Cathelicidin levels in nasal secretions are associated with the severity of acute bronchiolitis

Nasal cathelicidin is expressed in early life and is increased during mild, but not severe respiratory syncytial virus infection

Respiratory syncytial virus is the major cause of acute lower respiratory tract infections in young children, causing extensive mortality and morbidity globally, with limited therapeutic or preventative options. Cathelicidins are innate immune antimicrobial host defence peptides and have antiviral activity against RSV. However, upper respiratory tract cathelicidin expression and the relationship with host and environment factors in early life, are unknown. Infant cohorts were analysed to characterise early life nasal cathelicidin levels, revealing low expression levels in the first week of life, with increased levels at 9 months which are comparable to 2-year-olds and healthy adults. No impact of prematurity on nasal cathelicidin expression was observed, nor were there effects of sex or birth mode, however, nasal cathelicidin expression was lower in the first week-of-life in winter births. Nasal cathelicidin levels were positively associated with specific inflammatory markers and demonstrated to be associated with microbial community composition. Importantly, levels of nasal cathelicidin expression were elevated in infants with mild RSV infection, but, in contrast, were not upregulated in infants hospitalised with severe RSV infection. These data suggest important relationships between nasal cathelicidin, upper airway microbiota, inflammation, and immunity against RSV infection, with interventional potential.

Association of vitamin D with disease severity in infants with bronchiolitis

Vitamin D's role in immune system regulation and its contribution to host defenses against respiratory infections may have implications for bronchiolitis pathophysiology. This cross-sectional study aimed to determine the association between the clinical severity of bronchiolitis and serum vitamin D levels in infants. Infants aged 1 month to 12 months, diagnosed with bronchiolitis, and healthy controls attending routine immunization were enrolled. Baseline characteristics were recorded, including clinical details, bronchiolitis severity, and course during hospital stay. Bronchiolitis severity score (BSS) was used to score the severity. A 1-2 ml serum sample was obtained for vitamin D levels estimation. The median age of cases (n = 64; 65.6% male) was 5 [3, 8] months, and that of the control group (n = 30) was 3 [2, 9] months. No statistically significant differences were observed between the two groups in age, gender, weight, mode of delivery, family history of atopy/asthma, feeding pattern, smoke exposure, and daily vitamin D supplementation. The median vitamin D levels were not significantly different between the groups (p = 0.68). Among infants with bronchiolitis, 62.5% had vitamin D insufficiency (≤ 20 ng/ml). A significantly higher median BSS indicates that infants with vitamin D insufficiency exhibited more severe disease (p = 0.019). Although a negative correlation between BSS and vitamin D levels was noted, it did not reach statistical significance [rs = (-)0.17; p = 0.16].

CONCLUSION

 Infants with Vitamin D insufficiency experienced more severe bronchiolitis with elevated BSS scores. It highlights the potential role of vitamin D deficiency in severe bronchiolitis.

WHAT IS KNOWN

• Vitamin D level is low in infants with bronchiolitis.

WHAT IS NEW

• Infant with low vitamin D level experienced more severe bronchiolitis.

Vitamin D and Respiratory Diseases : Based on 11th Dr. I. C. Verma Excellence in Research Award for Young Pediatricians Delivered as Oration on 15th Oct. 2023

The significance of Vitamin D has been appreciated beyond bone health and calcium metabolism. The importance of Vitamin D in respiratory health has been recognized due to its immunomodulatory and anti-microbial properties. The hypothesis is that Vitamin D could have a significant role in the pathogenesis of respiratory diseases and may represent a novel preventive and therapeutic strategy. Furthermore, enumerable observational studies established the association of Vitamin D deficiency with respiratory diseases such as asthma, bronchiolitis, pneumonia, tuberculosis, etc. However, experimental studies have not shown the encouraging results. This brief review will summarize and discuss the synthesis and metabolism of Vitamin D, the prevalence of Vitamin D deficiency in children, its role in the pathogenesis of various childhood respiratory diseases, and an overview of the therapeutic trials assessing the role of Vitamin D supplementation in childhood respiratory diseases.

The ratio of serum LL-37 levels to blood leucocyte count correlates with COVID-19 severity

Beneficial effects of vitamin D on COVID-19 progression have been discussed in several studies. Vitamin D stimulates the expression of the antimicrobial peptide LL-37, and evidence shows that LL-37 can antagonize SARS-CoV-2. Therefore, we investigated the association between LL-37 and vitamin D serum levels and the severity of COVID-19. To this end, 78 COVID-19 patients were divided into 5 groups according to disease severity. We determined serum levels of LL-37, vitamin D, and routine laboratory parameters. We demonstrated a correlation of CRP, IL-6, PCT, leukocyte count, and LDH with the severity of COVID-19. Our study did not demonstrate a direct relationship between serum levels of LL-37 and vitamin D and the severity of COVID-19. LL-37 is produced by granulocytes and released at the site of inflammation. Therefore, the analysis of LL-37 in broncho-alvelolar lavage rather than in patient serum seems critical. However, since LL-37 is produced by granulocytes, we determined serum LL-37 levels as a function of leukocyte count. The LL-37/leukocyte count ratio correlates highly significantly inversely proportional with COVID-19 severity. Our results indicate that the LL-37/leukocyte count ratio could be used to assess the risk of COVID-19 progression as early as hospital admission.