Ribavirin attenuates the respiratory immune responses to influenza viral infection in mice.

Ribavirin is a broad-spectrum antiviral agent that is used against RNA and DNA viruses and has been reported to inhibit infection by influenza A and B virus in vitro and in vivo. Studies have shown that ribavirin can lower convalescent antibody titers in young children hospitalized with influenza. Here, we report that ribavirin administration in juvenile mice significantly attenuated respiratory immune responses, production of total IgA and hemagglutinin (HA)-specific secretory IgA responses on the mucosal surface. In contrast, systemic IgG and IgA responses were not affected. Ribavirin significantly suppressed toll-like receptor 2 and 4 expression in the lung and decreased the level of IL-1ß, IL-6, TNF-α, and IFN-γ in lung tissues of mice infected with influenza virus. Our findings suggest ribavirin appears to be able to inhibit viral replication and, as a result, TLR and cytokine expression are not up-regulated, attenuating inflammation as well as the respiratory tract's immune response.

Intranasal co-administration of 1,8-cineole with influenza vaccine provide cross-protection against influenza virus infection.

BACKGROUND: Vaccination is the most efficient means for protection against influenza. However, the various vaccines have low efficacy to protect against pandemic strains because of antigenic drift and recombination of influenza virus. Adjuvant therapy is one of the attempts to improve influenza vaccine effective cross-protection against influenza virus infection. Our previous study confirmed that 1,8-cineole inhibits the NF-κB, reduces pro-inflammatory cytokines, and relieves the pathological changes of viral pneumonia in mice infected with influenza virus. HYPOTHESIS/PURPOSE: 1,8-cineole, administered via intranasal (i.n.) route, may also have the capacity to be an adjuvant of the influenza vaccine. This study was designed to investigate the potential use of i.n. co-administration of 1,8-cineole, a major component of the Eucalyptus essential oils, with influenza vaccine and whether could provide cross-protection against influenza virus infection in a mouse model. STUDY DESIGN: I.n. co-administration of 1,8-cineole in two doses (6.25 and 12.5 mg/kg) with influenza vaccine was investigated in a mouse model in order to see whether it could provide cross-protection against influenza virus infection. METHODS: The mice were intranasally immunized three times at the 0, 7 and 14 day with vaccine containing 0.2 µg hemagglutinin (HA) and/or without 1,8-cineole. Seven days after the 3rd immunization dose, the mice were infected with 50 µl of 15 LD50 (50% mouse lethal dose) influenza virus A/FM/1/47 (H1N1). On day 6 post-infection, 10 mice per group were sacrificed to collect samples, to take the body weight and lung, and detect the viral load, pathological changes in the lungs and antibody, etc. The collected samples included blood serum and nasal lavage fluids. In addition, the survival experiments were carried out  to investigate the survival of mice. RESULTS: Mice i.n. inoculated with influenza vaccine and 12.5 mg/kg 1,8-cineole increased the production of influenza-specific serum immunoglobulin (Ig) G2a antibodies, stimulated mucosal secretive IgA (s-IgA) responses at the nasal cavity, improved the expression of respiratory tract intraepithelial lymphocytes (IELs) in the upper respiratory tract, and promoted dendritic cell (DC) maturation and the expression of co-stimulatory molecules cluster of differentiation (CD)40, CD80 and CD86 in peripheral blood. Importantly, mice that had received 1,8-cineole-supplemented influenza vaccine showed longer survival time, milder inflammation, less weight loss and mortality rate and lower lung index and viral titers compared to that of mice immunized a non-1,8-cineole-adjuvanted split vaccine. Thus, i.n. immunization with 1,8-cineole-adjuvanted vaccine induces a superior cross-protective immunity against infection with influenza than an inactivated vaccine only. CONCLUSION: These results suggest that 1,8-cineole (12.5 mg/kg) has a cross-protection against influenza virus, co-administered with inactivated influenza viral antigen in a mouse model.