Peptide and recombinant antigens for protection against bacterial middle ear infection.

Passive immunization of chinchillas with serum specific for either LB1 or for LPD-LB1 (f)(2,1,3) prior to challenge with heterologous NTHI isolates (relative to diversity in region three of P5-fimbrin), significantly inhibited the signs and incidence of otitis media (P < or = 0.01) induced by any of the challenge isolates. The ability of these antisera to induce total eradication of NTHI from the nasopharynx was not however equivalent among challenged cohorts. The data thus suggested that while early, complete eradication of NTHI from the nasopharynx was highly protective, reduction of the bacterial load to below a critical threshold level appeared to be similarly effective. Both immunogens thus remain strong vaccine candidates.