ME Research UK and the Irish ME Trust have this afternoon announced that they are co-funding a study in Sweden which will explore the relationship between ME/CFS and the XMRV retrovirus.

The study is being carried out in three centres – the clinical virology section at Uppsala University Hospital, the Institution for Neuroscience and Physiology at the Sahlgrenska Academy, Gothenburg University and at the Gottfries Clinic in Mölndal. The principal investigators are Professor Jonas Blomberg and Professor Carl-Gerhard Gottfries.

In their joint announcement, Dr Neil Abbot at ME Research UK and Declan Caroll of the Irish ME Trust say:

The discovery of a retroviral link to ME/CFS, reported recently in the major journal Science (Science 2009;326(5952):530-1) has the potential to greatly advance diagnosis and treatment of the illness (see our overview essay, XMRV and ME/CFS - A stunning find.

The major finding was that DNA from the XMRV virus could be detected in the peripheral blood mononuclear cells of over two-thirds of ME/CFS patients' samples from the blood bank in the Whittemore Peterson Institute tissue repository, but in less than 4% of healthy control samples. Also, the researchers reported that XMRV proteins were being expressed in blood cells from ME/CFS patients at very high levels compared with controls, and that patient-derived XMRV was infectious and transmissible.

These findings have caught the attention of the scientific world, but the next steps are equally important. Chief among these is for independent laboratories across the world to attempt the replication of the WPI findings among their own local populations of ME/CFS patients - it's sometimes said that replication studies are where the rubber meets the road in science!

Since the WPI researchers used samples selected from several regions in the US where "outbreaks of CFS" had been documented (using patients diagnosed on CDC-1994 and Canadian Clinical criteria 2003, blood samples from patients in other areas or countries might throw up very different results. Will ME/CFS samples from other regions of the US show similar high rates of positivity? What about European samples?

This replication study is one attempt to answer this question - to establish whether XMRV nucleic acid can be found in peripheral blood mononuclear cells, plasma and serum of Swedish patients and controls. The researchers will retrospectively test previously stored patients' samples (20 Fukuda-defined ME/CFS, 20 fibromyalgia, 20 irritable bowel), and 20 controls. In addition, they will prospectively test samples from 120 ME/CFS patients (defined on the Fukuda 1994 and the Canadian 2003 criteria, similar to patients in the original 2009 report in Science) who will also have functional assessments.

The investigators are well-placed to conduct this confirmation study. Prof Blomberg is head of the Research Group of Clinical Virology at the University of Uppsala, and his research interests include human endogenous retroviruses; the links between endogenous retroviral sequences (ERVs) of the human genome and diseases such as multiple sclerosis and schizophrenia; and the development of real time PCRs for common viral infections. Prof Carl-Gerhard Gottfries is Professor Emeritus at the Sahlgrenska University Hospital, Mölndal, and founder of the Gottfries Clinic AB which was formed in Västra Götaland 1998 for patients with fibromyalgia and ME/CFS, and which is now situated in Mölndal. The unit has three doctors, nurses and medical secretaries, and it has also conducted basic clinical research, including trials of immunomodulatory therapy for FM and CFS.

The results of this important replication study should be available in the Spring/Summer of 2010.