Research Article: Annotation of bat IG H/L/K loci and analysis of the characteristics of bat BCR-CDR3 repertoires
Abstract:
Bats represent the second largest order of mammals and are the only flying mammals, exhibiting remarkable biological characteristics such as viral tolerance, longevity, and low tumor incidence. Although bats serve as reservoirs for numerous zoonotic viruses, they remain asymptomatic without overt infection. However, the mechanisms and effects of B-cell adaptive immune responses in bats are largely unknown. In mammals, BCR V(D)J gene recombination and the formation of the CDR3 repertoire are key mechanisms underlying B-cell diversity, specificity, and memory responses. In this study, we performed, for the first time, a chromosome-level annotation of the IGK locus (17 KV; 4 KJ;1 LC) and IGL locus (74 LV; 6 LJ-LC gene clusters) in Rhinolophus ferrumequinum , as well as the IGH locus (81 HV; 16 HD; 6 HJ;HC of IgM, IgG, IgE, IgA) and IGL locus (56 LV; 9 LJ-LC gene clusters) in Antrozous pallidus. Comparative evolutionary analyses of each IG locus were also conducted. Using the annotated IG H/K/L constant region gene sequences, we employed 5? Rapid Amplification of cDNA Ends (5?RACE) to construct BCR CDR3 repertoires and perform high-throughput sequencing (HTS). The annotated bat IG H/K/L genes were then used to build a MixCR tool for bat BCR CDR3 HTS analysis. In the spleen and intestinal tissues of bats from Hipposideros armige and Rhinolophus pearsonii/pusillus , we observed high diversity and differential preferential usage of V and J genes in the BCR CDR3 repertoires. Compared with human and mouse BCR CDR3 repertoires, bat CDR3 repertoires exhibited both similarities (e.g., high-frequency motifs, tyrosine enrichment) and distinct differences (e.g., N/P nucleotide Additions/Deletions patterns, amino acid distribution in the CDR3 region). This study provides chromosome-level annotations of IG loci in bats from different families and preliminarily reveals the fundamental characteristics of the bat BCR-CDR3 repertoire, along with key differences compared to human and mouse. Our findings offer comparative base-data, novel insights, tools, and strategies for future in-depth investigations into B-cell adaptive immune responses in bats.
Introduction:
Bats are the only flying mammals, comprising approximately 1,400 species across about 20 families ( 1 , 2 ), and are classified into two suborders: Megachiroptera and Microchiroptera ( 3 , 4 ). Bats exhibit long lifespans, low tumor incidence, and carry numerous highly pathogenic viruses without frequently showing clinical symptoms ( 5 ). Their immune responses differ markedly from those of other mammals, attracting significant research attention. To date, a variety of severe zoonotic viruses have been detected in…
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