Supplementation of seasonal vaccine with multi-subtype neuraminidase and M2 ectodomain virus-like particle improves protection against homologous and heterologous influenza viruses in aged mice

The conventional inactivated split seasonal influenza vaccine offers low efficacy, particularly in the elderly and against antigenic variants. Here, to improve the efficacy of seasonal vaccination for the elderly population, we tested whether supplementing seasonal bivalent (H1N1 + H3N2) split (S) vaccine with M2 ectodomain repeat and multi-subtype consensus neuraminidase (NA) proteins (N1 NA + N2 NA + flu B NA) on a virus-like particle (NA-M2e) would induce enhanced cross-protection against different influenza viruses in aged mice. Immunization with split vaccine plus NA-M2e (S + NA-M2e) increased vaccine-specific IgG antibodies towards T-helper type 1 responses and hemagglutination inhibition titers. Aged mice with NA-M2e supplemented vaccination were protected against homologous and heterologous viruses at higher efficacies, as evidenced by preventing weight loss, lowering lung viral loads, inducing broadly cross-protective humoral immunity, and IFN-γ+ CD4 and CD8 T cell responses than those with seasonal vaccine. Overall, this study supports a new strategy of NA-M2e supplemented vaccination to enhance protection against homologous and antigenically different viruses in the elderly.

Comparison of the effects of different potent adjuvants on enhancing the immunogenicity and cross-protection by influenza virus vaccination in young and aged mice

Vaccination against influenza viruses suffers from low efficacy in conferring homologous and cross-protection, particularly in older adults. Here, we compared the effects of three different adjuvant types (QS-21+MPL, CpG+MPL and bacterial cell wall CWS) on enhancing the immunogenicity and homologous and heterosubtypic protection of influenza vaccination in young adult and aged mouse models. A combination of saponin QS-21 and monophosphoryl lipid A (QS-21+MPL) was most effective in inducing T helper type 1 (Th1) T cell and cross-reactive IgG as well as hemagglutination inhibiting antibody responses to influenza vaccination. Both combination adjuvants (QS-21+MPL and CpG+MPL) exhibited high potency by preventing weight loss and reducing viral loads and enhanced homologous and cross-protection by influenza vaccination in adult and aged mouse models. Bacillus Calmette-Guerin cell-wall skeleton (CWS) displayed substantial adjuvant effects on immune responses to influenza vaccination but lower adjuvant efficacy in inducing Th1 IgG responses, cross-protection in adult mice, and in conferring homologous protection in aged mice. This study has significance in comparing the effects of potent adjuvants on enhancing humoral and cellular immune responses to influenza virus vaccination, inducing homologous and cross-protection in adult and aged populations.

Intranasal Immunization Using CTA1-DD as a Mucosal Adjuvant for an Inactivated Influenza Vaccine

OBJECTIVE

To evaluate the effect of intranasal immunization with CTA1-DD as mucosal adjuvant combined with H3N2 split vaccine.

METHODS

Mice were immunized intranasally with PBS (negative control), or H3N2 split vaccine (3 μg/mouse) alone, or CTA1-DD (5 μg/mouse) alone, or H3N2 split vaccine (3 μg/mouse) plus CTA1-DD (5 μg/mouse). Positive control mice were immunized intramuscularly with H3N2 split vaccine (3 μg/mouse) and alum adjuvant. All the mice were immunized twice, two weeks apart. Then sera and mucosal lavages were collected. The specific HI titers, IgM, IgG, IgA, and IgG subtypes were examined by ELISA. IFN-γ and IL-4 were test by ELISpot. In addition, two weeks after the last immunization, surivival after H3N2 virus lethal challenge was measured.

RESULTS

H3N2 split vaccine formulated with CTA1-DD could elicit higher IgM, IgG and hemagglutination inhibition titers in sera. Furthermore, using CTA1-DD as adjuvant significantly improved mucosal secretory IgA titers in bronchoalveolar lavages and vaginal lavages. Meanwhile this mucosal adjuvant could enhance Th-1-type responses and induce protective hemagglutination inhibition titers. Notably, the addition of CTA1-DD to split vaccine provided 100% protection against lethal infection by the H3N2 virus.

CONCLUSION

CTA1-DD could promote mucosal, humoral and cell-mediated immune responses, which supports the further development of CTA1-DD as a mucosal adjuvant for mucosal vaccines.

Green tea cultivar 'Benifuuki' potentiates split vaccine-induced immunoglobulin A production

Influenza is a widespread disease caused by infection with the influenza virus. Vaccination is considered to be the main countermeasure against influenza. A split vaccine is widely used to avoid severe adverse events, and it induces strong humoral immunity. However, the split vaccine alone cannot elicit mucosal immunity, including IgA production, and its preventative effects are limited. Here, we show that the green tea cultivar 'Benifuuki' extract enhanced the effect of a split vaccine on mucosal immunity. The frequency of IgA⁺ cells was increased in lung and Peyer's patch that received Benifuuki diet. Secretion of hemagglutinin-specific mucosal IgA, which is closely linked to the prevention of viral infection, was significantly increased in the bronchoalveolar lavage fluid of split vaccine-immunized BALB/c mice that were administered green tea Benifuuki extract. Our findings suggest that Benifuuki intake enhanced the effects of the split vaccine on mucosal immunity.

Analysis of the immunogenicity and bioactivities of a split influenza A/H7N9 vaccine mixed with MF59 adjuvant in BALB/c mice

The H7N9 influenza virus caused significant mortality and morbidity in humans during an outbreak in China in 2013. A recombinant H7N9 influenza seed with hemagglutinin (HA) and neuraminidase (NA) gene segments from A/Zhejiang/DTID-ZJU01/2013(H7N9) and six internal protein gene segments from A/Puerto Rico/8/34(H1N1; PR8) were generated using reverse genetics. We sought to determine the immunogenic, protective properties, and mechanisms of a split avian influenza A/H7N9 vaccine mixed with MF59 adjuvant in comparison to vaccines that included other adjuvant. BALB/c mice were vaccinated with two doses of different amounts and combinations of this novel A/ZJU01/PR8/2013 split vaccine with adjuvant. Mice were subsequently challenged with A/Zhejiang/DTID-ZJU01/2013(H7N9) by intranasal inoculation. We verified that MF59 enhanced the HI, MN, and IgG antibody titers to influenza antigens. Compared with alum, MF59 could more potentially induce humoral immune responses and Th2 cytokine production after virus infection, while both MF59 and alum can slightly increase NK cell activity. This split H7N9 influenza vaccine with MF59 adjuvant could effectively induce antibody production and protect mice from H7N9 virus challenge. We have selected this vaccine for manufacture and future clinical studies to protect humans from H7N9 virus infection.

Co-immunization with tandem repeat heterologous M2 extracellular proteins overcomes strain-specific protection of split vaccine against influenza A virus

Current influenza vaccines are less efficacious against antigenically different influenza A viruses. This study presents an approach to overcome strain-specific protection, using a strategy of co-immunization with seasonal H3N2 split vaccine and yeast-expressed soluble proteins of a tandem repeat containing heterologous influenza M2 ectodomains (M2e5x). Co-immunization with both vaccines in mice was superior to either vaccine alone in inducing cross protection against heterologous H3N2 virus by raising M2e-specific humoral and cellular immune responses toward a T-helper type 1 profile inducing IgG2a isotype antibodies as well as interferon-γ-producing cells in systemic and mucosal sites. In addition, co-immunization sera were found to confer cross-protection against different subtypes of H1N1 and H5N1 influenza A viruses in naïve mice. A mechanistic study provides evidence that activation of dendritic cells by co-stimulation with M2e5x and split vaccine was associated with the proliferation of CD4(+) T cells. Our results suggest that a strategy of co-immunization with seasonal split and M2e5x protein vaccines could be a promising approach for overcoming the limitation of strain-specific protection by current influenza vaccination.

Seasonal split influenza vaccine induced IgE sensitization against influenza vaccine

Although anaphylaxis is an extremely rare vaccine-associated adverse event, it occurred in young children following administration of the 2011/12 seasonal split influenza vaccine, which contained 2-phenoxyethanol as the preservative. These children had high levels of IgE antibodies against influenza vaccine components. We herein investigated why these children were sensitized. One hundred and seventeen series of serum samples were obtained immediately before, and one month after the first and second immunizations with the HA split vaccine of 2011/12. Forty-two sequential serum samples were collected in the acute and convalescent phases (2 and 4 weeks) after natural infection with H1N1 Pdm in 2009. IgE antibodies developed following the vaccination of young children with seasonal split vaccines, whereas no significant IgE response was observed following natural infection with H1N1 Pdm 2009. The prevalence of IgE antibodies was not influenced by outbreaks of H1N1 Pdm. Repeated immunization with the HA split vaccine induced IgE sensitization against the influenza vaccine irrespective of the H1N1, H3N2, or B influenza subtypes. The reasons why anaphylaxis only occurred in recipients of the influenza vaccine containing 2-phenoxyethanol are still being investigated, and the size distribution of antigen particles may have shifted to a slightly larger size. Since the fundamental reason was IgE sensitization, current split formulation for the seasonal influenza vaccine needs to be reconsidered to prevent the induction of IgE sensitization.