No xenotropic murine leukemia virus-related virus detected in fibromyalgia patients

Lack of evidence for retroviral infections formerly related to chronic fatigue in Spanish fibromyalgia patients

Background

The etiology of fibromyalgia and chronic fatigue syndrome (FM/CFS) is currently unknown. A recurrent viral infection is an attractive hypothesis repeatedly found in the literature since it would explain the persistent pain and tiredness these patients suffer from. The initial striking link of two distinct orphan retroviruses: the gamma retroviruses murine leukemia virus (MLV)-related virus and the delta retrovirus T-lymphotropic virus type 2 (HTLV-2) to chronic fatigue have not been confirmed to date.

Results

Genomic DNA (gDNA) from 75 fibromyalgia patients suffering from chronic fatigue and 79 age-matched local healthy controls were screened for the presence of MLV-related and HTLV-2 related proviral sequences. The XMRV env gene was amplified in 20% of samples tested (24% patients/15% healthy controls). Unexpectedly, no PCR amplifications from independent gDNA preparations of the same individuals were obtained. None of the positive samples showed presence of contaminating murine sequences previously reported by other investigators, neither contained additional regions of the virus making us conclude that the initial env amplification came from spurious air-driven amplicon contaminants. No specific HTLV-2 sequences were obtained at any time from any of the 154 quality-controlled gDNA preparations screened.

Conclusions

Previous associations between MLV-related or HTLV-2 retrovirus infection with chronic fatigue must be discarded. Thus, studies showing positive amplification of HTLV-2 sequences from chronic fatigue participants should be revised for possible undetected technical problems.

To avoid false positives of viral infection, not only extreme precautions should be taken when nested-PCR reactions are prepared and exhaustive foreign DNA contamination controls performed, but also consistent amplification of diverse regions of the virus in independent preparations from the same individual must be demanded.

The fact that our cohort of patients did not present evidence of any of the two types of retroviral infection formerly associated to chronic fatigue does not rule out the possibility that other viruses are involved in inciting or maintaining fibromyalgia and/or chronic fatigue conditions.

No Detection of the Retrovirus Xenotropic Murine Leukemia Virus-Related Virus in Individuals with Hemophilia

<b><i>Background:</i></b> Xenotropic murine leukemia virus-related virus (XMRV) is a retrovirus that has recently been related to prostate cancers and chronic fatigue syndrome. Since other human-pathogenic retroviruses, such as HIV, human T-lymphotropic virus type I (HTLV-I) and –II, are known blood-transmitted pathogens, XMRV might present another hazard associated with products derived from in vitro cultures of human or animal origin, or blood component-based therapeutics. Here, we investigated whether XMRV was transmitted to individuals with hemophilia and frequent exposure to plasma-derived or recombinant clotting factors. <b><i>Methods: </i></b>We used highly sensitive real-time PCR to test plasma samples from 127 consecutive individuals with hemophilia who consulted our hemophilia center either for treatment or for a standard check-up. <b><i>Results: </i></b>From the 127 hemophiliacs, 80 had prior contact to persons with either hepatitis B (n = 30), hepatitis C (n = 74) and/or HIV (n = 21), and 30 were currently being treated with plasma-derived and 97 with recombinant factor concentrates. None of the individuals tested positive for XMRV. <b><i>Conclusions: </i></b>Independent of the ongoing discussion on whether the positive XMRV testing in initial reports was a result of reagent, sample, or tissue contamination, and whether XMRV is a real threat or a testing artifact, our data suggest that XMRV might not play an important role for hemophiliacs.

Absence of xenotropic murine leukemia virus-related virus in Italian patients affected by chronic fatigue syndrome, fibromyalgia, or rheumatoid arthritis

The xenotropic murine leukemia virus-related virus (XMRV) has been recently linked to chronic fatigue syndrome in a US cohort in whom the virus was demonstrated in 67&#x0025; patients vs 3.7&#x0025; healthy controls. Albeit this finding was not substantiated by subsequent reports and eventually considered a laboratory contamination, the matter is still the object of intense debate and scrutiny in various cohorts of patients. In this work we examined well-clinically characterized Italian patients affected by chronic fatigue syndrome, and also fibromyalgia and rheumatoid arthritis, two chronic illnesses of basically unknown etiology which show quite a few symptoms in common with chronic fatigue syndrome. Although we used recently updated procedures and controls, the XMRV was not found in 65 patients with chronic fatigue syndrome diagnosis, 55 with fibromyalgia, 25 with rheumatoid arthritis, nor in 25 healthy controls. These results add to the ever-growing number of surveys reporting the absence of XMRV in chronic fatigue syndrome patients and suggest that the virus is also absent in fibromyalgia and rheumatoid arthritis.

The tale of xenotropic murine leukemia virus-related virus

In 2006, a new retrovirus was isolated from prostate cancer patient tissue. Named xenotropic murine leukemia virus-related virus (XMRV), this was potentially the third class of retrovirus to be pathogenic in humans. XMRV made a more dramatic impact on the wider scientific community, and indeed the media, in 2009 when it was reported to be present in a remarkably high proportion of patients with chronic fatigue syndrome as well as a significant, albeit smaller, proportion of healthy controls. The apparent strong link to disease and the fear of a previously unknown retrovirus circulating in the general population lead to a surge in XMRV research. Subsequent studies failed to find an association of XMRV with disease and, in most cases, failed to find the virus in human samples. In 2011, the case against XMRV and human disease strengthened, ending with several decisive publications revealing the origin of the virus and demonstrating contamination of samples. In this review, we outline the passage of research on XMRV and its potential association with disease from its isolation to the present day, where we find ourselves at the end of a turbulent story.

Lack of the detection of XMRV or polytropic MLV-related sequences in blood cells from HIV-1-infected patients in Spain

BACKGROUND

Xenotropic murine leukemia virus-related virus (XMRV) and polytropic murine leukemia virus (MLV)-related virus are recently described human gammaretroviruses that have been associated with prostate cancer and chronic fatigue syndrome. These studies have been controversial because a number of laboratories have been unable to find evidence of XMRV in similar groups of patients or controls. Because the existence of XMRV raises many questions, we decided to study its presence in a group of patients infected with HIV-1 with a high proportion of intravenous drug use and coinfection by hepatitis C virus.

METHODS

Forty HIV-1-infected patients under follow-up in our institution were screened for XMRV/MLV by nested polymerase chain reaction using primers targeting the gag and env region. Specific primers for mouse mitochondrial DNA were used to rule out contamination.

RESULTS

No evidence of XMRV or polytropic MLV-related sequences was found in any sample from patients or controls. Four samples yielded polymerase chain reaction bands whose sequence corresponded to murine endogenous retroviral sequences, however, contamination with mouse cell DNA was subsequently confirmed.

CONCLUSIONS

XMRV/MLV viruses do not seem to be associated with HIV-1 infection or intravenous drug use. Contamination of samples or reagents by genomic murine DNA or XMRV vectors could account for the sporadic detection of positive samples for XMRV and related agents.

Restricted replication of xenotropic murine leukemia virus-related virus in pigtailed macaques

Although xenotropic murine leukemia virus-related virus (XMRV) has been previously linked to prostate cancer and myalgic encephalomyelitis/chronic fatigue syndrome, recent data indicate that results interpreted as evidence of human XMRV infection reflect laboratory contamination rather than authentic in vivo infection. Nevertheless, XMRV is a retrovirus of undefined pathogenic potential that is able to replicate in human cells. Here we describe a comprehensive analysis of two male pigtailed macaques (Macaca nemestrina) experimentally infected with XMRV. Following intravenous inoculation with >10(10) RNA copy equivalents of XMRV, viral replication was limited and transient, peaking at ≤2,200 viral RNA (vRNA) copies/ml plasma and becoming undetectable by 4 weeks postinfection, though viral DNA (vDNA) in peripheral blood mononuclear cells remained detectable through 119 days of follow-up. Similarly, vRNA was not detectable in lymph nodes by in situ hybridization despite detectable vDNA. Sequencing of cell-associated vDNA revealed extensive G-to-A hypermutation, suggestive of APOBEC-mediated viral restriction. Consistent with limited viral replication, we found transient upregulation of type I interferon responses that returned to baseline by 2 weeks postinfection, no detectable cellular immune responses, and limited or no spread to prostate tissue. Antibody responses, including neutralizing antibodies, however, were detectable by 2 weeks postinfection and maintained throughout the study. Both animals were healthy for the duration of follow-up. These findings indicate that XMRV replication and spread were limited in pigtailed macaques, predominantly by APOBEC-mediated hypermutation. Given that human APOBEC proteins restrict XMRV infection in vitro, human XMRV infection, if it occurred, would be expected to be characterized by similarly limited viral replication and spread.

Phylogenetic analysis of murine leukemia virus sequences from longitudinally sampled chronic fatigue syndrome patients suggests PCR contamination rather than viral evolution

Xenotropic murine leukemia virus (MLV)-related virus (XMRV) has been amplified from human prostate cancer and chronic fatigue syndrome (CFS) patient samples. Other studies failed to replicate these findings and suggested PCR contamination with a prostate cancer cell line, 22Rv1, as a likely source. MLV-like sequences have also been detected in CFS patients in longitudinal samples 15 years apart. Here, we tested whether sequence data from these samples are consistent with viral evolution. Our phylogenetic analyses strongly reject a model of within-patient evolution and demonstrate that the sequences from the first and second time points represent distinct endogenous murine retroviruses, suggesting contamination.

Xenotropic murine leukemia virus-related virus (XMRV) in patients with systemic lupus erythematosus

OBJECTIVES

Xenotropic murine leukemia virus-related virus (XMRV)-specific proviral DNA has been recently detected in peripheral blood mononuclear cells of patients with chronic fatigue syndrome. Since chronic fatigue is commonly reported in patients with systemic lupus erythematosus (SLE) we aimed at testing the presence of this virus in these patients.

METHODS

Ninety-five SLE patients, 45 of whom had a Fatigue Severity Scale score higher than 3, were included. Molecular analyses were performed by PCR from DNA obtained from the whole blood of both SLE patients and 50 healthy controls.

RESULTS

None of the 145 samples analyzed yielded the specific XMRV PCR product.

CONCLUSIONS

We conclude that XMRV is not detected in blood neither from SLE patients nor from healthy controls. It leads to infer that other environmental and biological triggers (different from XMRV) may account for the increased levels of fatigue over the course of SLE.

No evidence of XMRV or related retroviruses in a London HIV-1-positive patient cohort

Background

Several studies have implicated a recently discovered gammaretrovirus, XMRV (Xenotropic murine leukaemia virus-related virus), in chronic fatigue syndrome and prostate cancer, though whether as causative agent or opportunistic infection is unclear. It has also been suggested that the virus can be found circulating amongst the general population. The discovery has been controversial, with conflicting results from attempts to reproduce the original studies.

Methodology/Principal Findings

We extracted peripheral blood DNA from a cohort of 540 HIV-1-positive patients (approximately 20% of whom have never been on anti-retroviral treatment) and determined the presence of XMRV and related viruses using TaqMan PCR. While we were able to amplify as few as 5 copies of positive control DNA, we did not find any positive samples in the patient cohort.

Conclusions/Significance

In view of these negative findings in this highly susceptible group, we conclude that it is unlikely that XMRV or related viruses are circulating at a significant level, if at all, in HIV-1-positive patients in London or in the general population.