The Prostate Cancer-Associated Human Retrovirus XMRV Lacks Direct Transforming Activity but Can Induce Low Rates of Transformation in Cultured Cells

Xenotropic murine leukemia-related virus (XMRV) was identified in association with human prostate cancer and chronic fatigue syndrome. To examine the infection potential, kinetics, and tissue distribution of XMRV in an animal model, we inoculated five macaques with XMRV intravenously. XMRV established a persistent, chronic disseminated infection, with low transient viremia and provirus in blood lymphocytes during acute infection. Although undetectable in blood after about a month, XMRV viremia was reactivated at 9 months, confirming the chronicity of the infection. Furthermore, XMRV Gag was detected in tissues throughout, with wide dissemination throughout the period of monitoring. Surprisingly, XMRV infection showed organ-specific cell tropism, infecting CD4 T cells in lymphoid organs including the gastrointestinal lamina propria, alveolar macrophages in lung, and epithelial/interstitial cells in other organs, including the reproductive tract. Of note, in spite of the intravenous inoculation, extensive XMRV replication was noted in prostate during acute but not chronic infection even though infected cells were still detectable by fluorescence in situ hybridization (FISH) in prostate at 5 and 9 months postinfection. Marked lymphocyte activation occurred immediately postinfection, but antigen-specific cellular responses were undetectable. Antibody responses were elicited and boosted upon reexposure, but titers decreased rapidly, suggesting low antigen stimulation over time. Our findings establish a nonhuman primate model to study XMRV replication/dissemination, transmission, pathogenesis, immune responses, and potential future therapies.Xenotropic murine leukemia-related virus (XMRV) is a novel gammaretrovirus, initially identified in human prostate cancer using a Virochip DNA microarray (43) in men with a low-activity variant of RNASEL, an enzyme involved in innate immunity via type I interferons (14). Although related to murine leukemia virus (MLV) and probably acquired by zoonotic infection, human tissue-derived XMRV clearly segregates from other gammaretroviruses, genotypically arguing against the hypothesis that such human infection is acquired via repeated zoonotic transmission (43). The association of XMRV with prostate cancer has since been confirmed by other laboratories, albeit with a potentially different cellular tropism (34). In addition, association with RNASEL deficiency has been variable (1, 7, 15, 34), suggesting that low levels of RNASEL may not be a requirement for productive infection or viral propagation in humans. Nevertheless, the association of RNASEL mutations and prostate cancer has been reinforced by the recent discovery that a prostate cell line, 22Rv1, was derived from a patient with a low-activity RNASEL genotype (15). RNASEL dysfunction has also been associated with another disease, chronic fatigue syndrome (CFS) (8,20,21,38,42), which prompted an investigation into a potential association of XMRV with CFS. In a geographically restricted cohort, up to 67% of CFS patients were found ...

Section: Discussionmentioning

confidence: 76%

Infection, Viral Dissemination, and Antibody Responses of Rhesus Macaques Exposed to the Human Gammaretrovirus XMRV

Onlamoon

Gupta

Sharma

et al. 2011

“…NZB virus infection showed intermediate toxicity, with cell death being apparent in 11 to 12 days. Note that we previously reported that XMRV infection was not toxic to mink cells (22), but the virus used for infection in that study was a mixture of XMRV and the LAPSN vector. The LAPSN vector replicates more efficiently than XMRV in coinfected cells (22), and this may explain why the virus mixture showed no toxic effects.…”

Section: Xmrv Induces Apoptosis In Sy5y Neuroblastoma Cellsmentioning

confidence: 99%

“…We first tested XMRV for a possible transforming activity that might explain a role for XMRV in prostate cancer but found no evidence that XMRV was acutely oncogenic (22). We next explored the possibility that XMRV was neurotoxic and that this might explain a role for XMRV in the neuromuscular disease aspects of CFS.…”

mentioning

confidence: 99%

Xpr1 Is an Atypical G-Protein-Coupled Receptor That Mediates Xenotropic and Polytropic Murine Retrovirus Neurotoxicity

Vaughan

Mendoza

Aranda

et al. 2012

Self Cite

Xenotropic murine leukemia virus-related virus (XMRV) was first identified in human prostate cancer tissue and was later found in a high percentage of humans with chronic fatigue syndrome (CFS). While exploring potential disease mechanisms, we found that XMRV infection induced apoptosis in SY5Y human neuroblastoma cells, suggesting a mechanism for the neuromuscular pathology seen in CFS. Several lines of evidence show that the cell entry receptor for XMRV, Xpr1, mediates this effect, and chemical cross-linking studies show that Xpr1 is associated with the G␤ subunit of the G-protein heterotrimer. The activation of adenylate cyclase rescued the cells from XMRV toxicity, indicating that toxicity resulted from reduced G-protein-mediated cyclic AMP (cAMP) signaling. Some proteins with similarity to Xpr1 are involved in phosphate uptake into cells, but we found no role of Xpr1 in phosphate uptake or its regulation. Our results indicate that Xpr1 is a novel, atypical G-protein-coupled receptor (GPCR) and that xenotropic or polytropic retrovirus binding can disrupt the cAMP-mediated signaling function of Xpr1, leading to the apoptosis of infected cells. We show that this pathway is also responsible for the classic toxicity of the polytropic mink cell focus-forming (MCF) retrovirus in mink cells. Although it now seems clear that the detection of XMRV in humans was the result of sample contamination with a recombinant mouse virus, our findings may have relevance to neurologic disease induced by MCF retroviruses in mice.

“…Furthermore, XMRV was found at high titers in the 22Rv1 human prostate cancer cell line (20) and was recently shown to have most likely originated from recombination between two different endogenous murine retrovirus sequences during derivation of the 22Rv1 human prostate cancer cell line by serial passage of a human prostate tumor xenograft in nude mice (21,22). These findings have led to the general scientific consensus that XMRV is not a human retrovirus but a novel recombinant murine retrovirus with some unique biological properties (23). XMRV has a broad host range and can infect a variety of human cell lines in vitro (24)(25)(26)(27) and nonhuman primate cells and tissues in vivo (5,28).…”

mentioning

confidence: 97%

No Evidence of Xenotropic Murine Leukemia Virus-Related Virus Transmission by Blood Transfusion from Infected Rhesus Macaques

Williams

Galvin²,

Gao

et al. 2013

The discovery of xenotropic murine leukemia virus-related virus (XMRV) in human tissue samples has been shown to be due to virus contamination with a recombinant murine retrovirus. However, due to the unknown pathogenicity of this novel retrovirus and its broad host range, including human cell lines, it is important to understand the modes of virus transmission and develop mitigation and management strategies to reduce the risk of human exposure and infection. XMRV transmission was evaluated by whole-blood transfusion in rhesus macaques. Monkeys were infected with XMRV to serve as donor monkeys for blood transfers at weeks 1, 2, and 3 into naïve animals. The donor and recipient monkeys were evaluated for XMRV infection by nested PCR assays with nucleotide sequence confirmation, Western blot assays for development of virus-specific antibodies, and coculture of monkey peripheral blood mononuclear cells (PBMCs) with a sensitive target cell line for virus isolation. XMRV infection was demonstrated in the virus-injected donor monkeys, but there was no evidence of virus transmission by whole-blood transfusion to naïve monkeys based upon PCR analysis of PBMCs using XMRV-specific gag and env primers, Western blot analysis of monkey plasma up to 31 to 32 weeks after transfusion, and coculture studies using monkey PBMCs from various times after transfusion. The study demonstrates the lack of XMRV transmission by whole-blood transfusion during the acute phase of infection. Furthermore, analysis of PBMC viral DNA showed extensive APOBEC-mediated G-to-A hypermutation in a donor animal at week 9, corroborating previous results using macaques and supporting the possible restriction of XMRV replication in humans by a similar mechanism.