here, we demonstrated that the closely related EHV, EHV-4, also uses this strategy for cellular invasion, both in equine cells in culture and in the heterologous, non-permissive murine mastocytoma cell line (P815) after stable transfection with horse MHC-I genes. Using a panel of P815 cell lines transfected with individual horse MHC-I genes, we provided support for the hypothesis that EHV-1 and EHV-4 target classical polymorphic MHC-I molecules as viral entry receptors. All known equine MHC-I molecules from the two principal classical polymorphic loci specify alanine at position 173 (A173), whilst other MHC-I loci encoded different amino acids at this position and did not permit viral entry. Site-directed mutagenesis of position 173 diminished or enhanced viral entry, depending upon the initial amino acid. However, there were other, as yet undefined, constraints to this process: MHC-I genes from two non-classical loci carried A173 but did not enable viral entry in P815 transfectants. Our study suggested that the capacity to bind MHC-I molecules arose in the common ancestor of EHV-1 and EHV-4. The widespread occurrence of A173 in classical polymorphic horse MHC-I molecules indicated that horses of most MHC haplotypes should be susceptible to infection via this entry portal.
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Affiliation(s)
- Walid Azab
- Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.,Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, 14163 Berlin, Germany
| | - Rebecca Harman
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Donald Miller
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Rebecca Tallmadge
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Arthur R Frampton
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403, USA
| | - Douglas F Antczak
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Nikolaus Osterrieder
- Institut für Virologie, Robert von Ostertag-Haus, Zentrum für Infektionsmedizin, Freie Universität Berlin, 14163 Berlin, Germany
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Brinkmeyer-Langford CL, Murphy WJ, Childers CP, Skow LC. A conserved segmental duplication within ELA. Anim Genet 2010; 41 Suppl 2:186-95. [DOI: 10.1111/j.1365-2052.2010.02137.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Development of a DNA microarray for detection of expressed equine classical MHC class I sequences in a defined population. Immunogenetics 2010; 62:633-9. [PMID: 20683590 DOI: 10.1007/s00251-010-0463-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 06/28/2010] [Indexed: 10/19/2022]
Abstract
Development of an accurate and efficient molecular-based equine MHC class I typing method would facilitate the study of T lymphocyte immune responses in horses. Here, a DNA microarray was designed to detect expressed classical MHC class I genes comprising serologically defined equine leukocyte antigen (ELA)-A haplotypes represented in a closed Arabian horse breeding herd. Initially, cloning and sequencing of RT-PCR products were used to identify sequences associated with the ELA-A1, A4, and W11 haplotypes, and one undefined haplotype, in six horses. Subsequently, sequence-specific, conserved (positive control), and random nucleotide (negative control) 23- to 27-mer oligonucleotide microarray probes were designed and spotted onto an epoxy-coated masked slide using a robotic arrayer. Bulk RT-PCR products from each horse were biotinylated by nick translation, hybridized to the array, and detected using tyramide signal amplification. The microarray consistently detected eight of nine classical MHC class I transcripts and allowed ELA haplotypic associations to be made. Cloning and sequencing of RT-PCR products were then performed in a group of ELA disparate horses and ponies, in which six novel sequences were identified. This group was used to determine the specificity of the array. Overall, the microarray was more efficient than cloning and sequencing for detecting expressed classical MHC class I sequences in this defined population of horses, and was significantly more specific than serology. These results confirmed the utility of a microarray-based method for high-resolution MHC class I typing in the horse. With additional probes the array could be useful in a broader population.
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Equus caballus major histocompatibility complex class I is an entry receptor for equine herpesvirus type 1. J Virol 2010; 84:9027-34. [PMID: 20610718 DOI: 10.1128/jvi.00287-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In this study, Equus caballus major histocompatibility complex class I (MHC-I) was identified as a cellular entry receptor for the alphaherpesvirus equine herpesvirus type 1 (EHV-1). This novel EHV-1 receptor was discovered using a cDNA library from equine macrophages. cDNAs from this EHV-1-susceptible cell type were inserted into EHV-1-resistant B78H1 murine melanoma cells, these cells were infected with an EHV-1 lacZ reporter virus, and cells that supported virus infection were identified by X-Gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside) staining. Positive cells were subjected to several rounds of purification to obtain homogeneous cell populations that were shown to be uniformly infected with EHV-1. cDNAs from these cell populations were amplified by PCR and then sequenced. The sequence data revealed that the EHV-1-susceptible cells had acquired an E. caballus MHC-I cDNA. Cell surface expression of this receptor was verified by confocal immunofluorescence microscopy. The MHC-I cDNA was cloned into a mammalian expression vector, and stable B78H1 cell lines were generated that express this receptor. These cell lines were susceptible to EHV-1 infection while the parental B78H1 cells remained resistant to infection. In addition, EHV-1 infection of the B78H1 MHC-I-expressing cell lines was inhibited in a dose-dependent manner by an anti-MHC-I antibody.
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Noronha LE, Antczak DF. Maternal immune responses to trophoblast: the contribution of the horse to pregnancy immunology. Am J Reprod Immunol 2010; 64:231-44. [PMID: 20618178 DOI: 10.1111/j.1600-0897.2010.00895.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The horse has proven to be a distinctively informative species in the study of pregnancy immunology for several reasons. First, unique aspects of the anatomy and physiology of the equine conceptus facilitate approaches that are not possible in other model organisms, such as non-surgical recovery of early stage embryos and conceptuses and isolation of pure trophoblast cell populations. Second, pregnant mares make strong cytotoxic antibody responses to paternal major histocompatibility complex class I antigens expressed by the chorionic girdle cells, permitting detailed evaluation of the antigenicity of these invasive trophoblasts and how they affect the maternal immune system. Third, there is abundant evidence for local maternal cellular immune responses to the invading trophoblasts in the pregnant mare. The survival of the equine fetus in the face of strong maternal immune responses highlights the complex immunoregulatory mechanisms that result in materno-fetal tolerance. Finally, the parallels between human and horse trophoblast cell types, their gene expression, and function make the study of equine pregnancy highly relevant to human health. Here, we review the most pertinent aspects of equine reproductive immunology and how studies of the pregnant mare have contributed to our understanding of maternal acceptance of the allogeneic fetus.
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Affiliation(s)
- Leela E Noronha
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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Tallmadge RL, Campbell JA, Miller DC, Antczak DF. Analysis of MHC class I genes across horse MHC haplotypes. Immunogenetics 2010; 62:159-72. [PMID: 20099063 DOI: 10.1007/s00251-009-0420-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Accepted: 12/12/2009] [Indexed: 11/28/2022]
Abstract
The genomic sequences of 15 horse major histocompatibility complex (MHC) class I genes and a collection of MHC class I homozygous horses of five different haplotypes were used to investigate the genomic structure and polymorphism of the equine MHC. A combination of conserved and locus-specific primers was used to amplify horse MHC class I genes with classical and nonclassical characteristics. Multiple clones from each haplotype identified three to five classical sequences per homozygous animal and two to three nonclassical sequences. Phylogenetic analysis was applied to these sequences, and groups were identified which appear to be allelic series, but some sequences were left ungrouped. Sequences determined from MHC class I heterozygous horses and previously described MHC class I sequences were then added, representing a total of ten horse MHC haplotypes. These results were consistent with those obtained from the MHC homozygous horses alone, and 30 classical sequences were assigned to four previously confirmed loci and three new provisional loci. The nonclassical genes had few alleles and the classical genes had higher levels of allelic polymorphism. Alleles for two classical loci with the expected pattern of polymorphism were found in the majority of haplotypes tested, but alleles at two other commonly detected loci had more variation outside of the hypervariable region than within. Our data indicate that the equine major histocompatibility complex is characterized by variation in the complement of class I genes expressed in different haplotypes in addition to the expected allelic polymorphism within loci.
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Affiliation(s)
- Rebecca L Tallmadge
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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Marchetti B, Gault EA, Cortese MS, Yuan Z, Ellis SA, Nasir L, Campo MS. Bovine papillomavirus type 1 oncoprotein E5 inhibits equine MHC class I and interacts with equine MHC I heavy chain. J Gen Virol 2009; 90:2865-2870. [DOI: 10.1099/vir.0.014746-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Bovine papillomavirus type 1 is one of the aetiological agents of equine sarcoids. The viral major oncoprotein E5 is expressed in virtually all sarcoids, sarcoid cell lines and in vitro-transformed equine fibroblasts. To ascertain whether E5 behaves in equine cells as it does in bovine cells, we introduced the E5 open reading frame into fetal equine fibroblasts (EqPalF). As observed in primary bovine fibroblasts (BoPalF), E5 by itself could not immortalize EqPalF and an immortalizing gene, such as human telomerase (hTERT/hT), was required for the cells to survive selection. The EqPalF-hT-1E5 cells were morphologically transformed, elongated with many pseudopodia and capable of forming foci. Equine major histocompatibility complex class I (MHC I) was inhibited in these cells at least at two levels: transcription of MHC I heavy chain was inhibited and the MHC I complex was retained in the Golgi apparatus and prevented from reaching the cell surface. We conclude that, as in bovine cells and tumours, E5 is a player in the transformation of equine cells and the induction of sarcoids, and a potential major cause of MHC I downregulation and hence poor immune clearance of tumour cells.
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Affiliation(s)
- Barbara Marchetti
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
| | - Elisabeth A. Gault
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
| | - Marc S. Cortese
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
| | - ZhengQiang Yuan
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
| | | | - Lubna Nasir
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
| | - M. Saveria Campo
- Institute of Comparative Medicine, University of Glasgow, Glasgow G61 1QH, Scotland, UK
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Vaccination of ponies with the IE gene of EHV-1 in a recombinant modified live vaccinia vector protects against clinical and virological disease. Vet Immunol Immunopathol 2009; 135:108-117. [PMID: 20018383 DOI: 10.1016/j.vetimm.2009.11.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2009] [Revised: 11/10/2009] [Accepted: 11/14/2009] [Indexed: 12/28/2022]
Abstract
The control of EHV-1 infection by cytotoxic T-cell responses (CTL) via a reduction in cell associated viremia remains an important goal in horses. Unfortunately, current vaccines are inefficient at inducing these responses. We have identified the immediate early (IE) gene of EHV-1 as a potent stimulator of virus-specific CTL responses in ponies expressing a specific MHC class I serological haplotype (A3/B2). This study was designed to determine if vaccination of A3/B2 MHC I positive ponies with the IE gene could induce protection and immune responses associated with cell mediated immunity. Ponies expressing the MHC-I A3/B2 haplotype (A3/B2 vaccinates) and ponies with a different MHC I haplotype (either non-A3 vaccinates or A3-non-B2 vaccinates) were vaccinated with a recombinant modified vaccinia Ankara (rMVA) vector expressing the IE gene on 3 occasions and vaccinates and unvaccinated controls were challenge infected 8 weeks after the last vaccination. Interferon gamma (IFN-gamma) mRNA and antibody titers were determined throughout the study and clinical signs, nasal virus shedding and viremia were determined following challenge infection. Vaccination of A3/B2 vaccinates conferred significant clinical protection and a significant reduction in EHV-1 viremia. IFN-gamma mRNA increased significantly following vaccination in the A3/B2 vaccinates. Antibody titers remained low until after challenge infection, indicating that no accidental field acquired or recrudescent EHV-1 infection had occurred. In summary, this is an important study showing that vaccination of ponies with the EHV-1 IE protein provides not only reduction in clinical disease but also reduction of cell associated viremia, which is a prerequisite for the prevention of abortion and neurological disease.
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McGuire TC, Fraser DG, Mealey RH. Cytotoxic T lymphocytes in protection against equine infectious anemia virus. Anim Health Res Rev 2007; 5:271-6. [PMID: 15984338 DOI: 10.1079/ahr200482] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
AbstractCytotoxic T lymphocytes (CTL) are associated with virus control in horses infected with equine infectious anemia virus (EIAV). Early in infection, control of the initial viremia coincides with the appearance of CTL and occurs before the appearance of neutralizing antibody. In carrier horses, treatment with immunosuppressive drugs results in viremia before a change in serum neutralizing antibody occurs. Clearance of initial viremia caused by other lentiviruses, including human immunodeficiency virus-1 and simian immunodeficiency virus, is also associated with CTL and not neutralizing antibody. In addition, depletion of CD8+cells prior to infection of rhesus monkeys with simian immunodeficiency prevents clearance of virus and the same treatment of persistently infected monkeys results in viremia. Cats given adoptive transfers of lymphocytes from vaccinated cats were protected and the protection was MHC-restricted, occurred in the absence of antiviral humoral immunity, and correlated with the transfer of cells with feline immunodeficiency virus-specific CTL and T-helper lymphocyte activities. Therefore, a lentiviral vaccine, including one for EIAV, needs to induce CTL. Based on initial failures to induce CTL to EIAV proteins by any means other than infection, we attempted to define an experimental system for the evaluation of methods for CTL induction. CTL epitopes restricted by the ELA-A1 haplotype were identified and the MHC class I molecule presenting these peptides was identified. This was done by expressing individual MHC class I molecules from cDNA clones in target cells. The target cells were then pulsed with peptides and used with effector CTL stimulated with the same peptides. In a preliminary experiment, immunization of three ELA-A1 haplotype horses with an Env peptide restricted by this haplotype resulted in CTL in peripheral blood mononuclear cells (PBMC) which recognized the Env peptide and virus-infected cells, but the CTL response was transient. Nevertheless there was significant protection against clinical disease following EIAV challenge of these immunized horses when compared with three control horses given the same virus challenge. These data indicated that responses to peptides in immunized horses needed to be enhanced. Optimal CTL responses require help from CD4+T lymphocytes, and experiments were done to identify EIAV peptides which stimulated CD4+T lymphocytes in PBMC from infected horses with different MHC class II types. Two broadly cross-reactive Gag peptides were identified which stimulated only an interferon γ response by CD4+T lymphocytes, which indicated a T helper 1 response is needed for CTL stimulation. Such peptides should facilitate CTL responses; however, other problems in inducing protection against lentiviruses remain, the most significant of them being EIAV variants that can escape both CTL and neutralizing antibody. A possible solution to CTL escape variants is the induction of high-avidity CTL to multiple EIAV epitopes.
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Affiliation(s)
- Travis C McGuire
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA.
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15
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Mealey RH, Lee JH, Leib SR, Littke MH, McGuire TC. A single amino acid difference within the alpha-2 domain of two naturally occurring equine MHC class I molecules alters the recognition of Gag and Rev epitopes by equine infectious anemia virus-specific CTL. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2006; 177:7377-90. [PMID: 17082657 PMCID: PMC3342702 DOI: 10.4049/jimmunol.177.10.7377] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Although CTL are critical for control of lentiviruses, including equine infectious anemia virus, relatively little is known regarding the MHC class I molecules that present important epitopes to equine infectious anemia virus-specific CTL. The equine class I molecule 7-6 is associated with the equine leukocyte Ag (ELA)-A1 haplotype and presents the Env-RW12 and Gag-GW12 CTL epitopes. Some ELA-A1 target cells present both epitopes, whereas others are not recognized by Gag-GW12-specific CTL, suggesting that the ELA-A1 haplotype comprises functionally distinct alleles. The Rev-QW11 CTL epitope is also ELA-A1-restricted, but the molecule that presents Rev-QW11 is unknown. To determine whether functionally distinct class I molecules present ELA-A1-restricted CTL epitopes, we sequenced and expressed MHC class I genes from three ELA-A1 horses. Two horses had the 7-6 allele, which when expressed, presented Env-RW12, Gag-GW12, and Rev-QW11 to CTL. The other horse had a distinct allele, designated 141, encoding a molecule that differed from 7-6 by a single amino acid within the alpha-2 domain. This substitution did not affect recognition of Env-RW12, but resulted in more efficient recognition of Rev-QW11. Significantly, CTL recognition of Gag-GW12 was abrogated, despite Gag-GW12 binding to 141. Molecular modeling suggested that conformational changes in the 141/Gag-GW12 complex led to a loss of TCR recognition. These results confirmed that the ELA-A1 haplotype is comprised of functionally distinct alleles, and demonstrated for the first time that naturally occurring MHC class I molecules that vary by only a single amino acid can result in significantly different patterns of epitope recognition by lentivirus-specific CTL.
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MESH Headings
- Alleles
- Amino Acid Sequence
- Amino Acid Substitution/immunology
- Animals
- Antigen Presentation/immunology
- Computer Simulation
- Crystallography, X-Ray
- Cytotoxicity Tests, Immunologic
- Epitopes, T-Lymphocyte/chemistry
- Epitopes, T-Lymphocyte/immunology
- Epitopes, T-Lymphocyte/metabolism
- Female
- Gene Products, gag/chemistry
- Gene Products, gag/immunology
- Gene Products, gag/metabolism
- Gene Products, rev/chemistry
- Gene Products, rev/immunology
- Gene Products, rev/metabolism
- Histocompatibility Antigens Class I/chemistry
- Histocompatibility Antigens Class I/immunology
- Histocompatibility Antigens Class I/metabolism
- Horses
- Infectious Anemia Virus, Equine/chemistry
- Infectious Anemia Virus, Equine/immunology
- Male
- Molecular Sequence Data
- Protein Binding/immunology
- Protein Structure, Tertiary
- T-Lymphocytes, Cytotoxic/immunology
- T-Lymphocytes, Cytotoxic/metabolism
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Affiliation(s)
- Robert H Mealey
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164, USA.
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16
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Kydd JH, Davis-Poynter NJ, Birch J, Hannant D, Minke J, Audonnet JC, Antczak DF, Ellis SA. A molecular approach to the identification of cytotoxic T-lymphocyte epitopes within equine herpesvirus 1. J Gen Virol 2006; 87:2507-2515. [PMID: 16894188 DOI: 10.1099/vir.0.82070-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Equine herpesvirus 1 (EHV-1) causes respiratory and neurological disease and abortion in horses. Animals with high frequencies of cytotoxic T lymphocytes (CTL) show reduced severity of respiratory disease and frequency of abortion, probably by CTL-mediated control of cell-associated viraemia. This study aimed to identify CTL epitopes restricted by selected major histocompatibility complex (MHC) class I alleles expressed in the equine leukocyte antigen (ELA) A3 haplotype. Effector CTL were induced from EHV-1-primed ponies and thoroughbreds with characterized MHC class I haplotypes and screened against P815 target cells transfected with selected EHV-1 genes and MHC class I genes. Targets that expressed EHV-1 gene 64 and the MHC B2 gene were lysed by effector CTL in a genetically restricted manner. There was no T-cell recognition of targets expressing either the MHC B2 gene and EHV-1 genes 2, 12, 14, 16, 35, 63 or 69, or the MHC C1 gene and EHV-1 genes 12, 14, 16 or 64. A vaccinia virus vector encoding gene 64 (NYVAC-64) was also investigated. Using lymphocytes from ELA-A3 horses, the recombinant NYVAC-64 virus induced effector CTL that lysed EHV-1-infected target cells; the recombinant virus also supplied a functional peptide that was expressed by target cells and recognized in an MHC-restricted fashion by CTL induced with EHV-1. This construct may therefore be used to determine the antigenicity of EHV-1 gene 64 for other MHC haplotypes. These techniques are broadly applicable to the identification of additional CTL target proteins and their presenting MHC alleles, not only for EHV-1, but for other equine viruses.
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Affiliation(s)
- Julia H Kydd
- Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK
| | - N J Davis-Poynter
- Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK
| | - J Birch
- Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
| | - D Hannant
- Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK
| | - J Minke
- Merial SAS, 254 rue Marcel Mérieux, 69007 Lyon, France
| | - J-C Audonnet
- Merial SAS, 254 rue Marcel Mérieux, 69007 Lyon, France
| | - D F Antczak
- James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Shirley A Ellis
- Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
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17
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Tallmadge RL, Lear TL, Antczak DF. Genomic characterization of MHC class I genes of the horse. Immunogenetics 2005; 57:763-74. [PMID: 16220348 DOI: 10.1007/s00251-005-0034-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Accepted: 07/25/2005] [Indexed: 10/25/2022]
Abstract
The availability of a contig of bacterial artificial chromosome (BAC) clones spanning the equine major histocompatibility complex (MHC) made possible a detailed analysis of horse MHC class I genes. Prior to this study, only a single horse MHC class I gene had been sequenced at the genomic level. Although many ( approximately 60) MHC class I cDNA sequences had been determined and published, from this information, it was not possible to determine how many class I loci are expressed in horses or to assign individual sequences to allelic series. In this study, 15 MHC class I genes were identified in BAC subclones and fully sequenced. Because the BAC library donor horse had been bred for homozygosity at the MHC, these 15 genomic clones represent distinct MHC class I genes and pseudogenes and not alleles at a smaller number of loci. For five of the genes, cDNA sequences from these loci had previously been identified. Two additional expressed class I genes were discovered, bringing the known total of different equine MHC class I genes (loci) expressed as mRNA to seven. Expression of all seven loci was detected by reverse transcriptase-polymerase chain reaction in adult, fetal, and placental tissues. The remaining eight genes were designated as pseudogenes. This work resulted in moderate expansion of the horse MHC BAC contig length, and the remaining gap was shortened. The information contained in these equine MHC class I sequences will permit comparison of MHC class I genes expressed across different horse MHC haplotypes and between horses and other mammalian species.
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Affiliation(s)
- Rebecca L Tallmadge
- James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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18
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Miltiadou D, Ballingall KT, Ellis SA, Russell GC, McKeever DJ. Haplotype characterization of transcribed ovine major histocompatibility complex (MHC) class I genes. Immunogenetics 2005; 57:499-509. [PMID: 16028041 DOI: 10.1007/s00251-005-0008-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Accepted: 05/23/2005] [Indexed: 10/25/2022]
Abstract
The ovine major histocompatibility complex (MHC) remains poorly characterized compared with those of other livestock species. Molecular genetic analysis of the bovine MHC has revealed considerable haplotype and allelic diversity that earlier serological analysis had not detected. To develop cellular and molecular tools to support development of vaccines against intracellular pathogens of sheep, we have undertaken a molecular genetic analysis of four distinct ovine MHC haplotypes carried by two heterozygous Blackface rams. We have identified 12 novel class I transcripts and used a class I sequence-specific genotyping system to assign each of these transcripts to individual haplotypes. Using a combination of phylogenetic analysis, haplotype and transcript expression data, we identified at least four distinct polymorphic class I MHC loci, three of which appear together in a number of combinations in individual haplotypes. The haplotypes were further characterized at the highly polymorphic Ovar-DRB1 locus, allowing selection of the progeny of the two founder rams for the establishment of an MHC-defined resource population.
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Affiliation(s)
- Despoina Miltiadou
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK
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19
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Chung C, Mealey RH, McGuire TC. CTL from EIAV carrier horses with diverse MHC class I alleles recognize epitope clusters in Gag matrix and capsid proteins. Virology 2004; 327:144-54. [PMID: 15327905 PMCID: PMC3342308 DOI: 10.1016/j.virol.2004.06.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 06/11/2004] [Accepted: 06/23/2004] [Indexed: 11/29/2022]
Abstract
Cytotoxic T lymphocytes (CTL) are important for controlling equine infectious anemia virus (EIAV). Because Gag matrix (MA) and capsid (CA) are the most frequently recognized proteins, the hypothesis that CTL from EIAV-infected horses with diverse MHC class I alleles recognize epitope clusters (EC) in these proteins was tested. Four EC were identified by CTL from 15 horses and 8 of these horses had diverse MHC class I alleles. Two of the eight had CTL to EC1, six to EC2, five to EC3, and four to EC4. Because EC2-4 were recognized by CTL from >50% of horses with diverse alleles, the hypothesis was accepted. EC1 and EC3 were the most conserved EC and these more conserved broadly recognized EC may be most useful for CTL induction, helping overcome MHC class I polymorphism and antigenic variation.
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Affiliation(s)
| | | | - Travis C. McGuire
- Corresponding author. Department of Veterinary Microbiology and Pathology, Washington State University, PO Box 647040, Pullman, WA 99165-7040. Fax: +1 509 335 8529. (T.C. McGuire)
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20
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Chung C, Leib SR, Fraser DG, Ellis SA, McGuire TC. Novel classical MHC class I alleles identified in horses by sequencing clones of reverse transcription-PCR products. ACTA ACUST UNITED AC 2004; 30:387-96. [PMID: 14675391 DOI: 10.1111/j.1365-2370.2003.00420.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Improved typing of horse classical MHC class I is required to more accurately define these molecules and to extend the number identified further than current serological assays. Defining classical MHC class I alleleic polymorphism is important in evaluating cytotoxic T lymphocyte (CTL) responses in horses. In this study, horse classical MHC class I genes were analyzed based on reverse transcription (RT)-PCR amplification of sequences encoding the polymorphic peptide binding region and the more conserved alpha 3, transmembrane and cytoplasmic regions followed by cloning and sequencing. Primer sets included a horse classical MHC class I-specific reverse primer and a forward primer conserved in all known horse MHC class I genes. Sequencing at least 25 clones containing MHC class I sequences from each of 13 horses identified 25 novel sequences and three others which had been described. Of these, nine alleles were identified from different horses or different RT-PCR and 19 putative alleles were identified in multiple clones from the same RT-PCR. The primer pairs did not amplify putative non-classical MHC class I genes as only classical MHC class I and related pseudogenes were found in 462 clones. This method also identified classical MHC class I alleles shared between horses by descent, and defined differences in alleles between horses varying in equine leukocyte antigen (ELA)-A haplotype as determined by serology. However, horses sharing ELA-A haplotypes defined by serotyping did not always share cDNA sequences, suggesting subhaplotypic variations within serologically defined ELA-A haplotypes. The 13 horses in this study had two to five classical MHC class I sequences, indicating that multiple loci code for these genes. Sequencing clones from RT-PCR with classical MHC class I-specific primers should be useful for selection of haplotype matched and mismatched horses for CTL studies, and provides sequence information needed to develop easier and more discriminating typing procedures.
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Affiliation(s)
- C Chung
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99165-7040, USA.
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21
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Mealey RH, Zhang B, Leib SR, Littke MH, McGuire TC. Epitope specificity is critical for high and moderate avidity cytotoxic T lymphocytes associated with control of viral load and clinical disease in horses with equine infectious anemia virus. Virology 2003; 313:537-52. [PMID: 12954220 PMCID: PMC3342690 DOI: 10.1016/s0042-6822(03)00344-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Equine infectious anemia virus (EIAV) is a lentivirus that causes persistent infections in horses. We hypothesized that high-avidity CTL specific for nonvariable epitopes might be associated with low viral load and minimal disease in EIAV-infected horses. To test this hypothesis, memory CTL (CTLm) responses were analyzed in two infected horses with high plasma viral loads and recurrent disease (progressors), and in two infected horses with low-to-undetectable viral loads and mild disease (nonprogressors). High-avidity CTLm in one progressor recognized an envelope gp90 epitope, and the data documented for the first time in EIAV that viral variation led to CTL escape. Each of the nonprogressors had high-to-moderate avidity CTLm directed against epitopes within Rev, including the nuclear export and nuclear localization domains. These results suggested that the epitope specificity of high- and moderate-avidity CTLm was an important determinant for disease outcome in the EIAV-infected horses examined.
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Affiliation(s)
- Robert H Mealey
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
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22
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McGuire TC, Leib SR, Mealey RH, Fraser DG, Prieur DJ. Presentation and binding affinity of equine infectious anemia virus CTL envelope and matrix protein epitopes by an expressed equine classical MHC class I molecule. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 171:1984-93. [PMID: 12902502 DOI: 10.4049/jimmunol.171.4.1984] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Control of a naturally occurring lentivirus, equine infectious anemia virus (EIAV), occurs in most infected horses and involves MHC class I-restricted, virus-specific CTL. Two minimal 12-aa epitopes, Env-RW12 and Gag-GW12, were evaluated for presentation by target cells from horses with an equine lymphocyte Ag-A1 (ELA-A1) haplotype. Fifteen of 15 presented Env-RW12 to CTL, whereas 11 of 15 presented Gag-GW12. To determine whether these epitopes were presented by different molecules, MHC class I genes were identified in cDNA clones from Arabian horse A2152, which presented both epitopes. This horse was selected because it is heterozygous for the SCID trait and is used to breed heterozygous females. Offspring with SCID are used as recipients for CTL adoptive transfer, and normal offspring are used for CTL induction. Four classical and three putative nonclassical full-length MHC class I genes were found. Human 721.221 cells transduced with retroviral vectors expressing each gene had equine MHC class I on their surface. Following peptide pulsing, only cells expressing classical MHC class I molecule 7-6 presented Env-RW12 and Gag-GW12 to CTL. Unlabeled peptide inhibition of (125)I-labeled Env-RW12 binding to 7-6-transduced cells demonstrated that Env-RW12 affinity was 15-fold higher than Gag-GW12 affinity. Inhibition with truncated Env-RW12 demonstrated that amino acid positions 1 and 12 were necessary for binding, and single substitutions identified positions 2 and 3 as possible primary anchor residues. Since MHC class I 7-6 presented both epitopes, outbred horses with this allele can be immunized with these epitopes to optimize CTL responses and evaluate their effectiveness against lentiviral challenge.
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MESH Headings
- Amino Acid Substitution/genetics
- Amino Acid Substitution/immunology
- Animals
- Antigen Presentation/genetics
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Cell Line, Transformed
- Cloning, Molecular
- Cytotoxicity, Immunologic/genetics
- Epitopes, T-Lymphocyte/genetics
- Epitopes, T-Lymphocyte/immunology
- Epitopes, T-Lymphocyte/metabolism
- Gene Expression Regulation/immunology
- Gene Library
- Gene Products, env/genetics
- Gene Products, env/immunology
- Gene Products, env/metabolism
- Gene Products, gag/genetics
- Gene Products, gag/immunology
- Gene Products, gag/metabolism
- Genes, MHC Class I
- Histocompatibility Antigens Class I/biosynthesis
- Histocompatibility Antigens Class I/genetics
- Histocompatibility Antigens Class I/immunology
- Histocompatibility Antigens Class I/metabolism
- Horses
- Humans
- Infectious Anemia Virus, Equine/immunology
- Male
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/metabolism
- Protein Binding/genetics
- Protein Binding/immunology
- RNA, Messenger/genetics
- T-Lymphocytes, Cytotoxic/immunology
- T-Lymphocytes, Cytotoxic/metabolism
- Viral Matrix Proteins/genetics
- Viral Matrix Proteins/immunology
- Viral Matrix Proteins/metabolism
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Affiliation(s)
- Travis C McGuire
- Department of Veterinary Microbiology and Pathology, Washington State University College of Veterinary Medicine, Pullman, WA 99164, USA.
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23
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Zhou JH, Ferencik S, Rebmann V, Yang DL, Lu M, Roggendorf M, Grosse-Wilde H. Molecular genetic and biochemical analysis of woodchuck (Marmota monax) MHC class I polymorphism. TISSUE ANTIGENS 2003; 61:240-8. [PMID: 12694573 DOI: 10.1034/j.1399-0039.2003.00036.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The woodchuck (Marmota monax) is an animal model that is used in the study of human hepatitis B virus ( HBV ) infection. A knowledge of woodchuck MHC class I (Mamo-I) genes and gene products is therefore essential for understanding the antigen-specific T-cell responses in this animal model. A number of Mamo-I genes have been identified by molecular cloning and sequencing. However, the allelic nature of these genes has not been proven by classical genetics like the segregation analysis in families. In this study, we analyzed the allelic diversity of Mamo-I in two three-generation woodchuck families including 15 members by sequencing of Mamo-I genes and immunoblotting of Mamo-I proteins after one-dimensional isoelectric focusing (1D-IEF). In addition to four published Mamo-I alleles, six new alleles that belonged to the same locus as the known Mamo-I alleles (Mamo-A) were found within the two woodchuck families. A typical Mendelian segregation of Mamo-I gene and antigens was observed in the families studied. For simple and rapid detection of allelic variability of Mamo-I gene, a typing method based on the detection of PCR products amplified by sequence specific primers (SSP) has been developed and tested in 41 unrelated animals. The most prevalent allele was Mamo-A*01 with a frequency of 21.9% followed by Mamo-A*07 (12.2%). Our study established Mamo-A as a classical MHC class I locus by the polymorphic and allelic nature of Mamo-I gene in the woodchuck.
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Affiliation(s)
- J H Zhou
- Institute of Immunology, Institute of Virology, University Hospital of Essen, Virchowstrasse 171, 45122 Essen, Germany
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24
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McGuire TC, Fraser DG, Mealey RH. Cytotoxic T lymphocytes and neutralizing antibody in the control of equine infectious anemia virus. Viral Immunol 2003; 15:521-31. [PMID: 12513924 DOI: 10.1089/088282402320914476] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Travis C McGuire
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164-7040, USA.
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25
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Rappocciolo G, Birch J, Ellis SA. Down-regulation of MHC class I expression by equine herpesvirus-1. J Gen Virol 2003; 84:293-300. [PMID: 12560560 DOI: 10.1099/vir.0.18612-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is good evidence that cytotoxic T lymphocytes play an important role in the clearance of equine herpesvirus-1 (EHV1) in horses. We have demonstrated that, in common with other alphaherpesviruses, EHV1 infection can lead to dramatic down-regulation of MHC class I expression at the cell surface, a common strategy for pathogen evasion of the host immune response. This down-regulation is specific for MHC class I and does not reflect a general shut-off of host-cell protein synthesis. The use of monoclonal antibodies that recognize different MHC class I epitopes has demonstrated that the effect may be allele- or locus-specific. Use of the viral DNA synthesis inhibitor phosphonoacetic acid, which prevents late viral gene expression, showed that the effect is mediated by an immediate-early or early viral gene, and use of the protein translation inhibitor cycloheximide confirmed that an early gene is primarily responsible. The data indicate that EHV1 infection results in enhanced endocytosis of MHC class I from the cell surface; the only other herpesvirus reported to use this mechanism is human herpesvirus-8. Elucidation of the precise mechanisms used by EHV1 in this process and identification of the genes responsible may lead to improved vaccination strategies.
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Affiliation(s)
- Giovanna Rappocciolo
- Department of Immunology and Pathology, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
| | - James Birch
- Department of Immunology and Pathology, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
| | - Shirley A Ellis
- Department of Immunology and Pathology, Institute for Animal Health, Compton, Newbury, Berkshire RG20 7NN, UK
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26
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Bacon SJ, Ellis SA, Antczak DF. Control of expression of major histocompatibility complex genes in horse trophoblast. Biol Reprod 2002; 66:1612-20. [PMID: 12021038 DOI: 10.1095/biolreprod66.6.1612] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In most mammals, the fetus limits its presentation of paternal antigens to the mother by suppressing the cell-surface expression of proteins of the major histocompatibility complex (MHC) on trophoblast. In the horse, however, functional, polymorphic MHC class I antigens are expressed at high levels on the invasive trophoblast cells of the chorionic girdle between Days 32 and 36 of pregnancy, although not on the adjacent noninvasive trophoblast of the chorion and allantochorion membranes. In this study, the control of MHC class I gene expression was investigated in invasive and noninvasive horse trophoblast, and the MHC class I loci expressed by invasive trophoblast were identified. Northern blot hybridization of Day 33-34 conceptus tissue revealed both transcriptional and posttranscriptional regulation of cell-surface MHC class I expression in horse trophoblast. The invasive MHC class I-positive trophoblast showed levels of steady-state mRNA nearly as high as those in lymphoid tissues from adult horses, whereas noninvasive MHC class I-negative trophoblast also contained transcripts for MHC class I, but at lower levels similar to those present in adult horse nonlymphoid tissue. We also cloned and sequenced polymerase chain reaction products from the transmembrane and cytoplasmic regions of MHC class I transcripts in chorionic girdle and lymphocytes, and determined that horse invasive trophoblast appears to transcribe the same MHC class I loci transcribed in lymphocytes, including both polymorphic and nonpolymorphic loci. These data from the horse demonstrate that functional alloantigen presentation by trophoblast can be a normal part of early pregnancy.
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Affiliation(s)
- S J Bacon
- James A. Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
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27
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Mealey RH, Fraser DG, Oaks JL, Cantor GH, McGuire TC. Immune reconstitution prevents continuous equine infectious anemia virus replication in an Arabian foal with severe combined immunodeficiency: lessons for control of lentiviruses. Clin Immunol 2001; 101:237-47. [PMID: 11683583 PMCID: PMC3342689 DOI: 10.1006/clim.2001.5109] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Acute infection with equine infectious anemia virus (EIAV), a lentivirus of horses, results in a persistent high-level viremia in Arabian foals affected with severe combined immunodeficiency (SCID). This observation argues against the idea that the transient nature of acute lentiviral viremia is solely a function of viral population dynamics. To extend these studies, EIAV-specific immune reconstitution was attempted prior to EIAV challenge in two SCID foals, using adoptively transferred virus-stimulated lymphocytes derived from persistently EIAV-infected half sibling donors. Following transfer, lymphocyte engraftment occurred in one foal, and EIAV-specific cytotoxic T lymphocytes as well as neutralizing antibody activity developed. Following a brief period of plasma viremia in this foal, EIAV replication was controlled and plasma virus could not be detected by RT-PCR or culture. These results provide further direct evidence that a specific immune response is required for termination of plasma viremia in acute lentiviral infections.
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Affiliation(s)
- R H Mealey
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040, USA.
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28
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McGuire TC, Leib SR, Lonning SM, Zhang W, Byrne KM, Mealey RH. Equine infectious anaemia virus proteins with epitopes most frequently recognized by cytotoxic T lymphocytes from infected horses. J Gen Virol 2000; 81:2735-2739. [PMID: 11038386 DOI: 10.1099/0022-1317-81-11-2735] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Efficacious lentiviral vaccines designed to induce cytotoxic T lymphocytes (CTL) in outbred populations with a diverse repertoire of MHC class I molecules should contain or express multiple viral proteins. To determine the equine infectious anaemia virus (EIAV) proteins with epitopes most frequently recognized by CTL from seven horses infected for 0.5 to 7 years, retroviral vector-transduced target cells expressing viral proteins were used in CTL assays. Gag p15 was recognized by CTL from 100% of these infected horses. p26 was recognized by CTL from 86%, SU and the middle third of Pol protein were each recognized by 43%, TM by 29%, and S2 by 14%. Based on these results, it is likely that a construct expressing the 359 amino acids constituting p15 and p26 would contain epitopes capable of stimulating CTL in most horses.
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Affiliation(s)
- Travis C McGuire
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
| | - Steven R Leib
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
| | - Scott M Lonning
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
| | - Wei Zhang
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
| | - Katherine M Byrne
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
| | - Robert H Mealey
- Department of Veterinary Microbiology and Pathology1 and Department of Animal Sciences2, Washington State University, Pullman, WA 99164-7040, USA
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Abstract
The MHC of the urodele amphibian Ambystoma mexicanum consists of multiple polymorphic class I loci linked, so far as yet known, to a single class II B locus. This architecture is very different from that of the anuran amphibian Xenopus. The number of class I loci in the axolotl can vary from 6 to 21 according to the haplotypes as shown by cDNA analysis and Southern blot studies in families. These loci can be classified into seven sequence groups with features ranging from the class Ia to the class Ib type. All individuals express genes from at least three of the seven groups, and all individuals possess the class Ia-like type.
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Affiliation(s)
- B Sammut
- Basel Institute for Immunology Basel, Switzerland.
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30
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Hedrick PW, Parker KM, Miller EL, Miller PS. Major histocompatibility complex variation in the endangered Przewalski's horse. Genetics 1999; 152:1701-10. [PMID: 10430594 PMCID: PMC1460696 DOI: 10.1093/genetics/152.4.1701] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The major histocompatibility complex (MHC) is a fundamental part of the vertebrate immune system, and the high variability in many MHC genes is thought to play an essential role in recognition of parasites. The Przewalski's horse is extinct in the wild and all the living individuals descend from 13 founders, most of whom were captured around the turn of the century. One of the primary genetic concerns in endangered species is whether they have ample adaptive variation to respond to novel selective factors. In examining 14 Przewalski's horses that are broadly representative of the living animals, we found six different class II DRB major histocompatibility sequences. The sequences showed extensive nonsynonymous variation, concentrated in the putative antigen-binding sites, and little synonymous variation. Individuals had from two to four sequences as determined by single-stranded conformation polymorphism (SSCP) analysis. On the basis of the SSCP data, phylogenetic analysis of the nucleotide sequences, and segregation in a family group, we conclude that four of these sequences are from one gene (although one sequence codes for a nonfunctional allele because it contains a stop codon) and two other sequences are from another gene. The position of the stop codon is at the same amino-acid position as in a closely related sequence from the domestic horse. Because other organisms have extensive variation at homologous loci, the Przewalski's horse may have quite low variation in this important adaptive region.
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Affiliation(s)
- P W Hedrick
- Department of Biology, Arizona State University, Tempe, Arizona 85287, USA.
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31
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Abstract
Because major histocompatibility complex (MHC) genes play a major role in the development of acquired immune responses, it is essential to obtain comparative information on their organisation, expression and possible functional dichotomies in different species. In human, three classical, polymorphic class I genes (HLA-A, B- and -C) and four expressed A/B class II gene pairs (HLA-DM, -DP, -DQ and -DR) are each present on all haplotypes. With the exception of the HLA-DRB loci, it has been assumed that a similar rigid organisational situation exists in other mammalian species. However, extensive analysis of the bovine MHC (BoLA) at both the genomic and transcriptional levels has revealed a degree of genetic fluidity not described in other species. None of the four (or more) classical class I genes identified is consistently expressed, and haplotypes differ from one another in both the number and composition of expressed class I genes. Similarly, in the class II region, the number of DQ genes varies between haplotypes in both number and composition. These variations in both class I and II (which appear to reflect differences at the genomic level) are likely to play an important role in cattle immune responses. The observed phenotypic differences in cattle demonstrate very clearly the dynamic nature of the MHC region. This review addresses the functional impact of such variation in different breeds and populations, and its significance in terms of MHC evolution.
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Affiliation(s)
- S A Ellis
- Institute for Animal Health, Compton, UK.
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Shirai K, Sakai T, Oike T. Molecular cloning of bottle-nosed dolphin (Tursiops truncatus) MHC class I cDNA. J Vet Med Sci 1998; 60:1093-6. [PMID: 9819762 DOI: 10.1292/jvms.60.1093] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Using polymerase chain reaction, bottle-nosed dolphin (Tursiops truncatus) major histocompatibility complex (DoLA) class I alpha chain cDNA was cloned and sequenced. Predicted amino acid sequences of DoLA class I alpha chain have cystein residues for intradomain disulfide bond formation and N-linked glycosylation sites, suggesting that DoLA class I alpha chain molecules construct alpha 1, alpha 2, and alpha 3 domain structures. Similarity of DoLA class I alpha chain cDNA to land mammal MHC class I alpha chain cDNA was 90.4% in cattle, 90.2% in horse, 89.4% in sheep, and 87.8% in human. This investigation suggests that DoLA is closely related to land mammals.
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Affiliation(s)
- K Shirai
- Department of Preventive Veterinary Medicine and Animal Health, College of Bioresource Sciences, Nihon University, Kanagawa, Japan
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Cadavid LF, Shufflebotham C, Ruiz FJ, Yeager M, Hughes AL, Watkins DI. Evolutionary instability of the major histocompatibility complex class I loci in New World primates. Proc Natl Acad Sci U S A 1997; 94:14536-41. [PMID: 9405648 PMCID: PMC25046 DOI: 10.1073/pnas.94.26.14536] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/1997] [Accepted: 10/20/1997] [Indexed: 02/05/2023] Open
Abstract
Homologues of the human major histocompatibility complex (MHC) HLA-A, -B, -E, -F, and -G loci are present in all the Catarrhini (Old World primates, apes, and humans), and some of their allelic lineages have survived several speciation events. Analysis of 26 MHC class I cDNAs from seven different genera of New World primates revealed that the Callitrichinae (tamarins and marmosets) are an exception to these rules of MHC stability. In gene trees of primate MHC class I genes, sequences from the Callitrichinae cluster in a genus-specific fashion, whereas in the other genera of New World primates, as in the Catarrhini, they cluster in a transgeneric way. The genus-specific clustering of the Callitrichinae cDNAs indicates that there is no orthology between MHC class I loci in genera of this phyletic group. Additionally, the Callitrichinae genera exhibit limited variability of their MHC class I genes, in contrast to the high variability displayed by all other primates. Each Callitrichinae genus, therefore, expresses its own set of MHC class I genes, suggesting that an unusually high rate of turnover of loci occurs in this subfamily. The limited variability of MHC class I genes in the Callitrichinae is likely the result of the recent origin of these loci.
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Affiliation(s)
- L F Cadavid
- Wisconsin Regional Primate Research Center, University of Wisconsin, 1220 Capitol Court, Madison, WI 53715, USA.
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Osborn CK, Grigoriev V, Crew MD. Modulation of class I major histocompatibility complex antigen cell-surface stability by transmembrane domain length variation. Mol Immunol 1997; 34:771-80. [PMID: 9444976 DOI: 10.1016/s0161-5890(97)00069-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cell surface localization of major histocompatibility complex (MHC) class I proteins is conferred to a large extent by their transmembrane domains (TMs) which exhibit allelic, inter-locus and inter-species variation in both amino acid composition and length. Here, the consequences of TM length variation on trafficking and cell-surface stability were examined using the human MHC class I protein HLA-A2. Transformed B lymphocytes (CIR cells) transfected with an HLA-A2 gene encoding an additional 12 hydrophobic amino acids in the TM exhibited a marked decrease in steady-state cell-surface levels of the HLA-A2 protein relative to cells transfected with the wild-type HLA-A2 gene. Diminished surface expression was observed regardless of the presence or absence of the cytoplasmic domain and could not be accounted for by altered association with beta2-microglobulin. While intracellular trafficking rates were affected by TM length enlargement and/or the absence of cytoplasmic domains, this, as well, could not completely explain the TM length-dependent differential cell-surface levels. Studies using brefeldin A to block transport of HLA-A2 proteins to the cell surface suggested that the diminished cell-surface levels of TM enlarged HLA-A2 proteins was a result of decreased cell-surface stability. A significant negative correlation between cell-surface stability and TM length was observed in a comparison of four HLA-A2 proteins differing only in TM length. Similar studies employing an HLA-A2 protein with the TM of HLA-B27 (which is the same length as the HLA-A2 TM but is only 72% identical) suggested that MHC class I TM length variation, independent of amino acid composition and the cytoplasmic domain, may appreciably affect cell-surface stability.
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Affiliation(s)
- C K Osborn
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock 72205, USA
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36
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Abstract
Single-strand conformational polymorphism (SSCP) gel electrophoresis and DNA sequencing were used to characterize the second exon of the horse DRB homologue as well as to identify eight new DRB alleles. The SSCP gels presented a complex pattern, with phenotypes exhibiting between 4 and 13 bands. The DRB SSCP patterns were studied for two families (6 to 13 bands per pattern). For both families, the patterns showed simple Mendelian inheritance. The polymerase chain reaction products from two individuals possessing homozygous major histocompatibility complex (MHC) alleles by descent were cloned and retested on SSCP gels. All bands derived from the genomic DNA amplification could be accounted for with bands derived from the cloned DNA amplification products. The results were consistent with three DRB loci, though this number may be variable within the domestic horse population. Gene sequences were variable among the different products, and we were unable to assign locus designations for particular sequences. Amplification of cDNA library material derived from one of the individuals who is MHC homozygous by descent showed an SSCP profile suggesting that all three DRB loci are transcribed into mRNA.
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Affiliation(s)
- D G Fraser
- Department of Veterinary Science, 108 Gluck Equine Research Center, University of Kentucky, Lexington, KY 40546-0099, USA
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