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Residual baculovirus in insect cell-derived influenza virus-like particle preparations enhances immunogenicity.

ABSTRACT: Influenza virus-like particles are currently evaluated in clinical trials as vaccine candidates for influenza viruses. Most commonly they are produced in baculovirus- or mammalian- expression systems. Here we used different vaccination schemes in order to systematically compare virus-like particle preparations generated in the two systems. Our work shows significant differences in immunogenicity between the two, and indicates superior and broader immune responses induced by the baculovirus-derived constructs. We demonstrate that these differences critically influence protection and survival in a mouse model of influenza virus infection. Finally, we show that the enhanced immunogenicity of the baculovirus-derived virus-like particles is caused by contamination with residual baculovirus which activates the innate immune response at the site of inoculation.

SUBMITTER: Margine I

PROVIDER: S-EPMC3517492 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Residual baculovirus in insect cell-derived influenza virus-like particle preparations enhances immunogenicity.

Margine Irina I Martinez-Gil Luis L Chou Yi-Ying YY Krammer Florian F

PloS one 20121207 12

Influenza virus-like particles are currently evaluated in clinical trials as vaccine candidates for influenza viruses. Most commonly they are produced in baculovirus- or mammalian- expression systems. Here we used different vaccination schemes in order to systematically compare virus-like particle preparations generated in the two systems. Our work shows significant differences in immunogenicity between the two, and indicates superior and broader immune responses induced by the baculovirus-deriv ...[more]

PMID: 23236516

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Project description:Influenza viruses express two surface glycoproteins, the hemagglutinin (HA) and the neuraminidase (NA). Anti-NA antibodies protect from lethal influenza virus challenge in the mouse model and correlate inversely with virus shedding and symptoms in humans. Consequently, the NA is a promising target for influenza virus vaccine design. Current seasonal vaccines, however, poorly induce anti-NA antibodies, partly because of the immunodominance of the HA over the NA when the two glycoproteins are closely associated. To address this issue, here we investigated whether extending the stalk domain of the NA could render it more immunogenic on virus particles. Two recombinant influenza viruses based on the H1N1 strain A/Puerto Rico/8/1934 (PR8) were rescued with NA stalk domains extended by 15 or 30 amino acids. Formalin-inactivated viruses expressing wild-type NA or the stalk-extended NA variants were used to vaccinate mice. The virus with the 30-amino-acid stalk extension induced significantly higher anti-NA IgG responses (characterized by increased in vitro antibody-dependent cellular cytotoxicity [ADCC] activity) than the wild-type PR8 virus, while anti-HA IgG levels were unaffected. Similarly, extending the stalk domain of the NA of a recent H3N2 virus enhanced the induction of anti-NA IgGs in mice. On the basis of these results, we hypothesize that the subdominance of the NA can be modulated if the protein is modified such that its height surpasses that of the HA on the viral membrane. Extending the stalk domain of NA may help to enhance its immunogenicity in influenza virus vaccines without compromising antibody responses to HA.IMPORTANCE The efficacy of influenza virus vaccines could be improved by enhancing the immunogenicity of the NA protein. One of the reasons for its poor immunogenicity is the immunodominance of the HA over the NA in many seasonal influenza virus vaccines. Here we demonstrate that, in the mouse model, extending the stalk domain of the NA protein can enhance its immunogenicity on virus particles and overcome the immunodominance of the HA without affecting antibody responses to the HA. The antibody repertoire is broadened by the extended NA and includes additional ADCC-active antibodies. Our findings may assist in the efforts toward more effective influenza virus vaccines.

Project description:BackgroundDengue is listed as a neglected tropical disease by the Center for Disease Control and Preservation, as there are insufficient integrated surveillance strategies, no effective treatment, and limited licensed vaccines. Consisting of four genetically distinct serotypes, dengue virus (DENV) causes serious life-threatening infections due to its complexity. Antibody-dependent enhancement by pre-existing cross-reactive as well as homotypic antibodies further worsens the clinical symptoms of dengue. Thus, a vaccine conferring simultaneous and durable immunity to each of the four DENV serotypes is essential to restrict its escalation. In deeply affected resource-limited countries, oral vaccination using food-grade organisms is considered to be a beneficial approach in terms of costs, patient comfort, and simple logistics for mass immunization. The current study used a mouse model to explore the immunogenicity of an oral dengue vaccine candidate prepared using whole recombinant yeast cells (WC) and cell-free extracts (CFE) from cells expressing recombinant Escherichia coli heat-labile toxin protein B-subunit (LTB) fused to the consensus dengue envelope domain III (scEDIII). Mice were treated orally with recombinant WC and CFE vaccines in 2-week intervals for 4 weeks and changes in systemic and mucosal immune responses were monitored.ResultsBoth WC and CFE dosage applications of LTB-scEDIII stimulated a systemic humoral immune response in the form of dengue-specific serum IgG as well as mucosal immune response in the form of secretory sIgA. Antigen-specific B cell responses in isolated lymphoid cells from the spleen and Peyer's patches further indicated an elevated mucosal immune response. Cellular immune response estimated through lymphocyte proliferation assay indicated higher levels in CFE than WC dosage. Furthermore, sera obtained after both oral administrations successfully neutralized DENV-1, whereas CFE formulation only neutralized DENV-2 serotype, two representative serotypes which cause severe dengue infection. Sera from mice that were fed CFE preparations demonstrated markedly higher neutralizing titers compared to those from WC-fed mice. However, WC feeding elicited strong immune responses, which were similar to the levels induced by CFE feeding after intraperitoneal booster with purified scEDIII antigen.ConclusionsCFE preparations of LTB-scEDIII produced strong immunogenicity with low processing requirements, signifying that this fusion protein shows promise as a potent oral vaccine candidate against dengue viral infection.

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Residual baculovirus in insect cell-derived influenza virus-like particle preparations enhances immunogenicity.

Publications

Residual baculovirus in insect cell-derived influenza virus-like particle preparations enhances immunogenicity.

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