Background: Human neutrophil peptides 1-3 are endogenous cationic antimicrobial peptides implicated in host defense against microbes. The genes encoding human neutrophil peptides 1-3 (DEFA1/DEFA3) exhibit copy number variations. This study was designed to determine whether DEFA1/DEFA3 copy number variations conferred susceptibility to infection-induced complications such as severe sepsis.
Methods: This case-control study was performed in 179 patients with severe sepsis and 233 healthy blood donors and was replicated in an independent cohort of 112 cases and 118 controls. Plasma levels of human neutrophil peptides 1-3, tumor necrosis factor-alpha, interleukin-6, and interleukin-10 were detected.
Results: The genotype of DEFA1/DEFA3 with more than eight copies was more frequent in patients with severe sepsis than in controls (55.9% vs. 31.3%; P = 1.13 x 10, odds ratio 2.77, 95% confidence interval 1.85-4.16). After adjustment for age and gender, logistic regression analysis confirmed the association of the genotype of more than eight copies with an increased risk of severe sepsis (P = 2.25 x 10, odds ratio 2.66, 95% confidence interval 1.69-4.19). This established association was replicated in a second age- and gender-matched case-control cohort (P = 0.02, odds ratio 1.90, 95% confidence interval 1.11-3.27). Furthermore, compared with those with fewer copies, the patients carrying more than eight copies of DEFA1/DEFA3 presented significantly lower plasma levels of human neutrophil peptides 1-3, tumor necrosis factor-alpha, interleukin-6, and interleukin-10 (P = 0.039, 0.017, 0.030, and 0.029, respectively).
Conclusions: DEFA1/DEFA3 is an important genetic component participating in host immune response to severe sepsis. A higher copy number of DEFA1/DEFA3 (>8 copies) is significantly associated with the risk of severe sepsis.