Differences in T cell cytotoxicity and cell death mechanisms between progressive multifocal leukoencephalopathy, herpes simplex virus encephalitis and cytomegalovirus encephalitis.
During the appearance of human immunodeficiency virus infection in the 1980 and the 1990s, progressive multifocal leukoencephalopathy (PML), a viral encephalitis induced by the JC virus, was the leading opportunistic brain infection. As a result of the use of modern immunomodulatory compounds such as Natalizumab and Rituximab, the number of patients with PML is once again increasing. Despite the presence of PML over decades, little is known regarding the mechanisms leading to death of infected cells and the role the immune system plays in this process. Here we compared the presence of inflammatory T cells and the targeting of infected cells by cytotoxic T cells in PML, herpes simplex virus encephalitis (HSVE) and cytomegalovirus encephalitis (CMVE). In addition, we analyzed cell death mechanisms in infected cells in these encephalitides. Our results show that large numbers of inflammatory cytotoxic T cells are present in PML lesions. Whereas in HSVE and CMVE, single or multiple appositions of CD8+or granzyme-B+T cells to infected cells are found, in PML such appositions are significantly less apparent. Analysis of apoptotic pathways by markers such as activated caspase-3, caspase-6, poly(ADP-ribose) polymerase-1 (PARP-1) and apoptosis-inducing factor (AIF) showed upregulation of caspase-3 and loss of caspase-6 from mitochondria in CMVE and HSVE infected cells. Infected oligodendrocytes in PML did not upregulate activated caspase-3 but instead showed translocation of PARP-1 from nucleus to cytoplasm and AIF from mitochondria to nucleus. These findings suggest that in HSVE and CMVE, cells die by caspase-mediated apoptosis induced by cytotoxic T cells. In PML, on the other hand, infected cells are not eliminated by the immune system but seem to die by virus-induced PARP and AIF translocation in a type of cell death defined as parthanatos.
Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria.
Susanne
S
Laukoter
Department of Neurology, Sozialmedizinisches Zentrum Ost-Donauspital, Vienna, Austria.|Karl Landsteiner Institut für neuroimmunologische und neurodegenerative Erkrankungen, Donauspital, Vienna, Austria.
Helmut
H
Rauschka
Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria.
Anna R
AR
Tröscher
Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria.
Ulrike
U
Köck
Department of Neurology, Brain Research Institute, Niigata University, Niigata, Japan.
Etsuji
E
Saji
Institute of Clinical Neurobiology, Alberichgasse 5, 1150, Vienna, Austria.
Kurt
K
Jellinger
Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria.
Hans
H
Lassmann
Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, Spitalgasse 4, 1090, Vienna, Austria. jan.bauer@meduniwien.ac.at.
Jan
0000-0001-5802-8047
J
Bauer
D017088:AIDS-Related Opportunistic Infections / Q000276:immunology* / Q000473:pathology; D000328:Adult; D000368:Aged; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D001921:Brain / Q000276:immunology / Q000473:pathology / Q000821:virology; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000502:physiology*; D002648:Child; D003586:Cytomegalovirus Infections / Q000276:immunology* / Q000473:pathology; D020803:Encephalitis, Herpes Simplex / Q000276:immunology* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007968:Leukoencephalopathy, Progressive Multifocal / Q000276:immunology* / Q000473:pathology; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009474:Neurons / Q000276:immunology / Q000473:pathology; D009836:Oligodendroglia / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology / Q000821:virology
C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; C505407:CASP3 protein, human; D053148:Caspase 3
Caspase-mediated; Cell death pathways; Cytomegalovirus; Herpes simplex virus; Parthanatos; Progressive multifocal leucoencephalopathy; Virus encephalitis