Raul Rodriguez

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

Abstractu2002The New World primate Aotus nancymaae is susceptible to infection with the human malaria parasite Plasmodium falciparum and Plasmodium vivax and has therefore been recommended by the World Health Organization as a model for evaluation of malaria vaccine candidates. We present here a first step in the molecular characterization of the major histocompatibility complex (MHC) classu2009II DRB genes of Aotus nancymaae (owl monkey or night monkey) by nucleotide sequence analysis of the polymorphic exon 2 segments. In a group of 15 nonrelated animals captivated in the wild, 34u2009MHC DRB alleles could be identified. Six allelic lineages were detected, two of them having human counterparts, while two other lineages have not been described in any other New World monkey species studied. As in the common marmoset, the diversity of DRB alleles appears to have arisen largely by point mutations in the β-pleated sheets and by frequent exchange of fixed sequence motifs in the α-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 pockets number 1 and 4 are conserved or semiconserved between HLA-DR and Aona-DRB molecules, indicating a capacity to bind similar peptide repertoires. These results support fully our using Aotus monkeys as an animal model for evaluation of future subunit vaccine candidates.

Sequence and diversity of MHC DQA and DQB genes of the owl monkey Aotus nancymaae

Abstract. The New World primate Aotus nancymaae has been recommended by the World Health Organization (WHO) as a model for evaluation of malaria vaccine candidates, given its susceptibility to experimental infection with the human malaria parasites Plasmodium falciparum and Plasmodium vivax. We present here the nucleotide sequences of the complete cDNA of MHC-DQA1 and of the polymorphic exon 2 segments of MHC-DQB1/DQB2. In a group of three nonrelated animals captured in the wild, five alleles of MHC-DQA1 could be identified. They all belong to one lineage, namely Aona-DQA1*27. This lineage has not been described in any other New World monkey species studied. In a group of 19 unrelated animals, 14 Aona-DQB1 alleles could be identified which are grouped into the two lineages Aona-DQB1*22 and Aona-DQB1*23. These lineages have been described previously in the common marmoset and cotton-top tamarin. In addition, two Aona-DQB2 sequences could be identified which are highly similar to HLA-DQB2 sequences. Essential amino acid residues contributing to MHC DQ peptide binding pockets number 1 and 4 are conserved or semi-conserved between HLA-DQ and Aona-DQ molecules, indicating a capacity to bind similar peptide repertoires. These results fully support the use of Aotus monkeys as an animal model for evaluation of future subunit vaccine candidates.

Shifting the Polarity of some Critical Residues in Malarial Peptides Binding to Host Cells is a Key Factor in Breaking Conserved Antigens Code of Silence

As microbes use many mechanisms for avoiding immunological pressure, new strategies must be developed to bypass the immunological code of silence of conserved, functionally-important amino acid sequences, such as those involved in high activity binding peptides (HABPs) attaching to their host cells. Hundreds of experiments in large numbers of Aotus monkeys revealed that this immunological code of silence could be broken by shifting the polarity of some critical host cell binding residues in these HABPs by substituting F for R and vice versa, Y<-->W, L<-->H, I<-->N, P<-->D, M<-->K or E, C<-->T, V<-->N or S; there are special rules for A, G and S. (1)H-nuclear magnetic resonance of these modified, immunogenic, protection-inducing HABPs and molecular modelling revealed that such modifications induced appropriate fitting into specific HLA-DRbeta1 Pockets, suggesting the presence of new pockets and a haplotype- and allele-specific conscious TCR. A highly immunogenic and protection-inducing anti-malarial vaccine can thus be produced.

Sequence and expression of MHC-DPB1 molecules of the New World monkey Aotus nancymaae, a primate model for Plasmodium falciparum

Abstract.Aotus nancymaae represents an animal model for the pre-clinical evaluation of blood-stage vaccine candidates against Plasmodium falciparum and Plasmodium vivax. We present here the nucleotide sequences of exon 2 and 3 of MHC-DPB1 genes. In a group of seven unrelated animals captured in the wild, three alleles of MHC-DPB1 exon 2 could be identified. Phylogenetic analysis shows that in contrast to Aona-DRB and -DQB, the Aona-DPB1 exon 2 amino acid sequences cluster in a species-specific manner. No evidence could be found for the conservation of allelic lineages pre-dating the divergence of Old and New World monkeys. Additionally, two nucleotide sequences of MHC-DPB1 exon 3 could be identified differing in one synonymous base exchange. Phylogenetic analysis of Aona-DPB1 exon 3 amino acid sequence shows that it clusters together with human sequences separately from the New World monkey Saguinus oedipus. Aona-DP heterodimers are expressed on the surface of Aotus cells, as detected by staining with a cross-reactive monoclonal antibody, and can therefore present antigenic peptides to the cellular immune system.

Schistosoma mansoni infection in owl monkeys (Aontus nancymai): Evidence for the early elimination of adult worms

Detailed parasitologic, serologic, clinical and histopathologic studies were conducted in owl monkeys (Aotus nancymai) exposed to varying numbers of cercariae of Schistosoma mansoni. All the experimental animals had clinical symptoms suggestive of infection (weight loss diarrhoea, mucus in stools, etc.) which were not seen in uninfected individuals. The only A. vociferans included in this study passed S. mansoni eggs 8 weeks after infection. None of the A. nancymai passed eggs in their faeces. No adult worms were recovered following perfusion of the sacrificed experimental monkeys, suggesting that they were early eliminated. Serological techniques (ELISA-SEA and COPT) allowed diagnosis of infection, starting 9 weeks post challenge, in all but one A. nancymai exposed to 100 cercariae. Granulomas containing eggs were observed predominantly in liver and less extensively in intestine, suggesting that adult worms were mainly lodged in the intrahepatic portal system. We conclude that A. nancymai is susceptible to infection with S. mansoi, with the worms reaching sexual maturity, but being eliminated shortly after oviposition.