(1/62) In vitro studies of core peptide-bearing immunopotentiating reconstituted influenza virosomes as a non-live prototype vaccine against hepatitis C virus.
Evidence from both animal and human viral diseases indicate that cytotoxic T lymphocytes (CTL) are crucial in antiviral defense. However, a major problem to generate cytotoxic immunity is that in vivo exogenous antigens are usually presented via MHC class II pathway and normally fail to induce CTL. The aim of this study is to describe a novel non-live prototype vaccine based on immunopotentiating reconstituted influenza virosomes (IRIV) as vehicles to deliver HLA-A*0201-restricted hepatitis C virus (HCV) peptides (core 35-44 and 131-140) into the cytoplasm of at least three different target cell types [including T2, a transporter associated with antigen processing (TAP)-deficient cell line] resulting in MHC class I peptide presentation and lysis by peptide-specific CTL lines. Comparison of kinetics and analysis of the influence of peptide-stripping and Brefeldin A (BFA) reveal that there exists an endogenous, TAP-independent and BFA-sensitive pathway for virosomally delivered peptides. Moreover, virosomes containing influenza matrix peptide 58-66 can efficiently re-stimulate in vivo primed CTL and, importantly, IRIV containing HCV core peptides can even prime CTL from peripheral blood mononuclear cells of HCV(-) healthy blood donors in vitro. The fact that in vitro primed CTL are also able to specifically lyse target cells infected with recombinant vaccinia virus encoding the HCV core protein is of great importance for future studies based on in vivo mouse models. One of the most evident advantages of the virosomes in vivo will be their capability to protect the incorporated peptide from a large variety of degrading proteases. (+info)
(2/62) Efficacy of intranasal virosomal influenza vaccine in the prevention of recurrent acute otitis media in children.
To evaluate the efficacy of an intranasal, inactivated, virosomal subunit influenza vaccine for prevention of new episodes of acute otitis media (AOM) in children with recurrent AOM, 133 children aged 1-5 years were randomized to receive the vaccine (n=67) or no vaccination (n=66). During a 6-month period, 24 (35.8%) vaccine recipients had 32 episodes of AOM; 42 (63.6%) control subjects had 64 episodes. The overall efficacy of vaccination in preventing AOM was 43.7% (95% confidence interval, 18.6-61.1; P=.002). Children vaccinated before influenza season had a significantly better outcome than did those vaccinated after the onset of influenza season. The cumulative duration of middle ear effusion was significantly less in vaccinated children than in control subjects. Data suggest that the intranasal virosomal influenza vaccine might be considered among the options for the prevention of AOM in children <5 years old with recurrent AOM. (+info)
(3/62) Induction of parasite growth-inhibitory antibodies by a virosomal formulation of a peptidomimetic of loop I from domain III of Plasmodium falciparum apical membrane antigen 1.
Apical membrane antigen 1 (AMA-1) of Plasmodium falciparum is a leading candidate antigen for inclusion in a malaria subunit vaccine. Its ectodomain can be divided into three subdomains, each with disulfide bond-stabilized structures. Since the majority of antibodies raised against the ectodomain appear to recognize strain-specific epitopes in domain I, we attempted to develop a vaccine formulation which directs the immune response to a region that contains more conserved epitopes. Here we demonstrate that a virosomal formulation of a peptide that mimics the semiconserved loop I of domain III elicits parasite growth-inhibitory antibodies. A synthetic peptide comprising residues 446 to 490 of AMA-1 (AMA-1(446-490)) was conjugated through the N terminus to a derivative of phosphatidylethanolamine and the phosphatidylethanolamine-peptide conjugate was incorporated into immunopotentiating reconstituted influenza virosomes as a human-compatible antigen delivery system. Both cyclized and linear versions of the peptide antigen elicited antibodies which specifically bound to parasite-expressed AMA-1 in Western blotting with parasite lysates as well as in immunofluorescence assays with blood stage parasites. All 11 peptidomimetic-specific monoclonal antibodies generated were cross-reactive with parasite-expressed AMA-1. Antigen binding assays with a library of overlapping cyclic peptides covering the target sequence revealed differences in the fine specificity of these monoclonal antibodies and provided evidence that at least some of them recognized discontinuous epitopes. The two immunodominant epitopes comprised the conserved linear sequences K(459)RIKLN(464) and D(467)DEGNKKII(475). A key feature of the synthetic vaccine formulation proposed here is the display of the peptide antigen in a native-like state on the surface of the virosome. (+info)
(4/62) Successful booster antibody response up to 54 months after single primary vaccination with virosome-formulated, aluminum-free hepatitis A vaccine.
This study demonstrates that a booster dose of the virosome-formulated, aluminum-free hepatitis A vaccine Epaxal (Berna Biotech) is highly immunogenic in subjects who received a single primary dose of this vaccine 18-54 months earlier. There were no significant differences in geometric mean antibody titers (GMTs) among subjects who received the booster dose 18-29 months (GMT, 2330 mIU/mL), 30-41 months (GMT, 2395 mIU/mL), or 42-54 months (GMT, 2432 mIU/mL) after primary vaccination, indicating that delays in the administration of booster vaccination do not lead to a loss of immunogenicity. (+info)
(5/62) Peptide-loaded chimeric influenza virosomes for efficient in vivo induction of cytotoxic T cells.
Virus-specific CD8(+) T cells are thought to play an important role in resolving acute hepatitis C virus (HCV) infection as viral clearance has been associated with a strong and sustained CD8(+) T cell response. During the chronic state of HCV infection virus-specific T cells have a low frequency and a reduced responsiveness. Based on this, a therapeutic vaccine increasing the frequency of specific T cells is a promising alternative for the treatment of chronic HCV infection. We improved an existing vaccine platform based on immunopotentiating reconstituted influenza virosomes (IRIVs) for efficient delivery of peptide epitopes to the MHC class I antigen presentation pathway. IRIVs are proteoliposomes composed of phospholipids and influenza surface glycoproteins. Due to their fusogenic activity, IRIVs are able to deliver encapsulated macromolecules, e.g. peptides to immunocompetent cells. We developed a novel method based on chimeric virosomes [chimeric immunopotentiating reconstituted influenza virosomes (CIRIVs)] combining the high peptide-encapsulation capacity of liposomes and the fusion activity of virosomes. This new approach resulted in a 30-fold increase of the amount of incorporated soluble peptide compared with current preparation methods. To study the immunogenicity of chimeric virosomes HLA-A2.1 transgenic mice were immunized with CIRIVs containing the HCV Core132 peptide. Core132-CIRIVs efficiently induced specific cytotoxic and IFNgamma-producing T cells already with low peptide doses. Vaccine formulations, which include combinations of different HCV-derived CTL epitopes could be used to induce not only a strong but also a multi-specific CTL response, making them potential candidates for therapeutic and maybe prophylactic T cell vaccines in humans. (+info)
(6/62) Immune-reconstituted influenza virosome containing CD40L gene enhances the immunological and protective activity of a carcinoembryonic antigen anticancer vaccine.
The correct interaction of a costimulatory molecule such as CD40L with its contrareceptor CD40 expressed on the membrane of professional APCs, provides transmembrane signaling that leads to APC activation. This process can be exploited to significantly improve the efficacy of cancer vaccines and the outcome of a possible cancer vaccine-induced, Ag-specific CTL response. Therefore, we investigated whether a novel intranasal delivery of immune-reconstituted influenza virosomes (IRIV), assembled with the CD40L gene (CD40L/IRIV), could be used to improve protective immunity and the Ag-specific CTL response against carcinoembryonic Ag (CEA) generated with a novel vaccine constituted of IRIV assembled with the CEA gene (CEA/IRIV). Our results suggest that CD40L/IRIV was able to augment CEA-specific CTL activity and CEA-specific protective immunity induced by CEA/IRIV most likely through the induction of a CTL response associated with a Th1 phenotype. In conclusion, we provide evidence that CD40L/IRIV, by acting through the CD40L/CD40 signaling pathway, acts as an immune-adjuvant that could increase the efficacy of a CEA-specific cancer vaccine, which could provide an efficacious new strategy for cancer therapy. (+info)
(7/62) A papillomavirus-like particle (VLP) vaccine displaying HPV16 L2 epitopes induces cross-neutralizing antibodies to HPV11.
Peptides of the papillomavirus L2 minor capsid protein can induce antibodies (Ab) that neutralize a broad range of human papillomavirus (HPV) genotypes. Unfortunately, L2 is antigenically subdominant to L1 in the virus capsid. To induce a strong anti-L2 Ab response with cross-neutralizing activity to other mucosal types, chimeric virus-like particles (VLP) were generated in which HPV16 L2 neutralization epitopes (comprising L2 residues 69-81 or 108-120) are inserted within an immunodominant surface loop (between residues 133 and 134) of the L1 major capsid protein of bovine papillomavirus type 1 (BPV1). These chimeras self-assembled into pentameric capsomers, or complete VLP similar to wild type (wt) L1 protein. Immunization of rabbits with assembled particle preparations induced L2-specific serum Ab with titers 10-fold higher than those induced by cognate synthetic L2 peptides coupled to KLH. Antisera to both chimeric proteins partially neutralized HPV16 pseudovirions, confirming that both HPV16 L2 peptides define neutralization epitopes. When analyzed for the ability to cross-neutralize infection by authentic HPV11 virions, using detection of early viral RNA by RT-PCR-assays as the readout, immune serum to chimeric protein comprising L2 residues 69-81, but not 108-120, was partially neutralizing. In addition, mouse-antiserum induced by vaccinations with synthetic L2 peptide 108-120, but not 69-81, was partially neutralizing in this assay. Induction of cross-neutralization Ab by L2 epitopes displayed on chimeric VLP represents a possible strategy for the generation of broad-spectrum vaccines to protect against relevant mucosal HPV and associated neoplasia. (+info)
(8/62) Cost-effectiveness of adjuvanted influenza vaccination of healthy children 6 to 60 months of age.
This study estimated the health and economic outcomes of universal administration of a adjuvanted influenza vaccine to healthy preschool children, as compared with current immunization practice. A Markov model simulated a cohort of 3 million children and their households undergoing five influenza seasons. Assuming a vaccine uptake rate of 30%, at the current acquisition cost of Euro 5.50 per vaccine dose influenza vaccination (two doses for unprimed children) of 6- to 60-month- (5-year) old children averted more than 1 million clinical influenza episodes and saved Euro 63 million, from the perspective of the Italian society. From the perspective of the Italian health care service, influenza vaccination of 6- to 60- and of 6- to 24-month-old children cost Euro 10,000 and Euro 13,333 per quality-adjusted life year (QALY) saved, respectively. Administration of a adjuvanted influenza vaccine to children aged 6 to 60 months was highly cost-effective for the health care service and cost saving for the society. (+info)