Opportunities for assessing ex vivo neutrophil extracellular trap formation and blood citrullinated histone h3 levels in risk evaluation and stratification in children with residual post-tuberculosis pulmonary changes

Background: Residual pulmonary changes may develop in children after tuberculosis treatment, contributing to the risk of disease recurrence. This highlights the relevance of non-invasive laboratory diagnostic approaches for risk assessment and stratification.

Aim: The work aimed to assess the ex vivo ability of neutrophil leukocytes isolated from blood to form neutrophil extracellular traps in response to nonspecific antigenic stimulation in children with post-tuberculosis pulmonary changes, in relation to the in vivo level of citrullinated histone H3 (citH3) in blood.

Methods: The study groups included a control group of healthy children aged 4 to 7 years (n = 26) and a group of children with residual post-tuberculosis changes (Post-TB) aged 4 to 14 years (n = 18). Eligibility criteria: absence of concomitant chronic somatic, infectious, or autoimmune diseases. Neutrophils isolated from peripheral blood were stimulated with a polybacterial agent. Neutrophil extracellular traps formation was assessed using fluorescence microscopy. The level of citrullinated histone H3 was measured using enzyme-linked immunosorbent assay. Differences between groups were considered significant at p < 0.05 and evaluated using the Mann–Whitney and Kruskal–Wallis tests, followed by post-hoc analysis. The Post-TB group was divided into subgroups with low (Post-TB-L) and high (Post-TB-H) neutrophil extracellular traps formation capacity.

Results: In the Post-TB group, the proportion of thread-like extracellular traps and the total proportion of extracellular traps were significantly higher than in the control group (p = 0.0016 and p = 0.0035, respectively). The concentration of citrullinated histone H3 in the Post-TB group was also higher than in the control group (p = 0.0101). No differences were observed between the groups in terms of cloud-like neutrophil extracellular traps (p = 0.8047). In the Post-TB-H subgroup, the proportion of thread-like extracellular traps and total extracellular traps was higher than in the control group (p_post-hoc = 0.00002 and p_post-hoc < 0.0001, respectively). In the Post-TB-L subgroup, the proportion of thread-like neutrophil extracellular traps was lower than in the Post-TB-H subgroup (p_post-hoc = 0.0021). Blood citrullinated histone H3 levels in the Post-TB-H subgroup were higher than in the control group (p_post-hoc = 0.0105) and the Post-TB-L subgroup (p_post-hoc = 0.0292). Spearman’s correlation coefficient between the proportion of thread-like extracellular traps and blood citrullinated histone H3 concentration was r = 0.711 (p = 0.0006).

Conclusion: Neutrophil ability to form neutrophil extracellular traps in children with post-tuberculosis pulmonary changes shows distinct features. Research in this area may prove useful for personalized risk assessment of tuberculosis recurrence.