Viral Associations with Chronic Fatigue Syndrome and the Prevalence of Artifacts.
fatigue syndrome (CFS) is a complex, heterogeneous disease affecting more than 1 million
Americans. Despite extensive research into the etiology of CFS, no definitive cause of
CFS has been determined; however, there is evidence supporting an infectious etiology.
In 2009, a study that reported 67% of CFS patients tested positive for the new
gammaretrovirus xenotropic murine l... read moreeukemia virus-related virus (XMRV), as compared to
only 3.7% of healthy controls, reignited the quest for a causative viral agent for CFS.
Confirming this high prevalence of XMRV in CFS patients would have been a major step
forward in defining CFS. Instead, we found that murine DNA contamination in human
samples or reagents can result in false-positives when using the sensitive nested PCR to
detect XMRV employed by the 2009 study. Failing to detect anti-XMRV antibodies in the
sera of patients who previously tested positive for XMRV using the nested PCR confirmed
that the samples were, in fact, false-positives. Two viruses under investigation as
possible triggers for CFS, Epstein-Barr virus (EBV) and human herpesvirus-6 (HHV-6), can
transactivate the human endogenous retrovirus-K18 (HERV- K18) env gene, whose product
encodes a superantigen (SAg). SAgs are microbial proteins that greatly over-stimulate
the immune system. Thus, these viruses could lead to induction of the HERV-K18 env SAg,
which then could lead to overstimulation of the immune system causing the symptoms of
CFS. To test this model, we first attempted to associate increased HERV-K18 env
transcripts with CFS symptom severity; however, we found HERV-K18 env expression was the
same in CFS patients as healthy controls and did not correlate with CFS symptoms. Next,
we attempted to link the ubiquitous herpesviruses already suspected as triggers to CFS
and inducers of HERV-K18 env, HHV-6 and HHV-7, to HERV-K18 env by measuring viral copy
number in CFS patients; however, viral copy number failed to correlate with HERV-K18 env
expression. Lastly, because EBV was shown to transactivate HERV-K18 env, we examined the
HERV-K18 env genotype in CFS patients with a history of EBV-infectious mononucleosis
(EBV-IM) and compared it to CFS patients without a history of EBV-IM. Patients who
develop CFS after having EBV-IM could be associated with a susceptible HERV-K18 env
genotype that is not present in other CFS patients; however, we failed to find a
genotypic difference between these CFS populations in our small cohort. Typical gene
association studies employ hundreds, if not thousands, of samples to find significance;
thus, future studies should be done on a much larger cohort. Overall, these studies
helped focus the HERV-K18 model on a more specific, stratified group of CFS patients
with high viral copy numbers of HHV-6 or HHV-7. Also, these studies helped prove,
without a doubt, that XMRV is not associated with CFS. Finally, these studies highlight
the importance of using multiple methods to confirm results of major new
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Pharmacology & Experimental Therapeutics.
Advisor: Theoharis Theoharides.
Committee: Martin Beinborn, Michael Court, and Athe Tsibris.
Keywords: Pharmacology, Immunology, and Virology.read less