Selection of human anti-human immunodeficiency virus type 1 envelope single-chain antibodies from a peripheral blood cell-based phage repertoire

Monoclonal antibodies play an important role in the development of diagnost ic assays. Instead of using hybridoma technology to isolate human immunodef iciency virus type 1-specific antibodies, a phage-displayed antibody librar y was generated from a small number(10(7)) of peripheral blood lymphocytes from a seropositive donor. Two families of single-chain antibodies (scFvs) were selected by bio-panning with the envelope precursor gp160, ELISA and c ompetition in the BIAcore system revealed that one antibody family recogniz ed a conformation-sensitive epitope within gp120, while the other antibody family was gp41-specific. The latter group had sequence similarity to antib odies recognizing the cluster III epitope of gp41, Binding of scFvs to gp16 0 could be inhibited with the donor's serum antibodies, indicating that ant ibodies with a similar specificity were circulating in the donor's blood. C ompetition experiments suggested that the epitope of the anti-gp41 antibodi es was recognized by a broad range of patients' sera: 21 out of 22 sera fro m North American and all 20 sera from African seropositive patients inhibit ed binding of scFvs, In contrast, three sera from this panel did not react with the epitope of the anti-gp120 antibodies. These data indicate that, be cause of the conserved nature of its epitope, the anti-gp41 antibody will b e suitable for diagnostic applications.