Molecular Characterization of MHC Class I Alpha 1 and 2 Domains in Asian Seabass (Lates calcarifer)

The Asian seabass is of importance both as a farmed and wild animal. With the emergence of infectious diseases, there is a need to understand and characterize the immune system. In humans, the highly polymorphic MHC class I (MHC-I) molecules play an important role in antigen presentation for the adaptive immune system. In the present study, we characterized a single MHC-I gene in Asian seabass (Lates calcarifer) by amplifying and sequencing the MHC-I alpha 1 and alpha 2 domains, followed by multi-sequence alignment analyses. The results indicated that the Asian seabass MHC-I α1 and α2 domain sequences showed an overall similarity within Asian seabass and retained the majority of the conserved binding residues of human leukocyte antigen-A2 (HLA-A2). Phylogenetic tree analysis revealed that the sequences belonged to the U lineage. Mapping the conserved binding residue positions on human HLA-A2 and grass carp crystal structure showed a high degree of similarity. In conclusion, the availability of MHC-I α1 and α2 sequences enhances the quality of MHC class I genetic information in Asian seabass, providing new tools to analyze fish immune responses to pathogen infections, and will be applicable in the study of the phylogeny and the evolution of antigen-specific receptors.