Genotypes of chicken major histocompatibility complex B locus associated with regression of Rous sarcoma virus J-strain tumors

Exonic SNP in MHC-DMB2 is associated with gene expression and humoral immunity in Japanese quails

The DMB2 gene is widely expressed at high levels in avian. This gene plays an important role in humoral immunity. The aim of this study was to investigate the effects of 361 G > C Single nucleotide polymorphism (SNP) on DMB2 protein structure and gene expression to determine how the 361 G > C SNP affects humoral immune response in Japanese quails. 0.2 mL of 5% sheep red blood cell (SRBC) was injected into breast muscle of 130 Japanese quails on 28 days. After DNA extraction, PCR was carried out to amplify a 333-base pair DNA fragment from the exon 2 of DMB2 gene. The pattern of all samples was determined through RFLP technique. PCR-RFLP results identified two alleles segregating (C, G) as three genotypes (CC, CG and GG) in Japanese Quails. The antibody response to SRBC with CC genotype was significantly higher than the CG and GG genotypes (P < 0.01). In silico analysis showed that the 361 G > C SNP has no effect on the physicochemical properties and 3D structure. The results of RT-qPCR indicated that the effect of genotype on gene expression is significant, so that the expression of CC genotype is more than CG and GG genotype. It can be inferred that the 361 G > C SNP in the exon 2 of MHC-DMB2 gene is not desirable. This mutation decreases humoral immune response by reducing DMB2 gene expression.

Genetic diversity at major histocompatibility complex and its effect on production and immune traits in indigenous chicken breeds of India

The genetic diversity at major histocompatibility complex (MHC) in indigenous chicken breeds of India (Ghagus and Nicobari) in comparison with the White Leghorn (WLH) breed was investigated by genotyping the MHC-linked LEI0258 marker. Altogether 38 alleles and 96 genotypes were observed among three breeds. The observed and effective alleles were highest in Ghagus (23, 8.3) followed by Nicobari (14, 3.2) and WLH (10 and 2.2) breeds. The size of alleles ranged from 193 to 489 bp in Ghagus, 193 to 552 bp in Nicobari and 241 to 565 bp in the WLH breed. The number of private alleles was also highest in Ghagus (18) followed by Nicobari (8) and WLH (5) breeds. The most frequent allele was 261 bp in WLH (66 %), 343 bp in Nicobari (50.4 %) and 309 bp in the Ghagus (28.15 %) breed. Observed and expected heterozygosities were highest in Ghagus (0.83, 0.88) followed by Nicobari (0.58, 0.68) and WLH (0.53, 0.54). The genetic distance (Nei) between Ghagus and Nicobari breeds (2.24) was higher as compared to that of Ghagus and WLH (1.23) and that between Nicobari and WLH breeds (0.89). Association analysis revealed significant influence of MHC alleles on body weight, egg production in Ghagus and WLH breeds and antibody titres to Newcastle disease vaccine in the Nicobari breed.

Advances in methodologies for detecting MHC-B variability in chickens

The chicken major histocompatibility B complex (MHC-B) region is of great interest owing to its very strong association with resistance to many diseases. Variation in the MHC-B was initially identified by hemagglutination of red blood cells with specific alloantisera. New technologies, developed to identify variation in biological materials, have been applied to the chicken MHC. Protein variation encoded by the MHC genes was examined by immunoprecipitation and 2-dimensional gel electrophoresis. Increased availability of DNA probes, PCR, and sequencing resulted in the application of DNA-based methods for MHC detection. The chicken reference genome, completed in 2004, allowed further refinements in DNA methods that enabled more rapid examination of MHC variation and extended such analyses to include very diverse chicken populations. This review progresses from the inception of MHC-B identification to the present, describing multiple methods, plus their advantages and disadvantages.

LEI0258 microsatellite variability and its association with humoral and cell mediated immune responses in broiler chickens

Major histocompatibility complex (MHC) has a profound influence on disease resistance or susceptibility, productivity and important economic traits in chicken. Association of the MHC with a wide range of immune responses makes it a valuable predictive factor for the disease pathogenesis and outcome. The tandem repeat LEI0258 is a genetic marker which is located within the B locus of chicken MHC and strongly associated with serologically defined haplotypes. LEI0258 microsatellite marker was applied to investigate the MHC polymorphism in Ross 308 broiler chicken (N=104). Association of LEI0258 alleles with humoral and cell mediated immune responses to Newcastle disease (ND), Infectious bursal disease (IBD) and Avian influenza (AI) vaccines were also examined. LEI0258 polymorphism was determined by PCR-based fragment analysis, and association of LEI0258 alleles with immune responses were evaluated using multivariate regression analysis and GLM procedures. A total of seven alleles ranging from 195 to 448bp were found, including two novel alleles (263 and 362bp) that were unique in Ross 308 broiler population. Association study revealed a significant influence of MHC alleles on humoral and cellular immune responses in Ross population (P<0.05). Alleles 385 and 448bp were associated with increased peripheral blood lymphocyte proliferation response. Alleles 300, 362 and 448bp had a positive effect on immune responses to Infectious bursal disease vaccine, and allele 263bp was significantly correlated with elevated antibody titer against Newcastle disease vaccine. Results obtained from this study confirmed the important role of MHC as a candidate gene marker for immune responses that could be used in genetic improvement of disease-resistant traits and resource conservation in broiler population.

A high-density SNP panel reveals extensive diversity, frequent recombination and multiple recombination hotspots within the chicken major histocompatibility complex B region between BG2 and CD1A1

BACKGROUND

The major histocompatibility complex (MHC) is present within the genomes of all jawed vertebrates. MHC genes are especially important in regulating immune responses, but even after over 80 years of research on the MHC, much remains to be learned about how it influences adaptive and innate immune responses. In most species, the MHC is highly polymorphic and polygenic. Strong and highly reproducible associations are established for chicken MHC-B haplotypes in a number of infectious diseases. Here, we report (1) the development of a high-density SNP (single nucleotide polymorphism) panel for MHC-B typing that encompasses a 209,296 bp region in which 45 MHC-B genes are located, (2) how this panel was used to define chicken MHC-B haplotypes within a large number of lines/breeds and (3) the detection of recombinants which contributes to the observed diversity.

METHODS

A SNP panel was developed for the MHC-B region between the BG2 and CD1A1 genes. To construct this panel, each SNP was tested in end-point read assays on more than 7500 DNA samples obtained from inbred and commercially used egg-layer lines that carry known and novel MHC-B haplotypes. One hundred and one SNPs were selected for the panel. Additional breeds and experimentally-derived lines, including lines that carry MHC-B recombinant haplotypes, were then genotyped.

RESULTS

MHC-B haplotypes based on SNP genotyping were consistent with the MHC-B haplotypes that were assigned previously in experimental lines that carry B2, B5, B12, B13, B15, B19, B21, and B24 haplotypes. SNP genotyping resulted in the identification of 122 MHC-B haplotypes including a number of recombinant haplotypes, which indicate that crossing-over events at multiple locations within the region lead to the production of new MHC-B haplotypes. Furthermore, evidence of gene duplication and deletion was found.

CONCLUSIONS

The chicken MHC-B region is highly polymorphic across the surveyed 209-kb region that contains 45 genes. Our results expand the number of identified haplotypes and provide insights into the contribution of recombination events to MHC-B diversity including the identification of recombination hotspots and an estimation of recombination frequency.

Structural analysis of MHC alleles in an RSV tumour regression chicken using a BAC library

The chicken major histocompatibility complex (MHC-B locus) has a strong association with resistance and susceptibility to numerous diseases. We have found a B haplotype designated WLA that associated with the regression of tumours caused by Rous sarcoma virus J strain (RSV-J). Haplotype WLA was identical to the regressive B6 haplotype when partial genotyping was performed (Poultry Science, 89, 2010, 651). We then constructed a bacterial artificial chromosome (BAC) library from a WLA homozygote chicken to evaluate the structure of this regression haplotype and compared it to those of the B6 haplotype. Comparison between WLA and B6 above 59 kb within the 167 kb, including 14 genes from BG1 to BF2, revealed 75 SNPs and 14 indels. However, several genes were identical between WLA and B6, including the BF1 and BF2 genes, which encode a class I molecule previously suggested to be related to the regression phenotype. The BLB2 gene encoding the MHC class II beta chain showed the greatest diversity, with 19 non-synonymous SNPs. A comparison of WLA and B6 haplotpyes that are associated with tumour regression and RIRa and B24 haplotypes associated with tumour progression suggests that DMA1, DMA2, BRD2, TAPBP and BLB2 genes are not involved in the intensity of RSV J tumour regression.

Comparative study of tumorigenesis and tumor immunity in invertebrates and nonmammalian vertebrates

Despite intense study in mammals, the different roles played by the immune system in detecting (immunosurveillance), controlling and remodeling (immunoediting) neoplasia, and perhaps in metastasis are not fully understood. In this review, I will present evidence of neoplasia and invasive malignancy, as well as tumor immunity in invertebrates and nonmammalian vertebrates. I will also present a comparative and evolutionary view of the complex interactions between neoplasia and the host immune system. Overall, I wish to go beyond the too simplistic dichotomy between invertebrates with innate immunity that are only affected with benign neoplasia and vertebrates with adaptive immunity that are affected by metastatic malignancies or cancer.