Cloning-based analysis of MHC class II DRB variation and Enterocytozoon bieneusi association in the Amur tiger (Panthera tigris altaica).

The polymorphism of major histocompatibility complex (MHC) class II classical genes is closely related to pathogen resistance, among which the second exon of the DRB gene has the highest variability. In this study, we analyzed exon 2 of the MHC class II DRB gene in 32 captive Amur tigers (Panthera tigris altaica) using a cloning-based sequencing approach to assess genetic diversity and its association with infection by Enterocytozoon bieneusi. A total of 16 DRB alleles were identified, including six novel variants. One allele (Pati-DRB*02) showed a significant positive association with infection (P < 0.05), whereas no significant relationship was detected between heterozygosity and infection status. Phylogenetic analysis revealed that Amur tiger DRB alleles clustered with those from other felid species, supporting trans-species polymorphism. These results indicate that the DRB gene in Amur tigers exhibits a high degree of polymorphism, and that DRB*02 may be a susceptibility gene for E. bieneusi.