-
[show abstract]
[hide abstract]
ABSTRACT: Whole inactivated virus (WIV) influenza vaccines are more immunogenic in unprimed individuals than split-virus or subunit vaccines. In mice, this superior immunogenicity has been linked to the recognition of the viral ssRNA by endosomal TLR7 receptors in immune cells, leading to IFNα production and Th1-type antibody responses. Recent data suggest that viral membrane fusion in target cell endosomes is necessary for TLR7-mediated IFNα induction. If so, virus inactivation procedures that compromise the fusion activity of WIV vaccines, like formaldehyde (FA) treatment, could potentially harm vaccine efficacy. Therefore, we measured the effect of fusion inactivation of H5N1 WIV on TLR7 activation in vitro, and on antibody isotype responses in vivo. Fusion inactivation of WIV reduced, but did not block, TLR7-dependent IFNα induction in murine dendritic cells in vitro. In vivo, fusion-inactive WIV was as potent as fusion-active WIV in inducing total H5N1-specific serum IgG and IgG2c subtype antibodies in unprimed mice. Both vaccines induced only small amounts of IgG1. However, FA treatment of WIV did reduce the capacity of the vaccine to induce hemagglutination-inhibiting (HI) antibodies. This possibly relates to modification of epitopes that are targets for HI antibodies rather than to loss of fusion activity. Antibody affinity maturation was not negatively affected by fusion inactivation. In conclusion, fusion activity of H5N1 WIV does not play a major role in Th1-type antibody induction. Yet, to preserve the full immunogenicity of WIV, or possibly also other inactivated influenza vaccines, harsh treatment with formaldehyde should be avoided.
Vaccine 07/2012; 30(45):6501-7. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: With the current global influenza vaccine production capacity the large demand for vaccines in case of a pandemic can only be fulfilled when antigen dose sparing strategies are employed. Here we used a murine challenge model to evaluate the potential of GPI-0100, a semi-synthetic saponin derivative, to serve as a dose-sparing adjuvant for influenza subunit vaccine. Balb/c mice were immunized with different doses of A/PR8 (H1N1) subunit antigen alone or in combination with varying doses of GPI-0100. The addition of GPI-0100 significantly stimulated antibody and cellular immune responses, especially of the Th1 phenotype. Furthermore, virus titers detected in the lungs of mice challenged one week after the second immunization were significantly reduced among the animals that received GPI-0100-adjuvanted vaccines. Remarkably, adjuvantation of subunit vaccine with GPI-0100 allowed a 25-fold reduction in hemagglutinin dose without compromising the protective potential of the vaccine.
Vaccine 01/2011; 29(11):2037-43. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Stockpiling of pre-pandemic influenza vaccines guarantees immediate vaccine availability to counteract an emerging pandemic. Generally, influenza vaccines need to be stored and handled refrigerated to prevent thermal degradation of the antigenic component. Requirement of a cold-chain, however, complicates stockpiling and the logistics of vaccine distribution. We, therefore, investigated the effect of elevated storage temperatures on the immunogenicity of a pre-pandemic influenza A H5N1 whole inactivated virus vaccine. Either suspended in liquid or kept as a freeze-dried powder, vaccines could be stored for 1 year at ambient temperature (20 degrees C) with minimal loss of immunogenicity in mice. Elevation of the storage temperature to 40 degrees C, however, resulted in a significant loss of immunogenic potency within 3 months if vaccines were stored in liquid suspension. In sharp contrast, freeze-dried powder formulations were stable at 40 degrees C for at least 3 months. The presence of inulin or trehalose sugar excipients during freeze-drying of the vaccine proved to be critical to maintain its immunogenic potency during storage, and to preserve the characteristic Th1-type response to whole inactivated virus vaccine. These results indicate that whole inactivated virus vaccines may be stored and handled at room temperature in moderate climate zones for over a year with minimal decline and, if converted to dry-powder, even in hot climate zones for at least 3 months. The increased stability of dry-powder vaccine at 40 degrees C may also point to an extended shelf-life when stored at 4 degrees C. Use of the more stable dry-powder formulation could simplify stockpiling and thereby facilitating successful pandemic intervention.
The AAPS Journal 03/2010; 12(2):215-22. · 5.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Clinical trials with pandemic influenza vaccine candidates have focused on aluminium hydroxide as an adjuvant to boost humoral immune responses. In this study we investigated the effect of aluminium hydroxide on the magnitude and type of immune response induced by whole-inactivated virus (WIV) vaccine. Balb/c mice were immunized once with a range of antigen doses (0.04-5 microg) of WIV produced from A/PR/8 virus, either alone or in combination with aluminium hydroxide. The hemagglutination inhibition (HI) titers of mice receiving WIV+aluminium hydroxide were 4-16-fold higher than HI titers in mice receiving the same dose of WIV alone, indicating the boosting effect of aluminium hydroxide. WIV induced a TH1 skewed humoral and cellular immune response, characterized by strong influenza-specific IgG2a responses and a high number of IFNgamma-secreting T cells. In contrast, immunization with WIV adsorbed to aluminium hydroxide resulted in skewing of this response to a TH2 phenotype (high IgG1 levels and a low number of IFNgamma-producing T cells). To assess the effect of the observed immune response skewing on viral clearance from the lungs mice immunized once with 1 microg WIV without or with aluminium hydroxide were challenged with A/PR/8 virus 4 weeks later. The immunized mice showed a significant decrease in viral lung titers compared to control mice receiving buffer. However, despite higher antibody titers, mice immunized with WIV adsorbed to aluminium hydroxide suffered from more severe weight loss and had significantly higher virus loads in their lung tissue than mice receiving WIV alone. Major difference between these groups of mice was the type of immune response induced, TH2 instead of TH1, indicating that a TH1 response plays a major role in viral clearance.
Vaccine 06/2008; 26(19):2350-9. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: For protection against (re-)infection by influenza virus not only the magnitude of the immune response but also its quality in terms of antibody subclass and T helper profile is important. Information about the type of immune response elicited by vaccination is therefore urgently needed.
The aim of the study was to evaluate in detail the immune response elicited by three current influenza vaccine formulations and to shed light on vaccine characteristics which determine this response.
Mice were immunized with whole inactivated virus (WIV), virosomes (VS) or subunit vaccine (SU). Following subsequent infection with live virus, serum antibody titers and Th cell responses were measured. The effects of the vaccines on cytokine production by conventional and plasmacytoid dendritic cells were investigated in vitro.
In Balb/c mice (Th2 prone) as well as in C57Bl/6 mice (Th1 prone), WIV induced consistently higher hemagglutination-inhibition titers and virus-neutralizing antibody titers than VS or SU. In contrast to VS and SU, WIV stimulated the production of the antibody subclasses IgG2a (Balb/c) and IgG2c (C57BL/6), considered to be particularly important for viral clearance, and activation of IFN-gamma-producing T cells. Similar to live virus, WIV stimulated the production of proinflammatory cytokines by conventional dendritic cells and IFN-alpha by plasmacytoid cells, while VS and SU had little effect on cytokine synthesis by either cell type. We conclude that vaccination with WIV in contrast to VS or SU results in the desired Th1 response presumably by induction of type I interferon and other proinflammatory cytokines.
Influenza and Other Respiratory Viruses 04/2008; 2(2):41-51. · 4.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Virosomes are reconstituted viral envelopes that can serve as vaccines and as vehicles for cellular delivery of various macromolecules. To further advance the use of virosomes, we developed a novel dialysis procedure for the reconstitution of influenza virus membranes that is easily applicable to industrial production and compatible with encapsulation of a variety of compounds. This procedure relies on the use of 1,2-dicaproyl-sn-glycero-3-phosphocholine (DCPC) as a solubilizing agent. DCPC is a short-chain lecithin with detergent-like properties and with a critical micelle concentration of 14 mM. DCPC effectively dissolved the influenza virus membranes after which the nucleocapsids could be removed by ultracentrifugation. The solubilized membrane components were reconstituted either by removal of DCPC by dialysis or by a procedure involving initial dilution of the solubilized membrane components followed by dialysis. Both protocols resulted in removal of 99.9% of DCPC and simultaneous formation of virosomes. Analysis of the virosome preparations by equilibrium sucrose density gradient centrifugation revealed co-migration of phospholipid and protein for virosomes produced by either method. Moreover, both virosome preparations showed morphological and fusogenic characteristics similar to native influenza virus. Size, homogeneity and spike density of the virosomes varied with the two different reconstitution procedures employed. The recovery of viral membrane proteins and phospholipids in the virosomes was found to be higher for the dilution/dialysis procedure than for the simple dialysis protocol. This novel procedure for the production of virosomes is straightforward and robust and allows further exploitation of virosomes as vaccines or as drug delivery vehicles not only in academia, but also in industrial settings.
Biochimica et Biophysica Acta 05/2006; 1758(4):527-36. · 4.66 Impact Factor
-
Vaccine 03/2003; 21(9-10):925-31. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Virosomes are reconstituted viral envelopes which lack the genetic material but retain the cell entry and membrane fusion characteristics of the virus they are derived from. Thus, influenza virosomes are taken up by cells via receptor-mediated endocytosis, which directs the particles to the endosomal cell compartment. Subsequently, the virosomal membrane fuses with the endosomal membrane induced by the mildly acidic pH within the endosomes. This fusion process establishes continuity between the lumen of the virosome and the cell cytosol. Upon interaction of virosomes with antigen-presenting cells (APCs), protein antigens encapsulated within virosomes will be delivered to the cell cytosol, and thus, into the MHC class I presentation pathway. Indeed, virosome-mediated delivery of antigens in vivo results in efficient priming of a class I MHC-restricted cytotoxic T lymphocyte (CTL) response.
Journal of Liposome Research 12(1-2):155-63. · 1.71 Impact Factor
