Anti-HIV activities of novel synthetic peptide conjugated chitosan oligomers.

Chitosan and chitosan derived compounds are marine byproducts which have been shown to exhibit bioactivities including antibacterial, antioxidant, antidiabetic and anti-HIV. Proteins are among the most potent and selective molecules offering an endless potential of different structure and sequence preferences. The tripeptides which consist of tryptophan (W), methionine (M) and glutamine (Q) have been conjugated with chitosan oligomers. Among them QMW-COS and WMQ-COS protected C8166 cells from cell-lytic effects of HIV-1RF strain. Furthermore, these two compounds inhibited HIV-induced syncytia formation. We confirmed the decrease in viral-load in cell culture using p24 ELISA assay. To determine the specific mode of action of QMW-COS and WMQ-COS to inhibit HIV, we checked the inhibitory action of these compounds on viral reverse transcriptase and protease enzymes. However, we could not detect any inhibitory activity of conjugated compounds on recombinant reverse transcriptase and protease enzyme in vitro. When we co-cultured HIV-infected and uninfected C8166 cells, these two compounds actively inhibited the syncytia formation upon co-culture assay. Time-dependent addition of compounds and finally gp120-CD4 ELISA assay revealed that QMW-COS and WMQ-COS are bioactive compounds inhibiting HIV-induced cytopathic effects via exerting their effects on HIV entry stage.