Characterization of Mauritian cynomolgus macaque Fc gamma receptor alleles using long-read sequencing1

Fc gamma receptors (FCGRs) are immune cell surface proteins that bind IgG and facilitate cytokine production, phagocytosis, and antibody-dependent cell-mediated cytotoxicity. FCGRs play a critical role in immunity; variation in these genes is implicated in autoimmunity and other diseases. Cynomolgus macaques are an excellent animal model for many human diseases, and Mauritian cynomolgus macaques (MCMs) are particularly useful due to their restricted genetic diversity. Previous studies of MCM immune gene diversity have focused on the major histocompatibility complex (MHC) and killer cell immunoglobulin-like receptor (KIR). Here we characterize FCGR diversity in 48 MCMs, using PacBio long-read sequencing to identify novel alleles of each of the four expressed MCM FCGR genes. We also developed a high-throughput FCGR genotyping assay, which we used to determine allele frequencies and identify FCGR haplotypes in more than 500 additional MCMs. We found three alleles for FCGR1A , seven each for FCGR2A and FCGR2B , and four for FCGR3A ; these segregate into eight haplotypes. We also assessed whether different FCGR alleles confer different antibody binding affinities by surface plasmon resonance, and found minimal difference in binding affinities across alleles for a panel of wild type and Fc-engineered human IgG. This work suggests that although MCMs may not fully represent the diversity of FCGR responses in humans, they may offer highly reproducible results for monoclonal antibody therapy and toxicity studies.