Comment on "Detection of an infectious retrovirus, XMRV, in blood cells of patients with chronic fatigue syndrome"

Chronic fatigue syndrome: 3 cases and a discussion of the natural history of attention-deficit/hyperactivity disorder

Fatigue is commonly reported in the primary care setting; however, its cause is often unclear. This article presents 3 cases involving patients with chronic fatigue syndrome who responded poorly to treatment. After clinical evaluation, all patients were found to meet criteria for attention-deficit/hyperactivity disorder (ADHD) and underwent a standard regimen of a psychostimulant medication. After treatment with psychostimulants, the 3 patients reported improved symptoms of fatigue and pain, and cognitive and core ADHD symptoms. These cases suggest that ADHD and chronic fatigue syndrome (and possibly fibromyalgia) share a common underlying mechanism. This article presents a model suggesting that over time, ADHD (predominantly inattentive type) develops into a syndrome of chronic fatigue and pain. These cases indicate that fatigue may be an important presenting symptom of adult ADHD. These cases also suggest the need for additional research to determine the prevalence of ADHD in patients who present with fatigue, and, in those meeting criteria for ADHD, the responsiveness of fatigue to psychostimulant treatment.

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.

No evidence for the involvement of XMRV or MCV in the pathogenesis of breast cancer

Background:

The aetiology of breast cancer remains elusive. A viral aetiology has been proposed, but to date no virus has been conclusively demonstrated to be involved. Recently, two new viruses, namely Merkel cell polyomavirus (MCV) and xenotropic murine leukaemia virus-related virus (XMRV) have been identified and implicated in the pathogenesis of Merkel cell carcinoma (MCC) and familial form of prostate cancer, respectively.

Methods:

We examined 204 samples from 58 different cases of breast cancer for presence of MCV or XMRV by PCR. Samples consisted of both malignant and non-malignant tissues. Additionally, we included 6 cases of MCC and 12 cases of prostate cancer as potential controls for MCV and XMRV, respectively.

Results:

All of the breast cancer samples examined were negative for both MCV and XMRV. However, 4/6 MCC and 2/12 prostate cancer samples were found to be positive for MCV and XMRV, respectively. Sequence analysis of the amplified products confirmed that these sequences belonged to MCV and XMRV.

Conclusion:

We conclude that there is no evidence for the involvement of MCV or XMRV in the pathogenesis of breast cancer. What role these viruses have in the pathogenesis of MCC and prostate carcinomas remains to be demonstrated.

Chronic widespread musculoskeletal pain, fatigue, depression and disordered sleep in chronic post-SARS syndrome; a case-controlled study

BACKGROUND

The long term adverse effects of Severe Acute Respiratory Syndrome (SARS), a viral disease, are poorly understood.

METHODS

Sleep physiology, somatic and mood symptoms of 22 Toronto subjects, 21 of whom were healthcare workers, (19 females, 3 males, mean age 46.29 yrs.+/- 11.02) who remained unable to return to their former occupation (mean 19.8 months, range: 13 to 36 months following SARS) were compared to 7 healthy female subjects. Because of their clinical similarities to patients with fibromyalgia syndrome (FMS) these post-SARS subjects were similarly compared to 21 drug free female patients, (mean age 42.4 +/- 11.8 yrs.) who fulfilled criteria for fibromyalgia.

RESULTS

Chronic post-SARS is characterized by persistent fatigue, diffuse myalgia, weakness, depression, and nonrestorative sleep with associated REM-related apneas/hypopneas, an elevated sleep EEG cyclical alternating pattern, and alpha EEG sleep anomaly. Post- SARS patients had symptoms of pre and post-sleep fatigue and post sleep sleepiness that were similar to the symptoms of patients with FMS, and similar to symptoms of patients with chronic fatigue syndrome. Both post-SARS and FMS groups had sleep instability as indicated by the high sleep EEG cyclical alternating pattern rate. The post-SARS group had a lower rating of the alpha EEG sleep anomaly as compared to the FMS patients. The post-SARS group also reported less pre-sleep and post-sleep musculoskeletal pain symptoms.

CONCLUSIONS

The clinical and sleep features of chronic post-SARS form a syndrome of chronic fatigue, pain, weakness, depression and sleep disturbance, which overlaps with the clinical and sleep features of FMS and chronic fatigue syndrome.

Evidence and controversies on the role of XMRV in prostate cancer and chronic fatigue syndrome

The recent discovery of xenotropic murine leukaemia virus-related virus (XMRV) in prostate cancer tissues and in the blood of individuals suffering from chronic fatigue syndrome has attracted considerable interest. However, the relevance and significance of XMRV to human disease remain unclear, since the association has not been confirmed in other studies. XMRV is the first gammaretrovirus to be found in humans. XMRV and murine leukaemia viruses share similar structures and genomic organisation. Human restriction factors such as APOBEC3 or tetherin inhibit XMRV replication. Although XMRV induces low rates of transformation in cell culture, it might be able to induce cancer by low-frequency insertional activation of oncogenes or through the generation of highly active transforming viruses. A preference for regulatory regions of transcriptional active genes has been observed after a genomic-wide analysis of XMRV integration sites. Genes related to carcinogenesis and androgen signalling have been identified in the vicinity of integration sites. The XMRV genome contains a glucocorticoid responsive element, and androgens could modulate viral replication in the prostate. Evidence supporting the involvement of XMRV in chronic fatigue syndrome is still very weak, and needs further confirmation and validation. Currently approved anti-retroviral drugs such as zidovudine, tenofovir and raltegravir are efficient inhibitors of XMRV replication in vitro. These drugs might be useful to treat XMRV infection in humans. The identification of XMRV has potentially serious health implications for the implementation of novel techniques including gene therapy or xenotransplantation, while raising concerns on the need for screening donated blood to prevent transmission through transfusion.