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

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.