Carrier properties of a protein derived from outer membrane protein A of Klebsiella pneumoniae

We have recently cloned a new protein, recombinant P40 (rP40). When tested in vivo after conjugation to a B-cell epitope, rP40 induces an important an tibody response without the need for adjuvant. To characterize its potency, this carrier protein was coupled to a peptide derived from respiratory syn cytial virus attachment G protein (G1'). After immunization of mice with th e rP40-G1' conjugate, strong antipeptide antibodies were detected, whereas peptide alone was not immunogenic. To emphasize the carrier properties of r P40, a polysaccharide derived from Haemophilus influenzae type b (Hib) was coupled to it. Immunoglobulin G responses against the Hib polysaccharide we re observed after coupling to rP40. Interestingly, an antipeptide antibody response was observed despite preexisting anti-rP40 antibodies generated by preimmunization with rP40, In addition, rP40 compares well with the refere nce carrier protein, tetanus toroid (TT), since antibody responses of equal intensity were observed when a peptide or a polysaccharide was coupled to TT and rP40, Moreover, rP40 had advantages compared to TT; e.g., it induced a mixed Th1/Th2 response, whereas TT induced only a Th2 profile. Together, the results indicate that rP40 is a novel carrier protein with potential f or use as an alternative carrier for human vaccination.