汉黄芩素对流感病毒感染肺泡巨噬细胞炎症相关因子的影响

目的: 研究汉黄芩素对甲型流感病毒鼠肺适应株A/FM/1/47(H1N1)感染的大鼠肺泡巨噬细胞(NR8383)产生促炎症细胞因子、炎症介质及氧自由基的影响。 方法: 流感病毒感染 NR8383细胞1 h后,加入含汉黄芩素的培养基(终浓度16 mg/L),药物作用后6 h、12 h和24 h,ELISA法检测细胞上清中肿瘤坏死因子α(TNF-α)和单核细胞趋化蛋白 1(MCP-1)的含量,放射免疫测定法检测细胞上清中前列腺素E₂(PGE₂)、磷脂酸A₂(PLA₂)和白三烯B₄(LTB₄)的含量;药物作用后8 h、24 h、36 h和48 h,生化法检测细胞内一氧化氮(NO)含量和诱导型一氧化氮合酶(iNOS)活性,4 h、8 h、18 h和24 h,生化法检测超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量;药物作用后24 h,real-time PCR检测细胞内TNF-α和MCP-1的mRNA水平。 结果: 汉黄芩素抑制了流感病毒感染NR8383细胞后TNF-α、MCP-1的转录和表达(P<0.01),降低了PGE₂、PLA₂、LTB₄和MDA的含量(P<0.05);减少了NO和iNOS的产生(P<0.05),增强了SOD的活性(P<0.05)。 结论: 汉黄芩素明显抑制了流感病毒感染后肺泡巨噬细胞内各种炎症相关因子的产生,具有抗炎作用。     

Interaction of influenza virus with mouse macrophages.

Mouse peritoneal and alveolar macrophages differed substantially in their response to influenza in vitro. Immunofluorescent and infectious-center techniques showed that viral proteins were produced in only a small subpopulation (17%) of peritoneal macrophages and that these infected cells were removed from culture by 3 days postinfection. In contrast, alveolar macrophages were highly susceptible to influenza, and viral antigens were produced in all cells. This was accompanied by a cytopathic effect and cell death. However, no infectious virus was released and the infection was considered abortive. With mouse cytomegalovirus, however, both alveolar and peritoneal macrophages were equally restrictive, and viral antigens were produced in only 1 to 5% of either cell population. No significant differences were observed between mouse-virulent and -avirulent strains of influenza in their interaction with macrophages either in vitro or in vivo. In vivo, both strains induced an influx of cells to the alveolar spaces by 3 to 4 days postinfection, and this was reflected by a 5- to 10-fold increase in the number of "macrophages" in harvest fluids at this time. Many of these cells had an altered morphology compared with alveolar macrophages from uninfected mice, and the cell population as a whole was not susceptible to influenza. However, this resistance was lost by 7 days of in vitro culture.     

Histopathological Evaluation of the Diversity of Cells Susceptible to H5N1 Virulent Avian Influenza Virus

Patients infected with highly pathogenic avian influenza A H5N1 viruses (H5N1 HPAIV) show diffuse alveolar damage. However, the temporal progression of tissue damage and repair after viral infection remains poorly defined. Therefore, we assessed the sequential histopathological characteristics of mouse lung after intranasal infection with H5N1 HPAIV or H1N1 2009 pandemic influenza virus (H1N1 pdm). We determined the amount and localization of virus in the lung through IHC staining and in situ hybridization. IHC used antibodies raised against the virus protein and antibodies specific for macrophages, type II pneumocytes, or proliferating cell nuclear antigen. In situ hybridization used RNA probes against both viral RNA and mRNA encoding the nucleoprotein and the hemagglutinin protein. H5N1 HPAIV infection and replication were observed in multiple lung cell types and might result in rapid progression of lung injury. Both type II pneumocytes and macrophages proliferated after H5N1 HPAIV infection. However, the abundant macrophages failed to block the viral attack, and proliferation of type II pneumocytes failed to restore the damaged alveoli. In contrast, mice infected with H1N1 pdm exhibited modest proliferation of type II pneumocytes and macrophages and slight alveolar damage. These results suggest that the virulence of H5N1 HPAIV results from the wide range of cell tropism of the virus, excessive virus replication, and rapid development of diffuse alveolar damage.Seasonal, pandemic, and zoonotic influenza A virus infections show substantial morbidity and mortality in humans. Seasonal influenza A virus infections in humans are usually mild and cause pneumonia only in a few infected individuals. Pandemic influenza virus infections vary in their disease outcome. Zoonotic influenza virus infections in humans vary from self-limiting conjunctivitis to severe, often fatal, pneumonia. Highly pathogenic avian influenza H5N1 virus (H5N1 HPAIV), implicated in poultry outbreaks,^1,2 can be transmitted zoonotically to humans, as has been observed in areas of Asia and Africa.^3–5 Fatal outcomes have been reported at approximately 60% in the sporadic transmission of this avian influenza H5N1 virus to humans.^5–7 There is no evidence that the avian influenza virus has become efficiently transmissible among humans, a change that could result in a new pandemic.⁸The outcome after infection with influenza virus can range from slight to severe illness, depending on the kinds of cells that are affected during lung tissue infection.^9–11 Events occurring early in infection determine the extent of damage, which can range from bronchitis to pneumonia. In the most severe cases, diffuse alveolar damage (DAD) may be induced during the early stages, and healing and/or scarring may ensue, depending on the persistence of disease. Occasionally, bacterial infection also may occur, with associated effects expressed mainly in the later stages of the disease. Pathological damage caused by influenza viruses in humans and in animal models depends on the virulence of the infective agent and on the host response. All influenza viruses infect the respiratory tract epithelium from the nasal passages to the bronchioles; however, highly virulent viruses (eg, H1N1 1918 and H5N1 HPAIV) tend to infect pneumocytes and resident macrophages in the alveoli. In susceptible individuals, inflammation of the alveolar walls results in DAD. In contrast, low-virulence viruses (seasonal H1N1) primarily cause inflammation, congestion, and epithelial necrosis of the trachea, bronchi, and bronchioles. Tissue tropism is an important factor, and depends largely on the ability of the virus to attach to the host cell.^12–14 We investigated virus replication and histopathological progression of lung tissue in mice infected with H5N1 HPAIV, particularly focusing on the lower respiratory tract and alveoli, with direct comparison to the histopathological characteristics of mice infected with H1N1 pandemic (pdm) influenza virus 2009 virus.     

In vitro interaction of alveolar macrophages and pneumocytes with feline respiratory viruses.

Feline alveolar macrophages and feline pneumocytes were inoculated in vitro with low multiplicities of either feline calicivirus or feline viral rhinotracheitis virus. Pneumocytes were permissive for both viruses. High titers were attained, and characteristic cytopathic effects developed. Alveolar macrophages were permissive for feline viral rhinotracheitis virus, although the cycle of replication was delayed. Infection of macrophages with feline calicivirus resulted in the production of viral antigens and cytopathic effects; however, viral particles were not detected by electron microscopy, and viral infectivity titers rose only slightly and then fell to undetectable levels by 96 h. The differences in viral susceptibility between these two peripheral pulmonary cell populations that were demonstrated in vitro probably contribute to the differences in pathogenesis of viral rhinotracheitis and calicivirus infections in cats.     

Functional expression of influenza A viral nucleoprotein in cells transformed with cloned DNA

Simian cells permissive for influenza A virus infection were stably transformed with a full-length cloned influenza A nucleoprotein gene under the control of an inducible metallothionein promoter and linked to a dihydrofolate reductase gene to facilitate cell selection. Transformed cells synthesized a virus-specific nucleoprotein which was indistinguishable from the nucleoprotein synthesized in virus-infected cells with respect to molecular weight and intracellular localization. It was estimated that transformed cells produced only 1% of the amount of nucleoprotein synthesized in simian cells infected with influenza A virus. Nonetheless, when transformed cells were infected with influenza virus mutants which synthesized temperature-sensitive nucleoprotein, protein expressed by the cloned gene was able to complement the synthesis of plus-strand and minus-strand viral RNA for one mutant and only plus-strand synthesis for another mutant. This indicated that the influenza A nucleoprotein expressed in the transformed cells exhibited functional activity.     

A novel synthetic reversible inhibitor of sialidase efficiently blocks secondary but not primary influenza virus infection of MDCK cells in culture

Summary.  The sodium salts of 2-difluoromethyl-phenyl-α-ketoside of N-acetyl-neuraminic acid (compound 1) and of 4-difluoromethyl-2-methoxy-phenyl-α-ketoside of N-acetylneuraminic acid (compound 2) were designed as potential mechanism-based inhibitors of sialidase. In vitro both of these compounds competitively inhibited the sialidases of Clostridium perfringens and of influenza virus A/HK/1/68. Inhibition was irreversible with the sialidase of Clostridium perfringens whereas it was reversible with that of A/HK/1/68. Compound 2 did not inhibit the hemagglutinin of the virus but exhibited significant anti-influenza activity when added to the medium of Madin-Darby canine kidney (MDCK) cells infected by influenza virus. In non-infected MDCK cells no inhibition of cellular sialidase was observed. Compound 2 did not block primary infection, but inhibited the release of progeny virus from infected cells. Even after 8 passages in its presence, no resistant strains were detected. Because of its high Ki (M) compared to the low Ki (M) of 4 guanidino-Neu 5 Ac 2en and its reversible inhibition of viral sialidase, its development as an anti-influenza agent is no longer envisaged. Nevertheless, as a mechanism-based irreversible inhibitor of the bacterial enzyme, it could at least be useful for investigating the intrinsic role of sialidase in infections caused by this strain. Accepted February 3, 1997; Received November 12, 1996     

The Local Origin of the Febrile Response Induced in Ferrets During Respiratory Infection with a Virulent Influenza Virus

Intranasal infection of ferrets with a virulent Clone (7a) of the recombinant influenza virus A/PR/8/34—A/England/939/69 (H₃N₂) produced a fever approximately 24 h in duration beginning about 29 h after infection. The origin of this fever has been investigated as an indication of what might happen in influenza in man.The systemic production of fever by virus interaction with phagocytes in the reticuloendothelial system appeared unlikely because insufficient virus escaped into the bloodstream. Ten half-hourly i.v. injections of 10⁸ 50%0 Egg-Bit Infectious Doses (EBID₅₀) of virus were needed to produce a fever of short duration (3-8 h). Yet, after the intranasal infection, which results in the 24 h fever, the total virus content in the nasal mucosa was less than 10⁸ EBID₅₀ before the onset of fever and only reached 10^8.5 EBID₅₀ for 4 h during fever. Also, just before or during the fever produced by intranasal infection, influenza virus antigens could not be detected by fluorescent antibody in the spleens of the animals but were detected in animals receiving a single bloodstream injection of 10⁸ EBID₅₀ of virus.Fever is more likely to result from release of leucocyte pyrogen by virus-phagocyte interaction in the upper respiratory tract. A pyrogen active in ferrets with the characteristics of leucocyte (endogenous) pyrogen was produced by incubating influenza virus with ferret peripheral phagocytes in vitro. A pyrogen with similar properties was released by incubation of nasal inflammatory cells collected from infected febrile ferrets and many of the cells were shown by fluorescent antibody to have interacted with influenza virus.     

Use of monoclonal antibodies for rapid detection of influenza a viras in nasopharyngeal secretions

Two monoclonal antibodies against influenza A virus were assessed for use as diagnostic reagents in an indirect immunofluorescence assay (IFA) of nasopharyngeal secretions. Monoclonal antibody IA-52, directed at an internal antigen, reacted with all influenza A tested. The high stability of this epitope permitted its use in a rapid IFA test, which gave results comparable to those obtained with polyclonal antibodies and viral isolation. The second monoclonal antibody, IA-279 was directed at a surface epitope (hemagglutinin); it reacted with almost all H₃ subtype strains. Positive IFA using these monoclonal antibodies permitted rapid preliminary differentiation between the current two major subtypes of influenza A virus (H₁N₁,H₃N₂).     

NS2 protein of influenza virus is found in purified virus and phosphorylated in infected cells

Summary Purified viral preparations of influenza A virus were examined for the presence of NS₂ protein hitherto considered as a viral nonstructural protein that is present only in infected cells. Analysis of purified virus by radioimmunoprecipitation with monospecific antisera to NS₂ revealed its presence in the virus particle suggesting that it is a viral structural protein. NS₂ protein was also shown to be phosphorylated in infected cells in this study. This brings the number of influenza virus phosphoproteins to three which include NP, NS₁, and NS₂. These observations raise important questions about the role of NS₂ in the replication of influenza virus.     

Mechanisms of lymphatic system-specific viral replication and its potential role in autoimmune disease

Viral infections can be fatal because of the direct cytopathic effects of the virus or the induction of a strong, uncontrolled inflammatory response. Virus and host intrinsic characteristics strongly modulate the outcome of viral infections. Recently we determined the circumstances under which enhanced replication of virus within the lymphoid tissue is beneficial for the outcome of a disease. This enforced viral replication promotes anti-viral immune activation and, counterintuitively, accelerates virus control. In this review we summarize the mechanisms that contribute to enforced viral replication. Antigen-presenting cells and CD169⁺ macrophages exhibit enforced viral replication after infection with the model viruses lymphocytic choriomeningitis virus (LCMV) and vesicular stomatitis virus (VSV). Ubiquitin-specific peptidase 18 (Usp18), an endogenous type I interferon blocker in CD169⁺ macrophages, has been identified as a proviral gene, as are B cell activating factor (BAFF) and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). Lymphotoxins (LT) strongly enhance viral replication in the spleen and lymph nodes. All these factors modulate splenic architecture and thereby promote the development of CD169⁺ macrophages. Tumor necrosis factor alpha (TNF-α) and nuclear factor kappa-light-chain-enhancer of activated B cell signaling (NF-κB) have been found to promote the survival of infected CD169⁺ macrophages, thereby similarly promoting enforced viral replication. Association of autoimmune disease with infections is evident from (1) autoimmune phenomena described during a chronic virus infection; (2) onset of autoimmune disease simultaneous to viral infections; and (3) experimental evidence. Involvement of virus infection during onset of type I diabetes is strongly evident. Epstein–Bar virus (EBV) infection was discussed to be involved in the pathogenesis of systemic lupus erythematosus. In conclusion, several mechanisms promote viral replication in secondary lymphatic organs. Identifying such factors in humans is a challenge for future studies.     

Protein analysis of defective interfering lymphocytic choriomeningitis virus and persistently infected cells.

Defective interfering (DI) lymphocytic choriomeningitis virus (LCMV) was purified from the culture fluids of BHK 21/13S and L-929 cells persistently infected with LCMV. DI LCMV sedimented in renografin-76 gradients to a density slightly less than standard (S) LCMV (1.13 vs 1.14 g/cm³). Polyacrylamide gel electrophoretic analysis of [³⁵S]methionine-labeled DI virus revealed a major 63,000-dalton polypeptide corresponding to the S virion nucleoprotein (NP), and two minor polypeptides corresponding to the S virion 54,000? and 35,000-dalton glycopeptides. No differences in polypeptide composition were detected between the DI and S virions. Exposure of cells to DI virus before S virus challenge inhibited the intracellular synthesis of the NP. Cells persistently infected with LCMV released no detectable S virus or temperature-sensitive mutants but did release DI LCMV. The production of DI LCMV by these cultures was 10? to 100-fold lower than S virus production during acute infections. These persistently infected cells contained intracytoplasmic NP, detectable by immunofluorescence, but its rate of synthesis was too low to be detected by the radiolabeling methods used. Although present in the cytoplasms, detectable viral antigens were absent from the cell membranes of many of these persistently infected cells. Thus, cells persistently infected with LCMV produce relatively low levels of DI virus which can inhibit viral protein synthesis. These factors may act to render infected cells resistant to immunosurveillance mechanisms during persistent infections in vivo.     

Appearance of Rosette-Forming Macrophages in the Lungs of Influenza Virus-Infected Mice

Approximately one fifth of the macrophages obtained from the lungs of mice infected 2 to 5 days with influenza A/HK virus were found to rosette well with either unmodified human, chicken, or guinea pig erythrocytes, but not with erythrocytes from hamsters, sheep, or mice. Rosette-forming macrophages were seldom seen in suspensions from uninfected mice (3+/-3%) or mice infected 24 h previously (3+/-3%). Rosette formation was not due to virus hemadsorption, as indicated by the failure of specific antiserum to influenza virus to block rosette formation; by the induction of comparable levels of rosette-forming macrophages in the lungs of mice infected with herpes simplex virus type 2, a nonhemadsorbing virus; and by the inhibition of rosette formation at 4 degrees C. Instead, rosette formation appeared to be directly related to macrophage elicitation or activation since nonstimulated macrophage populations such as peripheral blood monocytes, macrophages from uninfected lungs, or noninduced peritoneal macrophages were not observed to rosette to any significant extent. Furthermore, peritoneal macrophages induced with filter-sterilized normal horse serum rosetted at levels comparable to that observed with cells from infected lungs. These results indicate that hemadsorption alone can not be used as a criterion of virus infection of macrophages. However, rosette formation may serve to identify macrophage subpopulations which are active in host defense against viral infections.     

The ability of pandemic influenza virus hemagglutinins to induce lower respiratory pathology is associated with decreased surfactant protein D binding

Pandemic influenza viral infections have been associated with viral pneumonia. Chimeric influenza viruses with the hemagglutinin segment of the 1918, 1957, 1968, or 2009 pandemic influenza viruses in the context of a seasonal H1N1 influenza genome were constructed to analyze the role of hemagglutinin (HA) in pathogenesis and cell tropism in a mouse model. We also explored whether there was an association between the ability of lung surfactant protein D (SP-D) to bind to the HA and the ability of the corresponding chimeric virus to infect bronchiolar and alveolar epithelial cells of the lower respiratory tract. Viruses expressing the hemagglutinin of pandemic viruses were associated with significant pathology in the lower respiratory tract, including acute inflammation, and showed low binding activity for SP-D. In contrast, the virus expressing the HA of a seasonal influenza strain induced only mild disease with little lung pathology in infected mice and exhibited strong in vitro binding to SP-D.     

Similar frequencies of antigenic variants in Sendai, vesicular stomatitis, and influenza A viruses

The effects of three inhibitors of glycosylation (2-deoxy-d-glucose, d-glucosamine, and tunicamycin) on the formation of infectious extracellular snowshoe hare virus and the synthesis of intracellular virus-induced polypeptides have been examined. The inhibitor 2-deoxy-d-glucose, used at concentrations of up to 10 mM, did not significantly affect either infectious virus release or viral-induced polypeptide synthesis and maturation. By contrast, both d-glucosamine (40 mM) and tunicamycin (1 μg/ml) prevented the release of infectious virus and inhibited the maturation of the two viral glycoproteins (Gl and G2), but not the viral nucleoprotein (N). Two new polypeptides, Gl₀ and G2₀, of molecular weights 105 × 103 and 33 × 103, respectively, were found in infected cells treated with tunicamycin or D-glucosamine. These two polypeptides were identified as virus specific since they could be precipitated by virus immune serum. Tunicamycin was found to inhibit the release of extracellular virus particles at 33 and 38°, which correlated with the observation that no intracellular virus particles were detected in electron micrographs of cells treated with the drug.     

MHV68 Latency Modulates the Host Immune Response to Influenza A Virus

Murine gammaherpesvirus 68 (MHV68) is a natural rodent pathogen that has been used as a model to study the pathogenesis of human gammaherpesviruses. Like other herpesviruses, MHV68 causes acute infection and establishes life-long latency in the host. Recently, it has been shown that mice latently infected with MHV68 have resistance to unrelated pathogens in secondary infection models. We therefore hypothesized that latent MHV68 infection could modulate the host response to influenza A virus. To test this hypothesis, mice were infected intranasally with influenza virus following the establishment of MHV68 latency. Mice latently infected with MHV68 showed significantly higher survival to influenza A virus infection than did PBS mock-infected mice. Latent MHV68 infection led to lower influenza viral loads and decreased inflammatory pathology in the lungs. Alveolar macrophages of mice latently infected with MHV68 showed activated status, and adoptive transfer of those activated macrophages into mice followed the infection with influenza A virus had significantly greater survival rates than control mice, suggesting that activated alveolar macrophages are a key mechanistic component in protection from secondary infections.     

Surfactant protein A,but not surfactant protein D,is an opsonin for influenza A virus phagocytosis by rat alveolar macrophages

Surfactant protein A (SP-A) and surfactant protein D (SP-D) are collectins, and both proteins were shown to interact with influenza A virus and alveolar macrophages. However, it is not known whether SP-A and SP-D can serve as opsonins for the phagocytosis of influenza A virus by alveolar macrophages. In the present study, we investigated the opsonic activities of SP-A and SP-D for phagocytosis of fluorescein isothiocyanate (FITC)-labeled influenza A (H3N2) virus by rat alveolar macrophages using flow cytometry. SP-A enhanced the association of the virus with macrophages in a dose-dependent manner, reaching a maximum at an SP-A concentration of 60 μg/ml. An approximate threefold increase in association of influenza A virus with alveolar macrophages in the presence of SP-A over control incubations which contained no SP-A was observed. Half of the total cell-associated fluorescence could be quenched as demonstrated using the extracellular quenching dye trypan blue. These results indicate that SP-A mediates internalization of FITC-labeled influenza A (H3N2) virus by alveolar macrophages. Removal of the carbohydrate moiety of SP-A by N-glycosidase F treatment or cleavage of its sialic acid residues by neuraminidase abolished the enhancement of the phagocytosis of FITC-labeled influenza A virus by alveolar macrophages. Mannan, a mannose homopolysaccharide known to bind to the carbohydrate-binding domain of SP-A, did not affect the SP-A-mediated phagocytosis of FITC-labeled influenza by alveolar macrophages. In contrast, SP-D neither enhanced the association of FITC-labeled influenza A virus with alveolar macrophages nor affected the opsonic activity of SP-A for FITC-labeled influenza A (H3N2) virus at the SP-D concentrations tested. It is concluded that SP-A acts via its sialic acid residues as an opsonin in the phagocytosis of influenza A virus by alveolar macrophages.     

Viral protein production in homogeneous and mixed infections of cytopathic and noncytopathic BVD virus

Summary Experiments were conducted to examine dual infection of cultured cells with cytopathic and noncytopathic bovine viral diarrhea virus (BVDV). Cell monolayers infected with a noncytopathic BVDV isolate and subsequently superinfected with a cytopathic BVDV isolate were refractive to the cytopathic effects of the cytopathic BVDV isolate, as reported in the literature. Immunofluorescence staining of superinfected cultures with monoclonal antibodies specific for the cytopathic or the noncytopathic viral isolate, demonstrated that cells in superinfected cultures contained both viral biotypes. Immunoprecipitation was used to compare the temporal detection of viral induced polypeptides in superinfected cultures to that of cultures infected with a single viral biotype. In single cytopathic viral infections, viral induced polypeptides of 80 kDa and 53–56 kDa are detected simultaneously, but in superinfections a 4 h gap occurred between detection of the 53–56 kDa polypeptide and detection of the 80 kDa polypeptide.     

Effect of influenza viras on phagocytic cells

Many viral infections predispose to bacterial superinfection, and it has been suggested that the increased susceptibility to bacterial infections is at least in part due to the effect of virus on the phagocytic cell function. Since the mechanisms by which the viruses affect neutrophil function are not well understood, we studied the function of polymorphonuclear leukocytes (PMNs) after incubation with influenza virus. Phagocytosis was assayed by incubating influenza virus (strain type A-Texas-77 [H₂N₂]) treated leukocytes with³H-thymidine-labelled staphylococci. The oxidative metabolism of the PMNs was studied by measuring the chemiluminescence generated by virus-treated PMNs after incubation with zymosan. Chemotaxis was measured under agarose. After incubation with 10⁷ EID₅₀ units of influenza virus, PMNs ingested only 35 % of the bacteria, whereas control leukocytes ingested over 80 %. Influenza virus also reduced the mobility of the PMNs and markedly suppressed the generation of chemiluminiscence. UV-killed virus with intact neuraminidase produced similar effects but virus with heat-inactivated neuraminidase did not. Virus envelope-neuraminidase may be responsible for some of the effects of the virus on the PMNs.     

Neonatal oxygen increases sensitivity to influenza A virus infection in adult mice by suppressing epithelial expression of Ear1

Oxygen exposure in premature infants is a major risk factor for bronchopulmonary dysplasia and can impair the host response to respiratory viral infections later in life. Similarly, adult mice exposed to hyperoxia as neonates display alveolar simplification associated with a reduced number of alveolar epithelial type II cells and exhibit persistent inflammation, fibrosis, and mortality when infected with influenza A virus. Because type II cells participate in innate immunity and alveolar repair, their loss may contribute to oxygen-mediated sensitivity to viral infection. A genomewide screening of type II cells identified eosinophil-associated RNase 1 (Ear1). Ear1 was also detected in airway epithelium and was reduced in lungs of mice exposed to neonatal hyperoxia. Electroporation-mediated gene delivery of Ear1 to the lung before infection successfully reduced viral replication and leukocyte recruitment during infection. It also diminished the enhanced morbidity and mortality attributed to neonatal hyperoxia. These findings demonstrate that novel epithelial expression of Ear1 functions to limit influenza A virus infection, and its loss contributes to oxygen-associated epithelial injury and fibrosis after infection. People born prematurely may have defects in epithelial innate immunity that increase their risk for respiratory viral infections.