Louis Bont

Respiratory syncytial virus and recurrent wheeze in healthy preterm infants

BACKGROUND Respiratory syncytial virus (RSV) infection is associated with subsequent recurrent wheeze. Observational studies cannot determine whether RSV infection is the cause of recurrent wheeze or the first indication of preexistent pulmonary vulnerability in preterm infants. The monoclonal antibody palivizumab has shown efficacy in preventing severe RSV infection in high-risk infants. METHODS In the double-blind, placebo-controlled MAKI trial, we randomly assigned 429 otherwise healthy preterm infants born at a gestational age of 33 to 35 weeks to receive either monthly palivizumab injections (214 infants) or placebo (215 infants) during the RSV season. The prespecified primary outcome was the total number of parent-reported wheezing days in the first year of life. Nasopharyngeal swabs were taken during respiratory episodes for viral analysis. RESULTS Palivizumab treatment resulted in a relative reduction of 61% (95% confidence interval, 56 to 65) in the total number of wheezing days during the first year of life (930 of 53,075 days in the RSV-prevention group [1.8%] vs. 2309 of 51,726 days [4.5%] in the placebo group). During this time, the proportion of infants with recurrent wheeze was 10 percentage points lower in patients treated with palivizumab (11% vs. 21%, P=0.01). CONCLUSIONS In otherwise healthy preterm infants, palivizumab treatment resulted in a significant reduction in wheezing days during the first year of life, even after the end of treatment. These findings implicate RSV infection as an important mechanism of recurrent wheeze during the first year of life in such infants. (Funded by Abbott Laboratories and by the Netherlands Organization for Health Research and Development; MAKI Controlled Clinical Trials number, ISRCTN73641710.).

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

BACKGROUND Respiratory 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. METHODS To 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. RESULTS SNPs 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). CONCLUSION SNPs in innate immune genes are important in determining susceptibility to RSV bronchiolitis.

Cord Blood Vitamin D Deficiency is Associated With Respiratory Syncytial Virus Bronchiolitis

BACKGROUND: Respiratory syncytial virus (RSV) is the most important pathogen causing severe lower respiratory tract infection (LRTI) in infants. Epidemiologic and basic studies suggest that vitamin D may protect against RSV LRTI. OBJECTIVE: To determine the association between plasma vitamin D concentrations at birth and the subsequent risk of RSV LRTI. DESIGN: A prospective birth cohort study was performed in healthy term neonates. Concentrations of 25-hydroxyvitamin D (25-OHD) in cord blood plasma were related to RSV LRTI in the first year of life, defined as parent-reported LRTI symptoms in a daily log and simultaneous presence of RSV RNA in a nose-throat specimen. RESULTS: The study population included 156 neonates. Eighteen (12%) developed RSV LRTI. The mean plasma 25-OHD concentration was 82 nmol/L. Overall, 27% of neonates had 25-OHD concentrations <50 nmol/L, 27% had 50-74 nmol/L and only 46% had 25-OHD 75 nmol/L. Cord blood 25-OHD concentrations were strongly associated with maternal vitamin D3 supplementation during pregnancy. Concentrations of 25-OHD were lower in neonates who subsequently developed RSV LRTI compared with those who did not (65 nmol/L versus 84 nmol/L, P = .009). Neonates born with 25-OHD concentrations <50 nmol/L had a sixfold (95% confidence interval: 1.6-24.9; P = .01) increased risk of RSV LRTI in the first year of life compared with those with 25-OHD concentrations ≥75 nmol/L. CONCLUSIONS: Vitamin D deficiency in healthy neonates is associated with increased risk of RSV LRTI in the first year of life. Intensified routine vitamin D supplementation during pregnancy may be a useful strategy to prevent RSV LRTI during infancy.

Association of Severe Respiratory Syncytial Virus Bronchiolitis with Interleukin-4 and Interleukin-4 Receptor α Polymorphisms

The association of variants of genes encoding interleukin (IL)-4 and the IL-4 receptor alpha chain (IL-4Ralpha) with respiratory syncytial virus (RSV) bronchiolitis was examined in hospitalized infants. Polymorphisms in IL-4 (C-590T) and IL-4Ralpha (I50V and Q551R) were genotyped by restriction fragment-length polymorphism analysis. Control subjects included parents of the hospitalized children (for the transmission/disequilibrium test), and a random population sample (for the case-control study). Results were also analyzed in a combination of these 2 tests, using Fishers method. The IL-4 590T allele was found more frequently among children hospitalized with RSV than expected in the case-control (odds ratio [OR], 1.43; P=.04) and combination (OR, 1.41; P=.02) tests. Among children who were >6 months old when they were hospitalized, compared with the control group or with the <6 months old who were hospitalized for RSV infection, higher frequencies of both the IL-4 590T allele and the IL-4Ralpha R551 allele were found. These results indicate that gain-of-function variants of T helper type 2 cytokine genes may play a role in increasing the severity of RSV disease, which appears more pronounced after the first half-year of life.

Down Syndrome: A Novel Risk Factor for Respiratory Syncytial Virus Bronchiolitis— A Prospective Birth-Cohort Study

OBJECTIVES. Respiratory syncytial virus is the single-most important cause of lower respiratory tract infections in children. Preterm birth and congenital heart disease are known risk factors for severe respiratory syncytial virus infections. Although Down syndrome is associated with a high risk of respiratory tract infections, little is known about the incidence of respiratory syncytial virus infections in this group. The aim of our study was to determine the incidence of respiratory syncytial virus lower respiratory tract infection–associated hospitalization among children with Down syndrome. PATIENTS AND METHODS. We performed a retrospective observational study and a prospective nationwide birth-cohort study of children with Down syndrome. The retrospective cohort comprised 176 children with Down syndrome. A birth cohort of 219 children with Down syndrome was prospectively followed until 2 years of age. All 276 siblings of the birth cohort were used as controls. RESULTS. Of the 395 patients with Down syndrome, 180 (45.6%) had a known risk factor for severe respiratory syncytial virus infections; 39 (9.9%) of these were hospitalized for respiratory syncytial virus lower respiratory tract infections. Two control children (0.7%) versus 9 term children with Down syndrome without congenital heart disease (7.6%) were hospitalized for respiratory syncytial virus lower respiratory tract infections. The median duration of hospitalization was 10 days; mechanical ventilation was required for 5 children (12.8%). CONCLUSIONS. This is the first study, to our knowledge, to demonstrate that Down syndrome is a novel independent risk factor for severe respiratory syncytial virus lower respiratory tract infections. These findings should prompt studies to investigate possible mechanisms that underlie severe respiratory syncytial virus lower respiratory tract infections in children with Down syndrome. The effect of respiratory syncytial virus prophylaxis in this specific population needs to be established.

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.

Local Interferon‐γ Levels during Respiratory Syncytial Virus Lower Respiratory Tract Infection Are Associated with Disease Severity

To investigate the role of cell-mediated immunity during respiratory syncytial virus (RSV) infection, interferon (IFN)-gamma and interleukin (IL)-10 levels in nasopharyngeal secretions were measured in infants with lower respiratory tract infection (LRTI) caused by RSV. A novel technique was used to measure in vivo cytokine levels in nasopharyngeal aspirates (NPAs). Cytokine levels in the NPAs of 17 mechanically ventilated infants and 43 nonventilated hospitalized infants were compared. As expected, mechanically ventilated infants were significantly younger than nonventilated infants (7 vs. 14 weeks). IFN-gamma levels were above the limit of detection in the NPAs of 3 (18%) mechanically ventilated infants and in the NPAs of 26 (60%) nonventilated infants. IL-10 levels in the NPAs of mechanically ventilated and nonventilated infants were comparable. It is hypothesized that maturation-related mechanisms have a key role in the development of RSV LRTI that results in mechanical ventilation.

Disease severity and viral load are correlated in infants with primary respiratory syncytial virus infection in the community

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, with remarkable variability in disease severity. Factors determining severity of disease in previously healthy infants are still unclear. It was hypothesized that disease severity is correlated with viral load in primary RSV infection. Infants of a healthy birth cohort were included at signs of their first respiratory tract infection. Nasopharyngeal aspirate was obtained within 48–96 hr and disease severity was assessed with a previously published severity scoring model. PCR was applied to test the aspirates in a semi‐quantitative way for the presence of 10 respiratory pathogens. In case of multiple infection, the pathogen with the highest load was defined as the primary pathogen. The correlation between disease severity and viral load was analyzed. A total of 82 infants were included over a period of 2 years. Median age at first respiratory tract infection was 3 months. Pathogens were detected in 77 (94%) infants; more than one pathogen was detected in 35 (43%) infants. RSV was present in aspirates of 30 infants; in 16 aspirates RSV was the primary pathogen. A negative correlation between RSV CT‐value and disease severity was found in all RSV cases (ρ = −0.52, P = 0.003) and in cases with RSV as the primary pathogen (ρ = −0.54, P = 0.03). In conclusion, this is the first report on viral loads in previously healthy infants with RSV infection in the community. Disease severity correlated positively with viral load during primary RSV infection. J. Med. Virol. 82: 1266–1271, 2010.

EMERGENCE AND EPIDEMIC OCCURRENCE OF ENTEROVIRUS 68 RESPIRATORY INFECTIONS IN THE NETHERLANDS IN 2010

Following an increase in detection of enterovirus 68 (EV68) in community surveillance of respiratory infections in The Netherlands in 2010, epidemiological and virological analyses were performed to investigate the possible public health impact of EV68 infections. We retrospectively tested specimens collected from acute respiratory infections surveillance and through three children cohort studies conducted in The Netherlands from 1994 through 2010. A total of 71 of 13,310 (0.5%) specimens were positive for EV68, of which 67 (94%) were from symptomatic persons. Twenty-four (34%) of the EV68 positive specimens were collected during 2010. EV68-positive patients with respiratory symptoms showed significantly more dyspnea, cough and bronchitis than EV68-negative patients with respiratory symptoms. Phylogenetic analysis showed an increased VP1 gene diversity in 2010, suggesting that the increased number of EV68 detections in 2010 reflects a real epidemic. Clinical laboratories should consider enterovirus diagnostics in the differential diagnosis of patients presenting with respiratory symptoms.

Influence of Promoter Variants of Interleukin-10, Interleukin-9, and Tumor Necrosis Factor–α Genes on Respiratory Syncytial Virus Bronchiolitis

Previously, we reported genetic associations between severe respiratory syncytial virus (RSV) bronchiolitis in infants and polymorphisms in the interleukin (IL)-4 and IL-4 receptor alpha (IL-4Ralpha) genes, providing evidence for involvement of T helper type 2 cytokines in the pathogenesis of RSV bronchiolitis. We expanded our studies to polymorphisms in genes encoding IL-9, IL-10, and tumor necrosis factor (TNF)-alpha, using both a transmission/disequilibrium test and a case-control approach. Children homozygous for the IL-10 -592C or -592A allele had a higher risk of hospitalization for RSV bronchiolitis than did heterozygous carriers (odds ratio [OR], 1.73 vs. 2.55; 95% confidence interval [CI], 1.13-2.66 vs. 1.21-5.39). In children hospitalized at < or =6 months of age, a significant association between RSV bronchiolitis and the IL-10 -592C allele was found (OR, 1.61; 95% CI, 1.10-2.35). No significant associations of TNF-alpha and IL-9 polymorphisms with RSV bronchiolitis were observed. We also explored the interactions between different polymorphisms and found an interaction between the IL-4Ralpha Q551R and IL-10 C-592A polymorphisms.