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

Hepatic lesions in captive owl monkeys (Aotus infulatus) with ultrasonographic "starry sky" liver

BACKGROUND

The "starry sky" (SK) liver is ultrasonographic pattern characterized by multiple hyperechogenic foci in hepatic parenchyma. The study aimed to characterize the microscopic hepatic lesions in captive owl monkeys with SK liver.

METHODS

Thirty-seven clinically healthy owl monkeys had their liver scanned and 18 of them had liver biopsy. Animals with SK and peliosis hepatis (PH) were subjected to immunohistochemical and molecular screening for Bartonella spp.

RESULTS

SK liver occurred in 59.4% (22/37) of the owl monkeys. Biopsied animals showed steatosis, hydropic degeneration, hemosiderosis, PH, and multifocal granulomatous hepatitis. Two monkeys had SK, granulomatous hepatitis, and PH which were negative for Bartonella spp.

CONCLUSIONS

PH and granulomatous hepatitis associated with hepatocellular degenerative lesions may present as hyperechoic nodular liver lesions consisted of SK liver; therefore, concomitant occurrence of two lesions or more contributed to the hepatic SK pattern among owl monkeys and such cases might be clinically monitored.

Characterising a microsatellite for DRB typing in Aotus vociferans and Aotus nancymaae (Platyrrhini)

Non-human primates belonging to the Aotus genus have been shown to be excellent experimental models for evaluating drugs and vaccine candidates against malaria and other human diseases. The immune system of this animal model must be characterised to assess whether the results obtained here can be extrapolated to humans. Class I and II major histocompatibility complex (MHC) proteins are amongst the most important molecules involved in response to pathogens; in spite of this, the techniques available for genotyping these molecules are usually expensive and/or time-consuming. Previous studies have reported MHC-DRB class II gene typing by microsatellite in Old World primates and humans, showing that such technique provides a fast, reliable and effective alternative to the commonly used ones. Based on this information, a microsatellite present in MHC-DRB intron 2 and its evolutionary patterns were identified in two Aotus species (A. vociferans and A. nancymaae), as well as its potential for genotyping class II MHC-DRB in these primates.

Characterisation and comparative analysis of MHC-DPA1 exon 2 in the owl monkey (Aotus nancymaae)

The Aotus nancymaae (owl monkey) is an important animal model in biomedical research, particularly for the preclinical evaluation of vaccine candidates against Plasmodium falciparum and Plasmodium vivax, which require a precisely typed major histocompatibility complex. The exon 2 from A. nancymaae MHC-DPA1 gene was characterised in order to infer its allelic diversity and evolutionary history. Aona-DPA1 shows no polymorphism and is related to other primate DPA alleles (including Catarrhini and Platyrrhini), constituting an ancient trans-specific and strongly supported lineage with different variability and selective patterns when compared to other primate-MHC-DPA1 lineages. A. nancymaae monkeys have thus a smaller MHC-DP polymorphism than MHC-DQ or MHC-DR.

Experimental schistosomiasis in the common marmoset Callithrix jacchus

In order to evaluate Callithrix jacchus as an animal model for mansoni schistosomiasis, a group of 10 male animals were once percutaneously exposed to 250 cercariae of the Schistosoma mansoni SLM (São Lourenço da Mata) strain. Animals were periodically bled for measuring serum level of enzymes and proteins and for blood cell counting. When comparing pre-infection to post-infection values, a significant increase was found for alkaline phosphatase at 15 to 120 days p.i., differential counts of eosinophil at 45 and 60 days, and total protein and global eosinophil counts at 120 days. No Schistosoma mansoni eggs were found in stools. Adult worms of small size were recovered from five animals. At day 120, the number of Schistosoma mansoni eggs/g of tissue was 0-289.7 (liver), 0-30.1 (large intestine) and 0-171.4 (small intestine). These findings lead us to classify Callithrix jacchus as a non-permissive host to the SLM strain of Schistosoma mansoni.

Characterizing T-cell receptor gamma-variable gene in Aotus nancymaae owl monkey peripheral blood

Gammadelta T lymphocytes have a heterodimeric complex formed by the association of gamma and delta chains as receptor. Proliferation of this lymphocyte population has been observed, when infection by several pathogens such as Mycobacterium tuberculosis and Plasmodium spp. occurs. The New World Monkey Aotus nancymaae has become a very good experimental model for the immunological and physiopathological study of these infectious agents. The A. nancymaae gamma-variable region was characterized from peripheral blood samples by using cDNA and genomic DNA polymerase chain reaction amplification, DNA sequencing, and dot-blot hybridization techniques. Seventeen different T-cell receptor gamma-variable (TCRGV) sequences were obtained. These sequences were distributed among TCRGV subsets 1, 2, or 3, according to human subset classification. Although no subset 4 amplification was obtained, this subset was detected by dot-blot hybridization. The presence of these 4 subsets resembles the behavior displayed by 'gammadelta-low species' (humans and mice), where high diversity among these lymphocytes can be observed. Homologies greater than 70% were found with respect to humans. Sequence convergence between human and A. nancymaae subsets 1 and 3 highlights Aotus as a promising model for studying these lymphocyte functions.

Aotus monkeys: their great value for anti-malaria vaccines and drug testing

Non-human primates represent a valuable resource for testing potential vaccines candidates and drugs for human use. Malaria remains one of the greatest burdens for the humanity represented by approximately 500 million new clinical cases per year worldwide and at least two million deaths caused annually. Additional control measures such as vaccines and new anti-malarial compounds are therefore urgently needed. Safety and protective efficacy studies in animal models are critical steps for vaccines and drugs development and primate models are probably the most appropriate for this purpose. Although Aotus genus provides several species susceptible to both Plasmodium falciparum and Plasmodium vivax, having different susceptibility to malaria, Aotus lemurinus griseimembra represents the best current malaria primate model because of its high susceptibility to infection by blood forms and sporozoites of both species of Plasmodium. Although the ultimate validation of this model depends upon human trials, over the past two decades these monkeys have proved very useful to test multiple malaria vaccine candidates prior to trials in humans. A good correlation between the B- and T-cell epitopes recognised by humans and by immunised monkeys has been documented, and cross reactivity between reagents for human and Aotus cytokines and lymphocyte markers have been identified and are facilitating the selection of vaccine candidates for clinical trials. Aotus also represents a good model for the screening of anti-malarial drugs and the understanding of malaria pathogenesis as well. In view of the decreasing availability of these primates, breeding programs and biomedical research facilities must be improved in countries of primate origin.

Functional and structural similarity of V gamma 9V delta 2 T cells in humans and Aotus monkeys, a primate infection model for Plasmodium falciparum malaria

Gammadelta T cells are implicated to play crucial roles during early immune responses to pathogens. A subset of human gammadelta T cells carrying the Vgamma9Vdelta2 TCR recognize small, phosphorylated nonpeptidic Ags. However, the precise role of these cells and the ligands recognized in human immune responses against pathogens remains unclear because of the lack of suitable animal models. We have analyzed the reactivity of spleen cells of the New World monkey Aotus nancymaae against isopentenyl pyrophosphate (IPP), a phosphorylated microbial metabolite selectively activating Vgamma9Vdelta2 T cells. Spleen cells were stimulated by IPP and the expanding cell population expressed the Vgamma9 TCR. TRGV-J and TRDV-D-J rearrangements expressed by IPP-stimulated cells of Aotus were analyzed by RT-PCR and DNA sequencing. The TRGV-J and TRDV-D-J rearrangements expressed by IPP-stimulated Aotus and human gammadelta T cells were similar with respect to 1) TCR gene segment usage, 2) a high degree of germline sequence homology of the TCR gene segments used, and 3) the diversity of the CDR3 regions. Phylogenetic analysis of human, Pan troglodytes, and A. nancymaae TRGV gene segments showed that the interspecies differences are smaller than the intraspecies differences with TRGV9 gene segments located on a distinct clade of the phylogenetic tree. The structural and functional conservation of Vgamma9Vdelta2 T cells in A. nancymaae and humans implicates a functionally important and evolutionary conserved mechanism of recognition of phosphorylated microbial metabolites.