Phenotypes and distribution of mucosal memory B-cell populations in the SIV/SHIV rhesus macaque model

Abstract

As vaccine-elicited antibodies have now been associated with HIV protective efficacy, a thorough understanding of mucosal and systemic B-cell development and maturation is needed. We phenotyped mucosal memory B-cells, investigated isotype expression and homing patterns, and defined plasmablasts and plasma cells at three mucosal sites (duodenum, jejunum and rectum) in rhesus macaques, the commonly used animal model for pre-clinical vaccine studies. Unlike humans, macaque mucosal memory B-cells lacked CD27 expression; only two sub-populations were present: naïve (CD21+CD27−) and tissue-like (CD21−CD27−) memory. Similar to humans, IgA was the dominant isotype expressed. The homing markers CXCR4, CCR6, CCR9 and α4β7 were differentially expressed between naïve and tissue-like memory B-cells. Mucosal plasmablasts were identified as CD19+CD20+/−HLA-DR+Ki-67+IRF4+CD138+/− and mucosal plasma cells as CD19+CD20−HLA-DR−Ki-67−IRF4+CD138+. Both populations were CD39+/−CD27−. Plasma cell phenotype was confirmed by spontaneous IgA secretion by ELISpot of positively-selected cells and J-chain expression by real-time PCR. Duodenal, jejunal and rectal samples were similar in B-cell memory phenotype, isotype expression, homing receptors and plasmablast/plasma cell distribution among the three tissues. Thus rectal biopsies adequately monitor B-cell dynamics in the gut mucosa, and provide a critical view of mucosal B-cell events associated with development of vaccine-elicited protective immune responses and SIV/SHIV pathogenesis and disease control.

Influence of Plasma Cell Niche Factors on the Recruitment and Maintenance of IRF4 hi Plasma Cells and Plasmablasts in Vaccinated, Simian Immunodeficiency Virus-Infected Rhesus Macaques with Low and High Viremia

“…1D) (29,31,39). Expression of CD27 was low in both subsets, in agreement with previous findings (34,35) (data not shown).…”

“…High expression of the transcription factor IRF4 is characteristic of both PB and PC (24)(25)(26), while expression of CD138 is most often associated with PC differentiation (27,28). Consistent with other reports and through backgating analysis of IRF4 hi populations of interest, these PC/PB subsets were identified as lacking expression of CD20 (29)(30)(31)(32) but as CD19 ϩ/Ϫ (31,33,34). Thus, for all sites examined, PB were identified as CD20 Ϫ IRF4 hi CD138 Ϫ and PC as CD20 Ϫ IRF4 hi CD138 ϩ (Fig.…”

“…Cells were washed, and RBCs were lysed in H 2 O as described above and resuspended in R10. Rectal pinch biopsy specimens were processed in the manner outlined by Demberg et al (29). Rectal tissue sections (17 by 14 mm 2 ) were frozen in OCT for subsequent SIV RNA analysis and tissue staining.…”

Editorial: Where’s the B in NHP?

“…Similar to other recent reports, Neumann et al [1] apply multicolor flow cytometry to rhesus macaque B cell subsetting and, like a concurrent report [2], include assessments of activation molecules, chemokine receptors, and Igs in their analyses. In addition, the authors follow phenotyping schemes applied to human B cells and plasmablasts/plasma cells (reviewed in ref.…”

“…There is growing literature on memory B cell subset distributions in rhesus macaque, which generally parallel distributions and phenotypes observed in humans. In both species, CD20+ B cells are defined further as naïve (CD21+ CD272), resting memory (CD21+ CD27+), activated memory (CD212 CD27+/hi), and tissue-like or double-negative memory (CD212 CD272) [2,[4][5][6]. Neumann et al [1] follow this scheme and include CD10 as a marker of immature/transitional B cells.…”