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The interaction between a peptide sequence from GB virus C E1 protein (E1P8) and its structural analogs (E1P8-12), (E1P8-13), and (E1P8-21) with anionic lipid membranes (POPG vesicles and POPG, DPPG or DPPC/DPPG (2:1) monolayers) and their association with HIV-1 fusion peptide (HIV-1 FP) inhibition at the membrane level were studied using biophysical methods. All peptides showed surface activity but leakage experiments in vesicles as well as insertion kinetics in monolayers and lipid/peptide miscibility indicated a low level of interaction: neither E1P8 nor its analogs induced the release of vesicular content and the exclusion pressure values (πe) were clearly lower than the biological membrane pressure (24-30 mN m(-1)) and the HIV-1 FP (35 mN m(-1)). Miscibility was elucidated in terms of the additivity rule and excess free energy of mixing (GE). E1P8, E1P8-12 and E1P8-21 (but not E1P8-13) induced expansion of the POPG monolayer. The mixing process is not thermodynamically favored as the positive GE values indicate. To determine how E1 peptides interfere in the action of HIV-1 FP at the membrane level, mixed monolayers of HIV-1 FP/E1 peptides (2:1) and POPG were obtained. E1P8 and its derivative E1P8-21 showed the greatest HIV-1 FP inhibition. The LC-LE phase lipid behavior was morphologically examined via fluorescence microscopy (FM) and atomic force microscopy (AFM). Images revealed that the E1 peptides modify HIV-1 FP-lipid interaction. This fact may be attributed to a peptide/peptide interaction as indicated by AFM results. Finally, hemolysis assay demonstrated that E1 peptides inhibit HIV-1 FP activity., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Three synthetic peptide sequences of 18 amino acid each, corresponding to different fragments of the E2 capsid protein of GB virus C (GBV-C): SDRDTVVELSEWGVPCAT (P45), GSVRFPFHRCGAGPKLTK (P58) and RFPFHRCGAGPKLTKDLE (P59) have been characterized in order to find a relationship between their physicochemical properties and the results obtained in cellular models. Experiments were performed in presence and absence of the HIV fusion peptide (FP-HIV) due to the evidences that GBV-C inhibits AIDS progression. P45 peptide showed lower surface activity and less extent of penetration into 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS) (3:2, mol/mol) lipid monolayers than P58 and P59. However, P45 peptide presented higher capacity to inhibit FP-HIV induced cell-cell fusion than the other two sequences. These results were supported by fluorescence anisotropy measurements which indicated that P45 had a significant effect on the inhibition of FP-HIV perturbation of liposomes of the same lipid composition. Finally, atomic force microscopy (AFM) studies have evidenced the modification of the changes induced by the FP-HIV in the morphology of lipid bilayers when P45 was present in the medium., (Copyright © 2014 Elsevier B.V. All rights reserved.)