HTLV-I II INFECTION IN A HIGH VIRAL ENDEMIC AREA OF ZAIRE, CENTRAL-AFRICA - COMPARATIVE-EVALUATION OF SEROLOGY, PCR, AND SIGNIFICANCE OF INDETERMINATE WESTERN-BLOT PATTERN/

The frequency of indeterminate Western blot (WB) seroreactivities agai nst HTLV-I ''gag encoded proteins'' only, and the use of low specific diagnostic WB criteria led to the overestimation of HTLV-I seroprevale nce in initial studies in intertropical Africa and Papua New Guinea. I n order to clarify the meaning of such seroreactivity, 98 blood sample s of individuals from a high HTLV-I endemic area in Zaire, Central Afr ica were studied by a WB assay containing HTLV-I disrupted virions enr iched with a gp 21 recombinant protein and a synthetic peptide from th e gp 46 region (MTA-1), and by the polymerase chain reaction (PCR) wit h 3 primers pairs and 4 different HTLV-I and or HTLV-II-specific probe s. These 98 samples were taken mainly from patients with neurological diseases and from their relatives. Using stringent WB criteria, 28 ser a (29%) were considered as HTLV-I-positive, 3 as negative and 67 (68%) as indeterminate. A large proportion of these indeterminate sera woul d have been considered as HTLV-I-positive samples according to previou s low specific WB diagnostic criteria. After PCR, 35 samples (36%) wer e considered as positive for the presence of HTLV-I proviral DNA. Out of the 67 WB seroindeterminate, 10 (15%) were found HTLV-I-positive by PCR. These 10 individuals exhibited in WB multiple band reactivity wi th p19 and/or p24 (7 cases of both) associated in 6 cases with rgp 21, but never with MTA-1. No samples were found PCR-positive for HTLV-II despite the findings of 11 sera suggestive of HTLV-II by WB. These fin dings demonstrate that even in a high HTLV-I endemic area, only a mino rity (about 15%) of the WB-seroindeterminate individuals could be cons idered as infected by HTLV-I, and that very stringent WB criteria coul d lead to overlooking some infected individuals. (C) 1994 Wiley-Liss, Inc.