Effect of Wen-Pi-Tang extract on lung damage by influenza virus infection

The effect of Wen-Pi-Tang extract on influenza virus infection in mice was investigated. The administration of Wen-Pi-Tang extract at a dose of 100 mg/kg body wt. for 8 consecutive days to influenza virus-infected mice reversed the lack of body wt. gain and prevented the increase in lung weight caused by the infection in comparison with uninfected mice, while allopurinol, a xanthine oxidase (XOD) inhibitor, did not show these effects. The serum levels of uric acid and allantoin in influenza virus-infected mice were reduced by Wen-Pi-Tang extract administration. Moreover, Wen-Pi-Tang extract reduced the uric acid level more as the dose increased, although it exerted lower activity than allopurinol. The XOD activity of the lungs was elevated by influenza virus infection, but Wen-Pi-Tang extract administration inhibited this activity, indicating prevention of lung damage by oxygen free radicals generated by XOD. After the administration of Wen-Pi-Tang extract to influenza virus-infected mice, the lung superoxide dismutase activity was not significantly different from that of uninfected mice, whereas lung catalase activity was lower in the former than the latter, but slightly higher than that of influenza virus-infected mice, suggesting that Wen-Pi-Tang extract may prevent the generation of highly toxic hydroxyl radicals in the lung. In addition, the administration of both Wen-Pi-Tang extract and allopurinol reduced the degree of lung consolidation caused by influenza virus infection. In particular, Wen-Pi-Tang extract reduced the consolidation score in a dose-dependent manner and more markedly than allopurinol did. This study suggests that Wen-Pi-Tang extract could improve pathological conditions of the lungs induced by influenza virus infection.     

Antiviral Activity of Chlorite-Oxidized Oxyamylose, a Polyacetal Carboxylic Acid

Intraperitoneal injection of chlorite-oxidized oxyamylose (COAM) protected mice against mengo, vaccinia, Semliki Forest, and influenza APR8 viruses. Topical administration in the eye of rabbits partially inhibited the development of experimental herpetic keratoconjunctivitis. COAM resembled polyacrylic acid in many aspects, but it was markedly less toxic. For systemic administration, the therapeutic index was on the order of magnitude of 1:300 to 1:500. Although the in vivo antiviral effect of COAM wore off faster than that of polyacrylic acid, protection lasted for several weeks. Against mengovirus, such prolonged protection was achieved only when polymer and virus were injected intraperitoneally. Protection against intravenous vaccinia virus was not dependent on the injection route of COAM. Experiments on the mode of action of COAM pointed to macrophages as possible mediators of the antiviral effect. The fact that small amounts of interferon appeared in the serum after administration of high doses of COAM suggests that interferon may play a role in the induction of antiviral resistance by COAM.     

The role of neutrophils in the upper and lower respiratory tract during influenza virus infection of mice

Background

Neutrophils have been shown to play a role in host defence against highly virulent and mouse-adapted strains of influenza virus, however it is not clear if an effective neutrophil response is an important factor moderating disease severity during infection with other virus strains. In this study, we have examined the role of neutrophils during infection of mice with influenza virus strain HKx31, a virus strain of the H3N2 subtype and of moderate virulence for mice, to determine the role of neutrophils in the early phase of infection and in clearance of influenza virus from the respiratory tract during the later phase of infection.

Methods

The anti-Gr-1 monoclonal antibody (mAb) RB6-8C5 was used to (i) identify neutrophils in the upper (nasal tissues) and lower (lung) respiratory tract of uninfected and influenza virus-infected mice, and (ii) deplete neutrophils prior to and during influenza virus infection of mice.

Results

Neutrophils were rapidly recruited to the upper and lower airways following influenza virus infection. We demonstrated that use of mAb RB6-8C5 to deplete C57BL/6 (B6) mice of neutrophils is complicated by the ability of this mAb to bind directly to virus-specific CD8⁺ T cells. Thus, we investigated the role of neutrophils in both the early and later phases of infection using CD8⁺ T cell-deficient B6.TAP^-/- mice. Infection of B6.TAP^-/- mice with a low dose of influenza virus did not induce clinical disease in control animals, however RB6-8C5 treatment led to profound weight loss, severe clinical disease and enhanced virus replication throughout the respiratory tract.

Conclusion

Neutrophils play a critical role in limiting influenza virus replication during the early and later phases of infection. Furthermore, a virus strain of moderate virulence can induce severe clinical disease in the absence of an effective neutrophil response.     

Vaccination against Human Influenza A/H3N2 Virus Prevents the Induction of Heterosubtypic Immunity against Lethal Infection with Avian Influenza A/H5N1 Virus

Annual vaccination against seasonal influenza viruses is recommended for certain individuals that have a high risk for complications resulting from infection with these viruses. Recently it was recommended in a number of countries including the USA to vaccinate all healthy children between 6 and 59 months of age as well. However, vaccination of immunologically naïve subjects against seasonal influenza may prevent the induction of heterosubtypic immunity against potentially pandemic strains of an alternative subtype, otherwise induced by infection with the seasonal strains.Here we show in a mouse model that the induction of protective heterosubtypic immunity by infection with a human A/H3N2 influenza virus is prevented by effective vaccination against the A/H3N2 strain. Consequently, vaccinated mice were no longer protected against a lethal infection with an avian A/H5N1 influenza virus. As a result H3N2-vaccinated mice continued to loose body weight after A/H5N1 infection, had 100-fold higher lung virus titers on day 7 post infection and more severe histopathological changes than mice that were not protected by vaccination against A/H3N2 influenza.The lack of protection correlated with reduced virus-specific CD8+ T cell responses after A/H5N1 virus challenge infection. These findings may have implications for the general recommendation to vaccinate all healthy children against seasonal influenza in the light of the current pandemic threat caused by highly pathogenic avian A/H5N1 influenza viruses.     

Identification of novel avian influenza virus derived CD8+ T-cell epitopes

Avian influenza virus (AIV) infection is a continuing threat to both humans and poultry. Influenza virus specific CD8+ T cells are associated with protection against homologous and heterologous influenza strains. In contrast to what has been described for humans and mice, knowledge on epitope-specific CD8+ T cells in chickens is limited. Therefore, we set out to identify AIV-specific CD8+ T-cell epitopes. Epitope predictions based on anchor residues resulted in 33 candidate epitopes. MHC I inbred chickens were infected with a low pathogenic AIV strain and sacrificed at 5, 7, 10 and 14 days post infection (dpi). Lymphocytes isolated from lung, spleen and blood were stimulated ex vivo with AIV-specific pooled or individual peptides and the production of IFNγ was determined by ELIspot. This resulted in the identification of 12 MHC B12-restricted, 3 B4-restricted and 1 B19-restricted AIV- specific CD8+ T-cell epitopes. In conclusion, we have identified novel AIV-derived CD8+ T-cell epitopes for several inbred chicken strains. This knowledge can be used to study the role of CD8+ T cells against AIV infection in a natural host for influenza, and may be important for vaccine development.     

Inhibitory role of neutrophils on influenza virus multiplication in the lungs of mice.

The protective role of neutrophils on intranasal infection of influenza virus was investigated in 3 strains of tumor-bearing mice with neutrophilic leukocytosis. In vitro multiplication of influenza virus was inhibited by neutrophils from both normal and tumor-bearing mice, and the inhibitory effect of neutrophils was augmented by an addition of fMLP to the culture. Pulmonary virus infectivities in the early phase after infection decreased in such ICR and BALB/c mice, and virus elimination in the late phase was accelerated in the ICR mice. However, no decrease in pulmonary virus infectivity was observed in tumor-bearing C57BL/6 mice. Intranasal administration of fMLP into normal and tumor-bearing C57BL/6 mice after infection significantly inhibited the virus propagation in the lungs. The decrease in neutrophil infiltration into the lung in tumor-bearing C57BL/6 mice was confirmed from histological observations of the lung and lung lavage after infection and from analysis of the neutrophil chemotactic activity induced by fMLP. This might be responsible for the high level of pulmonary virus titer in tumor-bearing C57BL/6 mice. Phagocytic activities of alveolar macrophages and productions of neutralizing antibody were suppressed in the 3 strains of tumor-bearing mice. These observations indicated that neutrophils could be significant effector cells as a host defense mechanism against influenza virus infection in vivo, and infiltration and functional activation of neutrophils could play a significant role in virus elimination from the infected site. Furthermore, the inhibition of virus propagation by neutrophils in vitro was almost completely abrogated by an addition of ZnSO4, suggesting that calprotectin could inhibit influenza virus multiplication.     

Host genetic background and the innate inflammatory response of lung to influenza virus

Many studies of influenza severity have focused on viral properties that confer virulence, whereas the contributory role of the host genetic background on infection severity remains largely unexplored. In this study, we measure the impact of inoculation with influenza virus in four strains of inbred mice - BALB/cByJ, C57BL/6 J, A/J, and DBA/2 J. To evaluate the extent to which responses are inherent to lung per se, as opposed to effects of the systemic response to lung infection, we also measured cytokines and chemokines in lung slices exposed to the virus in vitro. Finally, we evaluate the in vivo responses of recombinant inbred (RI) and select consomic strains of mice to search for genomic loci that contribute to phenotypic variance in response to influenza infection. We found marked variation among mouse strains after challenge with virus strain A/HKX31(H3N2), consistent with previous reports using more virulent strains. Furthermore, response patterns differ after in vivo versus in vitro exposure of lung to virus, supporting a predominant role of the systemic host inflammatory response in generating the strain differences. These results add to the body of information pointing to host genotype as a crucial factor in mediating the severity of influenza infections.     

Andrographolide inhibits influenza A virus-induced inflammation in a murine model through NF-κB and JAK-STAT signaling pathway

Influenza viruses, the main cause of respiratory tract diseases, cause high morbidity and mortality in humans. Excessive inflammation in the lungs is proposed to be a hallmark for the severe influenza virus infection, especially influenza A virus infection. Strategies against inflammation induced by influenza A virus infection could be a potential anti-influenza therapy. Here, lethal dose of mouse-adapted H1N1 strain PR8A/PR/8/34 was inoculated C57BL/6 mice to detect the anti-influenza activity of andrographolide, the active component of traditional Chinese medicinal herb Andrographis paniculata, with or without influenza virus entry inhibitor CL-385319. Treatment was initiated on 4 days after infection. The survival rate, body weight, lung pathology, viral loads, cytokine expression were monitored in 14 days post inoculation. The combination group had the highest survival rate. Andrographolide treatment could increase the survival rate, diminish lung pathology, decrease the virus loads and the inflammatory cytokines expression induced by infection. Mechanism studies showed the NF-κB and JAK-STAT signaling pathway were involved in the activity of andrographolide. In conclusion, combination of virus entry inhibitor with immunomodulator might be a promising therapeutic approach for influenza.     

Dependence of the cocarcinogenic action of the influenza virus on the nature of the influenza infection

It was shown in experiments of CC57W mice that cocarcinogenic activity of influenza A/PR8/34 virus correlates with acute or chronic pattern of infection. Prolonged persistence of the virus resulted in significant stimulation of the lung tumor incidence in infected mice. The prevention with thymosin of chronic influenza infection development in CC57W mice lead to a decrease in the incidence of lung tumors to the control level.     

Development of lung tumors in Syrian hamsters with a mixed Mycoplasma pneumoniae and influenza virus infection

The authors studied morphological alterations in the lungs of Syrian hamsters infected intranasally with Mycoplasma pneumoniae and influenza virus. The animals were first infected with M. pneumoniae and after 7 days with influenza A/PR8 virus. On days 1-3 after infection with influenza virus (days 8-11 following infection with M. pneumoniae) the animals showed the appearance of multiple foci of bronchiolar epithelium proliferation. At the later stages of experiment the size of the foci of proliferation increased. On days 14-21 after infection with influenza virus (days 21-28 of experiment) the animals developed lung tumors.     

Effects of Oxyamylose and Polyacrylic Acid on Foot-and-Mouth Disease and Hog Cholera Virus Infections

Two interferon-inducing polycarboxylates were tested for antiviral activity on foot-and-mouth disease (FMD) virus infections in mice, guinea pigs, and swine. Polyacrylic acid, given intraperitoneally, had a protective effect on infection by FMD virus administered in the peritoneal cavity of mice and in the foot pad of guinea pigs. Chlorite-oxidized oxyamylose (COAM) was effective in mice at a dosage of 2 mg/kg. Swine were not protected against naturally transmitted FMD by 120 mg/kg of COAM nor by polyacrylic acid. Swine were not totally unresponsive to COAM since it delayed symptoms of hog cholera. Interferon was not detected in the serum of COAM-treated swine. With FMD virus, an example was found of activity of interferon inducers in experimental hosts and lack of activity in a natural host.     

Characterization of Cells Infiltrating the Lungs of X-Irradiated and Nude Mice after Influenza Virus Infection

After X-irradiated and nonirradiated mice (C3H/He) as well as athymic nude mice and haired littermates (BALB/c) were infected with influenza A virus (Kumamoto strain, H2N2), they were examined for survival period, the development of consolidation in the lungs and the characteristics of the cells infiltrating the lung tissues. In two different T-cell deficient groups, there was a definite delay in the development of consolidation compared with their respective controls and this was reflected in prolonged survival periods: 5 days longer for irradiated mice and 6 days longer for nude mice. In both T-cell deficient and normal groups, about 70% of the cells obtained from consolidated lung tissues after virus infection were found to be small lymphoid cells and there were no morphological differences between the T-cell deficient and normal groups. None of these small lymphoid cells from the peripheral blood or the spleens of T-cell deficient mice responded to concanavalin A. In the lungs of both X-irradiated mice and nude mice, however, a definite increase in cells having natural killer activity was found at the late stages of the influenza infection, suggesting their participation in the development of consolidation.     

Influenza A virus-infected hosts boost an invasive type of Streptococcus pyogenes infection in mice

The apparent worldwide resurgence of invasive Streptococcus pyogenes infection in the last two decades remains unexplained. At present, animal models in which toxic shock-like syndrome or necrotizing fasciitis is induced after S. pyogenes infection are not well developed. We demonstrate here that infection with a nonlethal dose of influenza A virus 2 days before intranasal infection with a nonlethal dose of S. pyogenes strains led to a death rate of more than 90% in mice, 10% of which showed necrotizing fasciitis. Infection of lung alveolar epithelial cells by the influenza A virus resulted in viral hemagglutinin expression on the cell surface and promoted internalization of S. pyogenes. However, treatment with monoclonal antibodies to hemagglutinin markedly decreased this internalization. Our results indicate that prior infection with influenza A virus induces a lethal synergism, resulting in the induction of invasive S. pyogenes infection in mice.     

Collectin-mediated antiviral host defense of the lung: evidence from influenza virus infection of mice.

Collagenous lectins (collectins) present in mammalian serum and pulmonary fluids bind to influenza virus and display antiviral activity in vitro, but their role in vivo has yet to be determined. We have used early and late isolates of H3N2 subtype influenza viruses that differ in their degree of glycosylation to examine the relationship between sensitivity to murine serum and pulmonary lectins in vitro and the ability of a virus to replicate in the respiratory tract of mice. A marked inverse correlation was found between these two parameters. Early H3 isolates (1968 to 1972) bear 7 potential glycosylation sites on hemagglutinin (HA), whereas later strains carry 9 or 10. Late isolates were shown to be much more sensitive than early strains to neutralization by the mouse serum mannose-binding lectin (MBL) and rat lung surfactant protein D (SP-D) and bound greater levels of these lectins in enzyme-linked immunosorbent assays and Western blot analyses. They also replicated very poorly in mouse lungs compared to the earlier strains. Growth in the lungs was greatly enhanced, however, if saccharide inhibitors of the collectins were included in the virus inoculum. The level of SP-D in bronchoalveolar lavage fluids increased on influenza virus infection. MBL was absent from lavage fluids of normal mice but could be detected in fluids from mice 3 days after infection with the virulent strain A/PR/8/34 (H1N1). The results implicate SP-D and possibly MBL as important components of the innate defense of the respiratory tract against influenza virus and indicate that the degree or pattern of glycosylation of a virus can be an important factor in its virulence.     

Thoracic radiography as a refinement methodology for the study of H1N1 influenza in cynomologus macaques (Macaca fascicularis)

Recent advances in the technology associated with digital radiography have created new opportunities for biomedical research applications. Here we evaluated the use of thoracic radiography as a noninvasive refinement methodology for the cynomologus macaque (Macaca fascicularis) model of H1N1 infection. Thoracic radiographic evaluations of macaques infected with any of 3 strains of emerging H1N1 swine-associated influenza virus isolated during the recent pandemic were compared with those of macaques infected with the currently circulating Kawasaki strain of H1N1 influenza. Ventrodorsal, right, and left lateral thoracic radiographs were obtained at days 0, 1, 6, 8, 11, and 14 after infection. A board-certified veterinary radiologist who was blinded to the study design evaluated the images. Numeric scores of extent and severity of lung involvement assigned to each radiograph were compared and demonstrated a significant and substantial difference among groups. The radiographic evaluation allowed for noninvasive assessment of lung involvement, disease onset, progression, and resolution of radiographic changes associated with H1N1 influenza infection.     

甲型H1N1流感病毒感染不同免疫缺陷小鼠的比较

目的宿主免疫系统的功能状态在病毒的感染中起着至关重要的作用,本实验观察了不同免疫缺陷小鼠感染甲型H1N1流感病毒的差异。方法使用六个品系的近交系小鼠,经乙醚麻醉后进行滴鼻攻毒,分析其在病毒感染后存活率、体重变化和肺组织病理改变的异同。结果感染H1N1病毒的6种小鼠在观察的14d内,野生型的C57BL／6小鼠感染开始体重缓慢下降,感染后期有所回升,有半数存活;BALB／c小鼠和四种免疫缺陷品系小鼠感染病毒后体重随病情发展快速下降,死亡率均为100％。野生型C57BL／6小鼠感染初期为较弥漫的间质性肺炎,后期病变逐渐局限;BALB／c小鼠和四种免疫缺陷品系小鼠感染病毒后出现弥漫的中重度间质性肺炎,细支气管上皮有变性坏死,但炎症细胞明显少于C57BL／6小鼠。结论在甲型H1N1流感病毒的初次感染中固有免疫和特异性免疫分别在感染的初期和后期起主要作用,宿主免疫系统的功能状态影响着甲型H1N1病毒感染和预后。     

Preexisting influenza-specific CD4+ T cells correlate with disease protection against influenza challenge in humans

Protective immunity against influenza virus infection is mediated by neutralizing antibodies, but the precise role of T cells in human influenza immunity is uncertain. We conducted influenza infection studies in healthy volunteers with no detectable antibodies to the challenge viruses H3N2 or H1N1. We mapped T cell responses to influenza before and during infection. We found a large increase in influenza-specific T cell responses by day 7, when virus was completely cleared from nasal samples and serum antibodies were still undetectable. Preexisting CD4+, but not CD8+, T cells responding to influenza internal proteins were associated with lower virus shedding and less severe illness. These CD4+ cells also responded to pandemic H1N1 (A/CA/07/2009) peptides and showed evidence of cytotoxic activity. These cells are an important statistical correlate of homotypic and heterotypic response and may limit severity of influenza infection by new strains in the absence of specific antibody responses. Our results provide information that may aid the design of future vaccines against emerging influenza strains.