In the course of computer simulation study looking for active sites for the interaction between MHC II and T7 - a 12 residue long peptide of LSR2 - a recombinant fusion protein mimicing the native bacillus M.Leprae - an interesting relationship between the antigenicity of LSR2 and VIF of BIF has come to light. Computer analysis study has revealed this stretch of residue from 36 to 48 of LSR2 is highly antigenic. The experimental observation seems to confirm the role of this 12 residue peptide in antibody response. In an effort to determine whether a significant sequence level relationship exists between this and any other known protein, the sequence homology of both protein and nucleic acid was studied. It is found that this 12 residue long peptide (T7) of LSR2 is homologous with Viral Infectivity Factor (VIF) of the Bovine Immunodefiency Virus (BIV). Homology with translated nucleic acid sequence also indicate the same fact. The VIF gene which codes for this protein is known to be essential for ability of cell-free virus preparation to infect cells. These results lead to the question - whether this 12 residue long peptide which is common to both proteins play a role in their infectivity. Whether mutations in the peptide or elimination of this peptide from the protein and studying the effect of this on the diseases themselves may help in controlling them is another important question relevant to medical researchers. © 1997 Taylor & Francis Group, LLC.