IMMUNIZATION WITH HAEMOPHILUS-INFLUENZAE TYPE-B CONJUGATE VACCINE IN CHILDREN GIVEN BONE-MARROW TRANSPLANTATION - COMPARISON WITH HEALTHY AGE-MATCHED CONTROLS

Forty-seven patients (age range, 7 months-18 years) with malignant (38 cases) and nonmalignant (9 cases) disorders given an allogeneic or an autologous bone marrow transplantation (BMT) were immunized with Haem ophilus influenzae type b (Hib) polysaccharide-diphtheria toroid conju gate vaccine administered in a single dose at different time points af ter transplantation. Results were compared with those of 13 healthy ch ildren matched for age and sex who received the same immunization sche dule. Serum and saliva samples for measurement of total IgG subclass a nd specific antibody levels were obtained from patients and healthy co ntrols before and 3 weeks after vaccination. Twenty-five of the 47 pat ients (53%) had a specific anti-Hib IgG response, while an effective I gA and IgM response was mounted by 23 (49%) and 11 (23%) children, res pectively. In the control group, 13 of 13 subjects mounted a specific IgG antibody production (P < 0.005 in comparison to the patients' resp onse rate), while an IgA and IgM response was demonstrated in 12 (92%; P < 0.01 compared to transplanted patients) and 7 (54%; P < 0.05 in c omparison to BMT recipients) children, respectively. Lapse of time fro m BMT to immunization was the most important factor predicting antibod y response, as proved by an effective increase in prevaccination speci fic IgG levels in the majority of patients vaccinated after 2 years fr om transplant. Our data demonstrate that BMT recipients have a reduced capacity to mount an antibody response to polysaccharide antigens com pared to normal controls, even when a protein-conjugated vaccine is em ployed. Since time after transplant is the major factor influencing th e recovery of immune reactivity to polysaccharide antigens, the ontoge ny of the B cell repertoire seems to follow a predetermined sequential program of development.