Infection with respiratory syncytial virus enhances expression of native receptors for non-pilate Neisseria meningitidis on HEp-2 cells

Baicalin Induces a Potent Innate Immune Response to Inhibit Respiratory Syncytial Virus Replication via Regulating Viral Non-Structural 1 and Matrix RNA

Respiratory syncytial virus (RSV) infection is the most frequent cause of hospitalization in pediatric patients. Current systemic treatment and vaccines are not curative and re-infection is often associated with a more drastic incidence of the disease. Baicalin is a flavonoid isolated from Scutellaria baicalensis with potent anti-viral characteristics, namely against RSV. However, its precise mechanism of action remains unclear. Here, using in vitro methods and an in vivo murine model of RSV infection, we showed that baicalin inhibits RSV replication induces translational upregulation of type I interferons (IFNs), IFN-α and IFN-β, and reverses epithelial thickening in lung tissues. Moreover, baicalin inhibits transcription of the RSV non-structural proteins NS1 and NS2. Molecular docking and surface plasmon resonance-based affinity analysis showed that baicalin also binds to the α3 helix of the NS1 protein with an affinity constant of 1.119 × 10⁻⁵ M. Polysome profiling showed that baicalin inhibits translation of the RSV matrix protein (M) RNA. Baicalin mediates increased release of the ribosomal protein L13a from the large ribosomal subunit, where the extra ribosomal subunit L13a inhibits M RNA translation. These results comprehensively establish the multiple mechanisms by which baicalin induces a potent innate immune response against RSV infection.

Multiple Respiratory Syncytial Virus (RSV) Strains Infecting HEp-2 and A549 Cells Reveal Cell Line-Dependent Differences in Resistance to RSV Infection

Respiratory syncytial virus (RSV) is a leading cause of pediatric acute respiratory infection worldwide. There are currently no approved vaccines or antivirals to combat RSV disease. A few transformed cell lines and two historic strains have been extensively used to study RSV. Here, we reported a thorough molecular and cell biological characterization of HEp-2 and A549 cells infected with one of four strains of RSV representing both major subgroups as well as historic and more contemporary genotypes (RSV/A/Tracy [GA1], RSV/A/Ontario [ON], RSV/B/18537 [GB1], and RSV/B/Buenos Aires [BA]) via measurements of viral replication kinetics and viral gene expression, immunofluorescence-based imaging of gross cellular morphology and cell-associated RSV, and measurements of host response, including transcriptional changes and levels of secreted cytokines and growth factors.

IMPORTANCE Infection with the respiratory syncytial virus (RSV) early in life is essentially guaranteed and can lead to severe disease. Most RSV studies have involved either of two historic RSV/A strains infecting one of two cell lines, HEp-2 or A549 cells. However, RSV contains ample variation within two evolving subgroups (A and B), and HEp-2 and A549 cell lines are genetically distinct. Here, we measured viral action and host response in both HEp-2 and A549 cells infected with four RSV strains from both subgroups and representing both historic and more contemporary strains. We discovered a subgroup-dependent difference in viral gene expression and found A549 cells were more potently antiviral and more sensitive, albeit subtly, to viral variation. Our findings revealed important differences between RSV subgroups and two widely used cell lines and provided baseline data for experiments with model systems better representative of natural RSV infection.

Rocking Pneumonia and the Boogie Woogie Flu

The relation between pneumonia and influenza is regularly addressed in modern music. Epidemiological data obtained during influenza pandemics, as well as during seasonal influenza, illustrate and underscore this association. Even though the number of pneumonia cases are generally under-reported and blood tests show a lack of sensitivity, a clear link between influenza and pneumonia can still be observed. In fact, the majority of mortality during influenza pandemics is due to pneumonia caused by a bacterial superinfection, in most cases Streptococcus pneumoniae. Vaccination is a powerful tool to prevent the development of both influenza and pneumonia in children, as well as in the elderly. Cellular and molecular data show that influenza can lead to changes in the integrity of lung epithelial cells, including desialysation of carbohydrate moieties, which favour attachment and invasion of S. pneumoniae. Further elucidation of these mechanisms could lead to targeted intervention strategies, in which universal influenza vaccines could play a role.

Efficacy and long-term outcomes of palivizumab prophylaxis to prevent respiratory syncytial virus infection in infants with cystic fibrosis in Northern Ireland

BACKGROUND

RSV causes considerable morbidity and mortality in children. In cystic fibrosis (CF) viral infections are associated with worsening respiratory symptoms and bacterial colonization. Palivizumab is effective in reducing RSV hospitalization in high risk patient groups. Evidence regarding its effectiveness and safety in CF is inconclusive. CF screening in N. Ireland enabled timely palivizumab prophylaxis, becoming routine in 2002.

OBJECTIVES

To determine the effect of palivizumab on RSV-related hospitalization and compare lung function and bacterial colonization at age 6 years for those born pre- and post-introduction of palivizumab prophylaxis.

METHODS

A retrospective audit was conducted for all patients diagnosed with CF during the period from 1997 to 2007 inclusive. RSV-related hospitalization, time to Pseudomonas aeruginosa (PA) 1st isolate, lung function and growth parameters were recorded. Comparisons were made for outcomes pre- and post-introduction of routine palivizumab administration in 2002. A cost evaluation was also performed.

RESULTS

Ninety-two children were included; 47 pre- and 45 post-palivizumab introduction. The overall RSV-positive hospitalization rate was 13%. The relative risk of RSV infection in palivizumab non-recipients versus recipients was 4.78 (95%CI: 1.1-20.7), P = 0.027. Notably, PA 1st isolate was significantly earlier in the palivizumab recipient cohort versus non-recipient cohort (median 57 vs. 96 months, P < 0.025) with a relative risk of 2.5. Chronic PA infection at 6 years remained low in both groups, with similar lung function and growth parameters. Total costs were calculated at £96,127 ($151,880) for the non-recipient cohort versus £137,954 ($217,967) for the recipient cohort.

CONCLUSION

Palivizumab was effective in reducing RSV-related hospitalization infection in CF patients. Surprisingly, we found a significantly earlier time to 1st isolate of PA in palivizumab recipients which we could not explain by altered or improved diagnostic tests.

Many respiratory viruses have temporal association with meningococcal disease

BACKGROUND

Previous ecological studies have shown a temporal and spatial association between influenza epidemics and meningococcal disease (MNG); however, none have examined more than two respiratory viruses.

METHODS

Data were obtained in Chile between 2000 and 2005 on confirmed cases of MNG and all confirmed cases of respiratory viruses (influenza A and B; parainfluenza; adenovirus; and respiratory syncytial virus [RSV]). Both variables were divided by epidemiological weeks, age range, and regions. Models of transference functions were run for rates of MNG.

RESULTS

In this period, 1022 reported cases of MNG and 34,737 cases of respiratory virus were identified (25,137 RSV; 4300 parainfluenza; 2527 influenza-A; 356 influenza-B; and 2417 adenovirus). RSV was the major independent virus temporally associated to MNG (it appears one week before MNG), followed by parainfluenza, influenza-B, adenovirus, and influenza-A.

CONCLUSIONS

The rate of MNG in Chile is temporally associated to all of the respiratory viruses studied, but with variability according age range, and regions.

Viral bacterial co-infection of the respiratory tract during early childhood

Acute respiratory infection (ARI) is an important cause of morbidity in children. Mixed aetiology is frequent, with pathogenic viruses and bacteria co-detected in respiratory secretions. However, the clinical significance of these viral/bacterial co-infections has long been a controversial topic. While severe bacterial pneumonia following influenza infection has been well described, associations are less clear among infections caused by viruses that are more common in young children, such as respiratory syncytial virus. Although assessing the overall contribution of bacteria to disease severity is complicated by the presence of many confounding factors in clinical studies, understanding the role of viral/bacterial co-infections in defining the outcome of paediatric ARI will potentially reveal novel treatment and prevention strategies, improving patient outcomes. This review summarizes current evidence for the clinical significance of respiratory viral/bacterial co-infections in young children, discusses possible mechanisms of cooperative interaction between these pathogens and highlights areas that require further investigation.

Exploring the risk factors for sudden infant deaths and their role in inflammatory responses to infection

The risk factors for sudden infant death syndrome (SIDS) parallel those associated with susceptibility to or severity of infectious diseases. There is no evidence that a single infectious agent is associated with SIDS; the common thread appears to be induction of inflammatory responses to infections. In this review, interactions between genetic and environmental risk factors for SIDS are assessed in relation to the hypothesis that many infant deaths result from dysregulation of inflammatory responses to "minor" infections. Risk factors are assessed in relation to three important stages of infection: (1) bacterial colonization (frequency or density); (2) induction of temperature-dependent toxins; (3) induction or control of inflammatory responses. In this article, we review the interactions among risk factors for SIDS for their effects on induction or control of inflammatory responses. The risk factors studied are genetic factors (sex, cytokine gene polymorphisms among ethnic groups at high or low risk of SIDS); developmental stage (changes in cortisol and testosterone levels associated with 2- to 4-month age range); environmental factors (virus infection, exposure to cigarette smoke). These interactions help to explain differences in the incidences of SIDS observed between ethnic groups prior to public health campaigns to reduce these infant deaths.

Pro-inflammatory cytokines can act as intracellular modulators of commensal bacterial virulence

Interactions between commensal pathogens and hosts are critical for disease development but the underlying mechanisms for switching between the commensal and virulent states are unknown. We show that the human pathogen Neisseria meningitidis, the leading cause of pyogenic meningitis, can modulate gene expression via uptake of host pro-inflammatory cytokines leading to increased virulence. This uptake is mediated by type IV pili (Tfp) and reliant on the PilT ATPase activity. Two Tfp subunits, PilE and PilQ, are identified as the ligands for TNF-α and IL-8 in a glycan-dependent manner, and their deletion results in decreased virulence and increased survival in a mouse model. We propose a novel mechanism by which pathogens use the twitching motility mode of the Tfp machinery for sensing and importing host elicitors, aligning with the inflamed environment and switching to the virulent state.

In vitro inflammatory responses elicited by isolates of Alloiococcus otitidis obtained from children with otitis media with effusion

Alloiococcus otitidis is usually detected in children with otitis media (OM) by PCR as it is not often detected by routine culture. Our improved method for its isolation obtained A. otitidis from nearly 50% of 78 children with OM with effusion. The role of A. otitidis in pathogenesis of OM is unclear. This study tested two hypothesis: (1) that fresh isolates of A. otitidis would elicit pro-inflammatory cytokines from THP-1 monocytic cells equivalent to those induced by Streptococcus pneumoniae; (2) priming THP-1 cells with interferon-gamma (IFN-γ) a surrogate for virus infection, would enhance pro-inflammatory responses. Recent clinical isolates of A. otitidis, S. pneumoniae (ATCC 49619) and a blood culture isolate of S. pneumoniae (SP2) were used in the assays. Cytokines were quantified by BioRad bead assay and Luminex 200. IFN-γ priming enhanced cytokine responses. S. pneumoniae ATCC 49619 induced lower responses than SP2 for IL-1β, IL-6, TNF-α. A. otitidis LW 27 elicited higher IL-1β and TNF-α responses than either pneumococcal isolate. Small green colony types of A. otitidis induced higher responses than large white colony types for IL-8 and IL-1β. The hypothesis that A. otitidis elicits cytokines observed in middle ear effusions was supported; the need to use recent clinical isolates in studies of pathogenesis was highlighted.

Transcriptional adaptation of pneumococci and human pharyngeal cells in the presence of a virus infection

Background

Viral upper respiratory tract infections are associated with increased colonization by Streptococcus pneumoniae but the mechanisms underlying this relationship are unclear. The objective of this study is to describe a comprehensive picture of the cellular interaction between the adhering bacteria and host cells in the presence or absence of a viral co-infection.

Results

Gene expression profiles of Detroit-562 pharyngeal cells, which were either mock-infected or infected with human respiratory syncytial virus (RSV) or human parainfluenza virus 3 (HPIV3), were analyzed using human microarrays. Transcription response of S. pneumoniae strain TIGR4 (serotype 4) in the presence of either mock- or viral-infected cells was analyzed by pneumococcal microarray. Significantly regulated genes were identified by both significance analysis of microarray (SAM) and a ≥ 2-fold change ratio cut-off. The adherence of S. pneumoniae to human pharyngeal cells was significantly augmented in the presence of RSV or HPIV3 infection. Global gene expression profiling of the host cells during infection with RSV or HPIV3 revealed increased transcription of carcinoembryonic antigen-related cell adhesion molecules (CEACAM1), CD47, fibronectin, interferon-stimulated genes and many other host cell adhesion molecules. Pneumococci increased transcription of several genes involved in adhesive functions (psaA, pilus islet), choline uptake and incorporation (lic operon), as well as transport and binding.

Conclusions

We have identified a core transcriptome that represents the basic machinery required for adherence of pneumococci to D562 cells infected or not infected with a virus. These bacterial genes and cell adhesion molecules can potentially be used to control pneumococcal adherence occurring secondary to a viral infection.

Modulation of lipopolysaccharide receptor expression by lactate dehydrogenase-elevating virus

Lactate dehydrogenase-elevating virus (LDV) exacerbates mouse susceptibility to endotoxin shock through enhanced tumour necrosis factor (TNF) production by macrophages exposed to lipopolysaccharide (LPS). However, the in vivo enhancement of TNF production in response to LPS induced by the virus largely exceeds that found in vitro with cells derived from infected animals. Infection was followed by a moderate increase of Toll-like receptor (TLR)-4/MD2, but not of membrane CD14 expression on peritoneal macrophages. Peritoneal macrophages from LDV-infected mice unresponsive to type I interferons (IFNs) did not show enhanced expression of TLR-4/MD2 nor of CD14, and did not produce more TNF in response to LPS than cells from infected normal counterparts, although the in vivo response of these animals to LPS was strongly enhanced. In contrast, the virus triggered a sharp increase of soluble CD14 and of LPS-binding protein serum levels in normal mice. However, production of these LPS soluble receptors was similar in LDV-infected type I IFN-receptor deficient mice and in their normal counterparts. Moreover, serum of LDV-infected mice that contained these soluble receptors had little effect if any on cell response to LPS. These results suggest that enhanced response of LDV-infected mice to LPS results mostly from mechanisms independent of LPS receptor expression.

Genotypic and phenotypic characterization of carriage and invasive disease isolates of Neisseria meningitidis in Finland

The relationship between carriage and the development of invasive meningococcal disease is not fully understood. We investigated the changes in meningococcal carriage in 892 military recruits in Finland during a nonepidemic period (July 2004 to January 2006) and characterized all of the oropharyngeal meningococcal isolates obtained (n = 215) by using phenotypic (serogrouping and serotyping) and genotypic (porA typing and multilocus sequence typing) methods. For comparison, 84 invasive meningococcal disease strains isolated in Finland between January 2004 and February 2006 were also analyzed. The rate of meningococcal carriage was significantly higher at the end of military service than on arrival (18% versus 2.2%; P < 0.001). Seventy-four percent of serogroupable carriage isolates belonged to serogroup B, and 24% belonged to serogroup Y. Most carriage isolates belonged to the carriage-associated ST-60 clonal complex. However, 21.5% belonged to the hyperinvasive ST-41/44 clonal complex. Isolates belonging to the ST-23 clonal complex were cultured more often from oropharyngeal samples taken during the acute phase of respiratory infection than from samples taken at health examinations at the beginning and end of military service (odds ratio [OR], 6.7; 95% confidence interval [95% CI], 2.7 to 16.4). The ST-32 clonal complex was associated with meningococcal disease (OR, 17.8; 95% CI, 3.8 to 81.2), while the ST-60 clonal complex was associated with carriage (OR, 10.7; 95% CI, 3.3 to 35.2). These findings point to the importance of meningococcal vaccination for military recruits and also to the need for an efficacious vaccine against serogroup B isolates.

Respiratory virus infection and risk of invasive meningococcal disease in central Ontario, Canada

Background

In temperate climates, invasive meningococcal disease (IMD) incidence tends to coincide with or closely follow peak incidence of influenza virus infection; at a seasonal level, increased influenza activity frequently correlates with increased seasonal risk of IMD.

Methods

We evaluated 240 cases of IMD reported in central Ontario, Canada, from 2000 to 2006. Associations between environmental and virological (influenza A, influenza B and respiratory syncytial virus (RSV)) exposures and IMD incidence were evaluated using negative binomial regression models controlling for seasonal oscillation. Acute effects of weekly respiratory virus activity on IMD risk were evaluated using a matched-period case-crossover design with random directionality of control selection. Effects were estimated using conditional logistic regression.

Results

Multivariable negative binomial regression identified elevated IMD risk with increasing influenza A activity (per 100 case increase, incidence rate ratio = 1.18, 95% confidence interval (CI): 1.06, 1.31). In case-crossover models, increasing weekly influenza A activity was associated with an acute increase in the risk of IMD (per 100 case increase, odds ratio (OR)  = 2.03, 95% CI: 1.28 to 3.23). Increasing weekly RSV activity was associated with increased risk of IMD after adjusting for RSV activity in the previous 3 weeks (per 100 case increase, OR = 4.31, 95% CI: 1.14, 16.32). No change in disease risk was seen with increasing influenza B activity.

Conclusions

We have identified an acute effect of influenza A and RSV activity on IMD risk. If confirmed, these finding suggest that influenza vaccination may have the indirect benefit of reducing IMD risk.

Pulmonary surfactant phosphatidylglycerol inhibits respiratory syncytial virus-induced inflammation and infection

Respiratory syncytial virus (RSV) is the most common cause of hospitalization for respiratory tract infection in young children. It is also a significant cause of morbidity and mortality in elderly individuals and in persons with asthma and chronic obstructive pulmonary disease. Currently, no reliable vaccine or simple RSV antiviral therapy is available. Recently, we determined that the minor pulmonary surfactant phospholipid, palmitoyl-oleoyl-phosphatidylglycerol (POPG), could markedly attenuate inflammatory responses induced by lipopolysaccharide through direct interactions with the Toll-like receptor 4 (TLR4) interacting proteins CD14 and MD-2. CD14 and TLR4 have been implicated in the host response to RSV. Treatment of bronchial epithelial cells with POPG significantly inhibited interleukin-6 and -8 production, as well as the cytopathic effects induced by RSV. The phospholipid bound RSV with high affinity and inhibited viral attachment to HEp2 cells. POPG blocked viral plaque formation in vitro by 4 log units, and markedly suppressed the expansion of plaques from cells preinfected with the virus. Administration of POPG to mice, concomitant with viral infection, almost completely eliminated the recovery of virus from the lungs at 3 and 5 days after infection, and abrogated IFN-gamma (IFN-gamma) production and the enhanced expression of surfactant protein D (SP-D). These findings demonstrate an important approach to prevention and treatment of RSV infections using exogenous administration of a specific surfactant phospholipid.

The effects of disodium cromoglycate on enhanced adherence of Haemophilus influenzae to A549 cells infected with respiratory syncytial virus

Nontypeable Haemophilus influenzae (NTHi) secondary infection often complicates respiratory syncytial virus (RSV) infections. Previous studies have revealed that RSV infections enhance NTHi adherence to airway epithelial cells. In this study, we investigated the effects of disodium cromoglycate (DSCG) and corticosteroids, which are frequently used for the treatment of wheezing often related to RSV infections, on the adherence of NTHi to RSV-infected A549 cells. DSCG inhibited enhanced adherence of NTHi to RSV-infected A549 cells, whereas dexamethasone (Dex) and fluticasone propionate (Fp) did not. DSCG suppressed the expression of ICAM-1, which is one of the NTHi receptors. Furthermore, DSCG exhibited an inhibitory effect on RSV infections. It is suggested that DSCG exerts an anti-RSV effect, and consequently attenuates the expression of NTHi receptors.

Is shock a key element in the pathology of sudden infant death syndrome (SIDS)?

In developed countries, sudden infant death syndrome (SIDS) is the most common cause of death for infants between 1 month and 1 year of age. The etiology of SIDS is likely to be multifactorial, and current paradigms often describe three overlapping elements of risk. Those elements are a critical developmental period, a vulnerable infant, and one or more exogenous stressors. In the triple-risk model, SIDS infants are described as having an underlying vulnerability in cardiorespiratory control in the central nervous system during a critical period when autonomic control is developing. This vulnerability might affect the response to exogenous stressors, including prone sleeping position, hypoxia, and increased carbon dioxide. In the common bacterial hypothesis and fatal triangle, the focus is on the stressors. In the first, a combination of common respiratory infections can cause SIDS in an infant during a developmentally vulnerable period. This theory also includes 3 factors of vulnerability: a genetic predisposition, a vulnerable developmental age, and infectious stressors. In the fatal triangle theory, infection, inflammation, and genetics each play a role in triggering a SIDS fatality. From our work in an animal model, we have found that rat pups die from a combination of infectious insults during a critical time of development. This is exacerbated by perinatal nicotine exposure, a condition shown to alter the autonomic response in exposed offspring. We are proposing that shock and cardiovascular collapse is a key element that links these theories.

Rhinovirus disrupts the barrier function of polarized airway epithelial cells

RATIONALE

Secondary bacterial infection following rhinovirus (RV) infection has been recognized in chronic obstructive pulmonary disease.

OBJECTIVES

We sought to understand mechanisms by which RV infection facilitates secondary bacterial infection.

METHODS

Primary human airway epithelial cells grown at air-liquid interface and human bronchial epithelial (16HBE14o-) cells grown as polarized monolayers were infected apically with RV. Transmigration of bacteria (nontypeable Haemophilus influenzae and others) was assessed by colony counting and transmission electron microscopy. Transepithelial resistance (R(T)) was measured by using a voltmeter. The distribution of zona occludins (ZO)-1 was determined by immunohistochemistry and immunoblotting.

MEASUREMENTS AND MAIN RESULTS

Epithelial cells infected with RV showed 2-log more bound bacteria than sham-infected cultures, and bacteria were recovered from the basolateral media of RV- but not sham-infected cells. Infection of polarized airway epithelial cell cultures with RV for 24 hours caused a significant decrease in R(T) without causing cell death or apoptosis. Ultraviolet-treated RV did not decrease R(T), suggesting a requirement for viral replication. Reduced R(T) was associated with increased paracellular permeability, as determined by flux of fluorescein isothiocyanate (FITC)-inulin. Neutralizing antibodies to tumor necrosis factor (TNF)-alpha, IFN-gamma and IL-1beta reversed corresponding cytokine-induced reductions in R(T) but not that induced by RV, indicating that the RV effect is independent of these proinflammatory cytokines. Confocal microscopy and immunoblotting revealed the loss of ZO-1 from tight junction complexes in RV-infected cells. Intranasal inoculation of mice with RV1B also caused the loss of ZO-1 from the bronchial epithelium tight junctions in vivo.

CONCLUSIONS

RV facilitates binding, translocation, and persistence of bacteria by disrupting airway epithelial barrier function.

The prevalence of penicillin-non-susceptible Streptococcus pneumoniae among children aged < 5 years correlates with the biannual epidemic activity of respiratory syncytial virus

This study investigated whether the epidemiology of penicillin-non-susceptible pneumococci (PNSP) colonising small children correlated with the biannual epidemic activity of respiratory syncytial virus (RSV). Colonisation rates and the prevalence of PNSP among paediatric outpatients aged < 5 years was analysed between January 1998 and September 2003 using an established national surveillance network. Resistance trends were investigated using time-series analysis to assess the correlation with the biannual pattern of RSV infections and national sales of oral paediatric formulations of antibiotics and antibiotic prescriptions to children aged < 5 years for acute respiratory tract infections. PNSP rates exhibited a biannual cycle in phase with the biannual seasonal RSV epidemics (p < 0.05). Resistance rates were higher during the winter seasons of 1998-1999 (20.1%), 2000-2001 (16.0%) and 2002-2003 (19.1%), compared with the winter seasons of 1997-1998 (8.2%), 1999-2000 (11.6%) and 2001-2002 (9.5%). Antibiotic sales and prescriptions showed regular peaks during each winter, with no significant correlation with the biannual pattern of RSV activity and seasonal trends of PNSP. RSV is an important determinant of the spread of PNSP and must be considered in strategies aimed at antimicrobial resistance control.

Viral respiratory infections in cystic fibrosis

Viral respiratory infections in CF patients are associated with an increase in morbidity at short and long term. Viral infections have a greater impact on CF patients compared to non-CF controls. They result in increased respiratory symptoms, deterioration of Shwachman and radiological scores, prolonged hospitalizations, a persistent decrease of pulmonary function, increased use of antibiotics and a higher frequency of exacerbations at follow-up. In addition, interaction between viruses and bacteria in CF is suggested. Some studies observe increased new bacterial colonization and raised antipseudomonal antibodies in episodes of viral respiratory infections. Experimental data suggest that increased virus replication, impaired specific anti-bacterial defense and increased adherence of bacteria play a role in the pathogenesis of viral respiratory infections in CF. Further knowledge about the role of viruses and interaction with bacteria in CF lung disease might result in new therapeutic strategies to improve prognosis of CF patients.

Direct binding of respiratory syncytial virus to pneumococci: a phenomenon that enhances both pneumococcal adherence to human epithelial cells and pneumococcal invasiveness in a murine model

In a previous study we showed that pneumococcal adherence to epithelial cells was enhanced by a preceding respiratory syncytial virus (RSV) infection. RSV-glycoproteins, expressed on the infected cell surface, may play a role in this enhanced pneumococcal binding, by acting as bacterial receptors. In the current study, it was attempted to analyze the capacity of pneumococci to interact directly with RSV virions. By flow-cytometry, a direct interaction between RSV and pneumococci could be detected. Heparin, an inhibitor of RSV infectivity that interacts with RSV protein-G, blocked RSV-pneumococcal binding, indicating that the latter interaction is indeed mediated by protein-G. RSV-pneumococcal complexes showed enhanced adherence to uninfected human epithelial cells, compared with pneumococcal adherence without bound RSV, and this enhancement was also blocked by heparin. In addition, the significance of these findings in vitro was explored in vivo in a murine model. Both mice that were pretreated with RSV at day 4 before pneumococcal challenge and mice infected with both agents simultaneously showed significantly higher levels of bacteraemia than controls. Simultaneous infection with both agents enhanced the development of pneumococcal bacteraemia most strongly. It was hypothesized that direct viral binding is another mechanism by which RSV can induce enhanced pneumococcal binding to epithelial cells, a phenomenon that is translated in vivo by a higher invasiveness of pneumococci when administered simultaneously with RSV to mice. Apparently, RSV acts in this process as a direct coupling particle between bacteria and uninfected epithelial cells, thereby increasing colonization by and enhancing invasiveness of pneumococci.

Ethnicity, infection and sudden infant death syndrome

Epidemiological studies found the incidence of SIDS among Indigenous groups such as Aboriginal Australians, New Zealand Maoris and Native Americans were significantly higher than those for non-Indigenous groups within the same countries. Among other groups such as Asian families in Britain, the incidence of SIDS has been lower than among groups of European origin. Cultural and childrearing practices as well as socio-economic factors have been proposed to explain the greater risk of SIDS among Indigenous peoples; however, there are no definitive data to account for the differences observed. We addressed the differences among ethnic groups in relation to susceptibility to infection because there is evidence from studies of populations of European origin that infectious agents, particularly toxigenic bacteria might trigger the events leading to SIDS. The risk factors for SIDS parallel those for susceptibility to infections in infants, particularly respiratory tract infections which are also major health problems among Indigenous groups. Many of the risk factors identified in epidemiological studies of SIDS could affect three stages in the infectious process: (1) frequency or density of colonisation by the toxigenic species implicated in SIDS; (2) induction of temperature-sensitive toxins; (3) modulation of the inflammatory responses to infection or toxins. In this review we compare genetic, developmental and environmental risk factors for SIDS in ethnic groups with different incidences of SIDS: low (Asians in Britain); moderate (European/Caucasian); high (Aboriginal Australian). Our findings indicate: (1) the major difference was high levels of exposure to cigarette smoke among infants in the high risk groups; (2) cigarette smoke significantly reduced the anti-inflammatory cytokine interleukin-10 responses which control pro-inflammatory responses implicated in SIDS; (3) the most significant effect of cigarette smoke on reduction of IL-10 responses was observed for donors with a single nucleotide polymorphism for the IL-10 gene that is predominant among both Asian and Aboriginal populations. If genetic makeup were a major factor for susceptibility to SIDS, the incidence of these deaths should be similar for both populations. They are, however, significantly different and most likely reflect differences in maternal smoking which could affect frequency and density of colonisation of infants by potentially pathogenic bacteria and induction and control of inflammatory responses.

Adherence of type 1-fimbriated Escherichia coli to uroepithelial cells: more in diabetic women than in control subjects

OBJECTIVE

Women with diabetes have bacteriuria more often than women without diabetes. Because Escherichia coli adhere better to vaginal cells of nondiabetic patients with recurrent urinary tract infections (UTIs) than to those obtained from healthy control subjects, it was hypothesized that E. coli adhere more to the uroepithelial cells of diabetic women, either because of substances excreted in the urine (e.g., albumin, glucose, and Tamm Horsfall protein) or because of a difference in the uroepithelial cells.

RESEARCH DESIGN AND METHODS

A T24 bladder cell line and uroepithelial cells of 25 diabetic women and 19 control subjects were incubated with three different E. coli strains.

RESULTS

The mean numbers of type 1-fimbriated E. coli that adhered to diabetic and control cells were 12.9 and 6.1 (P = 0.001), respectively, whereas those of P-fimbriated E. coli were 8.8 and 8.1 (P = 0.8), and those of nonfimbriated E. coli were 2.7 and 3.4 (P = 0.4). The addition of various substances did not influence the adherence of E. coli to a T24 bladder cell line.

CONCLUSIONS

Type 1-fimbriated E. coli adhere more to diabetic than to control uroepithelial cells.

The role of bacterial toxins in sudden infant death syndrome (SIDS)

There is increasing evidence for the involvement of bacterial toxins in some cases of sudden infant death syndrome (SIDS), particularly the pyrogenic toxins of Staphylococcus aureus. This had led to the hypothesis that some SIDS deaths are due to induction of inflammatory mediators by infectious agents or their products during a period in which the infant is unable to control these normally protective responses. The genetic, developmental and environmental risk factors identified for SIDS are assessed in relation to frequency or density of mucosal colonisation by toxigenic bacteria and their effects on induction and control of inflammatory responses to the toxins.

Gene expression in epithelial cells in response to pneumovirus infection

Respiratory syncytial virus (RSV) and pneumonia virus of mice (PVM) are viruses of the family Paramyxoviridae, subfamily pneumovirus, which cause clinically important respiratory infections in humans and rodents, respectively. The respiratory epithelial target cells respond to viral infection with specific alterations in gene expression, including production of chemoattractant cytokines, adhesion molecules, elements that are related to the apoptosis response, and others that remain incompletely understood. Here we review our current understanding of these mucosal responses and discuss several genomic approaches, including differential display reverse transcription-polymerase chain reaction (PCR) and gene array strategies, that will permit us to unravel the nature of these responses in a more complete and systematic manner.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Respiratory viral infection predisposing for bacterial disease: a concise review

Although bacterial superinfection in viral respiratory disease is a clinically well documented phenomenon, the pathogenic mechanisms are still poorly understood. Recent studies have revealed some of the mechanisms involved. Physical damage to respiratory cells as a result of viral infection may lead to opportunistic adherence of bacteria. Enhanced bacterial adherence by specific mechanisms has been documented for respiratory cells infected with influenza A virus, respiratory syncytial virus and adenovirus in both in vitro and in vivo models. To date, results of various experimental studies indicate that different mechanisms for increased bacterial adherence induced by viruses are operating for specific viral-bacterial combinations. In the present review, a number of key findings obtained during the past two decades is presented and discussed.

Infection, inflammation and sleep: more pieces to the puzzle of sudden infant death syndrome (SIDS)

Risk factors for sudden infant death syndrome (SIDS) parallel those for respiratory tract infections; however, infectious agents suggested to be involved in SIDS do not fulfil Koch's postulates. No single agent has been identified in all cases and there is no suitable animal model for SIDS which could be used to test the candidate organisms. Based on epidemiological and experimental work by our group and others, we suggested some SIDS deaths are due to pathophysiological responses elicited by combinations of microbial products and/or cigarette smoke during a developmental stage when infants' endocrine responses are less able to "damp down" the effects of inflammatory mediators. Here we review evidence from studies on interactions between developmental and environmental risk factors that could affect 1) mucosal colonization of infants by potentially pathogenic bacteria, and 2) induction and control of infants', inflammatory responses to infectious agents. New evidence suggests that there are genetic factors involved in the induction of inflammatory responses to some bacterial antigens implicated in SIDS. Further investigation of the role of infection, exposure to cigarette smoke and inflammation in infants, particularly differences in ethnic groups at increased risk of SIDS, could lead to new insights into the events leading to a fatal outcome and perhaps to new intervention schemes to reduce further the incidence of these deaths.