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A gammaherpesvirus Bcl-2 ortholog blocks B cell receptor-mediated apoptosis and promotes the survival of developing B cells in vivo
Journal article   Open access   Peer reviewed

A gammaherpesvirus Bcl-2 ortholog blocks B cell receptor-mediated apoptosis and promotes the survival of developing B cells in vivo

Carrie B Coleman, Jennifer E McGraw, Emily R Feldman, Alexa N Roth, Lisa R Keyes, Katrina R Grau, Stephanie L Cochran, Thomas J Waldschmidt, Chengyu Liang, J Craig Forrest, …
PLoS pathogens, Vol.10(2), pp.e1003916-e1003916
02/2014
DOI: 10.1371/journal.ppat.1003916
PMCID: PMC3916410
PMID: 24516386
url
https://doi.org/10.1371/journal.ppat.1003916View
Published (Version of record) Open Access

Abstract

Gammaherpesviruses such as Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8) establish lifelong latency in their hosts and are associated with the development of several types of malignancies, including a subset of B cell lymphomas. These viruses are thought to co-opt the process of B cell differentiation to latently infect a fraction of circulating memory B cells, resulting in the establishment of a stable latency setpoint. However, little is known about how this infected memory B cell compartment is maintained throughout the life of the host. We have previously demonstrated that immature and transitional B cells are long-term latency reservoirs for murine gammaherpesvirus 68 (MHV68), suggesting that infection of developing B cells contributes to the maintenance of lifelong latency. During hematopoiesis, immature and transitional B cells are subject to B cell receptor (BCR)-mediated negative selection, which results in the clonal deletion of autoreactive B cells. Interestingly, numerous gammaherpesviruses encode homologs of the anti-apoptotic protein Bcl-2, suggesting that virus inhibition of apoptosis could subvert clonal deletion. To test this, we quantified latency establishment in mice inoculated with MHV68 vBcl-2 mutants. vBcl-2 mutant viruses displayed a marked decrease in the frequency of immature and transitional B cells harboring viral genome, but this attenuation could be rescued by increased host Bcl-2 expression. Conversely, vBcl-2 mutant virus latency in early B cells and mature B cells, which are not targets of negative selection, was remarkably similar to wild-type virus. Finally, in vivo depletion of developing B cells during chronic infection resulted in decreased mature B cell latency, demonstrating a key role for developing B cells in the maintenance of lifelong latency. Collectively, these findings support a model in which gammaherpesvirus latency in circulating mature B cells is sustained in part through the recurrent infection and vBcl-2-mediated survival of developing B cells.
Flow Cytometry Polymerase Chain Reaction B-Lymphocytes - cytology Proto-Oncogene Proteins c-bcl-2 - immunology Mice, Inbred C57BL Cell Survival - immunology Blotting, Western Receptors, Antigen, B-Cell - immunology Cell Differentiation - immunology Animals Apoptosis - immunology Tumor Virus Infections - immunology B-Lymphocytes - virology Mice Gammaherpesvirinae - physiology Virus Latency - immunology Microscopy, Fluorescence Herpesviridae Infections - immunology

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