HIV-proteinase is essential for proteolytic processing of the viral gag and gag-pol precursor proteins for active HIV replication in infected cells. We have shown that cerulenin, a naturally occuring antibiotic in combination with zinc, significantly inhibited HIV replication in T-cells. We also synthesized several synthetic peptides derived from the C-terminal region of HIV-proteinase sequences, and tested their ability to inhibit HIV replication in peripheral blood T-cells. Out of four peptides, one hexapeptide with the amino acid sequence Ac-gly-cys-thr-leu-asn-phe-COOH, we named MURUGA, was found to have high antiviral activity. The effective delivery of these peptides into HIV-infected T-cells, which express CD4 on their surface, was accomplished by encapsulation of peptides into liposomes conjugated with anti-CD4 antibody.