MAPPING OF ANTIGENIC AND IMMUNOGENIC SITES OF HAEMOPHILUS-INFLUENZAE OUTER-MEMBRANE PROTEIN P6 USING SYNTHETIC LIPOPEPTIDES

The immune response to the P6 protein of Haemophilus influenzae was characterized with 24 synthetic icosapeptides and 45 dodecapeptides conjugated to the immune stimulator N-palmitoyl-S-[2,3-(bispalmitoyloxy)-(2RS)-propyl]-(R)-cysteinyl-(S)-serine. The antigenicity of these lipopeptides was investigated by enzyme-linked immunosorbent assays with rabbit anti-P6 serum. The epitopes of P6 protein were identified and localized within residues 31-46 and 59-70 and in the C-terminal part of the P6 protein. Mice were immunized with lipoicosapeptides without using additional adjuvants or carriers and the antibody titers were measured with isolated P6 protein and lipopeptides in a dot blot assay. Lipopeptides containing the sequence pattern QILDAHAA (P6 47-54) and the mouse B cell epitope GEYV (P6 43-46) induced high titers of anti P6 antibodies. These murine antibodies were able to neutralize the intact bacterium Haemophilus influenzae.