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

Major histocompatibility complex class II DR and DQ evolution and variation in wild capuchin monkey species (Cebinae)

The major histocompatibility complex (MHC) is an important gene complex contributing to adaptive immunity. Studies of platyrrhine MHC have focused on identifying experimental models of immune system function in the equivalent Human Leukocyte Antigen (HLA). These genes have thus been explored primarily in captive platyrrhine individuals from research colonies. However, investigations of standing MHC variation and evolution in wild populations are essential to understanding its role in immunity, sociality and ecology. Capuchins are a promising model group exhibiting the greatest habitat diversity, widest diet breadth and arguably the most social complexity among platyrrhines, together likely resulting in varied immunological challenges. We use high-throughput sequencing to characterize polymorphism in four Class II DR and DQ exons for the first time in seven capuchin species. We find evidence for at least three copies for DQ genes and at least five for DRB, with possible additional unrecovered diversity. Our data also reveal common genotypes that are inherited across our most widely sampled population, Cebus imitator in Sector Santa Rosa, Costa Rica. Notably, phylogenetic analyses reveal that platyrrhine DQA sequences form a monophyletic group to the exclusion of all Catarrhini sequences examined. This result is inconsistent with the trans-species hypothesis for MHC evolution across infraorders in Primates and provides further evidence for the independent origin of current MHC genetic diversity in Platyrrhini. Identical allele sharing across cebid species, and more rarely genera, however, does underscore the complexity of MHC gene evolution and the need for more comprehensive assessments of allelic diversity and genome structure.

Plasmodium falciparum pre-erythrocytic stage vaccine development

Worldwide strategies between 2010 and 2017 aimed at controlling malarial parasites (mainly Plasmodium falciparum) led to a reduction of just 18% regarding disease incidence rates. Many biologically-derived anti-malarial vaccine candidates have been developed to date; this has involved using many experimental animals, an immense amount of work and the investment of millions of dollars. This review provides an overview of the current state and the main results of clinical trials for sporozoite-targeting vaccines (i.e. the parasite stage infecting the liver) carried out by research groups in areas having variable malaria transmission rates. However, none has led to promising results regarding the effective control of the disease, thereby making it necessary to complement such efforts at finding/introducing new vaccine candidates by adopting a multi-epitope, multi-stage approach, based on minimal subunits of the main sporozoite proteins involved in the invasion of the liver.

Igh locus structure and evolution in Platyrrhines: new insights from a genomic perspective

Non-human primates have been used as animal models because of their phylogenetic closeness to humans. However, the genetic differences between humans and non-human primates must be considered to select the appropriate animal models. Recently, New World monkeys (Platyrrhines) have generated a higher interest in biomedical research, especially in assessing vaccine safety and immunogenicity. Given the continued and renewed interest in Platyrrhines as biomedical models, it is a necessary to have a better and more complete understanding of their immune system and its implications for research. Immunoglobulins (Ig) are the main proteins that mediate humoral immunity. These proteins have evolved as part of an adaptive immune response system derived from ancient vertebrates. There are at least four Ig classes in Prosimians, whereas five have been reported in Catarrhines. Information on the structure and evolution of the loci containing immunoglobulin heavy chain constant genes (Igh) in Platyrrhines, however, is limited. Here, Igh loci were characterized in 10 Platyrrhines using the available whole genome sequences. Human and Macaca Igh loci were also assessed to compare them with their Platyrrhines counterparts. Differences in Igh locus structure were observed between Platyrrhines and Catarrhines. Noteworthy changes occur in the γ gene, which encodes a key Ig involved in organism defense that would favor protection after vaccination. The remarkable differences between the immunoglobulin proteins of Platyrrhines and Catarrhines warrant a cautionary message to biomedical researchers.

NHP-immunome: A translational research-oriented database of non-human primate immune system proteins

We are currently living the advent of a new age for medicine in which basic research is being quickly translated into marketable drugs, and the widespread access to genomics data is allowing the design and implementation of personalized solutions to medical conditions. Non-human primates (NHP) have gained an essential role in drug discovery and safety testing due to their close phylogenetic relationship to humans. In this study, a collection of well characterized genes of the human immune system was used to define the orthology-based immunome in four NHP species, with carefully curated annotations available based on multi-tissue RNA-seq datasets. A broad variation in the frequency of expressed protein isoforms was observed between species. Finally, this analysis also revealed the lack of expression of at least four different chemokines in new-world primates. In addition, transcripts corresponding to four genes including interleukin 12 subunit alpha were expressed in humans but no other primate species analyzed. Access to the non-human primate immunome is available in http://www.fidic.org.co:90/proyecto/.

IMPIPS: the immune protection-inducing protein structure concept in the search for steric-electron and topochemical principles for complete fully-protective chemically synthesised vaccine development

Determining immune protection-inducing protein structures (IMPIPS) involves defining the stereo-electron and topochemical characteristics which are essential in MHC-p-TCR complex formation. Modified high activity binding peptides (mHABP) were thus synthesised to produce a large panel of IMPIPS measuring 26.5 ±3.5Å between the farthest atoms fitting into Pockets 1 to 9 of HLA-DRβ1* structures. They displayed a polyproline II-like (PPII_L) structure with their backbone O and N atoms orientated to establish H-bonds with specific residues from HLA-DRβ1*-peptide binding regions (PBR). Residues having specific charge and gauche⁺ orientation regarding p3χ1, p5χ2, and p7χ1 angles determined appropriate rotamer orientation for perfectly fitting into the TCR to induce an appropriate immune response. Immunological assays in Aotus monkeys involving IMPIPS mixtures led to promising results; taken together with the aforementioned physicochemical principles, non-interfering, long-lasting, protection-inducing, multi-epitope, multistage, minimal subunit-based chemically-synthesised peptides can be designed against diseases scourging humankind.

Genetic diversity and differentiation of the rhesus macaque (Macaca mulatta) population in western Sichuan, China, based on the second exon of the major histocompatibility complex class II DQB (MhcMamu-DQB1) alleles

BACKGROUND

Rhesus macaques living in western Sichuan, China, have been separated into several isolated populations due to habitat fragmentation. Previous studies based on the neutral or nearly neutral markers (mitochondrial DNA or microsatellites) showed high levels of genetic diversity and moderate genetic differentiation in the Sichuan rhesus macaques. Variation at the major histocompatibility complex (MHC) loci is widely accepted as being maintained by balancing selection, even with a low level of neutral variability in some species. However, in small and isolated or bottlenecked populations, balancing selection may be overwhelmed by genetic drift. To estimate microevolutionary forces acting on the isolated rhesus macaque populations, we examined genetic variation at Mhc-DQB1 loci in 119 wild rhesus macaques from five geographically isolated populations in western Sichuan, China, and compared the levels of MHC variation and differentiation among populations with that previously observed at neutral microsatellite markers.

RESULTS

23 Mamu-DQB1 alleles were identified in 119 rhesus macaques in western Sichuan, China. These macaques exhibited relatively high levels of genetic diversity at Mamu-DQB1. The Hanyuan population presented the highest genetic variation, whereas the Heishui population was the lowest. Analysis of molecular variance (AMOVA) and pairwise FST values showed moderate genetic differentiation occurring among the five populations at the Mhc-DQB1 locus. Non-synonymous substitutions occurred at a higher frequency than synonymous substitutions in the peptide binding region. Levels of MHC variation within rhesus macaque populations are concordant with microsatellite variation. On the phylogenetic tree for the rhesus and crab-eating macaques, extensive allele or allelic lineage sharing is observed between the two species.

CONCLUSIONS

Phylogenetic analyses confirm the apparent trans-species model of evolution of the Mhc-DQB1 genes in these macaques. Balancing selection plays an important role in sharing allelic lineages between species, but genetic drift may share balancing selection dominance to maintain MHC diversity. Great divergence at neutral or adaptive markers showed that moderate genetic differentiation had occurred in rhesus macaque populations in western Sichuan, China, due to the habitat fragmentation caused by long-term geographic barriers and human activity. The Heishui population should be paid more attention for its lowest level of genetic diversity and relatively great divergence from others.

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.

MHC class II DQB diversity in the Japanese black bear, Ursus thibetanus japonicus

Background

The major histocompatibility complex (MHC) genes are one of the most important genetic systems in the vertebrate immune response. The diversity of MHC genes may directly influence the survival of individuals against infectious disease. However, there has been no investigation of MHC diversity in the Asiatic black bear (Ursus thibetanus). Here, we analyzed 270-bp nucleotide sequences of the entire exon 2 region of the MHC DQB gene by using 188 samples from the Japanese black bear (Ursus thibetanus japonicus) from 12 local populations.

Results

Among 185 of 188 samples, we identified 44 MHC variants that encoded 31 different amino acid sequences (allotypes) and one putative pseudogene. The phylogenetic analysis suggests that MHC variants detected from the Japanese black bear are derived from the DQB locus. One of the 31 DQB allotypes, Urth-DQB*01, was found to be common to all local populations. Moreover, this allotype was shared between the black bear on the Asian continent and the Japanese black bear, suggesting that Urth-DQB*01 might have been maintained in the ancestral black bear population for at least 300,000 years. Our findings, from calculating the ratio of non-synonymous to synonymous substitutions, indicate that balancing selection has maintained genetic variation of peptide-binding residues at the DQB locus of the Japanese black bear. From examination of genotype frequencies among local populations, we observed a considerably lower level of observed heterozygosity than expected.

Conclusions

The low level of observed heterozygosity suggests that genetic drift reduced DQB diversity in the Japanese black bear due to a bottleneck event at the population or species level. The decline of DQB diversity might have been accelerated by the loss of rare variants that have been maintained by negative frequency-dependent selection. Nevertheless, DQB diversity of the black bear appears to be relatively high compared with some other endangered mammalian species. This result suggests that the Japanese black bears may also retain more potential resistance against pathogens than other endangered mammalian species. To prevent further decline of potential resistance against pathogens, a conservation policy for the Japanese black bear should be designed to maintain MHC rare variants in each local population.

HLA-DQA2 and HLA-DQB2 genes are specifically expressed in human Langerhans cells and encode a new HLA class II molecule

The precise role of human epidermal Langerhans cells (LCs) in immune response is highly controversial. While studying the gene expression profile of these cells, we were intrigued to identify the HLA-DQB2 gene as potentially expressed in LCs. Despite a strong evolutionary conservation of their sequences, the concomitant expression of the poorly polymorphic HLA-DQA2/HLA-DQB2 genes, paralogous to the HLA-DQA1/HLA-DQB1 genes, has never been detected in any cell type. We confirmed by RT-PCR that the HLA-DQA2 and -DQB2 genes are both expressed in LCs, but not in monocyte-derived dendritic cells, or in blood CD1c(+) or plasmacytoid dendritic cells. The presence of the HLA-DQβ2 chain in LCs could be demonstrated by Western blotting, whereas immunofluorescence revealed its localization in early endosomes. As in the case of other HLA class II molecules, the HLA-DQα2 and -DQβ2 chains formed heterodimers that had to associate with the invariant chain to reach endosomal compartments. HLA-DQα2/β2 heterodimers were expressed at the cell surface, where they could mediate staphylococcal superantigen stimulation of T cells. Interestingly, HLA-DQα2 and HLA-DQβ1 chains formed mixed heterodimers which efficiently left the endoplasmic reticulum. These observations strongly suggest that the poorly polymorphic HLA-DQA2 and -DQB2 genes should be considered to be of immunological importance. The HLA-DQα2/β2 molecules could influence the complexity of the repertoire of Ags presented by LCs.

Characterization of the major histocompatibility complex class II DOB, DPB1, and DQB1 alleles in cynomolgus macaques of Vietnamese origin

Major histocompatibility complex (MHC) molecules play an important role in the susceptibility and/or resistance to many diseases. To gain an insight into the MHC background and to facilitate the experimental use of cynomolgus macaques, the second exon of the MhcMafa-DOB, -DPB1, and -DQB1 genes from 143 cynomolgus macaques were characterized by cloning to sequencing. A total of 16 Mafa-DOB, 16 Mafa-DPB1, and 34 Mafa-DQB1 alleles were identified, which revealed limited, moderate, and marked allelic polymorphism at DOB, DPB1, and DQB1, respectively, in a cohort of cynomolgus macaques of Vietnamese origin. In addition, 16 Mafa-DOB, 5 Mafa-DPB1, and 8 Mafa-DQB1 alleles represented novel sequences that had not been reported in earlier studies. Almost of the sequences detected at the DOB and DQB1 locus in the present study belonged to DOB*01 (100%) and DQB1*06 (62%) lineages, respectively. Interestingly, four, three, and one high-frequency alleles were detected at Mafa-DOB, -DPB1, and -DQB1, respectively, in this monkeys. The alleles with the highest frequency among these monkeys were Mafa-DOB*010102, Mafa-DPB1*13, and Mafa-DQB1*0616, and these were found in 33 (25.6%) of 129 monkeys, 32 (31.37%) of 102 monkeys, and 30 (31%) of 143 monkeys, respectively. The high-frequency alleles may represent high priority targets for additional characterization of immune function. We also carried out evolutionary and population analyses using these sequences to reveal population-specific alleles. This information will not only promote the understanding of MHC diversity and polymorphism in the cynomolgus macaque but will also increase the value of this species as a model for biomedical research.

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.

Characterization of the major histocompatibility complex class II DQB (MhcMamu-DQB1) alleles in a cohort of Chinese rhesus macaques (Macaca mulatta)

Rhesus macaques have long been used in animal models for various human diseases, the susceptibility and/or resistance to some of which have been associated with the major histocompatibilty complex (MHC). To gain insight into the MHC background and to facilitate the experimental use of Chinese rhesus macaques, the second exon of MhcMamu-DQB1 genes in 105 rhesus macaques were characterized by cloning and sequencing. A total of 37 MhcMamu-DQB1 alleles were identified, illustrating a marked allelic polymorphism at DQB1 in these monkeys. In addition to 10 alleles were novel sequences that had not been documented in earlier reports, at least 14 alleles reported in earlier studies were not detected in this study. Most of the sequences (73%) observed in this study belong to DQB1 06 (13 alleles) and DQB1 18 (14 alleles) lineages, and the rest (27%) belong to DQB1 15, DQB1 16 and DQB1 17 lineages. The most frequent allele detected among these monkeys was MhcMamu-DQB1 06111 (22%), followed by DQB1 1503 (19%); and most of the novel alleles were present at a frequency of less than 2.5%. As for individual animals, 24 of 105 (23%) were homozygous whereas 81 of 105 (77%) were heterozygous at the MhcMamu-DQB1 locus. These data indicated significant differences in MhcMamu-DQB1 allele distribution between the Chinese rhesus macaques and the previously reported rhesus macaques, which were mostly of Indian origin. This information will not only promote the understanding of rhesus macaque MHC diversity and polymorphism but will also facilitate the use of Chinese rhesus macaques in human disease studies, especially those that may be associated with HLA-DQB genes.

Flow cytometric analysis on cross-reactivity of human-specific CD monoclonal antibodies with splenocytes of Aotus nancymaae, a non-human primate model for biomedical research

The reactivity of 204 monoclonal antibodies (mAb) out of 377 commercially available antibodies collected by the animal homologue group of the HLAD8 was analyzed by single colour flow cytometry. Most of these mAb were originally developed against human cell surface molecules. Fifty-eight mAb (28%) showed reactivity with spleen cells of Aotus nancymaae, a non-human primate animal model in biomedical research. Out of these 58 mAb, 22 also showed reactivity with mononuclear cells derived from rhesus macaques and cynomolgus monkeys indicating that the epitopes recognized are evolutionary conserved between human, Old and New World monkeys. This novel panel of A. nancymaae reactive mAb will increase the potential to explore complex host-pathogen interactions in non-human primate animal models, particularly in malaria vaccine research.

A linear peptide containing minimal T- and B-cell epitopes of Plasmodium falciparum circumsporozoite protein elicits protection against transgenic sporozoite challenge

An effective malaria vaccine is needed to address the public health tragedy resulting from the high levels of morbidity and mortality caused by Plasmodium parasites. The first protective immune mechanism identified in the irradiated sporozoite vaccine, the "gold standard" for malaria preerythrocytic vaccines, was sporozoite-neutralizing antibody specific for the repeat region of the surface circumsporozoite (CS) protein. Previous phase I studies demonstrated that a branched peptide containing minimal T- and B-cell epitopes of Plasmodium falciparum CS protein elicited antirepeat antibody and CD4(+)-T-cell responses comparable to those observed in volunteers immunized with irradiated P. falciparum sporozoites. The current study compares the immunogenicity of linear versus tetrabranched peptides containing the same minimal T- and B-cell epitopes, T1BT*, comprised of a CS-derived universal Th epitope (T*) synthesized in tandem with the T1 and B repeats of P. falciparum CS protein. A simple 48-mer linear synthetic peptide was found to elicit antisporozoite antibody and gamma interferon-secreting T-cell responses comparable to the more complex tetrabranched peptides in inbred strains of mice. The linear peptide was also immunogenic in outbred nonhuman primates (Aotus nancymaae), eliciting antibody titers equivalent to those induced by tetrabranched peptides. Importantly, the 48-mer linear peptide administered in adjuvants suitable for human use elicited antibody-mediated protection against challenge with rodent malaria transgenic sporozoites expressing P. falciparum CS repeats. These findings support further evaluation of linear peptides as economical, safe, and readily produced malaria vaccines for the one-third of the world's population at risk of malaria infection.

Comparative molecular and three-dimensional analysis of the peptide–MHC II binding region in both human and Aotus MHC-DRB molecules confirms their usefulness in antimalarial vaccine development

A vaccine against malaria is desperately needed, and Aotus monkeys are highly susceptible to experimental infection with malarial parasites. A thorough analysis of this monkey's immune system molecules was thus undertaken in our institute. Cloning and sequencing, followed by three-dimensional analysis, has revealed high homology with some HLA-DRB1 molecules in terms of their peptide binding region pockets. Molecules such as HLA-DRB1*03, 11, 08, and HLA-DRB1*04 are so similar to Aotus MHC-DRB molecules that peptides identified as binding to these molecules and inducing protective immunity in these monkeys could be used in humans without further refinement, while small modifications seem to be needed for those binding to HLA-DRB1*07, HLA-DRB1*15, 16, and HLA-DRB1*10-like molecules, making this New World monkey an excellent model for tailor-made vaccine development, especially against malaria.

Sequence analysis of major histocompatibility complex class-II DQB1 (Patr-DQB1) alleles in chimpanzees by polymerase chain reaction-based methods

The major histocompatibility complex (MHC) class-II genes are described as the genes that encode the antigen-presenting molecule. In particular, functional alleles of MHC class-II genes in nonhuman primates have been analyzed as part of the study of infectious and immune-mediated diseases in animal models and as part of efforts to understand the molecular evolution of human leukocyte antigen. The polymorphisms and sequence analysis of MHC class-II genes in a large number of subjects is necessary for the group management of nonhuman primates. In the present study, we attempted to analyze the DQB1 polymorphism in the common chimpanzee (Pan troglodytes) by exon 2 sequencing. For exact typing of Patr-DQB1 alleles, we carried out polymerase chain reaction-restriction fragment length polymorphism and sequence analysis. In the genomic DNA of 25 chimpanzees, 6 Patr-DQB1 alleles, including 2 new alleles, were detected. Identification and analysis of Patr-DQB1 alleles using this method may contribute to our understanding of Patr-DQB1 allelic diversity in individual chimpanzees and should be useful in facilitating colony management of chimpanzee groups in Japan.

Reference strand conformational analysis (RSCA) is a valuable tool in identifying MHC-DRB sequences in three species of Aotus monkeys

The Aotus monkey has been of great value in the pre-clinical study of malaria vaccine candidates. Several components of this primate's immune system have been studied and they display great similarity to their human counterparts. Cloning and sequencing studies have revealed extensive sequence polymorphisms in Aotus MHC-DRB with very high similarities to several human allelic lineages, grouping at least nine distinct MHC-DRB lineages. As the efficacy of peptide vaccines in this animal model may be strongly influenced by exon 2 MHC-DRB polymorphism, the availability of a reliable and rapid MHC-DRB typing method for three species of Aotus (Aotus nancymaae, Aotus vociferans and Aotus nigriceps) is necessary. Reference strand conformational analysis (RSCA) was used here for differentiating the distinctive Aotus MHC-DRB sequences' mobility using five fluorescently labelled references proved to be very useful for resolving closely related sequences, establishing the number of sequences transcribed in a particular monkey and their identity. The RSCA method's reliability in terms of identifying Aotus MHC-DRB sequences will facilitate evaluating individual responsiveness to vaccines and prompt studies associating susceptibility/resistance to infectious agents or auto-immune disease, for which Aotus monkeys may be considered to be an appropriate animal model.

Comparative genetics of MHC polymorphisms in different primate species: duplications and deletions

Gene products of the major histocompatibility complex (MHC) play a crucial role in the activation of adaptive (antigen-dependent) immune responses. In this paper similarities and dissimilarities among the MHCs of different primate species and their functional implications are reviewed. The human HLA system represents the most thoroughly investigated MHC of any contemporary living primate species, and so it will serve as a reference.

Identification of five different IGHV gene families in owl monkeys (Aotus nancymaae)

In order to characterize immunoglobulin heavy-chain variable (IGHV) genes in Aotus nancymaae monkeys, different mRNAs encoded by five IGHV families in this non-human primate were molecularly analysed considering their paramount importance in antibody production in an immune response. This study reports gene products exhibiting 91% amino acid similarity with IGHV1, IGHV2, IGHV3, IGHV4 and IGHV7 human IGHV families. Our analyses suggest that the IGHV gene has several conserved characteristics in humans and A. nancymaae. Several amino acid residues that are highly conserved in all family members described in humans were also present in these families in A. nancymaae. Antibody diversity in these families has remained the same since divergence of both species. Our study continues to provide evidence supporting the use of A. nancymaae monkey as an animal model for studying antibody response.

Gamma interferon levels and antibody production induced by two PvMSP-1 recombinant polypeptides are associated with protective immunity against P. vivax in Aotus monkeys

Effector mechanisms responsible for providing protective immunity against Plasmodium vivax (Pv) infection were examined in Aotus monkeys vaccinated with two Pv Merozoite Surface Protein-1 (PvMSP-1) recombinant polypeptides that had previously been shown to protect vaccines against parasite challenge. Vaccine efficacy was reproducible in this trial, showing that one out of the five monkeys immunised with the recombinant protein mixture was partially protected while three others controlled parasitaemia. Antibodies reactive to the parasite's native proteins, the recombinant polypeptides and peptides spanning both recombinant fragments were detected in most vaccinees. Despite substantial Peripheral Blood Mononuclear Cell (PBMC) antigen-specific cellular proliferation not being detected, high rPvMSP-1(20) specific gamma interferon (IFN-gamma) production was found in the three animals that controlled parasitaemia. Altogether the results suggest that antibody titres and antigen-specific IFN-gamma production mediate protective immunity against P. vivax.

Elongating modified conserved peptides eliminates their immunogenicity and protective efficacy against P. falciparum malaria

Plasmodium falciparum malaria protein peptides were synthesised in the search for more effective routes for inducing a protective immune response against this deadly parasite and this information has been associated with such molecules' three-dimensional structure. These peptides had high red blood cell binding activity and their carboxy- and amino-terminal extremes were elongated for determining their immunogenic and protection-inducing activity against this disease in the Aotus monkey experimental model. 1H-NMR was used for analysing their three-dimensional structure; FAST ELISA, immunofluorescence antibody test, and Western blot were used for identifying their antibody inducing capacity and these previously immunised Aotus were inoculated with a highly infective P. falciparum strain to determine whether these elongated peptides were able to induce protection. This was aimed at establishing an association or correlation between long peptides' three-dimensional structure and their immunogenic and protection-inducing response in these monkeys. Peptides 20026 (25 residue), 20028 (30 residue), and 20030 (35 residues) were synthesised based on elongating the amino-terminal region of the 10022 highly immunogenic and protection-inducing modified peptide. 1H-NMR studies revealed that the first three had Classical type III beta-turn structures, different from the 20-amino acid long modified peptide 10022 which had a distorted type III beta-turn. Humoral immune response analysis showed that even when some antibodies could be generated against the parasite, none of the immunised Aotus could be protected with elongated peptides suggesting that elongating them eliminated modified peptide 10022 immunogenic and protection-inducing capacity.

Phenotypical and functional characterization of non-human primate Aotus spp. dendritic cells and their use as a tool for characterizing immune response to protein antigens

A population of cells exhibiting bona fide dendritic cell (DC) morphological and functional characteristics was obtained by treating Aotus spp. monocytes with human IL-4 and GM-CSF. Although the purity of mature DCs was relatively low IL-4/GM-CSF-treated monocytes (hereafter called Aotus spp. DCs) down-regulated CD14 and up-regulated discrete levels of CD80, MHC-Class II and CD1b molecules in response to different maturation stimuli. Aotus spp. DCs generated a potent allogeneic in vitro response evidenced in mixed lymphocyte reaction (MLR) where DCs were 2- to 10-fold more efficient than peripheral blood mononuclear cells (PBMCs). Aotus spp. DC ability to boost T-cells or priming naive T-cells in vivo was proved by vaccinating Aotus spp. with autologous DCs pulsed with tetanus toxoid (TT). A single dose of TT-pulsed DCs was sufficient to increase cellular response to TT in these experiments as assessed by lymphoproliferation and cytokine production. Since Aotus spp. represents a suitable animal model for evaluating anti-Plasmodium falciparum malaria vaccine, the results shown here suggest that using antigen-pulsed Aotus spp. DCs as vaccines might lead to identifying new prospects for malarial vaccines unidentified to date because they are being formulated in less efficient adjuvants.

Structural and functional characterisation of the Toll like receptor 9 of Aotus nancymaae, a non-human primate model for malaria vaccine development

In the absence of suitable rodent animal models for Plasmodium falciparum malaria, the efficacy testing of asexual blood-stage vaccine candidates in Aotus nancymaae represents a tool to select between different formulations before conducting expensive human clinical trials. CpG oligonucleotides (ODN) specifically promote the production of pro-inflammatory and Th1-type cytokines and they enhance the immunogenicity of co-administered antigens. Toll like receptor 9 (TLR-9) binds directly and sequence-specifically to single-stranded un-methylated CpG-DNA mediating the biological effects of CpG ODN. We cloned and functionally characterised the TLR-9 cDNA of A. nancymaae. The cDNA encompassed 3,099 bp predicted to code for 1,032 amino acid residues. Results of homology searches to human TLR-9 suggested that the receptor is 93 and 94% identical at the nucleotide and amino acid sequence levels, respectively. Stimulation of splenocytes of A. nancymaae with CpG ODN resulted in proliferative responses in all animals analysed. FACS analysis of cultures incubated with CpG ODN 2006 indicated that the B cell marker CD20 was up-regulated consistent with B cell activation. The high level of sequence conservation of Aona-TLR-9 reinforces the suitability of A. nancymaae as animal model for malaria subunit vaccine development.

Comparative analysis of CD45 proteins in primate context: owl monkeys vs humans

Transmembrane protein tyrosine phosphatase (PTPase) CD45 has been implicated in activating, differentiating and the development of different immune system cells. It regulates T-or B-cell activation during receptor-specific recognition by dephosphorylating tyrosine residues in protein kinase substrates. Aotus nancymaae, Aotus nigriceps, and Aotus vociferans CD45 nucleotide and deduced amino acid sequences are presented here, where we found 90-92% identity with the human counterpart in the nucleotide sequence and 83-86% in the amino acid sequence. Aotus CD45 alternative splicing isoforms include the same exons used in human CD45, producing several identical molecular weight nucleotide fragments. Most of the non-synonymous substitutions were found in the extracellular domain. The more conserved CD45 cytoplasmic portion has two intracellular phosphatase domains (D1 and D2) separated by a short spacer and some residues and motifs involved in signaling or molecular docking, intra- and intermolecular interactions and CD45 activity and activity regulation. All invariant residues and structural/functional motifs found in PTPases were totally conserved, suggesting that Aotus CD45 is a functional enzyme. Phylogenetic analysis has shown that the Aotus CD45 molecules are more related to the human homologs than to other reported vertebrate sequences and that the ancestral group of Aotus clade is A. vociferans. When Aotus species were compared, A. nigriceps and A. vociferans were the two most distant species, while A. nancymaae and A. nigriceps appeared to be a sister group. This could be relevant in deciding which Aotus species is to be used for studying particular immunological processes during lymphocyte activation or development.

MHC class I genes in the owl monkey: mosaic organisation, convergence and loci diversity

The MHC class I molecule plays an important role in immune response, pathogen recognition and response against vaccines and self- versus non-self-recognition. Studying MHC class I characteristics thus became a priority when dealing with Aotus to ensure its use as an animal model for biomedical research. Isolation, cloning and sequencing of exons 1-8 from 27 MHC class I alleles obtained from 13 individuals classified as belonging to three owl monkey species (A. nancymaae, A. nigriceps and A. vociferans) were carried out to establish similarities between Aotus MHC class I genes and those expressed by other New and Old World primates. Six Aotus MHC class I sequence groups (Ao-g1, Ao-g2, Ao-g3, Ao-g4, Ao-g5 and Ao-g6) weakly related to non-classical Catarrhini MHC were identified. An allelic lineage was also identified in one A. nancymaae and two A. vociferans monkeys, exhibiting a high degree of conservation, negative selection along the molecule and premature termination of the open reading frame at exon 5 (Ao-g5). These sequences' high conservation suggests that they more likely correspond to a soluble form of Aotus MHC class I molecules than to a new group of processed pseudogenes. Another group, named Ao-g6, exhibited a strong relationship with Catarrhini's classical MHC-B-C loci. Sequence evolution and variability analysis indicated that Aotus MHC class I molecules experience inter-locus gene conversion phenomena, contributing towards their high variability.

Identifying and structurally characterizing CD1b in Aotus nancymaae owl monkeys

This study reports the molecular characterization and tissue expression of the non-human Aotus nancymaae primate CD1b isoform in the search for an experimental animal model to be used in evaluating the role of non-peptide antigen-presentation molecules in the immune response to infectious agents. CD1b expression on the surface of A. nancymaae peripheral blood monocyte-derived dendritic cells, shown by flow cytometry, was made possible by using human CD1b isoform antibodies. Studying the expression of CD1b-encoded transcripts revealed this molecule's broad distribution in several tissues. The A. nancymaae CD1b transcript-encoded amino-acid sequence showed 95.5% identity with the human sequence. Such high sequence homology was reflected in the identical structural conservation of how pockets A', C' and F' and tunnel T' conforming the antigen's binding site are organized, the similar arrangement of those amino-acids interacting with the T-cell receptor (TCR) during antigen presentation, and the conservation of YQNI-motif sequence in the cytoplasmatic tail (responsible for the molecule's intracellular trafficking in humans). Comparing the structure of human CD1a and CD1b and mouse CD1d proteins with CD1b structure in A. nancymaae obtained by minimization revealed that changes in the latter molecule's alpha1 and alpha2 domains imposed a narrowing of the antigen-binding groove in A. nancymaae CD1b. The high structural similarity between A. nancymaae CD1b and that from humans presented in this study leads to A. nancymaae being proposed as a suitable experimental animal model for analyzing CD1b in vivo, mainly in bacterial and parasite infections such as tuberculosis and malaria, respectively.

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.

6746 SERA peptide analogues immunogenicity and protective efficacy against malaria is associated with short alpha helix formation: malaria protection associated with peptides alpha helix shortening

Erythrocyte high activity binding peptides (HABPs) have been identified for the Plasmodium falciparum serine repeat antigen (SERA). HABP 6746, located in this protein's 50 kDa fragment had its critical binding residues replaced by amino acids having similar mass but different charge to change their immunologic properties. This peptide analogues were used to immunize Aotus monkeys that were challenged later on with a virulent P. falciparum strain to determine their protective efficacy. A shortening in alpha helix structure was found in the immunogenic and protective ones when their secondary structure was analyzed by NMR, to correlate their structure with their immunologic properties. These data, together with results from previous studies, suggest that this shortening in HABP helical configuration may lead to better fitting with immune system molecules, rendering them immunogenic and protective and therefore making them excellent candidates for consideration as components of a subunit based multicomponent synthetic vaccine against malaria.

Alpha helix shortening in 1522 MSP-1 conserved peptide analogs is associated with immunogenicity and protection against P. falciparum malaria

1522 is a nonimmunogenic conserved high-activity binding peptide (HABP) belonging to Plasmodium falciparum MSP-1 protein N-terminal fragment. The key amino acids in binding to red blood cells (RBC) were identified and replaced by others having similar mass but different charge. Because conserved HABPs are not antigenic nor immunogenic, immunogenicity and protectivity studies were then conducted on them in the Aotus monkey. 1H-NMR studies included the lead peptide 1522 as well as the analogs 9782, 13446, 13448, and 13442 to relate their structure to biological function. All the peptides presented alpha-helical structure, with differences observed in helix location and extension. The nonprotective 1522 peptide was totally helical from the N- to the C-terminus, very similar to nonprotective 13442 and 13448 peptides whose extension was almost totally helical. The 9782 and 13446 protective peptides, however, possessed a shorter helical region where modified critical binding residues were not included. A more flexible region was generated at the C-terminus in those peptides with a shorter helical region, leading to a greater number of conformers. These data suggest that peptide flexibility results in increased interaction with immune system molecules, generating protective immunity.

Proliferative response of peripheral blood lymphocytes to mitogens in the owl monkey Aotus nancymae

The new world primate Aotus sp. has been recommended by the World Health Organization as a model for evaluation of malaria vaccine candidates, given its susceptibility to experimental infection with the human malaria parasites Plasmodium falciparum and P. vivax. The present study examined the in vitro proliferative response of peripheral blood mononuclear cells (PBMCs) isolated from Aotus monkeys, utilizing a wide range of mitogens. Results presented herein demonstrate that the in vitro proliferative response of PBMCs from the Aotus sp. is quite variable from monkey to monkey for each of the mitogens assessed. PBMCs from the Aotus monkey exhibited a delayed kinetic proliferative response and, particularly, a different sensitivity to proliferation in response to various concentrations of Phytohemagglutinin-P and favin lectins, the phorbol ester Phorbol myristate acetate and the calcium ionophore ionomycin. Altogether, our findings are consistent with the conclusion that the in vitro proliferative response of PBMCs from the Aotus differ in their activation requirements compared with PBMCs from humans.

Biomedical applications and studies of molecular evolution: a proposal for a primate genomic library resource

The anticipated completion of two of the most biomedically relevant genomes, mouse and human, within the next three years provides an unparalleled opportunity for the large-scale exploration of genome evolution. Targeted sequencing of genomic regions in a panel of primate species and comparison to reference genomes will provide critical insight into the nature of single-base pair variation, mechanisms of chromosomal rearrangement, patterns of selection, and species adaptation. Although not recognized as model "genetic organisms" because of their longevity and low fecundity, 30 of the approximately 300 primate species are targets of biomedical research. The existence of a human reference sequence and genomic primate BAC libraries greatly facilitates the recovery of genes/genomic regions of high biological interest because of an estimated maximum neutral nucleotide sequence divergence of 25%. Primate species, therefore, may be regarded as the ideal model "genomic organisms". Based on existing BAC library resources, we propose the construction of a panel of primate BAC libraries from phylogenetic anchor species for the purpose of comparative medicine as well as studies of genome evolution.

Partial characterization of the CD45 phosphatase cDNA in the owl monkey (Aotus vociferans)

CD45 is a protein tyrosine phosphatase implicated in T and B cell activation, differentiation, and development. It dephosphorylates specific tyrosine residues on its substrates, principally on the Src-family of protein tyrosine kinases, thus regulating T cell or B cell activation during the immune response. In this study, we present the partial CD45 nucleotide and deduced amino-acid sequences for the owl monkey (Aotus vociferens). There is 97% identity in the nucleotide sequence and 96% in the amino acid sequence with the human counterpart. Aotus CD45 undergoes alternative splicing on the extracelular N-terminal tail, and has several conserved features characteristic of other species. This includes the two Tyr phosphatase domains and some residues and/or motifs involved in docking of signaling molecules, intramolecular interactions, and CD45 activity and activity regulation (YINAS, GXGXXG, WPD, and YWP motifs, and the Cys residues). This suggests that the Aotus CD45 molecule is a functional enzyme and that initial lymphocyte activation in Aotus monkeys and humans is very similar. Together with previous reports from our laboratory, this work supports the contention that immune responses in Aotus are similar to those of humans, and supports the strategy for using this experimental model for studies on activation of T lymphocytes in response to specific antigens.

Double dimer peptide constructs are immunogenic and protective against Plasmodium falciparum in the experimental Aotus monkey model

Multiple antigen peptide constructs (MAPs) have been used to obtain defined multimeric peptide molecules useful in the development of possible synthetic malaria vaccines. In this context, a method was developed, named double dimer constructs (DDCs), involving the direct synthesis of a dimeric peptide with a C-terminal cysteine. A tetrameric molecule was then obtained by oxidation of sulfhydryl groups. Dimer synthesis was optimized using a Fmoc/tBu strategy, dimers were purified by HPLC, oxidized with DMSO and characterized by HPLC and MALDI-TOF-MS. The tetramers or DDCs obtained by this method were used as immunogens in the search for a possible malaria vaccine. It was found that they were immunogenic in the experimental Aotus monkey model, and were able to induce protective immunity when challenged experimentally with a highly infective Plasmodium falciparum malaria strain.

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.

New World monkey efficacy trials for malaria vaccine development: critical path or detour?

Neither GMP malaria antigens nor GMP vaccines have been compared for efficacy in monkeys and humans. It is too risky to base categorical (go/no go) development decisions on results obtained using partially characterized (non-GMP) antigens, adjuvants that are too toxic for human use or unvalidated primate models. Such practices will lead to serious errors (e.g. failure to identify and stop flawed efforts, rejection of effective vaccine strategies) and unjustifiable delays. Successful malaria vaccine development will emphasize definitive field trials in populations at risk of malaria to define and improve vaccine efficacy.

Independent origin of functional MHC class II genes in humans and New World monkeys

In previous studies, major histocompatibility complex (MHC) class II DP, DQ, and DR families of genes were characterized in different primate species mostly on the basis of their second exon sequences. Resemblances were found between Old World monkey (OWM) and New World monkey (NWM) genes and were interpreted as being the result of transspecies evolution. Subsequent analysis of intron sequences of catarrhine and platyrrhine DRB genes, however, revealed that the amplifiable genes were not, in fact, orthologous. To test other DRB genes and other families of the class II region Southern blot hybridizations were carried out with tamarin genomic DNA using probes specific for the third exons of the tamarin DQA, DQB, DPB, and DRB genes. The hybridizing bands were extracted from the gel and the third exons of the genes were amplified by PCR, cloned, and sequenced. With two exceptions, all NWM class II genes were found to group separately from the human sequences. Only the sequences of one nonfunctional DQB locus appeared to be more closely related to human genes than to other platyrrhine DQB genes. In the DRB family one gene was found that grouped with sheep and strepsirhine DRB sequences and might represent an old gene lineage. To extend the sequences to the second exon, long PCRs were performed on tamarin genomic DNA. This approach was successful for five of the ten third exon sequences. From these data, we conclude that at least the functional MHC class II genes have expanded independently in catarrhines and platyrrhines.