2157. Low Interferon-γ and Interleukin-13 Levels in the Respiratory Tract are Related to Life-threatening Respiratory Syncytial Virus Infection in Previously Healthy Infants.

Abstract Background The mechanisms of interindividual susceptibility to respiratory syncytial virus (RSV) are not clearly understood. Viral load (VL), an exaggerated immune response or T-helper 2 (Th2) bias were postulated as playing a role in the severity RSV infection. We aimed analyze VL, cytokine profiles and their association with life-threatening disease (LTD). Methods Prospective cohort study including previously healthy full-term infants < 12 months old, hospitalized first infection 2017-2019. Nasopharyngeal aspirates performed on admission assess VL (by qRT-PCR) cytokines levels (using Bioplex panel). Cytokines grouped according functional classification: proinflammatory (TNF-α), regulatory (interleukin [IL]-10), Th1 (interfereron-γ [IFN-γ]), Th2 (IL-4, IL-5, IL-9, IL-13) Th17 (IL-17a). Patients defined have LTD when required admittance intensive care units ventilatory support. Results One hundred nineteen patients studied, 68 (57%) male; median age was 3 months. Nineteen (16%) developed LTD, no significant differences socioeconomic, pregnancy infant variables compared other cases. Virus subtypes related (p= 0.77). associated 0.51). had significantly lower IFN-γ (mean 0.08 pg/ml [standard deviation -SD- 0.06] vs. 0.32 [SD 0.4]; p= 0.001) IL-13 0.03 0.04] 0.05 0.07]; 0.02), fig 1. inversely correlated days hypoxemia (p< 0.001 0.002, respectively). did correlate duration symptoms before admission. No relationship observed between IFN-γ, age, sex breastfeeding. In 102 (86%) samples, IL-4 under limit quantitation. TNF-α, IL-10 e IL-17a LTD. interleukin-13 clinical outcome. Conclusion To our knowledge, this is relate low infants. 4-fold IFN-γ. may be result deficient rather than higher viral overactive response. These findings provide additional evidence for development preventive therapeutic strategies. Disclosures All Authors: reported disclosures.