Finally a Viral Cause of Chronic Fatigue Syndrome? Or Not? – How Results Can Vary and Depend on Multiple Factors

15 02 2010

Last week @F1000 (on Twitter) alerted me to an interesting discussion at F1000 on  a paper in Science, that linked Chronic fatigue syndrome (CFS) to a newly discovered human virus XRMV [1]

This finding was recently disputed by another study in PLOS [2], that couldn’t reproduce the results.  This was highlighted in an excellent post by neuroskeptic “Chronic Fatigue Syndrome in “not caused by single virus” shock!

Here is my take on the discrepancy.

Chronic fatigue syndrome (CFS) is a debilitating disorder with unknown etiology. CFS causes extreme fatigue of the kind that does not go  away after a rest. Symptoms of CFS include fatigue for 6 months or more and experiencing other problems such as muscle pain, memory problems, headaches, pain in multiple joints and  sleep problems. Since other illnesses can cause similar symptoms, CFS is hard to diagnose. (source: Medline Plus).

No one knows what causes CFS, but a viral cause has often been suspected, at least in part of the CFS patients. Because the course of the disease often resembles a post-viral fatigue, CFS has also been referred to as post-viral fatigue syndrome (PVFS).

The article of Lombardi [1], published in October 2009 in Science, was a real breakthrough. The study showed that two thirds of patients with CFS were infected with a novel gamma retrovirus, xenotropic murine leukaemia virus-related virus (XMRV). XMVR was previously linked to prostate cancer.

Lombardi et al  isolated DNA from white blood cells (Peripheral Blood Mononuclear Cells or PBMCs) and assayed the samples for XMRV gag sequences by nested polymerase chain reaction (PCR).

The PCR is a technique that allows the detection of a single or few copies of target DNA by amplifying it across several orders of magnitude, generating thousands to millions of copies of a particular DNA. Nested PCR amplifies the resultant amplicon several orders of magnitude further. In the first round external primers are used (short DNA-sequences that fit the outer end of the piece of DNA to be amplified) and an internal set of primers is used for the second round. Nested PCR is often used if the target DNA is not abundantly present and to avoid the comtamination with products that are amplified as a spin-off due to the amplification of artifacts (sites to which the primers bind as well)

[I used a similar approach 15-20 years ago to identify a lymphoma-characteristic translocation in tonsils and purified B cells of (otherwise) healthy individuals. By direct sequencing I could prove that each sequence was unique in its breakpoint sequence, thereby excluding that the PCR-products arose by contamination of an amplified positive control. All tumor cells had the translocation against one in 100,000 or 1,000,000 normal cells. To be able to detect the oncogene in B cells, B cells had to be purified by FACS. Otherwise the detection limit could not be reached]

Lombardi could detect XMRV gag DNA in 68 of 101 patients (67%) as compared to 8 of 218 (3.7%) healthy controls. Detection of gag as well as env XMRV was confirmed in 7 of 11 CFS samples at the Cleveland Clinic (remarkably these are only shown in Fig 1A of the paper, thus not the original PCR-results).
In contrast, XMRV gag sequences were detected in 8 of 218 (3.7%) PBMC DNA specimens from healthy individuals. Of the 11 healthy control DNA samples analyzed by PCR, only one sample was positive for gag and none for env. The XMRV gag and env sequences were more than 99% similar to those previously reported for prostate tumor–associated strains of XMRV. The authors see this as proof against contamination of samples with prostate cancer associated XMRV-DNA.

Not only PCR experiments were done. Using intracellular flow cytometry and Western blot assays XMRV proteins were found to be expressed in PBMCs from CFS patients. CFS patiens had anti-XMRV antibodies and cell culture experiments revealed that patient-derived XMRV was infectious. These findings are consistent with but do not prove that XMRV may be a contributing factor in the pathogenesis of CFS. XMRV might just be an innocent bystander. However, unlike XMRV-positive prostate cancer cells, XMRV infection status did not not correlate with the RNASEL genotype.

The Erlwein study was published within 3 months after the first article. It is much simpler in design. DNA was extracted from whole blood (not purified white blood cells) and subjected to a nested PCR using another set of primers. The positive control was an end-point dilution of the plasmid. Water served as a negative control. None of the 186 CSF samples was positive.

The question then is: which study is true? (although it should be stressed that the Science paper just shows a link between the virus and CFS, not a causal relationship)

Regional Differences

Both findings could be “real” if there was a regional difference in occurrence of the virus. Indeed XMRV has previously been detected in prostate cancer cells from American patients, but not from German and Irish patients.

Conflict of Interest

Lombardi’s clinic [1] offers $650 diagnostic test to detect XMRV, so it is of real advantage to the authors of the first paper that the CSF-samples are positive for the virus. On the other hand Prof. Simon Wessely of the second paper has built his career on the hypothesis that CFS is a form of psychoneurosis, that should be treated with cognitive behavior therapy. The presence of a viral (biological) cause would not fit in.

Shortcomings of the Lombardi-article [1]

Both studies have used nested PCR to detect XMRV. Because of the enormous amplification potential, PCR can easily lead to contamination (with the positive control) and thus false positive results. Indeed it is very easy to get contamination from an undiluted positive into a weakly positive or negative sample.

Charles Chiu who belongs to the group detecting XMRV in a specific kind of hereditary prostate cancer, puts it like this [5]:

In their Dissenting Opinion of this article, Moore and Shuda raise valid concerns regarding the potential for PCR contamination in this study. Some concerns include 1) the criteria for defining CFS/ME in the patients and in controls were not explicitly defined, 2) nested PCR was used and neither in a blinded nor randomized fashion, 3) the remarkable lack of diversity in the six fully sequenced XMRV genomes (<6 nucleotide average difference across genome) — with Fig. S1 even showing that for one fully sequenced isolate two of the single nucleotide differences were “N’s” — clearly the result of a sequencing error, 4) failure to use Southern blotting to confirm PCR results, and 5) primary nested PCR screening done in one lab as opposed to independent screening from start to finish in two different laboratories. Concerns have also been brought up with respect to the antigen testing

Shortcomings of the Erlwein-article [2]

Many people have objected that the population of CSF patients is not the same in both studies. Sure it is difficult enough to diagnose CSF (which is only done by exclusion), but according to many commenters of the PLOS study there was a clear bias towards more depressed patients. Therefore, a biological agent is less likely the cause of the disease in these patients. In contrast the US patients had all kinds of physical constraints and immunological problems.

The review process was also far less stringent: 3 days versus several months.

The PLOS study might have suffered from the opposite of contamination: failure to amplify the rare CSF-DNA. This is not improbable. The Erlwein group did not purify the blood cells, used other primers, amplified another sequences and did not test DNA of normal individuals. The positive control was diluted in water not in human DNA. The negative control was water.

Omitting cell purification can lead to a lower relative amount of the XMRV-DNA or to inhibition (often seen this with unpurified samples). Furthermore the gel results seem of poor quality (see Fig 2). The second round of the positive PCR sample results in an overloaded lane with too many aspecific bands (lane 9), whereas the first round leads to a very vague low molecular band (lane 10). True that the CSF-samples also run two rounds, but why aren’t the aspecific bands seen here? It would have been better to use a tenfold titration of the positive control in human DNA (this might be a more real imitation of the CSF samples: (possibly) a rare piece of XMRV DNA mixed with genomic DNA) and to use normal DNA as control, not water.Another point is that the normal XMRV-incidence of 1-3,7% in healthy controls is not reached in the PLOS study, although this could be a matter of chance (1 out of 100).

Further Studies

Anyway, we can philosophize, but the answer must await further studies. There are several ongoing efforts.


  1. Lombardi VC, Ruscetti FW, Das Gupta J, Pfost MA, Hagen KS, Peterson DL, Ruscetti SK, Bagni RK, Petrow-Sadowski C, Gold B, Dean M, Silverman RH, & Mikovits JA (2009). Detection of an infectious retrovirus, XMRV, in blood cells of patients with chronic fatigue syndrome. Science (New York, N.Y.), 326 (5952), 585-9 PMID: 19815723
  2. Erlwein, O., Kaye, S., McClure, M., Weber, J., Wills, G., Collier, D., Wessely, S., & Cleare, A. (2010). Failure to Detect the Novel Retrovirus XMRV in Chronic Fatigue Syndrome PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008519
  5. Charles Chiu: Faculty of 1000 Biology, 19 Jan 2010

Photo Credits

Nested PCR

Peter Palese on H1N1/Influenza, Porcine and Otherwise

9 09 2009

Vodpod videos no longer available.

Seen on MicrobeWorld, posted by Chris Condayan: a video in which Peter Palese, Professor and Chairman of the Department of Microbiology and Infectious Diseases at Mt. Sinai, explains H1N1/swine flu, the natural herd immunity that all humans share against it, and the reasons why the elderly stand at a lesser risk of contracting the virus.

Found the video interesting? There are a lot more interesting posts, images and video’s on MicrobeWorld to read or watch.

Established in 2003, MicrobeWorld is an interactive multimedia educational outreach initiative from the American Society for Microbiology, a non-profit organization that “promotes awareness and understanding of key microbiological issues to adult and youth audiences, and showcases the significance of microbes in our lives.”

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Invisible Chronic Illness: Addison’s Disease

17 08 2009

This week the Grand Round will be hosted by Invisible Illness Week, a blog dedicated to the National Invisible  Ilness Week, which runs September 14 -20, 2009. The purpose:

National Invisible Chronic Illness Awareness Week  (..) is a worldwide effort to bring together people who live with invisible chronic illness and those who love them. Organizations are encouraged to educate the general public, churches, healthcare professionals and government officials about the impact of living with a chronic illness that is not visually apparent.

The theme of the Grand Round is, not very surprisingly: Invisible chronic Illness.

I won’t write about this professionally -being a librarian-, but I will speak from my own experience.

As many of you know, I’ve the chronic illness Addison’s Disease. Not that I feel ill. It doesn’t affect me, really… Not anymore.. I think.

But many people with Addison’s disease suffer silently from this disease. And like many other diseases this disease is seldomly understood by partners, colleagues, friends ….. and doctors.

Before I explain more about Addison’s disease, first let me say that almost every disease is “invisible” to others. People can never fully understand what an illness means to someone suffering from it.

Ball-and-stick model of the cortisol (hydrocor...

Cortisol, Image via Wikipedia

Patients with Addison’s disease make no or too small amounts of cortisol, a hormone made by the adrenal cortex. Cortisol has a bad reputation as the stress hormone among many people. It doesn’t deserve this reputation as this hormone is vital to life. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte levels, and behavior (Wikipedia)

Too much of this hormone causes Cushing’s disease, too little causes Addison’s disease. If you want to know what Cushing does to your body and mind, then please read the letter of Kate when she was first diagnosed with Cushing’s, at Robin’s “Survive the Journey”.

Here, I will confine myself to Addison’s disease. It is a very good example of an invisible yet serious disease.

There are 3 forms of Addison: primary (defect in the adrenal cortex itself, often also leading to a defect in aldosteron production), secondary Addison (by a defect in the hypophysis or hypothalamus) and iatrogenic Addison (caused by overtreatment with corticosteroids)

Here some reasons why the illness, although “invisible”, can have great impact on your live.

1. Diagnosis.

Diagnosis is often a challenge, especially in patients with primary Addison, most of whom look healthy because of their pigmented skin. Nowadays, the main cause of primary Addison’s disease is immune destruction of the adrenal cortex. This has often a slow onset and in 50% of the patients the diagnosis takes more than 2, sometimes even more than 10 years [1]. 38% of the patients even experience vague complaints, that can later be attributed to Addison, during 11->30 years before diagnosis [1].

Before the diagnosis is made, people with Addison’s Disease often feel extremely tired and miserable. Even when the disease fully manifests itself the symptoms are largely vague and aspecific. The most common symptoms are fatigue, dizziness, muscle weakness, weight loss, difficulty in standing up, vomiting, anxiety, diarrhea, headache, sweating, changes in mood and personality, and joint and muscle pains. Often the symptoms aren’t taken seriously (enough) or the illness is mistaken for anorexia or depression.

My secondary Addison was the consequence of an injury to the pituitary gland as result of heavy blood loss during complicated childbirth (see previous post). The week between the cause and the diagnosis of the disease, was the most terrible week of my life. I felt awful, weak, (well I lost >3 liters of blood to start with), couldn’t give breast milk (no prolactin), and I disgusted food so much, you can’t imagine. I couldn’t get anything down my throat, only the look of it made me vomit. And I felt so bad not being able to care for the baby, but I just couldn’t. I couldn’t even stand for more then a few minutes, couldn’t walk.  And then there was unstoppable diarrhea, dizzyness, and speaking with double tongue. And practically no one took it seriously, not the gynaecologists, not the nurses, not the paediatricians, nor my friends or family.

But this was only one week. How would it have been if it durated 5 or 10 years?

2. Grieve and adaptation.

Once the disease is diagnosed you have to learn to live with a body that has let you down (grieve) and you have to learn to become confident again (adapt). You also have to find a new balance. I’ve lost a few hormones overnight (ACTH, cortisol, thyroid hormone, growth hormone, prolactin, gonadotrope hormones) and believe me, it took me a few years to feel reasonable normal again. It is quite surprising how badly I was informed. Very little information about the risk of an Addisonian crises, the dosing of cortisol under various conditions.
It was also confronting how little people wanted to know about the disease or what I had been through. Visitors after the birth wanted me to be euphoric and didn’t want me to go into any detail of what had happened. They cut me short by saying: “But you have a lovely baby”. Somebody cried that she didn’t want to hear it. So I stopped trying to speak about it.

I took no sick leave, immediately went back to work. My boss – a nephrologist, never asked after my health, not once.

As I said it took a few years before my “come-back”. I didn’t feel myself. It was as if I couldn’t think, as if my head was filled with cottonwool. Afterwards I think the main reason for improval was the reduction of the cortisol from 30 mg to 12.5 per day and the use of DHEAs plus that I regained confidence in myself.

3. Comorbidity

With cortisol I lost some other hormones which are also essential. Patients with primary Addison often miss aldosteron as well, which makes them more liable for an Addisonian crisis. Primary Addisonians may also have other immune diseases, like autoimmune thyroid disease, gonadal failure, type 1 diabetes and vitiligo.

4. Addisonian crisis

An addisonian crisis is an emergency situation, with possible fatal outcome, associated mainly with an acute deficiency of the glucocorticoid cortisol. This occurs in (extremely) stressful situations. Some Addisonpatients are more prone to it than others. You can -and should – take precautions, like wearing alert bracelets or necklaces, so that emergency personnel can identify adrenal insufficiency and provide stress doses of steroids in the event of trauma, surgery, or hospitalization.

Some Addisonians fear these crises so much that they dear not walk or run alone. Many Addison patients don’t go to a country far away, some don’t even pass the border (and you know the Netherlands aren’t that big).

5. Addison’s disease can be treated but not cured.

Addison patients are treated with corticosteroids like hydrocortisone and are substituted with other hormones that they may lack. Without treatment, the disease is lethal, with treatment the disease is not cured. I do feel all right now, but many of my fellow patients don’t. I think that the following excerpt from a Seminar of Wiebke Arlt and Bruno Allolio about adrenal insufficiency [2] makes this very clear.

Despite adequate glucocorticoid and mineralocorticoid replacement, health-related quality of life is greatly impaired in patients with primary and secondary adrenal insufficiency. Predominant complaints are fatigue, lack of energy, depression, and anxiety. In addition, affected women frequently complain about impaired libido. In a survey of 91 individuals, 50% of patients with primary adrenal insufficiency considered themselves unfit to work and 30% needed household help. In another survey of 88 individuals the number of patients who received disablility pensions was two to three times higher than in the general population. The adverse effect of chronic adrenal insufficiency on health-related quality of life is comparable to that of congestive heart failure. However, fine-tuning of glucocorticoid replacement leaves only a narrow margin for improvement, and changes in timing or dose do not result in improved wellbeing.


  1. Zelissen PM. Addison patients in the Netherlands: medical report of the survey. The Hague: Dutch Addison Society, 1994.
  2. Wiebke Arlt, Bruno Allolio. Adrenal Insufficiency, Lancet 2003; 361: 1881–93 , full text on

Earlier posts on the subject:

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