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.

Abstract

Individuals reactive in antibody screening tests (ELISA) and with one or more reactions to HTLV-1 proteins on Western blotting, but lacking the criteria of a confirmed HTLV infection, are not exceptional in regions with a low prevalence of HTLV-1/-2 infections. PCR analysis of these indeterminate samples, using "diagnostic" pol and tax sets of primers, give negative results. However, expression of HTLV-1 defective proviruses with internal deletions undetectable by PCR with diagnostic primers could have taken place. Seven German HTLV-1 ELISA-reactive blood donors, who showed reactivity also in Western blots against several viral proteins, and twenty haemophiliacs, were examined by nested PCR and/or PCR/Southern hybridisation with primers designed for detection of HTLV-1 defective proviruses. No HTLV-1-specific amplification products were obtained. However, HTLV-1 defective proviruses with large internal deletions were detected in four out of five cell lines established from symptomatic HTLV-1 cases and two in HUT-102 cells. In two amplicons, short inverted rRNA sequences between gag and env fragments of HTLV-1 defective proviruses were revealed. These results do not exclude the presence of defective HTLV-1 proviruses in individuals with indeterminate serology although this is unlikely.