Pneumococcal challenge identifies antibody correlates of carriage in adults with suppressed HIV

People with HIV remain at increased risk of pneumococcal carriage and disease despite effective antiretroviral therapy. This experimental challenge study enrolled 60 clinically stable, virally suppressed adults with HIV and 60 HIV-uninfected adults. Participants received intranasal live pneumococcus serotype 6B; investigators assessed carriage using nasal wash culture and serotyping, and measured serum and nasal IgG concentrations and antibody binding.

Baseline capsular IgG, whole-cell IgG and antibody binding were similar between groups. Among participants with HIV, carriage susceptibility was associated with lower baseline serum capsular 6B IgG (0.84 versus 2.33 µg/mL; p<0.01) and nasal whole-cell IgG (92.2 versus 205 AU/mL; p=0.02). Nasal capsular IgG was also lower, although this association was not statistically significant (328 versus 761 pg/mL; p=0.07). These associations were not observed in HIV-uninfected participants. Challenge did not increase IgG concentrations in either group. Among HIV-uninfected participants with carriage, antibody binding increased from baseline to day 21 (120 to 209 AU; p=0.004); no increase was detected in participants with HIV (79.2 to 72.3 AU; p=0.72).

The findings support evaluating vaccination strategies to enhance pneumococcal antibody concentration and function in people with HIV. However, this single-serotype challenge study assessed carriage and immune measures, not vaccine efficacy or prevention of clinical disease. Only the abstract was available for assessment.