Janak A. Patel

Expression of interleukin 8 and CD54 by human gastric epithelium after Helicobacter pylori infection in vitro

BACKGROUND/AIMS Helicobacter pylori is associated with neutrophil infiltrates, although the mechanism of their recruitment is only partially defined. The aim of the study was to determine if Kato III, a human gastric epithelial cell line, expressed cytokines and the intercellular adhesion molecule 1 (ICAM-1), which could contribute to the initiation of inflammation during infection with H. pylori. METHODS Kato III cells were stimulated with H. pylori and were examined for evidence of infection, cytokine production, and the expression of ICAM-1. RESULTS The expression of interleukin 8 messenger RNA and immunoreactive protein by Kato III cells was significantly increased over constitutive levels within 3 hours of infection with H. pylori. Infected Kato III supernatants activated neutrophils as evidenced by increased CD11b/CD18 and decreased L-selectin that could be blocked by anti-interleukin 8. In contrast, Campylobacter jejuni, lipopolysaccharide, killed H. pylori, and supernatants from cultures of H. pylori did not increase interleukin 8. Interleukins 2 and 6; interferons alfa, beta, and gamma; and tumor necrosis factor were not produced by resting or H. pylori-stimulated Kato III cells. In addition to producing interleukin 8, Kato III constitutively expressed surface ICAM-1, which acts as an intercellular adhesion molecule for neutrophils. CONCLUSIONS Our results indicate that H. pylori stimulates the gastric epithelium to initiate inflammation and neutrophil recruitment and activation.

Viral upper respiratory tract infection and otitis media complication in young children.

Abstract Background. The common cold or upper respiratory infection (URI) is highly prevalent among young children and often results in otitis media (OM). The incidence and characteristics of OM complicating URI due to specific viruses have not been well studied. Methods. We performed a prospective, longitudinal cohort study of 294 healthy children (age range, 6 months to 3 years). Each child was observed for 1 year to assess the occurrence of URI, acute OM (AOM), and OM with effusion (OME) complicating URI due to specific viruses. Results. We documented 1295 URI episodes (5.06 episodes per child-year) and 440 AOM episodes (1.72 episodes per child-year). Virus studies were performed for 864 URI episodes; 63% were virus positive. Rhinovirus and adenovirus were most frequently detected during URI. The overall incidence of OM that complicated URI was 61%, including a 37% incidence of AOM and a 24% incidence of OME. Young age was the most important predictor of AOM that complicated URI. AOM occurred in approximately one-half of children with URI due to adenovirus, respiratory syncytial virus, or coronavirus and in approximately one-third of those with URI due to influenza virus, parainfluenza virus, enterovirus, or rhinovirus. Conclusions. More than 60% of episodes of symptomatic URI among young children were complicated by AOM and/or OME. Young age and specific virus types were predictors of URI complicated by AOM. For young children, the strategy to prevent OM should involve prevention of viral URI. The strategy may be more effective if the priority is given to development of means to prevent URI associated with adenovirus and respiratory syncytial virus.

Effect of viral respiratory tract infection on outcome of acute otitis media

We prospectively studied 271 infants and children (2 months to 7 years of age) with acute otitis media (AOM) for viral and bacterial causes, outcome at the end of therapy, and frequency of recurrence within 1 month. Comprehensive virologic methods, including viral antigen detection, cell culture, and serologic studies, were used to diagnose viral infection of the respiratory tract, middle ear, or both. Evidence of viral infection was found in 46% (124/271) of patients with AOM. Sixty-six patients (24%) had virus or viral antigen in the middle ear fluid; 50 of these patients (76%) also had bacteria in middle ear fluid, and 16 (24%) had virus alone. More patients with AOM and combined bacterial and viral infection (51%) had persistent otitis (3 to 12 days after institution of antibiotic treatment), compared with those with only bacterial otitis (35%; p = 0.05) or patients with only viral infection (19%; p less than 0.01). Of patients with only viral infection, 4 of 10 with virus in middle ear fluid had persistent otitis, compared with none of 11 patients who had virus only in nasal wash specimens or whose viral infection was diagnosed only by serologic studies. Our data suggest that viruses interact with bacteria and that concurrent viral infection can significantly worsen the clinical course of bacterial AOM. The presence of virus in middle ear fluid may contribute to the pathogenesis and outcome of bacterial AOM. The mechanism of these interactions deserve further investigation.

Microbial interactions during upper respiratory tract infections.

Competitive interactions between bacteria differ by number and species present; thus, vaccination and treatment strategies may alter nasopharyngeal flora and disease susceptibility.

Helicobacter pylori Infection Induces Oxidative Stress and Programmed Cell Death in Human Gastric Epithelial Cells

ABSTRACT Helicobacter pylori infection is associated with altered gastric epithelial cell turnover. To evaluate the role of oxidative stress in cell death, gastric epithelial cells were exposed to various strains of H. pylori, inflammatory cytokines, and hydrogen peroxide in the absence or presence of antioxidant agents. Increased intracellular reactive oxygen species (ROS) were detected using a redox-sensitive fluorescent dye, a cytochrome c reduction assay, and measurements of glutathione. Apoptosis was evaluated by detecting DNA fragmentation and caspase activation. Infection with H. pylori or exposure of epithelial cells to hydrogen peroxide resulted in apoptosis and a dose-dependent increase in ROS generation that was enhanced by pretreatment with inflammatory cytokines. Basal levels of ROS were greater in epithelial cells isolated from gastric mucosal biopsy specimens from H. pylori-infected subjects than in cells from uninfected individuals. H. pylori strains bearing the cag pathogenicity island (PAI) induced higher levels of intracellular oxygen metabolites than isogenic cag PAI-deficient mutants. H. pylori infection and hydrogen peroxide exposure resulted in similar patterns of caspase 3 and 8 activation. Antioxidants inhibited both ROS generation and DNA fragmentation by H. pylori. These results indicate that bacterial factors and the host inflammatory response confer oxidative stress to the gastric epithelium during H. pylori infection that may lead to apoptosis.

Incidence of Acute Otitis Media and Sinusitis Complicating Upper Respiratory Tract Infection: The Effect of Age

Infants and young children are prone to developing upper respiratory tract infections, which often result in bacterial complications such as acute otitis media and sinusitis. We evaluated 623 upper respiratory tract infection episodes in 112 children (6–35 months of age) to determine the proportion of upper respiratory tract infection episodes that result in acute otitis media or sinusitis. Of all upper respiratory tract infections, 30% were complicated by acute otitis media and 8% were complicated by sinusitis. The rate of acute otitis media after upper respiratory tract infection declined with increasing age, whereas the rate of sinusitis after upper respiratory tract infection peaked in the second year of life. Risk for acute otitis media may be reduced substantially by avoiding frequent exposure to respiratory viruses (eg, avoidance of day care attendance) in the first year of life.

Effect of pneumococcal conjugate vaccine on nasopharyngeal bacterial colonization during acute otitis media

The heptavalent pneumococcal conjugate vaccine (PCV7) has been shown to reduce the incidence of acute otitis media (AOM) caused by Streptococcus pneumoniae by 34% and reduces the overall incidence of AOM by 6% to 8%. More recent studies have shown increases in the proportion of Haemophilus influenzae and Moraxella catarrhalis in the middle-ear fluid of PCV7-immunized children. There has been no report on the effect of PCV7 on all 3 bacterial pathogens combined, either in the middle-ear fluid or nasopharynx of individual children with AOM. We investigated the impact of PCV7 on nasopharyngeal colonization with bacterial pathogens during AOM in the pre-PCV7 and post-PCV7 vaccination eras. Four hundred seventeen children (6 months to 4 years of age) were enrolled onto AOM studies between September 1995 and December 2004. Of these, 200 were enrolled before the vaccine use (historical controls), and 217 were enrolled after the initiation of PCV7 vaccination (101 were underimmunized, and 116 were immunized). Although the nasopharyngeal colonization rate for S pneumoniae was not different between the 3 groups, a significantly higher proportion of PCV7-immunized children with AOM were colonized with M catarrhalis. Overall, the mean number of pathogenic bacteria types isolated from immunized children (1.7) was significantly higher than in controls (1.4). The increase in bacterial colonization of the nasopharynx during AOM could be associated with an increase in AOM pathogens and theoretically can predispose PCV7-immunized children with AOM to a higher rate of antibiotic treatment failure or recurrent AOM.

Role of leukotriene B4 and interleukin-8 in acute bacterial and viral otitis media.

In order to evaluate the role of polymorphonuclear leukocytes (PMNs) in acute otitis media (AOM), levels of leukotriene B4 (LTB4), a potent inflammatory product of PMNs, and interleukin-8 (IL-8), a PMN chemotactic cytokine, were measured in 271 middle ear fluid (MEF) samples from 106 children with AOM. Forty-two percent of the patients had evidence of respiratory viral infection. At the time of diagnosis, levels of both LTB4 and IL-8 were higher in the MEFs from patients with AOM associated with bacterial or bacterial and viral infection than those MEFs containing no pathogen (p < .05). Antibiotic treatment was not associated with a significant change in levels of LTB4 or IL-8 in the MEFs obtained 2 to 5 days into treatment, compared to those obtained at diagnosis. Bacteriologic failure after 2 to 5 days of treatment was associated with high LTB4 levels in the initial MEFs (p = .05). Recurrence of AOM within 1 month was associated with high IL-8 levels in the initial MEF (p = .04). Our findings suggest that LTB4 and IL-8 are produced during acute infection of the middle ear, and these PMN-related inflammatory substances may play an important role in delaying recovery or in recurrence of AOM. Effective treatment of AOM may require eradication of bacteria by antibiotics, as well as pharmacologic agents that modulate PMN functions.

Association of proinflammatory cytokine gene polymorphisms with susceptibility to otitis media.

OBJECTIVE. Susceptibility to otitis media results from complex interactions among genetic factors of the host, exposure to pathogens, and environmental influences. The objective of this study was to study the role of single-nucleotide polymorphisms of regulatory elements of proinflammatory cytokine genes tumor necrosis factor-α−308, interleukin-1β+3953, and interleukin-6−174, in susceptibility to recurrent otitis media in childhood. METHODS. A total of 505 children (296 otitis media susceptible, 209 nonsusceptible as control) were enrolled at 2 sites (Texas and Kentucky). DNA of the children was studied for specific single-nucleotide polymorphisms by restriction fragment length polymorphism assay and confirmed by gene sequencing. RESULTS. In the overall study group, tumor necrosis factor-α−308 and interleukin-6−174 heterozygous or homozygous polymorphisms (high cytokine-producing genotypes) were significantly associated with otitis media susceptibility. The same association was found in a match-paired subgroup of 384 subjects. In the overall study group, there was a significant step-wise increase in otitis media susceptibility with increasing number of concomitant polymorphic genotypes. Simultaneous combination of tumor necrosis factor-α−308 and interleukin-6−174 polymorphisms further increased the risk for otitis media susceptibility. These 2 polymorphic genotypes also were associated with the increased risk for tympanostomy tube placement. Children who had tumor necrosis factor-α−308 polymorphism and were breastfed for <1 month or exposed to cigarette smoke were more likely to be otitis media susceptible. CONCLUSIONS. Our data suggest that tumor necrosis factor-α−308 and interleukin-6−174 polymorphisms are associated with increased risk for otitis media susceptibility and placement of tympanostomy tubes. Environmental factors such as breastfeeding may modify the risk for otitis media susceptibility in polymorphic individuals.

Persistence of adenovirus nucleic acids in nasopharyngeal secretions: a diagnostic conundrum.

Background: Polymerase chain reaction (PCR) assays increase the rate of viral detection in clinical specimens, compared with conventional virologic methods. Studies suggest that PCR may detect virus nucleic acid (NA) that persists in the respiratory tract. Methods: We analyzed virologic data from children having frequent upper respiratory infections (URI), who were followed up in a longitudinal study. Nasopharyngeal secretions were collected at URI onset and when acute otitis media was diagnosed; virus studies were performed using conventional diagnostics and PCR. Repeated presence of adenovirus by PCR was further studied by sequencing and phylogenetic analysis. Results: Of 581 URI episodes in 76 children, 510 viruses were detected. Of the viruses detected by PCR, 15% were those detected previously; repeated positives occurred most frequently with adenovirus. Sequencing results were available in 13 children with repeated adenovirus detection; the following 4 patterns of infection were identified (16 instances): (1) adenovirus of the same serotype and strain detected continuously (n = 8 instances), (2) adenovirus of different serotypes detected during sequential URI episodes (n = 3), (3) adenovirus of the same serotype but different strains detected during sequential URI episodes (n = 3), and (4) adenovirus of the same serotype and strain detected intermittently (n = 2). Conclusions: Among children with frequent URIs, repeated positive PCR results for adenovirus NA may represent a new serotype/strain, or persistence of viral NA. Results must be interpreted with caution; clinical correlation and presence of other viruses are important. Further longitudinal studies of children during and after infection are required for better understanding of the clinical significance of positive PCR tests for adenovirus NA in the respiratory tract.