Although the low polymorphism of the major histocompatibility complex (MHC) transplantation genes in the Filipino cynomolgus macaque (Macaca fascicularis) is expected to have important implications in the selection and breeding of animals for medical research, detailed polymorphism information is still lacking for many of the duplicated class I genes. To better elucidate the degree and types of MHC polymorphisms and haplotypes in the Filipino macaque population, we genotyped 127 unrelated animals by the Sanger sequencing method and high-resolution pyrosequencing and identified 112 different alleles, 28 at cynomolgus macaque MHC (Mafa)-A, 54 at Mafa-B, 12 at Mafa-I, 11 at Mafa-E, and seven at Mafa-F alleles, of which 56 were newly described. Of them, the newly discovered Mafa-A8*01:01 lineage allele had low nucleotide similarities (<86%) with primate MHC class I genes, and it was also conserved in the Vietnamese and Indonesian populations. In addition, haplotype estimations revealed 17 Mafa-A, 23 Mafa-B, and 12 Mafa-E haplotypes integrated with 84 Mafa-class I haplotypes and Mafa-F alleles. Of these, the two Mafa-class I haplotypes, F/A/E/B-Hp1 and F/A/E/B-Hp2, had the highest haplotype frequencies at 10.6 and 10.2%, respectively. This suggests that large scale genetic screening of the Filipino macaque population would identify these and other high-frequency Mafa-class I haplotypes that could be used as MHC control animals for the benefit of biomedical research.

Experimental infection of Mauritian cynomolgus macaques by simian immunodeficiency virus is a representative model of HIV infection, currently in favour for evaluating the efficacy of new preventive or curative treatments. Extensive studies of major histocompatibility complex (MHC) polymorphism by microsatellites revealed seven haplotypes (H1-H7). We present statistical evidence of the influence of MHC polymorphism on the set-point plasma viral load (PVL). Our analysis was based on the study of 45 Mauritian cynomolgus macaques inoculated by intravenous or intrarectal injection of a 50 AID50 dose of the SIVmac251 virus. The animals received no treatment before or after the inoculation. MHC polymorphism was investigated by means of 20 microsatellites distributed across the MHC and by DRB genotyping using the DGGE sequencing method. Statistical analysis with UNPHASED: software revealed that two markers located in the class IB region significantly influenced the Log PVL and that three class IB haplotypes were significantly associated with lower (H2 or H6) or higher (H4) set-point Log PVL values. Although the impact of MHC on Log PVL was found to be low (around one Log10), it is important to dispose of animals paired for their MHC genotypes, each animal tested for a given treatment and its untreated control, to minimize the influence of the MHC and clearly reveal the effect of the treatment.

The identity of histocompatibility loci, besides human leukocyte antigen (HLA), remains elusive. The major histocompatibility complex (MHC) class I MICA gene is a candidate histocompatibility locus. Here, we investigate its role in a French multicenter cohort of 1,356 kidney transplants. MICA mismatches were associated with decreased graft survival (hazard ratio (HR), 2.12; 95% confidence interval (CI): 1.45–3.11; P < 0.001). Both before and after transplantation anti-MICA donor-specific antibodies (DSA) were strongly associated with increased antibody-mediated rejection (ABMR) (HR, 3.79; 95% CI: 1.94–7.39; P < 0.001; HR, 9.92; 95% CI: 7.43–13.20; P < 0.001, respectively). This effect was synergetic with that of anti-HLA DSA before and after transplantation (HR, 25.68; 95% CI: 3.31–199.41; P = 0.002; HR, 82.67; 95% CI: 33.67–202.97; P < 0.001, respectively). De novo-developed anti-MICA DSA were the most harmful because they were also associated with reduced graft survival (HR, 1.29; 95% CI: 1.05–1.58; P = 0.014). Finally, the damaging effect of anti-MICA DSA on graft survival was confirmed in an independent cohort of 168 patients with ABMR (HR, 1.71; 95% CI: 1.02–2.86; P = 0.041). In conclusion, assessment of MICA matching and immunization for the identification of patients at high risk for transplant rejection and loss is warranted.

To describe the polymorphism of the DRA gene in Macaca fascicularis, we have studied 141 animals either at cDNA level (78 animals from Mauritius, the Philippines, and Vietnam) or genomic level (63 animals from the Philippines, Indonesia, and Vietnam). In total, we characterized 22 cDNA DRA alleles, 13 of which had not been described until now. In the Mauritius population, we confirmed the presence of three DRA alleles. In the Philippine and Vietnam populations, we observed 11 and 14 DRA alleles, respectively. Only two alleles were present in all three populations. All DRA alleles but one differ from the consensus sequence by one to three mutations, most being synonymous; so, only seven DR alpha proteins were deduced from the 22 cDNA alleles. One DRA cDNA allele, Mafa-DRA*02010101, differs from all other alleles by 11 to 14 mutations of which only four are non-synonymous. The two amino acid changes inside the peptide groove of Mafa-DRA*02010101 are highly conservative. The very low proportion of non-synonymous/synonymous mutations is compatible with a purifying selection which is comparable to all previous observations concerning the evolution of the DRA gene in mammals. Homologues of the allele Mafa-DRA*02010101 are also found in two other Asian macaques (Macaca mulatta and Macaca nemestrina). The forces able to maintain this highly divergent allele in three different macaque species remain hypothetical.