Most of drugs designed to act on the target gp-120 which is the surface part of the envelope glycoprotein (Env) of HIV_1. The HIV_1 inter to the cell by temporary interaction between the viral exterior glycoprotein GP120 and human CD4 receptor. Binding to CD4 stimulate the start of a cascade of conformational changes in gp120 and gp41 that lead to the fusion of the viral with the host cell membrane. Three gp120s and gp41s combine in a trimer of heterodimers to form the envelope spike, which mediates attachment to and entry into the host cell. The binding of ligand to many cell surface receptors leads to intracellular signaling molecules termed as second messengers. Stimulation of some GPCRs and other cell-surface receptors leads to activation of secondary messengers. Blocking the CD 4 receptor access to GP 120 of HIV_1 halts Antigen presentation process at crucial step in those cell lines (CD4+/T Helper) .Attempts are made to control this. Here in this project an SCFV fragment was studied for its ability to block CD4 receptor in such a way that gp120 (HIV_1) could not get access to CD 4 receptor.