Jan L. L. Kimpen

Genetic susceptibility to respiratory syncytial virus bronchiolitis is predominantly associated with innate immune genes

BACKGROUNDnRespiratory syncytial virus (RSV) is a common cause of severe lower respiratory tract infection in infants. Only a proportion of children infected with RSV require hospitalization. Because known risk factors for severe disease, such as premature birth, cannot fully explain differences in disease severity, genetic factors have been implicated.nnnMETHODSnTo study the complexity of RSV susceptibility and to identify the genes and biological pathways involved in its development, we performed a genetic association study involving 470 children hospitalized for RSV bronchiolitis, their parents, and 1008 random, population controls. We analyzed 384 single-nucleotide polymorphisms (SNPs) in 220 candidate genes involved in airway mucosal responses, innate immunity, chemotaxis, adaptive immunity, and allergic asthma.nnnRESULTSnSNPs in the innate immune genes VDR (rs10735810; P=.0017), JUN (rs11688; P=.0093), IFNA5 (rs10757212; P=.0093), and NOS2 (rs1060826; P=.0031) demonstrated the strongest association with bronchiolitis. Apart from association at the allele level, these 4 SNPs also demonstrated association at the genotype level (P=.0056, P=.0285, P=.0372, and P=.0117 for the SNPs in VDR, JUN, IFNA5, and NOS2, respectively). The role of innate immunity as a process was reinforced by association of the whole group of innate immune SNPs when the global test for groups of genes was applied (P=.046).nnnCONCLUSIONnSNPs in innate immune genes are important in determining susceptibility to RSV bronchiolitis.

Identification of strong interleukin-10 inducing lactic acid bacteria which down-regulate T helper type 2 cytokines.

Background Decreased exposure to microbial stimuli has been proposed to be involved in the increased prevalence of atopic disease. Such a relationship was indicated by enhanced presence of typical probiotic bacteria in the intestinal flora correlating with reduced prevalence of atopic disease. Recent clinical trials suggested that probiotic bacteria may decrease and prevent allergic symptoms, but which (different) species or strains may contribute is poorly understood.

Skewed pattern of Toll-like receptor 4-mediated cytokine production in human neonatal blood: Low LPS-induced IL-12p70 and high IL-10 persist throughout the first month of life

Newborns are highly susceptible to infectious diseases, which may be due to impaired immune responses. This study aims to characterize the ontogeny of neonatal TLR-based innate immunity during the first month of life. Cellularity and Toll-like receptor (TLR) agonist-induced cytokine production were compared between cord blood obtained from healthy neonates born after uncomplicated gestation and delivery (n=18), neonatal venous blood obtained at the age of one month (n=96), and adult venous blood (n=17). Cord blood TLR agonist-induced production of the Th1-polarizing cytokines IL-12p70 and IFN-alpha was generally impaired, but for TLR3, 7 and 9 agonists, rapidly increased to adult levels during the first month of life. In contrast, TLR4 demonstrated a slower maturation, with low LPS-induced IL-12p70 production and high IL-10 production up until the age of one month. Polarization in neonatal cytokine responses to LPS could contribute to neonatal susceptibility to severe bacterial infection.

Effectiveness of internet-based cognitive behavioural treatment for adolescents with chronic fatigue syndrome (FITNET): a randomised controlled trial

BACKGROUNDnChronic fatigue syndrome is characterised by persistent fatigue and severe disability. Cognitive behavioural therapy seems to be a promising treatment, but its availability is restricted. We developed Fatigue In Teenagers on the interNET (FITNET), the first dedicated internet-based therapeutic program for adolescents with this disorder, and compared its effectiveness with that of usual care.nnnMETHODSnAdolescents aged 12-18 years with chronic fatigue syndrome were assigned to FITNET or usual care in a 1:1 ratio at one tertiary treatment centre in the Netherlands by use of a computer-generated blocked randomisation allocation schedule. The study was open label. Primary outcomes were school attendance, fatigue severity, and physical functioning, and were assessed at 6 months with computerised questionnaires. Analysis was by intention to treat. Thereafter, all patients were offered FITNET if needed. This trial is registered, number ISRCTN59878666.nnnFINDINGSn68 of 135 adolescents were assigned to FITNET and 67 to usual care, and 67 and 64, respectively, were analysed. FITNET was significantly more effective than was usual care for all dichotomised primary outcomes at 6 months-full school attendance (50 [75%] vs 10 [16%], relative risk 4·8, 95% CI 2·7-8·9; p<0·0001), absence of severe fatigue (57 [85%] vs 17 [27%], 3·2, 2·1-4·9; p<0·0001), and normal physical functioning (52 [78%] vs 13 [20%], 3·8, 2·3-6·3; p<0·0001). No serious adverse events were reported.nnnINTERPRETATIONnFITNET offers a readily accessible and highly effective treatment for adolescents with chronic fatigue syndrome. The results of this study justify implementation on a broader scale.nnnFUNDINGnNetherlands Organisation for Health Research and Development.

Respiratory Syncytial Virus-Induced Activation and Migration of Respiratory Dendritic Cells and Subsequent Antigen Presentation in the Lung-Draining Lymph Node

ABSTRACT In the respiratory tract, different dendritic cell (DC) populations guard a tight balance between tolerance and immunity to infectious or harmless materials to which the airways are continuously exposed. For infectious and noninfectious antigens administered via different routes, different subsets of DC might contribute during the induction of T-cell tolerance and immunity. We studied the impact of primary respiratory syncytial virus (RSV) infection on respiratory DC composition in C57BL/6 mice. We also tracked the migration of respiratory DC to the lymph nodes and studied antigen presentation by lung-derived and lymph node-resident DC to CD4+ and CD8+ T cells. We observed a massive influx of mainly CD103− CD11bhigh CD11c+ conventional DC (cDC) and plasmacytoid DC during the first 7 days of RSV infection, while CD103+ CD11blow CD11c+ cDC disappeared from the lung. The two major subsets of lung tissue DC, CD103+ CD11blow CD11c+ and CD103− CD11bhigh CD11c+ cDC, both transported RSV RNA to the lung-draining lymph node. Furthermore, these lung-derived cDC subsets as well as resident LN DC, which did not contain viral RNA, displayed viral antigen by major histocompatibility complex class I and class II to CD8+ and CD4+ T cells. Taken together, our data indicate that during RSV infections, at least three DC subsets might be involved during the activation of lymph node-homing naïve and memory CD4+ and CD8+ T cells.

Adolescent Chronic Fatigue Syndrome: Prevalence, Incidence, and Morbidity

OBJECTIVE: To determine nationwide general practitioner (GP)-diagnosed prevalence and pediatrician–diagnosed incidence rates of adolescent chronic fatigue syndrome (CFS), and to assess CFS morbidity. DESIGN AND SETTING: We collected data from a cross-sectional national sample among GPs and prospective registration of new patients with CFS in all pediatric hospital departments in the Netherlands. PATIENTS AND METHODS: Study participants were adolescents aged 10 to 18 years. A representative sample of GPs completed questionnaires on the prevalence of CFS in their adolescent patients. Pediatric hospital departments prospectively reported new cases of CFS in adolescent patients. For every new reported case, a questionnaire was sent to the reporting pediatrician and the reported patient to assess CFS morbidity. Prevalence was estimated through the data from GP questionnaires and incidence was estimated on the basis of cases newly reported by pediatricians from January to December 2008. RESULTS: Prevalence was calculated as 111 per 100 000 adolescents and incidence as 12 per 100 000 adolescents per year. Of newly reported patients with CFS, 91% scored at or above cutoff points for severe fatigue and 93% at or above the cutoff points for physical impairment. Forty-five percent of patients with CFS reported >50% school absence during the previous 6 months. CONCLUSIONS: Clinically diagnosed incidence and prevalence rates show that adolescent CFS is uncommon compared with chronic fatigue. The primary adverse impact of CFS is extreme disability associated with considerable school absence.

Selection of probiotic bacteria for prevention of allergic diseases : immunomodulation of neonatal dendritic cells

Modification of intestinal microbiota early in life by administration of probiotic bacteria may be a potential approach to prevent allergic disease. To select probiotic bacteria for in vivo purposes, we investigated the capacity of probiotic bacteria to interact with neonatal dendritic cells (DC) and studied the ensuing T cell polarizing effect. Immature DC were generated from cord blood‐derived monocytes and maturation was induced by maturation factors (MF), lipopolysaccharide (LPS) plus MF and Bifidobacterium bifidum, B. infantis, Lactobacillus salivarius, Lactococcus lactis alone or combined with MF. After 12u2003days of co‐culture with DC and Staphylococcus aureus enterotoxin B (SEB) as antigenic stimulus, cytokine production by autologous T cells was determined by intracellular cytokine staining. Additionally, cells were stimulated with CD3 and CD28 monoclonal antibodies and cytokines were measured in supernatants by multiplex assay. The probiotic strains induced partial maturation of DC. Full maturation of DC was induced for all strains tested when MF was added. The percentage of interleukin (IL)‐4 producing T cells was lower in T cell cultures stimulated with B. bifidum matured DC compared to MF and LPS matured DC, which coincided with a higher percentage of interferon (IFN)‐γ‐producing T cells. Furthermore, T cells stimulated by B. bifidum matured DC produced significantly more IL‐10 compared to MF matured DC. Selected species of the Bifidobacterium genus prime in vitro cultured neonatal DC to polarize T cell responses and may therefore be candidates to use in primary prevention of allergic diseases.

The Wheezing Illnesses Study Leidsche Rijn (WHISTLER): Rationale and design

The Wheezing Illnesses Study Leidsche Rijn (WHISTLER) was initiated in December 2001 as a single-centre prospective birth cohort study and will include a population-based sample of at least 2000 healthy newborns. The aims of WHISTLER are to investigate determinants for wheezing illnesses (including neonatal lung function, viral infections, asthma-susceptibility genes and endotoxin exposure) and to derive a comprehensive risk score, that is appropriate for use in primary health care and allows for efficient planning of early preventive strategies. Baseline examination includes a questionnaire evaluating known risk factors for wheezing illnesses; anthropometric measurements; measurements of infant and parental lung function; and sampling of infant and parental DNA. Participants will be followed for respiratory events using data from a daily respiratory symptom questionnaire; visits to the general practitioner (primary health care visits, drugs prescriptions and hospital referral); viral sampling during wheezing episodes; and house dust sampling. Based on actual neonatal care practice and embedded in a larger epidemiological study, the Utrecht Health Project, WHISTLER will provide an unique framework to address issues in childhood respiratory disease that are currently insufficiently understood. In particular, WHISTLER will provide a well-balanced view on the prognostic power of neonatal lung function and genetic and environmental factors (including viral infections and endotoxin exposure) to predict wheezing illnesses from birth to young adulthood and beyond. In the scope of prevention, WHISTLER is expected to support the design of solid based prevention measures to reduce respiratory morbidity, mortality and associated costs, and to improve quality of life.

Activation of Human Eosinophils In Vitro by Respiratory Syncytial Virus

ABSTRACT: To determine the nature of the interaction between viruses and eosinophils, normodense eosinophils were separated from the blood of healthy volunteers and incubated in vitro with respiratory syncytial virus (RSV). After incubation for 2 h with the virus, 29.5 ± 15.8% of the eosinophils demonstrated specific binding of the virus to the cell membrane, as detected by fluorescent staining with an anti-RSV MAb. Superoxide production and leukotriene C4 release were measured as determinants of cell activation. Using a cytochrome c reduction assay, superoxide could be detected in the supernatant 30 min after exposure to RSV. Maximal release was reached at 3 h postexposure (5.88 ± 2.19 nmol cytochrome c reduction/5 × 105 cells). The virus-induced superoxide generation varied in magnitude among different subjects and ranged from 0.6 to 11.5 nmol cytochrome c reduction/5 × 105 cells. RSV also appeared to prime eosinophils to the effects of other known cell activators, as demonstrated by an increase in superoxide production upon subsequent stimulation of RSV-primed cells with phorbol-12-myristate-13-acetate (21.4 ± 5.8 versus 9.4 ± 2.7 nmol cytochrome c reduction/5 × 105 cells for primed and unprimed cells, respectively) (p < 0.04). RSV did not directly induce leukotriene C4 release from the eosinophils but primed the cells to exhibit a more vigorous response on subsequent challenge with the calcium ionophore A23187 (9.16 ± 1.04 versus 4.2 μ1.3 ng leukotriene C4/1 × 106 cells) (p < 0.005). These findings indicate that RSV can activate or prime eosinophils to release various inflammatory mediators. Such virus-induced effects on inflammatory cells may play a role in the pathogenesis of RSV bronchiolitis and may also be critical for the development of persistent airway hyperreactivity after viral infections.

Concurrent bacterial infection and prolonged mechanical ventilation in infants with respiratory syncytial virus lower respiratory tract disease

ObjectiveTo identify demographic, clinical, and laboratory variables predictive for a concurrent bacterial pulmonary infection in ventilated infants with respiratory syncytial virus (RSV) lower respiratory tract disease (LRTD) and investigate antimicrobial drug use.Design and settingRetrospective, observational study in a 14-bed pediatric intensive care unit.Patients82 infants younger than 1xa0year of age with a virologically confirmed RSV LRTD during 1996 – 2001, of whom 65 were mechanically ventilated.ResultsMicrobiological data were available from 38 ventilated infants, 10 of whom had a positive blood culture (n=1) or endotracheal aspirate (n=9) obtained upon admission to the pediatric intensive care unit (PICU). Infants with a positive culture had a lower mean gestational age but were otherwise demographically comparable to those with negative culture results. Infants with a positive culture were ventilated 4xa0days longer. Indicators for a concurrent bacterial infection were comparable between ventilated and nonventilated infants. Antimicrobial drugs were used in 95.1% of infants (100% of ventilated infants) with a mean duration of 7.8±0.3xa0days. The moment of initiation and duration of antimicrobial drug treatment varied considerably.ConclusionsWe observed in ventilated infants a low occurrence of concurrent bacterial pulmonary infection, but infants with positive cultures needed prolonged ventilatory support. Improvement in the diagnosis of a pulmonary bacterial infection is warranted to reduce the overuse of antimicrobial drugs among ventilated infants with RSV LRTD and to restrict these drugs to the proper patients.