Weakly acidic pH reduces inflammatory cytokine expression in airway epithelial cells.

BACKGROUND: Aspiration lung disease (ALD) is a common cause of respiratory morbidity in children and adults with severe neurodisability (sND). Recent studies suggest that chronic microaspiration of gastric contents is associated with mild rather than low, airway acidification. We investigated inflammatory responses to infection by airway epithelial cells (AECs) exposed to weakly acidic media. METHODS: Using pH measurements from children with sND at high risk of ALD as a guide, we incubated AECs in weakly acidic (pH5.5-7.4) media alone; in combination with lipopolysaccharide (LPS); or prior to LPS stimulation at normal pH. Interleukin (IL) -6 and IL-8 expression were measured. RESULTS: IL-6/8 expression in AECs simultaneously exposed to weakly acidic media and LPS for 4 h was reduced with no effect on cell viability. Pre-incubation of AECs at weakly acidic pH also reduced subsequent LPS-induced cytokine expression. Suppression of inflammation was greatest at lower pHs (pH 5.5-6.0) for prolonged periods (16/24 h), but this also adversely affected cell viability. CONCLUSION: AEC inflammatory responses to bacterial stimuli is markedly reduced in a mildly acidic environment.

Respiratory syncytial virus infection of airway epithelial cells, in vivo and in vitro, supports pulmonary antibody responses by inducing expression of the B cell differentiation factor BAFF.

BACKGROUND: The mechanisms regulating antibody expression within the human lung during airway infection are largely unknown. In this study, our objectives were to determine if infection with respiratory syncytial virus (RSV) upregulates expression of the B cell differentiation factors A proliferation inducing ligand (APRIL) and B cell activating factor of the TNF family (BAFF), if this is a common feature of viral airway infection, and how this is regulated in human airway epithelial cells. METHODS: We measured BAFF and APRIL protein expression in bronchoalveolar lavage (BAL) fluid from infants with severe RSV disease, and healthy control children, and in nasopharyngeal aspirates from preschool children with other single respiratory viral infections. We also measured mRNA expression in bronchial brushings from RSV-infected infants, and in RSV-infected paediatric primary airway epithelial cell cultures (pAEC). Beas-2B cell cultures were used to examine mechanisms regulating BAFF expression. RESULTS: BAFF protein and mRNA were elevated (in marked contrast with APRIL) in BAL and bronchial brushings, respectively, from RSV-infected infants. BAFF protein was also found in upper airway secretions from children with human metapneumovirus, H1N1, bocavirus, rhinovirus, RSV and Mycoplasma pneumoniae infection. BAFF mRNA and protein were expressed following in vitro RSV infection of both pAEC and Beas-2B cultures, with mRNA expression peaking 12-h postinfection. BAFF induction was blocked by addition of a neutralising anti-interferon-ß antibody or palivizumab. CONCLUSIONS: BAFF, produced through an interferon-ß-dependent process, is a consistent feature of airway infection, and suggests a role for the airway epithelia in supporting protective antibody and B cell responses in the lung.

Primary airway epithelial cultures from children are highly permissive to respiratory syncytial virus infection.

BACKGROUND: Respiratory syncytial virus (RSV) infection of airway epithelial cells (AECs) is an important initial event in RSV bronchiolitis. AEC immunological responses are thought to be critical in driving the subsequent inflammation in the airway. This study examined viral replication, cytotoxicity and cytokine production in cultures of primary AECs from children compared with responses to RSV infection in an immortalised epithelial cell line and to those from infants with RSV bronchiolitis. METHODS: RSV replication, proinflammatory cytokine responses and cytotoxicity in RSV-infected primary AEC cultures derived from bronchial brushings from the lungs of children were compared with those seen in BEAS-2B cultures, as well as AECs and bronchoalveolar lavage fluid collected from children with and without RSV bronchiolitis. RESULTS: Viral replication, cytotoxicity and inflammatory cytokine production were greater in primary AEC cultures than in BEAS-2B cells. Different response patterns were observed, with RSV infection of primary AEC cultures causing distinct peaks of viral replication and matched cytotoxic responses. Some primary AEC culture immunological responses, such as interleukin 8, were similar in magnitude to those seen in clinical samples from the lungs of children with RSV bronchiolitis. Although variable amounts of RSV were detected by PCR in freshly isolated primary AECs, RSV was not detected by immunocytochemistry. CONCLUSION: This is one of the first studies to examine comprehensively the responses to RSV infection in primary AEC cultures from children and shows marked differences from those of a commercially available immortalised human cell line but reassuring similarities to results found in vivo. This suggests that future work investigating responses of AECs to RSV infection should use primary AEC cultures.

Assessing the Liverpool Respiratory Symptom Questionnaire in children with cystic fibrosis.

Monitoring respiratory status in cystic fibrosis (CF) is challenging, particularly in young children. We aimed to test whether the Liverpool Respiratory Symptom Questionnaire (LRSQ) could distinguish well, pre-school and older children with and without CF, whether it could distinguish well and unwell children with CF and, finally, whether LRSQ scores in older children with CF correlated with established measures of disease severity. 20 stable pre-school children with CF had significantly higher total LRSQ scores than 51 pre-school controls, and higher scores in two out of eight domains. Similarly, 21 stable 6- to 12-yr-old children with CF had higher total scores than 97 6- to 12-yr-old controls, and higher scores in seven out of eight domains. In older children with CF, LRSQ scores correlated negatively with Shwachman score and forced expiratory volume in 1 s (r = -0.58, p < 0.001, n = 31; and r = -0.46, p < 0.010, n = 34, respectively). Within the CF group, patients who cultured Pseudomonas aeruginosa, who used more "back-up" antibiotics or whose school attendance was lower also had higher LRSQ scores. The LRSQ differentiates well children from those with CF in both pre-school and the 6- to 12-yr-old age group, even at a point of stability. It also differentiates stable from unwell children with CF, and scores correlate with other measures of respiratory disease, highlighting its potential as a clinical monitoring tool in paediatric CF.