부산대학교 도서관

Ab to PRP are protective against systemic infections by Hib, but infants under 18 mo usually have an inadequate Ab response to PRP vaccine. To circumvent this unresponsiveness, we conjugated oligosaccharides of PRP to a protein carrier, CRM197, a nontoxic version of diphtheria toxin. Infants were injected with the conjugate at ages 2, 4, and 6 mo. At age 9 mo the geometric mean titer (GMT) of anti-PRP Ab in a group of 5 such infants was 2.0 μg/ml; the response included IgG Ab. In an unvaccinated control group of 13 infants the GMT was 0.015 μg/ml, with no IgG included. Both groups were then vaccinated with PRP vaccine, and the anti-PRP Ab was measured 1 mo later. In the control group, 3/13 infants had a rise, and the GMT rose to 0.024 μg/ml. In the group primed with conjugate, 4/5 had a rise, and the GMT rose to 7.2 μg/ml. Thus the conjugate is able not only to raise the Ab to high levels, but also to prime for an enhanced response to the polymer. It seems likely that such a response would occur also when the infant encounters Hib. Further, boosting with PRP after priming with conjugate may maintain the Ab at an elevated level.