The CFIDS Association of America hosted a webinar on Oct. 14, 2011 to
provide information about the Phase III results of the multicenter
study of XMRV known as the Blood XMRV Scientific Research Working
Group (SRWG) study.
Results of the Blood XMRV Scientific Research Working Group Study
Graham Simmons, PhD of Blood Systems Research Institute
Michael Busch, MD, PhD of Blood Systems Research Institute
Steven Kleinman, BSc, MD of University of British Columbia
Link to slides: http://www.cfids.org/xmrv/srwg-webinar-oct2011.pdf
Link to webinar recording:
From the webinar:
Answers to 10 Common Criticisms of the SRWG study
by Graham Simmons, PhD
1. All of the controls were not screened by all of the labs.
Response: Controls were screened by at least five labs: WPI, National
Cancer Insitute/NCI-Ruscetti, Food and Drug Administration/FDA-Lo,
Centers for Disease Control & Prevention (CDC) and NCI/Drug Resistance
2. Control peripheral blood mononuclear cells (PBMCs) were not
screened prior to blinding, so could not have been ruled as negative.
Response: Three out of the 15 did have their PBMCs extensively
screened prior to blinding, yet two of these were still called
"positive" in various assays by the WPI and NCI/Ruscetti in the study.
3. No cryopreservative was used for the storage of the PBMCs, which
would prevent the WPI's assay from working. No Trizol was used.
Response: Due to the short-term nature of the study it was not felt
that preservatives were required for PBMC cryopreservation. The
Lo/Alter study detected sequences in PBMCs stored for 15 years in the
absence of preservatives. Trizol is for the extraction of nucleic acid
and laboratories were given the option of choosing their own
4. The length of time allotted for the serology and culture assays was
massively reduced, so that the WPI or NCI/Ruscetti assays were not
performed as desired.
Response: All the laboratories were allowed as much time as required
to perform their desired assays. The culture and serological assays
were performed by WPI and NCI/Ruscetti to their own specifications.
5. The WPI was not given the opportunity to complete virus culture assays.
Response: The WPI encountered mycoplasma contamination of their target
cell population, and used the plasma samples without results. This was
very unfortunate. There were no further stocks left to perform repeat
cultures with. It was deemed by both the WPI and the working group
that performing the studies on freeze/thawed material would be
6. Samples and collection tubes were handled in the same laboratory as
22Rv1 cells used to spike the analytical controls.
Response: As stated in the paper, 22Rv1 cells were handled in a
separate facility to where all other activities were performed. The
fact that only one laboratory detected PCR and virus culture in
clinical samples supports the fact that 22Rv1 contamination did not
occur at the central laboratory.
7. Patients were on additional therapies that would produce false negatives.
Response: Lo/Alter patients were not on any additional treatments. It
is unclear what additional treatments patients were on at the time of
Lombardi et al. There is no published evidence that additional
treatments would have positive or negative effects.
8. FDA/Lo used the wrong assay from Lo et al. and instead used the one
that could not detect positives.
Response: Lo et al. used their own criteria to decide on which
assay(s) to use, but it is clear that both primer sets in their paper
are equally capable of amplifying diverse polytropic murine leukemia
viruses (MLVs), so it is not obvious that one would be better that the
other at detecting "positives."
9. The NCI did no PCR and could not use their clinically validated
serology and culture assays.
Response: NCI felt that they were not sufficiently experienced at PCR
to participate in the study. They did perform their serology and
culture assays – just as performed in Lombardi et al.
10. All the SRWG labs optimized their assays to VP62. VP62 does not
exist in nature and Lombardi et al. is now known to have discovered
HGRVs. Does your study include HGRVs? Or how do HGRVs relate to XMRV?
Response: As demonstrated in an earlier slide, although this study was
initiated after Lombardi et al. as a study of XMRV, as soon as Lo et
al. was published the mission of the study was broadened to include
all MLV-like viruses. Thus, almost all of the assays were designed to
perform against MLVs in general and were optimized and tested as such.
As our study has demonstrated there is no such thing as an
independently validated clinically positive sample against which to
test. Currently there is no such thing as human gammaretroviruses
(HGRV). No published virus has been isolated, cloned or sequenced from