Inefficient establishment of KSHV latency suggests an additional role for continued lytic replication in Kaposi sarcoma pathogenesis
Adam Grundhoff, Don Ganem
Adam Grundhoff, Don Ganem
Published January 1, 2004
Citation Information: J Clin Invest. 2004;113(1):124-136. https://doi.org/10.1172/JCI17803.
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Article Infectious disease

Inefficient establishment of KSHV latency suggests an additional role for continued lytic replication in Kaposi sarcoma pathogenesis

Abstract

Kaposi sarcoma–associated (KS-associated) herpesvirus (KSHV) infection is linked to the development of both KS and several lymphoproliferative diseases. In all cases, the resulting tumor cells predominantly display latent viral infection. KS tumorigenesis requires ongoing lytic viral replication as well, however, for reasons that are unclear but have been suggested to involve the production of angiogenic or mitogenic factors by lytically infected cells. Here we demonstrate that proliferating cells infected with KSHV in vitro display a marked propensity to segregate latent viral genomes, with only a variable but small subpopulation being capable of stable episome maintenance. Stable maintenance is not due to the enhanced production of viral or host trans-acting factors, but is associated with cis-acting, epigenetic changes in the viral chromosome. These results indicate that acquisition of stable KSHV latency is a multistep process that proceeds with varying degrees of efficiency in different cell types. They also suggest an additional role for lytic replication in sustaining KS tumorigenesis: namely, the recruitment of new cells to latency to replace those that have segregated the viral episome.

Authors

Adam Grundhoff, Don Ganem

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Figure 5

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Gardella gel analysis of in vitro–infected SLK and TIME cells. Aliquots ...
Gardella gel analysis of in vitro–infected SLK and TIME cells. Aliquots from KSHV-infected TIME (a) or SLK (b) cultures were evaluated by Gardella gel analysis at various time points after infection (indicated in days above the lanes) and KSHV episomes were detected using a LANA-specific probe. As a control, BCBL-1 cells were loaded in the leftmost and rightmost lanes in a and b, respectively. BCBL-1 cells were either untreated (lanes labeled BCBL-1) or treated with TPA and ionomycin (lanes labeled BCBL-1 ind.) for lytic cycle induction. The position of supercoiled episomes (upper band) and linear as well as nicked and partially degraded KSHV DNA (lower band) are marked by arrows labeled sup and lin, respectively. Note that the band marked with an asterisk in a, migrating slightly above the linear viral DNA, results from nonspecific background hybridization, because it is also present in the uninfected TIME cells loaded in lane 3. TPA/ionomycin-treated BCBL-1 samples show an increase in intensity of the lower (linear) band relative to uninduced BCBL-1 cells due to lytic replication and production of virus particles harboring linear KSHV genomes. (Note: Since spontaneous lytic replication does not occur in SLK [55], the linear DNA in b likely derives from fragmentation of circular KSHV genomes during handling and electrophoresis). infect., infected; ind., lytic cycle induction.