Humoral immune responses to Neisseria meningitidis in children

An understanding of the nature of immunity to serogroup B meningococci in c hildhood is necessary in order to establish the reasons for poor responses to candidate vaccines in infancy. We sought to examine the nature of humora l immune responses following infection in relation to age. Serum bactericid al activity was poor in children under 12 months of age despite recent infe ction with Neisseria meningitidis. The highest levels of bactericidal activ ity were seen in children over 10 years of age. However, infants produced l evels of total immunoglobulin G (Igc) and IgG subclass antibodies similar t o those in older children in a meningococcal enzyme-linked immunosorbent as say. Most antibody was of the IgG1 and IgG3 subclasses. This striking age d ependency of bactericidal antibody response following infection is not appa rently due to failure of class switching in infants but might be due to qua litative differences in antibody specificity or affinity.