Influenza Virus Infection In Mice Research Articles

Oral administration of heat-killed Lactobacillus pentosus strain b240 augments protection against influenza virus infection in mice

Host-defense mechanisms against influenza virus (IFV) infection involve both innate and acquired immunities. Among other components, secretory immunoglobulin A (SIgA) in the airway mucosa plays a particularly pivotal role in preventing IFV infection. Among 150 strains of lactic acid bacteria, Lactobacillus pentosus strain b240 (b240) has the highest IgA-inducing potency in mouse Peyer's patch cells. We previously reported a practical new finding that oral ingestion of nonviable heat-killed b240 elevates salivary IgA secretion in humans. The present study aimed to determine if nonviable b240 can prevent IFV infection in mice.In a BALB/c mouse model infected with lethal levels of IFV A/PR8/34 (H1N1), oral administration of b240 for 3weeks by gavage prior to IFV infection significantly prolonged the survival period. For IFV infection at nonlethal levels, the infectious titers of IFV in the lungs 7days after infection were significantly reduced after similar b240 administration. Both anti-IFV IgA and immunoglobulin G titers in bronchoalveolar lavage fluid and plasma on day 7 were significantly higher in the b240-treated group than the control group. The augmentation of the anti-IFV immune response by b240 application was preliminarily confirmed by the elevated production of IFV-driven T-cell factors during mixed lymphocyte reactions with b240-primed splenocytes.These results suggest that oral nonviable heat-killed b240 intake can facilitate protection against IFV infection.

Inhibition of lectin‐mediated innate host defences in vivo modulates disease severity during influenza virus infection

Host-mediated recognition of mannose-rich glycans on the surface of pathogens represents an ancient mechanism of innate immune defence. In this study, we demonstrate that the virus strains that differ in the degree of N-linked glycosylation on the globular head of their hemagglutinin glycoprotein also differed in their (i) sensitivity to neutralization by a mannose-specific lectin in mouse lung fluids and (ii) ability to infect (and, therefore, to be destroyed) by airway macrophages. Virus strain BJx109 (H3N2), but not PR8 (H1N1), was sensitive to neutralization by mouse lung fluids and infected airway macrophages efficiently in vitro and these antiviral activities were blocked by mannan, a complex polymer of mannose residues. Although intranasal (i.n.) infection of mice with PR8 led to severe disease and mortality, mice infected with an equivalent dose of BJx109 displayed no signs of disease. However, i.n. treatment of BJx109-infected mice with mannan led to viral pneumonia, severe disease and death characterized by excessive virus replication, pulmonary inflammation, vascular leak and lung edema. Thus, when mannose-specific innate defences were inhibited in vivo, virus strain BJx109 induced severe viral pneumonia similar to that of PR8. Together, these findings highlight the importance of N-linked glycans as a target for recognition and destruction of influenza viruses by the innate immune system. Moreover, soluble and cell-associated lectins coordinate to modulate disease severity following influenza virus infection of mice.

Transforming Growth Factor-β: Activation by Neuraminidase and Role in Highly Pathogenic H5N1 Influenza Pathogenesis

Transforming growth factor-beta (TGF-β), a multifunctional cytokine regulating several immunologic processes, is expressed by virtually all cells as a biologically inactive molecule termed latent TGF-β (LTGF-β). We have previously shown that TGF-β activity increases during influenza virus infection in mice and suggested that the neuraminidase (NA) protein mediates this activation. In the current study, we determined the mechanism of activation of LTGF-β by NA from the influenza virus A/Gray Teal/Australia/2/1979 by mobility shift and enzyme inhibition assays. We also investigated whether exogenous TGF-β administered via a replication-deficient adenovirus vector provides protection from H5N1 influenza pathogenesis and whether depletion of TGF-β during virus infection increases morbidity in mice. We found that both the influenza and bacterial NA activate LTGF-β by removing sialic acid motifs from LTGF-β, each NA being specific for the sialic acid linkages cleaved. Further, NA likely activates LTGF-β primarily via its enzymatic activity, but proteases might also play a role in this process. Several influenza A virus subtypes (H1N1, H1N2, H3N2, H5N9, H6N1, and H7N3) except the highly pathogenic H5N1 strains activated LTGF-β in vitro and in vivo. Addition of exogenous TGF-β to H5N1 influenza virus–infected mice delayed mortality and reduced viral titers whereas neutralization of TGF-β during H5N1 and pandemic 2009 H1N1 infection increased morbidity. Together, these data show that microbe-associated NAs can directly activate LTGF-β and that TGF-β plays a pivotal role protecting the host from influenza pathogenesis.

Classical swine H1N1 influenza viruses confer cross protection from swine-origin 2009 pandemic H1N1 influenza virus infection in mice and ferrets

The hemagglutinin of the 2009 pandemic H1N1 influenza virus is a derivative of and is antigenically related to classical swine but not to seasonal human H1N1 viruses. We compared the A/California/7/2009 (CA/7/09) virus recommended by the WHO as the reference virus for vaccine development, with two classical swine influenza viruses A/swine/Iowa/31 (sw/IA/31) and A/New Jersey/8/1976 (NJ/76) to establish the extent of immunologic cross-reactivity and cross-protection in animal models. Primary infection with 2009 pandemic or NJ/76 viruses elicited antibodies against the CA/7/09 virus and provided complete protection from challenge with this virus in ferrets; the response in mice was variable and conferred partial protection. Although ferrets infected with sw/IA/31 virus developed low titers of cross-neutralizing antibody, they were protected from pulmonary replication of the CA/7/09 virus. The data suggest that prior exposure to antigenically related H1N1 viruses of swine-origin provide some protective immunity against the 2009 pandemic H1N1 virus.

Intranasal Delivery of an IgA Monoclonal Antibody Effective against Sublethal H5N1 Influenza Virus Infection in Mice

Highly pathogenic avian H5N1 influenza viruses are endemic in poultry in Asia and pose a pandemic threat to humans. Since the deployment of vaccines against a pandemic strain may take several months, adequate antiviral alternatives are needed to minimize the effects and the spread of the disease. Passive immunotherapy is regarded as a viable alternative. Here, we show the development of an IgA monoclonal antibody (DPJY01 MAb) specific to H5 hemagglutinin. The DPJY01 MAb showed a broad hemagglutination inhibition (HI) profile against Asian H5N1 viruses of clades 0, 1.0, 2.1, 2.2, and 2.3 and also against H5 wild bird influenza viruses of the North American and Eurasian lineages. DPJY01 MAb displayed also high neutralization activity in vitro and in vivo. In mice, DPJY01 MAb provided protection via a single dose administered intranasally before or after inoculation with a sublethal dose of H5N1 viruses of clades 1.0 and 2.2. Pretreatment with 50 mg of DPJY01 MAb kg of body weight at either 24, 48, or 72 h before highly pathogenic H5N1 virus (A/Vietnam/1203/2004 [H5N1]) inoculation resulted in complete protection. Treatment with 50 mg/kg at either at 24, 48, or 72 h after H5N1 inoculation provided 100%, 80%, and 60% protection, respectively. These studies highlight the potential use of DPJY01 MAb as an intranasal antiviral treatment for H5N1 influenza virus infections.

Interferon-β modulates type 1 immunity during influenza virus infection

Influenza viruses are important human pathogens, associated throughout history with worldwide outbreaks and pandemics. The antiviral effects of interferon (IFN)-αs/β against influenza virus infections are well recognized, yet the mechanisms whereby IFNs exert their immunomodulatory effects on an anti-influenza response remain ill-defined. Here, we describe the effects of IFN-β treatment on the immune response during a respiratory influenza (A/WSN/33) A virus infection of mice. A single dose of IFN-β (1 × 10 5 U) enhanced DC migration into the draining lymph node (DLN) on day 3 post-intranasal infection, and subsequently inhibited the migration from the lungs into the DLN of a newly identified late activator antigen-presenting cell population associated with type 2 immunity, LAPC. IFN-β treatment polarized the immune response towards a type 1 immune response, eliciting enhanced T H1 effector and cytolytic T cell responses, but diminished T H2 effector T cell responses in both the DLN and lung tissues of influenza virus-infected mice. Associated with the polarization towards a type 1 immune response, IFN-β treatment of mice resulted in accelerated viral clearance and diminished pulmonary eosinophilia in infected lung tissues.

Effect of intranasal administration of Lactobacillus pentosus S-PT84 on influenza virus infection in mice

Lactobacillus pentosus strain S-PT84 isolated from Kyoto pickles enhances splenic natural killer (NK) cell activity and exhibit anti-allergic effects by modulating the Th1/Th2 (T-helper1/T-helper2) balance. In the present study, we investigated whether the immune response could be activated by intranasal administration of S-PT84 in the respiratory immune system and protected against influenza virus infection in mice. When BALB/c mice received intranasal administration of S-PT84 once daily for 3 consecutive days, S-PT84 strongly induced interleukin-12 (IL-12) and gamma interferon (IFN-γ) production in mediastinal lymph node (MLN) cells. At intranasal infection with influenza virus PR8 (a mouse-adapted H1N1 strain) after S-PT84 treatment, the survival rates of mice improved in a dose-dependent manner, and the titer of influenza virus in bronchoalveolar lavage fluids (BALF) was significantly decreased by S-PT84 administration. Production of IL-12 and alpha-interferon (IFN-α) in BALF were significantly higher in mice treated with S-PT84 compared to the control mice. Lung NK activity was also significantly augmented in S-PT84-treated mice. These results suggested that the L. pentosus strain S-PT84 showed inhibitory activity against influenza virus infection.

Identification of a novel antigen-presenting cell population modulating antiinfluenza type 2 immunity

Antiinfluenza type 2 (T2) immunity contributes to both immunopathology and immunoprotection, yet the underlying mechanisms modulating T2 immunity remain ill defined. We describe a novel mouse antigen (Ag)-presenting cell (APC), designated late-activator APC (LAPC). After pulmonary influenza A (H1N1) virus infection, LAPCs enter the lungs, capture viral Ag, and subsequently migrate to the draining lymph node (DLN) and spleen, with delayed kinetics relative to dendritic cells (DCs). In the DLN, influenza virus–activated LAPCs present Ag and selectively induce T helper type 2 (Th2) effector cell polarization by cell–cell contact–mediated modulation of GATA-3 expression. In adoptive transfer experiments, influenza virus–activated LAPCs augmented Th2 effector T cell responses in the DLN, increased production of circulating antiinfluenza immunoglobulin, and increased levels of T2 cytokines in bronchoalveolar lavage fluid in recipient influenza virus–infected mice. LAPC-recipient mice exhibited exacerbated pulmonary pathology, with delayed viral clearance and enhanced pulmonary eosinophilia. Collectively, our results identify and highlight the importance of LAPCs as immunomodulators of T2 immunity during influenza A virus infection.

Analysis of in vivo dynamics of influenza virus infection in mice using a GFP reporter virus

Influenza A virus is being extensively studied because of its major impact on human and animal health. However, the dynamics of influenza virus infection and the cell types infected in vivo are poorly understood. These characteristics are challenging to determine, partly because there is no efficient replication-competent virus expressing an easily traceable reporter gene. Here, we report the generation of a recombinant influenza virus carrying a GFP reporter gene in the NS segment (NS1-GFP virus). Although attenuated when compared with wild-type virus, the NS1-GFP virus replicates efficiently in murine lungs and shows pathogenicity in mice. Using whole-organ imaging and flow cytometry, we have tracked the dynamics of influenza virus infection progression in mice. Imaging of murine lungs shows that infection starts in the respiratory tract in areas close to large conducting airways and later spreads to deeper sections of the lungs. In addition to epithelial cells, we found GFP-positive antigen-presenting cells, such as CD11b(+)CD11c(-), CD11b(-)CD11c(+), and CD11b(+)CD11c(+), as early as 24 h after intranasal infection. In addition, a significant proportion of NK and B cells were GFP positive, suggesting active infection of these cells. We next tested the effects of the influenza virus inhibitors oseltamivir and amantadine on the kinetics of in vivo infection progression. Treatment with oseltamivir dramatically reduced influenza infection in all cell types, whereas, surprisingly, amantadine treatment more efficiently blocked infection in B and NK cells. Our results demonstrate high levels of immune cells harboring influenza virus antigen during viral infection and cell-type-specific effects upon treatment with antiviral agents, opening additional avenues of research in the influenza virus field.

Eliminating heat and wetness evil therapy for influenza virus infection

Objective To observe the role of eliminating heat and wetness evil in mice with viral pneumonia due to influenza virus infection, and to provide experimental support for clinical differentiation and treatment by exploring the immune regulating mechanism of this traditional Chinese therapy for influenza virus. Methods The antiviral effect of the therapy was observed in vitro, so was the role of this treatment in pneumonia due to influenza virus infection in mice. The rat model of viral pneumonia was established by using FM1 strains. The mice were randomly assigned to normal group, model group, Haoqinqingdan decoction group, or ribavirin group. The rates of CD3/CD4 and CD8 were detected by flow cytometry, so were serum levels of IL-4, IL-8, and IFN-γ by ELISA. Results The therapy did not have an inhibiting effect on FM1 strains, but did have on influenza virus-induced pneumonia; there was a significant difference as compared with the model group (P 0.05). Haoqinqingdan decoction had some inhibiting effect on the decreases in the rates of CD3+CD4+ and CD3+CD4+/CD3+CD8+ and reduced levels of TIL-18 and IFN-γ. Conclusions Eliminating heat and wetness evil therapy can not kill influenza virus directly. It reduces abnormal cellular immune response and strengthen humoral immune function which is beneficial of the repair of damaged tissues by adjusting the rate of CD3+CD4+/CD3+CD8+ and by reducing the expression levels of IFN-γ and IL-18. Key words: Eliminating heat and wetness evil therapy; Influenza virus; IFN- 7 ; IL-18; IL-4

Critical Role of Airway Macrophages in Modulating Disease Severity during Influenza Virus Infection of Mice

Airway macrophages provide a first line of host defense against a range of airborne pathogens, including influenza virus. In this study, we show that influenza viruses differ markedly in their abilities to infect murine macrophages in vitro and that infection of macrophages is nonproductive and no infectious virus is released. Virus strain BJx109 (H3N2) infected macrophages with high efficiency and was associated with mild disease following intranasal infection of mice. In contrast, virus strain PR8 (H1N1) was poor in its ability to infect macrophages and highly virulent for mice. Depletion of airway macrophages by clodronate-loaded liposomes led to the development of severe viral pneumonia in BJx109-infected mice but did not modulate disease severity in PR8-infected mice. The severe disease observed in macrophage-depleted mice infected with BJx109 was associated with exacerbated virus replication in the airways, leading to severe airway inflammation, pulmonary edema, and vascular leakage, indicative of lung injury. Thymic atrophy, lymphopenia, and dysregulated cytokine and chemokine production were additional systemic manifestations associated with severe disease. Thus, airway macrophages play a critical role in limiting lung injury and associated disease caused by BJx109. Furthermore, the inability of PR8 to infect airway macrophages may be a critical factor contributing to its virulence for mice.

Protection from H1N1 Influenza Virus Infections in Mice by Supplementation with Selenium: A Comparison with Selenium-Deficient Mice

The present paper describes protective effects of supplemental selenium in mice infected with influenza virus. The effects of supplemental selenium on serum selenium levels, mortality, lung virus titers, and cytokine titers were investigated in mice inoculated intranasally with suspensions of influenza virus. Whereas the mortality of the virus-infected Se-deficient mice was 75%, along with a marked reduction in body weight, lower levels of TNF-α and IFN-γ and lower serum selenium concentrations, the mortality of mice maintained on feed containing 0.5mg Se/kg in the form of sodium selenite was 25%.There were no significantly differences, however, in viral titer between the Se-adequate and the selenium-supplemented groups. The data indicate that selenium supplementation may provide a feasible approach to improving the immune response to viral infections, such as lethal influenza infection.

Supplementation with bovine colostrum enhances natural killer cell activity in influenza‐infected mice

Bovine colostrum (BC), from the first milking following partuition, is available as a human nutraceutical for immune support, although data are limited. Oral administration of BC in mice has been demonstrated to affect local intestinal immunity, including an increase in the percentage of NK cells; however, resistance to infection has not been studied. Therefore, we proposed to investigate the effects of BC (W150, La Belle, Inc.) on the innate immune response to influenza infection in 4 month‐old female C57BL/6 mice supplemented with 1g of BC/kg of body weight by pipette for 7 days prior to and following a non‐lethal infection with mouse‐adapted influenza A virus (H1N1, PR8). Animals were observed through 3 days of infection and assessed for weight loss and recovery, lung virus titers, splenic NK cell activity and serum IgA. BC‐supplemented mice demonstrated less reduction in body weight and decreased lung virus burden following infection compared to controls, indicating a less severe infection. BC‐supplemented mice also demonstrated a significant increase in influenza‐enhanced NK cell cytotoxicity compared to controls at 3 days post‐infection (P<0.05). There were no differences in IgA levels between groups. BC supplementation enhanced NK cell cytotoxicity and improved the immune response to influenza virus infection in mice, with no effect on serum IgA. (Sponsored by La Belle, Inc., Bellingham, WA)

The Effector phase of the CD8+ T cell response is not programmed during initiation (50.25)

Abstract It is believed that CD8+ T cell responses are programmed at initiation in the lymph nodes by activated antigen presenting cells to undergo further proliferation in the absence of antigen and costimulation signals. We examined the effector CD8+ T cell response in the lungs of influenza virus infected mice during the late phase of infection, in the absence of costimulation, antigen and dendritic cells (DC). Blocking CD28-CD80/CD86 signaling with antibodies or depleting DCs after day six of the infection results in a 6-fold reduction in the absolute number of lung NP366-374- specific CD8+ T cells at the peak of the infection on day 10. Adoptive transfer of effector OVA257-264- specific CD8+ T cells into WSN-OVA infected wild type mice, CD80/CD86 knockout mice and DC depleted CD11c-DTR mice showed a 7-fold reduction in the number of effector CD8+ T cells in the lungs. Importantly effector CD8+ T cells need antigen to expand. Transferred effector OVA257-264 specific CD8+ T cells from lungs of WSN-OVA infected mice fail to expand in mice infected with influenza virus that does not carry cognate antigen. Moreover the absence of costimulation and dendritic cells leads to increased apoptosis of effector CD8+ T cells. In conclusion our results show that antigen-specific CD8+ T cells at the effector site need the continuous presence of dendritic cells, antigen and costimulation for expansion and survival during the late effector phase of the immune response

Insight into AhR-mediated increases in neutrophilia during infection: iNOS as a potentially new AhR target gene (37.26)

Abstract There are many known factors that can affect immune responses to respiratory viral infections such as influenza A virus. Indeed, recent epidemiological studies indicate that in addition to host genetics, age and pathogen sub-types, a variety of environmental factors also impact the immune response to infections. Many of these environmental factors, including diesel exhaust and cigarette smoke, contain ligands for the aryl hydrocarbon receptor (AhR), an environment-sensing transcription factor shown to affect multiple facets of the immune system. Our laboratory has shown that activation of the AhR by the persistent environmental contaminant dioxin exacerbates neutrophil recruitment and increases the expression of inducible nitric oxide synthase (iNOS) in the lungs of influenza virus-infected mice. We show that depleting neutrophils during viral infection does not abrogate AhR-mediated increases in iNOS expression, demonstrating that neutrophil recruitment is downstream of elevated iNOS. We also show that AhR activation in iNOS-deficient mice infected with influenza virus does not affect neutrophil recruitment to the lung. Thus, these findings suggest that these AhR-mediated events are linked, and that increased iNOS expression could be a novel mechanism regulating neutrophil migration the infected lung. Additionally these studies implicate iNOS as a novel AhR target gene and provide new insights into the mechanisms underlying leukocyte recruitment during viral infections.

A DNA Vaccine-Encoded Nucleoprotein of Influenza Virus Fails To Induce Cellular Immune Responses in a Diabetic Mouse Model

Influenza virus infections cause yearly epidemics and are a major cause of lower respiratory tract illnesses in humans worldwide. Influenza virus has long been recognized to be associated with higher morbidity and mortality in diabetic patients. Vaccination is an effective tool to prevent influenza virus infection in this group of patients. Vaccines employing recombinant-DNA technologies are an alternative to inactivated virus and live attenuated virus vaccines. Internal highly conserved viral nucleoprotein (NP) can be delivered as a DNA vaccine to provide heterosubtypic immunity, offering resistance against various influenza virus strains. In this study, we investigated the efficacy of an NP DNA vaccine for induction of cell-mediated immune responses and protection against influenza virus infection in a mouse model of diabetes. Healthy and diabetic BALB/c mice were immunized on days 0, 14, and 28 by injection of NP DNA vaccine. Two weeks after the last immunization, the cellular immune response was evaluated by gamma interferon (IFN-gamma), lymphocyte proliferation, and cytotoxicity assays. The mice were challenged with influenza virus, and the viral titers in the lungs were measured on day 4. Diabetic mice showed significantly smaller amounts of IFN-gamma production, lymphocyte proliferation, and cytotoxicity responses than nondiabetic mice. Furthermore, higher titers of the influenza virus were detected after challenge in the lungs of the diabetic mice. The present data suggest that the NP DNA vaccine with the protocol of immunization described here is not able to induce efficient cellular immune responses against influenza virus infection in diabetic mice.

Efficacy of inactivated vaccine against H5N1 influenza virus infection in mice with type 1 diabetes

We sought to determine susceptibility to highly pathogenic avian influenza (HPAI) H5N1 virus and to explore immune protection of inactivated H5N1 vaccine in streptozotocin-induced type 1 diabetic mice. Susceptibility of diabetic mice to an H5N1 virus was evaluated by comparing the median lethal dose (LD 50) and the lung virus titers with those of the healthy after the viral infection. To evaluate the influence of diabetes on vaccination, diabetic and healthy mice were immunized once with an inactivated H5N1 vaccine and then challenged with a lethal dose of H5N1 virus. The antibody responses, survival rates, lung virus titers and body weight changes were tested. Mice with type 1 diabetes had higher lung virus titers and lower survival rates than healthy mice after H5N1 virus infection. Inactivated H5N1 vaccine induced protective antibody in diabetic mice, but the antibody responses were postponed and weakened. In spite of this, diabetic mice could be protected against the lethal virus challenge by a single dose of immunization when the amount of the antigen increased. These results indicated that type 1 diabetic mice were more susceptible to H5N1 influenza virus infection than healthy mice, and can be effectively protected by inactivated H5N1 vaccine with increased antigen.

MicroRNA Expression and Virulence in Pandemic Influenza Virus-Infected Mice

The worst known H1N1 influenza pandemic in history resulted in more than 20 million deaths in 1918 and 1919. Although the underlying mechanism causing the extreme virulence of the 1918 influenza virus is still obscure, our previous functional genomics analyses revealed a correlation between the lethality of the reconstructed 1918 influenza virus (r1918) in mice and a unique gene expression pattern associated with severe immune responses in the lungs. Lately, microRNAs have emerged as a class of crucial regulators for gene expression. To determine whether differential expression of cellular microRNAs plays a role in the host response to r1918 infection, we compared the lung cellular "microRNAome" of mice infected by r1918 virus with that of mice infected by a nonlethal seasonal influenza virus, A/Texas/36/91. We found that a group of microRNAs, including miR-200a and miR-223, were differentially expressed in response to influenza virus infection and that r1918 and A/Texas/36/91 infection induced distinct microRNA expression profiles. Moreover, we observed significant enrichment in the number of predicted cellular target mRNAs whose expression was inversely correlated with the expression of these microRNAs. Intriguingly, gene ontology analysis revealed that many of these mRNAs play roles in immune response and cell death pathways, which are known to be associated with the extreme virulence of r1918. This is the first demonstration that cellular gene expression patterns in influenza virus-infected mice may be attributed in part to microRNA regulation and that such regulation may be a contributing factor to the extreme virulence of the r1918.

Pulmonary protection of a plant polyphenol extract in influenza virus-infected mice

Influenza remains one of the serious problems of public health. The plant extracts provide an alternative source for substances with antiviral properties. The current study investigated the protective effect of a polyphenol-rich extract from the medicinal plant Geranium sanguineum L. (PC) in mice, nasally (i.n.) challenged with influenza A/Aichi/2/68 (H3N2) virus (IV) and its effects on mice lungs.

Modulation of cytokine production by 7-hydroxycoumarin in vitro and its efficacy against influenza infection in mice

We previously demonstrated that 7-hydroxycoumarin (7HC) was effective in reducing proinflammatory cytokine production in lipopolysaccharide-exposed macrophage-like P388D1 cells and fever production by suppressing the increase in interleukin (IL)-1α production in an influenza virus-intranasal infection model in mice. In this study, we assessed the effects of modulation of cytokine production by 7HC on influenza virus infection in relation to its efficacy in influenza virus-infected mice. 7HC was confirmed to suppress proinflammatory cytokine levels in P388D1 cells due to influenza virus infection. In the murine infection model, oral administration of 7HC (30 mg/kg) was significantly effective in reducing the weight loss of infected mice and virus titers in the bronchoalveolar lavage fluid (BALF) of lungs and in prolonging survival times without toxicity. The rise of proinflammatory and Th1 cytokine (IL-12 and interferon-γ) production in the BALF from infected mice was significantly suppressed by 7HC at two and four days post-infection, respectively. This suppression correlated with the reduction of virus titers and diminution of lung consolidation. Because 7HC did not exhibit direct anti-influenza virus activity in vitro, 7HC was suggested to suppress pneumonia in influenza virus-infected mice through suppression of the cytokine production induced by infection.