A killer mimotope with therapeutic activity against AIDS-related opportunistic micro-organisms inhibits ex-vivo HIV-1 replication.

Casoli, Claudio; Pilotti, Elisabetta; Perno, Carlo Federico; Balestra, Emanuela; Polverini, Eugenia; Cassone, Antonio; Conti, Stefania; Magliani, Walter; Polonelli, Luciano

OBJECTIVE To verify whether a synthetic therapeutic killer decapeptide (KP), a functional mimotope of a yeast killer toxin with wide-spectrum microbicidal activity, inclusive of AIDS-related opportunistic micro-organisms, through interaction with beta-glucan receptors, which has been found to possess sequence homology with critical segments in gp160 V1/V2 and V3 loops, may also be inhibiting HIV-1 replication. METHODS Primary peripheral blood mononuclear cells (PBMCs) cultures established from HIV-1-infected patients were treated with KP in comparison with zidovudine and supernatants and cells were harvested for analysis of HIV RNA and proviral contents, respectively. Virus production in exogenous in-vitro PBMCs infection with lymphocytotropic and monocytotropic HIV-1 strains was also assessed in presence of KP by enzyme-linked immunosorbent assay HIV p24 gag antigen detection. The binding affinity of KP to CD4, CCR5 and CXCR4 was evaluated on CD4-CCR5 or CD4-CXCR4 transfected astroglioma cell lines. RESULTS KP was shown to be devoid of cytotoxicity on PBMCs and to inhibit HIV-1 replication in PBMCs of a patient in the acute phase of infection. The antiretroviral activity of KP, which proved to be more potent than zidovudine at micromolar concentrations, is abolished by beta 1,3-glucan but not by beta 1,6-glucan. Down-regulation of CCR5 co-receptor, and/or physical block of the gp120-receptor interaction are possible mechanisms of KP activity. CONCLUSION KP appears to be the first antibody-derived short peptide displaying an inhibitory activity against HIV-1 and related opportunistic micro-organisms by different mechanisms of action.