A novel M2e-multiple antigenic peptide providing heterologous protection in mice

Swine influenza viruses (SwIVs) cause considerable morbidity and mortality in domestic pigs, resulting in a significant economic burden. Moreover, pigs have been considered to be a possible mixing vessel in which novel strains loom. Here, we developed and evaluated a novel M2e-multiple antigenic peptide (M2e-MAP) as a supplemental antigen for inactivated H3N2 vaccine to provide cross-protection against two main subtypes of SwIVs, H1N1 and H3N2. The novel tetra-branched MAP was constructed by fusing four copies of M2e to one copy of foreign T helper cell epitopes. A high-yield reassortant H3N2 virus was generated by plasmid based reverse genetics. The efficacy of the novel H3N2 inactivated vaccines with or without M2e-MAP supplementation was evaluated in a mouse model. M2e-MAP conjugated vaccine induced strong antibody responses in mice. Complete protection against the heterologous swine H1N1 virus was observed in mice vaccinated with M2e-MAP combined vaccine. Moreover, this novel peptide confers protection against lethal challenge of A/Puerto Rico/8/34 (H1N1). Taken together, our results suggest the combined immunization of reassortant inactivated H3N2 vaccine and the novel M2e-MAP provided cross-protection against swine and human viruses and may serve as a promising approach for influenza vaccine development.

Protective efficacy of a high-growth reassortant swine H3N2 inactivated vaccine constructed by reverse genetic manipulation

Novel reassortant H3N2 swine influenza viruses (SwIV) with the matrix gene from the 2009 H1N1 pandemic virus have been isolated in many countries as well as during outbreaks in multiple states in the United States, indicating that H3N2 SwIV might be a potential threat to public health. Since southern China is the world's largest producer of pigs, efficient vaccines should be developed to prevent pigs from acquiring H3N2 subtype SwIV infections, and thus limit the possibility of SwIV infection at agricultural fairs. In this study, a high-growth reassortant virus (GD/PR8) was generated by plasmid-based reverse genetics and tested as a candidate inactivated vaccine. The protective efficacy of this vaccine was evaluated in mice by challenging them with another H3N2 SwIV isolate [A/Swine/Heilongjiang/1/05 (H3N2) (HLJ/05)]. Prime and booster inoculation with GD/PR8 vaccine yielded high-titer serum hemagglutination inhibiting antibodies and IgG antibodies. Complete protection of mice against H3N2 SwIV was observed, with significantly reduced lung lesion and viral loads in vaccine-inoculated mice relative to mock-vaccinated controls. These results suggest that the GD/PR8 vaccine may serve as a promising candidate for rapid intervention of H3N2 SwIV outbreaks in China.

VaxcineTM: an oil-based adjuvant for influenza vaccines

Vaccination is the method of choice for the prevention of influenza infection. However, the quantity of the antigen available, especially in the case of pandemics, often fails to meet the global demand. However, improved adjuvants can overcome this problem. Preliminary results obtained in this study revealed that one year after a single subcutaneous immunisation with influenza A H3N2 virus in an oil-based carrier, VaxcineTM, outbreed mice produced a high immunoglobulin G response that lasted for up to one year and exhibited less variation in titre compared with the response of the control group treated with alum. The haemagglutination-inhibition titres induced by VaxcineTM were also higher than those generated by alum. These data indicate that VaxcineTM is a good adjuvant candidate for seasonal influenza vaccines.

Time course of pulmonary pathology, cytokine influx and their correlation on augmentation of antigen challenge by influenza A virus infection.

A murine model of influenza A virus exacerbation of allergen induced airway inflammation, pulmonary histopathological changes, bronchoalveolar lavage fluid (BALF) analysis, cytokine influx and the time course of these events have been studied. The present study was undertaken to determine the relative contributions of Thl/Th2 cytokines to the histopathological changes in the lungs observed at 9, 12, 24 and 48 hr following antigen challenge in mice previously immunized with influenza A virus. BALF analysis of acute phase group revealed statistically significant increase in neutrophils at 9 hr, macrophages at 12 hr, lymphocytes and eosinophils at 24 hr, as compared to OVA-sensitized control mice. These changes were associated with an alteration in the levels of IL-4, IL-5 and IFN-gamma. A peak of IL-4 at 24 hr significantly enhanced bronchiolar and perivascular histopathology, whereas increased IL-5 level peaking at 24 hr was correlated with the enhanced infiltration of eosinophils in both BALF and lung tissue. There was simultaneous depletion of IL-10 an anti-inflammatory cytokine leading to persistence of pulmonary inflammation in case of acute phase group. Histopathology at 24 and 48 hr showed severe denudation of bronchiolar lining epithelium surrounded by dense chronic inflammatory infiltrate. Chronic interstitial infiltrate with focal loss of architecture, marked oedema, extravasation of RBCs from congested blood vessels and laying down of reticulin fibres was observed in acute phase. Thus, infection with influenza A virus on pre-existing asthmatic immunopathology elicits a cascade of Th2 cytokines with influx of inflammatory cells in BALF, mucosal and interstitial inflammation leading to asthma exacerbations.