Identification of a LFA‐1 region involved in the HIV‐1‐induced syncytia formation through phage‐display technology

We have identified a peptide region on CD18 molecule (the β subunit of the LFA‐1 molecule) involved in syncytia formation of HIV‐1‐infected lymphocytes. Several phage clones mimicking an epitope of the CD18 cell‐surface determinant were isolated from two 9‐mer random peptide phage‐displayed libraries via their binding to the CD18‐specific monoclonal antibody (mAb) MHM23, which in in vitro assay inhibits syncytia formation in HIV‐1‐infected cells. The peptide sequences displayed on phages that blocked immunolabeling of this mAb on LFA‐1‐expressing cells were used to identify the epitope recognized by mAb MHM23 by sequence comparison. On the basis of this analysis, two peptides which inhibited syncytia formation in HIV‐1‐infected cells in vitro were synthesized, thus confirming that they mimic a CD18 domain that is involved in this phenomenon. The results here presented highlight the potential of phage‐display technology for the study of biological processes at the basis of virus infection, but also suggest new approaches for the therapy of AIDS.