Maternal antibody in milk after Group B streptococcus vaccination in Uganda: MAMA study

Abstract

Introduction: Group B Streptococcus (GBS) is a significant cause of morbidity and mortality among newborns worldwide. The available strategies to control GBS disease in low to middle-income countries have met several challenges. Vaccination of pregnant women is a possible strategy to protect infants from GBS infection, as breast milk is a source of immunoglobulins that can be increased by vaccination during pregnancy. We aimed to compare the amounts of GBS antibodies in breast milk following vaccination. Methods: This was a comparative observational study nested in a multicentre randomized, placebo-controlled, double-blind parallel-group study in pregnant women living with and without HIV at Kawempe National Referral Hospital. We evaluated breast milk at birth, 28 days, and 56 days post-delivery for total and GBS specific antibodies, IgA and IgG, using ELISA. Participants were divided into four groups based on their vaccination and HIV status. The primary outcome was to compare the specific anti-GBS concentrations among the groups. Results: The study enrolled 48 participants, of which 39 received the GBS vaccine and 9 received a placebo. Out of these, 25 participants were HIV-infected and 23 were not. Breastmilk was found to contain anti-GBS antibodies, with the highest concentration present in colostrum and declining over time. Participants who received the GBS vaccine had significantly higher concentrations of RibN IgA antibody in breastmilk at 56 days after delivery compared to those who received placebo (p=0.0127). HIV non-infected participants had significantly higher anti-GBS IgG concentrations of Alp1N (p=0.0379), AlphaCN (p=<0.0001), Alp2/3N (p=0.0104), RibN (p=<0.0001) in colostrum and of AlphaCN (0.0192) in breast milk at day 28 compared to HIV-infected participants. Conclusion: The study found presence of GBS-specific IgA and IgG antibodies in breastmilk with the highest concentration found in colostrum and declining over time. This suggests that breastfeeding can offer some protection against GBS, and HIV infection may affect the production of anti-GBS antibodies in breastmilk. More studies are needed to examine this relationship further.