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

By: Judy A. Mikovits,1,* Vincent C. Lombardi,1 Max A. Pfost,1 Kathryn S. Hagen1 and Francis W. Ruscetti2
1Whittemore Peterson Institute; Reno, NV USA; 2Laboratory of Experimental Immunology; Cancer and Inflammation Program; National Cancer Institute-
Frederick; Frederick USA

In October 2009, we reported the first direct isolation of infectious xenotropic murine leukemia virus-related virus (XMRV). In that study, we used a combination of biological amplification and
molecular enhancement techniques to detect XMRV in more than 75% of 101 patients with chronic fatigue syndrome (CFS). Since our report, controversy arose after the publication of several studies that failed to detect XMRV infection in their CFS patient populations.

In this addenda, we further detail the multiple detection methods we used in order
to observe XMRV infection in our CFS cohort. Our results indicate that PCR from DNA of unstimulated peripheral blood mononuclear cells is the least sensitive method for detection of XMRV in subjects’ blood. We advocate the use of more than one type of assay in order to
determine the frequency of XMRV infection in patient cohorts in future studies of the relevance of XMRV to human disease.

Patient selection poses a challenge to any study of myalgic encephalomyelitis/
chronic fatigue syndrome (ME/CFS). In our October 2009 paper, samples banked
from 2006 to 2008 were selected for our study from severely disabled patients who
fulfilled the 1994 CDC Fukuda Criteria for chronic fatigue syndrome1 as well as
the 2003 Canadian Consensus Criteria (CCC) for ME/CFS.