title: Development and application of a high-throughput microneutralization assay: lack of xenotropic murine leukemia virus-related virus and/or murine leukemia virus detection in blood donors.
abstract: BACKGROUND
  Xenotropic murine leukemia virus (MLV)-related virus (XMRV) and other related MLVs have been described with chronic fatigue syndrome and certain types of prostate cancer. In addition, prevalence rates as high as 7% have been reported in blood donors, raising the risk of transfusion-related transmission. Several laboratories have utilized microneutralization assays as a surrogate marker for detection of anti-MLV serologic responses--with up to 25% of prostate cancer patients reported to harbor neutralizing antibody responses.
  
  
  METHODS
  We developed a high-throughput microneutralization assay for research studies on blood donors using retroviral vectors pseudotyped with XMRV-specific envelopes. Infection with these pseudotypes was neutralized by sera from both macaques and mice challenged with XMRV, but not preimmune serum. A total of 354 plasma samples from blood donors in the Reno/Tahoe area were screened for neutralization.
  
  
  RESULTS
  A total of 6.5% of donor samples gave moderate neutralization of XMRV, but not control pseudotypes. However, further testing by Western blot revealed no evidence of antibodies against MLVs in any of these samples. Furthermore, no evidence of infectious virus or viral nucleic acid was observed.
  
  
  CONCLUSIONS
  A microneutralization assay was developed for detection of XMRV and can be applied in a high-throughput format for large-scale studies. Although a proportion of blood donors demonstrated the ability to block XMRV envelope-mediated infection, we found no evidence that this inhibition was mediated by specific antibodies elicited by exposure to XMRV or MLV. It is likely that this moderate neutralization is mediated through another, nonspecific mechanism.
authors.affiliation: Blood Systems Research Institute, Department of Laboratory Medicine, University of California at San Francisco, San Francisco, California 94118, USA.
authors.forename: Yanchen
authors.initials: Y
authors.lastname: Zhou
authors.forename: Imke
authors.initials: I
authors.lastname: Steffen
authors.forename: Leilani
authors.initials: L
authors.lastname: Montalvo
authors.forename: Tzong-Hae
authors.initials: TH
authors.lastname: Lee
authors.forename: Reeve
authors.initials: R
authors.lastname: Zemel
authors.forename: William M
authors.initials: WM
authors.lastname: Switzer
authors.forename: Shaohua
authors.initials: S
authors.lastname: Tang
authors.forename: Hongwei
authors.initials: H
authors.lastname: Jia
authors.forename: Walid
authors.initials: W
authors.lastname: Heneine
authors.forename: Valerie
authors.initials: V
authors.lastname: Winkelman
authors.forename: Chetankumar S
authors.initials: CS
authors.lastname: Tailor
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Graham
authors.initials: G
authors.lastname: Simmons
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral / Q000097:blood / Q000302:isolation & purification; D001782:Blood Donors / Q000706:statistics & numerical data; D045744:Cell Line, Tumor; D005260:Female; D057809:HEK293 Cells; D057166:High-Throughput Screening Assays / Q000379:methods*; D006801:Humans; D009052:Leukemia Virus, Murine / Q000276:immunology / Q000302:isolation & purification*; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D008832:Microchemistry / Q000379:methods; D041681:NIH 3T3 Cells; D009500:Neutralization Tests / Q000379:methods*; D012192:Retroviridae Infections / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology / Q000821:virology; D058008:Xenotropic murine leukemia virus-related virus / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral