Inflammatory impact of IFN-γ in CD8+ T cell-mediated lung injury is mediated by both Stat1-dependent and -independent pathways

AMG487 alleviates influenza A (H1N1) virus-induced pulmonary inflammation through decreasing IFN-γ-producing lymphocytes and IFN-γ concentrations

BACKGROUND AND PURPOSE

Severe influenza virus-infected patients have high systemic levels of Th1 cytokines (including IFN-γ). Intrapulmonary IFN-γ increases pulmonary IFN-γ-producing T lymphocytes through the CXCR3 pathway. Virus-infected mice lacking IP-10/CXCR3 demonstrate lower pulmonary neutrophilic inflammation. AMG487, an IP-10/CXCR3 antagonist, ameliorates virus-induced lung injury in vivo through decreasing viral loads. This study examined whether AMG487 could treat H1N1 virus-induced mouse illness through reducing viral loads or decreasing the number of lymphocytes or neutrophils.

EXPERIMENTAL APPROACH

Here, we studied the above-mentioned effects and underlying mechanisms in vivo.

KEY RESULTS

H1N1 virus infection caused bad overall condition and pulmonary inflammation characterized by the infiltration of lymphocytes and neutrophils. From Day-5 to Day-10 post-virus infection, bad overall condition, pulmonary lymphocytes, and IFN-γ concentrations increased, while pulmonary H1N1 viral titres and neutrophils decreased. Both anti-IFN-γ and AMG487 alleviated virus infection-induced bad overall condition and pulmonary lymphocytic inflammation. Pulmonary neutrophilic inflammation was mitigated by AMG487 on Day-5 post-infection, but was not mitigated by AMG487 on Day-10 post-infection. H1N1 virus induced increases of IFN-γ, IP-10, and IFN-γ-producing lymphocytes and activation of the Jak2-Stat1 pathways in mouse lungs, which were inhibited by AMG487. Anti-IFN-γ decreased IFN-γ and IFN-γ-producing lymphocytes on Day-5 post-infection. AMG487 but not anti-IFN-γ decreased viral titres in mouse lung homogenates or BALF. Higher virus load did not increase pulmonary inflammation and IFN-γ concentrations when mice were treated with AMG487.

CONCLUSION AND IMPLICATIONS

AMG487 may ameliorate H1N1 virus-induced pulmonary inflammation through decreasing IFN-γ-producing lymphocytes rather than reducing viral loads or neutrophils.

Exploring immune-related pathogenesis in lung injury: Providing new insights Into ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a significant global burden of morbidity and mortality, with lung injury being the primary cause of death in affected patients. The pathogenesis of lung injury, however, remains a complex issue. In recent years, the role of the immune system in lung injury has attracted extensive attention worldwide. Despite advancements in our understanding of various lung injury subtypes, significant limitations persist in both prevention and treatment. This review investigates the immunopathogenesis of ALI/ARDS, aiming to elucidate the pathological processes of lung injury mediated by dendritic cells (DCs), natural killer (NK) cells, phagocytes, and neutrophils. Furthermore, the article expounds on the critical contributions of gut microbiota, inflammatory pathways, and cytokine storms in the development of ALI/ARDS.

Construction of an inhalable recombinant M2e-FP-expressing Bacillus subtilis spores-based vaccine and evaluation of its protection efficacy against influenza in a mouse model

Influenza A virus (IAV) is a deadly zoonotic pathogen that remains a burden to global health systems despite continuous vaccinations, indicating the need for an improved vaccine strategy. In this work, we constructed a new recombinant influenza vaccine using Bacillus subtilis spores expressing M2e-FP protein (RSM2eFP) and assessed its potency and efficacy in BALB/c mouse immunized via aerosolized intratracheal inoculation (i.t.) or intragastric (i.g.) administration. Immunization via i.t. route conferred 100 % protection against 20 × LD50 A/PR/8/34 (H1N1) virus compared with only 50 % via the i.g. route. Even when challenged with 40 × LD50 virus, the RSM2eFP vaccine immunized via i.t. provided 80 % protection. Consistently, i.t. inoculation of RSM2eFP spore vaccine induced a stronger lung mucosal immune response and a greater cellular immune response than i.g. administration, as indicated by the high production of IgG and SIgA. In addition, the RSM2eFP spore vaccine diminished the yield of infectious virus in the lung of mice immunized via i.t. These results suggest that i.t. immunization of the RSM2eFP spore vaccine may be a promising strategy for the development of mucosal vaccines against IAV infections.

Role of Serum Amyloid A as a Biomarker for Predicting the Severity and Prognosis of COVID-19

OBJECTIVE

To detect biomarkers that can be used to predict COVID-19 severity to identify patients with high probability of disease progression and poor prognosis.

METHODS

Of the 102 patients with confirmed COVID-19 who were admitted to King Fahd General Hospital, Jeddah City, Saudi Arabia, from July 1, 2021 to August 5, 2021, 50 were included in this cross-sectional study to investigate the influence of serum amyloid A (SAA) on disease severity and survival outcomes of COVID-19 patients. Dynamic shifts in SAA, C-reactive protein (CRP), white blood cell (WBC), lymphocytes, neutrophils, biochemical markers, and disease progression were examined. At admission, and at three, five, and seven days after treatment, at least four data samples were collected from all patients, and they underwent clinical status assessments.

RESULTS

Critically ill patients showed higher SAA and CRP levels and WBC and neutrophil counts and significantly lower lymphocyte and eosinophil counts compared to the moderately/severely ill patients, especially with regard to disease progression. Similarly, nonsurvivors had higher SAA levels than survivors. The moderately/severely ill patients and the survivors had significantly higher dynamic changes in SAA compared to the critically ill patients and nonsurvivors, respectively, with differences clearly noticed on the fifth and seventh day of treatment. ROC curve analysis revealed that the combination of SAA and CRP was valuable in evaluating the disease progression and prognosis of COVID-19 patients at different time points; however, a combination of SAA and lymphocyte counts was more sensitive for disease severity prediction on admission. The most sensitive parameters for predicting survival on admission were the combination of SAA/WBC and SAA/neutrophil count.

CONCLUSIONS

The study findings indicate that SAA can be used as a sensitive indicator to assess the degree of disease severity and survival outcomes of COVID-19 patients.

Modulating cholesterol-rich lipid rafts to disrupt influenza A virus infection

Influenza A virus (IAV) is widely disseminated across different species and can cause recurrent epidemics and severe pandemics in humans. During infection, IAV attaches to receptors that are predominantly located in cell membrane regions known as lipid rafts, which are highly enriched in cholesterol and sphingolipids. Following IAV entry into the host cell, uncoating, transcription, and replication of the viral genome occur, after which newly synthesized viral proteins and genomes are delivered to lipid rafts for assembly prior to viral budding from the cell. Moreover, during budding, IAV acquires an envelope with embedded cholesterol from the host cell membrane, and it is known that decreased cholesterol levels on IAV virions reduce infectivity. Statins are commonly used to inhibit cholesterol synthesis for preventing cardiovascular diseases, and several studies have investigated whether such inhibition can block IAV infection and propagation, as well as modulate the host immune response to IAV. Taken together, current research suggests that there may be a role for statins in countering IAV infections and modulating the host immune response to prevent or mitigate cytokine storms, and further investigation into this is warranted.

Downregulated miR-129-5p expression inhibits rat pulmonary fibrosis by upregulating STAT1 gene expression in macrophages

OBJECTIVE

This study investigated the mechanism by which microRNA-129-5p (miR-129-5p) in macrophages affects pulmonary fibrosis in rats by regulating the expression of the signal transducer and activator of transcription 1 (STAT1) gene.

METHODS

After the establishment of a pulmonary fibrosis rat model, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to detect the expression of miR-129-5p in the sham group and model group. The binding sites between miR-129-5p and STAT1 were predicted online and verified by using a dual luciferase reporter system. qRT-PCR and Western blot analyses were used to test the effect of miR-129-5p on STAT1 gene expression. M2 macrophages were isolated and induced, and exosomes were extracted. Cell proliferation was detected by EdU. Furthermore, qRT-PCR was performed to detect the expression of STAT1, collagen type I A2 (COL1A2), collagen type III A1 (COL3A1), fibronectin, and α-SMA in cells and tissues followed by the detection of CD9, CD63, CD81, CD31 and STAT1 protein expression using a Western blot analysis. The pulmonary fibrosis area was detected by Masson staining followed by the immunohistochemical detection of α-smooth muscle actin (α-SMA) and type I collagen (COL-I) expression in pulmonary fibroblasts.

RESULTS

Compared with the sham group, the expression level of miR-129-5p in the model group was significantly increased (P < 0.05). miR-129-5p was observed to negatively regulate the expression of STAT1 (P < 0.05). The in vitro cell transfection experiments showed that after inhibiting the expression of miR-129-5p, the expression of STAT1 was increased, and the proliferation of fibroblasts and pulmonary fibrosis were inhibited (all P < 0.05). Furthermore, compared with the fibroblasts without coculture, the proliferation of the fibroblasts cocultured with M2 macrophage-secreted exosomes was clearly increased, and the expression levels of COL1A2, COL3A1, fibronectin and α-SMA were significantly increased (all P < 0.05). Compared with the mimic NC-exo group, the miR-129-5p-exo group had significantly increased proliferation of fibroblasts, decreased expression of STAT1, and significantly increased expression of COL1A2, COL3A1, fibronectin and α-SMA, and M2 macrophage-secreted exosomes could carry miR-129-5p to fibroblasts. Furthermore, the in vivo experiment confirmed that the exosomes of M2 macrophages could carry miR-129-5p, which could regulate M2 macrophages with pulmonary fibrosis in vivo.

CONCLUSION

M2 macrophages can carry miR-129-5p to pulmonary interstitial fibroblasts and inhibit STAT1 gene expression, which may lead to the proliferation of fibroblasts and promote pulmonary fibrosis. The downregulation of miR-129-5p can significantly promote STAT1 gene expression in macrophages to inhibit pulmonary fibrosis in rats.

Interferon-γ Preferentially Promotes Necroptosis of Lung Epithelial Cells by Upregulating MLKL

Necroptosis, a form of programmed lytic cell death, has emerged as a driving factor in the pathogenesis of acute lung injury (ALI). As ALI is often associated with a cytokine storm, we determined whether pro-inflammatory cytokines modulate the susceptibility of lung cells to necroptosis and which mediators dominate to control necroptosis. In this study, we pretreated/primed mouse primary lung epithelial and endothelial cells with various inflammatory mediators and assessed cell type-dependent responses to different necroptosis inducers and their underlying mechanisms. We found that interferon-γ (IFNγ) as low as 1 ng/mL preferentially promoted necroptosis and accelerated the release of damage-associated molecular patterns from primary alveolar and airway epithelial cells but not lung microvascular endothelial cells. Type-I IFNα was about fifty-fold less effective than IFNγ. Conversely, TNFα or agonists of Toll-like receptor-3 (TLR3), TLR4, TLR7 and TLR9 had a minor effect. The enhanced necroptosis in IFNγ-activated lung epithelial cells was dependent on IFNγ signaling and receptor-interacting protein kinase-3. We further showed that necroptosis effector mixed lineage kinase domain-like protein (MLKL) was predominantly induced by IFNγ, contributing to the enhanced necroptosis in lung epithelial cells. Collectively, our findings indicate that IFNγ is a potent enhancer of lung epithelial cell susceptibility to necroptosis.

Restriction of viral replication, rather than T cell immunopathology, drives lethality in MNV CR6-infected STAT1-deficient mice

Recent evidence indicates that viral components of the microbiota can contribute to intestinal homeostasis and protection from local inflammatory or infectious insults. However, host-derived mechanisms that regulate the virome remain largely unknown. Here, we use colonization with the model commensal murine norovirus (MNV CR6) to interrogate host-directed mechanisms of viral regulation, and show that STAT1 is a central coordinator of both viral replication and antiviral T cell responses. In addition to restricting CR6 replication to the intestinal tract, we show that STAT1 regulates antiviral CD4⁺ and CD8⁺ T cell responses, and prevents systemic viral-induced tissue damage and disease. Despite altered T cell responses that resemble those that mediate lethal immunopathology in systemic viral infections in STAT1-deficient mice, depletion of adaptive immune cells and their associated effector functions had no effect on CR6-induced disease. However, therapeutic administration of an antiviral compound limited viral replication, preventing viral-induced tissue damage and death without impacting the generation of inflammatory antiviral T cell responses. Collectively, our data show that STAT1 restricts MNV CR6 replication within the intestinal mucosa, and that uncontrolled viral replication mediates disease rather than the concomitant development of dysregulated antiviral T cell responses in STAT1-deficient mice. Importance The intestinal microbiota is a collection of bacteria, archaea, fungi and viruses that colonize the mammalian gut. Co-evolution of the host and microbiota has required development of immunological tolerance to prevent ongoing inflammatory responses against intestinal microbes. Breakdown of tolerance to bacterial components of the microbiota can contribute to immune activation and inflammatory disease. However, the mechanisms that are necessary to maintain tolerance to viral components of the microbiome, and the consequences of loss of tolerance, are less well understood. Here, we show that STAT1 is integral for preventing escape of a commensal-like virus, murine norovirus CR6 (MNV CR6) from the gut, and that in the absence of STAT1, mice succumb to infection-induced disease. In contrast to other systemic viral infections, mortality of STAT1-deficient mice is not driven by immune-mediated pathology. Our data demonstrates the importance of host-mediated geographical restriction of commensal-like viruses.

Regulation of Lysosomal Associated Membrane Protein 3 (LAMP3) in Lung Epithelial Cells by Coronaviruses (SARS-CoV-1/2) and Type I Interferon Signaling

Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2) infection is a major risk factor for mortality and morbidity in critical care hospitals around the world. Lung epithelial type II cells play a major role in the recognition and clearance of respiratory viruses as well as repair of lung injury in response to environmental toxicants. Gene expression profiling studies revealed that mouse lung epithelial type II cells express several cell-specific markers including surfactant proteins and Lysosomal associated membrane protein 3 (LAMP3) located in lysosomes, endosomes and lamellar bodies. These intracellular organelles are involved in vesicular transport and facilitate viral entry and release of the viral genome into the host cell cytoplasm. In this study, regulation of LAMP3 expression in human lung epithelial cells by several respiratory viruses and type I interferon signaling was investigated. Respiratory viruses including SARS-CoV-1 and SARS-CoV-2 significantly induced LAMP3 expression in lung epithelial cells within 24 hours after infection that required the presence of ACE2 viral entry receptors. Time course experiments revealed that the induced expression of LAMP3 was correlated with the induced expression of Interferon–beta (IFNB1) and STAT1 at mRNA levels. LAMP3 was also induced by direct IFN-beta treatment in multiple lung epithelial cell lines or by infection with influenza virus lacking the non-structural protein1(NS1) in NHBE bronchial epithelial cells. LAMP3 expression was also induced by several respiratory viruses in human lung epithelial cells including RSV and HPIV3. Location in lysosomes and endosomes aswell as induction by respiratory viruses and type I Interferon suggests that LAMP3 may have an important role in inter-organellar regulation of innate immunity and a potential target for therapeutic modulation in health and disease. Furthermore, bioinformatics revealed that a subset of lung type II genes were differentially regulated in the lungs of COVID-19 patients.

Regulation of early growth response-1 (Egr-1) gene expression by Stat1-independent type I interferon signaling and respiratory viruses

Respiratory virus infection is one of the leading causes of death in the world. Activation of the Jak-Stat pathway by Interferon-alpha/beta (IFN-α/β) in lung epithelial cells is critical for innate immunity to respiratory viruses. Transcriptional factor profiling in the transcriptome and RNA analysis revealed that Early growth response-1 (EGR1/Egr-1) was rapidly induced by IFN-α/β and Toll-like receptor (TLR) ligands in multiple cell types. Studies in mutant cell lines lacking components of the interferon-stimulated gene factor complex (ISGF-3) revealed that IFN-β induction of Egr-1 was independent of Stat1, Stat2, or Irf9. Activation of the Mek/Erk-1/2 pathway was implicated in the rapid induction of Egr-1 by IFN-β in serum-starved mouse lung epithelial cells. Interrogation of multiple microarray datasets revealed that respiratory viruses including coronaviruses induced IFN-β and regulated Egr-1 expression in human lung cell lines. Furthermore, bioinformatic analysis revealed that type I interferon-stimulated genes and Egr-1 inducible genes including transcription factors, mediators of cell growth, and chemokines were differentially regulated in the human lung cell lines after coronavirus infection, and in the lung biopsies of COVID-19 patients.

Profiling transcription factor sub-networks in type I interferon signaling and in response to SARS-CoV-2 infection

Type I interferons (IFN α/β) play a central role in innate immunity to respiratory viruses, including coronaviruses. In this study, transcription factor profiling in the transcriptome was used to gain novel insights into the role of inducible transcription factors in response to type I interferon signaling in immune cells and in lung epithelial cells after SARS-CoV-2 infection. Modeling the interferon-inducible transcription factor mRNA data in terms of distinct sub-networks based on biological functions such as antiviral response, immune modulation, and cell growth revealed enrichment of specific transcription factors in mouse and human immune cells. Interrogation of multiple microarray datasets revealed that SARS-CoV-2 induced high levels of IFN-beta and interferon-inducible transcription factor mRNA in human lung epithelial cells. Transcription factor mRNA of the three sub-networks were differentially regulated in human lung epithelial cell lines after SARS-CoV-2 infection and in COVID-19 patients. A subset of type I interferon-inducible transcription factors and inflammatory mediators were specifically enriched in the lungs and neutrophils of Covid-19 patients. The emerging complex picture of type I IFN transcriptional regulation consists of a rapid transcriptional switch mediated by the Jak-Stat cascade and a graded output of the inducible transcription factor activation that enables temporal regulation of gene expression.

The Mechanism behind Influenza Virus Cytokine Storm

Influenza viruses are still a serious threat to human health. Cytokines are essential for cell-to-cell communication and viral clearance in the immune system, but excessive cytokines can cause serious immune pathology. Deaths caused by severe influenza are usually related to cytokine storms. The recent literature has described the mechanism behind the cytokine–storm network and how it can exacerbate host pathological damage. Biological factors such as sex, age, and obesity may cause biological differences between different individuals, which affects cytokine storms induced by the influenza virus. In this review, we summarize the mechanism behind influenza virus cytokine storms and the differences in cytokine storms of different ages and sexes, and in obesity.

STAT1 epigenetically regulates LCP2 and TNFAIP2 by recruiting EP300 to contribute to the pathogenesis of inflammatory bowel disease

Background

The aetiology of inflammatory bowel disease (IBD) is related to genetics and epigenetics. Epigenetic regulation of the pathogenesis of IBD has not been well defined. Here, we investigated the role of H3K27ac events in the pathogenesis of IBD. Based on previous ChIP-seq and RNA-seq assays, we studied signal transducer and activator of transcription 1 (STAT1) as a transcription factor (TF) and investigated whether the STAT1–EP300–H3K27ac axis contributes to the development of IBD. We performed ChIP-PCR to investigate the interaction between STAT1 and H3K27ac, and co-IP assays were performed to investigate the crosstalk between STAT1 and EP300.

Results

Lymphocyte cytosolic protein 2 (LCP2) and TNF-α‐inducible protein 2 (TNFAIP2) are target genes of STAT1. p-STAT1 binds to the enhancer loci of the two genes where H3K27ac is enriched, and EP300 subsequently binds to regulate their expression. In mice with dextran sulfate sodium (DSS)-induced acute colitis, an EP300 inhibitor significantly inhibited colitis.

Conclusions

p-STAT1 and EP300 promote TNFAIP2 and LCP2 expression through an increase in H3K27ac enrichment on their enhancers and contribute to the pathogenesis of chronic inflammation.

Graphic abstract

Effects of IFN-γ on immune cell kinetics during the resolution of acute lung injury

The immunologic responses that occur early in the acute respiratory distress syndrome (ARDS) elicit immune‐mediated damage. The mechanisms underlying the resolution of ARDS, particularly the role of signaling molecules in regulating immune cell kinetics, remain important questions. Th1‐mediated responses can contribute to the pathogenesis of acute lung injury (ALI). Interferon‐gamma (IFN‐γ) orchestrates early inflammatory events, enhancing immune‐mediated damage. The current study investigated IFN‐γ during resolution in several experimental models of ALI. The absence of IFN‐γ resulted in altered kinetics of lymphocyte and macrophage responses, suggesting that IFN‐γ present in this microenvironment is influential in ALI resolution. Genetic deficiency of IFN‐γ or administering neutralizing IFN‐γ antibodies accelerated the pace of resolution. Neutralizing IFN‐γ decreased the numbers of interstitial and inflammatory macrophages and increased alveolar macrophage numbers during resolution. Our results underline the complexity of lung injury resolution and provide insight into the effects through which altered IFN‐γ concentrations affect immune cell kinetics and the rate of resolution. These findings suggest that therapies that spatially or temporally control IFN‐γ signaling may promote ALI resolution. Identifying and elucidating the mechanisms critical to ALI resolution will allow the development of therapeutic approaches to minimize collateral tissue damage without adversely altering the response to injury.

Prevalence and outcomes of D dimer elevation among the COVID-19 patients in tertiary care hospital, Salem

Introduction:

Methodology:

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Conclusion:

Impact of Regulatory T Cells on Type 2 Alveolar Epithelial Cell Transcriptomes during Resolution of Acute Lung Injury and Contributions of IFN-γ

By enhancing tissue repair and modulating immune responses, Foxp3⁺ regulatory T cells (Tregs) play essential roles in resolution from lung injury. The current study investigated the effects that Tregs exert directly or indirectly on the transcriptional profiles of type 2 alveolar epithelial (AT2) cells during resolution in an experimental model of acute lung injury. Purified AT2 cells were isolated from uninjured mice or mice recovering from LPS-induced lung injury, either in the presence of Tregs or in Treg-depleted mice, and transcriptome profiling identified differentially expressed genes. Depletion of Tregs resulted in altered expression of 49 genes within AT2 cells during resolution, suggesting that Tregs present in this microenvironment influence AT2-cell function. Biological processes from Gene Ontology enriched in the absence of Tregs included those describing responses to IFN. Neutralizing IFN-γ in Treg-depleted mice reversed the effect of Treg depletion on inflammatory macrophages and B cells by preventing the increase in inflammatory macrophages and the decrease in B cells. Our results provide insight into the effects of Tregs on AT2 cells. Tregs directly or indirectly impact many AT2-cell functions, including IFN type I and II-mediated signaling pathways. Inhibition of IFN-γ expression and/or function may be one mechanism through which Tregs accelerate resolution after acute lung injury.

Immunopathogenesis of Coronavirus-Induced Acute Respiratory Distress Syndrome (ARDS): Potential Infection-Associated Hemophagocytic Lymphohistiocytosis

The outbreak of coronavirus disease 2019 (COVID-19) in December 2019 in Wuhan, China, introduced the third highly pathogenic coronavirus into humans in the 21st century. Scientific advance after the severe acute respiratory syndrome coronavirus (SARS-CoV) epidemic and Middle East respiratory syndrome coronavirus (MERS-CoV) emergence enabled clinicians to understand the epidemiology and pathophysiology of SARS-CoV-2. In this review, we summarize and discuss the epidemiology, clinical features, and virology of and host immune responses to SARS-CoV, MERS-CoV, and SARS-CoV-2 and the pathogenesis of coronavirus-induced acute respiratory distress syndrome (ARDS). We especially highlight that highly pathogenic coronaviruses might cause infection-associated hemophagocytic lymphohistiocytosis, which is involved in the immunopathogenesis of human coronavirus-induced ARDS, and also discuss the potential implication of hemophagocytic lymphohistiocytosis therapeutics for combating severe coronavirus infection.

Immunopathology of SARS-CoV-2 Infection: Immune Cells and Mediators, Prognostic Factors, and Immune-Therapeutic Implications

The present is a comprehensive review of the immunopathology of Covid-19. The immune reaction to SARS-CoV-2 infection is characterized by differentiation and proliferation of a variety of immune cells with immune mediator production and release, and activation of other pathogen resistance mechanisms. We fully address the humoral and cellular immune changes induced by the virus, with particular emphasis on the role of the “cytokine storm” in the evolution of the disease. Moreover, we also propose some immune alterations (i.e., inflammatory parameters, cytokines, leukocytes and lymphocyte subpopulations) as prognostic markers of the disease. Furthermore, we discuss how immune modifying drugs, such as tocilizumab, chloroquine, glucocorticoids and immunoglobulins, and blood purification therapy, can constitute a fundamental moment in the therapy of the infection. Finally, we made a critical analysis of a number of substances, not yet utilized, but potentially useful in SARS-CoV-2 patients, such as IFN lambda, TNF blockers, ulinastatin, siponimod, tacrolimus, mesenchymal stem cells, inhibitors of mononuclear macrophage recruitment, IL-1 family antagonists, JAK-2 or STAT-3 inhibitors.

D-Dimer and Prothrombin Time Are the Significant Indicators of Severe COVID-19 and Poor Prognosis

Objective

To investigate the value of coagulation indicators D-dimer (DD), prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), and fibrinogen (Fg) in predicting the severity and prognosis of COVID-19.

Methods

A total of 115 patients with confirmed COVID-19, who were admitted to Tianyou Hospital of Wuhan University of Science and Technology between January 18, 2020, and March 5, 2020, were included. The dynamic changes of DD, PT, APTT, and Fg were tested, and the correlation with CT imaging, clinical classifications, and prognosis was studied.

Results

Coagulation disorder occurred at the early stage of COVID-19 infection, with 50 (43.5%) patients having DD increased and 74 (64.3%) patients having Fg increased. The levels of DD and Fg were correlated with clinical classification. Among 23 patients who deceased, 18 had DD increased at the first lab test, 22 had DD increased at the second and third lab tests, and 18 had prolonged PT at the third test. The results from ROC analyses for mortality risk showed that the AUCs of DD were 0.742, 0.818, and 0.851 in three times of test, respectively; PT was 0.643, 0.824, and 0.937. In addition, with the progression of the disease, the change of CT imaging was closely related to the increase of the DD value (P < 0.01).

Conclusions

Coagulation dysfunction is more likely to occur in severe and critically ill patients. DD and PT could be used as the significant indicators in predicting the mortality of COVID-19.

Serum Amyloid A is a biomarker of severe Coronavirus Disease and poor prognosis

BACKGROUND

To explore the significance of SAA in evaluating the severity and prognosis of COVID-19.

METHODS

A total of 132 patients with confirmed COVID-19 who were admitted to a designated COVID-19 hospital in Wuhan, China from January 18, 2020 to February 26, 2020 were collected. The dynamic changes of blood SAA, CRP, PCT, WBC, Lymphocyte (L), PLT, CT imaging, and disease progression were studied. All patients completed at least twice laboratory data collection and clinical condition assessment at three time points indicated for this study; The length of hospital stay was longer than 14 days prior to February 26, 2020.

RESULTS

COVID-19 patients had significantly increased SAA and CRP levels, while L count decreased, and PCT, WBC, and PLT were in the normal range. As disease progressed from mild to critically severe, SAA and CRP gradually increased, while L decreased, and PLT, WBC, and PCT had no significant changes; ROC curve analysis suggests that SAA/L, CRP, SAA, and L count are valuable in evaluating the severity of COVID-19 and distinguishing critically ill patients from mild ones; Patients with SAA consistently trending down during the course of disease have better prognosis, compared with the patients with SAA continuously rising; The initial SAA level is positively correlated with the dynamic changes of the serial CT scans. Patient with higher initial SAA level are more likely to have poor CT imaging.

CONCLUSIONS

SAA and L are sensitive indicators in evaluating the severity and prognosis of COVID-19. Monitoring dynamic changes of SAA, combined with CT imaging could be valuable in diagnosis and treatment of COVID-19.

Platelet-to-lymphocyte ratio is associated with prognosis in patients with coronavirus disease-19

Since December 2019, novel coronavirus infected pneumonia emerged in Wuhan city and rapidly spread throughout China. In severe novel coronavirus pneumonia cases, the number of platelets, their dynamic changes during the treatment, platelet-to-lymphocyte ratio (PLR) were a concern. We sought to describe the platelet feature of these cases. Single-center case series of the 30 hospitalized patients with confirmed coronavirus disease (COVID)-19 in Huizhou municipal central hospital from January 2020 to February 2020 were retrospectively analyzed. Demographic, clinical, blood routine results, other laboratory results, and treatment data were collected and analyzed. Outcomes of severe patients and nonsevere patients were compared. Univariate analysis showed that: age, platelet peaks, and PLR at peak platelet were the influencing factors in severe patients, multivariate analysis showed that the PLR value at peak platelet during treatment was an independent influencing factor in severe patients. The average hospitalization day of patients with platelet peaks during treatment was longer than those without platelet peaks (P < .05). The average age of patients with platelet peaks during treatment was older than those without platelet peaks (P < .05). The patients with significantly elevated platelets during treatment had longer average hospitalization days. And the higher PLR of patients during treatment had longer average hospitalization days. Single-center case series of the 30 hospitalized patients with confirmed COVID-19 in Huizhou Municipal Central Hospital, presumed that the number of platelets and their dynamic changes during the treatment may have a suggestion on the severity and prognosis of the disease. The patient with markedly elevated platelets and longer average hospitalization days may be related to the cytokine storm. The PLR of patients means the degree of cytokine storm, which might provide a new indicator in the monitoring in patients with COVID-19.

The role of heparin/heparan sulphate in the IFN-γ-led Arena

IFN-γ (Interferon-gamma) is a pleiotropic cytokine. It is often involved in a variety of physiological processes by binding to the cell surface transmembrane receptor (IFN-γR) to initiate a series of signalling pathways that transmit external signals from cell surface receptors to the cell nucleus. Heparan sulphate (HS), a highly sulphated linear polysaccharide, is ubiquitous on the mammalian cell surface and extracellular matrix. Electrostatic interactions can be generated between the highly sulphated HS region and specific basic amino acid residues in the IFN-γ structure, thereby detaining IFN-γ on the cell surface, and the concentration of IFN-γ on the cell surface is thus, changed. IFN-γ retained on the cell surface will optimize the binding of IFN-γ to the transmembrane receptor resulting in high efficiency signalling. Heparin is a glycosaminoglycan with a structure similar to HS. The structural similarity provides a basis for modelling exogenous heparin dependence for interference with IFN-γ function. This model can be summarized as follows: First, the competitive binding effect; heparin bound to cytokines by competing with membrane-associated HS, causes a decrease in cytokine concentration on the cell surface. Second, the principle of priority occupancy; heparin can occupy the receptor binding site on cytokines, partially preventing the IFN-γ-IFN-γR interaction. These two models interfere with IFN-γ signal transmission. To decipher the mechanism by which heparin influences IFN-γ activity, studies of the structure-activity relationship are in progress. This paper summarizes research progress on the IFN-γ signalling pathway, heparin interference with IFN-γ activity and the structure-activity relationship between heparin and IFN-γ.

RNA Sequencing of H3N2 Influenza Virus-Infected Human Nasal Epithelial Cells from Multiple Subjects Reveals Molecular Pathways Associated with Tissue Injury and Complications

The human nasal epithelium is the primary site of exposure to influenza virus, the initiator of host responses to influenza and the resultant pathologies. Influenza virus may cause serious respiratory infection resulting in major complications, as well as severe impairment of the airways. Here, we elucidated the global transcriptomic changes during H3N2 infection of human nasal epithelial cells from multiple individuals. Using RNA sequencing, we characterized the differentially-expressed genes and pathways associated with changes occurring at the nasal epithelium following infection. We used in vitro differentiated human nasal epithelial cell culture model derived from seven different donors who had no concurrent history of viral infections. Statistical analysis highlighted strong transcriptomic signatures significantly associated with 24 and 48 h after infection, but not at the earlier 8-h time point. In particular, we found that the influenza infection induced in the nasal epithelium early and altered responses in interferon gamma signaling, B-cell signaling, apoptosis, necrosis, smooth muscle proliferation, and metabolic alterations. These molecular events initiated at the infected nasal epithelium may potentially adversely impact the airway, and thus the genes we identified could serve as potential diagnostic biomarkers or therapeutic targets for influenza infection and associated disease management.

SOCS4 expressed by recombinant HSV protects against cytokine storm in a mouse model

Oncolytic viruses are genetically engineered viruses designed for the treatment of solid tumors, and are often coupled with the antitumor immunity of the host. The challenge of using oncolytic herpes simplex virus (oHSV) as an efficacious oncolytic agent is the potential host tissue damage caused by the production of a range of cytokines following intratumoral oHSV injection. An HSV-suppressor of cytokine signaling 4 (SOCS4) recombinant virus was created to investigate whether it inhibits cytokine storm. Recombinant HSV-SOCS4 and HSV-1(F) were used to infect mice, and levels of several representative cytokines, including monocyte chemoattractant protein-1, interleukin (IL)-1β, tumor necrosis factor-α, IL-6 and interferon γ, in serum and bronchoalveolar lavage fluid (BALF) of infected mice were determined, and immune cells in BALF and spleen were enumerated. Lung damage, virus titers in the lung, body weight and survival rates of infected mice were also determined and compared between the two groups. The cytokine concentration of HSV-SOCS4-infected mice was significantly decreased compared with that of HSV-1(F)-infected mice in BALF and serum, and a smaller number of cluster of differentiation (CD)11b⁺ cells of BALF, and CD8⁺CD62L⁺ T cells and CD4⁺CD62L⁺ T cells of the spleen were also identified in HSV-SOCS4-infected mice. HSV-SOCS4-infected mice exhibited slight lung damage, a decrease in body weight loss and a 100% survival rate. The results of the present study indicated that SOCS4 protein may be a useful regulator to inhibit cytokine overproduction, and that HSV-SOCS4 may provide a possible solution to control cytokine storm and its consequences following induction by oncolytic virus treatment.

Expanding laparoscopic pancreaticoduodenectomy to pancreatic-head and periampullary malignancy: major findings based on systematic review and meta-analysis

BACKGROUND

Laparoscopic pancreaticoduodenectomy (LPD) remains to be established as a safe and effective alternative to open pancreaticoduodenectomy (OPD) for pancreatic-head and periampullary malignancy. The purpose of this meta-analysis was to compare LPD with OPD for these malignancies regarding short-term surgical and long-term survival outcomes.

METHODS

A literature search was conducted before March 2018 to identify comparative studies in regard to outcomes of both LPD and OPD for the treatment of pancreatic-head and periampullary malignancies. Morbidity, postoperative pancreatic fistula (POPF), mortality, operative time, estimated blood loss, hospitalization, retrieved lymph nodes, and survival outcomes were compared.

RESULTS

Among eleven identified studies, 1196 underwent LPD, and 8247 were operated through OPD. The pooled data showed that LPD was associated with less morbidity (OR = 0.57, 95%CI: 0.41~ 0.78, P < 0.01), less blood loss (WMD = - 372.96 ml, 95% CI, - 507.83~ - 238.09 ml, P < 0.01), shorter hospital stays (WMD = - 197.49 ml, 95% CI, - 304.62~ - 90.37 ml, P < 0.01), and comparable POPF (OR = 0.85, 95%CI: 0.59~ 1.24, P = 0.40), and overall survival (HR = 1.03, 95%CI: 0.93~ 1.14, P = 0.54) compared to OPD. Operative time was longer in LPD (WMD = 87.68 min; 95%CI: 27.05~ 148.32, P < 0.01), whereas R0 rate tended to be higher in LPD (OR = 1.17; 95%CI: 1.00~ 1.37, P = 0.05) and there tended to be more retrieved lymph nodes in LPD (WMD = 1.15, 95%CI: -0.16~ 2.47, P = 0.08), but these differences failed to reach statistical significance.

CONCLUSIONS

LPD can be performed as safe and effective as OPD for pancreatic-head and periampullary malignancy with respect to both surgical and oncological outcomes. LPD is associated with less intraoperative blood loss and postoperative morbidity and may serve as a promising alternative to OPD in selected individuals in the future.

Dysregulation of the IFN-γ-STAT1 signaling pathway in a cell line model of large granular lymphocyte leukemia

T cell large granular lymphocyte leukemia (T-LGLL) is a rare incurable disease that is characterized by defective apoptosis of cytotoxic CD8+ T cells. Chronic activation of the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) pathway is a hallmark of T-LGLL. One manifestation is the constitutive phosphorylation of tyrosine 701 of STAT1 (p-STAT1). T-LGLL patients also exhibit elevated serum levels of the STAT1 activator, interferon-γ (IFN-γ), thus contributing to an inflammatory environment. In normal cells, IFN-γ production is tightly controlled through induction of IFN-γ negative regulators. However, in T-LGLL, IFN-γ signaling lacks this negative feedback mechanism as evidenced by excessive IFN-γ production and decreased levels of suppressors of cytokine signaling 1 (SOCS1), a negative regulator of IFN-γ. Here we characterize the IFN-γ-STAT1 pathway in TL-1 cells, a cell line model of T-LGLL. TL-1 cells exhibited lower IFN-γ receptor protein and mRNA expression compared to an IFN-γ responsive cell line. Furthermore, IFN-γ treatment did not induce JAK2 or STAT1 activation or transcription of IFN-γ-inducible gene targets. However, IFN-β induced p-STAT1 and subsequent STAT1 gene transcription, demonstrating a specific IFN-γ signaling defect in TL-1 cells. We utilized siRNA targeting of STAT1, STAT3, and STAT5b to probe their role in IL-2-mediated IFN-γ regulation. These studies identified STAT5b as a positive regulator of IFN-γ production. We also characterized the relationship between STAT1, STAT3, and STAT5b proteins. Surprisingly, p-STAT1 was positively correlated with STAT3 levels while STAT5b suppressed the activation of both STAT1 and STAT3. Taken together, these results suggest that the dysregulation of the IFN-γ-STAT1 signaling pathway in TL-1 cells likely results from low levels of the IFN-γ receptor. The resulting inability to induce negative feedback regulators explains the observed elevated IL-2 driven IFN-γ production. Future work will elucidate the best way to target this pathway, with the ultimate goal to find a better therapeutic for T-LGLL.

Minimally invasive pancreaticoduodenectomy for periampullary disease: a comprehensive review of literature and meta-analysis of outcomes compared with open surgery

BACKGROUND

Minimally invasive pancreatoduodenectomy (MIPD) has been gradually attempted. However, whether MIPD is superior, equal or inferior to its conventional open pancreatoduodenectomy (OPD) is not clear.

METHODS

Studies published up to May 2017 were searched in PubMed, Embase, Cochrane Library, and Web of Science. Main outcomes were comprehensively reviewed and measured including conversion to open approach, operation time (OP), estimated blood loss (EBL), transfusion, length of hospital stay (LOS), overall complications, postoperative pancreatic fistula (POPF), delayed gastric emptying (DGE), post-pancreatectomy hemorrhage (PPH), readmission, reoperation and reasons of preoperative death, number of retrieved lymph nodes (RLN), surgical margins, recurrence, and survival. The software of Review Manage version 5.1 was used for meta-analysis.

RESULTS

One hundred studies were included for systematic review and 26 out of them (totally 3402 cases, 1064 for MIPD, 2338 for OPD) were included for meta-analysis. In the early years, most articles were case reports or non-control case series studies, while in the last 6 years high-volume and comparative researches were increasing gradually. Systematic review revealed conversion rates of MIPD to OPD ranged from 0% to 40%. The mean or median OP of MIPD ranged from 276 to 657 min. The total POPF rates vary between 3.8% and 50% observed in all systematic reviewed studies. Meta-analysis demonstrated MIPD had longer OP (WMD = 99.4 min; 95%CI: 46.0 ~ 152.8, P < 0.01), lower blood loss (WMD = -0.54 ml; 95% CI, -0.88 ~ -0.20 ml; P < 0.01), lower transfusion rate (RR = 0.73, 95%CI: 0.57 ~ 0.94, P = 0.02), shorter LOS (WMD = -3.49 days; 95%CI: -4.83 ~ -2.15, P < 0.01). There was no significant difference in time to oral intake, postoperative complications, POPF, reoperation, readmission, perioperative mortality and number of retrieved lymph nodes.

CONCLUSION

Our study demonstrates MIPD is technically feasible and safety on the basis of historical studies. MIPD is associated with less blood loss, faster postoperative recovery, shorter length of hospitalization and longer operation time. These findings are waiting for being confirmed with robust prospective comparative studies and randomized clinical trials.

Recent advances in our understanding of the mechanisms of late lung development and bronchopulmonary dysplasia

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.

Inhibition of CD8+ T cells and elimination of myeloid cells by CD4+ Foxp3- T regulatory type 1 cells in acute respiratory distress syndrome

Acute lung injury and acute respiratory distress syndrome (ARDS) are caused by rapid-onset bilateral pulmonary inflammation. We therefore investigated the potential role of interleukin (IL)-10⁺ CD4⁺ Tr1 cells, a regulatory T cell subset with previously identified immunosuppressive functions, in ARDS patients. We first showed that circulating Tr1 cells were upregulated in active and resolved ARDS patients compared to healthy controls and pneumonia patient controls. A significant fraction of these Tr1 cells expressed granzyme B and perforin, while most Tr1 cells did not express interferon gamma (IFN-γ), IL-4, IL-17 or FOXP3, suggesting that the effector functions of these Tr1 cells were primarily mediated by IL-10, granzyme B, and perforin. Indeed, Tr1 cells effectively suppressed CD8⁺ T cell IFN-γ production and induced lysis of monocytes and dendritic cells in vitro. The elimination of myeloid antigen-presenting cells depended on granzyme B production. We also discovered that Tr1 cells could be identified in the bronchoalveolar lavage fluid collected from ARDS patients. All these results suggested that Tr1 cells possessed the capacity to downregulate inflammation in ARDS. In support of this, we found that ARDS patients who resolved the inflammation and survived the syndrome contained significantly higher levels of Tr1 cells than ARDS patients who succumbed to the syndrome. Overall, this report added a novel piece of evidence that ARDS could be intervened by regulatory T cell-mediated suppressive mechanisms.

New fronts emerge in the influenza cytokine storm

Influenza virus is a significant pathogen in humans and animals with the ability to cause extensive morbidity and mortality. Exuberant immune responses induced following infection have been described as a "cytokine storm," associated with excessive levels of proinflammatory cytokines and widespread tissue damage. Recent studies have painted a more complex picture of cytokine networks and their contributions to clinical outcomes. While many cytokines clearly inflict immunopathology, others have non-pathological delimited roles in sending alarm signals, facilitating viral clearance, and promoting tissue repair, such as the IL-33-amphiregulin axis, which plays a key role in resolving some types of lung damage. Recent literature suggests that type 2 cytokines, traditionally thought of as not involved in anti-influenza immunity, may play an important regulatory role. Here, we discuss the diverse roles played by cytokines after influenza infection and highlight new, serene features of the cytokine storm, while highlighting the specific functions of relevant cytokines that perform unique immune functions and may have applications for influenza therapy.

Airway CD8(+) T Cells Are Associated with Lung Injury during Infant Viral Respiratory Tract Infection

Infants and young children are disproportionately susceptible to severe complications from respiratory viruses, although the underlying mechanisms remain unknown. Recent studies show that the T cell response in the lung is important for protective responses to respiratory infections, although details on the infant/pediatric respiratory immune response remain sparse. The objectives of the present study were to characterize the local versus systemic immune response in infants and young children with respiratory failure from viral respiratory tract infections and its association to disease severity. Daily airway secretions were sampled from infants and children 4 years of age and younger receiving mechanical ventilation owing to respiratory failure from viral infection or noninfectious causes. Samples were examined for immune cell composition and markers of T cell activation. These parameters were then correlated with clinical disease severity. Innate immune cells and total CD3(+) T cells were present in similar proportions in airway aspirates derived from infected and uninfected groups; however, the CD8:CD4 T cell ratio was markedly increased in the airways of patients with viral infection compared with uninfected patients, and specifically in infected infants with acute lung injury. T cells in the airways were phenotypically and functionally distinct from those in blood with activated/memory phenotypes and increased cytotoxic capacity. We identified a significant increase in airway cytotoxic CD8(+) T cells in infants with lung injury from viral respiratory tract infection that was distinct from the T cell profile in circulation and associated with increasing disease severity. Airway sampling could therefore be diagnostically informative for assessing immune responses and lung damage.

Anti-inflammatory Effects of Herbal Preparations STW5 and STW5-II in Cytokine-Challenged Normal Human Colon Cells

Inflammatory bowel diseases (IBD) are chronic relapsing intestinal disorders characterized by up-regulation of pro-inflammatory cytokines followed by invasion of immune cells to the intestinal lamina propria. Standard therapies consist of anti-inflammatory or immunosuppressive drugs. Since clinical efficiency is not satisfactory and the established drugs have massive side effects, new strategies to treat IBD are required. Herein, we investigate the protective effect of the fixed combination herbal preparations STW5 and STW5-II and the contribution of the corresponding single components in an in vitro inflammation model. The normal human colon epithelial cell line, NCM460, was treated with STW5, STW5-II or their single components for 4 h followed by experimental conditions comparable to induction of colitis. A pro-inflammatory cytokine cocktail consisting of TNF-α, IL-β, and IFN-γ was used to simulate inflammatory stimuli normally caused by immune cells. The effects on NCM460 cells were investigated by enzyme-linked immunoassay and Proteome Profiler^®. Levels of IP-10, MCP-1, I-TAC, Groα, and IL-8 were elevated in chemokine-treated cells compared to untreated cells, but significantly reduced upon pretreatment with STW5 or STW5-II. However, the single compounds revealed only little effects on protein expression. Furthermore, we investigated the effect of both combination preparations on pro-inflammatory transcription factors of the STAT family using Western blot. In addition, we tested the effects on upstream MAPK p38. Both, STW5 and STW5-II did not show any effect on MAPK p38, but were effective in reducing phosphorylated levels of STAT1. In conclusion, both combination preparations act in an anti-inflammatory manner by influencing cytokine secretion via reduced activity of the JAK/STAT1 pathway. Relevant differences between STW5 and STW5-II were not found indicating similar efficacies.

The inflammatory response triggered by Influenza virus: a two edged sword

Influenza A virus (IAV) is a relevant respiratory tract pathogen leading to a great number of deaths and hospitalizations worldwide. Secondary bacterial infections are a very common cause of IAV associated morbidity and mortality. The robust inflammatory response that follows infection is important for the control of virus proliferation but is also associated with lung damage, morbidity and death. The role of the different components of immune response underlying protection or disease during IAV infection is not completely elucidated. Overall, in the context of IAV infection, inflammation is a 'double edge sword' necessary to control infection but causing disease. Therefore, a growing number of studies suggest that immunomodulatory strategies may improve disease outcome without affecting the ability of the host to deal with infection. This review summarizes recent aspects of the inflammatory responses triggered by IAV that are preferentially involved in causing severe pulmonary disease and the anti-inflammatory strategies that have been suggested to treat influenza induced immunopathology.

Balancing Immune Protection and Immune Pathology by CD8(+) T-Cell Responses to Influenza Infection

Influenza A virus (IAV) is a significant human pathogen causing annual epidemics and periodic pandemics. CD8⁺ cytotoxic T lymphocyte (CTL)-mediated immunity contributes to the clearance of virus-infected cells, and CTL immunity targeting the conserved internal proteins of IAVs is a key protection mechanism when neutralizing antibodies are absent during heterosubtypic IAV infection. However, CTL infiltration into the airways, its cytotoxicity, and the effects of produced proinflammatory cytokines can cause severe lung tissue injury, thereby contributing to immunopathology. Studies have discovered complicated and exquisite stimulatory and inhibitory mechanisms that regulate CTL magnitude and effector activities during IAV infection. Here, we review the state of knowledge on the roles of IAV-specific CTLs in immune protection and immunopathology during IAV infection in animal models, highlighting the key findings of various requirements and constraints regulating the balance of immune protection and pathology involved in CTL immunity. We also discuss the evidence of cross-reactive CTL immunity as a positive correlate of cross-subtype protection during secondary IAV infection in both animal and human studies. We argue that the effects of CTL immunity on protection and immunopathology depend on multiple layers of host and viral factors, including complex host mechanisms to regulate CTL magnitude and effector activity, the pathogenic nature of the IAV, the innate response milieu, and the host historical immune context of influenza infection. Future efforts are needed to further understand these key host and viral factors, especially to differentiate those that constrain optimally effective CTL antiviral immunity from those necessary to restrain CTL-mediated non-specific immunopathology in the various contexts of IAV infection, in order to develop better vaccination and therapeutic strategies for modifying protective CTL immunity.

Influenza lung injury: mechanisms and therapeutic opportunities

In this Perspectives, we discuss some recent developments in the pathogenesis of acute lung injury following influenza infection, with an emphasis on promising therapeutic leads. Damage to the alveolar-capillary barrier has been quantified in mice, and agents have been identified that can help to preserve barrier integrity, such as vasculotide, angiopoietin-like 4 neutralization, and sphingosine 1-phosphate mimics. Results from studies using mesenchymal stem cells have been disappointing, despite promising data in other types of lung injury. The roles of fatty acid binding protein 5, prostaglandin E2, and the interplay between IFN-γ and STAT1 in epithelial signaling during infection have been addressed in vitro. Finally, we discuss the role of autophagy in inflammatory cytokine production and the viral life cycle and the opportunities this presents for intervention.