Despite CD4⁺ count restoration and viral load suppression with antiretroviral therapy (ART), HIV-infected children remain at increased risk of life-threatening infections including invasive pneumococcal disease (IPD). We therefore investigated whether persistent susceptibility to IPD following ART is associated with incomplete recovery of B-cell function.

41 HIV-infected Malawian children commencing ART were followed-up for a 1 year period during which time blood samples were collected at 0, 3, 6 and 12 months for comprehensive immunophenotyping and pneumomococcal-specific Memory B-cell Enzyme-Linked Immunospot assays. In addition, nasopharyngeal swab samples were cultured to determine pneumococcal carriage rates.

Normalization of major lymphocyte subsets such as CD4⁺ percentages was evident following 3 months of ART. The proportions of mature naïve B cells (CD19⁺ CD10⁻ CD27⁻ CD21^hi) and resting memory B cells (CD19⁺ CD27⁺ CD21^hi) increased and apoptosis-prone mature activated B cells (CD19⁺ CD21^lo CD10⁻) decreased markedly by 12 months. However, in the context of high nasopharyngeal pneumococcal carriage rates (83%), restoration of pneumococcal protein antigen-specific B-cell memory was more delayed.

These data show that, in chronically HIV-infected children receiving ART, improvement in B-cell memory profiles and function is slower than CD4⁺ T-cells. This supports early initiation of ART and informs research into optimal timing of immunization with pneumococcal vaccines.