MEASUREMENT OF LEVELS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 REVERSE-TRANSCRIPTASE (RT) AND RT ACTIVITY-BLOCKING ANTIBODY IN HUMAN SERUM BYA NEW STANDARDIZED COLORIMETRIC ASSAY

Standardization and calibration of a new colorimetric assay for detect ion of reverse transcriptase (RT) was carried out for optimal detectio n of RT activity-blocking antibody (RTb-Ab) in serum. A total of 99 of 100 Swedish and 54 of 54 African human immunodeficiency virus type 1 (HIV-1) antibody-positive individuals had RTb-Ab. The one RTb-Ab-negat ive HIV-1 serum sample from a Swedish individual was obtained early du ring seroconversion. Five of 615 HIV-1-negative sera from tumor patien ts, pregnant women, patients undergoing routine viral diagnostics, and blood donors gave false-positive results, In addition, 3 of 126 HIV-1 -negative African serum samples and 2 of 91 serum samples selected bec ause of false reactivity in other commercially available HIV antibody assays were positive for RTb-Ab. RT activity and RTb-Ab were measured in sera from newly HIV-1-infected individuals during seroconversion. P eak RT activity was usually detected between days 8 and 13 after the o nset of symptoms of primary infection. In addition, HIV-1 RTb-Ab was d etected in the same recently infected individuals in most cases within 1 month and in some cases as early as 10 to 12 days after the onset o f symptoms. A cross-reactivity study involving HIV-1 and HIV-2 RTb-Gbs and their homologous RT showed HIV-1 RTb-Ab to be highly type specifi c. None of 10 serum samples from HIV-l-infected individuals showed cro ss-reacting RTb-Ab toward HIV-2 RT, whereas 4 of 10 serum samples from HIV-2-infected patients showed cross-reactivity toward HIV-1 RT; howe ver, the cross-reactivity toward HIV-1 RT was 3,000 times lower than t hat toward its homologous RT. Future uses for the assay with reference to the recent World Health Organization proposal for other methods in stead of Western blotting (immunoblotting) for confirming HIV-1 infect ion and for methods for the diagnosis of infection as follow-up in vac cine trials are also discussed.