Influenza Virus Infection Research Articles

Monitoring the Cascade of Monocyte-Derived Macrophages to Influenza Virus Infection in Human Alveolus Chips.

Respiratory viruses ravage the world and seriously threaten people's health. Despite intense research efforts, the immune mechanism underlying respiratory virus-induced acute lung injury (ALI) and pulmonary fibrosis (PF) has not been fully elucidated. Here, the cascade of monocyte-derived macrophages to influenza A virus infection is monitored on an optimized human alveolus chip to reveal the role of macrophages in the development of ALI and PF. We find that viral infection causes damage to the alveolar air-liquid barrier and the release of inflammatory cytokines, which induce the M0 macrophages to gather and polarize to the M1 phenotype at the damaged site through recruitment, adhesion, migration, and activation, leading to ALI. Afterward, M1 macrophages polarize into the M2 phenotype, and then transform into myofibroblasts, followed by enhanced secretion of various anti-inflammatory cytokines and profibrotic cytokines, to promote PF. Our study provides an insight into the pathogenesis of virus-induced ALI and PF, which will assist in the development of therapeutic strategies and drugs for treating influenza and other respiratory virus infections.

Influenza Vaccine Effectiveness Against Illness and Asymptomatic Infection in 2022-2023: A Prospective Cohort Study.

Previous estimates of vaccine effectiveness (VE) against asymptomatic influenza virus infection based on seroconversion have varied widely and may be biased. We estimated 2022-2023 influenza VE against illness and asymptomatic infection in a prospective cohort. In the HEROES-RECOVER cohort, adults at increased occupational risk of influenza exposure across 7 US sites provided weekly symptom reports and nasal swabs for reverse transcription-polymerase chain reaction (RT-PCR) influenza testing. Laboratory-confirmed influenza virus infections were classified as symptomatic (≥1 symptom) or asymptomatic during the week of testing. Participants reported demographic information and vaccination through surveys; most sites verified vaccination through medical record and immunization registry review. Person-time was calculated as days from the site-specific influenza season start (September-October 2022) through date of infection, study withdrawal, or season end (May 2023). We compared influenza incidence among vaccinated versus unvaccinated participants overall, by symptom status, and by influenza A subtype, using Cox proportional hazards regression adjusted for site and occupation. We estimated VE as (1 - adjusted hazard ratio) × 100%. In total, 269 of 3785 (7.1%) participants had laboratory-confirmed influenza, including 263 (98%) influenza A virus infections and 201 (75%) symptomatic illnesses. Incidence of laboratory-confirmed influenza illness among vaccinated versus unvaccinated participants was 23.7 and 33.2 episodes per 100 000 person-days, respectively (VE: 38%; 95% CI: 15%-55%). Incidence of asymptomatic influenza virus infection was 8.0 versus 11.6 per 100 000 (VE: 13%; 95% CI: -47%, 49%). Vaccination reduced incidence of symptomatic but not asymptomatic influenza virus infection, suggesting that influenza vaccination attenuates progression from infection to illness.

Trivalent oleanolic acid-glucose conjugates: Synthesis and efficacy against Influenza A virus

Influenza A virus (IAV) leads to significant morbidity and mortality due to the seasonal epidemics and spread. We have demonstrated that oleanolic acid (OA) C28 glucose conjugates and OA trimers are capable of effectively blocking the recognition and interaction between the influenza virus and host cells. In this study, a series of OA-glucose trimers were designed and synthesized through the CuAAC reaction. All trimers underwent screening for anti-IAV activities in vitro. Among these, compounds 13a and 13b showed inhibitory activity against the influenza virus, with IC50 values of 0.68 μM and 0.47 μM, respectively, demonstrating greater potency than oseltamivir (IC50 = 1.36 μM). Results from the time-of-addition experiment and hemagglutination inhibition assay suggest that these OA-glucose trimers may disrupt the recognition between the HA protein of IAV and sialic acid receptors on host cells, thus blocking viral entry. Furthermore, it was found that compound 13b effectively inhibits IAV infection in BALB/c mice. This study has elucidated the structure-activity relationships of OA trimers against the influenza virus and highlighted the utility of multivalent OA conjugates for enhancing ligand-target interactions in anti-influenza virus drug design, laying a groundwork for future research into the antiviral applications of these natural products.

Quantification of influenza virus mini viral RNAs using Cas13.

Influenza A virus (IAV) RNA synthesis produces full-length and deletion-containing RNA molecules, which include defective viral genomes (DVG) and mini viral RNAs (mvRNA). Sequencing approaches have shown that DVG and mvRNA species may be present during infection, and that they can vary in size, segment origin, and sequence. Moreover, a subset of aberrant RNA molecules can bind and activate host pathogen receptor retinoic acid-inducible gene I (RIG-I), leading to innate immune signaling and the expression of type I and III interferons. Measuring the kinetics and distribution of these immunostimulatory aberrant RNA sequences is important for understanding their function in IAV infection. Here, we explored if IAV mvRNA molecules can be detected and quantified using amplification-free, CRISPR-LbuCas13a-based detection. We show that CRISPR-LbuCas13a can be used to measure the copy numbers of specific mvRNAs in samples from infected tissue culture cells. However, to efficiently detect mvRNAs in other samples, promiscuous CRISPR guide RNAs are required that activate LbuCas13a in the presence of multiple mvRNA sequences. One crRNA was able to detect full-length IAV segment 5 without amplification, allowing it to be used for general IAV infection detection nasopharyngeal swabs. Using CRISPR-LbuCas13a, we confirm that mvRNAs are present in ferret upper and lower respiratory tract tissue, as well as clinical nasopharyngeal swab extracts of hospitalized patients. Overall, CRISPR-LbuCas13a-based RNA detection is a useful tool for studying deletion-containing viral RNAs and it complements existing amplification-based approaches.

Viral co-detection of influenza virus and other respiratory viruses in hospitalized Brazilian patients during the first three years of the coronavirus disease (COVID)-19 pandemic: an epidemiological profile

IntroductionIn Brazil, few studies were performed regarding the co-detection of respiratory viruses in hospitalized patients. In this way, the study aimed to describe the epidemiological profile of hospitalized patients due to influenza virus infection that presented co-detection with another respiratory virus.MethodsThe epidemiological analysis was made by collecting data from Open-Data-SUS. The study comprised patients infected by the influenza A or B virus with positive co-detection of another respiratory virus, such as adenovirus, bocavirus, metapneumovirus, parainfluenza virus (types 1, 2, 3, and 4), rhinovirus, and respiratory syncytial virus (RSV). The markers [gender, age, clinical signs and symptoms, comorbidities, need for intensive care unit (ICU) treatment, and need for ventilatory support] were associated with the chance of death. The data was collected during the first three years of the coronavirus disease (COVID)-19 pandemic—from December 19, 2019, to April 06, 2023.ResultsA total of 477 patients were included, among them, the influenza A virus was detected in 400 (83.9%) cases. The co-detection occurred, respectively, for RSV (53.0%), rhinovirus (14.0%), adenovirus (13.4%), parainfluenza virus type 1 (10.7%), parainfluenza virus type 3 (5.2%), metapneumovirus (3.8%), parainfluenza virus type 2 (3.6%), bocavirus (3.4%), and parainfluenza virus type 4 (1.5%). The co-detection rate was higher in the male sex (50.7%), age between 0–12 years of age (65.8%), and white individuals (61.8%). The most common clinical symptoms were cough (90.6%), dyspnea (78.8%), and fever (78.6%). A total of 167 (35.0%) people had at least one comorbidity, mainly cardiopathy (14.3%), asthma (8.4%), and diabetes mellitus (7.3%). The need for ICU treatment occurred in 147 (30.8%) cases, with most of them needing ventilatory support (66.8%), mainly non-invasive ones (57.2%). A total of 33 (6.9%) patients died and the main predictors of death were bocavirus infection (OR = 14.78 [95%CI = 2.84–76.98]), metapneumovirus infection (OR = 8.50 [95%CI = 1.86–38.78]), race (other races vs. white people) (OR = 3.67 [95%CI = 1.39–9.74]), cardiopathy (OR = 3.48 [95%CI = 1.13–10.71]), and need for ICU treatment (OR = 7.64 [95%CI = 2.44–23.92]).ConclusionCo-detection between the influenza virus and other respiratory viruses occurred, mainly with RSV, rhinovirus, and adenovirus being more common in men, white people, and in the juvenile phase. Co-detection of influenza virus with bocavirus and metapneumovirus was associated with an increased chance of death. Other factors such as race, cardiopathy, and the need for an ICU were also associated with a higher chance of death.

A human monoclonal antibody targeting the monomeric N6 neuraminidase confers protection against avian H5N6 influenza virus infection

The influenza neuraminidase (NA) is a potential target for the development of a next-generation influenza vaccine, but its antigenicity is not well understood. Here, we isolate an anti-N6 human monoclonal antibody, named 18_14D, from an H5N6 avian influenza virus (AIV) infected patient. The antibody weakly inhibits enzymatic activity but confers protection in female mice, mainly via ADCC function. The cryo-EM structure shows that 18_14D binds to a unique epitope on the lateral surface of the N6 tetramer, preventing the formation of tightly closed NA tetramers. These findings contribute to the molecular understanding of protective immune responses to NA of AIVs in humans and open an avenue for the rational design of NA-based vaccines.

Differential transcriptomic host responses in the early phase of viral and bacterial infections in human lung tissue explants ex vivo

BackgroundThe first 24 h of infection represent a critical time window in interactions between pathogens and host tissue. However, it is not possible to study such early events in human lung during natural infection due to lack of clinical access to tissue this early in infection. We, therefore, applied RNA sequencing to ex vivo cultured human lung tissue explants (HLTE) from patients with emphysema to study global changes in small noncoding RNA, mRNA, and long noncoding RNA (lncRNA, lincRNA) populations during the first 24 h of infection with influenza A virus (IAV), Mycobacterium bovis Bacille Calmette-Guerin (BCG), and Pseudomonas aeruginosa.ResultsPseudomonas aeruginosa caused the strongest expression changes and was the only pathogen that notably affected expression of microRNA and PIWI-associated RNA. The major classes of long RNAs (> 100 nt) were represented similarly among the RNAs that were differentially expressed upon infection with the three pathogens (mRNA 77–82%; lncRNA 15–17%; pseudogenes 4–5%), but lnc-DDX60-1, RP11-202G18.1, and lnc-THOC3-2 were part of an RNA signature (additionally containing SNX10 and SLC8A1) specifically associated with IAV infection. IAV infection induced brisk interferon responses, CCL8 being the most strongly upregulated mRNA. Single-cell RNA sequencing identified airway epithelial cells and macrophages as the predominant IAV host cells, but inflammatory responses were also detected in cell types expressing few or no IAV transcripts. Combined analysis of bulk and single-cell RNAseq data identified a set of 6 mRNAs (IFI6, IFI44L, IRF7, ISG15, MX1, MX2) as the core transcriptomic response to IAV infection. The two bacterial pathogens induced qualitatively very similar changes in mRNA expression and predicted signaling pathways, but the magnitude of change was greater in P. aeruginosa infection. Upregulation of GJB2, VNN1, DUSP4, SerpinB7, and IL10, and downregulation of PKMYT1, S100A4, GGTA1P, and SLC22A31 were most strongly associated with bacterial infection.ConclusionsHuman lung tissue mounted substantially different transcriptomic responses to infection by IAV than by BCG and P. aeruginosa, whereas responses to these two divergent bacterial pathogens were surprisingly similar. This HLTE model should prove useful for RNA-directed pathogenesis research and tissue biomarker discovery during the early phase of infections, both at the tissue and single-cell level.

The Global Trend of Drug Resistant Sites in Influenza A Virus Neuraminidase Protein from 2011 to 2020.

Influenza A virus (IAV) causes highly contagious respiratory disease worldwide, so prevention and control of IAV is extremely important. However, overuse of neuraminidase inhibitor (NAI) drugs leads to drug resistance. To explore the up-to-date geographical distribution and evolution of drug-resistant mutations (DRMs) in the NA protein of IAV, 81,492 near full-length NA sequences downloaded from NCBI and GISAID databases, including 34,481 H1N1 and 46,622 H3N2, were processed and analyzed. Our results showed the annual number of NA sequences from 2011 to 2019 continuously increased. Meanwhile, almost 85% of sequences were from developed countries in North America, Europe and Asia. Clustering analysis demonstrated H3N2 varied more than H1N1. Notably, H3N2 exhibited a higher frequency of DRMs than H1N1, with prevailing DRMs mainly located at non-active sites within the NA protein. Phylogenetic analyses showed NA harboring DRMs collected in the same year and from the same location clustered together, which may be related to the local economic level, clinical monitoring of DRMs and research level. Consequently, it is imperative to enhance global surveillance targeting drug resistance in IAV infections which can mitigate the transmission of drug-resistant strains. In summary, our research provides valuable insights for clinical medication while establishing a robust scientific basis for IAV prevention and treatment strategies to improve overall efficacy.

Influence of Donor-Specific Characteristics on Cytokine Responses in H3N2 Influenza A Virus Infection: New Insights from an Ex Vivo Model.

Influenza A virus (IAV) is known for causing seasonal epidemics ranging from flu to more severe outcomes like pneumonia, cytokine storms, and acute respiratory distress syndrome. The innate immune response and inflammasome activation play pivotal roles in sensing, preventing, and clearing the infection, as well as in the potential exacerbation of disease progression. This study examines the complex relationships between donor-specific characteristics and cytokine responses during H3N2 IAV infection using an ex vivo model. At 24 h post infection in 31 human lung explant tissue samples, key cytokines such as interleukin (IL)-6, IL-10, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ) were upregulated. Interestingly, a history of lung cancer did not impact the acute immune response. However, cigarette smoking and programmed death-ligand 1 (PD-L1) expression on macrophages significantly increased IL-2 levels. Conversely, age inversely affected IL-4 levels, and diabetes mellitus negatively influenced IL-6 levels. Additionally, both diabetes mellitus and programmed cell death protein 1 (PD-1) expression on CD3+/CD4+ T cells negatively impacted TNF-α levels, while body mass index was inversely associated with IFN-γ production. Toll-like receptor 2 (TLR2) expression emerged as crucial in mediating acute innate and adaptive immune responses. These findings highlight the intricate interplay between individual physiological traits and immune responses during influenza infection, underscoring the importance of tailored and personalized approaches in IAV treatment and prevention.

Melanin concentrating hormone regulates the JNK/ERK signaling pathway to alleviate influenza A virus infection-induced neuroinflammation

Melanin concentrating hormone (MCH) controls many brain functions, such as sleep/wake cycle and memory, and modulates the inflammation response. Previous studies have shown that influenza A virus (IAV) infection-induced neuroinflammation leads to central nervous damage. This study investigated the potential effects of MCH against neuroinflammation induced by IAV infection and its mechanism. MCH (1 and 2 mg/ml) was administrated for 5 consecutive days before IAV infection. Pentobarbital-induced sleep tests, an open-field test, and a Morris water maze were performed to measure sleep quality, spatial learning and memory ability. Neuronal loss and microglial activation were observed with Nissl staining and immunofluorescence assay. The levels of inflammatory cytokines and the expression of the JNK/ERK signaling pathway were examined by ELISA and western blot. IAV infection led to poor sleep quality, impaired the ability of spatial learning and memory, caused neuronal loss and microglial activation in mice’s hippocampus and cortex. Meanwhile the level of inflammatory cytokines increased, and the JNK/ERK signaling pathway was activated after IAV infection. MCH administration significantly alleviated IAV-induced neuroinflammation, cognitive impairment, and sleep disorder, decreased the levels of inflammatory cytokines, and inhibited neuronal loss and microglial activation in the hippocampus and cortex by regulating the JNK/ERK signaling pathway. Therefore, MCH alleviated the neuroinflammation, spatial learning and memory impairment, and sleep disorder in IAV-infected mice by regulating the JNK/ERK signaling pathway.

Comparative study on the epidemiological characteristics and hazards of respiratory syncytial virus and influenza virus infections among elderly people

ObjectiveTo investigate the epidemiological characteristics and infections of respiratory syncytial virus (RSV) and influenza viruses in hospitalized elderly patients with respiratory tract infections in Suzhou City, China, and to compare the differences in clinical characteristics and economic burden associated with these two infections.MethodsIn this prospective study, pathogenetic testing and clinical data for hospitalized patients aged 60 years and older with respiratory tract infections were collected in five hospitals through stratified cluster sampling from December 2023 to May 2024. Comparative study on epidemic characteristics, clinical features and costs of cases who infected RSV alone and influenza alone were conducted.ResultsAmong 1,894 cases included, the RSV positivity rate was 5.91% during the 2023–2024 winter-spring season, while the influenza positivity rate was 9.61%. RSV-B was the predominant subtype of RSV, and influenza A (primarily H3N2) was the dominant strain among the influenza-positive cases. Compared with cases infected influenza virus alone, those infected RSV alone had lower occurrence frequency of fever (18.8% vs. 35.7%, P = 0.004), higher occurrence frequency of complications of lower respiratory tract infections (70.8% vs. 54.8%, P = 0.011), higher direct medical costs ($996.2 vs. $841.1, P = 0.017) and total costs ($1019.7 vs. $888.1, P = 0.036). RSV single infection is more common in female cases (P = 0.007) and diabetic cases (P = 0.007) than influenza virus single infection.ConclusionsDuring the winter and spring months, RSV is the second most common pathogen after influenza virus among older adults hospitalized for respiratory infections in Suzhou, China. Patients infected RSV are more likely to develop complications with lower respiratory tract infections and have higher medical costs than the influenza. RSV infection in the elderly should be emphasized, especially in female patients and diabetic patients.

A tentative exploration for the association between influenza virus infection and SARS-CoV-2 infection in Shihezi, China: A test-negative study

The outbreak of respiratory diseases, such as COVID-19 and influenza, has drawn global attention. However, it remains unclear whether the risk of influenza A infection may be affected by the history of SARS-CoV-2 infection. In this study, we conducted a test-negative case-control study, and utilized a logistic regression model to analyze the relationship between SARS-CoV-2 and influenza A infections. Among 258 eligible patient samples with influenza-like illness (ILI), we did not detect a statistically significant association between the history of SARS-CoV-2 infection and the risk of influenza A infection. These findings might indicate that antibodies against COVID-19 acquired through vaccination or natural immunity have not protected against influenza.

Ruhao Dashi granules exert therapeutic effects on H1N1 influenza virus infection by altering intestinal microflora composition.

Antiviral medications for influenza could be ineffective due to the emergence of resistant influenza virus strains. Ruhao Dashi (RHDS) granules possess anti-inflammatory and antibacterial effects. The present study aimed to determine the efficacy of RHDS granules in treating influenza-infected mice and the mechanism underlying this treatment as well as its effect on the intestinal flora composition of the infected mice. The HPLC-UV method was used to identify the active components of RHDS granules. ICR mice were infected with influenza A virus (IAV) H1N1 subtype through a nasal drip. After the influenza mice model was successfully established, the pathological changes in the lungs were observed for 5 days after gavage treatment with 0.9% sterile saline and low, medium, and high doses (0.07, 0.14, and 0.28 g/mL, respectively) of RHDS granules. The serum levels of the cytokines IL-6 and TNF-α and sIgA were detected by ELISA. Real-time fluorescence quantitative PCR and western blotting assay were performed to determine the expression levels of the tight junction (TJ) proteins claudin-1, occludin, and zonula occludens-1 (ZO-1) in colon tissues. Furthermore, 16S rRNA gene sequencing of feces samples was conducted to assess the effect of RHDS granules on the gut microbiota. RHDS granules exerted a protective effect on the lung tissues of IAV-infected mice; moreover, the granules reduced the synthesis of proinflammatory cytokines and increased the relative expression levels of claudin-1, occludin, and ZO-1 in colon tissues. Furthermore, RHDS granule treatment increased the relative abundance of Lactobacillus, Akkermansia, and Faecalibaculum and decreased the relative abundance of Muribaculaceae; thus, RHDS granules could stabilize the intestinal microbiota to some extent. RHDS granules exert a therapeutic effect on IAV-infected mice probably by modifying the structural composition of their intestinal microbiota.

Enhancement of protective efficacy of recombinant attenuated Salmonella typhimurium delivering H9N2 avian influenza virus hemagglutinins(HA) antigen vaccine candidate strains by C-C motif chemokine ligand 5 in chickens(chCCL5)

The H9N2 inactivated avian influenza vaccine cannot induce cellular and mucosal immune responses, while the attenuated Salmonella vector as an intracellular bacterium can induce dominant cellular and mucosal immune responses. However, it provides low protection against the virus when delivering viral antigens and needs further optimization. Chicken C-C motif chemokine ligand 5 (chCCL5) is an important CC chemokine associated with immune cell chemotaxis, migration, and viral infection. This study connected the sequence of chCCL5 (CCL5) with the hemagglutinin sequence of the H9N2 avian influenza virus (yH9HA), utilizing the attenuated Salmonella typhimurium vector containing the delayed lysis system MazE/F regulated by arabinose as a carrier. A vaccine strain of recombinant attenuated Salmonella typhimurium and H9N2 avian influenza virus HA, rSC0130 (pS0017-yH9HA-CCL5), was successfully constructed. The experimental results indicate that yH9HA-CCL5 can be expressed in 293 T cells; compared to the strain without CCL5, rSC0130 (pS0017-yH9HA-CCL5) can induce significantly increased cellular immune responses and provide better protective effects in H9N2 virus challenge experiments. The above results indicate that chCCL5 can significantly enhance the protective effect of Salmonella delivering H9N2 avian influenza virus HA protein vaccine against H9N2 avian influenza virus infection, providing valuable theoretical support for further improving the protective efficiency of recombinant attenuated Salmonella vectors for delivering viral antigens.

Modelling and investigating memory immune responses in infectious disease. Application to influenza a virus and sars-cov-2 reinfections

Understanding effector and memory immune responses against influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and re-infections is extremely important, given that they are now endemic in the community. The goal of this study is to investigate the role of memory cells and antibodies in the immune responses against IAV and SARS-CoV-2 re-infections. To this end, we adapt a previously-published within-host mathematical model (Sadria & Layton, 2021) for the primary immune response against SARS-CoV-2 infections, by including two types of memory immune cells, i.e., memory CD8+ T-cells and memory B-cells, and by parametrising the new model with values specific to the two viruses. We first investigate the long-term dynamics of the model by identifying the virus-free steady states and studying the conditions that ensure the stability of these states. Then, we investigate the transient dynamics of this in-host model by simulating different viral reinfection times: 20 days, 60 days and 400 days after the first encounter with the pathogen. This allows us to highlight which memory immune components have the greatest impact on the viral elimination depending on the time of reinfection. Our results suggest that memory immune responses have a greater impact in the case of IAV infections compared to SARS-CoV-2 infections. Moreover, we observe that the immune response after a secondary infection is more efficient when the reinfection occurs at a shorter time.

Recent advances in the influenza virus vaccine landscape: a comprehensive overview of technologies and trials.

SUMMARYIn the United Kingdom (UK) in 2022/23, influenza virus infections returned to the levels recorded before the COVID-19 pandemic, exerting a substantial burden on an already stretched National Health Service (NHS) through increased primary and emergency care visits and subsequent hospitalizations. Population groups ≤4 years and ≥65 years of age, and those with underlying health conditions, are at the greatest risk of influenza-related hospitalization. Recent advances in influenza virus vaccine technologies may help to mitigate this burden. This review aims to summarize advances in the influenza virus vaccine landscape by describing the different technologies that are currently in use in the UK and more widely. The review also describes vaccine technologies that are under development, including mRNA, and universal influenza virus vaccines which aim to provide broader or increased protection. This is an exciting and important era for influenza virus vaccinations, and advances are critical to protect against a disease that still exerts a substantial burden across all populations and disproportionately impacts the most vulnerable, despite it being over 80 years since the first influenza virus vaccines were deployed.

A-239 Cxcl10 induced gut dysbiosis exacerbates acute lung injury and secondary infection in influenza by inhibiting il22

Abstract Background Secondary infections are the most cause of severe pulmonary injury and death in influenza. CXCL10, known as interferon γ-induced protein 10(IP-10), is highly upregulated in response to IFN-γstimulation during influenza. Previous studies show that CXCL10 contributes to bacteria co-infections and worse finales in influenza. However, the underlying mechanisms by which CXCL10 facilitate secondary infections remains unclear. Emerging evidences show that influenza virus infections disturb the composition and function of gut microbiota, which in turn influences the infection process. Herein, we aimed to explore whether CXCL10 could affect the progress of influenza infection and secondary infection in a gut microbiota dependent manner. Methods CXCL10 knockout mice were used to determine the role of CXCL10 in staphylococcus aureus co-infection after influenza A virus (IAV) infection. Lung tissues from CXCL10 knockout mice were collected for Transcriptomics sequencing. Feces from mice and clinicals including IAV patients and healthy individuals were collected for Metagenomic sequencing. Paired serum samples were collected for Metabolomic sequencing. QRT-PCR was performed to determine the expression of inflammatory factors in lung tissues from CXCL10 knockout mice. Elisa assays were used to measure the serum expression levels of CXCL10 and IL22. Flow cytometry was applied to detect the proportion of IL22+ cells. Fecal microbiota transplantation (FMT) was applied to confirm that CXCL10 plays an adverse role in acute lung injury and staphylococcus aureus co-infection after IAV infection by disrupting intestinal microbiome homeostasis. Results CXCL10 aggravated acute lung injury and promoted staphylococcus aureus coinfection after IAV infection. Transcriptomics sequencing results suggests improved cell membrane integrity and regeneration of epithelial cells after IAV infection in CXCL10 knockout mice with an upregulation of integrity proteins. CXCL10 knockout significantly increased the expression levels of IL22 without influencing virus duplication. rh-IL22 protects lung epithelial cell from staphylococcus aureus co-infection in influenza and increased the expression of tight junction proteins. The gut microbiome shows different structures between wild type mice and knockout mice, as well as clinical samples according to serum CXCL10 expression levels. We found some genera were markedly increased in knockout mice and patients with low serum CXCL10 expression levels including Lactobacillus, Lachnospiraceae, Oscillibacter, Odoribacter, Eubacterium. FMT from patients with low serum CXCL10 levels and healthy individuals ameliorating lung pathological damage. Conclusions This study interpreted that CXCL10 exacerbates acute lung injury and secondary infection in influenza by inducing gut dysbiosis, suggesting that balancing the gut flora could be assistant treatments to protect from acute lung injury and secondary infections in influenza. And IL22 may be a potential mediating factor between gut-lung axis to improve epithelial integrity.

Gestational influenza A virus infection elicits nonresolving vascular dysfunction and T-cell accumulation in the aorta of mice.

T-cell accumulation within the aorta promotes endothelial dysfunction and the genesis of cardiovascular disease, including hypertension and atherosclerosis. Viral infection during pregnancy is also known to mediate marked acute endothelial dysfunction, but it is not clear whether T cells are recruited to the aorta and whether the dysfunction persists postpartum. Here, we demonstrate that influenza A virus (IAV) infection during pregnancy in a murine model resulted in endothelial dysfunction of the aorta, which persisted for up to 60 days postinfection and was associated with higher levels of IFN-γ mRNA expression within the tissue. In the absence of infection, low numbers of naïve CD4+ and CD8+ T cells, central memory T cells, and effector memory T cells were observed in the aorta. However, with IAV infection, these T-cell subsets were significantly increased with a notable accumulation of IAV-specific CD8+ effector memory T cells. Critically, this increase was maintained out to at least 60 days. In contrast, IAV infection in nonpregnant female mice resulted in modest endothelial dysfunction with no accumulation of T cells within the aorta. These data, therefore, demonstrate that the aorta is a site of T-cell recruitment and retention after IAV infection during pregnancy. Although IAV-specific memory T cells could theoretically confer protection against future influenza infection, nonspecific memory T-cell activation and IFN-γ production in the aorta could also contribute to future endothelial dysfunction and cardiovascular disease.NEW & NOTEWORTHY Pregnancy is a risk factor for cardiovascular complications to influenza A virus (IAV) infection. We demonstrate that gestational IAV infection caused endothelial dysfunction of the maternal aorta, which persisted for 60 days postinfection in mice. Various T cells accumulated within the aorta at 60 days because of the infection, and this was associated with elevated levels of the proinflammatory cytokine, IFN-γ. Our study demonstrates a novel "long influenza" cardiovascular phenotype in female mice.

Detection of H1N1 Influenza Virus in the Bile of a Severe Influenza Mouse Model.

Influenza virus infection may lead to fatal complications including multi-organ failure and sepsis. The influenza virus was detected in various extra-pulmonary organs in autopsy studies during the 2009 pandemic. However, limited research has been conducted on the presence of viral particle or viral components in the peripheral blood. We established a mouse model for severe H1N1 influenza. The bile and blood samples were collected over time and inoculated into embryonated chicken eggs. We detected live influenza virus in bile and blood samples in early infection. Immunofluorescence showed influenza viral components in the liver tissue. No live virus was isolated in the bile in mice intragastrically administered with influenza virus, indicating that the virus was spread from the blood stream. Targeted metabolomics analysis of bile acid and liver tissues showed that a secondary bile acid (3-dehydrocholic acid) was decreased after influenza H1N1 infection. Genes related with fatty acid metabolism and bile secretion pathways were down-regulated in liver after influenza virus infection. Our study indicated that influenza virus viremia is present in severe influenza, and that the liver is a target organ for influenza viral sepsis.

FBXL19 in endothelial cells protects the heart from influenza A infection by enhancing antiviral immunity and reducing cellular senescence programs.

Influenza A virus (IAV) infection while primarily affecting the lungs, is often associated with cardiovascular complications. However, the mechanisms underlying this association are not fully understood. Here, we investigated the potential role of FBXL19, a member of the Skp1-Cullin-1-F-box family of E3 ubiquitin ligase, in IAV-induced cardiac inflammation. We demonstrated that FBXL19 overexpression in endothelial cells (ECs) reduced viral titers and IAV matrix protein 1 (M1) levels while increasing antiviral gene expression, including interferon (IFN)-α, -β, and -γ and RANTES (regulated on activation normal T cell expressed and secreted) in the cardiac tissue of IAV-infected mice. Moreover, EC-specific overexpression of FBXL19 attenuated the IAV infection-reduced interferon regulatory factor 3 (IRF3) level without altering its mRNA level and suppressed cardiac inflammation. Furthermore, IAV infection triggered cellular senescence programs in the heart as indicated by the upregulation of p16 and p21 mRNA levels and the downregulation of lamin-B1 levels, which were partially reversed by FBXL19 overexpression in ECs. Our findings indicate that EC-specific overexpression of FBXL19 protects against IAV-induced cardiac damage by enhancing interferon-mediated antiviral signaling, reducing cardiac inflammation, and suppressing cellular senescence programs.NEW & NOTEWORTHY Our study reveals a novel facet of IAV infection, demonstrating that it can trigger cellular senescence within the heart. Intriguingly, upregulation of endothelial FBXL19 promotes host innate immunity, reduces cardiac senescence, and diminishes inflammation. These findings highlight the therapeutic potential of targeting FBXL19 to mitigate IAV-induced cardiovascular complications.