Xenotropic Murine Leukemia Virus Related Virus (XMRV) Informational Presentation

1. Xenotropic Murine Leukemia Virus Related Virus (XMRV)Informational Presentation BPAC meeting, July 26, 2010 Indira Hewlett, Ph. D Chief, Laboratory of Molecular Virology DETTD/CBER/FDA

2. Issue Informational presentation to provide BPAC updates on collaborative efforts of public health agencies, academia and blood establishments to evaluate whether XMRV poses a safety concern for the blood supply.

3. Identification of XMRV XMRV is a newly identified human retrovirus and the first gamma retrovirus detected in humans. XMRV is unrelated to HIV or HTLV. The virus was identified in 2006 using a viral detection microarray of highly conserved sequences of all known viruses. Since its discovery, several studies have reported conflicting findings regarding association of XMRV with disease. Association where found would not in itself necessarily imply disease causation.

4. Disease Association of XMRV Using the gene array, XMRV sequences were detected in 7/11 highly selected prostate cancer (PC) patients homozygous for RNAse L, an important molecule in the innate antiviral response. Additional studies of a broader spectrum of 334 PC cases showed that up to 6% were positive for DNA by PCR and 23% for protein expression by immuno-histochemistry. Taken together these findings suggested an association of XMRV with PC.

5. Disease Association of XMRV – con’t In 2009, a US study showed that XMRV could be detected in 67% (68/101) of patients with Chronic Fatigue Syndrome (CFS) and 3.7% (8/218) of healthy controls using PCR and serology. Viral gene sequences in this patient population and healthy controls were virtually identical to sequences from PC patients. Virus from activated peripheral blood cells and supernatant could be transmitted to susceptible prostate cancer cells in culture suggesting that it was infectious.

6. Disease Association of XMRV- con’t • In 2010, a German study reported that XMRV DNA could be detected in respiratory secretions • In this study, 329 respiratory samples were tested and positive findings were observed in: • 2.3% of 75 travelers from Asia with respiratory infections, • 3.2% (1/31) of patients with chronic obstructive pulmonary diseases • 9.9% (16/161) of immuno-suppressed patients with severe respiratory tract infections. • 3.2% (2/62) of healthy controls.

7. Lack of Disease Association of XMRV Recent studies (’09-’10) of PC patients have yielded negative findings resulting in a controversy of XMRV association with PC. Studies of 1) an Irish PC cohort of 139 patients and 2) a German cohort of 589 patients showed no evidence of XMRV by a variety of techniques. In a separate German study, 1/105 samples from non familial PC cases were found to be positive for XMRV DNA, however, 1/70 from non PC individuals were also positive.

8. Lack of Disease Association of XMRV – con’t • Several recent studies have reported negative findings of XMRV in the blood of CFS patients. • A Dutch study of 32 CFS patients showed negative results using PCR on whole blood samples. • Two UK studies, one of 186 patients and the other of 142 patients also reported negative results using PCR on whole blood of CFS patients. • A US study conducted by CDC in 51 CFS patients reported negative results using PCR and serology. • A US study of 996 men from the Chicago MACS cohort (562 HIV+ve and 434 HIV-1 –ve) reported negative results for XMRV using PCR.

9. Possible reasons for discrepant findings • Reasons for the discordant findings in the various studies are unclear at the present time • They could be due to differences in: • study populations • geographic differences in prevalence • case definition criteria and stage of illness • sensitivity and specificity of test methods • potential genetic variation of the virus • other unknown factors Additional studies are needed to evaluate the role of XMRV in disease using well standardized assays

10. Evaluation of Transfusion Risk Transmission through transfusion has not been shown but is theoretically possible since XMRV has been detected in blood cells and there is evidence of cell-free virus. A sero-prevalence study in Japanese blood donors using an in-house Western blot assay showed a prevalence of 1.7% (5/300). Preliminary studies in US donors showed 0.1% sero-prevalence (3/2851) using a research serologic assay. A CDC study of 121 US blood donors showed no evidence of XMRV by PCR and serologic testing. In a separate US study of blood donors 0/1435 and 0/44 HIV-1 +blood donors were positive for XMRV RNA and DNA

11. Animal studies of XMRV XMRV infection of rhesus macaques by intravenous inoculation showed disseminated infection and low but detectable transient viremia between 4-14 days. Seroconversion occurred between 11-14 days with titers peaking around day 95. Virus was isolated from T, B and NK cells as well as reproductive tissue. There was also evidence for virus replication in spleen, lymph nodes, lung and liver. The findings lend support to potential transfusion transmission of XMRV.

12. Assay standardization Currently there are no FDA approved assays for XMRV detection and assays used in cohort studies have not been standardized. For this purpose a Blood XMRV Scientific Working Group led by National Heart, Lung and Blood Institute (NHLBI) was established to standardize and validate assays to evaluate transfusion risk in future studies through the Retrovirus Epidemiology Study Group (REDS). Analytical and clinical reference panels have been developed to validate assays for future donor studies Coded panels are in the process of being evaluated by six laboratories including CDC, NIH, WPI, BSRI and 2 labs at FDA

13. XMRV and Blood Donation • As there is currently no evidence for XMRV transmission by transfusion or association with a transfusion transmitted disease, FDA has not established donor policy specific to XMRV. • A large survey conducted in Sweden and Denmark (SCANDAT) of 888,843 blood transfusion recipients without a prior cancer diagnosis at the index transfusion showed no increase in prostate cancer. • Furthermore, statistically significant decreased risk was observed in anatomic site-specific analysis for prostate cancer 2-4 years after transfusion.

14. XMRV and Blood donation – con’t In regard to CFS, FDA regulations require that donors should be in good health and medical directors at blood collection centers should exercise judgment in determining whether CFS patients are in good health at the time of donation. Donor deferral has been introduced in parts of Canada, Australia, New Zealand and the UK, for donors who voluntarily disclose their diagnosis of CFS. In the US, AABB has issued a bulletin (No. 10-03) recommending the use of donor education materials on CFS and indefinite deferral for donors who voluntarily disclose their CFS diagnosis.

15. Summary FDA intends to periodically update the committee on progress in our understanding of XMRV and transfusion safety. As additional data are obtained on prevalence in blood donors and transfusion risk BPAC may be asked to advise FDA on appropriate measures for maintaining the safety of the blood supply

16. BPAC presentations • The BPAC session today will include the following presentations on XMRV: • Review of studies that led to identification of XMRV and updates of relevant research. • Canadian perspective on XMRV. • Update from the Scientific working group on assay validation using XMRV panels. • Updates from PHS agencies (CDC, NCI, FDA) on their XMRV studies.