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

<p>This study aimed to identify the polymorphism of the B Locus Beta 2 (<i>BLB2</i>) gene and its association with immunoglobulin Y (IgY) concentration and Newcastle disease (ND) antibody titer; we analyzed <i>BLB2</i> 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 <i>BLB2</i> polymorphism was Sanger sequencing. Analysis of <i>BLB2</i> 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 <i>BLB2</i> 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 <span class="inline-formula">Δ</span>Ct value showed that the expression of the <i>BLB2</i> 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 <span class="inline-formula">&gt;</span> A was associated with high IgY concentrations, and the <i>BLB2</i> gene presented with a high expression in IPB-D2 chickens with high ND antibody titers.</p>