Anti-Group B Streptococcus antibody in infants born to mothers with human immunodeficiency virus (HIV) infection

Background: HIV-exposed uninfected infants have increased infection risk and mortality compared to HIV-unexposed infants. HIV-exposed infants may be at increased risk of invasive GBS disease due to reduced maternal antibody against GBS. Methods: We quantified antibodies that bind to the surface of whole Group B Streptococcus (GBS) of serotypes Ia, lb, II, III and V using novel flow cytometry assays in South African HIV-infected and noninfected mothers and their uninfected infants. Antibody-mediated complement Cb3/iC3b deposition onto GBS of these serotypes was also quantified by a novel flow cytometry assay. Results: Geometric mean concentration (GMC) of both surface-binding anti-GBS antibody and antibody-mediated complement deposition onto GBS were reduced in HIV-infected women (n = 46) compared to HIV-uninfected women (n=58) for ST1a (surface-binding: 19.3 vs 293; p=0.003; complement deposition: 2.9 vs 5.3 SU/mL; p=0.003), STIb (24.9 vs 47.6; p=0.003; 2.6 vs 4.9 SU/mL; p=0.003), STII (19.8 vs 50.0; p=0.001; 3.1 vs 6.2 SU/mL; p=0.001), STIII (27.8 vs 60.1; p=0.001; 2.8 vs 5.3 SU/mL; p=0.001) and STV (121.9 vs 185.6 SU/mL; p<0.001) and in their infants for STIa (complement deposition 9.4 vs 27.0 SU/mL; p=0.02), STIb (13.4 vs 24.5 SU/mL; p=0.02), STII (14.6 vs 42.7 SU/mL; p=0.03), STIII (26.6 vs 62.7 SU/mL; p=0.03) and STV (90.4 vs 165.8 SU/mL; p=0.04). Median transplacental transfer of antibody from HIV-infected women to their infants was reduced compared to HIV-uninfected women for GBS serotypes 11 (0.42 [IQR 0.22-0.59] vs 1.0 SU/mL [0.42-1.66]; p<0.001), III (0.54 [0.34-1.03] vs 0.95 SU/mL [0.42-3.05],p=0.05) and V (0.51 [0.28-0.79] vs 0.75 SU/mL [0.26-2.9],p=0.04). The differences between infants remained significant at 16 weeks of age. Conclusions: Maternal HIV infection was associated with lower anti-GBS surface binding antibody concentration and antibody-mediated C3b/iC3b deposition onto GBS bacteria of serotypes Ia, lb, II, III and V. This may render these infants more susceptible to early and late onset GBS disease. Crown Copyright (C) 2014 Published by Elsevier Ltd.