Sequence stability of the gene encoding outer membrane protein P2 of nontypeable Haemophilus influenzae in the human respiratory tract.

Nontypeable Haemophilus influenzae (NTHI) is an important cause of lower respiratory tract infections in patients with chronic obstructive pulmonary disease. Recent findings suggest that the major outer membrane protein P2 should be reconsidered as a vaccine candidate for NTHI. A P2-based vaccine would require a relative degree of sequence stability of the gene encoding P2 (ompP2) during colonization. To characterize the sequence stability of ompP2 during colonization of the human respiratory tract, ompP2 genes from 13 sets of isolates that persisted in patients with chronic obstructive pulmonary disease (mean colonization, 7 months) were sequenced. In 9 sets of isolates, ompP2 did not change. Sequence changes were noted in 4 sets of isolates. Most of these changes occurred within areas of repetitive DNA, suggesting that this type of DNA has a role in antigenic variation of P2. The sequence of ompP2 is relatively stable during persistence of NTHI in the human host.