Active lytic infection of human primary tonsillar B cells by KSHV and its noncytolytic control by activated CD4+ T cells
Jinjong Myoung, Don Ganem
Jinjong Myoung, Don Ganem
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Research Article

Active lytic infection of human primary tonsillar B cells by KSHV and its noncytolytic control by activated CD4+ T cells

Abstract

Kaposi sarcoma–associated herpesvirus (KSHV) is a B-lymphotropic virus whose primary site of replication is the oropharynx. KSHV can infect both T and B cells from primary tonsillar explant cultures. However, T cells do not support lytic replication, while B cells spontaneously produce substantial amounts of infectious virus. Here, we provide evidence for a mechanism by which activated T cells may promote or stabilize latency of KSHV infection in B cells. When mixed cultures of B cells and activated T cells were exposed to KSHV, little spontaneous virus production was observed. Removing T cells from the mix or treating the mixed culture with immune suppressants enhanced virus production. Adding back activated T cells to purified infected B cells efficiently suppressed KSHV production, primarily due to CD4+ T cells. This suppressive activity required T cell activation and direct cell-cell contact, but not prior exposure to KSHV antigen. Suppression was not MHC restricted and did not result in killing of the target cell. We therefore propose that oropharyngeal T cells activated by a variety of stimuli can recognize ligands on infected target B cells, leading to signaling events that prevent spontaneous lytic activation and promote latent infection in this compartment.

Authors

Jinjong Myoung, Don Ganem

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Figure 2

Viral gene expression in infected tonsillar cells.

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Viral gene expression in infected tonsillar cells. (A) Copy numbers of e...
(A) Copy numbers of eGFP, vCyclin, and ORF59 mRNA were determined by real-time quantitative PCR after gene-specific reverse transcriptase reactions on 50 ng of DNase-treated total RNA from fractionated T or B cells or unfractionated tonsillar cells (Mix) at the indicated time points; the cells were infected as described in Figure 1. Cells were treated with CsA for the indicated duration. Dots represent data from each individual tonsil. The mean of data from 6 different tonsils is indicated by the horizontal bar. **P < 0.01; ***P < 0.001 by Student’s t test. (B) Mixed cells or purified CD19+ B and CD3+ T cells were infected with rKSHV.219 as described in Figure 1 and Methods. At day 2 and day 4 after infection, total RNA was extracted and subjected to tiling microarray with linear amplification (for details, see Methods). –k, no viral infection. Total RNA from BCBL-1 cells, which were induced to lytic replication by Val (600 μM) for 1–3 days, was included as a positive control. KSHV tiling microarray data (ordered by genome position) are displayed for 13,444 unique probes. The color bar indicates the fold change relative to the level for the uninfected B cells. 2 independent experiments for B cells are shown. Array data for T and mixed cells are 1 representative of 2 independent experiments.