Abstract
A new assay for detecting inhibition of reverse transcriptase activity (the RT‐i REA) was developed. This assay was standardized for screening serum samples for reverse transcriptase inhibiting antibodies (RT‐iAb). High specificity (100%) and sensitivity (<98%) were achieved with samples from HIV‐negative individuals and HIV‐in‐fected individuals. The RT‐i REA was also used in a study of the titers of RT‐iAb in serum samples obtained from 33 HIV‐infected homosexual men. The results confirmed the relation between decreasing RT‐iAb levels and progression to late stages of the disease. Furthermore, a falling RT‐ iAb titer was observed in 14 of 15 individuals experiencing periods of severe clinical symptoms attributed to HIV‐activity. In 7 of the patients the decline in RT‐iAb titer began prior to severe clinical symptoms. The fall in RT‐iAb titer also correlated with a reduction in core Ab level. The core Ab level has previously been reported to be a disease progression marker with considerable prognostic value. However, whereas all patients were positive for RT‐iAb, 8 of the 33 patients did not have detectable core Ab. The use of RT‐iAb titer as a marker of disease progression is discussed.