Defective human T-cell leukaemia virus type 1 (HTLV-1) genomes: No evidence in serologically indeterminate German blood donors but new type detected in established cell lines

Individuals reactive in antibody screening tests (ELISA) and with one or mo re reactions to HTLV-1 proteins on Western blotting, but lacking the criter ia of a confirmed HTLV infection, are not exceptional in regions with a low prevalence of HTLV-1/-2 infections. PCR analysis of these indeterminate sa mples, using "diagnostic" pol and tax sets of primers, give negative result s. However, expression of HTLV-1 defective proviruses with internal deletio ns undetectable by PCR with diagnostic primers could have taken place. Seve n German HTLV-1 ELISA-reactive blood donors, who showed reactivity also in Western blots against several viral proteins, and twenty haemophiliacs, wer e examined by nested PCR and/or PCR/Southern hybridisation with primers des igned for detection of HTLV-1 defective proviruses. No HTLV-1-specific ampl ification products were obtained. However, HTLV-1 defective proviruses with large internal deletions were detected in four out of five cell lines esta blished from symptomatic HTLV-1 cases and two in HUT-102 cells. In two ampl icons, short inverted rRNA sequences between gag and env fragments of HTLV- 1 defective proviruses were revealed. These results do not exclude the pres ence of defective HTLV-1 proviruses in individuals with indeterminate serol ogy although this is unlikely. (C) 2002 Wiley-Liss, Inc.