Associations between vitamin D and antimicrobial peptide LL-37 in children with respiratory syncytial virus pneumonia

Abstract

Abstract Objective We investigated the effects of serum vitamin D and antimicrobial peptide LL-37 levels on the respiratory syncytial virus (RSV) pneumonia in children. Methods From January 2021 to December 2021, 81 children with RSV pneumonia (case group) were divided into severe group (n = 29) and normal group (n = 52) according to the 2019 edition of the expert consensus on childhood pneumonia, while 45 health clinic checkup children were selected as controls. Serum 25-(OH)D levels were measured by electrochemiluminescence and serum LL-37 levels were measured by enzyme-linked immunosorbent assay. Levels and correlations between groups were then statistically analyzed. Results 25-(OH)D levels in the case group (91.25 ± 24.80 nmol/L) were significantly lower than in the healthy controls (104.91 ± 22.23 nmol/L, P < 0.01). LL-37 levels in the case group (323.81 ± 91.51 pg/mL) were higher than levels in the healthy controls (260.85 ± 38.48 pg/mL, P < 0.001). We identified a correlation between 25-(OH)D and LL-37 levels in the case group (r = 0.231, P = 0.04). We observed no significant differences in 25-(OH)D and LL-37 levels between affected children in winter and spring periods, and affected children in summer and autumn periods (P > 0.05). When common group compared with the severe group of RSV pneumonia, there were significant differences in LL-37 levels (t = -3.611, P = 0.001), white blood cell (WBC) ≥ 10×109/L (χ2 = 7.89, P < 0.01) and C-reaction protein (CRP) < 10 mg/L (χ2 = 4.71, P = 0.03) and there was no significant difference in the 25-(OH)D levels (t = -1.08, P > 0.05). Receiver-operating characteristic (ROC) curve analyses showed that the optimal critical serum LL-37 value was 384.24 pg/mL, and corresponding specificity and sensitivity values were 90.4% and 58.6%, respectively. Severe RSV pneumonia risk of LL-37 ≥ 384.24 pg/mL was significantly higher than that of the LL-37 < 384.24 pg/mL group (χ2 = 22.60, P < 0.001). Using multivariate logistic regression analysis, serum LL-37 ≥ 384.24 pg/mL (odds ratio (OR) = 17.127, P < 0.001), WBC ≥ 10×109/L (OR = 7.399, P < 0.01), and CRP < 10 mg/L (OR = 12.393, P = 0.02) may be risk factors for severe RSV pneumonia in children. Conclusions 25-(OH)D and LL-37 levels are involved in RSV pneumonia, with little seasonal correlations. High LL-37, WBC ≥ 10×109/L, and CRP < 10 mg/L levels are probably related to disease severity and may be used for disease evaluation.