Determination of genetic status in a closed colony of rhesus monkeys (Macaca mulatta)

An analysis of risk factors for spontaneously occurring type 2 diabetes mellitus in rhesus macaques (Macaca mulatta)

BACKGROUND

Type 2 Diabetes Mellitus (T2D) is a chronic disease with a high prevalence worldwide. Human literature suggests factors beyond well-known risk factors (e.g., age, body mass index) for T2D: cytomegalovirus serostatus, season of birth, maternal age, birth weight, and depression. Nothing is known, however, about whether these variables are influential in primate models of T2D.

METHODS

Using a retrospective methodology, we identified 22 cases of spontaneously occurring T2D among rhesus monkeys at our facility. A control sample of n = 1199 was identified.

RESULTS

Animals born to mothers that were ≤5.5 years of age, and animals that showed heightened Activity and Emotionality in response to brief separation in infancy, had a greater risk for development of T2D in adulthood.

CONCLUSIONS

Knowledge of additional risk factors for T2D could help colony managers better identify at-risk animals and enable diabetes researchers to select animals that might be more responsive to their manipulations.

Rhesus macaque social functioning is paternally, but not maternally, inherited by sons: potential implications for autism

BACKGROUND

Quantitative autistic traits are common, heritable, and continuously distributed across the general human population. Patterns of autistic traits within families suggest that more complex mechanisms than simple Mendelian inheritance-in particular, parent of origin effects-may be involved. The ideal strategy for ascertaining parent of origin effects is by half-sibling analysis, where half-siblings share one, but not both, parents and each individual belongs to a unique combination of paternal and maternal half-siblings. While this family structure is rare in humans, many of our primate relatives, including rhesus macaques, have promiscuous breeding systems that consistently produce paternal and maternal half-siblings for a given index animal. Rhesus macaques, like humans, also exhibit pronounced variation in social functioning.

METHODS

Here we assessed differential paternal versus maternal inheritance of social functioning in male rhesus macaque offspring (N = 407) using ethological observations and ratings on a reverse-translated quantitative autistic trait measurement scale. Restricted Maximum Likelihood mixed models with unbounded variance estimates were used to estimate the variance components needed to calculate the genetic contribution of parents as the proportion of phenotypic variance (σ2P) between sons that could uniquely be attributed to their shared genetics (σ2g), expressed as σ2g/σ2P (or the proportion of phenotypic variance attributable to genetic variance), as well as narrow sense heritability (h2).

RESULTS

Genetic contributions and heritability estimates were strong and highly significant for sons who shared a father but weak and non-significant for sons who shared a mother. Importantly, these findings were detected using the same scores from the same sons in the same analysis, confirmed when paternal and maternal half-siblings were analyzed separately, and observed with two methodologically distinct behavioral measures. Finally, genetic contributions were similar for full-siblings versus half-siblings that shared only a father, further supporting a selective paternal inheritance effect.

LIMITATIONS

These data are correlational by nature. A larger sample that includes female subjects, enables deeper pedigree assessments, and supports molecular genetic analyses is warranted.

CONCLUSIONS

Rhesus macaque social functioning may be paternally, but not maternally, inherited by sons. With continued investigation, this approach may yield important insights into sex differences in autism's genetic liability.

The relationship of maternal rank, 5-HTTLPR genotype, and MAOA-LPR genotype to temperament in infant rhesus monkeys (Macaca mulatta)

Temperament is a construct whose manifestations are quantifiable from an early age, and whose origins have been proposed as "biological." Our goal was to determine whether maternal rank and infant genotype are associated with five measures of temperament in 3- to 4-month old rhesus monkeys (Macaca mulatta), all of whom were born and reared by their mothers in large, outdoor, half-acre cages. Maternal rank was defined as the proportion of animals outranked by each female, and the two genes of interest to us were monoamine oxidase and serotonin transporter, both of which are polymorphic in their promoter regions (MAOA-LPR and 5-HTTLPR, respectively), with one allele of each gene considered a "plasticity" allele, conferring increased sensitivity to environmental events. Our large sample size (n = 2014-3140) enabled us to examine the effects of individual genotypes rather than combining genotypes as is often done. Rank was positively associated with Confident temperament, but only for animals with the 5-repeat allele for MAOA-LPR. Rank had no other effect on temperament. In contrast, genotype had many different effects, with 5-HTTLPR associated with behavioral inhibition, and MAOA-LPR associated with ratings-based measures of temperament. We also examined the joint effect of the two genotypes and found some evidence for a dose-response: animals with the plasticity alleles for both genes were more likely to be behaviorally inhibited. Our results suggest phenotypic differences between animals possessing alleles for MAOA-LPR that show functional equivalence based on in vitro tests, and our data for 5-HTTLPR revealed differences between short/short homozygotes and long/short heterozygotes, strongly suggesting that combining genotypes for statistical analysis should be avoided if possible. Our analysis also provides evidence of sex differences in temperament, and, to our knowledge, the only evidence of differences in temperament based on specific pathogen-free status. We suggest several directions for future research.

No postcopulatory selection against MHC-homozygous offspring: Evidence from a pedigreed captive rhesus macaque colony

The heterozygosity status of polymorphic elements of the immune system, such as the major histocompatibility complex (MHC), is known to increase the potential to cope with a wider variety of pathogens. Pre- and postcopulatory processes may regulate MHC heterozygosity. In a population where mating occurs among individuals that share identical MHC haplotypes, postcopulatory selection may disfavour homozygous offspring or ones with two MHC haplotypes identical to its mother. We tested these ideas by determining the incidence of MHC-heterozygous and MHC-homozygous individuals in a pedigreed, partially consanguineous captive rhesus monkey colony. Bayesian statistics showed that when parents share MHC haplotypes, the distribution of MHC-heterozygous and MHC-homozygous individuals significantly fitted the expected Mendelian distribution, both for the complete MHC haplotypes, and for MHC class I or II genes separately. Altogether, we found in this captive colony no evidence for postcopulatory selection against MHC-homozygous individuals. However, the distribution of paternally and maternally inherited MHC haplotypes tended to differ significantly from expected. Individuals with two MHC haplotypes identical to their mother were underrepresented and offspring with MHC haplotypes identical to their father tended to be overrepresented. This suggests that postcopulatory processes affect MHC haplotype combination in offspring, but do not prevent low MHC heterozygosity.

Primate models in organ transplantation

Large animal models have long served as the proving grounds for advances in transplantation, bridging the gap between inbred mouse experimentation and human clinical trials. Although a variety of species have been and continue to be used, the emergence of highly targeted biologic- and antibody-based therapies has required models to have a high degree of homology with humans. Thus, the nonhuman primate has become the model of choice in many settings. This article will provide an overview of nonhuman primate models of transplantation. Issues of primate genetics and care will be introduced, and a brief overview of technical aspects for various transplant models will be discussed. Finally, several prominent immunosuppressive and tolerance strategies used in primates will be reviewed.

Microsatellite variation in two subspecies of cynomolgus monkeys (Macaca fascicularis)

To estimate the genetic variability of two subspecies of cynomolgus monkeys (Macaca fascicularis fascicularis and M. f. aurea) using microsatellite markers, 26 microsatellite markers were selected from previous reports. Seventeen markers showed high polymorphism in a subset of monkeys and were used for the assessment of genetic diversity in the larger sample. The effective number of alleles, the polymorphism information content (PIC) and the expected heterozygosity of M. f. aurea monkeys were all statistically significantly higher than those of M. f. fascicularis monkeys (P < 0.05), suggesting the M. f. aurea monkeys had a higher degree of genetic variation than the M. f. fascicularis monkeys. Substantial differences in allele distribution were also detected between the two subspecies of cynomolgus monkeys. Private alleles restricted to the M. f. fascicularis or the M. f. aurea monkeys were found throughout the selected 17 loci. These private alleles may allow the discrimination of the two subspecies of cynomolgus monkeys. The selected markers could also be used to estimate the genetic variation for other subspecies of cynomolgus monkeys. Further work using additional animals obtained from native or independent sources will be important for a more complete understanding of the genetic differences between these two subgroups.

Nonhuman primate transplant models finally evolve: detailed immunogenetic analysis creates new models and strengthens the old

Nonhuman primate (NHP) models play a critical role in the translation of novel therapies for transplantation to the clinic. However, although MHC disparity significantly affects the outcome of transplantation, until recently, experiments using NHP models were performed without the ability to rigorously control the degree of MHC disparity in transplant cohorts. In this review, we discuss several key technical breakthroughs in the field, which have finally enabled detailed immunogenetic data to be incorporated into NHP transplantation studies. These advances have created a new gold-standard for NHP transplantation research, which incorporates detailed information regarding the degree of relatedness and the degree of MHC haplotype disparity between transplant pairs and the precise MHC alleles that both donors and recipients express. The adoption of this new standard promises to increase the rigor of NHP transplantation studies and to ensure that these experiments are optimally translatable to patient care.

Disposition of antimony in rhesus monkeys infected with Leishmania braziliensis and treated with meglumine antimoniate

Antimony (Sb) disposition and toxicity was evaluated in Leishmania braziliensis-infected monkeys (Macaca mulatta) treated with a 21-d course of low (LOW) or standard (STD) meglumine antimoniate (MA) dosage regimens (5 or 20 mg Sb(V)/kg body weight/d im). Antimony levels in biological matrices were determined by inductively coupled plasma mass spectrometry (ICPMS), while on-line ion chromatography coupled to ICPMS was used to separate and quantify Sb species in plasma. Nadir Sb levels rose steadily from 19.6 ± 4 and 65.1 ± 17.4 ng/g, 24 h after the first injection, up to 27.4 ± 5.8 and 95.7 ± 6.6 ng/g, 24 h after the 21st dose in LOW and SDT groups, respectively. Subsequently, Sb plasma levels gradually declined with a terminal elimination phase half-life of 35.8 d. Antimony speciation in plasma on posttreatment days 1-9 indicated that as total Sb levels declined, proportion of Sb(V) remained nearly constant (11-20%), while proportion of Sb(III) rose from 5% (d 1) to 50% (d 9). Plasma [Sb]/erythrocyte [Sb] ratio was >1 until 12 h after dosing and reversed thereafter. Tissue Sb concentrations (posttreatment days 55 and 95) were as follows: >1000 ng/g in thyroid, nails, liver, gall bladder and spleen; >200 and <1000 ng/g in lymph nodes, kidneys, adrenals, bones, skeletal muscles, heart and skin; and <200 ng/g in various brain structures, thymus, stomach, colon, pancreas. and teeth. Results from this study are therefore consistent with view that Sb(V) is reduced to Sb(III), the active form, within cells from where it is slowly eliminated. Localization of Sb active forms in the thyroid gland and liver and the pathophysiological consequences of marked Sb accumulation in these tissues warrant further studies.

An MHC-defined primate model reveals significant rejection of bone marrow after mixed chimerism induction despite full MHC matching

In murine models, mixed hematopoietic chimerism induction leads to robust immune tolerance. However, translation to primates and to patients has been difficult. In this study, we used a novel MHC-defined rhesus macaque model to examine the impact of MHC matching on the stability of costimulation blockade-/sirolimus-mediated chimerism, and to probe possible mechanisms of bone marrow rejection after nonmyeloablative transplant. Using busulfan-based pretransplant preparation and maintenance immunosuppression with sirolimus, as well as CD28 and CD154 blockade, all recipients demonstrated donor engraftment after transplant. However, the mixed chimerism that resulted was compartmentalized, with recipients demonstrating significantly higher whole blood chimerism compared to T cell chimerism. Thus, the vast majority of T cells presenting posttransplant were recipient-rather than donor-derived. Surprisingly, even in MHC-matched transplants, rejection of donor hematopoiesis predominated after immunosuppression withdrawal. Weaning of immunosuppression was associated with a surge of antigen-experienced T cells, and transplant rejection was associated with the acquisition of donor-directed T cell alloreactivity. These results suggest that a reservoir of alloreactive cells was present despite prior costimulation blockade and sirolimus, and that the post-immunosuppression lymphocytic rebound may have lead to a phenotypic shift in these recipient T cells towards an activated, antigen-experienced phenotype, and ultimately, to transplant rejection.

Genetic characterization of specific pathogen-free rhesus macaque (Macaca mulatta) populations at the California National Primate Research Center (CNPRC)

A study based on 14 STRs was conducted to understand intergenerational genetic changes that have occurred within the California National Primate Research Center's (CNPRC) regular specific pathogen-free (SPF) and super-SPF captive rhesus macaque populations relative to their conventional founders. Intergenerational genetic drift has caused age cohorts of each study population, especially within the conventional population, to become increasingly differentiated from each other and from their founders. Although there is still only minimal stratification between the conventional population and either of the two SPF populations, separate derivation of the regular and super-SPF animals from their conventional founders has caused the two SPF populations to remain marginally different from each other. The regular SPF and, especially, the super-SPF populations have been influenced by the effects of differential ancestry, sampling, and lost rare alleles, causing a substantial degree of genetic divergence between these subpopulations. The country of origin of founders is the principal determinant of the MHC haplotype composition of the SPF stocks at the CNPRC. Selection of SPF colony breeders bearing desired genotypes of Mamu-A*01 or -B*01 has not affected the overall genetic heterogeneity of the conventional and the SPF research stocks.Because misclassifying the ancestry of research stocks can undermine experimental outcomes by excluding animals with regional-specific genotypes or phenotypes of importance, understanding founder/descendent genetic relationships is crucial for investigating candidate genes with distinct geographic origins. Together with demographic management, population genetic assessments of SPF colonies can curtail excessive phenotypic variation among the study stocks and facilitate successful production goals.

Development of an integrative database with 499 novel microsatellite markers for Macaca fascicularis

BACKGROUND

Cynomolgus macaques (Macaca fascicularis) are a valuable resource for linkage studies of genetic disorders, but their microsatellite markers are not sufficient. In genetic studies, a prerequisite for mapping genes is development of a genome-wide set of microsatellite markers in target organisms. A whole genome sequence and its annotation also facilitate identification of markers for causative mutations. The aim of this study is to establish hundreds of microsatellite markers and to develop an integrative cynomolgus macaque genome database with a variety of datasets including marker and gene information that will be useful for further genetic analyses in this species.

RESULTS

We investigated the level of polymorphisms in cynomolgus monkeys for 671 microsatellite markers that are covered by our established Bacterial Artificial Chromosome (BAC) clones. Four hundred and ninety-nine (74.4%) of the markers were found to be polymorphic using standard PCR analysis. The average number of alleles and average expected heterozygosity at these polymorphic loci in ten cynomolgus macaques were 8.20 and 0.75, respectively.

CONCLUSION

BAC clones and novel microsatellite markers were assigned to the rhesus genome sequence and linked with our cynomolgus macaque cDNA database (QFbase). Our novel microsatellite marker set and genomic database will be valuable integrative resources in analyzing genetic disorders in cynomolgus macaques.

Frequency of the major histocompatibility complex Mamu-A*01 allele in a closed breeding colony of rhesus monkey (Macaca mulatta) from Brazil

BACKGROUND

Rhesus monkeys are relevant models for human diseases. The simian immunodeficiency virus (SIV) infection is an useful macaque model for assessing human immunodeficiency virus (HIV) vaccine strategies. Susceptibility and resistance to viruses have been associated with particular major histocompatibility complex (MHC) molecules. Several epitopes in the HIV structural and non-structural protein restricted by distinct MHC class I haplotypes are important targets for human cytotoxic T lymphocytes, which mediate protection against SIVmac infection. Mamu-A*01, for example, is a MHC class I molecule of rhesus monkeys that presents a peptide from SIV gag protein.

METHODS

Our study determined the frequency of Mamu-A*01 in a closed colony of rhesus monkeys from Brazil by polymerase chain reaction.

RESULTS

A high frequency of the allele was found in the study colony.

CONCLUSION

This colony provides a significant source of A*01-positive animals to investigators.

INTERSPECIES HYBRIDIZATION AND THE STRATIFICATION OF NUCLEAR GENETIC VARIATION OF RHESUS (MACACA MULATTA) AND LONG-TAILED MACAQUES (MACACA FASCICULARIS)

Genotypes for 13 short tandem repeats (STRs) were used to assess the genetic diversity within and differentiation among populations of rhesus macaques (Macaca mulatta) from mainland Asia and long-tailed macaques (M. fascicularis) from mainland and insular Southeast Asia. These animals were either recently captured in the wild or derived from wild-caught founders maintained in captivity for biomedical research.A large number of alleles is shared between the two macaque species but a significant genetic division between them persists. This distinction is more clear-cut among populations that are not, or are unlikely to have recently been, geographically contiguous. Our results suggest there has been significant interspecies nuclear gene flow between rhesus macaques and long-tailed macaques on the mainland. Comparisons of mainland and island populations of long-tailed macaques reflect marked genetic subdivisions due to barriers to migration. Geographic isolation has restricted gene flow, allowing island populations to become subdivided and genetically differentiated. Indonesian long-tailed macaques show evidence of long-term separation and genetic isolation from the mainland populations, while long-tailed macaques from the Philippines and Mauritius both display evidence of founder effects and subsequent isolation, with the impact from genetic drift being more profound in the latter.

Pinpointing a selective sweep to the chimpanzee MHC class I region by comparative genomics

Chimpanzees experienced a reduction of the allelic repertoire at the major histocompatibility complex (MHC) class I A and B loci, which may have been caused by a retrovirus belonging to the simian immunodeficiency virus (SIV) family. Extended MHC haplotypes were defined in a pedigreed chimpanzee colony. Comparison of genetic variation at microsatellite markers mapping inside and outside the Mhc region was carried out in humans and chimpanzees to investigate the genomic extent of the repertoire reduction. Multilocus demographic analyses underscored that chimpanzees indeed experienced a selective sweep that mainly targeted the chromosomal segment carrying the Mhc class I region. Probably due to genetic linkage, the sweep also affected other polymorphic loci, mapping in the close vicinity of the Mhc class I region genes. Nevertheless, although the allelic repertoire at particular Mhc class I and II loci appears to be limited, naturally occurring recombination events allowed the establishment of haplotype diversity after the sweep. However, recombination did not have sufficient time to erase the signal of the selective sweep.

Simian immunodeficiency virus-induced CD4+ T cell deficits in cytokine secretion profile are dependent on monkey origin

Facets of the immune response early after human immunodeficiency virus (HIV) infection influence the course of disease. In the simian immunodeficiency virus (SIV)-rhesus monkey system, a global dysfunction of CD4(+) T cell cytokine secretion was reported to develop early after infection [McKay PF, Barouch DH, Schmitz JE, Veazey RS, Gorgone DA, Lifton MA, Williams KC, and Letvin NL: J Virol 2003;77:4695-4702]. Because differences have been found in SIV pathogenesis depending on the origin of the monkeys, we investigated the correlation between animal background, defined by country of origin (India or China), and circulating T cell cytokine secretion as well as cycling ability within the first 3 mo of SIV infection. An early loss of CD4(+) T cells that produce interferon (IFN)-gamma and interleukin (IL)-2, those that produce IFN-gamma but not tumor necrosis factor (TNF)-alpha, as well as those that do not express IFN-gamma but can express IL-2 or TNF-alpha, was observed in animals of Indian, but not of Chinese, origin after SIV infection. After infection CD4(+) T cells in Chinese macaques developed an increased proliferating pool of T cells compared with Indian animals. These data reveal host diversity in the global effects of SIV infection on functional subsets of immune cells, which can add to a better understanding of differences observed in populations from diverse ethnic origins.

Highly polymorphic STR marker amplified with human DYS389 primers in Japanese macaques (Macaca fuscata)

Amplification products from male and female Japanese macaques were obtained by PCR with human Y-chromosomal DYS389 primers. These products were examined by electrophoresis and sequence analysis. The PCR products from the 12 Japanese macaques tested had different band patterns on an electrophoretogram. Sequence analysis of the products revealed that the high polymorphism originated from variable numbers of repeats of two separate CTAT sequences. The sequences of the Japanese macaque products were similar to those of the reference human DYS389 sequence. However, variable CTGT repeats and a difference in the second forward primer binding site yielded two products in human males, DYS389I and DYS389II, which do not exist in Japanese macaques. Our results suggest that the human DYS389 primers may be a potential tool not only for distinguishing between human and Japanese macaque DNA samples, but also for identifying individual macaques, because of the highly polymorphic alleles.

Development of a microsatellite marker set applicable to genome-wide screening of cynomolgus monkeys (Macaca fascicularis)

To develop a microsatellite marker set applicable to genome-wide screening of cynomolgus monkeys (Macaca fascicularis), 148 microsatellite markers were selected from the human genome database. The polymorphisms and inheritance of PCR products were determined by screening twenty unrelated monkeys and by analysis of three families, respectively. As a result, 106 primers (72%) gave PCR products of the size expected for humans and rhesus monkeys. Among these products, polymorphism and single-gene inheritance in cynomolgus monkeys was observed for 66 markers (62%). The average number of alleles at the 66 polymorphic loci was 5.86 (range 2-10), and average heterozygosity was 0.63 (range 0.10-0.88). This is the first report of microsatellite markers for cynomolgus monkeys. Chromosomal mapping of these markers is now in progress.

Microsatellite markers for standardized genetic management of captive colonies of rhesus macaques (Macaca mulatta)

To preserve genetic variability and minimize genetic subdivision among captive Macaca mulatta at each of the U.S. National Institutes of Health (NIH)-sponsored regional research colonies, the genetic structure of each colony must be characterized. To compare population genetic and demographic parameters across colonies and generations, one standard panel of highly informative genetic markers is required. We assembled a core marker set of four multiplex polymerase chain reaction (PCR) panels comprising 15 autosomal short tandem repeat (STR) loci with high information content selected from existing panels of well-characterized markers that are currently used for parentage assessment and genetic management of rhesus macaques. We then assessed the effectiveness of these loci for providing high probabilities of individual identification and parentage resolution, and for estimating population genetic parameters that are useful for genetic management.

Leishmania infantum-induced primary and challenge infections in rhesus monkeys (Macaca mulatta): a primate model for visceral leishmaniasis

Visceral leishmaniasis (VL) was experimentally induced in rhesus macaques (Macaca mulatta) by intravenously inoculating 2 x 10(7)amastigotes/kg of body weight of Leishmania infantum. The macaques developed a systemic disease showing characteristic features of human VL such as fever, diarrhoea, body weight loss, anaemia, hypergammaglobulinaemia and transient lymphocytosis, as well as lymph node, liver and/or spleen enlargement. Nine weeks after infection, one primate showed pronounced weight loss, became moribund and was euthanized. The necropsy findings included granulomas composed of parasite-containing macrophages, lymphocytes and plasma cells in the liver, spleen and lymph nodes. The remaining macaques had a sustained course of infection but developed a mild-to-moderate illness that subsequently showed evidence of self-cure. Of note, pathological findings included a typical cell-mediated immunity-induced granulomatous reaction that had an effect on the control of parasite replication. All infected monkeys responded with increased production of anti-Leishmania-specific IgG antibodies. Despite the fact that clinical resistance to L. infantum was not consistently associated with a parasite-specific cell-mediated immune response, drug-cured macaques from the primary infection acquired immunity to homologous re-infection. These findings point to the feasibility of using the L. infantum macaque model for pre-clinical evaluation of novel chemotherapeutics or vaccine candidates for human VL.

Susceptibility of Chinese rhesus monkeys to SIV infection

The use of China-derived monkeys in AIDS research has been limited by reports of reduced susceptibility to SIV. We performed a serial passage of SIV in Chinese macaques, which resulted in a viral stock capable of inducing simian AIDS and high levels of replication in these animals. Similar to HIV in humans, SIV pathogenesis in non-human primates is not limited by geographical origin. Chinese macaques are useful in pathogenesis, vaccine, and therapeutic studies in AIDS.