Lactoferrin-DNA complex detection to evaluate plasma neutrophil extracellular traps of patients with severe influenza A (H1N1)

Objective To establish a relative quantitative assay for lactoferrin-DNA complex, and to assess the levels of neutrophil extracellular traps (NETs)in plasma samples from patients with severe influenza A (H1N1) and other pathogen infectious diseases. Methods Plasma samples with clear DNA content were serially diluted as a standard, and the level of lactoferrin-DNA complex in plasma was determined by Enzyme-linked immunosorbent assay (ELISA). The lactoferrin-DNA ELISA method was used to compare the difference of plasma lactoferrin-DNA complex between 19 patients with severe influenza A (H1N1) and 19 blood donors (control group). Results Level of plasma lactoferrin-DNA complex of patients in severe influenza A (H1N1) was positively correlated with that of cfDNA (cell-free DNA) and histone-DNA complex, respectively (r = 0.6763, P < 0.0001; r = 0.756, P < 0.0001). The plasma lactoferrin-DNA complex content in patients with severe influenza A (H1N1) was 2.082 (1.169, 5.021) μg/ml, which was significantly higher than that of the controls [0.233 (0.170, 0.376) μg/ml, P < 0.0001], and positively correlated with Acute Physiological and Chronic Health Evaluation Ⅱ score (APACHE Ⅱ score) (r = 0.7379, P = 0.0005). Conclusion Plasma lactoferrin-DNA complex level could be used to assess NETs level in patients with severe influenza A (H1N1). Key words: Severe influenza A (H1N1); Lactoferrin-DNA complex; Neutrophil extracellular traps; Enzyme-linked immunosorbent assay