Target Advantages Drawbacks Preliminary data
Outer Membrane Protein - P1 Significant areas of conservation among typeable and nontypeable strains Only 1 epitope in common between 28 strains tested Rabbit antisera presented bactericidal activity against NTHi [42].
Outer Membrane Protein - P2 reveals the presence of both heterogeneous and conserved surface-exposed loops of the P2 molecule among strains
Bactericidal antibodies to P2 are present in normal human sera
Immunization with P2, did not enhance clearance as much as did immunization with P1 or P6. Induce the synthesis of antibodies protective against experimental Hib disease. Immunization with a P2-LOS complex in mice and purified P2 preparation in a rat model showed enhanced pulmonary clearance of a homologous strain of NTHi [22,43,44].
Outer Membrane Protein - P4 One surface-exposed epitope was conserved Did not presented effective antigenicity After in vitro and vivo trials did not demonstrated effective antigenicity [36]
Outer Membrane Protein - P6 1 surface epitope common to all strains, conserved among encapsulated and nonencapsulated H. influenzaestrains Cannot be a transmembrane protein and is not conserved in all NTHi strains [49]. Mice and rabbits have been shown to produce bactericidal antibodies after systemic immunization with P6 and recombinant P6 [46-48].
lipooligosaccharide (LOS)-tetanus toxoid (TT) Protective against NTHi strains Not yet tested in children Well tolerated in adults [50]
NTHi OMV Protective against NTHi strains. Various heterologous antigens in the vesicules Not yet tested in humans Tests in mice demonstrate a cross-protective immunization [51].
Table 3: Novel Membrane proteins target in Haemophilus influenza.