• A20 Curtails Primary but Augments Secondary CD8(+) T Cell Responses in Intracellular Bacterial Infection.

      Just, Sissy; Nishanth, Gopala; Buchbinder, Jörn H; Wang, Xu; Naumann, Michael; Lavrik, Inna; Schlüter, Dirk; Helmholtz Centre for infection research, Inhoffenstr. 7., 38124 Braunschweig, Germany. (2016-12-22)
      The ubiquitin-modifying enzyme A20, an important negative feedback regulator of NF-κB, impairs the expansion of tumor-specific CD8(+) T cells but augments the proliferation of autoimmune CD4(+) T cells. To study the T cell-specific function of A20 in bacterial infection, we infected T cell-specific A20 knockout (CD4-Cre A20(fl/fl)) and control mice with Listeria monocytogenes. A20-deficient pathogen-specific CD8(+) T cells expanded stronger resulting in improved pathogen control at day 7 p.i. Imaging flow cytometry revealed that A20-deficient Listeria-specific CD8(+) T cells underwent increased apoptosis and necroptosis resulting in reduced numbers of memory CD8(+) T cells. In contrast, the primary CD4(+) T cell response was A20-independent. Upon secondary infection, the increase and function of pathogen-specific CD8(+) T cells, as well as pathogen control were significantly impaired in CD4-Cre A20(fl/fl) mice. In vitro, apoptosis and necroptosis of Listeria-specific A20-deficient CD8(+) T cells were strongly induced as demonstrated by increased caspase-3/7 activity, RIPK1/RIPK3 complex formation and more morphologically apoptotic and necroptotic CD8(+) T cells. In vitro, A20 limited CD95L and TNF-induced caspase3/7 activation. In conclusion, T cell-specific A20 limited the expansion but reduced apoptosis and necroptosis of Listeria-specific CD8(+) T cells, resulting in an impaired pathogen control in primary but improved clearance in secondary infection.
    • The Deubiquitinating Enzyme Cylindromatosis Dampens CD8(+) T Cell Responses and Is a Critical Factor for Experimental Cerebral Malaria and Blood-Brain Barrier Damage.

      Schmid, Ursula; Stenzel, Werner; Koschel, Josephin; Raptaki, Maria; Wang, Xu; Naumann, Michael; Matuschewski, Kai; Schlüter, Dirk; Nishanth, Gopala; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017)
      Cerebral malaria is a severe complication of human malaria and may lead to death of Plasmodium falciparum-infected individuals. Cerebral malaria is associated with sequestration of parasitized red blood cells within the cerebral microvasculature resulting in damage of the blood-brain barrier and brain pathology. Although CD8(+) T cells have been implicated in the development of murine experimental cerebral malaria (ECM), several other studies have shown that CD8(+) T cells confer protection against blood-stage infections. Since the role of host deubiquitinating enzymes (DUBs) in malaria is yet unknown, we investigated how the DUB cylindromatosis (CYLD), an important inhibitor of several cellular signaling pathways, influences the outcome of ECM. Upon infection with Plasmodium berghei ANKA (PbA) sporozoites or PbA-infected red blood cells, at least 90% of Cyld(-/-) mice survived the infection, whereas all congenic C57BL/6 mice displayed signatures of ECM, impaired parasite control, and disruption of the blood-brain barrier integrity. Cyld deficiency prevented brain pathology, including hemorrhagic lesions, enhanced activation of astrocytes and microglia, infiltration of CD8(+) T cells, and apoptosis of endothelial cells. Furthermore, PbA-specific CD8(+) T cell responses were augmented in the blood of Cyld(-/-) mice with increased production of interferon-γ and granzyme B and elevated activation of protein kinase C-θ and nuclear factor "kappa light-chain enhancer" of activated B cells. Importantly, accumulation of CD8(+) T cells in the brain of Cyld(-/-) mice was significantly reduced compared to C57BL/6 mice. Bone marrow chimera experiments showed that the absence of ECM signatures in infected Cyld(-/-) mice could be attributed to hematopoietic and radioresistant parenchymal cells, most likely endothelial cells that did not undergo apoptosis. Together, we were able to show that host deubiqutinating enzymes play an important role in ECM and that CYLD promotes ECM supporting it as a potential therapeutic target for adjunct therapy to prevent cerebral complications of severe malaria.
    • A Listeria monocytogenes ST2 clone lacking chitinase ChiB from an outbreak of non-invasive gastroenteritis.

      Halbedel, Sven; Prager, Rita; Banerji, Sangeeta; Kleta, Sylvia; Trost, Eva; Nishanth, Gopala; Alles, Georg; Hölzel, Christina; Schlesiger, Friederike; Pietzka, Ariane; et al. (Springer Nature, 2019-01-01)
      An outbreak with a remarkable Listeria monocytogenes clone causing 163 cases of non-invasive listeriosis occurred in Germany in 2015. Core genome multi locus sequence typing grouped non-invasive outbreak isolates and isolates obtained from related food samples into a single cluster, but clearly separated genetically close isolates obtained from invasive listeriosis cases. A comparative genomic approach identified a premature stop codon in the chiB gene, encoding one of the two L. monocytogenes chitinases, which clustered with disease outcome. Correction of this premature stop codon in one representative gastroenteritis outbreak isolate restored chitinase production, but effects in infection experiments were not found. While the exact role of chitinases in virulence of L. monocytogenes is still not fully understood, our results now clearly show that ChiB-derived activity is not required to establish L. monocytogenes gastroenteritis in humans. This limits a possible role of ChiB in human listeriosis to later steps of the infection.