Intranasal administration of Lactobacillus rhamnosus GG protects mice from H1N1 influenza virus infection by regulating respiratory immune responses

Aims: To investigate whether intranasal Lactobacillus administration protects host animals from influenza virus (IFV) infection by enhancing respiratory immune responses in a mouse model. Methods and Results: After 3 days of intranasal exposure to Lactobacillus rhamnosus GG (LGG), BALB/c mice were infected with IFV A/PR/8/34 (H1N1). Mice treated with LGG showed a lower frequency of accumulated symptoms and a higher survival rate than control mice (P < 0·05). The YAC‐1 cell‐killing activity of lung cells isolated from mice treated with LGG was significantly greater than those isolated from control mice (P < 0·01). Intranasal administration of LGG significantly increased mRNA expression of interleukin (IL)‐1β, tumour necrosis factor (TNF) and monocyte chemotactic protein (MCP)‐1 (P < 0·01). Conclusions: These results suggest that intranasal administration of LGG protects the host animal from IFV infection by enhancing respiratory cell‐mediated immune responses following up‐regulation of lung natural killer (NK) cell activation. Significance and Impact of Study: We have demonstrated that probiotics might protect host animals from viral infection by stimulating immune responses in the respiratory tract.     

The immunogenicity of recombinant LC16mO vaccinia virus harboring HBsAg gene in mice

It was found that hepatitis B surface antigen (HBsAg) expressed by recombinant vaccinia virus (RVV), rProHBmO143, harboring HBsAg gene was immunologically similar to plasma-derived HBsAg and immunogenicity of the rProHBmO143 was possible to evaluate by the skin scarification (SS) method using BALB/c mice. When we compared the immunogenicity of 10(8) TCID50 of the rProHBmO143 by the SS method with that of 0.125 ml of the plasma-derived hepatitis B vaccine (HB vaccine) given by intraperitoneal inoculation, the anti-HBs antibody eliciting ability of its RVV was almost the same as that of the HB vaccine with maintenance of high antibody titers, and the antibody responses rose further by re-inoculation in association with HB vaccine, especially by using its RVV as a priming. Also, no virus was recovered from the liver, spleen or brain of the mice inoculated with rProHBmO143 by the SS method. Furthermore, in mice inoculated with rProHBmO143 and then inoculated with RVV harboring Japanese encephalitis virus (JEV) gene 24-weeks later, no effect was recognized on duration of anti-HBs antibody persistence while anti-JEV antibody is being produced. These results suggest that the rProHBmO143 is likely to become a practical live vaccine; a different immunization schedule to protect against hepatitis B virus and two or more kinds of RVV vaccines may be usable for the same animal or humans at intervals of some years.     

Intranasally administered Lactobacillus gasseri TMC0356 protects mice from H1N1 influenza virus infection by stimulating respiratory immune responses

We conducted a study to evaluate the possibility that intranasal administration of a new probiotic strain Lactobacillus gasseri TMC0356 (TMC0356) may protect host animals from influenza virus (IFV) infection, which was indicated by enhanced respiratory immune responses in a mouse model. After 3 days of exposure to TMC0356, BALB/c mice were intranasally infected with IFVA/PR/8/34 (H1N1). Lung cells were isolated from the tested mice and evaluated for cytotoxicity against YAC-1 cells. After intranasal treatment with TMC0356, mice showed a lower morbidity and higher survival rate compared to control mice (P < 0.05). The cytotoxicity of lung cells isolated from mice after intranasal treatment against YAC-1 cells was statistically higher than that of lung cells isolated from control mice (P < 0.05). Intranasal administration of TMC0356 significantly increased mRNA expression of interleukin (IL)-1β, tumor necrosis factor, IL-10, and monocyte chemotactic protein-1 (P < 0.01). These results suggest that intranasal administration of TMC0356 may protect the host animal from IFV infection. They also indicate that TMC0356 can enhance respiratory cell-mediated immune responses of host animals characteristically with up-regulated activation of lung natural killer cells. Further studies will evaluate the possible role of the immune stimulatory effects of TMC0356 within the protective effects of this bacterium against IFV, as observed in the present study.