Serological relationship between reverse transcriptases from human T-cell lymphotropic viruses defined by monoclonal antibodies. Evidence for two forms of reverse transcriptases in the AIDS-associated virus, HTLV-III/LAV.

The immunological relationship between reverse transcriptases purified from human T-cell lymphotropic viruses (HTLV-I, HTLV-II, HTLV-III) was defined using monoclonal antibodies specific for HTLV-III reverse transcriptase, secreted by a mouse/mouse hybridoma clone (4F8) developed in our laboratory. The viral proteins from HTLV-I and HTLV-II do not bear any cross-reactive epitope to antibodies secreted by this clone. These antibodies specifically cross-react with HTLV-III reverse transcriptase. The antibodies failed to neutralize the catalytic activity of reverse transcriptase; however, after immunoprecipitation with a magnetic conjugate of goat anti-mouse IgG, the residual activity was completely inhibited. This shows that the antibodies are not directed towards the catalytic active center of the enzyme. Using an immunoblotting technique (Western blotting), we have found two cross-reactive proteins with HTLV-III lysate with molecular masses of 53 and 66 kDa. This suggests that HTLV-III possesses two reverse transcriptase activities with a common determinant recognized by the same epitope.