José A. Pérez

A new continuous epitope of hepatitis A virus

A new continuous epitope of hepatitis A virus (HAV) was defined in the VP3 protein. Convalescent sera recognised the synthetic peptide 3110–3121 (FWRGDLVFDFQV). The replacement of the arginine, glycine, or aspartic acid at positions 112, 113, or 114, respectively by other aminoacids induced the loss of synthetic peptide recognition by human convalescent sera, thereby confirming the presence of an epitope in the original VP3(110‐121) sequence. Shorter VP3 peptides such as VP3(110‐119), VP3(110‐117), and VP3(110‐116) and a tandem repeat of VP3(111‐116) failed to react with convalescent sera, indicating the importance of the entire peptide in the epitope structure. The maximum inhibition of human convalescent binding to HAV by the VP3(110‐121) peptide was around 60%, and 50% inhibition was achieved at a peptide concentration of 2.3–2.4 μg/ml. Antibodies generated by this peptide bound to intact HAV and neutralised its infectivity. Antipeptide antibodies inhibited convalescent serum binding to HAV. Monoclonal antibodies H7C27 and MAK‐4E7 inhibited completely binding of the antipeptide antibodies to HAV. J. Med. Virol. 54:95–102, 1998.

Minimal residual disease monitoring after allogeneic transplantation may help to individualize post-transplant therapeutic strategies in acute myeloid malignancies.

This study evaluates the prognostic value of minimal residual disease (MRD) monitoring by multiparametric flow cytometry in 41 patients with acute myeloid leukemia or myelodysplastic syndrome undergoing allogeneic transplantation. MRD assessment after transplant (day +100) allowed to discriminate different risk populations, being the most significant cut‐off value for outcome level of MRD

Conformational behavior of the HAV-VP3(110–121) peptidic sequence and synthetic analogs in membrane environments studied by CD and computational methods

The present study was undertaken to examine the structural features that may be important to explain the immunogenicity of the (110-121) peptide sequence (FWRGDLVFDFQV) of VP3 capsid protein of hepatitis A virus. A conformational analysis of the preferred conformations by CD and molecular mechanics was carried out. Present results suggest that the interaction with liposomes as biomembrane model induces and stabilizes the amphipathic beta-structure of the peptide. To study the contribution of amino acid replacements at the RGD tripeptide as well as the influence of the peptide chain length on peptide conformation, solid-phase peptide synthesis of several peptide analogs was carried out and the peptide conformation was studied using CD spectroscopy. The results show that the RGD sequence is necessary to induce the beta-structure in the presence of liposomes.

Anti‐Hepatitis A Virus Antibody Response Elicited in Mice by Different Forms of a Synthetic VP1 Peptide

Peptide VP1 (11‐25) of the capsid of hepatitis A virus was synthesized by the Fmoc‐polyamide solid phase method, and administered to mice in different forms: (1) free, (2) encapsulated in multilamellar liposomes, (3) coupled to keyhole limpet hemocyanin (KHL), and (4) incorporated into a tetrameric branched lysine core. The highest anti‐VP1 peptide responses were generated by synthetic peptides entrapped into liposomes and coupled to KLH. No anti‐HAV response was generated with the free peptide, while all the other forms induced both anti‐HAV and HAV‐neutralizing antibodies. Maximum neutralization indices were observed in ascites from mice treated with liposome‐entrapped and KLH peptides.

Surface and polarization fluorescence studies on the interaction of an RGD sequence containing a Hepatitis A virus peptide with phospholipids

Abstract The synthesis of a VP3(110–121)-HAV peptide was carried out by solid phase methodology. A physicochemical study on the interaction of this peptide with phospholipids involving lipid mono- and bilayers is described. The surface activity of the peptide is indicative of a medium hydrophobic character suggesting the potential ability of this peptide to associate with lipids. Moreover, the presence of the peptide in the incubation media of dipalmitoylphosphatidylcholine (DPPC) and DPPC/DPPG liposomes saturated with anilinonaphthalene sulphonate (ANS) or diphenylhexatriene (DPH) show a strong influence in the bilayers fluidity determined by polarization fluorescence. The presence of lipids in the gel state has a strong influence on the polarity of a Trp environment, inducing a blue shift and fluorescence intensity increases. No interaction was detected when measurements were carried out at temperatures above T c .

Conformational study of the preferred conformations of the peptide sequence VP3(110–121) of HAV by circular dichroism and molecular mechanics

A conformational analysis of the fragment 110–121 of VP3 coating protein of the hepatitis A virus was carried out using circular dichroism spectroscopy and computational studies. The latter studies indicate the tendency of the peptide to adopt hairpin-type structures. Circular dichroism experiments indicate that, in spite of the fact that the isolated peptide exhibits no structure under different experimental conditions, negatively charged liposomes induce a secondary structure that agrees with the results of the computational study.

Interactions of a tetravalent branched peptide from VP3 capsid protein of hepatitis A virus with monolayers as biomembrane models

Abstract The interactions between a synthetic multiple antigenic peptide containing four units of a peptide corresponding to the sequence (110–121) of VP3 protein of the hepatitis A virus, termed MAP 4 -VP3(110–121), and phospholipids as the main components of biological membranes have been studied in detail. Surface activity of the multiple antigenic peptide was determined as a function of its bulk concentration in an aqueous solution. Saturation was reached at 0.33 μM concentration. The ability of the peptide to insert into lipid monolayers of dipalmitoyl phosphatidylcholine, dipalmitoyl phosphatidylglycerol and stearyl amine was determined. The peptide interacts preferably with the positive phospholipid according to its negative charge.