Serological Evidence of Filovirus Infection in Nonhuman Primates in Zambia.

Ebolaviruses and marburgviruses are filoviruses that are known to cause severe hemorrhagic fever in humans and nonhuman primates (NHPs). While some bat species are suspected to be natural reservoirs of these filoviruses, wild NHPs often act as intermediate hosts for viral transmission to humans. Using an enzyme-linked immunosorbent assay, we screened two NHP species, wild baboons and vervet monkeys captured in Zambia, for their serum IgG antibodies specific to the envelope glycoproteins of filoviruses. From 243 samples tested, 39 NHPs (16%) were found to be seropositive either for ebolaviruses or marburgviruses with endpoint antibody titers ranging from 100 to 25,600. Interestingly, antibodies reactive to Reston virus, which is found only in Asia, were detected in both NHP species. There was a significant difference in the seropositivity for the marburgvirus antigen between the two NHP species, with baboons having a higher positive rate. These results suggest that wild NHPs in Zambia might be nonlethally exposed to these filoviruses, and this emphasizes the need for continuous monitoring of filovirus infection in wild animals to better understand the ecology of filoviruses and to assess potential risks of outbreaks in humans in previously nonendemic countries.

Rabies among animals in Saudi Arabia.

BACKGROUND: Rabies is a fatal viral disease that continues to threaten human and animal health in endemic countries. Rabies is endemic in animals in the Arabian Peninsula. Although Saudi Arabia is the largest country on the Peninsula, little has been reported in the country about rabies situation. METHODS: A total of 199 animals suspected of rabies from 2010 to 2017, were examined for rabies infection using the Direct Fluorescent Antibody Test (DFAT). RESULTS: There were 158 (79.4%) positive cases of rabies of the examined animals, Most positive cases were found in Al-Qassim (63), Eastern region (48), Riyadh (25) and Al-Madina (10). Rabies was diagnosed in Procavia capensis and monkeys (Papio hamadryas hamadryas) in Saudi Arabia for the first time. In addition, infected livestock, especially camels, sheep and goat that pose a risk to veterinarians and farmers which increases the risk of potential zoonosis of rabies in Saudi Arabia. CONCLUSION: These findings indicate that Rabies in Saudi Arabia remain a public health problem and dogs and camels are the main reservoir and continue to present health risks for both human and animals throughout the country, underscoring the importance of applying rabies control measures to animals and humans.

Subclinical Infection of Macaques and Baboons with A Baboon Simarterivirus.

Simarteriviruses (Arteriviridae: Simarterivirinae) are commonly found at high titers in the blood of African monkeys but do not cause overt disease in these hosts. In contrast, simarteriviruses cause severe disease in Asian macaques upon accidental or experimental transmission. Here, we sought to better understand the host-dependent drivers of simarterivirus pathogenesis by infecting olive baboons (n = 4) and rhesus monkeys (n = 4) with the simarterivirus Southwest baboon virus 1 (SWBV-1). Surprisingly, none of the animals in our study showed signs of disease following SWBV-1 inoculation. Three animals (two rhesus monkeys and one olive baboon) became infected and sustained high levels of SWBV-1 viremia for the duration of the study. The course of SWBV-1 infection was highly predictable: plasma viremia peaked between 1 × 107 and 1 × 108 vRNA copies/mL at 3⁻10 days post-inoculation, which was followed by a relative nadir and then establishment of a stable set-point between 1 × 106 and 1 × 107 vRNA copies/mL for the remainder of the study (56 days). We characterized cellular and antibody responses to SWBV-1 infection in these animals, demonstrating that macaques and baboons mount similar responses to SWBV-1 infection, yet these responses are ineffective at clearing SWBV-1 infection. SWBV-1 sequencing revealed the accumulation of non-synonymous mutations in a region of the genome that corresponds to an immunodominant epitope in the simarterivirus major envelope glycoprotein GP5, which likely contribute to viral persistence by enabling escape from host antibodies.

Baboon CD8 T cells suppress SIVmac infection in CD4 T cells through contact-dependent production of MIP-1α, MIP-1ß, and RANTES.

Simian immunodeficiency virus (SIV) infection in rhesus macaques is often characterized by high viremia and CD4 T cell depletion. By contrast, SIV infection in African nonhuman primate natural hosts is typically nonpathogenic despite active viral replication. Baboons are abundant in Africa and have a geographical distribution that overlaps with natural hosts, but they do not harbor SIVs. Previous work has demonstrated baboons are resistant to chronic SIV infection and/or disease in vivo but the underlying mechanisms remain unknown. Using in vitro SIVmac infections, we sought to identify SIV restriction factors in baboons by comparing observations to the pathogenic rhesus macaque model. SIVmac replicated in baboon PBMC but had delayed kinetics compared to rhesus PBMC. However, SIVmac replication in baboon and rhesus isolated CD4 cells were similar to the kinetics seen for rhesus PBMC, demonstrating intracellular restriction factors do not play a strong role in baboon inhibition of SIVmac replication. Here, we show CD8 T cells contribute to the innate SIV-suppressive activity seen in naïve baboon PBMC. As one mechanism of restriction, we identified higher production of MIP-1α, MIP-1ß, and RANTES by baboon PBMC. Contact between CD4 and CD8 T cells resulted in maximum production of these chemokines and suppression of viral replication, whereas neutralization of CCR5-binding chemokines in baboon PBMC increased viral loads. Our studies indicate baboon natural restriction of SIVmac replication is largely dependent on CD4-extrinsinc mechanisms mediated, in part, by CD8 T cells.

A simian hemorrhagic fever virus isolate from persistently infected baboons efficiently induces hemorrhagic fever disease in Japanese macaques.

Simian hemorrhagic fever virus is an arterivirus that naturally infects species of African nonhuman primates causing acute or persistent asymptomatic infections. Although it was previously estimated that 1% of baboons are SHFV-positive, more than 10% of wild-caught and captive-bred baboons tested were SHFV positive and the infections persisted for more than 10 years with detectable virus in the blood (100-1000 genomes/ml). The sequences of two baboon SHFV isolates that were amplified by a single passage in primary macaque macrophages had a high degree of identity to each other as well as to the genome of SHFV-LVR, a laboratory strain isolated in the 1960s. Infection of Japanese macaques with 100PFU of a baboon isolate consistently produced high level viremia, pro-inflammatory cytokines, elevated tissue factor levels and clinical signs indicating coagulation defects. The baboon virus isolate provides a reliable BSL2 model of viral hemorrhagic fever disease in macaques.

Human parainfluenza virus type 3 in wild nonhuman primates, Zambia.

Human parainfluenza virus type 3 (HPIV3) genome was detected in 4 baboons in Zambia. Antibody for HPIV3 was detected in 13 baboons and 6 vervet monkeys in 2 distinct areas in Zambia. Our findings suggest that wild nonhuman primates are susceptible to HPIV3 infection.

The Baboon (Papio spp.) as a model of human Ebola virus infection.

Baboons are susceptible to natural Ebola virus (EBOV) infection and share 96% genetic homology with humans. Despite these characteristics, baboons have rarely been utilized as experimental models of human EBOV infection to evaluate the efficacy of prophylactics and therapeutics in the United States. This review will summarize what is known about the pathogenesis of EBOV infection in baboons compared to EBOV infection in humans and other Old World nonhuman primates. In addition, we will discuss how closely the baboon model recapitulates human EBOV infection. We will also review some of the housing requirements and behavioral attributes of baboons compared to other Old World nonhuman primates. Due to the lack of data available on the pathogenesis of Marburg virus (MARV) infection in baboons, discussion of the pathogenesis of MARV infection in baboons will be limited.

Laboratory diagnosis of cytomegalovirus in monkeys in the Adler Breeding Center and in humans.

Monitoring of cytomegalovirus markers was carried out in the blood of humans and in the blood, lavage fluid specimens from the throat, and salivary gland tissues of monkeys of different species. Correlation between the percentage of cytomegalovirus infection and age was detected in humans. The virus was most often detected in salivary gland tissues and least so in the blood.

Properties of virion transactivator proteins encoded by primate cytomegaloviruses.

BACKGROUND: Human cytomegalovirus (HCMV) is a betaherpesvirus that causes severe disease in situations where the immune system is immature or compromised. HCMV immediate early (IE) gene expression is stimulated by the virion phosphoprotein pp71, encoded by open reading frame (ORF) UL82, and this transactivation activity is important for the efficient initiation of viral replication. It is currently recognized that pp71 acts to overcome cellular intrinsic defences that otherwise block viral IE gene expression, and that interactions of pp71 with the cell proteins Daxx and ATRX are important for this function. A further property of pp71 is the ability to enable prolonged gene expression from quiescent herpes simplex virus type 1 (HSV-1) genomes. Non-human primate cytomegaloviruses encode homologs of pp71, but there is currently no published information that addresses their effects on gene expression and modes of action. RESULTS: The UL82 homolog encoded by simian cytomegalovirus (SCMV), strain Colburn, was identified and cloned. This ORF, named S82, was cloned into an HSV-1 vector, as were those from baboon, rhesus monkey and chimpanzee cytomegaloviruses. The use of an HSV-1 vector enabled expression of the UL82 homologs in a range of cell types, and permitted investigation of their abilities to direct prolonged gene expression from quiescent genomes. The results show that all UL82 homologs activate gene expression, and that neither host cell type nor promoter target sequence has major effects on these activities. Surprisingly, the UL82 proteins specified by non-human primate cytomegaloviruses, unlike pp71, did not direct long term expression from quiescent HSV-1 genomes. In addition, significant differences were observed in the intranuclear localization of the UL82 homologs, and in their effects on Daxx. Strikingly, S82 mediated the release of Daxx from nuclear domain 10 substructures much more rapidly than pp71 or the other proteins tested. All UL82 homologs stimulated the early release of ATRX from nuclear domain 10. CONCLUSION: All of the UL82 homolog proteins analysed activated gene expression, but surprising differences in other aspects of their properties were revealed. The results provide new information on early events in infection with cytomegaloviruses.

Broad, high-magnitude and multifunctional CD4+ and CD8+ T-cell responses elicited by a DNA and modified vaccinia Ankara vaccine containing human immunodeficiency virus type 1 subtype C genes in baboons.

Candidate human immunodeficiency virus (HIV) vaccine regimens based on DNA boosted with recombinant modified vaccinia Ankara (MVA) have been in development for some time, and there is evidence for improved immunogenicity of newly developed constructs. This study describes immune responses to candidate DNA and MVA vaccines expressing multiple genes (gag, RT, tat, nef and env) from HIV-1 subtype C in chacma baboons (Papio ursinus). The vaccine regimen induced (i) strong T-cell responses, with a median of 4103 spot forming units per 10(6) peripheral blood mononuclear cells by gamma interferon (IFN-gamma) ELISPOT, (ii) broad T-cell responses targeting all five vaccine-expressed genes, with a median of 12 peptides targeted per animal and without any single protein dominating the response, (iii) balanced CD4(+) and CD8(+) responses, which produced both IFN-gamma and interleukin (IL)-2, including IL-2-only responses not detected by the ELISPOT assay, (iv) vaccine memory, which persisted 1 year after immunization and could be boosted further, despite strong anti-vector responses, and (v) mucosal T-cell responses in iliac and mesenteric lymph nodes in two animals tested. The majority of peptide responses mapped contained epitopes previously identified in human HIV infection, and two high-avidity HIV epitope responses were confirmed, indicating the utility of the baboon model for immunogenicity testing. Together, our data show that a combination of DNA and MVA immunization induced robust, durable, multifunctional CD4(+) and CD8(+) responses in baboons targeting multiple HIV epitopes that may home to mucosal sites. These candidate vaccines, which are immunogenic in this pre-clinical model, represent an alternative to adenoviral-based vaccines and have been approved for clinical trials.

Evidence of simian virus 40 exposure in a colony of captive baboons.

Simian virus 40 (SV40) is a polyomavirus for which non-human primates are the permissive host. The baboon (Papio spp.) is an old world monkey that is used in a variety of research investigations; however, natural infection of SV40 among baboons has not been thoroughly examined or reported. Initially, we were interested in determining the prevalence of SV40 infection among a captive colony of baboons based on the presence of antibodies to SV40 large T-antigen (Tag). An overall seroprevalence rate of >50% was found after screening sera from 142 baboons in the colony based on ELISA. Endpoint titer values for serum antibody binding to SV40 Tag reached as high as 1280 for 5 out of 142 baboons. Peptide binding assays revealed that a range of SV40 Tag epitopes are immunogenic in the baboon, and that individual animals differ in their humoral immune responses to SV40 Tag based on epitope recognition. Specificity to SV40 Tag and not some other primate polyomavirus encoded large Tag was further examined by serologic reactivity to peptide epitopes unique to SV40 Tag. Additional serology was performed to assess SV40 Tag reactivity by Western blot and whether antibodies were capable of neutralizing SV40 infectivity in vitro. Although antibodies with high levels of SV40 neutralization were observed in a number of the baboons, there was a lack of correlation between viral neutralization and antibodies to SV40 Tag. Further examination using molecular-based diagnosis and SV40 Tag specific real-time quantitative PCR determined that some of the baboons appeared to be exposed to SV40. DNA sequence analysis of the PCR products confirmed that SV40 Tag specific sequences were detected in baboons.

Polyomaviruses of nonhuman primates: implications for research.

Polyomaviruses are a family of small nonenveloped DNA viruses that infect birds and mammals. At least 7 nonhuman primate polyomaviruses that occur in macaques, African green monkeys, marmosets baboons, and chimpanzees have been described, as well as 4 polyomaviruses that occur in humans. Simian virus 40 (SV40), which infects macaques, was the first nonhuman primate polyomavirus identified as a contaminant of early polio vaccines. Primate polyomaviruses cause inapparent primary infections but persist in the host and can cause severe disease in situations of immunocompromise. This review describes the primate polyomaviruses, and the diseases associated with the viruses of macaques. In macaques, the greatest current concerns are the potential confounding of study results by polyomavirus infections and the zoonotic potential of SV40.

Naturally transmitted herpesvirus papio-2 infection in a black and white colobus monkey.

CASE DESCRIPTION: A 6.5-year-old female eastern black and white colobus monkey (Colobus guereza) was evaluated after acute onset of ataxia and inappetence. CLINICAL FINDINGS: The monkey was ataxic and lethargic, but no other abnormalities were detected via physical examination, radiography, or clinicopathologic analyses. During the next 2 days, the monkey's clinical condition deteriorated, and its WBC count decreased dramatically. Cytologic examination of a CSF sample revealed marked lymphohistiocytic inflammation. TREATMENT AND OUTCOME: Despite supportive care, the monkey became apneic; after 20 hours of mechanical ventilation, fatal cardiac arrest occurred. At necropsy, numerous petechiae were detected within the white matter tracts of the brain; microscopic lesions of multifocal necrosis and hemorrhage with intranuclear inclusions identified in the brain and adrenal glands were consistent with an acute herpesvirus infection. A specific diagnosis of herpesvirus papio-2 (HVP-2) infection was made on the basis of results of serologic testing; PCR assay of tissue specimens; live virus isolation from the lungs; and immunohistochemical identification of the virus within brain, spinal cord, and adrenal gland lesions. Via phylogenetic tree analysis, the colobus HVP-2 isolate was grouped with neuroinvasive strains of the virus. The virus was most likely transmitted to the colobus monkey through toys shared with a nearby colony of baboons (the natural host of HVP-2). CLINICAL RELEVANCE: To the authors' knowledge, this is the first reported case of natural transmission of HVP-2 to a nonhost species. Infection with HVP-2 should be a differential diagnosis for acute encephalopathy in primate monkeys and humans, particularly following exposure to baboons.

Complete genome sequences for nine simian enteroviruses.

Analysis of the VP1 capsid-coding sequences of the simian picornaviruses has suggested that baboon enterovirus (BaEV), SV19, SV43 and SV46 belong to the species Human enterovirus A (HEV-A) and SA5 belongs to HEV-B, whereas SV4/A2 plaque virus (two isolates of a single serotype), SV6 and N125/N203 (two isolates of a single serotype) appear to represent new species in the genus. We have further characterized by complete genomic sequencing the genetic relationships among the simian enteroviruses serotypes (BaEV, N125/N203, SA5, SV4/A2 plaque virus, SV6, SV19, SV43 and SV46) and to other enteroviruses. Phylogenetic and pairwise sequence relationships for the P1 region paralleled those of VP1 alone, and confirmed that SV4/A-2 plaque virus, SV6 and N125/N203 represent unique genetic clusters that probably correspond to three new species. However, sequence relationships in the P2 and P3 regions were quite different. In 2C, SV19, SV43 and SV46 remain clustered with the human viruses of HEV-A, but BaEV, SV6 and N125/N203 cluster together; in 3CD, SA5 (HEV-B) also joined this cluster. The 3'-non-translated region (NTR) sequences are highly conserved within each of the four human enterovirus species, but the 3'-NTRs of the simian enteroviruses are distinct from those of all human enteroviruses and generally distinct from one another. These results suggest that host species may have a significant influence on the evolution of enterovirus non-capsid sequences.

The complete genome sequence of herpesvirus papio 2 (Cercopithecine herpesvirus 16) shows evidence of recombination events among various progenitor herpesviruses.

We have sequenced the entire genome of herpesvirus papio 2 (HVP-2; Cercopithecine herpesvirus 16) strain X313, a baboon herpesvirus with close homology to other primate alphaherpesviruses, such as SA8, monkey B virus, and herpes simplex virus (HSV) type 1 and type 2. The genome of HVP-2 is 156,487 bp in length, with an overall GC content of 76.5%. The genome organization is identical to that of the other members of the genus Simplexvirus, with a long and a short unique region, each bordered by inverted repeats which end with an "a" sequence. All of the open reading frames detected in this genome were homologous and colinear with those of SA8 and B virus. The HSV gene RL1 (gamma(1)34.5; neurovirulence factor) is not present in HVP-2, as is the case for SA8 and B virus. The HVP-2 genome is 85% homologous to its closest relative, SA8. However, segment-by-segment bootstrap analysis of the genome revealed at least two regions that display closer homology to the corresponding sequences of B virus. The first region comprises the UL41 to UL44 genes, and the second region is located within the UL36 gene. We hypothesize that this localized and defined shift in homology is due to recombination events between an SA8-like progenitor of HVP-2 and a herpesvirus species more closely related to the B virus. Since some of the genes involved in these putative recombination events are determinants of virulence, a comparative analysis of their function may provide insight into the pathogenic mechanism of simplexviruses.

Divergent patterns of recent retroviral integrations in the human and chimpanzee genomes: probable transmissions between other primates and chimpanzees.

The human genome is littered by endogenous retrovirus sequences (HERVs), which constitute up to 8% of the total genomic sequence. The sequencing of the human (Homo sapiens) and chimpanzee (Pan troglodytes) genomes has facilitated the evolutionary study of ERVs and related sequences. We screened both the human genome (version hg16) and the chimpanzee genome (version PanTro1) for ERVs and conducted a phylogenetic analysis of recent integrations. We found a number of recent integrations within both genomes. They segregated into four groups. Two larger gammaretrovirus-like groups (PtG1 and PtG2) occurred in chimpanzees but not in humans. The PtG sequences were most similar to two baboon ERVs and a macaque sequence but neither to other chimpanzee ERVs nor to any human gammaretrovirus-like ERVs. The pattern was consistent with cross-species transfer via predation. This appears to be an example of horizontal transfer of retroviruses with occasional fixation in the germ line.

Serological detection of adenoviruses in non-human primates maintained in a colony in Kenya.

BACKGROUND: Adenoviruses are known to cause several human diseases including acute febrile respiratory syndromes, epidemic conjunctivitis and gastroenteritis. These diseases associated with adenovirus infection affect adults and are usually more severe in infants and children. Forty-seven human adenoviruses serotypes have so far been identified adenovirus. The diversity of these viruses has delayed progress on vaccine development due to difficulties in identifying appropriate vaccine targets. To date, limited studies have been done to determine the prevalence of adenovirus infection in non-human primates with the goal of developing a non-human primate model that can be used to study the mechanisms of infection. OBJECTIVE: To determine the prevalence of enteric adenovirus infection in Kenyan non-human primates. DESIGN: A prospective study to investigate the prevalence of enteric andenovirus infection in captive non-human primates maintained in a colony. SETTING: Faecal samples were collected from monkeys trapped from different geographical areas of Kenya and also from the ones maintained in a colony at the Institute of Primate Research (IPR), Kenya. SUBJECTS: Ninety four faecal samples were collected from three species of non-human primates consisting of various ages and sex. Samples were collected from monkeys trapped from different geographical areas of Kenya and also from the ones maintained in a colony at the Institute of Primate Research (IPR), Kenya. All the faecal samples were screened for presence of adenoviruses using a commercial antigen-capture enzyme immunoassay (EIA) kit, this is an enzyme-linked immunosorbent assay (ELISA) kit designed for diagnosis of human enteric adenoviruses in stool samples. RESULTS: The highest prevalence of adenoviruses, detected by EIA kit, was in olive baboons (Papio anubis, 52.9%), followed by vervet monkeys (Cercopithecus aethiops, 48.9%) and the yellow baboons (Papio cynocephalus, 18.8%). Sub-grouping within each species (based on age and sex) indicated no significant differences (p > 0.05) in adenovirus infection signifying equal susceptibility. The prevalence of adenoviruses in vervet monkeys that were also Simian Immunodeficiency virus (SIV) seropositive was determined and shown to be 63.2%. CONCLUSION: The results of this study indicate that adenovirus infection is prevalent among non-human primates in Kenya. These findings suggest that cross species transmission in Kenyan non-human primates may be a common occurrence and there is a possibility of zoonotic transmission of adenoviruses. Furthermore, our results highlight the potential of using these non-human primates as models for testing safety and efficacy of candidate adenovirus vaccines prior to clinical trials in humans.

Endogenous retrovirus long terminal repeats as ready-to-use mobile promoters: the case of primate beta3GAL-T5.

Throughout the course of vertebrate evolution, germline retroviral infections have resulted in heritable provirus insertions into host DNA. These endogenous retroviruses (ERVs) contain long terminal repeat (LTR) promoters that can be adopted for use by nearby host genes. It is not known whether the transcription factor (TF) binding sites and tissue-specificities of modern LTR gene promoters have been retained since the time of ERV insertion, or if these features evolved later as the LTR became involved in host gene regulation. To address this issue, we have conducted a case study of the ERV-L LTR promoter of human beta1,3-galactosyltransferase 5 (beta3GAL-T5). We have previously shown that the human beta3GAL-T5 LTR promoter is responsible for the majority of gene transcripts in the colon. The murine beta3gal-t5 gene is also expressed primarily in the colon, despite the absence of an orthologous ERV-L LTR in the mouse genome. We therefore hypothesized that both the ERV-L LTR and the non-retroviral ancestral beta3GAL-T5 promoter were active in the colon at the time of ERV insertion. In support of this hypothesis, we have shown that the orthologous LTRs of four non-human primates are also active in a human colorectal cell line, and that the baboon LTR is active in primary baboon colon tissue. We also present evidence that the functional TF binding sites of the human beta3GAL-T5 LTR promoter were present in the original consensus sequence for this class of LTRs. Upon similar analysis of other ERV sequences, we have concluded that this evolutionary history is shared by certain other LTR gene promoters, and may be a general phenomenon.

Development of a real-time QPCR assay for the detection of RV2 lineage-specific rhadinoviruses in macaques and baboons.

BACKGROUND: Two distinct lineages of rhadinoviruses related to Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) have been identified in macaques and other Old World non-human primates. We have developed a real-time quantitative PCR (QPCR) assay using a TaqMan probe to differentially detect and quantitate members of the rhadinovirus-2 (RV2) lineage. PCR primers were derived from sequences within ORF 60 and the adjacent ORF 59/60 intergenic region which were highly conserved between the macaque RV2 rhadinoviruses, rhesus rhadinovirus (RRV) and Macaca nemestrina rhadinovirus-2 (MneRV2). These primers showed little similarity to the corresponding sequences of the macaque RV1 rhadinoviruses, retroperitoneal fibromatosis herpesvirus Macaca nemestrina (RFHVMn) and Macaca mulatta (RFHVMm). To determine viral loads per cell, an additional TaqMan QPCR assay was developed to detect the single copy cellular oncostatin M gene. RESULTS: We show that the RV2 QPCR assay is linear from less than 2 to more than 300,000 copies using MneRV2 DNA, and is non-reactive with RFHVMn DNA up to 1 billion DNA templates per reaction. RV2 loads ranging from 6 to 2,300 viral genome equivalent copies per 10(6) cells were detected in PBMC from randomly sampled macaques from the Washington National Primate Research Center. Screening tissue from other primate species, including another macaque, Macaca fascicularis, and a baboon, Papio cynocephalus, revealed the presence of novel rhadinoviruses, MfaRV2 and PcyRV2, respectively. Sequence comparison and phylogenetic analysis confirmed their inclusion within the RV2 lineage of KSHV-like rhadinoviruses. CONCLUSIONS: We describe a QPCR assay which provides a quick and sensitive method for quantitating rhadinoviruses belonging to the RV2 lineage of KSHV-like rhadinoviruses found in a variety of macaque species commonly used for biomedical research. While this assay broadly detects different RV2 rhadinovirus species, it is unreactive with RV1 rhadinovirus species which commonly co-infect the same primate hosts. We also show that this QPCR assay can be used to identify novel RV2 rhadinoviruses in different primate species.