Respiratory influenza virus infection induces intestinal immune injury via microbiota-mediated Th17 cell-dependent inflammation

Intestinal Microbiota Disruption Reduces Regulatory T Cells and Increases Respiratory Viral Infection Mortality Through Increased IFNγ Production

Alterations in gastrointestinal microbiota indirectly modulate the risk of atopic disease, but effects on respiratory viral infections are less clear. Using the murine paramyxoviral virus type 1, Sendai virus (SeV), we examined the effect of altering gastrointestinal microbiota on the pulmonary antiviral immune response. C57BL6 mice were treated with streptomycin before or during infection with SeV and resulting immune response studied. Ingestion of the non-absorbable antibiotic streptomycin led to a marked reduction in intestinal microbial diversity without a significant effect on lung microbiota. Reduction in diversity in the gastrointestinal tract was followed by greatly increased mortality to respiratory viral infection (p < 0.0001). This increase in mortality was associated with a dysregulated immune response characterized by decreased lung (p = 0.01) and intestinal (p = 0.03) regulatory T cells (Tregs), and increased lung IFNγ (p = 0.049), IL-6 (p = 0.015), and CCL2 (p = 0.037). Adoptive transfer of Treg cells or neutralization of IFNγ prevented increased mortality. Furthermore, Lin^-CD4⁺ cells appeared to be a potential source of the increased IFNγ. Together, these results demonstrate gastrointestinal microbiota modulate immune responses at distant mucosal sites and have the ability to significantly impact mortality in response to a respiratory viral infection.

Houttuynia cordata polysaccharides ameliorate pneumonia severity and intestinal injury in mice with influenza virus infection

ETHNOPHARMACOLOGICAL RELEVANCE

Hottuynia cordata is an important traditional Chinese medicine for the treatment of respiratory diseases including bacterial and viral infections. Polysaccharides isolated from Houttuynia cordata (HCP), as its main ingredients, have been demonstrated to ameliorate the LPS-induced acute lung injury in mice. The study aimed to determine the protective effects of HCP on multiple organ injury in influenza A virus (IAV) H1N1 infected mice and its primary mechanisms in anti-inflammation and immune regulation.

MATERIALS AND METHODS

Mice were inoculated with IAV H1N1 and then treated with 20 or 40 mg/kg/d of HCP for survival test and acute lung-gut injury test.

RESULTS

The treatment with HCP resulted in an increase in the survival rate of H1N1 infected mice and the protection from lung and intestine injury, accompanied with the reduced virus replication. HCP markedly decreased the concentration of pulmonary proinflammatory cytokines/chemokines and the number of intestinal goblet cells, and strengthened the intestinal physical and immune barrier, according to the increase of sIgA and tight junction protein (ZO-1) in intestine. At the same time, the inhibition of inflammation in lung and gut was related to the suppressing of the expression of TLR4 and p-NFκB p65 in lung.

CONCLUSIONS

These results indicated that HCP ameliorated lung and intestine injury induced by IAV attack. The mechanisms were associated with inhibition of inflammation, protection of intestinal barrier and regulation of mucosal immunity, which may be related to the regulation of gut-lung axis. As an alternative medicine, HCP may have clinical potential to treat IAV infection in human beings.

Avian Influenza Virus Subtype H9N2 Affects Intestinal Microbiota, Barrier Structure Injury, and Inflammatory Intestinal Disease in the Chicken Ileum

Avian influenza virus subtype H9N2 (H9N2 AIV) has caused significant losses to the poultry industry due to the high mortality associated with secondary infections attributable to E. coli. This study tries to address the underlying secondary mechanisms after H9N2 AIV infection. Initially, nine day-old specific pathogen-free chickens were assigned to control (uninfected) and H9N2-infected groups, respectively. Using Illumina sequencing, histological examination, and quantitative real-time PCR, it was found that H9N2 AIV caused intestinal microbiota disorder, injury, and inflammatory damage to the intestinal mucosa. Notably, the genera Escherichia, especially E. coli, significantly increased (p < 0.01) at five days post-infection (dpi), while Lactobacillus, Enterococcus, and other probiotic organisms were significantly reduced (p < 0.01). Simultaneously, the mRNA expression of tight junction proteins (ZO-1, claudin 3, and occludin), TFF2, and Muc2 were significantly reduced (p < 0.01), indicating the destruction of the intestinal epithelial cell tight junctions and the damage of mucin layer construction. Moreover, the mRNA expression of proinflammatory cytokines IFN-γ, IL-22, IFN-α, and IL-17A in intestinal epithelial cells were significantly upregulated, resulting in the inflammatory response and intestinal injury. Our findings may provide a theoretical basis for observed gastroenteritis-like symptoms such as diarrhea and secondary E. coli infection following H9N2 AIV infection.

Influence of Novel Highly Pathogenic Avian Influenza A (H5N1) Virus Infection on Migrating Whooper Swans Fecal Microbiota

The migration of wild birds plays an important role in the transmission and spread of H5 highly pathogenic avian influenza (HPAI) virus, posing a severe risk to animal and human health. Substantial evidence suggests that altered gut microbial community is implicated in the infection of respiratory influenza virus. However, the influence of H5N1 infection in gut microbiota of migratory birds remains unknown. In January 2015, a novel recombinant H5N1 virus emerged and killed about 100 migratory birds, mainly including whooper swans in Sanmenxia Reservoir Area of China. Here, we describe the first fecal microbiome diversity study of H5N1-infected migratory birds. By investigating the influence of H5N1 infection on fecal bacterial communities in infected and uninfected individuals, we found that H5N1 infection shaped the gut microbiota composition by a difference in the dominance of some genera, such as Aeromonas and Lactobacillus. We also found a decreased α diversity and increased β diversity in infectious individuals. Our results highlight that increases in changes in pathogen-containing gut communities occur when individuals become infected with H5N1. Our study may provide the first evidence that there are statistical association among H5N1 presence and fecal microbiota compositional shifts, and properties of the fecal microbiota may serve as the risk of gut-linked disease in migrates with H5N1 and further aggravate the disease transmission.

Respiratory Disease following Viral Lung Infection Alters the Murine Gut Microbiota

Alterations in the composition of the gut microbiota have profound effects on human health. Consequently, there is great interest in identifying, characterizing, and understanding factors that initiate these changes. Despite their high prevalence, studies have only recently begun to investigate how viral lung infections have an impact on the gut microbiota. There is also considerable interest in whether the gut microbiota could be manipulated during vaccination to improve efficacy. In this highly controlled study, we aimed to establish the effect of viral lung infection on gut microbiota composition and the gut environment using mouse models of common respiratory pathogens respiratory syncytial virus (RSV) and influenza virus. This was then compared to the effect of live attenuated influenza virus (LAIV) vaccination. Both RSV and influenza virus infection resulted in significantly altered gut microbiota diversity, with an increase in Bacteroidetes and a concomitant decrease in Firmicutes phyla abundance. Although the increase in the Bacteroidetes phylum was consistent across several experiments, differences were observed at the family and operational taxonomic unit level. This suggests a change in gut conditions after viral lung infection that favors Bacteroidetes outgrowth but not individual families. No change in gut microbiota composition was observed after LAIV vaccination, suggesting that the driver of gut microbiota change is specific to live viral infection. Viral lung infections also resulted in an increase in fecal lipocalin-2, suggesting low-grade gut inflammation, and colonic Muc5ac levels. Owing to the important role that mucus plays in the gut environment, this may explain the changes in microbiota composition observed. This study demonstrates that the gut microbiota and the gut environment are altered following viral lung infections and that these changes are not observed during vaccination. Whether increased mucin levels and gut inflammation drive, or are a result of, these changes is still to be determined.

Intestinal microbiota in patients with chronic hepatitis C with and without cirrhosis compared with healthy controls

BACKGROUND & AIMS

The importance of the intestinal microbiota for the onset and clinical course of many diseases, including liver diseases like non-alcoholic steatohepatitis and cirrhosis, is increasingly recognized. However, the role of intestinal microbiota in chronic hepatitis C virus (HCV) infection remains unclear.

METHODS

In a cross-sectional approach, the intestinal microbiota of 95 patients chronically infected with HCV (n=57 without cirrhosis [NO-CIR]; n=38 with cirrhosis [CIR]) and 50 healthy controls (HC) without documented liver diseases was analysed.

RESULTS

Alpha diversity, measured by number of phylotypes (S) and Shannon diversity index (H'), decreased significantly from HC to NO-CIR to CIR. S and H' correlated negatively with liver elastography. Analysis of similarities revealed highly statistically significant differences in the microbial communities between HC, NO-CIR and CIR (R=.090; P<1.0×10^-6 ). Stratifying for HCV genotypes even increased the differences. In addition, we observed distinct patterns in the relative abundance of genera being either positive or negative correlated with diseases status.

CONCLUSIONS

This study shows that not only the stage of liver disease but also HCV infection is associated with a reduced alpha diversity and different microbial community patterns. These differences might be caused by direct interactions between HCV and the microbiota or indirect interactions facilitated by the immune system.

Correlation of Severity of Functional Gastrointestinal Disease Symptoms with that of Asthma and Chronic Obstructive Pulmonary Disease: A Multicenter Study

Introduction

There is a growing clinical awareness about the influence of gut-lung axis on lung injury and coexisting manifestations of disease processes in both the intestine and lungs. Patients of chronic lung diseases such as chronic obstructive pulmonary disease (COPD) and asthma very often present with coexistent gut symptoms. In the present study, we have tried to establish the correlation of severity of pulmonary pathology of COPD and asthma patients with functional gastrointestinal (GI) symptoms of the patients.

Materials and Methods

This is a prospective, questionnaire-based study comprising patients with asthma and COPD. After following strict inclusion and exclusion criteria, a total of 200 patients (100 patients of bronchial asthma and 100 patients of COPD) were included in the study. Functional GI symptom questionnaire [Annexure 1-Bowel Disease Questionnaire] is based on ROME III diagnostic criteria. On the basis of GOLD (Global Initiative for Obstructive Lung Disease) guidelines, COPD patients were divided into 4 categories (mild - GOLD 1, moderate - GOLD2, severe - GOLD3 and very severe - GOLD4). Asthma patients were divided into three categories (well controlled, partly controlled, uncontrolled) on the basis of GINA (Global Initiative for Asthma) guidelines.

Results

Highest percentage of patients with maximum GI symptoms was found in "GOLD-4" group among COPD patients and "uncontrolled" group among asthma patients. Highest percentage of patients with least GI symptoms was found in "GOLD-1" group among COPD patients and "well controlled" group among asthma patients.

Conclusion

We can conclude from our study that the phenomenon of gut-lung axis not only exists but also the severity of symptoms of one system (gut) carries a high degree of concordance with severity of other (lung).

Effects of Th17 cells and IL-17 in the progression of cervical carcinogenesis with high-risk human papillomavirus infection

The existence of Th17 cells and IL‐17 was recently shown in several types of infectious diseases, but their distribution and functions in cervical lesions with high‐risk human papillomavirus (HPV) infection have not been fully elucidated. In this study, the frequency of Th17 cells in peripheral blood samples obtained from 28 cervical squamous cell carcinoma patients, 26 CIN1 patients, 30 CIN2 patients, 29 CIN3 patients, 25 high‐risk HPV‐infected women with normal cervical cytology, and 30 healthy controls was determined by flow cytometry. Besides, the levels of IL‐17 in peripheral blood samples as well as in supernatant of cervical tissue homogenate were assessed by enzyme‐linked immunosorbent assay (ELISA) simultaneously. We found that during the disease progression of cervical lesions, the proportion of Th17 cells in the total CD4⁺ cells showed a gradually increased tendency compared with the controls (P < 0.05). Moreover, levels of IL‐17 in serum and supernatant of cervical tissue homogenate showed the same tendency as the proportion of Th17 cells (P < 0.05). When compared in pairs, the levels of IL‐17 in supernatant differed significantly among the study groups and the control group (P < 0.05), but no significant difference was observed in serum (P > 0.05). In conclusions, the results indicate that Th17 cells and IL‐17 may play a role of immune enhancement in the infection of high‐risk HPV especially in the cervical microenvironment, which contribute to the disease progression of its associated cervical lesions.

Microbiomes in respiratory health and disease: An Asia-Pacific perspective

There is currently enormous interest in studying the role of the microbiome in health and disease. Microbiome's role is increasingly being applied to respiratory diseases, in particular COPD, asthma, cystic fibrosis and bronchiectasis. The changes in respiratory microbiomes that occur in these diseases and how they are modified by environmental challenges such as cigarette smoke, air pollution and infection are being elucidated. There is also emerging evidence that gut microbiomes play a role in lung diseases through the modulation of systemic immune responses and can be modified by diet and antibiotic treatment. There are issues that are particular to the Asia-Pacific region involving diet and prevalence of specific respiratory diseases. Each of these issues is further complicated by the effects of ageing. The challenges now are to elucidate the cause and effect relationships between changes in microbiomes and respiratory diseases and how to translate these into new treatments and clinical care. Here we review the current understanding and progression in these areas.

Time-series analysis: variation of anti-acetylcholine receptor antibody titer in myasthenia gravis is related to incidence of Mycoplasma pneumoniae and influenza virus infections

Objectives The exacerbating factors of myasthenia gravis (MG) are unknown. However, it has been speculated that infections may play a role in disease progression. Methods We calculated the adjusted anti-acetylcholine receptor antibody (Adj-AChR-Ab) titers (range, 0-1) in 58 MG patients between 2006 and 2012. We determined the relationship between Adj-AChR-Ab titer and infection incidence. Results A cross-correlation function (CCF) analysis of Adj-AChR-Ab titer and incidence of Mycoplasma pneumoniae (M. pneumoniae) (r = 0.449, P < 0.0001) and influenza virus (r = 0.411, P < 0.001) infections indicated significant correlations. MG with thymoma was highly correlated with M. pneumoniae infection (r = 0.798, P < 0.0001). The relative risk for Adj-AChR-Ab titer was 1.407 for M. pneumoniae (95% CI, 1.193-1.661 for an increase in one infected patient per monitoring point) and 1.158 for influenza (95% CI, 1.071-1.253 for 100 infected patients). Conclusion Variation of Adj-AChR-Ab titer is significantly influenced by the presence of M. pneumoniae and influenza virus infections.

Effects of urban coarse particles inhalation on oxidative and inflammatory parameters in the mouse lung and colon

Background

Air pollution is a recognized aggravating factor for pulmonary diseases and has notably deleterious effects on asthma, bronchitis and pneumonia. Recent studies suggest that air pollution may also cause adverse effects in the gastrointestinal tract. Accumulating experimental evidence shows that immune responses in the pulmonary and intestinal mucosae are closely interrelated, and that gut-lung crosstalk controls pathophysiological processes such as responses to cigarette smoke and influenza virus infection. Our first aim was to collect urban coarse particulate matter (PM) and to characterize them for elemental content, gastric bioaccessibility, and oxidative potential; our second aim was to determine the short-term effects of urban coarse PM inhalation on pulmonary and colonic mucosae in mice, and to test the hypothesis that the well-known antioxidant N-acetyl-L-cysteine (NAC) reverses the effects of PM inhalation.

Results

The collected PM had classical features of urban particles and possessed oxidative potential partly attributable to their metal fraction. Bioaccessibility study confirmed the high solubility of some metals at the gastric level. Male mice were exposed to urban coarse PM in a ventilated inhalation chamber for 15 days at a concentration relevant to episodic elevation peak of air pollution. Coarse PM inhalation induced systemic oxidative stress, recruited immune cells to the lung, and increased cytokine levels in the lung and colon. Concomitant oral administration of NAC reversed all the observed effects relative to the inhalation of coarse PM.

Conclusions

Coarse PM-induced low-grade inflammation in the lung and colon is mediated by oxidative stress and deserves more investigation as potentiating factor for inflammatory diseases.

Electronic supplementary material

The online version of this article (10.1186/s12989-017-0227-z) contains supplementary material, which is available to authorized users.

Clinical and virological factors associated with gastrointestinal symptoms in patients with acute respiratory infection: a two-year prospective study in general practice medicine

Background

Gastrointestinal (GI) symptoms, such as diarrhea, vomiting, abdominal pain and nausea are not an uncommon manifestation of an acute respiratory infection (ARI).

We therefore evaluated clinical and microbiological factors associated with the presence of GI symptoms in patients consulting a general practitioner (GP) for ARI.

Methods

Nasopharyngeal swabs, stool specimens and clinical data from patients presenting to GPs with an ARI were prospectively collected during two winter seasons (2014-2016). Samples were tested by quantitative real-time PCR for 12 respiratory pathogen groups and for 12 enteric pathogens.

Results

Two hundred and four of 331 included patients (61.6%) were positive for at least one respiratory pathogen. Sixty-nine stools (20.8%) were positive for at least one pathogen (respiratory and/or enteric). GI symptoms were more likely declared in case of laboratory confirmed-enteric infection (adjusted odds ratio (aOR) = 3.2; 95% confidence interval [CI] [1.2–9.9]; p = 0.02) or human coronavirus (HCoV) infection (aOR = 2.7; [1.2–6.8]; p = 0.02). Consumption of antipyretic medication before the consultation seemed to reduce the risk of developing GI symptoms for patients with laboratory-confirmed influenza (aOR = 0.3; [0.1–0.6]; p = 0.002).

Conclusions

The presence of GI symptoms in ARI patients could not be explained by the detection of respiratory pathogens in stools. However, the detection of enteric pathogens in stool samples could explained by the presence of GI symptoms in some of ARI cases. The biological mechanisms explaining the association between the presence of HCoVs in nasopharynx and GI symptoms need to be explored.

Electronic supplementary material

The online version of this article (10.1186/s12879-017-2823-9) contains supplementary material, which is available to authorized users.

Role of microbiota on lung homeostasis and diseases

The lungs, as a place of gas exchange, are continuously exposed to environmental stimuli, such as allergens, microbes, and pollutants. The development of the culture-independent technique for microbiological analysis, such as 16S rRNA sequencing, has uncovered that the lungs are not sterile and, in fact, colonized by diverse communities of microbiota. The function of intestinal microbiota in modulating mucosal homeostasis and defense has been widely studied; however, the potential function of lung microbiota in regulating immunity and homeostasis has just begun. Increasing evidence indicates the relevance of microbiota to lung homeostasis and disease. In this review, we describe the distribution and composition of microbiota in the respiratory system and discuss the potential function of lung microbiota in both health and acute/chronic lung disease. In addition, we also discuss the recent understanding of the gut-lung axis, because several studies have revealed that the immunological interaction among the gut, the lung, and the microbiota was involved in this issue.

The respiratory microbiome of HIV-infected individuals

INTRODUCTION

The respiratory tract is constantly exposed to various environmental and endogenous microbes; however, unlike other similar mucosal surfaces, there has been limited investigation of the microbiome of the respiratory tract.

AREAS COVERED

In this review, we summarize the current state of knowledge of the bacterial, fungal, and viral respiratory microbiomes during HIV infection and how the microbiome might relate to HIV-associated lung disease. Expert commentary: HIV infection is associated with alterations in the respiratory microbiome. The clinical implications of lung microbial dysbiosis are however currently unknown. Mechanistic studies are needed to establish causality between shifts in the respiratory microbiome and pulmonary complications in HIV-infected individuals.

Interactions between intestinal pathogens, enteropathy and malnutrition in developing countries

Purpose of review

This review focuses on recent data highlighting the interactions between intestinal pathogens, enteropathy and malnutrition in developing countries, which drive morbidity and mortality and hinder the long-term developmental potential of children.

Recent findings

Diarrhoea remains the second commonest cause of death in children below 5 years, and malnutrition underlies 45% of all child deaths. Even in the absence of diarrhoea, subclinical pathogen carriage and enteropathy are almost universal in developing countries. Here, we review recent studies addressing the causes and consequences of diarrhoea; emerging data on environmental influences that govern postnatal development of the gut and microbiota; current concepts of environmental enteric dysfunction; and recent intervention trials in the field. We highlight the interactions between these processes, whereby intestinal pathogens drive a cycle of gut damage, malabsorption, chronic inflammation and failed mucosal regeneration, leading to malnutrition and susceptibility to further enteric infections.

Summary

Efforts to improve child survival and long-term developmental potential need to address the overlapping and interacting effects of diarrhoea, enteropathy and malnutrition. Recent insights from human and animal studies suggest potential targets for intervention.

Lactobacillus paracasei feeding improves immune control of influenza infection in mice

Respiratory tract infections such as flu cause severe morbidity and mortality and are among the leading causes of death in children and adults worldwide. Commensal microbiota is critical for orchestrating tissue homeostasis and immunity in the intestine. Probiotics represent an interesting source of immune modulators and several clinical studies have addressed the potential beneficial effects of probiotics against respiratory infections. Therefore, we have investigated the mechanisms of protection conferred by L. paracasei CNCM I-1518 strain in a mouse model of influenza infection. Notably, local myeloid cells accumulation is generated in the lungs after seven days feeding with L. paracasei prior to viral infection. L. paracasei-fed mice showed reduced susceptibility to the influenza infection, associated with less accumulation of inflammatory cells in the lungs, faster viral clearance and general health improvement. Interestingly, Allobaculum was significantly increased in L. paracasei-fed mice 7 days after influenza infection, even if the gut microbiota composition was not altered overall. L. paracasei-purified peptidoglycan partially recapitulated the protective phenotype observed with the entire bacteria. Collectively, our results demonstrate that oral consumption of L. paracasei CNCM I-1518 modulates lung immunity was associated with an improved control of influenza infection. These results further extend the beneficial role for certain lactobacilli to alleviate the burden of respiratory tract infections.

Impact of Age, Caloric Restriction, and Influenza Infection on Mouse Gut Microbiome: An Exploratory Study of the Role of Age-Related Microbiome Changes on Influenza Responses

Immunosenescence refers to age-related declines in the capacity to respond to infections such as influenza (flu). Caloric restriction represents a known strategy to slow many aging processes, including those involving the immune system. More recently, some changes in the microbiome have been described with aging, while the gut microbiome appears to influence responses to flu vaccination and infection. With these considerations in mind, we used a well-established mouse model of flu infection to explore the impact of flu infection, aging, and caloric restriction on the gut microbiome. Young, middle-aged, and aged caloric restricted (CR) and ad lib fed (AL) mice were examined after a sublethal flu infection. All mice lost 10–20% body weight and, as expected for these early time points, losses were similar at different ages and between diet groups. Cytokine and chemokine levels were also similar with the notable exception of IL-1α, which rose more than fivefold in aged AL mouse serum, while it remained unchanged in aged CR serum. Fecal microbiome phyla abundance profiles were similar in young, middle-aged, and aged AL mice at baseline and at 4 days post flu infection, while increases in Proteobacteria were evident at 7 days post flu infection in all three age groups. CR mice, compared to AL mice in each age group, had increased abundance of Proteobacteria and Verrucomicrobia at all time points. Interestingly, principal coordinate analysis determined that diet exerts a greater effect on the microbiome than age or flu infection. Percentage body weight loss correlated with the relative abundance of Proteobacteria regardless of age, suggesting flu pathogenicity is related to Proteobacteria abundance. Further, several microbial Operational Taxonomic Units from the Bacteroidetes phyla correlated with serum chemokine/cytokines regardless of both diet and age suggesting an interplay between flu-induced systemic inflammation and gut microbiota. These exploratory studies highlight the impact of caloric restriction on fecal microbiome in both young and aged animals, as well as the many complex relationships between flu responses and gut microbiota. Thus, these preliminary studies provide the necessary groundwork to examine how gut microbiota alterations may be leveraged to influence declining immune responses with aging.

Role of the intestinal microbiota in the immunomodulation of influenza virus infection

Prevention and treatment measures against influenza virus infection remain limited, and alternative host protection strategies are badly needed. In this review, we discuss the regulatory role of intestinal microbiota in influenza infections, and present the latest evidence for strategies seeking to harness gut microbiota for the management of influenza infections.

Vγ4+γδT Cells Aggravate Severe H1N1 Influenza Virus Infection-Induced Acute Pulmonary Immunopathological Injury via Secreting Interleukin-17A

The influenza A (H1N1) pdm09 virus remains a critical global health concern and causes high levels of morbidity and mortality. Severe acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the major outcomes among severely infected patients. Our previous study found that interleukin (IL)-17A production by humans or mice infected with influenza A (H1N1) pdm09 substantially contributes to ALI and subsequent morbidity and mortality. However, the cell types responsible for IL-17A production during the early stage of severe influenza A (H1N1) pdm09 infection remained unknown. In this study, a mouse model of severe influenza A (H1N1) pdm09 infection was established. Our results show that, in the lungs of infected mice, the percentage of γδT cells, but not the percentages of CD4⁺Th and CD8⁺Tc cells, gradually increased and peaked at 3 days post-infection (dpi). Further analysis revealed that the Vγ4⁺γδT subset, but not the Vγ1⁺γδT subset, was significantly increased among the γδT cells. At 3 dpi, the virus induced significant increases in IL-17A in the bronchoalveolar lavage fluid (BALF) and serum. IL-17A was predominantly secreted by γδT cells (especially the Vγ4⁺γδT subset), but not CD4⁺Th and CD8⁺Tc cells at the early stage of infection, and IL-1β and/or IL-23 were sufficient to induce IL-17A production by γδT cells. In addition to secreting IL-17A, γδT cells secreted interferon (IFN)-γ and expressed both an activation-associated molecule, natural killer group 2, member D (NKG2D), and an apoptosis-associated molecule, FasL. Depletion of γδT cells or the Vγ4⁺γδT subset significantly rescued the virus-induced weight loss and improved the survival rate by decreasing IL-17A secretion and reducing immunopathological injury. This study demonstrated that, by secreting IL-17A, lung Vγ4⁺γδT cells, at least, in part mediated influenza A (H1N1) pdm09-induced immunopathological injury. This mechanism might serve as a promising new target for the prevention and treatment of ALI induced by influenza A (H1N1) pdm09.

The Lung Microbiome, Immunity, and the Pathogenesis of Chronic Lung Disease

The development of culture-independent techniques for microbiological analysis has uncovered the previously unappreciated complexity of the bacterial microbiome at various anatomic sites. The microbiome of the lung has relatively less bacterial biomass when compared with the lower gastrointestinal tract yet displays considerable diversity. The composition of the lung microbiome is determined by elimination, immigration, and relative growth within its communities. Chronic lung disease alters these factors. Many forms of chronic lung disease demonstrate exacerbations that drive disease progression and are poorly understood. Mounting evidence supports ways in which microbiota dysbiosis can influence host defense and immunity, and in turn may contribute to disease exacerbations. Thus, the key to understanding the pathogenesis of chronic lung disease may reside in deciphering the complex interactions between the host, pathogen, and resident microbiota during stable disease and exacerbations. In this brief review we discuss new insights into these labyrinthine relationships.

Dendritic cell expression of the signaling molecule TRAF6 is required for immune tolerance in the lung

Immune tolerance in the lung is important for preventing hypersensitivity, such as allergic asthma. Maintenance of tolerance in the lung is established by coordinated activities of poorly understood cellular and molecular mechanisms, including participation of dendritic cells (DCs). We have previously identified DC expression of the signaling molecule TRAF6 as a non-redundant requirement for the maintenance of immune tolerance in the small intestine of mice. Because mucosal tissues share similarities in how they interact with exogenous antigens, we examined the role of DC-expressed TRAF6 in the lung. As with the intestine, we found that the absence TRAF6 expression by DCs led to spontaneous generation of T_h2-associated immune responses and increased susceptibility to model antigen-induced asthma. To examine the role of commensal microbiota, mice deficient in TRAF6 in DCs were treated with broad-spectrum antibiotics and/or re-derived on a germ-free (GF) background. Interestingly, we found that antibiotics-treated specific pathogen-free, but not GF, mice showed restored immune tolerance in the absence of DC-expressed TRAF6. We further found that antibiotics mediate microbiota-independent effects on lung T cells to promote immune tolerance in the lung. This work provides both a novel tool for studying immune tolerance in the lung and an advance in our conceptual understanding of potentially common molecular mechanisms of immune tolerance in both the intestine and the lung.

Gut Microbiota Species Can Provoke both Inflammatory and Tolerogenic Immune Responses in Human Dendritic Cells Mediated by Retinoic Acid Receptor Alpha Ligation

Dendritic cells are considered as the main coordinators of both mucosal and systemic immune responses, thus playing a determining role in shaping the outcome of effector cell responses. However, it is still uncovered how primary human monocyte-derived DC (moDC) populations drive the polarization of helper T (Th) cells in the presence of commensal bacteria harboring unique immunomodulatory properties. Furthermore, the individual members of the gut microbiota have the potential to modulate the outcome of immune responses and shape the immunogenicity of differentiating moDCs via the activation of retinoic acid receptor alpha (RARα). Here, we report that moDCs are able to mediate robust Th1 and Th17 responses upon stimulation by Escherichia coli Schaedler or Morganella morganii, while the probiotic Bacillus subtilis strain limits this effect. Moreover, physiological concentrations of all-trans retinoic acid (ATRA) are able to re-program the differentiation of moDCs resulting in altered gene expression profiles of the master transcription factors RARα and interferon regulatory factor 4, and concomitantly regulate the cell surface expression levels of CD1 proteins and also the mucosa-associated CD103 integrin to different directions. It was also demonstrated that the ATRA-conditioned moDCs exhibited enhanced pro-inflammatory cytokine secretion while reduced their co-stimulatory and antigen-presenting capacity thus reducing Th1 and presenting undetectable Th17 type responses against the tested microbiota strains. Importantly, these regulatory circuits could be prevented by the selective inhibition of RARα functionality. These results altogether demonstrate that selected commensal bacterial strains are able to drive strong effector immune responses by moDCs, while in the presence of ATRA, they support the development of both tolerogenic and inflammatory moDC in a RARα-dependent manner.

Interplay of Regulatory T Cell and Th17 Cells during Infectious Diseases in Humans and Animals

It is now clear that the outcome of an inflammatory process caused by infections depends on the balance of responses by several components of the immune system. Of particular relevance is the interplay between regulatory T cells (Tregs) and CD4⁺ T cells that produce IL-17 (Th17 cells) during immunoinflammatory events. In addition to discussing studies done in mice to highlight some unresolved issues in the biology of these cells, we emphasize the need to include outbred animals and humans in analyses. Achieving a balance between Treg and Th17 cells responses represents a powerful approach to control events during immunity and immunopathology.

CD161+ Tconv and CD161+ Treg Share a Transcriptional and Functional Phenotype despite Limited Overlap in TCRβ Repertoire

Human regulatory T cells (Treg) are important in immune regulation, but can also show plasticity in specific settings. CD161 is a lectin-like receptor and its expression identifies an effector-like Treg population. Here, we determined how CD161⁺ Treg relate to CD161⁺ conventional T cells (Tconv). Transcriptional profiling identified a shared transcriptional signature between CD161⁺ Tconv and CD161⁺ Treg, which is associated with T helper (Th)1 and Th17 cells, and tissue homing, including high expression of gut-homing receptors. Upon retinoic acid (RA) exposure, CD161⁺ T cells were more enriched for CCR9⁺ and integrin α4⁺β7⁺ cells than CD161^- T cells. In addition, CD161⁺ Tconv and CD161⁺ Treg were enriched at the inflamed site in autoimmune arthritis, and both CD161⁺ and CD161^- Treg from the inflamed site were suppressive in vitro. CD161⁺ T cells from the site of autoimmune arthritis showed a diminished gut-homing phenotype and blunted response to RA suggesting prior imprinting by RA in the gut or at peripheral sites rather than during synovial inflammation. TCRβ repertoires of CD161⁺ and CD161^- Tconv and Treg from blood showed limited overlap whereas there was clear overlap between CD161⁺ and CD161^- Tconv, and CD161⁺ and CD161^- Treg from the inflamed site suggesting that the inflamed environment may alter CD161 levels, potentially contributing to disease pathogenesis.

Role of the microbiome in swine respiratory disease

Microbiome is a term used to describe the community of microorganisms that live on the skin and mucosal surfaces of animals. The gastrointestinal microbiome is essential for proper nutrition and immunity. How the gastrointestinal microbiome impacts primary respiratory or systemic infections is an emerging area of study. Porcine reproductive and respiratory syndrome (PRRS) is caused by a systemic virus infection with primary lung pathology and continues to be the most costly disease of swine worldwide. Recent studies have demonstrated that improved outcome after experimental infection with PRRS virus and porcine circovirus type 2 (PCV2) is associated with increased fecal microbiome diversity and the presence of non-pathogenic Escherichia coli. In this review, we will discuss the factors that influence microbiome development in swine, associations of the microbiome with growth and immunity during infection with respiratory pathogens, and the role of the microbiome in PRRS. Taken together, modulation of the microbiome may be an alternative tool in the control of PRRS due to its intricate role in digestion of nutrients, systemic immunity, and response to pulmonary infections.

Clinical differences of influenza subspecies among hospitalized children

AIM

Clinical findings, mortality, and morbidity rates differ among influenza subspecies. Awareness of these differences will lead physicians to choose the proper diagnostic and therapeutic strategies and to foresee possible complications. The aim of this study was to evaluate the clinical differences of influenza subspecies among hospitalized children.

MATERIAL AND METHODS

Hospitalized children with proven influenza infection by polymerase chain reaction on nasopharyngeal swab specimens in our clinic, between December 2013 and March 2016, were enrolled. These children were divided into 3 groups as Influenza A/H1N1 (n=42), Influenza A/H3N2 (n=23), and Influenza B (n=35).

RESULTS

The median age of the children was 51.5 months (range, 3-204 months). The most common presenting symptoms were fever (n=83), cough (n=58), and difficulty in breathing (n=25). The most common non-respiratory findings were lymphadenopathy (n=18) and gastrointestinal system involvement (n=17). Sixty-two percent of the patients (n=62) had chronic diseases. H1N1 and H3N2 were significantly more common among patients with chronic neurologic disorders and renal failure, respectively. Leukopenia (n=32) and thrombocytopenia (n=22) were the most common pathologic laboratory findings. Neutropenia, elevated CRP levels, and antibiotic use were significantly more common among patients with H1N1 infection. Seven patients were transferred to the intensive care unit with diagnoses of acute respiratory distress syndrome (n=4), encephalitis (n=2), and bronchiolitis (n=1). Two patients with chronic diseases and H1N1 infection died secondary to acute respiratory distress syndrome.

CONCLUSIONS

Influenza A/H1N1 infection represented more severe clinical disease.

Infection and antibiotic use in infancy and risk of childhood obesity: a longitudinal birth cohort study

BACKGROUND

Data from previous studies have suggested a possible association between antibiotic use in infancy and risk of childhood obesity, with implications for health-care delivery and obesity prevention strategies. However, whether the observed association was due to antibiotic use or underlying infection, or both, is unclear. We aimed to disentangle the effect of antibiotic use in infancy from that of underlying infection on the risk of childhood obesity.

METHODS

In this longitudinal birth cohort study, we included infants in the Kaiser Permanente Northern California population born between Jan 1, 1997, and March 31, 2013. We used electronic medical records to ascertain data for antibiotic use, infection diagnosis, and anthropometric measurements (and thus BMI and obesity status) from birth up to age 18 years. We used standard mixed-effects logistic regression for repeated measurements to analyse multiple BMI measurements per child (median five measurements) and to obtain odds ratios (ORs) and 95% CIs for obesity risk. We also did a substudy in 547 same-sex twin pairs with discordant exposure status to substantiate our findings.

FINDINGS

260 556 individuals were included in our analysis. After controlling for maternal age, race or ethnic origin, pre-pregnancy BMI, preterm delivery, low birthweight, maternal antibiotic use, and infection during pregnancy, infection without antibiotic use in infancy was associated with an increased risk of childhood obesity compared with controls without infection (OR 1·25, 95% CI 1·20-1·29). A clear dose-response relation was seen between infection episodes and risk of childhood obesity (p_trend <0·0001). By contrast, compared with infants with untreated infection, antibiotic use during infancy was not associated with risk of childhood obesity (1·01, 0·98-1·04). Neither broad-spectrum nor narrow-spectrum antibiotics were associated with risk of childhood obesity. These findings were supported by the results of the twin set analysis.

INTERPRETATION

Infection, but not antibiotic use, during infancy is associated with risk of childhood obesity. This finding will need to be replicated in future studies. Although our results do not rule out a potential effect of antibiotics on microbiome composition and the use of antibiotics should always be judicious, they suggest that treatment of common infections with antibiotics in infancy is unlikely to be a main contributor to childhood obesity.

FUNDING

Kaiser Permanente Center for Effectiveness & Safety Research.

Host-microbiome interactions in acute and chronic respiratory infections

Respiratory infection is a leading cause of global morbidity and mortality. Understanding the factors that influence risk and outcome of these infections is essential to improving care. We increasingly understand that interactions between the microbial residents of our mucosal surfaces and host regulatory systems is fundamental to shaping local and systemic immunity. These mechanisms are most well defined in the gastrointestinal tract, however analogous systems also occur in the airways. Moreover, we now appreciate that the host-microbiota interactions at a given mucosal surface influence systemic host processes, in turn, affecting the course of infection at other anatomical sites. This review discusses the mechanisms by which the respiratory microbiome influences acute and chronic airway disease and examines the contribution of cross-talk between the gastrointestinal and respiratory compartments to microbe-mucosa interactions.

Respiratory Influenza Virus Infection Induces Memory-like Liver NK Cells in Mice

Although NK cells are classified as innate immune cells, recent studies have demonstrated the transformation of NK cells into long-lived memory cells that contribute to secondary immune responses in certain mouse models. However, whether NK cells mount an Ag-specific memory response to acute influenza virus infection has not yet been examined. Here, we show that, consistent with previous studies, lung NK cells play an important role in controlling viral proliferation after primary influenza virus infection. However, although lung NK cells display a memory phenotype at the late stage of infection, these cells do not protect mice against secondary influenza virus infection. Interestingly, liver NK cells from influenza virus-infected mice possess a memory phenotype and protect mice against secondary influenza virus infection. Memory-like liver NK cells display a CD49a⁺DX5^- phenotype, and the adoptive transfer of purified liver CD49a⁺DX5^- NK cells into naive mice followed by viral infection results in protective immunity and decreased viral titer. Moreover, we demonstrate that primary inactivated influenza virus induces memory NK cells residing in the liver of Rag1^-/- mice. Collectively, these data suggest that liver CD49a⁺DX5^- NK cells remember encountered Ag from influenza virus after primary infection and are more protective upon subsequent infection.

Protective effects of organic acid component from Taraxacum mongolicum Hand.-Mazz. against LPS-induced inflammation: Regulating the TLR4/IKK/NF-κB signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

TMHM is a type of Chinese medicine commonly used in medical practice and has multiple functions, including clearing heat, detoxification, reducing swelling, and tumor therapy. Previous research has demonstrated that the OAC of TMHM (TMHM-OAC) displays advantageous therapeutic action against respiratory inflammation. However, the effect of TMHM-OAC on inflammatory injury and its anti-inflammatory role requires further clarification.

MATERIALS AND METHODS

An in vitro inflammation damage model was employed using NHBE cells and 100ng/ml of (LPS). HPLC-DAD was conducted to analyze the components of TMHM-OAC. An ELISA was conducted to determine IL-1β, IL-6, TNF-α, and NO expression. An MTT assay was conducted to determine the cytotoxicity of TMHM-OAC. The levels of IL-1β, IL-6, TNF-α, caspase-3, caspase-8, iNOS, TLR4p-nuclear factor kappa-B kinase (p-IκκB), and p-NF-κB p65 in cellular protein, as well as the mRNA levels, were determined using WB, IF testing, and Q-PCR.

RESULTS

TMHM-OAC significantly reduced LPS-induced NHBE cell inflammation, which was reflected in the reduced expression of relevant cytokines such as TNF-α, IL-1β, IL-6 and NO, caspase-3, and caspase-8. In addition, this component suppressed TLR4, p-IKKβ, and p-NF-κB p65 levels in both mRNA and cellular protein.

CONCLUSION

TMHM-OAC can reduce LPS-induced inflammation in NHBE cells and this function could be linked to the regulation of the TLR4/IKK/NF-kB pathway.

The microbiome-metabolome crosstalk in the pathogenesis of respiratory fungal diseases

Filamentous fungi of the genus Aspergillus are responsible for several superficial and invasive infections and allergic syndromes. The risk of infection and its clinical outcome vary significantly even among patients with similar predisposing clinical factors and pathogen exposure. There is increasing evidence that the individual microbiome supervises the outcome of the host-fungus interaction by influencing mechanisms of immune regulation, inflammation, metabolism, and other physiological processes. Microbiome-mediated mechanisms of resistance allow therefore the control of fungal colonization, preventing the onset of overt disease, particularly in patients with underlying immune dysfunction. Here, we review this emerging area of research and discuss the contribution of the microbiota (and its dysbiosis), including its immunoregulatory properties and relationship with the metabolic activity of commensals, to respiratory fungal diseases. Finally, we highlight possible strategies aimed at decoding the microbiome-metabolome dialog and at its exploitation toward personalized medical interventions in patients at high risk of infection.

[Effect of respiratory syncytial virus-related pulmonary infection on endogenous metabolites in large intestinal mucosa in mice]

OBJECTIVE

To investigate the effect of respiratory syncytial virus (RSV)-related pulmonary infection on endogenous metabolites in large intestinal mucosa in BALB/c mice using metabolomics technology based on gas chromatography-mass spectrometry (GC-MS).

METHODS

Mice were randomly divided into a control group and a RSV pneumonia model group (n=16 each). The mouse model of RSV pneumonia was established using intranasal RSV infection (100×TCID₅₀, 50 μL/mouse, once a day). After 7 days of intranasal RSV infection, the mice were sacrificed and GC-MS was used to identify endogenous metabolites and measure the changes in their relative content in colon tissue. SMCA-P12.0 software was used to perform principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) for endogenous metabolites in colon tissue. The differentially expressed metabolites in colon tissue were imported into the metabolic pathway platform Metaboanalyst to analyze related metabolic pathways.

RESULTS

PCA and OPLS-DA showed significant differences between the control and RSV pneumonia model groups. A total of 32 metabolites were identified in the colon tissue of the mice with RSV pneumonia. The RSV pneumonia model group had significant increases in the content of leucine, isoleucine, glycine, alanine, arachidonic acid, and lactic acid, which were related to the valine, leucine, isoleucine, arachidonic acid, and pyruvic acid metabolic pathways.

CONCLUSIONS

RSV pneumonia might cause metabolic disorders in the large intestinal tissue in mice.

Emerging pathogenic links between microbiota and the gut-lung axis

The microbiota is vital for the development of the immune system and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the respiratory tract and the gut have recently been linked to alterations in immune responses and to disease development in the lungs. In this Opinion article, we review the microbial species that are usually found in healthy gastrointestinal and respiratory tracts, their dysbiosis in disease and interactions with the gut-lung axis. Although the gut-lung axis is only beginning to be understood, emerging evidence indicates that there is potential for manipulation of the gut microbiota in the treatment of lung diseases.

The Gut-Lung Axis in Respiratory Disease

Host-microorganism interactions shape local cell functionality, immune responses, and can influence disease development. Evidence indicates that the impact of host-microbe interactions reaches far beyond the local environment, thus influencing responses in peripheral tissues. There is a vital cross-talk between the mucosal tissues of our body, as exemplified by intestinal complications during respiratory disease and vice versa. Although, mechanistically, this phenomenon remains poorly defined, the existence of the gut-lung axis and its implications in both health and disease could be profoundly important for both disease etiology and treatment. In this review, we highlight how changes in the intestinal microenvironment, with a particular focus on the intestinal microbiota, impact upon respiratory disease.

Viral Infection of the Central Nervous System Exacerbates Interleukin-10 Receptor Deficiency-Mediated Colitis in SJL Mice

Theiler´s murine encephalomyelitis virus (TMEV)-infection is a widely used animal model for studying demyelinating disorders, including multiple sclerosis (MS). The immunosuppressive cytokine Interleukin (IL)-10 counteracts hyperactive immune responses and critically controls immune homeostasis in infectious and autoimmune disorders. In order to investigate the effect of signaling via Interleukin-10 receptor (IL-10R) in infectious neurological diseases, TMEV-infected SJL mice were treated with IL-10R blocking antibody (Ab) in the acute and chronic phase of the disease. The findings demonstrate that (i) Ab-mediated IL-10 neutralization leads to progressive colitis with a reduction in Foxp3+ regulatory T cells and increased numbers of CD8+CD44+ memory T cells as well as activated CD4+CD69+ and CD8+CD69+ T cells in uninfected mice. (ii) Concurrent acute TMEV-infection worsened enteric disease-mediated by IL-10R neutralization. Virus-triggered effects were associated with an enhanced activation of CD4+ T helper cells and CD8+ cytotoxic T lymphocytes and augmented cytokine expression. By contrast, (iii) IL-10R neutralization during chronic TMEV-infection was not associated with enhanced peripheral immunopathology but an increased CD3+ T cell influx in the spinal cord. IL-10R neutralization causes a breakdown in peripheral immune tolerance in genetically predisposed mice, which leads to immune-mediated colitis, resembling inflammatory bowel disease. Hyperactive immune state following IL-10R blockade is enhanced by central nervous system-restricted viral infection in a disease phase-dependent manner.

The Fecal Microbiota Profile and Bronchiolitis in Infants

BACKGROUND

Little is known about the association of gut microbiota, a potentially modifiable factor, with bronchiolitis in infants. We aimed to determine the association of fecal microbiota with bronchiolitis in infants.

METHODS

We conducted a case-control study. As a part of multicenter prospective study, we collected stool samples from 40 infants hospitalized with bronchiolitis. We concurrently enrolled 115 age-matched healthy controls. By applying 16S rRNA gene sequencing and an unbiased clustering approach to these 155 fecal samples, we identified microbiota profiles and determined the association of microbiota profiles with likelihood of bronchiolitis.

RESULTS

Overall, the median age was 3 months, 55% were male, and 54% were non-Hispanic white. Unbiased clustering of fecal microbiota identified 4 distinct profiles: Escherichia-dominant profile (30%), Bifidobacterium-dominant profile (21%), Enterobacter/Veillonella-dominant profile (22%), and Bacteroides-dominant profile (28%). The proportion of bronchiolitis was lowest in infants with the Enterobacter/Veillonella-dominant profile (15%) and highest in the Bacteroides-dominant profile (44%), corresponding to an odds ratio of 4.59 (95% confidence interval, 1.58-15.5; P = .008). In the multivariable model, the significant association between the Bacteroides-dominant profile and a greater likelihood of bronchiolitis persisted (odds ratio for comparison with the Enterobacter/Veillonella-dominant profile, 4.24; 95% confidence interval, 1.56-12.0; P = .005). In contrast, the likelihood of bronchiolitis in infants with the Escherichia-dominant or Bifidobacterium-dominant profile was not significantly different compared with those with the Enterobacter/Veillonella-dominant profile.

CONCLUSIONS

In this case-control study, we identified 4 distinct fecal microbiota profiles in infants. The Bacteroides-dominant profile was associated with a higher likelihood of bronchiolitis.

Influenza Virus Affects Intestinal Microbiota and Secondary Salmonella Infection in the Gut through Type I Interferons

Human influenza viruses replicate almost exclusively in the respiratory tract, yet infected individuals may also develop gastrointestinal symptoms, such as vomiting and diarrhea. However, the molecular mechanisms remain incompletely defined. Using an influenza mouse model, we found that influenza pulmonary infection can significantly alter the intestinal microbiota profile through a mechanism dependent on type I interferons (IFN-Is). Notably, influenza-induced IFN-Is produced in the lungs promote the depletion of obligate anaerobic bacteria and the enrichment of Proteobacteria in the gut, leading to a “dysbiotic” microenvironment. Additionally, we provide evidence that IFN-Is induced in the lungs during influenza pulmonary infection inhibit the antimicrobial and inflammatory responses in the gut during Salmonella-induced colitis, further enhancing Salmonella intestinal colonization and systemic dissemination. Thus, our studies demonstrate a systemic role for IFN-Is in regulating the host immune response in the gut during Salmonella-induced colitis and in altering the intestinal microbial balance after influenza infection.

Influenza is a respiratory illness. Symptoms of flu include fever, headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose, and muscle aches. Some people, especially children, can have additional gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. In humans, there is no evidence that the influenza virus replicates in the intestine. Using an influenza mouse model, we found that influenza infection alters the intestinal microbial community through a mechanism dependent on type I interferons induced in the pulmonary tract. Futhermore, we demonstrate that influenza-induced type I interferons increase the host susceptibility to Salmonella intestinal colonization and dissemination during secondary Salmonella-induced colitis through suppression of host intestinal immunity.

Use of Metatranscriptomics in Microbiome Research

The human intestinal microbiome is a microbial ecosystem that expresses as many as 100 times more genes than the human host, thereby constituting an important component of the human holobiome, which contributes to multiple health and disease processes. As most commensal species are difficult or impossible to culture, genomic characterization of microbiome composition and function, under various environmental conditions, comprises a central tool in understanding its roles in health and disease. The first decade of microbiome research was mainly characterized by usage of DNA sequencing-based 16S rDNA and shotgun metagenome sequencing, allowing for the elucidation of microbial composition and genome structure. Technological advances in RNA-seq have recently provided us with an ability to gain insight into the genes that are actively expressed in complex bacterial communities, enabling the elucidation of the functional changes that dictate the microbiome functions at given contexts, its interactions with the host, and functional alterations that accompany the conversion of a healthy microbiome toward a disease-driving configuration. Here, we highlight some of the key metatranscriptomics strategies that are implemented to determine microbiota gene expression and its regulation and discuss the advantages and potential challenges associated with these approaches.

Local and Long-Distance Calling: Conversations between the Gut Microbiota and Intra- and Extra-Gastrointestinal Tract Infections

Preservation of health from infectious diseases depends upon both mucosal and systemic immunity via the collaborative effort of innate and adaptive immune responses. The proficiency of host immunity stems from robust defense mechanisms—physical barriers and specialized immune cells—and a failure of these mechanisms leads to pathology. Intriguingly, immunocompetence to pathogens can be shaped by the gut microbiome as recent publications highlight a dynamic interplay between the gut microbiome and host susceptibility to infection. Modulation of host immunity to enteric pathogens has long been studied where gut bacteria shape multiple facts of both innate and adaptive immunity. Conversely, the impact of gut commensals on host immunity to extra-gastrointestinal (GI) tract infections has only recently been recognized. In this context, the gut microbiome can augment host immunity to extra-GI tract bacterial, viral, and parasitic pathogens. This review explores the research that affords insight into the role of the gut microbiome in various infectious diseases, with a particular emphasis on extra-GI tract infections. A better understanding of the link between the gut microbiome and infectious disease will be critical for improving global health in the years ahead.

Norovirus in symptomatic and asymptomatic individuals: cytokines and viral shedding

Noroviruses (NoV) are the most common cause of epidemic gastroenteritis world-wide. NoV infections are often asymptomatic, although individuals still shed large amounts of NoV in their stool. Understanding the differences between asymptomatic and symptomatic individuals would help in elucidating mechanisms of NoV pathogenesis. Our goal was to compare the serum cytokine responses and faecal viral RNA titres of asymptomatic and symptomatic NoV-infected individuals. We tested serum samples from infected subjects (n = 26; 19 symptomatic, seven asymptomatic) from two human challenge studies of GI.1 NoV for 16 cytokines. Samples from prechallenge and days 1-4 post-challenge were tested for these cytokines. Cytokine levels were compared to stool NoV RNA titres quantified previously by reverse transcription-polymerase chain reaction (RT-qPCR). While both symptomatic and asymptomatic groups had similar patterns of cytokine responses, the symptomatic group generally exhibited a greater elevation of T helper type 1 (Th1) and Th2 cytokines and IL-8 post-challenge compared to the asymptomatic group (all P < 0·01). Daily viral RNA titre was associated positively with daily IL-6 concentration and negatively with daily IL-12p40 concentration (all P < 0·05). Symptoms were not associated significantly with daily viral RNA titre, duration of viral shedding or cumulative shedding. Symptomatic individuals, compared to asymptomatic, have greater immune system activation, as measured by serum cytokines, but they do not have greater viral burden, as measured by titre and shedding, suggesting that symptoms may be immune-mediated in NoV infection.

Commensal Microbiome Promotes Resistance to Local and Systemic Infections

Objective:

In this review, to illustrate the resistance mechanism for pathogen insult, we discussed the role of the intestinal microbiome in promoting resistance to local gastrointestinal tract infections and to respiratory tract infections.

Data Sources:

The review was based on data obtained from the published research articles.

Study Selection:

A total of 49 original articles were selected in accordance with our main objective to illustrate the resistance mechanism(s) by which commensal microbiota can contribute to host defense against local and systemic infections.

Results:

Diverse microorganisms colonize human environmentally exposed surfaces such as skin, respiratory tract, and gastrointestinal tract. Co-evolution has resulted in these microbes with extensive and diverse impacts on multiple aspects of host biological functions. During the last decade, high-throughput sequencing technology developed has been applied to study commensal microbiota and their impact on host biological functions. By using pathogen recognition receptors pathway and nucleotide binding oligomerization domain-like receptors pathway, the commensal microbiome promotes resistance to local and systemic infections, respectively. To protect against the local infections, the microbiome functions contain the following: The competing for sites of colonization, direct production of inhibition molecules or depletion of nutrients needed for pathogens, and priming immune defenses against pathogen insult. At the same time, with the purpose to maintain homeostasis, the commensal bacteria can program systemic signals toward not only local tissue but also distal tissue to modify their function for infections accordingly.

Conclusions:

Commensal bacteria play an essential role in protecting against infections, shaping and regulating immune responses, and maintaining host immune homeostasis.

Chemokine receptor patterns in lymphocytes mirror metastatic spreading in melanoma

Melanoma prognosis is dictated by tumor-infiltrating lymphocytes, the migratory and functional behavior of which is guided by chemokine or cytokine gradients. Here, we retrospectively analyzed the expression patterns of 9 homing receptors (CCR/CXCR) in naive and memory CD4+ and CD8+ T lymphocytes in 57 patients with metastatic melanoma (MMel) with various sites of metastases to evaluate whether T cell CCR/CXCR expression correlates with intratumoral accumulation, metastatic progression, and/or overall survival (OS). Homing receptor expression on lymphocytes strongly correlated with MMel dissemination. Loss of CCR6 or CXCR3, but not cutaneous lymphocyte antigen (CLA), on circulating T cell subsets was associated with skin or lymph node metastases, loss of CXCR4, CXCR5, and CCR9 corresponded with lung involvement, and a rise in CCR10 or CD103 was associated with widespread dissemination. High frequencies of CD8+CCR9+ naive T cells correlated with prolonged OS, while neutralizing the CCR9/CCL25 axis in mice stimulated tumor progression. The expansion of CLA-expressing effector memory CD8+ T cells in response to a single administration of CTLA4 blockade predicted disease control at 3 months in 47 patients with MMel. Thus, specific CCR/CXCR expression patterns on circulating T lymphocytes may guide potential diagnostic and therapeutic approaches.

IL-17A Promotes Pulmonary B-1a Cell Differentiation via Induction of Blimp-1 Expression during Influenza Virus Infection

B-1 cells play a critical role in early protection during influenza infections by producing natural IgM antibodies. However, the underlying mechanisms involved in regulating this process are largely unknown. Here we found that during influenza infection pleural cavity B-1a cells rapidly infiltrated lungs, where they underwent plasmacytic differentiation with enhanced IgM production. This process was promoted by IL-17A signaling via induction of Blimp-1 expression and NF-κB activation in B-1a cells. Deficiency of IL-17A led to severely impaired B-1a-derived antibody production in the respiratory tract, resulting in a deficiency in viral clearance. Transfer of B-1a-derived natural antibodies rescued Il17a^-/- mice from otherwise lethal infections. Together, we identify a critical function of IL-17A in promoting the plasmacytic differentiation of B-1a cells. Our findings provide new insights into the mechanisms underlying the regulation of pulmonary B-1a cell response against influenza infection.

Influenza infection is highly localized in respiratory tract where immune response is triggered to provide protection from primary infection. Although natural IgM antibodies produced by B-1a cells have long been recognized as first-line protection against influenza, it remains unclear whether B-1a cell response occurs in the lung and what molecular mechanisms regulate this process. We show that airway exposure to influenza causes migration of B-1a cells to lungs for further differentiation into plasma cells with enhanced production of protective IgM antibodies. IL-17A critically regulates this process by driving differentiation of B-1a cells to high-rate IgM producing plasma cells in situ. Thus, IL-17A is a key factor in the local inflammatory milieu that modulates early humoral immunity afforded by B-1a cells.

Systems Vaccinology: Applications, Trends, and Perspectives

The strategies employed in vaccinology have improved since the seminal work of Edward Jenner in the eighteenth century. Stimulated by failure to develop vaccines for cancers and chronic infectious diseases as well as an emergence of a multitude of new technologies not available earlier, vaccinology has moved from a largely experimental art to a new phase of innovation. Currently, immune reactions can be predicted and modeled before they occur and formulations can be optimized in advance for genetic background, age, sex, lifestyle, environmental factors, and microbiome. A multitude of scientific insights and technological advancements have led us to this current status, yet possibly none of the recent developments is individually more promising to achieve these goals than the interdisciplinary science of systems vaccinology. This review summarizes current trends and applications of systems vaccinology, including technically tangible areas of vaccine and immunology research which allow the transformative process into a truly broad understanding of vaccines, thereby effectively modeling interaction of vaccines with health and disease. It is becoming clear that a multitude of factors have to be considered to understand inter-patient variability of vaccine responses including those characterized from the interfaces between the immune system, microbiome, metabolome, and the nervous system.

Prevalence of gastrointestinal symptoms in patients with influenza, clinical significance, and pathophysiology of human influenza viruses in faecal samples: what do we know?

This review provides for the first time an assessment of the current understanding about the occurrence and the clinical significance of gastrointestinal (GI) symptoms in influenza patients, and their correlation with the presence of human influenza viruses in stools of patients with confirmed influenza virus infection. Studies exploring how human influenza viruses spread to the patient’s GI tract after a primary respiratory infection have been summarized. We conducted a systematic search of published peer-reviewed literature up to June 2015 with regard to the above-mentioned aspects, focusing on human influenza viruses (A(H1N1), A(H1N1)pdm09, A(H3N2), and B). Forty-four studies were included in this systematic review and meta-analysis. The pooled prevalence of any digestive symptoms ranged from 30.9 % (95 % CI, 9.8 to 57.5; I² = 97.5 %) for A(H1N1)pdm09 to 2.8 % (95 % CI, 0.6 to 6.5; I² = 75.4 %) for A(H1N1). The pooled prevalence of influenza viruses in stool was 20.6 % (95 % CI, 8.9 to 35.5; I² = 96.8 %), but their correlation with GI symptoms has rarely been explored. The presence of viral RNA in stools because of haematogenous dissemination to organs via infected lymphocytes is likely, but the potential to cause direct intestinal infection and faecal–oral transmission warrants further investigation. This review highlights the gaps in our knowledge, and the high degree of uncertainty about the prevalence and significance of GI symptoms in patients with influenza and their correlation with viral RNA positivity in stool because of the high level of heterogeneity among studies.