Perturbations in B cell responsiveness to CD4+ T cell help in HIV-infected individuals

Abstract

HIV infection induces a wide array of B cell dysfunctions. We have characterized the effect of plasma viremia on the responsiveness of B cells to CD4(+) T cell help in HIV-infected patients. In HIV-negative donors, B cell proliferation correlated with CD154 expression on activated CD4(+) T cells and with the availability of IL-2, whereas in HIV-infected viremic patients, reduced B cell proliferation was observed despite normal CD154 expression on activated CD4(+) T cells. Reduced triggering of B cells by activated CD4(+) T cells was clearly observed in HIV-infected viremic patients compared with aviremic patients with comparable CD4(+) T cell counts, and a dramatic improvement in B cell function was observed in patients whose plasma viremia was controlled by effective antiretroviral therapy. The degree of B cell dysfunction in viremic patients correlated strongly with the inability of B cells to express CD25 in response to activated CD4(+) T cells, resulting in an inability to mount a normal proliferative response to IL-2. Similar defects in responsiveness to IL-2 were observed in the B cells of HIV-infected viremic patients in the context of B cell receptor stimulation. These data provide new insight into the mechanisms associated with ineffective humoral responses in HIV disease.

Figures

Figure 1

B cell responses induced by activated CD4+ T cells and soluble stimuli. (A) CD4+ T cells isolated from a representative HIV-negative donor were stimulated with media or anti-CD3 ± anti-CD28 ± IL-2/IL-12 for 40 h, irradiated, and cocultured with B cells in the presence of anti-CD3. (B) Effect of neutralizing mAbs on B cells from a representative HIV-negative donor stimulated with anti-CD3/CD28-activated CD4+ T cells in the presence of anti-CD3 or B cells stimulated with phorbol 12-myristate 13-acetate (PMA)/ionomycin. (C) Effect of HIV infection and plasma viremia on B cell responsiveness to CD4+ T cells under conditions described in A; data are from a representative HIV-infected viremic patient. (See Fig. 2A for additional pairs of HIV-negative versus HIV-infected viremic individuals.) All culture conditions were performed in triplicate with standard deviation indicated by the error bars.

Figure 2

Effect of plasma viremia in HIV infection on B cell proliferation in response to activated CD4+ T cells. CD4+ T cells isolated from patients described in Table 1 were stimulated for 40 h with anti-CD3/CD28 (A) or anti-CD3/CD28 + IL-2/IL-12 (B and C), irradiated, and cocultured with B cells in the presence of immobilized anti-CD3 (A) or IL-2 (B and C). Three sets of patients were compared: HIV-infected viremic versus HIV-negative (A), cross-sectional HIV-infected viremic versus HIV-infected aviremic with matched CD4+ T cell counts (B), and longitudinal HIV-infected viremic versus HIV-infected aviremic (C). Inset legends identify paired patients from Table 1, and, for sets A and B, assays on paired patients were performed in parallel on the same day. All culture conditions were performed in triplicate with standard deviation indicated by the error bars.

Figure 3

Comparisons between B cell proliferation and up-regulation of CD154 on activated CD4+ T cells and activation markers on B cells. B cell proliferation in response to anti-CD3/CD28 + IL-2/IL-12-stimulated CD4+ T cells and IL-2 was correlated with induction of CD154 on the effector CD4+ T cells (A) and induction of CD25 on the responding B cells (B). HIV-negative donors were excluded from A, and all data points represent individual patients.

Figure 4

Response of B cells to BCR stimulation in the presence of IL-2. (A) B cells were isolated from four HIV-negative, four HIV-infected aviremic, and four HIV-infected viremic patients and stimulated with anti-IgM and IL-2. The shaded bars represent medians for each patient group. (B) Expression of CD25 and CD80 on activated B cells of representative HIV-infected viremic and aviremic patients.