Abstract
Ab to the capsular antigen of Hib is considered protective in humans, but the role of Ab of various immunoglobulin classes and subclasses is not well known. We evaluated the protective nature of sera from 13 children, 3 of whom were immunized with polyribosylribitol phosphate (PRP) and 4 with PRP conjugated to diphtheria toxgid (PRP-D); 6 were immunized with PRP conjugated to outer membrane protein of N. meningitidis. Each serum was used to passively immunize a series of 5-day-old rats, followed by subcutaneous inoculation of virulent Hib, The dose of total PRP Ab (Farr technique) required to prevent bacteremia and/or meningitis in 50% of rats (PD50) ranged from 13-916 ng/rat. Sera were also tested for in vitro opsonic activity. Neither protection nor opsgnic activity correlated with total PRP Ab. Analysis of anti-PRP IgG, IgG subclass and IgM Ab suggested that high IgG and IgM Ab were associated with protection. A drop in protection was associated with low Ab of two or more IgG subclasses. No single subclass response was consistently protective. High levels of IgG4 and IgM Ab were present in the most opsonic and protective sera. Anti-PRP IgM alone did not compensate for low levels of two or more IgG subclass Ab's. Full protection probably cannot be realized when there are low levels of Ab of 2 or more of the heavy chain genotypes tested (IgM, IgG1-4).
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Schoettler, J., Kim, K., Hong, J. et al. PROTECTIVE AND OPSONIC ACTIVITY OF IgG SUBCLASS ANTIBODIES (Ab) AGAINST HAEMOPHILUS INFLUENZAE TYPE B (Hib). Pediatr Res 21 (Suppl 4), 318 (1987). https://doi.org/10.1203/00006450-198704010-00903
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DOI: https://doi.org/10.1203/00006450-198704010-00903