Surfactant Protein A Recognizes Outer Membrane Protein OprH on Pseudomonas aeruginosa Isolates From Individuals With Chronic Infection

Surfactant protein A (SP-A) plays a critical role in the clearance of Pseudomonas aeruginosa from the lung. However, there is limited information about the interaction of this protein with P. aeruginosa isolates from individuals with cystic fibrosis (CF). We characterized the interplay between SP-A and a collection of isogenic sequential isolates from 7 patients with CF. We identified outer membrane protein OprH as a novel ligand for SP-A on P. aeruginosa. The last-available (late) isolates from patients with CF bound significantly less SP-A than their respective first-available (early) isolates. This difference could be associated with a reduction in the expression of OprH. Binding of SP-A to OprH promoted phagocytic killing; thus, late CF isolates were at least 2-fold more resistant to SP-A-mediated killing by human macrophages than their respective early isolates. We postulate that the reduction of OprH expression is a previously unrecognized adaptation of P. aeruginosa to the lung of individuals with CF that facilitates the escape of the microorganism from SP-A-mediated phagocytic killing.