Neutrophil extracellular trap (NET) formation can generate short-term, functional anucleate cytoplasts and trigger loss of cell viability. We demonstrated that the necroptotic cell death effector mixed lineage kinase domain-like (MLKL) translocated from the cytoplasm to the plasma membrane and stimulated downstream NADPH oxidase-independent ROS production, loss of cytoplasmic granules, breakdown of the nuclear membrane, chromatin decondensation, histone hypercitrullination, and extrusion of bacteriostatic NETs. This process was coordinated by receptor-interacting protein kinase-1 (RIPK1), which activated the caspase-8-dependent apoptotic or RIPK3/MLKL-dependent necroptotic death of mouse and human neutrophils. Genetic deficiency of RIPK3 and MLKL prevented NET formation but did not prevent cell death, which was because of residual caspase-8-dependent activity. Peptidylarginine deiminase 4 (PAD4) was activated downstream of RIPK1/RIPK3/MLKL and was required for maximal histone hypercitrullination and NET extrusion. This work defines a distinct signaling network that activates PAD4-dependent NET release for the control of methicillin-resistant (MRSA) infection.

SUMMARY The co-engagement of fragment crystallizable (Fc) gamma receptors (FcγRs) with the Fc region of recombinant immunoglobulin monoclonal antibodies (mAbs) and its contribution to therapeutic activity has been extensively studied. For example, Fc-FcγR interactions have been shown to be important for mAb-directed effector cell activities, as well as mAb-dependent forward signaling into target cells via receptor clustering. Here we identify a function of mAbs targeting T cell-expressed antigens that involves FcγR co-engagement on antigen-presenting cells (APCs). In the case of mAbs targeting CTLA-4 and TIGIT, the interaction with FcγR on APCs enhanced antigen-specific T cell responses and tumoricidal activity. This mechanism extended to an anti-CD45RB mAb, which led to FcγR-dependent regulatory T cell expansion in mice.

No abstract

Our results demonstrated that extrinsic, mitochondrial and possibly ER pathways are inducers of germ cell apoptosis in EAO and that Bax and Bcl-2 proteins modulate this process.

Experimental autoimmune orchitis (EAO) is characterized by an interstitial lymphomononuclear cell infiltration and a severe lesion of seminiferous tubules (ST) with germ cells that undergo apoptosis and sloughing. The aim of this study was to analyse the expression and localization of adherens junction (AJ) proteins: N-cadherin, α-, β- and p120 catenins and gap junction protein, connexin 43 (Cx43), to explore some aspects of germ-cell sloughing during the development of orchitis. EAO was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Concomitant with early signs of germ-cell sloughing, we observed by immunofluorescence and Western blot, a delocalization and a significant increase in N-cadherin and α-catenin expression in the ST of EAO compared with C rats. In spite of this increased AJ protein expression, a severe germ-cell sloughing occurred. This is probably due to the impairment of the AJ complex function, as shown by the loss of N-cadherin/β-catenin colocalization (confocal microscopy) and increased pY654 β-catenin expression, suggesting lower affinity of these two proteins and increased pERK1/2 expression in the testis of EAO rats. The significant decrease in Cx43 expression detected in EAO rats suggests a gap junction function impairment also contributing to germ-cell sloughing.

No abstract

T-cell immunoreceptor with Ig and ITIM domains (TIGIT) has emerged as an important regulator of the cancer-immunity cycle. Preclinical studies have demonstrated that TIGIT antibodies can enhance T and NK cell anti-tumor immunity, and therapeutic antibodies targeting TIGIT are advancing in the clinic. Nonetheless, questions on the optimal format for TIGIT therapeutics remain unresolved. Preclinical studies have demonstrated that anti-TIGIT antibodies enhance anti-tumor immunity by (1) blocking inhibitory signaling downstream of TIGIT/PVR and TIGIT/PVRL2 receptor-ligand interactions and (2) redirecting PVR/PVRL2 ligand binding to the co-stimulatory receptor CD226. Here we describe a novel and unanticipated mechanism of action of anti-TIGIT antibodies in which interactions between the antibody Fc domain and select FcγRs, particularly FcγRIIIA, dramatically improve T cell activation and effector function. In mouse tumor models, TIGIT antibodies that promote FcγR interactions enhance anti-tumor responses, whereas Fc-inert TIGIT antibodies show no such benefit. Moreover, TIGIT antibodies that enhance binding to human FcγRIIIA or mouse FcγRIV promote superior single agent activity and combination activity with other checkpoint modulators in antigen-stimulation assays and mouse tumor models respectively. Notably, this mechanism of action is independent of regulatory T cell depletion. Our findings support a dependence on Fc-FcγR interaction for promoting T cell responsiveness and effector function upon TIGIT antagonism. We further demonstrate that this novel mechanism also extends to anti-CTLA-4, but not anti-PD-1 or anti-LAG-3 antibodies. Altogether, our data describe a novel FcγR-dependent mechanism of action that may enhance the therapeutic activity of anti-TIGIT antibodies, deepen our understanding of this class of therapies, and inform on the optimal design for a new class of Fc-engineered antibodies that could be leveraged to potentially enhance antitumor immune responses. Citation Format: Dhan Chand, Jeremy D. Waight, Elena Paltrinieri, Sylvia Dietrich, Mark Bushell, Mathew Costa, Randi Gombos, Nicholas S. Wilson, Jennifer S. Buell, Robert B. Stein, Alexander Duncan, David A. Savitsky. FcgR co-engagement by anti-TIGIT monoclonal antibodies enhances T cell functionality and antitumor immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2390.

Gene "7" of Escherichia coli phage K1E was proposed to encode a novel DNA-dependent RNA polymerase (RNAP). The corresponding protein was produced recombinantly, purified to apparent homogeneity via affinity chromatography, and successfully employed for in vitro RNA synthesis. Optimal assay conditions (pH 8, 37 degrees C, 10 mM magnesium chloride and 1.3 mM spermidine) were established. The corresponding promoter regions were identified on the phage genome and summarized in a sequence logo. Surprisingly, next to K1E promoters, the SP6 promoter was also recognized efficiently in vitro by K1E RNAP, while the T7 RNAP promoter was not recognized at all. Based on these results, a system for high-yield in vitro RNA synthesis using K1E RNAP was established. The template plasmid is a pUC18 derivative, which enables blue/white screening for positive cloning of the target DNA. Production of more than 5 microg of purified RNA per microgram plasmid DNA was achieved. Finally, in vivo protein production systems for Bacillus megaterium were established based on K1E and SP6 phage RNAP transcription. Up to 61.4 mg g (CDW) (-1) (K1E RNAP) of the reporter protein Gfp was produced in shaking flask cultures of B. megaterium.