Chinese rhesus and cynomolgus macaques in HIV vaccine and pathogenesis research

Establishment of an immortal cynomolgus macaque fibroblast cell line for propagation of cynomolgus macaque cytomegalovirus (CyCMV)

Cynomolgus macaques are widely used as an animal model in biomedical research. We have established an immortalized cynomolgus macaque fibroblast cell line (MSF-T) by transducing primary dermal fibroblasts isolated from a 13-year-old male cynomolgus macaque with a retrovirus vector expressing human telomerase reverse transcriptase (hTERT). The MSF-T cells showed increased telomerase enzyme activity and reached over 200 in vitro passages compared to the non-transduced dermal fibroblasts, which reached senescence after 43 passages. The MSF-T cell line is free of mycoplasma contamination and is permissive to the newly identified cynomolgus macaque cytomegalovirus (CyCMV). CyCMV productively infects MSF-T cells and induces down-regulation of MHC class I expression. The MSF-T cell line will be extremely useful for the propagation of CyCMV and other cynomolgus herspesviruses in host-derived fibroblast cells, allowing for the retention of host-specific viral genes. Moreover, this cell line will be beneficial for many in vitro experiments related to this animal model.

Evaluation of cynomolgus macaque (Macaca fascicularis) endogenous retrovirus expression following simian immunodeficiency virus infection

Human endogenous retrovirus type K (HERV-K) transcripts are upregulated in the plasma of HIV-infected individuals and have been considered as targets for an HIV vaccine. We evaluated cynomolgus macaque endogenous retrovirus (CyERV) mRNA expression by RT-qPCR in PBMCs isolated from a cohort of animals previously utilized in a live attenuated SIV vaccine trial. CyERV env transcript levels decreased following vaccination (control and vaccine groups) and CyERV env and gag mRNA expression was decreased following acute SIV-infection, whereas during chronic SIV infection, CyERV transcript levels were indistinguishable from baseline. Reduced susceptibility to initial SIV infection, as measured by the number of SIV challenges required for infection, was associated with increased CyERV transcript levels in PBMCs. In vitro analysis revealed that SIV infection of purified CD4⁺ T-cells did not alter CyERV gene expression. This study represents the first evaluation of ERV expression in cynomolgus macaques following SIV infection, in an effort to assess the utility of cynomolgus macaques as an animal model to evaluate ERVs as a target for an HIV/SIV vaccine. This non-human primate model system does not recapitulate what has been observed to date in the plasma of HIV-infected humans suggesting that further investigation at the cellular level is required to elucidate the impact of HIV/SIV infection on endogenous retrovirus expression.

Genomic sequencing and characterization of cynomolgus macaque cytomegalovirus

Cytomegalovirus (CMV) infection is the most common opportunistic infection in immunosuppressed individuals, such as transplant recipients or people living with HIV/AIDS, and congenital CMV is the leading viral cause of developmental disabilities in infants. Due to the highly species-specific nature of CMV, animal models that closely recapitulate human CMV (HCMV) are of growing importance for vaccine development. Here we present the genomic sequence of a novel nonhuman primate CMV from cynomolgus macaques (Macaca fascicularis; CyCMV). CyCMV (Ottawa strain) was isolated from the urine of a healthy, captive-bred, 4-year-old cynomolgus macaque of Philippine origin, and the viral genome was sequenced using next-generation Illumina sequencing to an average of 516-fold coverage. The CyCMV genome is 218,041 bp in length, with 49.5% G+C content and 84% protein-coding density. We have identified 262 putative open reading frames (ORFs) with an average coding length of 789 bp. The genomic organization of CyCMV is largely colinear with that of rhesus macaque CMV (RhCMV). Of the 262 CyCMV ORFs, 137 are homologous to HCMV genes, 243 are homologous to RhCMV 68.1, and 200 are homologous to RhCMV 180.92. CyCMV encodes four ORFs that are not present in RhCMV strain 68.1 or 180.92 but have homologies with HCMV (UL30, UL74A, UL126, and UL146). Similar to HCMV, CyCMV does not produce the RhCMV-specific viral homologue of cyclooxygenase-2. This newly characterized CMV may provide a novel model in which to study CMV biology and HCMV vaccine development.

Assessing natural introgression in 2 biomedical model species, the rhesus macaque (Macaca mulatta) and the long-tailed macaque (Macaca fascicularis)

Rhesus macaque (Macaca mulatta) and long-tailed macaque (Macaca fascicularis) are the 2 most commonly used primate model species in biomedical sciences. Although morphological studies have revealed a weak hybridization at the interspecific contact zone, in the north of Indochina, a molecular study has suggested an ancient introgression from rhesus to long-tailed macaque into the Indo-Chinese peninsula. However, the gene flow between these 2 taxa has never been quantified using genetic data and theoretical models. In this study, we have examined genetic variation within and between the parapatric Chinese rhesus macaque and Indo-Chinese long-tailed macaque populations, using 13 autosomal, 5 sex-linked microsatellite loci and mitochondrial DNA sequence data. From these data, we assessed genetic structure and estimated gene flow using a Bayesian clustering approach and the "Isolation with Migration" model. Our results reveal a weak interspecific genetic differentiation at both autosomal and sex-linked loci, suggesting large population sizes and/or gene flow between populations. According to the Bayesian clustering, Chinese rhesus macaque is a highly homogeneous gene pool that contributes strongly to the current Indo-Chinese long-tailed macaque genetic makeup, whether or not current admixture is assumed. Coalescent simulations, which integrated the characteristics of the loci, pointed out 1) a higher effective population size in rhesus macaque, 2) no mitochondrial gene flow, and 3) unilateral and male-mediated nuclear gene flow of approximately 10 migrants per generation from rhesus to long-tailed macaque. These patterns of genetic structure and gene flow suggest extensive ancient introgression from Chinese rhesus macaque into the Indo-Chinese long-tailed macaque population.

Factors shaping genetic variation in the MHC of natural non-human primate populations

Across a large distribution range, population-specific factors as well as pathogen-mediated selection may shape species genetic diversity in the major histocompatibility complex (MHC). We have studied genetic diversity and population differentiation in the MHC region of the Southeast Asian cynomolgus macaque (Macaca fascicularis fascicularis), a species with large and discontinuous range, in order to investigate the role of demography vs selection. Genetic variation was assessed at seven MHC microsatellites on 272 individuals from five populations (Indochina, Java, Borneo, Philippines, and Mauritius). A high genetic diversity was observed in all populations and the Philippines but also the Mauritius populations were the most genetically differentiated. The strength and extent of linkage disequilibrium (LD) (up to 4 Mb) varies across populations mainly because of demographic factors. In Indochina, the complete lack of LD could be the signature of ancient hybridization between cynomolgus and rhesus macaques in the Indochinese peninsula. With the additional support of seven autosomal microsatellites, tests for outlier loci based on intrapopulation diversity and interpopulation differentiation (using F-statistic) allowed to dissociate demographic from selective histories: (i) demographic history may itself explain levels of MHC variability in the Mauritius populations and (ii) positive selection could be responsible for the Philippines population differentiation, especially in the MHC class II region. Among various pathogens, Plasmodium knowlesi and Plasmodium coatneyi are two likely candidates to explain the higher frequency of some MHC haplotypes. Indeed, literature describes low parasitemia in the Philippines individuals, contrasting with fatal infections provoked by these parasites in other cynomolgus macaque populations.