Maternal Parasitic Infections Alter Infant Antibody Response to Pneumococcal Immunization

Abstract

Vaccine-preventable diseases remain a signifcant cause of early childhood mortality in developing countries, despite concerted efforts to improve vaccine coverage. One reason for this discrepancy may be the impact of prenatal exposure to parasitic antigens on the infant's developing immune system. Our goal in this study was to investigate the effect of maternal parasitic infections on the infant immune response to early childhood vaccines. 580 pregnant Kenyan mothers were enrolled in the study and tested at prenatal visits for malaria, soil transmitted helminths, Giardia lamblia, Strongyloides stercoralis and Schistosoma haematobium infection. The infants received the 10-valent Streptococcus pneumonia conjugate vaccine (PCV), Haemophilus infuenzae type B (Hib) and Diphtheria toxoid (DT) vaccines at 6, 10, and 14 weeks of age. Serum was collected from cord blood, 10 and 14-weeks, 6 months, and every 6 months following through the second year of life. A multiplex fuorescent bead assay determined IgG concentrations to HiB, DT, and the ten PCV serotypes: 1, 4, 5, 6B, 7F, 9V, 14, 18C, 19F and 23F. Total parasitic infection incidence among mothers in the study is high, with 373 of 580 (64.2%) participants having at least one parasitic infection during pregnancy and 75 participants (13%) with 2 or more infections. The most common infections were hookworm (19.7%), Plasmodium falciparum (16.2%), S. haematobium (11%), and Trichuris trichiura (10.5%). In preliminary analysis using a mixed linear model comparing infection status to log (antibody concentration), we are able to see a 37% higher concentration of PCV 9V antibody in children born to mothers with infections (p=0.016) compared to uninfected mother/child pairs. S. haematobium infection was associated with signifcantly higher concentrations in 4 PCV antigens: 1 (3.9 fold higher, p=0.0006), 7 (2.3 fold higher, p=0.004), 9V (2.3 fold higher, p=0.002), and 18C (6.8 fold higher, p<0.0001). More testing is ongoing with this study, including more samples from later time-points, which will provide a more detailed analysis of the dynamics of first and second year responses to vaccine antigens.