HTLV-I among Northern Territory blood donors.

Objective: Human T-lymphotropic virus type I (HTLV-I) is known to be endemic among Northern Territory (NT) Aborigines, therefore evidence was sought of HTLV-I infection in NT blood donors.

Design: Samples were screened for HTLV-I antibodies using the Serodia HTLV-I particle-agglutination assay. Repeatedly reactive sera were tested by western blot. Viro- logical and molecular investigations were also performed. SERA: Aliquots from all 11,121 blood donations collected between June 1991 and August 1992.

Results: Four (0.036% of total) blood donations, each from different donors, were repeatedly reactive by particle-agglutination assay. One (0.009%) sample, from a 52-year-old non-Aboriginal man with no verified risk factors, was confirmed as HTLV-I seropositive by western blot. A viral isolate and a 431 base pair polymerase chain reaction product from the env gene were obtained from a culture of his peripheral blood mononuclear cells. Sequencing of the polymerase chain reaction product demonstrates that this isolate is a prototype strain and not the variant identified among Aborigines. The remaining three repeatedly reactive donors, including the positive donor's wife, were western blot indeterminate.

Conclusions: There is a low prevalence of HTLV-I carriage among blood donors in the NT, and presumably in other States. However, most repeatedly reactive donations prove to be western blot indeterminate, therefore additional tests are required to detect or exclude HTLV-I infection. Although universal screening of donations would virtually eliminate HTLV-I transmission by transfusion, it has disadvantages, including financial cost.