Study at the air/water interface of a hepatitis A N-acetylated and C-amidated synthetic peptide (AcVP3(110-121)-NH₂): II. Miscibility in lipid monolayers

In the present work the pattern of miscibility between a hepatitis A virus (HAV) synthetic peptide (AcVP3110) with monolayers composed of lipids of different charge was studied. Zwitterionic (dipalmitoyl phosphatidylcholine (DPPC)), anionic (dipamitoyl phosphatidylglycerol (DPPG)), and cationic (stearylamine (SA)) lipids were studied at the air/water interface by compression isotherms. AcVP3110, a putative HAV synthetic vaccine candidate, formed stable monolayers through compression, being predominantly correlated with β-sheet conformations. Both DPPC and DPPG peptide mixtures with the peptide presented positive deviations from ideality. This behavior reveals the presence of repulsive forces between these lipids and AcVP3110, which were expected especially with DPPG, owing to the fact that both lipid and peptide have negative net charge. Mixed monolayers with SA showed low deviations from ideality, which were positive or negative depending on the amount of peptide present in the monolayer. All this suggests that in addition to playing a role in hydrophobic interactions, electrostatic forces have a major role in miscibility between AcVP3110 and membrane lipids. This is in agreement with what has been found for complete hepatitis A virus, where ionizable groups in the surface of the virus or cell play an important role in the attachment and endocytosis processes. Moreover, amidation and acetylation of the VP3(110-121) peptide sequence do not modify the recognition of this continuous epitope by anti-HAV antibodies.