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Front Microbiol. 2016 Jun 9;7:844. doi: 10.3389/fmicb.2016.00844. eCollection 2016.

Cytomegalovirus-Infected Cells Resist T Cell Mediated Killing in an HLA-Recognition Independent Manner.

Author information

1
Children's Cancer Research Institute, St. Anna KinderkrebsforschungVienna, Austria; Children's University Hospital, Universitätsklinikum ErlangenErlangen, Germany.
2
Children's Cancer Research Institute, St. Anna Kinderkrebsforschung Vienna, Austria.
3
Institute for Clinical and Molecular Virology, Universitätsklinikum ErlangenErlangen, Germany; Department of Microbiology, The University of ChicagoChicago, IL, USA.
4
Institute for Clinical and Molecular Virology, Universitätsklinikum Erlangen Erlangen, Germany.
5
Children's Cancer Research Institute, St. Anna KinderkrebsforschungVienna, Austria; Department of Pediatrics, St. Anna Kinderspital, Medical University of ViennaVienna, Austria.

Abstract

In order to explore the potential of HLA-independent T cell therapy for human cytomegalovirus (HCMV) infections, we developed a chimeric antigen receptor (CAR) directed against the HCMV encoded glycoprotein B (gB), which is expressed at high levels on the surface of infected cells. T cells engineered with this anti-gB CAR recognized HCMV-infected cells and released cytokines and cytotoxic granules. Unexpectedly, and in contrast to analogous approaches for HIV, Hepatitis B or Hepatitis C virus, we found that HCMV-infected cells were resistant to killing by the CAR-modified T cells. In order to elucidate whether this phenomenon was restricted to the use of CARs, we extended our experiments to T cell receptor (TCR)-mediated recognition of infected cells. To this end we infected fibroblasts with HCMV-strains deficient in viral inhibitors of antigenic peptide presentation and targeted these HLA-class I expressing peptide-loaded infected cells with peptide-specific cytotoxic T cells (CTLs). Despite strong degranulation and cytokine production by the T cells, we again found significant inhibition of lysis of HCMV-infected cells. Impairment of cell lysis became detectable 1 day after HCMV infection and gradually increased during the following 3 days. We thus postulate that viral anti-apoptotic factors, known to inhibit suicide of infected host cells, have evolved additional functions to directly abrogate T cell cytotoxicity. In line with this hypothesis, CAR-T cell cytotoxicity was strongly inhibited in non-infected fibroblasts by expression of the HCMV-protein UL37x1, and even more so by additional expression of UL36. Our data extend the current knowledge on Betaherpesviral evasion from T cell immunity and show for the first time that, beyond impaired antigen presentation, infected cells are efficiently protected by direct blockade of cytotoxic effector functions through viral proteins.

KEYWORDS:

UL36; UL37x1; anti-apoptotic; chimeric antigen receptor; cytomegalovirus; glycoprotein B; herpesvirus; immune evasion

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