Efficacy of Immunization with Outer Membrane Proteins for Induction of Pulmonary Clearance of Nontypeable Haemophilus Influenzae in a Rat Respiratory Model

Three strains of nontypeable Haemophilus influenzae namely NTHi-I , NTHi-II and NTHi-III were isolated from the sputum of patients with bronchitis and identified by biochemical, serological and electron microscopy. The polypeptide patterns of isolates were compared and found to have similar sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) polypeptide patterns, although some of the bands were specific in some strains. A similar comparison was made on extracted outer membrane proteins (OMPs) on the above mentioned strains, using Triton X-100 and sodium dodecyle sulphate (SDS). It was found that the polypeptides with molecular weights of 70, 42, 33 and 27 KDa were identified as P1, P2, P4 and P5 respectivly. The protein estimation of crude OMPs from the three strains were calculated, and OPM-I prepared from NTHi–I showed the highest amount of protein and was chosen for its immunogenicity in a rat respiratory model. The efficacy of immunization with OMP was determined by enhancement of pulmonary clearance of live bacteria in the rat lung. A significant protective immune response induced by OMP was observed by enhanced respiratory clearance of nontypeable H. influenzae following mucosal immunization.