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

BACKGROUND: Chlamydia 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. METHODS: Pediatric 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. RESULTS: None 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). CONCLUSION: Our 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.