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The design of vaccines for RNA viral diseases is complicated by the high genetic variability of the viruses, which favors the selection of escape mutants. A case in point is foot-and-mouth disease virus (FMDV), for which only limited protection has been observed in vaccination with single peptides. We have explored the potential of immunogens of higher sequence diversity, covering a broad range of field or culture-induced mutations at the immunodominant site A of FMDV, serotype C. Four mixotope-type peptide libraries, containing ca. 3 × 103 or ca. 3 × 105 peptides each, in either linear or cyclic form, and combining most significant mutations found or induced at site A have been synthesized and used to immunize guinea-pigs. Substantial levels of serum conversion have been observed for all four mixotope libraries, as well as for single peptides, linear or cyclic, corresponding to the consensus site A sequence. The specificity and neutralizing ability of the anti-mixotope and -peptide antibodies have been evaluated by direct ELISA and by plaque reduction and micro-neutralization assays, respectively. Challenge experiments with an infectious, guinea-pig-adapted FMDV strain, have shown higher protection rates in animals immunized with the cyclic versions, either in single sequence or in combinatorial mixotope form. © 2004 Elsevier Ltd. All rights reserved.

To prepare liposomes containing a synthetic hepatitis A virus antigen (HAV) [VP3(110-121)] as a vaccine, the miscibility of this peptide (with negative net charge) with a neutral lipid [dipalmitoylphosphatidylcholine (DPPC)], a negatively charged lipid [dipalmitoylphosphatidylglycerol (DPPG)], and a positively charged lipid [Stearylamine (SA)] was studied through compression isotherms of monolayers. Mixtures with DPPC and SA showed a low degree of interaction with the peptide, the composition of the monolayer being stable through compression. For DPPG-containing monolayers larger positive deviations from ideality were found, and the peptide was squeezed out from the monolayer at a DPPG/VP3(110-121) mole fraction of 0.8/0.2. All this suggests that besides hydrophobic interactions between the peptide and the lipid, electrostatic forces also play a role; thus it seems that neutral and positively charged lipids would be more suitable for preparing stable liposomes with VP3(110-121). Copyright 2000 Academic Press.

Our proposal was directed to the identification of synthetic peptide mimetics corresponding to neutralizing epitopes recognized by IgG1b12 and MAb 58.2. Herein, we report recent results on MAb 58.2 which provides important new information regarding methods and outcomes for synthetic vaccines as well as specific information about the role that conformation plays in neutralizing immune responses to the V3 epitope. MAb 58.2 displays broad reactivity against Clade B gp120s from primary isolates. It weakly neutralizes a cloned macrophage-tropic primary isolate, JR-CSF. We identified a constrained V-3 loop mimetic that binds >1,000 times better to MAb 58.2 than the corresponding linear peptide. Rabbit polyclonal antibodies to the constrained peptide but not the linear peptide bind rgp120 (MN). Furthermore, the polyclonal immune response to a constrained V3 peptide mimics the conformational preference and neutralizing activity of MAb 58.2. HIV-1 neutralization correlates with conformational preference and affinity for gp120. These results and others presented in the report establish beyond doubt the remarkable improvements in antigenicity and immunogenicity of constrained peptides compared to linear peptides.