Alterations in peripheral blood B-cell populations in SHIV89.6P-infected macaques (Macacca fascicularis)

Abstract

In addition to CD4+ T cell depletion, the B cell compartment of HIV-infected patients exhibits abnormalities, including deficits and diminished responses to ex vivo antigenic stimulation and in vivo vaccination. We used chimeric simian-human immunodeficiency virus (SHIV) infection of cynomolgus macaques to determine the dynamics of peripheral blood B cell alterations in this model of HIV infection. During the course of infection, we observed progressive loss of total and memory (CD27+) B cells, increased percentages of activated (CD95+) B cells, hypergammaglobulinemia, and deficits in the CD21+ B cell population. In addition, we noted declines in subsets of memory B cells, including both IgM+ and class-switched (IgD-IgM- CD27+) cells, with sustained deficits in the IgM+ memory (IgM+CD27+) B cell population. The similarity of the B cell alterations in these studies to those observed in HIV+ subjects supports the utility of the SHIV macaque model for examination of HIV-related B cell dysfunction.

Figure 1.

Decline of total B cells and CD4+ T cells after SHIV infection. (A) B cells were distinguished from other lymphocytes by CD20 surface expression (representative plot). (B) Total numbers of B (CD20+) cells and (C) percentages of lymphocytes positive for CD20 were determined by flow cytometry of serial time points. (D) Mean CD4+ T cell numbers. (E) Kinetics of plasma viral load (open circles) compared with CD20+ cell numbers (solid squares) are shown. *, value significantly (P < 0.05, paired Student t-test) different from baseline value.

Figure 2.

Percentages of CD95+ B cells were increased after SHIV infection. Flow cytometry of CD95+ (Fas) B cells at serial time points in a subset of SHIV-infected macaques (n = 17). (A) Numbers and (B) percentages of B cells positive for CD95 are shown. *, value significantly (P < 0.05, paired Student t-test) different from baseline value.

Figure 3.

B cells expressing CD21 were decreased after SHIV infection. (A) Numbers and (B) percentages of peripheral blood B cells expressing the surface marker CD21 (CD20+CD21+) were determined by flow cytometry at serial time points in SHIV-infected macaques (n = 29). *, value significantly (P < 0.05, paired Student t-test) different from baseline value.

Figure 4.

CD27+ B cells and subsets in peripheral blood of SHIV-infected macaques. (A) Peripheral blood memory B (CD20+CD27+) cell numbers in macaques (n = 29) were determined by flow cytometry at serial time-points. (B) Numbers and (C) percentages of class-switched (IgM–IgD–) and (D) numbers and (E) percentages of IgM memory (IgM+CD27+) subsets of CD27+ B cells are shown for a subset of macaques (n = 17). *, value significantly (P < 0.05, paired Student t-test) different from baseline value.

Figure 5.

Naïve B cells (CD20+CD27– lymphocytes) declined from baseline values after SHIV infection. Peripheral blood naïve B (CD20+CD27–) cells in macaques (n = 29) were evaluated by flow cytometry at serial time points. (A) Numbers and (B) percentages are shown. *, value significantly (P < 0.05, paired Student t-test) different from baseline value.

Figure 6.

Evidence of hypergammaglobulinemia in SHIV-infected macaques. Concentrations of total plasma IgG was measured by ELISA of a subset of SHIV-infected macaques (n = 12) at serial time points. Changes were significant (P = 0.0041) by repeated-measures ANOVA.