Influences of MHC Class II Haplotypes on Avian Influenza Traits in Thai Indigenous Chicken

Abstract

Natural infections with influenza viruses have been reported in a variety of animal species including human, pigs, horses, sea mammals, mustelids and birds. Gccasionally devastating pandemics occur in domestic chickens (broiler and layers) and human. During November 2003 to March 2004 in many countries in Asia, there are outbreaks of H5N1 avian influenza virus, causing of death of infected patients and devastated poultry industry. Some groups of Thai indigenous chickens are survivabie recommended as resistance. These traits were reiated to immunogenetics, especially, the major histocompatibility complex (MHC) class I and class II molecules. The chicken MHC ciass II was investigated as candidate genes for avian influenza resistance. Seven hundred and thirty Thai indigenous chickens of smaii hoider farms in the rurai area of avian influenza outbreaks in the centrai part of Thailand were used in this study. They were separated into two groups, 340 survivable chickens and 390 dead chickens (resistance and susceptible). Genomic DNA were precipitated from blood samples and feathers. Diluted DNA was amplified to identify MHC haplotype. Data were statistically analyzed by χ2 analysis to test significant differences of influences of MHC class II haplotypes on avian influenza traits. The resuits represented ten MHC ciass II hapiotypes, A9, B12, B13, B14, B19, B21, B2, B4, B5, and B6, and included eighteen of their crossbred. The homozygous B21 from these collected sampies had 100 percent of survivai rate and they were the major survivai group. In addition, the heterozygous B21 also showed high survival rate because of co-dominant expression of these genes. In the other way, the homozygous B13 had 100 percent of mortality rate and they were the major group of high mortality rate. These results confirmed that MHC class II haplotypes influenced on avian influenza resistant traits in Thai indigenous chicken. The MHC genes can be used as genetic markers to improve disease resistant traits in chicken. © 2006, Japan Poultry Science Association. All rights reserved.