Character of chicken polymorphic major histocompatibility complex class II alleles of 3 Chinese local breeds

Novel MHC BLB2 gene polymorphism and its association with IgY concentration and Newcastle disease antibody titer in IPB-D2 chickens

This study aimed to identify the polymorphism of the B Locus Beta 2 (BLB2) gene and its association with immunoglobulin Y (IgY) concentration and Newcastle disease (ND) antibody titer; we analyzed BLB2 gene expression in different categories of ND antibody titers in IPB-D2 chickens. The total sample used was 100 IPB-D2 chickens. Blood samples were collected at 21 weeks old for an ELISA (enzyme-linked immunoassay) test, an HI (hemagglutination inhibition) test, and genotyping. The method for BLB2 polymorphism was Sanger sequencing. Analysis of BLB2 gene expression was performed using the cecal tonsil tissue of IPB-D2 chickens. Polymorphism data were analyzed using SNPstats and DNAsp (DNA Sequence Polymorphism) software. The association of the single-nucleotide polymorphisms (SNPs) with IgY concentration and ND antibody titer was analyzed using SAS software (version 9.2). The genotype mean values were compared by means of a T test. The relative mRNA expression analysis was performed using a quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that 13 SNPs were found in exon 2 and exon 3 in the BLB2 gene. As many as 4 out of the 13 SNPs were associated with IgY concentration. As many as 9 out the 13 SNPs may have changed amino acids. The Δ Ct value showed that the expression of the BLB2 gene in IPB-D2 chickens with high ND antibody titers is higher than IPB-D2 chickens with low ND antibody titers. In conclusion, the AA genotype of g.458 T >  A was associated with high IgY concentrations, and the BLB2 gene presented with a high expression in IPB-D2 chickens with high ND antibody titers.

In silico prediction of B and T cell epitopes based on NDV fusion protein for vaccine development against Newcastle disease virus

Newcastle disease (ND) is known as the most common diseases of economic importance worldwide. Vaccination against virulent strains of Newcastle disease virus (NDV) has failed during some outbreaks. Here, we aimed to assess the epitopes of NDV fusion protein as targets for a peptide-based vaccine. To explore the most antigenic epitopes on the F protein, we retrieved virulent strains of genotype VII from National Center for Biotechnology Information (NCBI). Linear and conformational B-cell epitopes were identified. Moreover, T-cell epitopes with high and moderate binding affinities to human major histocompatibility complex (MHC) class I and class II alleles were predicted using bioinformatics tools. Subsequently, the overlapped epitopes of B-cell and MHC class I and MHC class II were determined. To validate our predictions, the best epitopes were docked, to chicken MHC class I (B-F) alleles using the HADDOCK flexible docking server. Seven ‘high ranked epitopes’ were identified. Among them, ‘LYCTRIVTF’ and ‘MRATYLETL’ showed the highest scores. The other five epitopes including LSGEFDATY, LTTPPYMALK, LYLTELTTV, DCIKITQQV and SIAATNEAV obtained very encouraging results as well. SIAATNEAV had been recognized as a neutralizing epitope of F protein using monoclonal antibodies before. Taken together, our results demonstrated that the identified epitopes needed to be tested by in vitro and in vivo experiments.

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.

Activation of chicken macrophages during in vitro stimulation and expression of immune genes

OBJECTIVE To characterize activation and expression of immune genes of chicken macrophages after in vitro stimulation with lipopolysaccharide (LPS) and mouse erythrocytes. ANIMALS Five 15-day-old chickens and 2 BALB/c mice. PROCEDURES Macrophages were extracted from chicken bone marrow or peripheral blood and then stimulated with cytokines secreted from cell lines L929 and HD11. Stimulated chicken macrophages were further cocultured with LPS or mouse erythrocytes, and gene transcription of some distinctive cytokines was detected by use of a real-time PCR assay. RESULTS Morphological features and phagocytic function of macrophages were characterized. Activated macrophages had an elongated shape with a large cell nucleus, and they had phagocytic function. Distinctive genes encoding the surface marker gene CD11b were identified; high quantities of CD11b were transcribed. Relative transcription of chicken genes BF and BL in mature cells cocultured with both stimuli was lower than for control cells. However, the quantity of genes encoding M1- or M2-distinctive cytokines (interleukin [IL]-1β, IL-10, IL-12, inducible nitric oxide synthase, tumor necrosis factor-α, and transforming growth factor-β) that were transcribed differed significantly between stimulation with LPS and mouse erythrocytes. CONCLUSIONS AND CLINICAL RELEVANCE Chicken macrophages were differentially stimulated by LPS and mouse erythrocytes, which suggested that in vitro stimulation can distinctly influence the transcription and expression of immune genes of chicken macrophages.

Grass carp (Ctenopharyngodon idellus) invariant chain of the MHC class II chaperone protein associates with the class I molecule

The invariant chain (Ii) is an important immune molecule, as it assists major histocompatibility complex (MHC) class II molecules to present antigenic peptides. The relationship between the Ii and MHC molecules in teleosts remains poorly understood. This study focused on the molecular structure of grass carp Ii (gIi), its organ distribution, correlations with gene transcription, and the association with MHC. gIi cDNA was cloned using designed degenerate primers and the rapid amplification of cDNA ends method (RACE). The gIi sequence was 92%-96% similar to that of other teleosts, but only 52%-67% similar to that of mammals, respectively. The gIi gene was distributed in all 12 organs examined by PCR. The gIi gene transcription levels were markedly higher in organs enriched with immune cells than in other organs (P < 0.01). Moreover, positive correlations were detected between transcription levels of the gIi and gMhcI or II genes in different organs (r = 8.415-8.523, P = 0.001). The gIi co-localized on endomembrane systems with either class I or II molecules in co-transfected cells observed by a laser confocal. Further testing confirmed that the gIi bound gMHCI and II molecules. Taken together, these results indicate that the gIi is associated with MHC class I and II molecules, suggesting homology of both MHC molecules.

MHC class I BFIV gene polymorphisms in four Chinese native chicken breeds

The major histocompatibility complex (MHC) includes the most polymorphic genes in vertebrates, and balancing selection has been proposed as a main evolutionary force. Here we present one of the first data sets examining the genetic characteristics of chicken MHC I BFIV molecules in four Chinese native breeds, sourced from different regions in China. In all, 89 BFIV alleles were isolated from 102 individuals sampled, and 13 repeated alleles were observed. No significant correlation was found between genetic differentiation and geographical distance in the phylogenetic tree. BFIV genes exhibited a high level of nucleotide polymorphisms, and most of the polymorphic sites were located in the peptide-binding region (PBR) encoded in exons 2 and 3. A comparison of the three-dimensional structures of PBRs in chicken BFIV and human HLA-A molecules revealed evident structural and functional similarities. The results suggested that MHC I molecules had similar structural features in different species.

Characterization of class II β chain major histocompatibility complex genes in a family of Hawaiian honeycreepers: 'amakihi (Hemignathus virens)

Hawaiian honeycreepers (Drepanidinae) have evolved in the absence of mosquitoes for over five million years. Through human activity, mosquitoes were introduced to the Hawaiian archipelago less than 200 years ago. Mosquito-vectored diseases such as avian malaria caused by Plasmodium relictum and Avipoxviruses have greatly impacted these vulnerable species. Susceptibility to these diseases is variable among and within species. Due to their function in adaptive immunity, the role of major histocompatibility complex genes (Mhc) in disease susceptibility is under investigation. In this study, we evaluate gene organization and levels of diversity of Mhc class II β chain genes (exon 2) in a captive-reared family of Hawaii 'amakihi (Hemignathus virens). A total of 233 sequences (173 bp) were obtained by PCR+1 amplification and cloning, and 5720 sequences were generated by Roche 454 pyrosequencing. We report a total of 17 alleles originating from a minimum of 14 distinct loci. We detected three linkage groups that appear to represent three distinct haplotypes. Phylogenetic analysis revealed one variable cluster resembling classical Mhc sequences (DAB) and one highly conserved, low variability cluster resembling non-classical Mhc sequences (DBB). High net evolutionary divergence values between DAB and DBB resemble that seen between chicken BLB system and YLB system genes. High amino acid identity among non-classical alleles from 12 species of passerines (DBB) and four species of Galliformes (YLB) was found, suggesting that these non-classical passerine sequences may be related to the Galliforme YLB sequences.

Cross-species association of quail invariant chain with chicken and mouse MHC II molecules

There are different degrees of similarity among vertebrate invariant chains (Ii). The aim of this study was to determine the relationship between quail and other vertebrate Ii MHC class II molecules. The two quail Ii isoforms (qIi-1, qIi-2) were cloned by RACE, and qRT-PCR analysis of different organs showed that their expression levels were positively correlated with MHC II gene (B-LB) transcription levels. Confocal microscopy indicated that quail full-length Ii co-localized with MHC II of quail, chicken or mouse in 293FT cells co-transfected with both genes. Immunoprecipitation and western blotting further indicated that these aggregates corresponded to polymers of Ii and MHC class II molecules. This cross-species molecular association of quail Ii with chicken and mouse MHC II suggests that Ii molecules have a high structural and functional similarity and may thereby be used as potential immune carriers across species.