Serum B-cell activating factor levels in HIV-2 infection.(a) Serum B-cell activating factor (BAFF) levels in HIV-2-infected, HIV-1-infected, and seronegative (Seroneg) individuals. Due to sample availability, a distinct seronegative cohort was used [11 women/six men; 39 (26–61) median years of age; 63.85 (40.10–76.90) median CD4⁺ T-cell frequency; 908 (537–1312) median CD4⁺ T-cells/μl; 8.15 (2.56–18.19) median B-cell frequency; 163 (63–383) median B-cells/μl], as well as representative subgroups of the infected cohorts [HIV-2, including the 10 treated individuals: 13 women/nine men; 56 (19–72) median years of age; 28.02 (4.51–63.20) median CD4⁺ T-cell frequency; 337 (52–1336) median CD4⁺ T-cells/μl; 200 (200–34314) median RNA copies per millilitre; 108 (5–1002) median proviral DNA copies per 10⁶ PBMC; 7.41 (2.89–19.70) median B-cell frequency; 132 (30–369) median B-cells per microlitre; and untreated HIV-1: three women/nine men; 42 (23–61) median years of age; 32.85 (7.71–74.4) median CD4⁺ T-cell frequency; 431 (77–1425) median CD4⁺ T-cells/μl; 1.4 × 10⁴ (40–4.5 × 10⁶) RNA copies per millilitre; 88 (5–573) median proviral DNA copies per 10⁶ PBMC; 6.64 (2.08–15.60) median B-cell frequency; 112 (56–324) median B-cells per microlitre)]. (b) The HIV-2 cohort was further stratified according to disease stage (early: >350 CD4⁺ T-cells/μl; late: <350 CD4⁺ T-cells/μl) and levels of plasma viral load (aviremic: undetectable; viremic: detectable), and the BAFF levels were compared between seronegatives and all groups of HIV-2-infected individuals. Each dot represents one individual and bars indicate median. Filled circles refer to antiretroviral therapy (ART)-treated individuals. Statistical analysis was performed using the Mann–Whitney test and the significant P values are shown.