Sequence and diversity of DRB genes of Aotus nancymaae, a primate model for human malaria parasites

The New World primate Aotus nancymaae is susceptible to infection with the human malaria parasite Plasmodium falciparum and Plasmodium vivax and has t herefore been recommended by the World Health Organization as a model for e valuation of malaria vaccine candidates. We present here a first step in th e molecular characterization of the major histocompatibility complex (MHC) class II DRB genes of Aotus nancy-maae (owl monkey or night monkey) by nucl eotide sequence analysis of the polymorphic exon 2 segments. In a group of 15 nonrelated animals captivated in the wild, 34 MHC DRB alleles could be i dentified. Six allelic lineages were detected, two of them having human cou nterparts, while two other lineages have not been described in any other Ne w World monkey species studied. As in the common marmoset, the diversity of DRB alleles appears to have arisen largely by point mutations in the beta- pleated sheets and by frequent exchange of fixed sequence motifs in the alp ha-helical portion. Pairs of alleles differing only at amino acid position b86 by an exchange of valine to glycine are present in Aotus, as in humans. Essential amino acid residues contributing to MHC DR peptide binding pocke ts number 1 and 4 are conserved or semiconserved between HLA-DR and Aona-DR B molecules, indicating a capacity to bind similar peptide repertoires. The se results support fully our using Aotus monkeys as an animal model for eva luation of future subunit vaccine candidates.