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, Ib, II, III and V using novel flow cytometry assays in South African HIV-infected and non-infected mothers and their uninfected infants. Antibody-mediated complement C3b/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 29.3; 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 II (0.42 [IQR 0.22-0.59] vs 1.0. SU/mL [0.42-1.66]; p<. 0.001), III (0.54 [0.31-1.03] 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, Ib, II, III and V. This may render these infants more susceptible to early and late onset GBS disease.