Australian indigenous infants experience the highest incidence of chronic suppurative and acute otitis media in the world with many babies developing disease in the early postnatal period. Streptococcus pneumoniae is the major cause of otitis media in this population. Infants are protected against bacterial disease in the first months of life by passive transfer of maternal antibody across the placenta during the late stages of gestation. We hypothesized that reduced passive immunity may contribute to increased disease risk in this population. We compared the concentrations and function of serotype-specific IgG in cord serum from Australian indigenous neonates and Gambian neonates, the latter experiences a similar socioeconomic status to Australian indigenous neonates.
Serotype-specific IgG, IgG1 and IgG2 were measured using a modified 3rd generation enzyme linked immunosorbent assay based on World Health Organization recommendations. Antibody avidity was measured using a modified sodium thiocyanate elution method.
Australian indigenous neonates had significantly increased levels of serotype-specific IgG compared with Gambian populations for 6 of 12 serotypes (P < 0.02). There was no significant difference in antibody function, as measured by antibody avidity, between the 2 groups.
An increased risk for otitis media in Australian indigenous neonates is not primarily determined by specific antibody titers against pneumococcal bacteria. Further investigation into the possible roles of the innate immune response and Eustachian tube dysfunction in the development of chronic otitis media amongst Australian indigenous infants is warranted.