Changes in Serum IgA Antibody Levels against the Glycopeptidolipid Core Antigen during Antibiotic Treatment of Mycobacterium avium Complex Lung Disease

Abstract

We evaluated serial changes in the levels of serum immunoglobulin A (IgA) antibody to the glycopeptidolipid (GPL) core antigen during antibiotic treatment in 57 patients with Mycobacterium avium complex (MAC) lung disease at baseline (T0) and after 3 months (T3) and 6 months (T6) of treatment. The median patient age was 59 years, and 37 (65%) patients were women. The etiologic organisms included M. avium in 32 (56%) patients and M. intracellulare in 25 (44%) patients. Seven (12%) patients had the fibrocavitary form of the disease on computed tomography. After 12 months of treatment, 42 (74%) patients had a favorable response to treatment, whereas 15 (26%) patients had an unfavorable response to treatment defined as the absence of sputum culture conversion within 12 months of treatment. The initial median serum anti-GPL IgA levels in the 57 patients was 3.50 U/mL, and the antibody levels at T0 (median 3.50 U/mL), T3 (median 2.71 U/mL), and T6 (median 2.61 U/mL) were significantly decreased following treatment (P ＜ 0.001). The results of the multivariate analysis indicated that an initially elevated anti-GPL IgA level (＞ 3.50 U/mL) was associated with an unfavorable response (P = 0.049). Our data suggest that elevated anti-GPL IgA levels may reflect disease activity and may help predict treatment response in patients with MAC lung disease.