The extracellular domain of M2 (M2e), a small ion channel membrane protein, is well conserved among different human influenza A virus strains. To improve the protective efficacy of M2e vaccines, we genetically engineered a tandem repeat of M2e epitope sequences (M2e5x) of human, swine, and avian origin influenza A viruses, which was expressed in a membrane-anchored form and incorporated in virus-like particles (VLPs). The M2e5x protein with the transmembrane domain of hemagglutinin (HA) was effectively incorporated into VLPs at a several 100-fold higher level than that on influenza virions. Intramuscular immunization with M2e5x VLP vaccines was highly effective in inducing M2e-specific antibodies reactive to different influenza viruses, mucosal and systemic immune responses, and cross-protection regardless of influenza virus subtypes in the absence of adjuvant. Importantly, immune sera were found to be sufficient for conferring protection in naive mice, which was long-lived and cross-protective. Thus, molecular designing and presenting M2e immunogens on VLPs provide a promising platform for developing universal influenza vaccines without using adjuvants.

Current influenza vaccines provide limited protection against circulating influenza A viruses. A universal influenza vaccine will eliminate the intrinsic limitations of the seasonal flu vaccines. Here we report methodology to generate double-layered protein nanoparticles as a universal influenza vaccine. Layered nanoparticles are fabricated by desolvating tetrameric M2e into protein nanoparticle cores and coating these cores by crosslinking headless HAs. Representative headless HAs of two HA phylogenetic groups are constructed and purified. Vaccinations with the resulting protein nanoparticles in mice induces robust long-lasting immunity, fully protecting the mice against challenges by divergent influenza A viruses of the same group or both groups. The results demonstrate the importance of incorporating both structure-stabilized HA stalk domains and M2e into a universal influenza vaccine to improve its protective potency and breadth. These potent disassemblable protein nanoparticles indicate a wide application in protein drug delivery and controlled release.

Lactobacillus plantarum DK119 (DK119) isolated from the fermented Korean cabbage food was used as a probiotic to determine its antiviral effects on influenza virus. DK119 intranasal or oral administration conferred 100% protection against subsequent lethal infection with influenza A viruses, prevented significant weight loss, and lowered lung viral loads in a mouse model. The antiviral protective efficacy was observed in a dose and route dependent manner of DK119 administration. Mice that were treated with DK119 showed high levels of cytokines IL-12 and IFN-γ in bronchoalveolar lavage fluids, and a low degree of inflammation upon infection with influenza virus. Depletion of alveolar macrophage cells in lungs and bronchoalveolar lavages completely abrogated the DK119-mediated protection. Modulating host innate immunity of dendritic and macrophage cells, and cytokine production pattern appeared to be possible mechanisms by which DK119 exhibited antiviral effects on influenza virus infection. These results indicate that DK119 can be developed as a beneficial antiviral probiotic microorganism.

The influenza M2 ectodomain (M2e) is poorly immunogenic and has some amino acid changes among isolates from different host species. We expressed a tandem repeat construct of heterologous M2e sequences (M2e5x) derived from human, swine, and avian origin influenza A viruses on virus-like particles (M2e5x VLPs) in a membrane-anchored form. Immunization of mice with M2e5x VLPs induced protective antibodies cross-reactive to antigenically different influenza A viruses and conferred cross protection. Anti-M2e antibodies induced by heterologous M2e5x VLPs showed a wider range of cross reactivity to influenza virus at higher levels than those by live virus infection, homologous M2e VLPs, or M2e monoclonal antibody 14C2. Fc receptors were found to be important for mediating protection by immune sera from M2e5x VLP vaccination. The present study provides evidence that heterologous recombinant M2e5x VLPs can be more effective in inducing protective M2e immunity than natural virus infection and further supports an approach for developing an effective universal influenza vaccine.

Current influenza vaccines do not provide good protection against antigenically different influenza A viruses. As an approach to overcome strain specificity of protection, this study demonstrates significantly improved long-term cross protection by supplementing split vaccines with a conserved molecular target, a repeat of the influenza M2 ectodomain (M2e) expressed on virus-like particles (M2e5x VLPs) in a membrane-anchored form. Intramuscular immunization with H1N1 split vaccine (A/California/07/2009) supplemented with M2e5x VLPs induced M2e-specific humoral and cellular immune responses, and shaped the host responses to the vaccine in the direction of T-helper type 1 responses inducing dominant IgG2a isotype antibodies as well as interferon-γ (IFN-γ) producing cells in systemic and mucosal sites. Upon lethal challenge, M2e5x VLP-supplemented vaccination lowered lung viral loads and induced long-term cross protection against H3N2 or H5N1 subtype influenza viruses over 12 months. M2e antibodies, CD4 T cells, and CD8 T cells were found to contribute to improving heterosubtypic cross protection. In addition, improved cross protection by supplemented vaccination with M2e5x VLPs was mediated via Fc receptors. The results support evidence that supplementation with M2e5x VLPs is a promising approach for overcoming the limitation of strain-specific protection by current influenza vaccination.

This study demonstrates that immunization with non-replicating virus-like particle (FFG VLP) containing RSV F and G glycoproteins together with RSV F DNA induced T helper type 1 antibody responses to RSV F similar to live RSV infection. Upon RSV challenge 21 weeks after immunization, FFG VLP vaccination induced protection against RSV infection as shown by clearance of lung viral loads, and the absence of eosinophil infiltrates, and did not cause lung pathology. In contrast, formalin-inactivated RSV (FI-RSV) vaccination showed significant pulmonary eosinophilia, severe mucus production, and extensive histopathology resulting in a hallmark of pulmonary pathology. Substantial lung pathology was also observed in mice with RSV re-infections. High levels of systemic and local inflammatory cytokine-secreting cells were induced in mice with FI-RSV but not with FFG VLP immunization after RSV challenge. Therefore, the results provide evidence that recombinant RSV FFG VLP vaccine can confer long-term protection against RSV without causing lung pathology.

Ginseng herbal medicine has been known to have beneficial effects on improving human health. We investigated whether red ginseng extract (RGE) has preventive effects on influenza A virus infection in vivo and in vitro. RGE was found to improve survival of human lung epithelial cells upon influenza virus infection. Also, RGE treatment reduced the expression of pro-inflammatory genes (IL-6, IL-8) probably in part through interference with the formation of reactive oxygen species by influenza A virus infection. Long-term oral administration of mice with RGE showed multiple immunomodulatory effects such as stimulating antiviral cytokine IFN-γ production after influenza A virus infection. In addition, RGE administration in mice inhibited the infiltration of inflammatory cells into the bronchial lumens. Therefore, RGE might have the potential beneficial effects on preventing influenza A virus infections via its multiple immunomodulatory functions.

There is no licensed vaccine against respiratory syncytial virus (RSV) since the failure of formalin-inactivated RSV (FI-RSV) due to its vaccine-enhanced disease. We investigated immune correlates conferring protection without causing disease after intranasal immunization with virus-like particle vaccine containing the RSV fusion protein ( IMPORTANCEIt has been a difficult challenge to develop an effective and safe vaccine against respiratory syncytial virus (RSV), a leading cause of respiratory disease. Immune correlates conferring protection but preventing vaccine-enhanced disease remain poorly understood. RSV F virus-like particle (VLP) would be an efficient vaccine platform conferring protection. Here, we investigated the protective immune correlates without causing disease after intranasal immunization with RSV F VLP in comparison to FI-RSV and live RSV. In addition to inducing RSV neutralizing antibodies responsible for clearing lung viral loads, we show that modulation of specific subsets of dendritic cells and CD8 T cells producing T helper type 1 cytokines are important immune correlates conferring protection but not causing vaccine-enhanced disease. R espiratory syncytial virus (RSV) is a major human pathogen that causes bronchiolitis in infants and young children, as well as serious respiratory illness in elderly and immunocompromised adults. It is estimated that approximately 3.4 million children are annually hospitalized due to RSV-related illnesses and 160,000 people die from RSV infection worldwide (1). Despite extensive attempts to develop RSV vaccines, there have been significant obstacles and challenges. This is partially due to the disastrous outcome of formalin-inactivated, alum-adjuvanted RSV (FI-RSV) vaccine in the 1960s. In this trial, children who were vaccinated with FI-RSV developed vaccine-enhanced respiratory disease (ERD) resulting in hospitalizations and two deaths during the next epidemic season (2). Atypical T helper type 2 (Th2)-biased T cell responses were reported to be associated with enhanced histopathology following experimental immunization with FI-RSV in small animals (3-5). In addition, a high rate of RSV reinfection is observed during childhood and throughout life, although RSV is effectively cleared after primary infection and both RSV-specific antibody and T-cell responses are induced (6). Illness associated with RSV reinfection includes sinus complications with upper respiratory tract infections and increased airway resistance as lower airway disease (7,8). Thus, it is suggested that a protective immune response to an ideal vaccine should differ quantitatively or qualitatively from that induced by natural infection.Virus-like particles (VLPs) have morphologies similar to live viruses in size and external structure but do not have viral genomes. It was demonstrated that intramuscular immunization of mice with Newcastle disease virus-based VLPs containing the chimeric RSV attachment (G) or both the chimeric G and the fusion (F) proteins induced protection again...