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 beta subunit of t he LFA-1 molecule) involved in syncytia formation of HIV-1-infected lymphoc ytes. Several phage clones mimicking an epitope of the CD18 cell-surface de terminant were isolated from two 9-mer random peptide phage-displayed libra ries via their binding to the CD18-specific monoclonal antibody (mAb) MHM23 , which in in vitro assay inhibits syncytia formation in HIV-1-infected cel ls. The peptide sequences displayed on phages that blocked immunolabeling o f this mAb on LFA-1-expressing cells were used to identify the epitope reco gnized 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 po tential of phage-display technology for the study of biological processes a t the basis of virus infection, but also suggest new approaches for the the rapy of AIDS.