Diagnostic value of antibodies against pseudomonas aeruginosa in bronchoalveolar lavage fluid after lung transplantation

Abstract

Background. Pseudomonal airway colonization is a risk factor for chronic allograft dysfunction after lung transplantation (LTx). Pseudomonas aeruginosa exoproteases are involved in initiating colonization, and immune complexes directed against these proteases may activate innate immune responses.Objective. To investigate whether specific antibodies against pseudomonal proteases could be measured in bronchoalveolar lavage (BAL) fluid, whether they are associated with innate immune responses, and whether they could identify patients with chronic P aeruginosa colonization after LTx.Materials. and Methods. BAL fluid from 40 noncolonized and 25 chronically colonized LTx recipients was retrospectively assayed for IgG antibodies against P aeruginosa alkaline protease (AP), elastase (Ela), and exotoxin (Exo), and for BAL total and differential cell counts and IL-8 protein concentration.Results. BAL anti-Ela and anti-Exo antibody titers were significantly increased in colonized compared with noncolonized patients (P = .009 and P = .02, respectively), whereas anti-AP titers were comparable (P = .79). Antibody titers strongly correlated with each other, and anti-Ela and anti-Exo titers, but not anti-AP titers, also correlated with BAL total cellularity, neutrophilia, and IL-8 protein concentration. Anti-Ela antibodies demonstrated the greatest diagnostic value in receiver operating characteristic analysis to detect chronic airway colonization (P = .009), followed by anti-Exo (P = .02) and anti-AP (P = .79). A combination of all 3 antibodies resulted in overall sensitivity of 45% (95% confidence interval [CI], 29.3-61.5), specificity of 88% (95% CI, 68.8-97.5), and positive predictive value of 55% (95% CI, 38.5-70.7).Conclusion. P aeruginosa proteases in BAL may be associated with local innate immune responses, and could have the potential to enable detection of chronic colonization after LTx.