Monoclonal antibodies to native HIV type 1 reverse transcriptase and theirinteraction with enzymes from different subtypes

Recombinant reverse transcriptase (RT) from HIV-1 subtype B was used to pro duce mouse anti-RT monoclonal antibodies (MAbs). Immunization was done by m ixing RT with the ISCOM matrix-forming adjuvant saponin (Quil A). Two diffe rent assays, both based on the interaction of native RT and antibodies, wer e used to monitor the immune response in mice and for screening, selection, and characterization of the MAbs. The first assay measures the capacity of antibodies to inhibit the polymerase activity of the RT and the second ass ay measures the ability of antibodies to capture enzymatically active RT. T welve clones with the capacity to inhibit at least 50% of the RT activity a nd 34 clones with high RT-capturing capacity were found. The MAb panel was utilized to evaluate the immunological properties of 18 different RTs repre senting 9 different HIV-1 subtypes. The RT-inhibitory MAbs could be divided into two groups based on their pattern of cross-reactivity toward the diff erent HIV-1 RTs. The degree of diversity recorded among MAbs with RT-captur ing capacity was larger. At least seven groups of MAbs with distinct cross- reactivity patterns were identified. Thus, the degree of isoenzyme specific ity varied greatly, from MAbs that were quite specific for subtype B RT to one MAb that was able to capture the RTs from all HIV-1 isolates tested exc ept one of the two group O isolates. In conclusion, our study revealed that there exist surprisingly large immunological differences between RTs from different HIV-1 subtypes as well as from the same subtype.