title: Isolation of an in vitro transmissible agent with reverse transcriptase activity from a blood donor with a borderline-positive HIV-1 serology for more than five years.
abstract: BACKGROUND
  Reverse transcriptase (RT) is present in all infectious retrovirus particles. Sensitive RT tests should thus detect all such particles. A family of ultrasensitive RT tests, product-enhanced reverse transcriptase (PERT) assays, have been designed. Accumulated results show that (i) a first version of the PERT assay that uses microtiter/ELISA technology detects RT of only 3-11 retroviral particles, (ii) very different human and animal lenti- and oncoviruses are detected very sensitively, (iii) HIV-1 is detected as sensitively as with polymerase chain reaction (PCR) for viral RNA, and (iv) prevalence of elevated particle-associated RT in plasma of unselected Swiss blood donors was 1.9%.
  
  
  OBJECTIVE
  To investigate whether the RT activity detected in one unselected donor with a chronically elevated level of the liver enzyme alanine aminotransferase and two selected donors with chronically indeterminate or borderline-positive HIV-1 serology was due to human immunodeficiency virus (HIV) or human T-cell leukemia virus (HTLV) infection.
  
  
  METHODS
  Blood samples were tested by PCR for viral DNA and/or RNA of HIV-1, HIV-2, HTLV-1, HTLV-2, hepatitis B and C virus. Serological tests and virus cultures were also employed.
  
  
  RESULTS
  Infection with any of the above agents could not be demonstrated. Virus cultivation in one case of borderline-positive HIV-1 Western blot for more than 5 years yielded a peak of RT production that was repeatedly transmissible to fresh cells.
  
  
  CONCLUSIONS
  The findings suggest the presence of an infectious RT-positive agent, probably different from HIV-1/2 or HTLV-1/2, in a healthy individual with chronically borderline-positive HIV-1 serology. The PERT assay may detect retroviruses currently undetectable by other tests. The use of more stringent Western blot interpretation guidelines other than those of CDC or WHO is strongly recommended.
authors.affiliation: Swiss National Center for Retroviruses, University of Zurich, Gloriastr, 30, CH-8028 Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Schüpbach
authors.forename: H
authors.initials: H
authors.lastname: Pyra
authors.forename: J
authors.initials: J
authors.lastname: Jendis
authors.forename: Z
authors.initials: Z
authors.lastname: Tomasik
authors.forename: J
authors.initials: J
authors.lastname: Böni