Plasma and BAL Fluid Concentrations of Antimicrobial Peptides in Patients With Mycobacterium avium- intracellulare Infection

Abstract

To investigate the roles of human alpha-defensin (HAD), human beta-defensin (HBD)-1, and HBD-2, novel antimicrobial peptides, in patients with Mycobacterium avium-intracellulare infection (MAI). The study included 25 patients (10 men) with MAI who visited our hospital between June 1998 and August 1999. In patients with pulmonary MAI, we measured HAD and HBD-1, and HBD-2 levels in plasma and in BAL fluid (BALF) by radioimmunoassay. Plasma concentrations of HAD and HBD-2 in those patients were higher than those in control subjects, whereas HBD-1 levels were similar to those in the control subjects. High levels of HAD and HBD-2, but not HBD-1, also were observed in the BALF of MAI patients. There was a positive correlation between HAD and interleukin (IL)-8 concentrations in the BALF of patients with MAI. BALF HBD-2 concentrations also correlated positively with those of plasma HBD-2 and BALF IL-1 beta in MAI patients. Patients with cavity formation on the chest roentgenogram had higher HAD and HBD-2 levels in their BALF than those of patients without cavity formation. Treatment with clarithromycin combined with two or three other antibiotics, including ethambutol, rifampicin, ofloxacin, or ciprofloxacin, for at least 6 months resulted in a significant fall in plasma HBD-2 concentrations in responders, but not in nonresponders. Our findings suggest that HAD and HBD-2 may participate in host defense and local remodeling of the respiratory tract in patients with MAI and that plasma HBD-2 levels may be a useful marker of disease activity in patients with pulmonary MAI.