KSHV infects a subset of human tonsillar B cells, driving proliferation and plasmablast differentiation
Lynn M. Hassman, … , Thomas J. Ellison, Dean H. Kedes
Lynn M. Hassman, … , Thomas J. Ellison, Dean H. Kedes
Published January 18, 2011
Citation Information: J Clin Invest. 2011;121(2):752-768. https://doi.org/10.1172/JCI44185.
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Research Article

KSHV infects a subset of human tonsillar B cells, driving proliferation and plasmablast differentiation

Abstract

Kaposi sarcoma–associated herpesvirus (KSHV; also known as HHV8) is the causative agent of two B cell tumors, multicentric Castleman disease (MCD) and primary effusion lymphoma (PEL). However, little is known about the nature of the specific B cell subtype(s) most susceptible to infection. Identifying these cells would provide direct insight into KSHV transmission and virus-induced transformation. To identify this subset and to determine whether infection alters its cellular phenotype, we exposed human tonsillar cells to KSHV and characterized infected cells using high-throughput multispectral imaging flow cytometry (MIFC). Stable expression of the virally encoded latency-associated nuclear antigen (LANA), a marker of latent KSHV infection, was observed predominantly in cells expressing the l light chain of the B cell receptor. These LANA+ B cells proliferated and exhibited similarities to the cells characteristic of MCD (IgMl-expressing plasmablasts), including blasting morphology with elevated expression of Ki67, variable expression of CD27, and high levels of IgM and IL-6 receptor. Furthermore, the proportion of infected cells showing a blasting phenotype increased upon addition of exogenous IL-6. Our data lead us to propose that oral transmission of KSHV involves the latent infection of a subset of tonsillar IgMl-expressing B cells, which then proliferate as they acquire the plasmablast phenotype characteristic of MCD.

Authors

Lynn M. Hassman, Thomas J. Ellison, Dean H. Kedes

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Figure 6

KSHV-infected B cells resemble MCD plasmablasts.

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KSHV-infected B cells resemble MCD plasmablasts. Tonsil cells were expos...
Tonsil cells were exposed to KSHV and analyzed by MIFC for expression of LANA, IgM, and CD27 at 72 hpi. (A) Representative images of cells labeled with antibodies to LANA, IgM, and CD27. (B) Left panel: Histogram showing representative gating for IgM+ cells. Right panel: Percentage of IgM– or IgM+ cells expressing LANA dots, from 5 donors (individual symbols). (C) Left panel: Histogram showing, among IgM+ cells (gated as in B), levels of IgM expression on LANA– (gray line) versus LANA+ (black line) cells. Right panel: Among IgM+ cells, fold change in IgM expression (MFI) of individual LANA+ groups (1–2, 3–4, ≥5 dots/cell) compared with LANA– (0 dots) cells. Values represent mean ± SEM from 5 separate tonsil donors. P value reflects significance of Spearman correlation, which was 0.797. (D) Left panel: Representative histogram showing CD27 expression on LANA–IgM+ (gray filled) and LANA+IgM+ (black line) cells. Vertical line indicates threshold above which CD27 signal becomes visible by MIFC. Above left: Examples of cells on either side of threshold. Right panel: Percentage of IgM+LANA– or IgM+LANA+ cells expressing CD27 (5 donors). (E) Scatter plot showing nuclear and cytoplasmic areas for LANA– cells (gray dots) and LANA+ cells (green circles). (F) Mean N/C ratios for uninfected (0 dots) and cells with low (1–2 dots), moderate (3–4 dots), and high (≥5 dots/cell) viral load. Data represent mean ± SEM from 4 of 6 KSHV-exposed tonsils. P value reflects significance of Spearman correlation, which was 0.675.