WPI Response to another negative xmrv study

[Guest guest]

http://www.wpinstitute.org/news/news_current.html

In The News

February 18, 2010: WPI is aware of the recent UK study that was unable

to detect the presence of XMRV in any CFS patient samples. Although

researchers at the WPI were not involved in this project, our work in XMRV

continues with researchers around the world. We look forward to the results

of studies which replicate the methods used in the original research

described in the journal Science in October, 2009.

View more...

Information Regarding XMRV Studies

1. The authors of the Science paper established the existence of XMRV as

an infectious human blood borne retrovirus for the first time in blood of

patients diagnosed with Chronic Fatigue Syndrome (CFS). Previous studies had

established the presence of XMRV sequences and protein in human prostate

tissue.

2. In the Science paper, the presence of XMRV in well-characterized

patients with CFS was established using multiple technologies:

a) PCR on nucleic acids from un-stimulated and stimulated white blood

cells;

XMRV protein expression from stimulated white blood cells;

c) Virus isolation on the LNCaP cell line; and

d) A specific antibody response to XMRV.

3. The authors of the two UK studies did not attempt to ³replicate² the

WPI study. Replication requires that the same technologies be employed. The

WPI sent reagents and information to several groups of researchers in an

effort to support their replication studies. Neither UK study requested

positive control blood, plasma or nucleic acids from the WPI.

4. The collection, preparation and storage of DNA were completely

different between the Science and UK papers. The latter studies do not show

data on blood harvesting or storage. Nor do the studies disclose the

quantity of isolated cells. Insufficient number of cells analyzed may result

in failure to detect a low copy virus like XMRV, regardless of the

sensitivity of the assay. Neither UK study provides detail to allow

interpretation of how many white blood cells were analyzed.

5. Patient population selection may differ between studies.

6. The UK authors were unable to detect XMRV, even though 4% of healthy

individuals were found to be infected in the US. Japanese scientists

detected XMRV in 1.7% in healthy blood donors in Japan. The two previously

identified human retroviruses have distinct geographical distributions.

7. Perhaps the most important issue to focus on is the low level of XMRV

in the blood. XMRV is present in such a small percentage of white blood

cells that it is highly unlikely that either UK study¹s PCR method could

detect it using the methods described. Careful reading of the Science paper

shows that increasing the amount of the virus by growing the white blood

cells is usually required rather than using white blood cells directly

purified from the body. When using PCR alone, the Science authors found that

four samples needed to be taken at different times from the same patient in

order for XMRV to be detected by PCR in freshly isolated white blood cells.

More importantly, detection methods other than PCR showed that patients

whose blood lacks sufficient amount of XMRV detectable by PCR are actually

infected. This was proven by the isolation of viral proteins and the finding

of infectious XMRV isolated from the indicator cell line LNCaP. The authors

of the Retrovirology paper admit that their neutralization assay did not

detect bacterially expressed XMRV gag and that positive control sera was

needed to validate their assay. The WPI¹s monoclonal antibodies specifically

and sensitively completed the immune response demonstrating the assays

sensitivity and specificity for XMRV envelope.

Simply stated the only validated reliable methods for detecting XMRV in

CFS patients, to date, are the methods described in Science. Failure to use

these methods and validated reagents has resulted in the failure to detect

XMRV. A failure to detect XMRV is not the same as absence of this virus in

patients with CFS