Impact of HIV Status on Group B Streptococcus Colonization and Antibody Responses in Serum and Vaginal Mucosa

Group B streptococcus (GBS) is a commensal bacterium of the digestive and genital tracts that can occasionally cause maternal and neonatal disease. GBS is particularly a burden in low-resource settings, where infections with HIV are also highly prevalent. This study investigates the impact of HIV status on GBS colonization and antibody levels.

In Uganda, 90 nonpregnant women of childbearing age were followed for 3 months. Every 2 weeks, rectal and vaginal swabs were tested for GBS, and vaginal cups and blood were collected for measurement of GBS capsular polysaccharides (CPS) IgG using standardized assays.

Twenty-six of 90 women were living with HIV. Almost 51/90 women were GBS colonized at 1 or several visits. GBS colonization fluctuated in the rectal and vaginal sites. Most prevalent serotypes were Ia and III, with 33 individuals carrying different serotypes over time. Serum and vaginal CPS-IgG levels were stable over 12 weeks. In serum, for serotypes Ib-V, the geometric mean concentration (GMC) of CPS-IgG did not differ between HIV+ and HIV- participants. However, the GMC for serum CPS-Ia-IgG in the HIV+ group was 2.5 times lower than in the HIV- group (P = 0.038). Vaginal CPS-IgG was measurable in 5/26 (19%) HIV+ participants, and 32/64 (50%) HIV- participants.

Despite fluctuating GBS colonization, antibody levels remained stable over 12 weeks. The level of CPS-Ia-specific IgG in serum was lower in women with HIV than in those without HIV. Vaginal CPS-specific IgG was not measurable in 81% of individuals with HIV.