2221. Chlamydia pneumoniae (Cpn) Induces IFN-γ Responses in Peripheral Blood Mononuclear Cells (PBMC) from Pediatric and Adult Asthma Patients: Effects of Age and Inhaled Corticosteroid Use

Abstract

BackgroundChlamydia pneumoniae (Cpn) is unique in its ability to cause chronic infections, potentially triggering asthma exacerbations as well as subsequent asthma development. Th1-mediated immunity and IFN-γ are critical for clearing chlamydial infections. Persistent or recent Cpn infection may be identified in vitro by detecting T-helper cytokine IFN-γ produced by peripheral blood mononuclear cells (PBMC) stimulated by Cpn. Inhaled corticosteroids (ICS) may have an inhibitory effect on IFN-γ. Prior studies have shown increased Th2 responses upon in vitro Cpn stimulation with increased age. Our aim was to determine whether age and inhaled corticosteroid (ICS) use affect Cpn-induced PBMC produced IFN-γ levels.MethodsPediatric and adult subjects with (n = 23) and without (n = 10) asthma were enrolled. PBMC obtained from all subjects were stimulated with Cpn (MOI = 0.1 x48h) in vitro. IFN-γ levels in culture supernatants were determined by ELISA and reported as pg/mL. Nasopharyngeal (NP) swabs were tested for Cpn using Real-Time PCR. Statistical analysis for continuous variables was performed using the Mann–Whitney U test.ResultsNone of the subjects were positive for Cpn by PCR on NP swab. Levels of IFN-γ produced by PBMC stimulated by Cpn were similar between asthmatic vs. control subjects (41.7 vs. 68.8, respectively; P = 0.72) and between pediatric and adult subjects with asthma (IFN-γ 54 vs. 20.1 respectively, P = 0.95). Pediatric subjects with asthma who received ICS had lower IFN-γ levels than those who did not (median IFN-γ 25.5 vs. 209; P = 0.003).ConclusionOur finding of lower IFN-γ levels among asthma patients on ICS compared with those not on ICS suggests that ICS use may dampen the systemic inflammatory response. While we did not find a statistically significant difference between pediatric and adult age groups in this pilot study, there was a trend to higher Cpn-induced IFN-γ levels among younger pediatric subjects. Future prospective studies should further define predictors of diminished IFN-γ responses in patients with asthma.Disclosures All authors: No reported disclosures.