Viral and bacterial co-infection in severe pneumonia triggers innate immune responses and specifically enhances IP-10: a translational study

The Relationship Between Differential Expression of Non-coding RNAs (TP53TG1, LINC00342, MALAT1, DNM3OS, miR-126-3p, miR-200a-3p, miR-18a-5p) and Protein-Coding Genes (PTEN, FOXO3) and Risk of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a rapidly progressive interstitial lung disease of unknown pathogenesis with no effective treatment currently available. Given the regulatory roles of lncRNAs (TP53TG1, LINC00342, H19, MALAT1, DNM3OS, MEG3), miRNAs (miR-218-5p, miR-126-3p, miR-200a-3p, miR-18a-5p, miR-29a-3p), and their target protein-coding genes (PTEN, TGFB2, FOXO3, KEAP1) in the TGF-β/SMAD3, Wnt/β-catenin, focal adhesion, and PI3K/AKT signaling pathways, we investigated the expression levels of selected genes in peripheral blood mononuclear cells (PBMCs) and lung tissue from patients with IPF. Lung tissue and blood samples were collected from 33 newly diagnosed, treatment-naive patients and 70 healthy controls. Gene expression levels were analyzed by RT-qPCR. TaqMan assays and TaqMan MicroRNA assay were employed to quantify the expression of target lncRNAs, mRNAs, and miRNAs. Our study identified significant differential expression in PBMCs from IPF patients compared to healthy controls, including lncRNAs MALAT1 (Fold Change = 3.809, P = 0.0001), TP53TG1 (Fold Change = 0.4261, P = 0.0021), and LINC00342 (Fold Change = 1.837, P = 0.0448); miRNAs miR-126-3p (Fold Change = 0.102, P = 0.0028), miR-200a-3p (Fold Change = 0.442, P = 0.0055), and miR-18a-5p (Fold Change = 0.154, P = 0.0034); and mRNAs FOXO3 (Fold Change = 4.604, P = 0.0032) and PTEN (Fold Change = 2.22, P = 0.0011). In lung tissue from IPF patients, significant expression changes were observed in TP53TG1 (Fold Change = 0.2091, P = 0.0305) and DNM3OS (Fold Change = 4.759, P = 0.05). Combined analysis of PBMCs expression levels for TP53TG1, MALAT1, miRNA miR-126-3p, and PTEN distinguished IPF patients from healthy controls with an AUC = 0.971, sensitivity = 0.80, and specificity = 0.955 (P = 6 × 10-8). These findings suggest a potential involvement of the identified ncRNAs and mRNAs in IPF pathogenesis. However, additional functional validation studies are needed to elucidate the precise molecular mechanisms by which these lncRNAs, miRNAs, and their targets contribute to PF.

Aetiological agents of pneumonia among HIV and non-HIV infected children in Ghana: A case-control study

Pneumonia is the leading cause of death in children, however, the microbial aetiology of pneumonia is not well elucidated in low- and middle-income countries. Our study was aimed at determining the microbial aetiologies of childhood pneumonia and associated risk factors in HIV and non-HIV infected children. We conducted a case-control study that enrolled children with pneumonia as cases and non-pneumonia as controls from July 2017 to May 2020. Induced sputum and blood samples were investigated for microbial organisms using standard microbiological techniques. DNA/RNA was extracted from sputum samples and tested for viral and bacterial agents. Four hundred and four (404) subjects consisting of 231 (57.2%) cases and 173 (42.8%) controls were enrolled. We identified a significant (p = 0.011) proportion of viruses in cases (125; 54.1%, 95%CI: 47.4-60.7) than controls (71; 33.6%, 95%CI: 33.6-48.8) and these were mostly contributed to by Respiratory Syncytial Virus. Staphylococcus aureus (16; 4.0%), Klebsiella spp. (15, 3.7%) and Streptococcus pneumoniae (8, 2.0%) were the main bacterial agents identified in sputum or induced sputum samples. HIV infected children with viral-bacterial co-detection were found to have very severe pneumonia compared to those with only viral or bacterial infection. Indoor cooking (OR = 2.36; 95%CI:1.41-3.96) was found to be associated with pneumonia risk in patients. This study demonstrates the importance of various microbial pathogens, particularly RSV, in contributing to pneumonia in HIV and non-HIV paediatric populations. There is a need to accelerate clinical trials of RSV vaccines in African populations to support improvement of patient care.

SOCSs: important regulators of host cell susceptibility or resistance to viral infection

Suppressors of cytokine signaling (SOCSs) are implicated in viral infection and host antiviral innate immune response. Recent studies demonstrate that viruses can hijack SOCSs to inhibit Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway, block the production and signaling of interferons (IFNs). At the same time, viruses can hijack SOCS to regulate non-IFN factors to evade antiviral response. Host cells can also regulate SOCSs to resist viral infection. The competition of the control of SOCSs may largely determine the fate of viral infection and the susceptibility or resistance of host cells, which is of significance for development of novel antiviral therapies targeting SOCSs. Accumulating evidence reveal that the regulation and function of SOCSs by viruses and host cells are very complicated, which is determined by characteristics of both viruses and host cell types. This report presents a systematic review to evaluate the roles of SOCSs in viral infection and host antiviral responses. One of messages worth attention is that all eight SOCS members should be investigated to accurately characterize their roles and relative contribution in each viral infection, which may help identify the most effective SOCS to be used in "individualized" antiviral therapy.

Role of the MicroRNAs in the Pathogenic Mechanism of Painful Symptoms in Long COVID: Systematic Review

The ongoing pandemic of COVID-19 has caused more than 6.7 million tragic deaths, plus, a large percentage of people who survived it present a myriad of chronic symptoms that last for at least 6 months; this has been named as long COVID. Some of the most prevalent are painful symptoms like headache, joint pain, migraine, neuropathic-like pain, fatigue and myalgia. MicroRNAs are small non-coding RNAs that regulate genes, and their involvement in several pathologies has been extensively shown. A deregulation of miRNAs has been observed in patients with COVID-19. The objective of the present systematic review was to show the prevalence of chronic pain-like symptoms of patients with long COVID and based on the expression of miRNAs in patients with COVID-19, and to present a proposal on how they may be involved in the pathogenic mechanisms of chronic pain-like symptoms. A systematic review was carried out in online databases for original articles published between March 2020 to April 2022; the systematic review followed the PRISMA guidelines, and it was registered in PROSPERO with registration number CRD42022318992. A total of 22 articles were included for the evaluation of miRNAs and 20 regarding long COVID; the overall prevalence of pain-like symptoms was around 10 to 87%, plus, the miRNAs that were commonly up and downregulated were miR-21-5p, miR-29a,b,c-3p miR-92a,b-3p, miR-92b-5p, miR-126-3p, miR-150-5p, miR-155-5p, miR-200a, c-3p, miR-320a,b,c,d,e-3p, and miR-451a. The molecular pathways that we hypothesized to be modulated by these miRNAs are the IL-6/STAT3 proinflammatory axis and the compromise of the blood-nerve barrier; these two mechanisms could be associated with the prevalence of fatigue and chronic pain in the long COVID population, plus they could be novel pharmacological targets in order to reduce and prevent these symptoms.

Microbial and Immune Regulation of the Gut-Lung Axis during Viral-Bacterial Coinfection

Viral-bacterial coinfections of the respiratory tract have long been associated with worsened disease outcomes. Clinical and basic research studies demonstrate that these infections are driven via complex interactions between the infecting pathogens, microbiome, and host immune response, although how these interactions contribute to disease progression is still not fully understood. Research over the last decade shows that the gut has a significant role in mediating respiratory outcomes, in a phenomenon known as the "gut-lung axis." Emerging literature demonstrates that acute respiratory viruses can modulate the gut-lung axis, suggesting that dysregulation of gut-lung cross talk may be a contributing factor during respiratory coinfection. This review will summarize the current literature regarding modulation of the gut-lung axis during acute respiratory infection, with a focus on the role of the microbiome, secondary infections, and the host immune response.

Interactions Between Severe Acute Respiratory Syndrome Coronavirus 2 Replication and Major Respiratory Viruses in Human Nasal Epithelium

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with extensive nonpharmacological interventions, have profoundly altered the epidemiology of major respiratory viruses. Some studies have described virus-virus interactions, particularly manifested by viral interference mechanisms at different scales. However, our knowledge of the interactions between SARS-CoV-2 and other respiratory viruses remains incomplete. Here, we studied the interactions between SARS-CoV-2 and several respiratory viruses (influenza, respiratory syncytial virus, human metapneumovirus, and human rhinovirus) in a reconstituted human epithelial airway model, exploring different scenarios affecting the sequence and timing of coinfections. We show that the virus type and sequence of infections are key factors in virus-virus interactions, the primary infection having a determinant role in the immune response to the secondary infection.

The current landscape of microRNAs (miRNAs) in bacterial pneumonia: opportunities and challenges

MicroRNAs (miRNAs), which were initially discovered in Caenorhabditis elegans, can regulate gene expression by recognizing cognate sequences and interfering with the transcriptional or translational machinery. The application of bioinformatics tools for structural analysis and target prediction has largely driven the investigation of certain miRNAs. Notably, it has been found that certain miRNAs which are widely involved in the inflammatory response and immune regulation are closely associated with the occurrence, development, and outcome of bacterial pneumonia. It has been shown that certain miRNA techniques can be used to identify related targets and explore associated signal transduction pathways. This enhances the understanding of bacterial pneumonia, notably for "refractory" or drug-resistant bacterial pneumonia. Although these miRNA-based methods may provide a basis for the clinical diagnosis and treatment of this disease, they still face various challenges, such as low sensitivity, poor specificity, low silencing efficiency, off-target effects, and toxic reactions. The opportunities and challenges of these methods have been completely reviewed, notably in bacterial pneumonia. With the continuous improvement of the current technology, the miRNA-based methods may surmount the aforementioned limitations, providing promising support for the clinical diagnosis and treatment of "refractory" or drug-resistant bacterial pneumonia.

Time-Dependent Increase in Susceptibility and Severity of Secondary Bacterial Infections During SARS-CoV-2

Secondary bacterial infections can exacerbate SARS-CoV-2 infection, but their prevalence and impact remain poorly understood. Here, we established that a mild to moderate infection with the SARS-CoV-2 USA-WA1/2020 strain increased the risk of pneumococcal (type 2 strain D39) coinfection in a time-dependent, but sex-independent, manner in the transgenic K18-hACE2 mouse model of COVID-19. Bacterial coinfection increased lethality when the bacteria was initiated at 5 or 7 d post-virus infection (pvi) but not at 3 d pvi. Bacterial outgrowth was accompanied by neutrophilia in the groups coinfected at 7 d pvi and reductions in B cells, T cells, IL-6, IL-15, IL-18, and LIF were present in groups coinfected at 5 d pvi. However, viral burden, lung pathology, cytokines, chemokines, and immune cell activation were largely unchanged after bacterial coinfection. Examining surviving animals more than a week after infection resolution suggested that immune cell activation remained high and was exacerbated in the lungs of coinfected animals compared with SARS-CoV-2 infection alone. These data suggest that SARS-CoV-2 increases susceptibility and pathogenicity to bacterial coinfection, and further studies are needed to understand and combat disease associated with bacterial pneumonia in COVID-19 patients.

Nucleolin: a cell portal for viruses, bacteria, and toxins

The main localization of nucleolin is the nucleolus, but this protein is present in multiple subcellular sites, and it is unconventionally secreted. On the cell surface, nucleolin acts as a receptor for various viruses, some bacteria, and some toxins. Aim of this review is to discuss the characteristics that make nucleolin able to act as receptor or co-receptor of so many and different pathogens. The important features that emerge are its multivalence, and its role as a bridge between the cell surface and the nucleus. Multiple domains, short linear motifs and post-translational modifications confer and modulate nucleolin ability to interact with nucleic acids, with proteins, but also with carbohydrates and lipids. This modular multivalence allows nucleolin to participate in different types of biomolecular condensates and to move to various subcellular locations, where it can act as a kind of molecular glue. It moves from the nucleus to the cell surface and can accompany particles in the reverse direction, from the cell surface into the nucleus, which is the destination of several pathogens to manipulate the cell in their favour.

Time-Dependent Increase in Susceptibility and Severity of Secondary Bacterial Infection during SARS-CoV-2 Infection

Secondary bacterial infections can exacerbate SARS-CoV-2 infection, but their prevalence and impact remain poorly understood. Here, we established that a mild to moderate SARS-CoV-2 infection increased the risk of pneumococcal coinfection in a time-dependent, but sexindependent, manner in the transgenic K18-hACE mouse model of COVID-19. Bacterial coinfection was not established at 3 d post-virus, but increased lethality was observed when the bacteria was initiated at 5 or 7 d post-virus infection (pvi). Bacterial outgrowth was accompanied by neutrophilia in the groups coinfected at 7 d pvi and reductions in B cells, T cells, IL-6, IL-15, IL-18, and LIF were present in groups coinfected at 5 d pvi. However, viral burden, lung pathology, cytokines, chemokines, and immune cell activation were largely unchanged after bacterial coinfection. Examining surviving animals more than a week after infection resolution suggested that immune cell activation remained high and was exacerbated in the lungs of coinfected animals compared with SARS-CoV-2 infection alone. These data suggest that SARS-CoV-2 increases susceptibility and pathogenicity to bacterial coinfection, and further studies are needed to understand and combat disease associated with bacterial pneumonia in COVID-19 patients.

Immune signature of acute pharyngitis in a Streptococcus pyogenes human challenge trial

Streptococcus pyogenes causes at least 750 million infections and more than 500,000 deaths each year. No vaccine is currently available for S. pyogenes and the use of human challenge models offer unique and exciting opportunities to interrogate the immune response to infectious diseases. Here, we use high-dimensional flow cytometric analysis and multiplex cytokine and chemokine assays to study serial blood and saliva samples collected during the early immune response in human participants following challenge with S. pyogenes. We find an immune signature of experimental human pharyngitis characterised by: 1) elevation of serum IL-1Ra, IL-6, IFN-γ, IP-10 and IL-18; 2) increases in peripheral blood innate dendritic cell and monocyte populations; 3) reduced circulation of B cells and CD4+ T cell subsets (Th1, Th17, Treg, TFH) during the acute phase; and 4) activation of unconventional T cell subsets, γδTCR + Vδ2+ T cells and MAIT cells. These findings demonstrate that S. pyogenes infection generates a robust early immune response, which may be important for host protection. Together, these data will help advance research to establish correlates of immune protection and focus the evaluation of vaccines.

Building HMM and molecular docking analysis for the sensitive detection of anti-viral pneumonia antimicrobial peptides (AMPs)

Pneumonia is the main reason for mortality among children under five years, causing 1.6 million deaths every year; late research has exhibited that mortality is increasing in the elderly. A few biomarkers used for its diagnosis need specificity and precision, as they are related to different infections, for example, pulmonary tuberculosis and Human Immunodeficiency Virus. There is a quest for new biomarkers worldwide to diagnose the disease to defeat these previously mentioned constraints. Antimicrobial peptides (AMPs) are promising indicative specialists against infection. This research work used AMPs as biomarkers to detect viral pneumonia pathogens, for example, Respiratory syncytial virus, Influenza A and B viruses utilizing in silico technologies, such as Hidden Markov Model (HMMER). HMMER was used to distinguish putative anti-viral pneumonia AMPs against the recognized receptor proteins of Respiratory syncytial virus, Influenza A, and B viruses. The physicochemical parameters of these putative AMPs were analyzed, and their 3-D structures were determined utilizing I-TASSER. Molecular docking interaction of these AMPs against the recognized viral pneumonia proteins was carried out using the PATCHDOCK and HDock servers. The results demonstrated 27 anti-viral AMPs ranked based on their E values with significant physicochemical parameters in similarity with known experimentally approved AMPs. The AMPs additionally had a high anticipated binding potential to the pneumonia receptors of these microorganisms sensitively. The tendency of the putative anti-viral AMPs to bind pneumonia proteins showed that they would be promising applicant biomarkers to identify these viral microorganisms in the point-of-care (POC) pneumonia diagnostics. The high precision observed for the AMPs legitimizes HMM's utilization in the disease diagnostics' discovery process.

Viral and Bacterial Co-Infections in the Lungs: Dangerous Liaisons

Respiratory tract infections constitute a significant public health problem, with a therapeutic arsenal that remains relatively limited and that is threatened by the emergence of antiviral and/or antibiotic resistance. Viral–bacterial co-infections are very often associated with the severity of these respiratory infections and have been explored mainly in the context of bacterial superinfections following primary influenza infection. This review summarizes our current knowledge of the mechanisms underlying these co-infections between respiratory viruses (influenza viruses, RSV, and SARS-CoV-2) and bacteria, at both the physiological and immunological levels. This review also explores the importance of the microbiome and the pathological context in the evolution of these respiratory tract co-infections and presents the different in vitro and in vivo experimental models available. A better understanding of the complex functional interactions between viruses/bacteria and host cells will allow the development of new, specific, and more effective diagnostic and therapeutic approaches.

Aetiology of acute respiratory infection in preschool children requiring hospitalisation in Europe-results from the PED-MERMAIDS multicentre case-control study

Background

Both pathogenic bacteria and viruses are frequently detected in the nasopharynx (NP) of children in the absence of acute respiratory infection (ARI) symptoms. The aim of this study was to estimate the aetiological fractions for ARI hospitalisation in children for respiratory syncytial virus (RSV) and influenza virus and to determine whether detection of specific respiratory pathogens on NP samples was associated with ARI hospitalisation.

Methods

349 children up to 5 years of age hospitalised for ARI (following a symptom-based case definition) and 306 hospital controls were prospectively enrolled in 16 centres across seven European Union countries between 2016 and 2019. Admission day NP swabs were analysed by multiplex PCR for 25 targets.

Results

RSV was the leading single cause of ARI hospitalisations, with an overall population attributable fraction (PAF) of 33.4% and high seasonality as well as preponderance in younger children. Detection of RSV on NP swabs was strongly associated with ARI hospitalisation (OR adjusted for age and season: 20.6, 95% CI: 9.4 to 45.3). Detection of three other viral pathogens showed strong associations with ARI hospitalisation: influenza viruses had an adjusted OR of 6.1 (95% CI: 2.5 to 14.9), parainfluenza viruses (PIVs) an adjusted OR of 4.6 (95% CI: 1.8 to 11.3) and metapneumoviruses an adjusted OR of 4.5 (95% CI: 1.3 to 16.1). Influenza viruses had a PAF of 7.9%, PIVs of 6.5% and metapneumoviruses of 3.0%. In contrast, most other pathogens were found in similar proportions in cases and controls, including Streptococcus pneumoniae, which was weakly associated with case status, and endemic coronaviruses.

Conclusion

RSV is the predominant cause of ARI hospitalisations in young children in Europe and its detection, as well as detection of influenza virus, PIV or metapneumovirus, on NP swabs can establish aetiology with high probability. PAFs for RSV and influenza virus are highly seasonal and age dependent.

Outcomes of respiratory viral-bacterial co-infection in adult hospitalized patients

BACKGROUND

Viral infections of the respiratory tract represent a major global health concern. Co-infection with bacteria may contribute to severe disease and increased mortality in patients. Nevertheless, viral-bacterial co-infection patterns and their clinical outcomes have not been well characterized to date. This study aimed to evaluate the clinical features and outcomes of patients with viral-bacterial respiratory tract co-infections.

METHODS

We included 19,361 patients with respiratory infection due to respiratory viruses [influenza A and B, respiratory syncytial virus (RSV), parainfluenza] and/or bacteria in four tertiary hospitals in Hong Kong from 2013 to 2017 using a large territory-wide healthcare database. All microbiological tests were conducted within 48 h of hospital admission. Four etiological groups were included: (1) viral infection alone; (2) bacterial infection alone; (3) laboratory-confirmed viral-bacterial co-infection and (4) clinically suspected viral-bacterial co-infection who were tested positive for respiratory virus and negative for bacteria but had received at least four days of antibiotics. Clinical features and outcomes were recorded for laboratory-confirmed viral-bacterial co-infection patients compared to other three groups as control. The primary outcome was 30-day mortality. Secondary outcomes were intensive care unit (ICU) admission and length of hospital stay. Propensity score matching estimated by binary logistic regression was used to adjust for the potential bias that may affect the association between outcomes and covariates.

FINDINGS

Among 15,906 patients with respiratory viral infection, there were 8451 (53.1%) clinically suspected and 1,087 (6.8%) laboratory-confirmed viral-bacterial co-infection. Among all the bacterial species, Haemophilus influenzae (226/1,087, 20.8%), Pseudomonas aeruginosa (180/1087, 16.6%) and Streptococcus pneumoniae (123/1087, 11.3%) were the three most common bacterial pathogens in the laboratory-confirmed co-infection group. Respiratory viruses co-infected with non-pneumococcal streptococci or methicillin-resistant Staphylococcus aureus was associated with the highest death rate [9/30 (30%) and 13/48 (27.1%), respectively] in this cohort. Compared with other infection groups, patients with laboratory-confirmed co-infection had higher ICU admission rate (p < 0.001) and mortality rate at 30 days (p = 0.028), and these results persisted after adjustment for potential confounders using propensity score matching. Furthermore, patients with laboratory-confirmed co-infection had significantly higher mortality compared to patients with bacterial infection alone.

INTERPRETATION

In our cohort, bacterial co-infection is common in hospitalized patients with viral respiratory tract infection and is associated with higher ICU admission rate and mortality. Therefore, active surveillance for bacterial co-infection and early antibiotic treatment may be required to improve outcomes in patients with respiratory viral infection.

Antibiofilm activity of host defence peptides: complexity provides opportunities

Host defence peptides (HDPs) are integral components of innate immunity across all living organisms. These peptides can exert direct antibacterial effects, targeting planktonic cells (referred to as antimicrobial peptides), and exhibit antibiofilm (referred to as antibiofilm peptides), antiviral, antifungal and host-directed immunomodulatory activities. In this Review, we discuss how the complex functional attributes of HDPs provide many opportunities for the development of antimicrobial therapeutics, focusing particularly on their emerging antibiofilm properties. The mechanisms of action of antibiofilm peptides are compared and contrasted with those of antimicrobial peptides. Furthermore, obstacles for the practical translation of candidate peptides into therapeutics and the potential solutions are discussed. Critically, HDPs have the value-added assets of complex functional attributes, particularly antibiofilm and anti-inflammatory activities and their synergy with conventional antibiotics.

Influenza-Induced Oxidative Stress Sensitizes Lung Cells to Bacterial-Toxin-Mediated Necroptosis

Pneumonias caused by influenza A virus (IAV) co- and secondary bacterial infections are characterized by their severity and high mortality rate. Previously, we have shown that bacterial pore-forming toxin (PFT)-mediated necroptosis is a key driver of acute lung injury during bacterial pneumonia. Here, we evaluate the impact of IAV on PFT-induced acute lung injury during co- and secondary Streptococcus pneumoniae (Spn) infection. We observe that IAV synergistically sensitizes lung epithelial cells for PFT-mediated necroptosis in vitro and in murine models of Spn co-infection and secondary infection. Pharmacoelogical induction of oxidative stress without virus sensitizes cells for PFT-mediated necroptosis. Antioxidant treatment or inhibition of necroptosis reduces disease severity during secondary bacterial infection. Our results advance our understanding on the molecular basis of co- and secondary bacterial infection to influenza and identify necroptosis inhibition and antioxidant therapy as potential intervention strategies.

Critical role of microRNAs in host and influenza A (H1N1) virus interactions

As a type of non-coding RNA, microRNAs are considered to be a new regulator in viral infections. Influenza A (H1N1) virus infection is a serious threat to human health. There is growing evidence supporting that microRNAs play important roles in various cellular infection stages and host antiviral response during H1N1 infection. Some microRNAs defend against H1N1 invasion, while others may promote viral replication. MicroRNAs are implicated in the host-viral interactions and serve versatile functions in it. In this review, we focus on the innate immune response and virus replication regulated by microRNAs during H1N1 infection. MicroRNAs can influence H1N1 virus replication by directly binding to viral compositions and through host cellular pathways. Moreover, microRNAs are involved in multiple antiviral response, including production of interferons (IFNs), retinoic acid-inducible gene I (RIG-I) signaling pathway, immune cells development and secretion, activation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB). Furthermore, these regulatory effects of microRNAs suggest its potential clinical significance. In addition, another non-coding RNA, lncRNA, are also mentioned in the review, which can regulate innate immune response and influence virus replication during H1N1 infection as well.

Immunopathological Changes in SARS-CoV-2 Critical and Non-critical Pneumonia Patients: A Systematic Review to Determine the Cause of Co-infection

The ongoing COVID-19 pandemic originating from Wuhan, China is causing major fatalities across the world. Viral pneumonia is commonly observed in COVID-19 pandemic. The number of deaths caused by viral pneumonia is mainly due to secondary bacterial or fungal infection. The immunopathology of SARS-CoV-2 viral pneumonia is poorly understood with reference to human clinical data collected from patients infected by virus and secondary bacterial or fungal infection occurring simultaneously. The co-infection inside the lungs caused by pneumonia has direct impact on the changing lymphocyte and neutrophil counts. Understanding the attribution of these two immunological cells triggered by cytokines level change is of great importance to identify the progression of pneumonia from non-severe to severe state in hospitalized patients. This review elaborates the cytokines imbalance observed in SARS-CoV-1 (2003 epidemic), SARS-CoV-2 (2019 pandemic) viral pneumonia and community acquired pneumonia (CAP), respectively, in patients to determine the potential reason of co-infection. In this review the epidemiology, virology, clinical symptoms, and immunopathology of SARS-CoV-2 pneumonia are narrated. The immune activation during SARS-CoV-1 pneumonia, bacterial, and fungal pneumonia is discussed. Here it is further analyzed with the available literatures to predict the potential internal medicines, prognosis and monitoring suggesting better treatment strategy for SARS-CoV-2 pneumonia patients.

MicroRNA-4485 ameliorates severe influenza pneumonia via inhibition of the STAT3/PI3K/AKT signaling pathway

The present study aimed to explore the potential roles and mechanism of microRNA-4485 (miR-4485) in severe influenza pneumonia. miR-4485 expression was detected in patients with severe H1N1 pneumonia using quantitative PCR. Furthermore, the effects of aberrantly expressed miR-4485 on H1N1-infected A549 cells were investigated using Cell Counting Kit-8, terminal deoxynucleotidyl transferase dUTP nick end labeling, western blotting and (ELISA) assays. Furthermore, the regulatory relationships between miR-4485 and the STAT3-mediated PI3K/AKT/mTOR signaling pathway were explored using a luciferase reporter and rescue assay. MiR-4485 expression was downregulated following H1N1 infection and in patients with H1N1 pneumonia. In addition, miR-4485 alleviated H1N1-induced A549 cell injury by promoting cell viability and the production of cytokines, as well as reducing apoptosis in A549 cells. Furthermore, STAT3 was revealed to be a target gene of miR-4485. Additionally, STAT3 silencing reversed the protective effects of miR-4485 knockdown on H1N1-induced cell injury via inhibition of the PI3K/AKT/mTOR signaling pathway. In conclusion, miR-4485 inhibited H1N1-induced severe pneumonia in A549 cells by targeting STAT3 via the PI3K/AKT/mTOR signaling pathway.

Spectrum of respiratory viral infections in liver disease patients with cirrhosis admitted in critical care unit

BACKGROUND:

Clinical significance of respiratory viruses (RVs) as an etiology of pneumonia in liver disease patients with cirrhosis is usually underestimated. Therefore, the aim of this study was to evaluate the spectrum of RVs in cirrhotic patients with pneumonia admitted in critical care units (CCUs) and its impact on the clinical outcome of cirrhotic patients.

MATERIAL AND METHOD:

A prospective study was conducted in a tertiary care CCU, and consecutive cirrhotic patients with pneumonia were included. Bronchoalveolar lavage or throat swab/nasal swab was collected in viral transport medium for analysis of RVs by multiplex real-time polymerase chain reaction. A total of 135 cirrhotic patients were included, viral and bacterial etiology of pneumonia was identified, and analysis was done with the clinical outcome.

RESULTS:

Overall, RVs were detected in 30 (22.2%) cirrhotic patients and viral–bacterial coinfection in 16 (11.8%) cirrhotic patients. The most common virus detected was rhinovirus in 9 (30%) patients. Mortality in cirrhotic patients with RV infection was significantly higher in comparison to cirrhotic patients with no RV infection (25 [83.3%] and 11 [12.3%], respectively, P < 0.001).

CONCLUSION:

Respiratory viruses in cirrhotic patients with pneumonia are associated with poor clinical outcome.

Xenobiotic receptors in mediating the effect of sepsis on drug metabolism

Sepsis is an infection-induced systemic inflammatory syndrome. The immune response in sepsis is characterized by the activation of both proinflammatory and anti-inflammatory pathways. When sepsis occurs, the expression and activity of many inflammatory cytokines are markedly affected. Xenobiotic receptors are chemical-sensing transcription factors that play essential roles in the transcriptional regulation of drug-metabolizing enzymes (DMEs). Xenobiotic receptors mediate the functional crosstalk between sepsis and drug metabolism because the inflammatory cytokines released during sepsis can affect the expression and activity of xenobiotic receptors and thus impact the expression and activity of DMEs. Xenobiotic receptors in turn may affect the clinical outcomes of sepsis. This review focuses on the sepsis-induced inflammatory response and xenobiotic receptors such as pregnane X receptor (PXR), aryl hydrocarbon receptor (AHR), glucocorticoid receptor (GR), and constitutive androstane receptor (CAR), DMEs such as CYP1A, CYP2B6, CYP2C9, and CYP3A4, and drug transporters such as p-glycoprotein (P-gp), and multidrug resistance-associated protein (MRPs) that are affected by sepsis. Understanding the xenobiotic receptor-mediated effect of sepsis on drug metabolism will help to improve the safe use of drugs in sepsis patients and the development of new xenobiotic receptor-based therapeutic strategies for sepsis.

Characterization of cellular transcriptomic signatures induced by different respiratory viruses in human reconstituted airway epithelia

Acute respiratory infections, a large part being of viral origin, constitute a major public health issue. To propose alternative and/or new therapeutic approaches, it is necessary to increase our knowledge about the interactions between respiratory viruses and their primary cellular targets using the most biologically relevant experimental models. In this study, we used RNAseq to characterize and compare the transcriptomic signature of infection induced by different major respiratory viruses (Influenza viruses, hRSV and hMPV) in a model of reconstituted human airway epithelia. Our results confirm the importance of several cellular pathways commonly or specifically induced by these respiratory viruses, such as the innate immune response or antiviral defense. A very interesting common feature revealed by the global virogenomic signature shared between hRSV, hMPV and influenza viruses is the global downregulation of cilium-related gene expression, in good agreement with experimental evaluation of mucociliary clearance. Beyond providing new information about respiratory virus/host interactions, our study also underlines the interest of using biologically relevant experimental models to study human respiratory viruses.

Etiology and Risk Factors for Mortality in an Adult Community-acquired Pneumonia Cohort in Malawi

Rationale: In the context of rapid antiretroviral therapy rollout and an increasing burden of noncommunicable diseases, there are few contemporary data describing the etiology and outcome of community-acquired pneumonia (CAP) in sub-Saharan Africa.Objectives: To describe the current etiology of CAP in Malawi and identify risk factors for mortality.Methods: We conducted a prospective observational study of adults hospitalized with CAP to a teaching hospital in Blantyre, Malawi. Etiology was defined by blood culture, Streptococcus pneumoniae urinary antigen detection, sputum mycobacterial culture and Xpert MTB/RIF, and nasopharyngeal aspirate multiplex PCR.Measurements and Main Results: In 459 patients (285 [62.1%] males; median age, 34.7 [interquartile range, 29.4-41.9] yr), 30-day mortality was 14.6% (64/439) and associated with male sex (adjusted odds ratio, 2.60 [95% confidence interval, 1.17-5.78]), symptom duration greater than 7 days (2.78 [1.40-5.54]), tachycardia (2.99 [1.48-6.06]), hypoxemia (4.40 [2.03-9.51]), and inability to stand (3.59 [1.72-7.50]). HIV was common (355/453; 78.4%), frequently newly diagnosed (124/355; 34.9%), but not associated with mortality. S. pneumoniae (98/458; 21.4%) and Mycobacterium tuberculosis (75/326; 23.0%) were the most frequently identified pathogens. Viral infection occurred in 32.6% (148/454) with influenza (40/454; 8.8%) most common. Bacterial-viral coinfection occurred in 9.1% (28/307). Detection of M. tuberculosis was associated with mortality (adjusted odds ratio, 2.44 [1.19-5.01]).Conclusions: In the antiretroviral therapy era, CAP in Malawi remains predominantly HIV associated, with a large proportion attributable to potentially vaccine-preventable pathogens. Strategies to increase early detection and treatment of tuberculosis and improve supportive care, in particular the correction of hypoxemia, should be evaluated in clinical trials to address CAP-associated mortality.

Invasive Pneumococcal Disease and Influenza Activity in a Pediatric Population: Impact of PCV13 Vaccination in Pandemic and Nonpandemic Influenza Periods

The objective of this study was to analyze the incidence, clinical presentation, and severity of invasive pneumococcal disease (IPD)-causing serotypes and the impact of the 13-valent pneumococcal conjugate vaccination during epidemic and nonepidemic influenza periods in Catalonia, Spain. This was a prospective study in persons aged <18 years diagnosed with IPD between 2012 and 2015 in three Catalan pediatric hospitals. IPD was defined as clinical infection together with isolation of Streptococcus pneumoniae by culture and/or detection by reverse transcription-PCR in a normally sterile sample. Incidence rate ratios (IRRs) and the fraction of IPD prevented associated with 13-valent pneumococcal conjugate vaccine (PCV13) were calculated. The bivariate analysis used the χ² test and the multivariate analysis nonconditional logistic regression. A total of 229 cases of IPD were recorded. The incidence was higher during influenza epidemic periods (IRR, 2.7; 95% confidence interval [CI], 2.05 to 3.55; P < 0.001), especially for pneumonia (IRR, 3.25; 95% CI, 2.36 to 4.47; P < 0.001), with no differences in the distribution of pneumococcal serotypes. Complications during admission and sequel at discharge were greater during epidemic periods (adjusted odds ratio [aOR], 2.00; 95% CI, 1.06 to 3.77; P = 0.03) than at nonepidemic periods (aOR, 3.38; 95% CI, 1.37 to 8.29; P = 0.01). The prevented fraction for the population (PFp) of IPD in children aged 7 to 59 months was 48% to 49.4%. The PFp was higher in influenza epidemic than nonepidemic periods and increased when ≥2 doses of PCV13 or ≥1 after 24 months were administered. Influenza virus circulation increases the incidence of IPD in persons aged <18 years. In influenza epidemic periods, IPD cases were more severe. Increased PCV13 coverage might increase the fraction of IPD prevented in epidemic and nonepidemic periods.

Clinical Efficacy and Safety of Mechanical Ventilation Combined with Fiberoptic Bronchoalveolar Lavage in Patients with Severe Pulmonary Infection

Background

The aim of this study was to assess the clinical efficacy and safety of mechanical ventilation combined with fiberoptic bronchoalveolar lavage in patients with severe pulmonary infection.

Material/Methods

We randomly divided 81 patients with severe pulmonary infection into a control group (n=40) and an observation group (n=41). Both groups were treated using mechanical ventilation, and observation group additionally received assistive fiberoptic bronchoalveolar lavage.

Results

The cure rate and effectiveness rate in the observation group were higher than in the control group (P<0.05, χ²=3.2), and the incidence of ventilator-associated pneumonia in the observation group was significantly lower than that in the control group (P<0.05, χ²=9.4). The partial pressure of oxygen (PaO₂) and oxygen saturation (SaO₂) were higher in the observation group than in the control group (P<0.05, t=3.862, t=33.595), whereas the partial pressure of carbon dioxide (PaCO₂) and respiratory rate were lower in the observation group than in the control group (P<0.05, t=3.307, t=5.043). The levels of C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) in the 2 groups were lower after treatment than before treatment (all P<0.05), and the levels in the observation group were lower than those in the control group (all P<0.05). Hospital stay, infection control window appearance time, invasive mechanical ventilation time, and total mechanical ventilation time in the observation group were shorter than those in the control group (P<0.05, t=13.990, t=8.643, t=9.717, t=8.980).

Conclusions

Mechanical ventilation combined with fiberoptic bronchoalveolar lavage can effectively improve the curative effects and the blood gas and inflammation indicators in patients.

Direct interaction of whole-inactivated influenza A and pneumococcal vaccines enhances influenza-specific immunity

The upper respiratory tract is continuously exposed to a vast array of potentially pathogenic viruses and bacteria. Influenza A virus (IAV) has particular synergism with the commensal bacterium Streptococcus pneumoniae in this niche, and co-infection exacerbates pathogenicity and causes significant mortality. However, it is not known whether this synergism is associated with a direct interaction between the two pathogens. We have previously reported that co-administration of a whole-inactivated IAV vaccine (γ-Flu) with a whole-inactivated pneumococcal vaccine (γ-PN) enhances pneumococcal-specific responses. In this study, we show that mucosal co-administration of γ-Flu and γ-PN similarly augments IAV-specific immunity, particularly tissue-resident memory cell responses in the lung. In addition, our in vitro analysis revealed that S. pneumoniae directly interacts with both γ-Flu and with live IAV, facilitating increased uptake by macrophages as well as increased infection of epithelial cells by IAV. These observations provide an additional explanation for the synergistic pathogenicity of IAV and S. pneumoniae, as well as heralding the prospect of exploiting the phenomenon to develop better vaccine strategies for both pathogens.

Quantitative profiling of cytokines and chemokines in DOCK8-deficient and atopic dermatitis patients

BACKGROUND

Hyper-IgE syndromes (HIES) are a clinically overlapping, heterogeneous group of inborn errors of immunity characterized by elevated serum IgE level, eosinophilia, atopy, and immune dysregulation. Deficiency of DOCK8 protein is potentially a life-threatening autosomal recessive HIES and only curable with bone marrow transplantation. Hence, the diagnosis of DOCK8 deficiency is critical and should be sought at an early stage to initiate definitive therapy.

METHODS

Serum samples from patients with DOCK8 deficiency and atopic dermatitis were profiled on a cytokine/chemokine panel for potential differential expression.

RESULTS

CXCL10 and TNF-A were upregulated in DOCK8 patients when compared to AD, possibly contributing toward increased susceptibility to infections and cancer. In contrast, epidermal growth factor (EGF) was significantly downregulated in a subgroup of DOCK8-deficient and AD patients, while IL-31 expression was comparable between both DOCK8-deficient and AD cohorts, possibly contributing toward pruritus seen in both groups.

CONCLUSION

This comprehensive cytokine profile in HIES patients reveals distinctive biomarkers that differentiate between the DOCK8-deficient and AD patients. The unique expression profile of various inflammatory cytokines in patients with DOCK8 deficiency vs atopic dermatitis likely reflects disease-specific perturbations in multiple cellular processes and pathways leading to a predisposition to infections and allergies seen in these patients. These data agree with the role for EGF replacement therapy in EGF-deficient individuals with AD as well as DOCK8 deficiency through a potential shared pathway. In addition, these novel biomarkers may be potentially useful in distinguishing DOCK8 deficiency from AD allowing early-targeted treatment options.

Interleukin-5, interleukin-6, interferon induced protein-10, procalcitonin and C-reactive protein among mechanically ventilated severe community-acquired viral and bacterial pneumonia patients

BACKGROUND

The serum cytokine levels among 45 mechanically ventilated, intensive care unit (ICU)-treated severe community-acquired pneumonia (SCAP) patients with known microbial etiology in three different etiology groups were assessed.

METHODS

Blood samples for C-reactive protein (CRP), procalcitonin (PCT), interleukin (IL)-5, IL-6, IL-10, human interferon gamma induced protein (IP)-10, and TNF-α (tumor necrosis factor alpha) were collected at time points 0, 12, 24, 48, 72 and 96 h after study inclusion.

RESULTS

There were 21 (43%) pure bacterial infections (bacterial group, BG), 5 (10%) pure viral infections (viral group, VG), and 19 (39%) mixed bacterial-viral infections (mixed group, MG) among 45 mechanically ventilated SCAP patients. CRP and PCT levels were significantly higher in the MG and values decreased with time in all groups. PCT differed also in time and group analysis (P = 0.001), the highest being in the MG. IL-5 levels were significantly higher in the VG compared to others (Ptime = 0.001, Pgroup = 0.051 and Ptimexgroup = 0.016). IL-6 and IP-10 levels decreased over time (Ptime = 0.003 and Ptime = 0.021), but there were no differences between groups.

CONCLUSION

SCAP patients with viral etiology have higher IL-5 levels. Patients with mixed viral and bacterial group have higher PCT compared to other etiologies.

Association of High Mobility Group Box Protein B1 Gene Polymorphisms with Pneumonia Susceptibility and Severity

OBJECTIVE

To investigate the relationship between the high mobility group box protein B1 (HMGB1) single nucleotide polymorphisms (SNPs) rs1412125, rs2249825, and rs1045411 with pneumonia in terms of susceptibility, severity, and inflammatory response.

METHODS

The genotypes of HMGB1 rs1412125 (-1615T > C), rs2249825 (3814C > G), and rs1045411 (2262C > T) loci in 328 patients with community-acquired pneumonia (CAP) and 317 healthy subjects were analyzed by Sanger sequencing. The expression and secretion of the inflammatory cytokines HMGB1, interleukin (IL)-10, tumor necrosis factor-alpha (TNF-α), and IL-6 were determined after lipopolysaccharide (LPS) stimulation of peripheral whole blood cells.

RESULTS

The risk of CAP was higher in carriers of the mutant HMGB1 rs1412125 and rs2249825 alleles than those that had the wild type alleles (adjusted odds ratio [OR] = 1.241; 95% confidence interval [CI] = 1.061-1.448; p = 0.007; adjusted OR = 1.225; 95% CI = 1.038-1.427; p = 0.016, respectively). Moreover, the mutation-carrying patients with CAP were more likely to develop severe community-acquired pneumonia (SCAP). There was no correlation between the HMGB1 rs1045411 SNP alleles and CAP or SCAP (p > 0.05). The expression and secretion of the inflammatory cytokines HMGB1, IL-10, TNF-α, and IL-6 was significantly higher in LPS-stimulated peripheral blood among patients with mutations at the rs1412125 and rs2249825 loci compared with those with wild type alleles (p < 0.05). The 30-day mortality rates for CAP patients with mutations at the rs1412125 and rs2249825 loci of HMGB1 were significantly higher than those that had wild type alleles. The mortality rate difference between rs1045411 wild-type CAP patients and mutant was not significant (p = 0.789).

CONCLUSION

SNPs at the rs1412125 and rs2249825 loci of HMGB1 are associated with pneumonia in terms of susceptibility, severity, and inflammatory response.

MicroRNA‑124‑3p attenuates severe community‑acquired pneumonia progression in macrophages by targeting tumor necrosis factor receptor‑associated factor 6

Community‑acquired pneumonia (CAP) is a severe type of pneumonia in adults, with a high mortality rate. Macrophages have been reported to mediate severe CAP (SCAP) in vitro following administration of LPS. Therefore, the present study established a SCAP model in Ana‑1 macrophages by lipopolysaccharide (LPS) induction, and aimed to explore the function of microRNA (miR)‑124‑3p in the LPS‑induced SCAP. The effect of LPS on Ana‑1 cell viability was evaluated by an MTT assay. In addition, the protein and mRNA levels of interleukin (IL)‑1β and tumor necrosis factor (TNF)‑α were determined by enzyme‑linked immunosorbent assay and reverse transcription‑quantitative polymerase chain reaction, respectively. The nuclear factor (NF)‑κB activity and phosphorylation of p38 mitogen‑activated protein kinase (MAPK) were also evaluated by western blotting. The results demonstrated that exposure to 0.1 µg/ml LPS displayed no evident toxicity on macrophages. Compared with the control group, higher TNF receptor‑associated factor 6 (TRAF6) mRNA and protein levels were observed subsequent to induction by LPS (0.1 µg/ml), suggesting the promoting role of TRAF6 in SCAP. Furthermore, miR‑124‑3p was proven to target the 3'‑untranslated region (3'UTR) of TRAF6. The miR‑124‑3p mimic effectively inhibited the LPS‑induced upregulation of IL‑1β and TNF‑α secretion, and mRNA expression levels in macrophages, which may be mediated by the p38 MAPK and NF‑κB signaling pathway. Taken together, these results strongly indicated that miR‑124‑3p targeted the 3'UTR of TRAF6, while it attenuated SCAP by reducing LPS‑induced inflammatory cytokine production and inhibiting the activation of p38 MAPK and NF‑κB signaling pathways. These findings indicate the immunoregulatory role of miR‑124‑3p against macrophage‑mediated SCAP.

Inflammation induced by influenza virus impairs human innate immune control of pneumococcus

Colonization of the upper respiratory tract by pneumococcus is important both as a determinant of disease and for transmission into the population. The immunological mechanisms that contain pneumococcus during colonization are well studied in mice but remain unclear in humans. Loss of this control of pneumococcus following infection with influenza virus is associated with secondary bacterial pneumonia. We used a human challenge model with type 6B pneumococcus to show that acquisition of pneumococcus induced early degranulation of resident neutrophils and recruitment of monocytes to the nose. Monocyte function was associated with the clearance of pneumococcus. Prior nasal infection with live attenuated influenza virus induced inflammation, impaired innate immune function and altered genome-wide nasal gene responses to the carriage of pneumococcus. Levels of the cytokine CXCL10, promoted by viral infection, at the time pneumococcus was encountered were positively associated with bacterial load.

Transmission Electron Microscopy Improves the Diagnostic Sensitivity in Nonbacterial Etiology of Severe Pneumonia: A Retrospective Study

Background

Severe pneumonia is responsible for great mortality and morbidity worldwide, and early-applied effective anti-infective therapy can improve the prognosis of patients. However, identification of infectious agents in severe pneumonia remains a major challenge so far. In this study, the potential utility of transmission electron microscopy (TEM) in detecting nonbacterial pathogens in patients with severe pneumonia was retrospectively evaluated.

Materials and Methods

A total of 106 patients diagnosed with severe pneumonia at our hospital from September 2015 to December 2017 were included, and their baseline clinical characteristics were collected. Nonbacterial infectious agents detected by TEM in bronchoalveolar lavage fluid (BALF) and serological tests were summarized. The detection rates were further compared between TEM and serological tests.

Results

BALF examination under the transmission electron microscope revealed 24 viruses, 16 mycoplasmas, 18 chlamydia, 2 fungi and 74 bacteria in 99 samples, among which 61 samples were mixed infections. The combined use of serological tests and TEM significantly improved the detection rate of nonbacterial infectious agents in patients with severe pneumonia.

Conclusions

Our data support that implementation of TEM could improve the sensitivity for detecting viruses, atypical pathogens and mixed infections in BALF from patient of severe pneumonia. Therefore, TEM may be used as an auxiliary diagnostic method of other microbiological tests in severe pneumonia.

Streptococcus pneumoniae's Virulence and Host Immunity: Aging, Diagnostics, and Prevention

Streptococcus pneumoniae is an infectious pathogen responsible for millions of deaths worldwide. Diseases caused by this bacterium are classified as pneumococcal diseases. This pathogen colonizes the nasopharynx of its host asymptomatically, but overtime can migrate to sterile tissues and organs and cause infections. Pneumonia is currently the most common pneumococcal disease. Pneumococcal pneumonia is a global health concern and vastly affects children under the age of five as well as the elderly and individuals with pre-existing health conditions. S. pneumoniae has a large selection of virulence factors that promote adherence, invasion of host tissues, and allows it to escape host immune defenses. A clear understanding of S. pneumoniae's virulence factors, host immune responses, and examining the current techniques available for diagnosis, treatment, and disease prevention will allow for better regulation of the pathogen and its diseases. In terms of disease prevention, other considerations must include the effects of age on responses to vaccines and vaccine efficacy. Ongoing work aims to improve on current vaccination paradigms by including the use of serotype-independent vaccines, such as protein and whole cell vaccines. Extending our knowledge of the biology of, and associated host immune response to S. pneumoniae is paramount for our improvement of pneumococcal disease diagnosis, treatment, and improvement of patient outlook.

The Opp (AmiACDEF) Oligopeptide Transporter Mediates Resistance of Serotype 2 Streptococcus pneumoniae D39 to Killing by Chemokine CXCL10 and Other Antimicrobial Peptides

Antimicrobial peptides (AMPs), including chemokines, are produced during infections to kill pathogenic bacteria. To fill in gaps in knowledge about the sensitivities of Streptococcus pneumoniae and related Streptococcus species to chemokines and AMPs, we performed a systematic, quantitative study of inhibition by chemokine CXCL10 and the AMPs LL-37 and nisin. In a standard Tris-glucose buffer (TGS), all strains assayed lacked metabolic activity, as determined by resazurin (alamarBlue) reduction, and were extremely sensitive to CXCL10 and AMPs (50% inhibitory concentration [IC₅₀], ∼0.04 μM). In TGS, changes in sensitivities caused by mutations were undetectable. In contrast, strains that retained reductive metabolic activity in a different assay buffer (NPB [10 mM sodium phosphate {pH 7.4}, 1% {vol/vol} brain heart infusion {BHI} broth]) were less sensitive to CXCL10 and AMPs than in TGS. In NPB, mutants known to respond to AMPs, such as Δdlt mutants lacking d-alanylation of teichoic acids, exhibited the expected increased sensitivity. S. pneumoniae serotype 2 strain D39 was much (∼10-fold) less sensitive to CXCL10 killing in NPB than serotype 4 strain TIGR4, and the sensitivity of TIGR4 was unaffected by the absence of capsule. Candidate screening of strain D39 revealed that mutants lacking Opp (ΔamiACDEF) oligopeptide permease were significantly more resistant to CXCL10 than the wild-type strain. This increased resistance could indicate that Opp is a target for CXCL10 binding or that it transports CXCL10 into cells. Finally, ΔftsX or ΔftsE mutants of Bacillus subtilis or amino acid changes that interfere with FtsX function in S. pneumoniae did not impart resistance to CXCL10, in contrast to previous results for Bacillus anthracis, indicating that FtsX is not a general target for CXCL10 binding.IMPORTANCES. pneumoniae (pneumococcus) is a human commensal bacterium and major opportunistic respiratory pathogen that causes serious invasive diseases, killing millions of people worldwide annually. Because of its increasing antibiotic resistance, S. pneumoniae is now listed as a "superbug" for which new antibiotics are urgently needed. This report fills in knowledge gaps and resolves inconsistencies in the scientific literature about the sensitivity of S. pneumoniae and related Streptococcus pathogens to chemokines and AMPs. It also reveals a new mechanism by which S. pneumoniae can acquire resistance to chemokine CXCL10. This mechanism involves the Opp (AmiACDEF) oligopeptide transporter, which plays additional pleiotropic roles in pneumococcal physiology, quorum sensing, and virulence. Taking the results together, this work provides new information about the way chemokines kill pneumococcal cells.

Role of p53/NF-κB functional balance in respiratory syncytial virus-induced inflammation response

The interplay between respiratory syncytial virus (RSV) and the p53 pathway has only been reported in a limited number of studies, yet the underlying abrogation mechanisms of p53 activity during the time course of infection, possibly involving viral proteins, remained unclear. Here, we demonstrate that RSV infection impairs global p53 transcriptional activity, notably via its proteasome-dependent degradation at late stages of infection. We also demonstrate that NS1 and NS2 contribute to the abrogation of p53 activity, and used different experimental strategies (e.g. siRNA, small molecules) to underline the antiviral contribution of p53 in the context of RSV infection. Notably, our study highlights a strong RSV-induced disequilibrium of the p53/NF-κB functional balance, which appears to contribute to the up-regulation of the expression of several proinflammatory cytokines and chemokines.

RSV Infection in Human Macrophages Promotes CXCL10/IP-10 Expression during Bacterial Co-Infection

Respiratory syncytial virus (RSV), a major etiologic agent of acute lower respiratory infection constitutes the most important cause of death in young children worldwide. Viral/bacterial mixed infections are related to severity of respiratory inflammatory diseases, but the underlying mechanisms remain poorly understood. We have previously investigated the intracellular mechanisms that mediate the immune response in the context of influenza virus/Streptococcus pneumoniae (Sp) co-infection using a model of human monocyte-derived macrophages (MDMs). Here, we set up and characterized a similar model of MDMs to investigate different scenarios of RSV infection and co-infection with Sp. Our results suggest that Sp contributes to a faster and possibly higher level of CXCL10/IP-10 expression induced by RSV infection in human MDMs.

Impaired expression of CXCL5 and matrix metalloproteinases in the lungs of mice with high susceptibility to Streptococcus pneumoniae infection

Introduction

Streptococcus pneumoniae colonizes the nasopharynx of healthy individuals establishing a commensal relationship with the host. In some conditions, bacteria invade the lower respiratory tract and innate immune responses are crucial to avoid diseases such as pneumonia, sepsis, or meningitis.

Methods

Here, we compared the susceptibility to pneumococcal respiratory infection of two outbred mouse lines, AIRmin and AIRmax, selected for low or high acute inflammatory responses, respectively.

Results

AIRmin mice showed increased susceptibility to infection with different pneumococcal serotypes, when compared to AIRmax. Significant higher numbers of alveolar macrophages expressing the CD206 mannose receptor were observed in AIRmin mice when compared to AIRmax mice. Despite this difference, secretion of several cytokines and chemokines in the respiratory tract of AIRmin and AIRmax mice, after infection, was similar. The only exception was CXCL5, which was highly induced after pneumococcal infection in AIRmax mice but not in AIRmin mice. Reduced expression of the matrix metalloproteinases (MMP) 2, 3, 8, and 9, as well as reduced activities of MMPs were also observed in the lungs of AIRmin mice, after infection. Such impaired responses may have contributed to the low influx of neutrophils observed in the airways of these mice. Finally, high percentages of macrophages and neutrophils in apoptosis or necrosis, at the site of infection, were also observed in AIRmin mice, suggesting that leukocyte functionality is also compromised.

Conclusions

Our results indicate that CXCL5 and MMPs contribute to the resistance to pneumococcal infection in mice.

Secondary Bacterial Infections Associated with Influenza Pandemics

Lower and upper respiratory infections are the fourth highest cause of global mortality (Lozano et al., 2012). Epidemic and pandemic outbreaks of respiratory infection are a major medical concern, often causing considerable disease and a high death toll, typically over a relatively short period of time. Influenza is a major cause of epidemic and pandemic infection. Bacterial co/secondary infection further increases morbidity and mortality of influenza infection, with Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus reported as the most common causes. With increased antibiotic resistance and vaccine evasion it is important to monitor the epidemiology of pathogens in circulation to inform clinical treatment and development, particularly in the setting of an influenza epidemic/pandemic.