No Impairment in Host Defense against Streptococcus pneumoniae in Obese CPEfat/fat Mice

In the US and globally, dramatic increases in the prevalence of adult and childhood obesity have been reported during the last 30 years. In addition to cardiovascular disease, type II diabetes, and liver disease, obesity has recently been recognized as an important risk factor for influenza pneumonia. During the influenza pandemic of 2009, obese individuals experienced a greater severity of illness from the H1N1 virus. In addition, obese mice have also been shown to exhibit increased lethality and aberrant pulmonary inflammatory responses following influenza infection. In contrast to influenza, the impact of obesity on bacterial pneumonia in human patients is controversial. In this report, we compared the responses of lean WT and obese CPE^fat/fat mice following an intratracheal infection with Streptococcus pneumoniae, the leading cause of community-acquired pneumonia. At 16 weeks of age, CPE^fat/fat mice develop severe obesity, hyperglycemia, elevated serum triglycerides and leptin, and increased blood neutrophil counts. There were no differences between lean WT and obese CPE^fat/fat mice in survival or lung and spleen bacterial burdens following intratracheal infection with S. pneumoniae. Besides a modest increase in TNF-α levels and increased peripheral blood neutrophil counts in CPE^fat/fat mice, there were not differences in lung or serum cytokines after infection. These results suggest that obesity, accompanied by hyperglycemia and modestly elevated triglycerides, at least in the case of CPE^fat/fat mice, does not impair innate immunity against pneumococcal pneumonia.     

Impaired Clearance of Influenza A Virus in Obese,Leptin Receptor Deficient Mice Is Independent of Leptin Signaling in the Lung Epithelium and Macrophages

Rationale

During the recent H1N1 outbreak, obese patients had worsened lung injury and increased mortality. We used a murine model of influenza A pneumonia to test the hypothesis that leptin receptor deficiency might explain the enhanced mortality in obese patients.

Methods

We infected wild-type, obese mice globally deficient in the leptin receptor (db/db) and non-obese mice with tissue specific deletion of the leptin receptor in the lung epithelium (SPC-Cre/LepR^fl/fl) or macrophages and alveolar type II cells (LysM-Cre/Lepr^fl/fl) with influenza A virus (A/WSN/33 [H1N1]) (500 and 1500 pfu/mouse) and measured mortality, viral clearance and several markers of lung injury severity.

Results

The clearance of influenza A virus from the lungs of mice was impaired in obese mice globally deficient in the leptin receptor (db/db) compared to normal weight wild-type mice. In contrast, non-obese, SP-C-Cre^+/+/LepR^fl/fl and LysM-Cre^+/+/LepR^fl/fl had improved viral clearance after influenza A infection. In obese mice, mortality was increased compared with wild-type mice, while the SP-C-Cre^+/+/LepR^fl/fl and LysM-Cre^+/+/LepR^{fl /fl} mice exhibited improved survival.

Conclusions

Global loss of the leptin receptor results in reduced viral clearance and worse outcomes following influenza A infection. These findings are not the result of the loss of leptin signaling in lung epithelial cells or macrophages. Our results suggest that factors associated with obesity or with leptin signaling in non-myeloid populations such as natural killer and T cells may be associated with worsened outcomes following influenza A infection.     

Differential effect of prior influenza infection on alveolar macrophage phagocytosis of Staphylococcus aureus and Escherichia coli: involvement of interferon-gamma production

The influenza A virus is one of the main causes of respiratory infection. Although influenza virus infection alone can result in pneumonia, secondary bacterial infection combined with the virus is the major cause of morbidity and mortality. Interestingly, while influenza infection increases susceptibility to some bacteria, including Streptococcus pneumoniae, Staphylococcus aureus (S. aureus), and Haemophilus influenzae, other bacteria such as Escherichia coli (E. coli) and Klebsiella pneumoniae are not associated with influenza infection. The reason for this discrepancy is not known. In this study, it was found that prior influenza virus infection inhibits murine alveolar macrophage phagocytosis of S. aureus but not of E. coli. Here, the mechanism for this inhibition is elucidated: prior influenza virus infection strongly increases interferon gamma (IFN-γ) production. Furthermore, it was shown that IFN-γ differentially affects alveolar macrophage phagocytosis of S. aureus and E. coli. The findings of the present study explain how influenza virus infection increases susceptibility to some bacteria, such as S. aureus, but not others, and provides evidence that IFN-γ might be a promising target for protecting the human population from secondary bacterial infection by influenza.     

The critical role of Notch ligand Delta-like 1 in the pathogenesis of influenza A virus (H1N1) infection

Influenza A viral infections have been identified as the etiologic agents for historic pandemics, and contribute to the annual mortality associated with acute viral pneumonia. While both innate and acquired immunity are important in combating influenza virus infection, the mechanism connecting these arms of the immune system remains unknown. Recent data have indicated that the Notch system is an important bridge between antigen-presenting cells (APCs) and T cell communication circuits and plays a central role in driving the immune system to overcome disease. In the present study, we examine the role of Notch signaling during influenza H1N1 virus infection, focusing on APCs. We demonstrate here that macrophages, but not dendritic cells (DCs), increased Notch ligand Delta-like 1 (Dll1) expression following influenza virus challenge. Dll1 expression on macrophages was dependent on retinoic acid-inducible gene-I (RIG-I) induced type-I IFN pathway, and not on the TLR3-TRIF pathway. We also found that IFNα-Receptor knockout mice failed to induce Dll1 expression on lung macrophages and had enhanced mortality during influenza virus infection. Our results further showed that specific neutralization of Dll1 during influenza virus challenge induced higher mortality, impaired viral clearance, and decreased levels of IFN-γ. In addition, we blocked Notch signaling by using γ-secretase inhibitor (GSI), a Notch signaling inhibitor. Intranasal administration of GSI during influenza infection also led to higher mortality, and higher virus load with excessive inflammation and an impaired production of IFN-γ in lungs. Moreover, Dll1 expression on macrophages specifically regulates IFN-γ levels from CD4(+)and CD8(+)T cells, which are important for anti-viral immunity. Together, the results of this study show that Dll1 positively influences the development of anti-viral immunity, and may provide mechanistic approaches for modifying and controlling the immune response against influenza H1N1 virus infection.     

Exploring cell tropism as a possible contributor to influenza infection severity

Several mechanisms have been proposed to account for the marked increase in severity of human infections with avian compared to human influenza strains, including increased cytokine expression, poor immune response, and differences in target cell receptor affinity. Here, the potential effect of target cell tropism on disease severity is studied using a mathematical model for in-host influenza viral infection in a cell population consisting of two different cell types. The two cell types differ only in their susceptibility to infection and rate of virus production. We show the existence of a parameter regime which is characterized by high viral loads sustained long after the onset of infection. This finding suggests that differences in cell tropism between influenza strains could be sufficient to cause significant differences in viral titer profiles, similar to those observed in infections with certain strains of influenza A virus. The two target cell mathematical model offers good agreement with experimental data from severe influenza infections, as does the usual, single target cell model albeit with biologically unrealistic parameters. Both models predict that while neuraminidase inhibitors and adamantanes are only effective when administered early to treat an uncomplicated seasonal infection, they can be effective against more severe influenza infections even when administered late.     

Epigenetic changes mediated by microRNA miR29 activate cyclooxygenase 2 and lambda-1 interferon production during viral infection

Lambda-1 interferon (IFN-λ1) and cyclooxygenase-2 (COX-2) were reported to play an important role in host antiviral defense. However, the mechanism by which IFN-λ1 and COX2 are activated and modulated during viral infection remains unclear. In this study, we found that expression of both circulating IFN-λ1 and COX2-derived prostaglandin E2 (PGE2) was coordinately elevated in a cohort of influenza patients compared to healthy individuals. Expression of IFN-λ1 was blocked by a selective COX2 inhibitor during influenza A virus infection in A549 human lung epithelial cells but enhanced by overexpression of COX2, indicating that the production of IFN-λ1 is COX2 dependent. COX2 was able to increase IFN-λ1 expression by promoting NF-κB binding to the enhancer in the IFN-λ1 promoter. We found that epigenetic changes activate COX2 expression and PGE2 accumulation during viral infection. The expression of DNA methyltransferase 3a (DNMT3a) and DNMT3b, but not that of DNMT1, was downregulated following influenza A virus infection in both A549 cells and peripheral blood mononuclear cells (PBMCs). We showed that microRNA miR29 suppresses DNMT activity and thus induces expression of COX2 and PGE2. Furthermore, miR29 expression was elevated 50-fold in virally infected A549 cells and 10-fold in PBMCs from influenza patients, compared to expression after mock infection of A549 cells or in healthy individuals, respectively. Activation of the protein kinase A signaling pathway and phosphorylation of CREB1 also contributed to COX2 expression. Collectively, our work defines a novel proinflammatory cascade in the control of influenza A virus infection.     

Lack of Evidence for the Role of Human Adenovirus‐36 in Obesity in a European Cohort

Adenovirus infection has been shown to increase adiposity in chickens, mice, and nonhuman primates. Adenovirus type 36 (Ad‐36) DNA was detected in adipose tissues in these animal trials. In the United States, Ad‐36 significantly correlates with obesity as illustrated by an Ad‐36 seroprevalence of 30% in obese individuals and 11% in nonobese individuals. We investigated the possibility of a similar correlation of Ad‐36 in Dutch and Belgian persons. In total, 509 serum samples were analyzed for Ad‐36 antibodies using a serum neutralization assay. In addition, PCR was used to detect adenoviral DNA in visceral adipose tissue of 31 severely obese surgical patients. Our results indicated an overall Ad‐36 seroprevalence of 5.5% increasing with age. BMI of Ad‐36 seropositive humans was not significantly different from seronegative humans. No adenoviral DNA could be found using PCR on visceral adipose tissue. In conclusion, this first Ad‐36 study in the Netherlands and in Belgium indicates that Ad‐36 does not play a role as a direct cause of BMI increase and obesity in humans in Western Europe.     

Methamphetamine Reduces Human Influenza A Virus Replication

Methamphetamine (meth) is a highly addictive psychostimulant that is among the most widely abused illicit drugs, with an estimated over 35 million users in the world. Several lines of evidence suggest that chronic meth abuse is a major factor for increased risk of infections with human immunodeficiency virus and possibly other pathogens, due to its immunosuppressive property. Influenza A virus infections frequently cause epidemics and pandemics of respiratory diseases among human populations. However, little is known about whether meth has the ability to enhance influenza A virus replication, thus increasing severity of influenza illness in meth abusers. Herein, we investigated the effects of meth on influenza A virus replication in human lung epithelial A549 cells. The cells were exposed to meth and infected with human influenza A/WSN/33 (H1N1) virus. The viral progenies were titrated by plaque assays, and the expression of viral proteins and cellular proteins involved in interferon responses was examined by Western blotting and immunofluorescence staining. We report the first evidence that meth significantly reduces, rather than increases, virus propagation and the susceptibility to influenza infection in the human lung epithelial cell line, consistent with a decrease in viral protein synthesis. These effects were apparently not caused by meth’s effects on enhancing virus-induced interferon responses in the host cells, reducing viral biological activities, or reducing cell viability. Our results suggest that meth might not be a great risk factor for influenza A virus infection among meth abusers. Although the underlying mechanism responsible for the action of meth on attenuating virus replication requires further investigation, these findings prompt the study to examine whether other structurally similar compounds could be used as anti-influenza agents.     

Interactions between Streptococcus pneumoniae and influenza virus: a mutually beneficial relationship?

Historically, most research on infectious diseases has focused on infections with single pathogens. However, infections with pathogens often occur in the context of pre-existing viral and bacterial infections. Clinically, this is of particular relevance for coinfections with Streptococcus pneumoniae and influenza virus, which together are an important cause of global morbidity and mortality. In recent years new evidence has emerged regarding the underlying mechanisms of influenza virus-induced susceptibility to secondary pneumococcal infections, in particular regarding the sustained suppression of innate recognition of S. pneumoniae. Conversely, it is also increasingly being recognized that there is not a unidirectional effect of the virus on S. pneumoniae, but that asymptomatic pneumococcal carriage may also affect subsequent influenza virus infection and the clinical outcome. Here, we will review both aspects of pneumococcal influenza virus infection, with a particular focus on the age-related differences in pneumococcal colonization rates and invasive pneumococcal disease.     

The role of respiratory tract viruses in the etiology of obstructive bronchitis in infants

Out of 524 children with acute respiratory infections in 141 obstructive bronchitis was diagnosed (OZO). Seventy cases could be linked to viral infection. Viral infections tested (influenza virus A, B, parainfluenza typ 1-3, RSV, adenoviruses) were more frequently associated with OZO than other acute respiratory infections of unknown etiology. Majority infections induced by influenza virus A and parainfluenza virus typ 2 were accompanied by OZO symptoms. Of the highest risk of acquiring OZO despite of viral infection participation, were children of 4-12 months of age. OZO associated viral infections prevailed during autumn-winter season, while in spring-summer period undetermined factors were the major cause of OZO. In serum samples of children with OZO, despite of etiology of the disease, higher level of IgE was found than in a group of children without the symptoms. In the case of OZO of unestablished etiology the level of serum IgE was significantly higher than in the cases when viral etiology of the disease was found.     

Mast cell-induced lung injury in mice infected with H5N1 influenza virus

Although an important role for mast cells in several viral infections has been demonstrated, its role in the invasion of highly pathogenic H5N1 influenza virus is unknown. In the present study, we demonstrate that mast cells were activated significantly by H5N1 virus (A/chicken/Henan/1/2004) infection both in vivo and in vitro. Mast cells could possibly intensify the lung injury that results from H5N1 infection by releasing proinflammatory mediators, including histamine, tryptase, and gamma interferon (IFN-γ). Lung lesions and apoptosis induced by H5N1 infection were reduced dramatically by treatment with ketotifen, which is a mast cell degranulation inhibitor. A combination of ketotifen and the neuraminidase inhibitor oseltamivir protected 100% of the mice from death postinfection. In conclusion, our data suggest that mast cells play a crucial role in the early stages of H5N1 influenza virus infection and provide a new approach to combat highly pathogenic influenza virus infection.     

Neuraminidase inhibitors for treatment of human and avian strain influenza: A comparative modeling study

Treatment of seasonal influenza viral infections using antivirals such as neuraminidase inhibitors (NAIs) has been proven effective if administered within 48 h post-infection. However, there is growing evidence that antiviral treatment of infections with avian-derived strains even as late as 6 days post-infection (dpi) can significantly reduce infection severity and duration. Using a mathematical model of in-host influenza viral infections which can capture the kinetics of both a short-lived, typical, seasonal infection and a severe infection exhibiting sustained viral titer, we explore differences in the effects of NAI treatment on both types of influenza viral infections. Comparison of our model's behavior against experimental data from patients naturally infected with avian strains yields estimates for the times at which patients were infected that are consistent with those reported by the patients, and estimates of drug efficacies that are lower for patients who died than for those who recovered. In addition, our model suggests that the sustained, high, viral titers often seen in more severe influenza virus infections are the reason why antiviral treatment delayed by as much as 6 dpi will still lead to reduced viral titers and shortened illness. We conclude that NAIs may be an effective and beneficial treatment strategy against more severe strains of influenza virus characterized by high, sustained, viral titers. We believe that our mathematical model will be an effective tool in guiding treatment of severe influenza viral infections with antivirals.     

Protection from H1N1 Influenza Virus Infections in Mice by Supplementation with Selenium: A Comparison with Selenium-Deficient Mice

The present paper describes protective effects of supplemental selenium in mice infected with influenza virus. The effects of supplemental selenium on serum selenium levels, mortality, lung virus titers, and cytokine titers were investigated in mice inoculated intranasally with suspensions of influenza virus. Whereas the mortality of the virus-infected Se-deficient mice was 75%, along with a marked reduction in body weight, lower levels of TNF-α and IFN-γ and lower serum selenium concentrations, the mortality of mice maintained on feed containing 0.5 mg Se/kg in the form of sodium selenite was 25%.There were no significantly differences, however, in viral titer between the Se-adequate and the selenium-supplemented groups. The data indicate that selenium supplementation may provide a feasible approach to improving the immune response to viral infections, such as lethal influenza infection.     

Leptin and cancer

The prevalence of obesity has markedly increased over the past two decades, especially in the industrialized countries. While the impact of excess body weight on the development of cardiac disease and diabetes has been well documented, the link between obesity and carcinogenesis is just being recognized. This review will focus on the link between leptin, a cytokine that is elevated in obese individuals, and cancer development. First, we briefly discuss the biological functions of leptin and its signaling pathways. Then, we summarize the effects of leptin on different cancer types in experimental cellular and animal models. Next, we analyze epidemiological data on the relationship between obesity and the presence of cancer or cancer risk in patients. Finally, leptin as a target for cancer treatment and prevention will be discussed.     

Antiviral cyclic D,L-alpha-peptides: targeting a general biochemical pathway in virus infections

Diverse virus families have evolved to exploit the acidification of endosomal compartments to gain entry into cells. We describe a supramolecular approach for selectively targeting and inhibiting viral infections through this central biochemical pathway. Using adenovirus as a model non-enveloped virus, we have determined that an eight-residue cyclic D,L-alpha-peptide, selected from a directed combinatorial library, can specifically prevent the development of low pH in endocytic vesicles, arrest the escape of virions from the endosome, and abrogate adenovirus infection without an apparent adverse effect on cell viability. The likely generality of this approach against other pH-dependent viral infections is supported by the inhibition of type-A influenza virus escape from endosomes in the presence of the same peptide. Our studies suggest that self-assembling cyclic D,L-alpha-peptides hold considerable potential as a new rational supramolecular approach toward the design and discovery of broad-spectrum antiviral agents.     

Influenza A virus—a model for viral antigen presentation to cytotoxic T lymphocytes

Human influenza A virus is characterized by its high degree of variability and by its ability to cause frequent epidemics of disease. Most of the variation occurs in the two surface glycoproteins of the virus, against which protective antibodies are directed. In contrast, the strong MHC class I-restricted CTL response to infection with virus is predominantly specific for internal viral proteins which are relatively well conserved, and is cross-reactive between different strains of influenza A virus. However, the natural evolution of influenza viruses is largely driven by selection with antibody, with no firm evidence of selection by CTL. In normal individuals influenza virus produces an acute, localized infection, and this in part may reflect an inability to escape the CTL response.     

Significance of Legionella pneumophila in human respiratory pathology

The etiological structure of acute pneumonia and acute respiratory diseases was studied with a view to establishing the proportion of L. pneumophila among other causative agents of such diseases. A total of 299 patients were examined over time. The etiological diagnosis based on the data of serological examination was made in 70.6% of the patients with acute pneumonia and in 65% of the patients with acute respiratory viral infections and influenza. In the etiology of pneumonia, the leading role was found to belong to influenza A (H3N2) and B viruses, as well as to adenovirus, while in the etiology of acute respiratory viral infections and influenza, to influenza B virus, adenovirus and Mycoplasma pneumoniae. The importance of L. pneumophila in the etiology of acute pneumonia and acute respiratory diseases was shown. The proportion of L. pneumophila proved to be, on the average, 9.9% in acute pneumonia and 9.8% in acute respiratory diseases. L. pneumophila occurred most frequently in mixed infections in combination with adenovirus and influenza B virus. Diseases of Legionella etiology were found to have a seasonal character, occurring mostly in winter and spring.     

Pterostilbene effectively inhibits influenza A virus infection by promoting the type I interferon production

With the prevalence of novel strains and drug-resistant influenza viruses, there is an urgent need to develop effective and low-toxicity anti-influenza therapeutics. Regulation of the type I interferon antiviral response is considered an attractive therapeutic strategy for viral infection. Pterostilbene, a 3,5-dimethoxy analog of resveratrol, is known for its remarkable pharmacological activity. Here, we found that pterostilbene effectively inhibited influenza A virus infection and mainly affected the late stages of viral replication. A mechanistic study showed that the antiviral activity of pterostilbene might promote the induction of antiviral type I interferon and expression of its downstream interferon-stimulated genes during viral infection. The same effect of pterostilbene was also observed in the condition of polyinosinic-polycytidylic acid (poly I:C) transfection. Further study showed that pterostilbene interacted with influenza non-structural 1 (NS1) protein, inhibited ubiquitination mediated degradation of RIG-I and activated the downstream antiviral pathway, orchestrating an antiviral state against influenza virus in the cell. Taken together, pterostilbene could be a promising anti-influenza agent for future antiviral drug exploitation and compounds with similar structures may provide new options for the development of novel inhibitors against influenza A virus (IAV).