XMRV Xenotropic Murine leukemia virus–Related Virus – linked with CFS

– true or not true

Anders Widell, MD, PhD, Lund University, Malmö University

Hospital, Malmö, Sweden

Xenotropic Murine Leukemia Virus Related Virus

• Xenos = Greek Stranger (e.g. compare with Xenofobia)

• Xenotropic Murine. Infect others than mice, whereas ecotropic infects, polytropic broader ”mice and men”

• MLV and XMRV are related gammaretroviruses, known for for long times.

• Belong to Gammaretroviruses

The Retrovirus Family

XMRV and suggested link to prostate cancer

• RNaseL linked cancer • Confirmed by one other group• Not confirmed by several other groups

XMRV surfaces• Lombardi et al in in Science 2009 describe a strong

association – 68 pos /101 tested between Chronic Fatigue Syndrome and presence of XMRV in CFS patients PBMCs

• Low prevalence in (3,7 %) healthy persons• Dataset provided in Science paper

– XMRV nucleic acid by RT-PCR in PBMC – XMRV antigens by Western in PBMCs– XMRV T and B cells, – 50% pts produce NT antibody– Transferrable virus to Prostate Cancer cell line. EM

Subsequent attempts to confirm Lombardis findings

• Several groups assess CFS patients using same techniques– Hong et al 0/85 Chinese CFS patients positive– Van Kuppeveld et al Dutch CFS patients– Groom et al 0/299 patients, half of them with CFS, – Heinrich et al 0/32 with CFS, nor in several other immune

suppressed patient groups incl. HIV– Tang et al 0/199 African patients with HIV– Barnes et al 0/230 patients with HIV or HCVNo confirmation

Then a possible confirmation by Lo et al in PNAS

MLV-like virus gag gene sequences LV in 41 PBMC-derived DNA samples from 37 patients meeting accepted diagnostic criteria for CFS, in 32 of 37 (86.5%) compared with only 3 of 44 (6.8%) healthy volunteer blood donors.

Sequences retained over 15 years

Criticism – Sato et al

• When CFS patients were assessed, also water gave MLV like sequences

• Was found to be associated with RNA in Invitrogen Platinum hot start mouse monoclonal against the polymerase

• Very closely related to Lo´s MLV like sequences – Lo used Platinum

Criticism - Hué et al

• XMRV sequences identical with retroviral sequences found in prostate cancer cell line 22Rv1

• XMRV specific primers amplify several cell line associated MLVs

• Many tumour call lined have been established vi grafts in mice who have plenty of MLVs

Figure 2 Phylogeny of 22Rv1 and patient derived XMRV sequences and other murine leukaemia viruses. Bayesian maximum clade credibility phylogeny of 22Rv1 cell line derived XMRV clones, patient derived XMRV sequences and other murine leukaemia viruses (A). The monophyletic cluster formed by 22Rv1 cell line derived XMRV clones and patient derived XMRVs is magnified in (B). Xenotropic MLV (MLV-X), polytropic MLV (PMLV), and modified polytropic MLV (MPMLV) were added as controls. Sequences derived from prostate cancer patients (VP and WO) and chronic fatigue syndrome patients (WPI) are indicated by red and yellow circles respectively. Gene sequences derived from 22Rv1 clones are indicated by blue squares. When full-length genomes were not available, the loci of the sequence used in the phylogenetic reconstruction are shown in brackets. APOBEC-3G/F hypermutated clones are labelled with a closed circle. The tree is rooted against AKV and Moloney MLVs. Bayesian posterior probabilities of 1.00 are indicated on the corresponding branches by a star. The scale bar represents the number of nucleotide substitutions per site.

Lessons to learn• Virus discovery and senstive PCR certainly can

generate new viral sequences• No molecular enzyme is completely free from

production or stabilizing nucleic acid• No statistical significance beats easy confirmation from

independent investigators• Earlier lessons from hepatitis non-A, non-B/HCV

– several systems appeared, got applauses and quietly disappeared

– and then came Chiron – whose data could immediately be confirmed and generate BIG money

– Industry´s living dream since then, GBV, TTV, SENV, XMRV

Further lessons

• Do not exclude an infectious mechanism for CFS – it may need other technology

• Be suspicious if the Discoverer only keeps presenting his/her original data over and over again adding nothing new – he/she has had a good lead to generate more

• “You can fool some of the People all the time, and all the People some of the Time, but never All the People All the Time” /Churchill