Purpose Reovirus is a naturally occurring oncolytic virus in clinical trials. Although tumor infection by reovirus can generate adaptive antitumor immunity, its therapeutic importance versus direct viral oncolysis is undefined. This study addresses the requirement for viral oncolysis and replication, and the relative importance of antitumor immunity and direct oncolysis in therapy. Experimental Design Nonantigen specific T cells loaded with reovirus were delivered i.v. to C57BL/6 and severe combined immunodeficient mice bearing lymph node and splenic metastases from the murine melanoma, B16ova, with assessment of viral replication, metastatic clearance by tumor colony outgrowth, and immune priming. Human cytotoxic lymphocyte priming assays were done with dendritic cells loaded with Mel888 cells before the addition of reovirus. Results B16ova was resistant to direct oncolysis in vitro, and failed to support reovirus replication in vitro or in vivo. Nevertheless, reovirus purged lymph node and splenic metastases in C57BL/6 mice and generated antitumor immunity. In contrast, reovirus failed to reduce tumor burden in severe combined immunodeficient mice bearing either B16ova or reovirus-sensitive B16tk metastases. In the human system, reovirus acted solely as an adjuvant when added to dendritic cells already loaded with Mel888, supporting priming of specific antitumor cytotoxic lymphocyte, in the absence of significant direct tumor oncolysis; UV-treated nonreplicating reovirus was similarly immunogenic. Conclusion The immune response is critical in mediating the efficacy of reovirus, and does not depend upon direct viral oncolysis or replication. The findings are of direct relevance to fulfilling the potential of this novel anticancer agent.

INTRODUCTIONThe biogenic amine histamine, 2-(1H-imidazol-4-yl)-ethanamine, is produced by decarboxylation of L-histidine and is implicated in a wide range of physiological and pathophysiological functions. It is metabolised by histamine N tmethyltransferase (HMT) and mono-or diaminoxidase. Histamine is mainly acting via four distinct metabotropic histamine receptor subtypes (H 1 R-H 4 R), which have meanwhile all been cloned. Whereas antagonists for H 1 R and H 2 R subtypes have been blockbusters in therapy of allergy and ulcer, respectively, antagonists for H 3 R and H 4 R subtypes are not on the market. The recently described H 4 R seems to be involved in inflammatory and immunomodulatory processes. H 3 Rs play a central role in neurotransmission of histamine and in control of many other neurotransmitters. Several antagonists are in preclinical and some in clinical stage of development. PHARMACOLOGICAL BACKGROUND Auto-and HeteroreceptorThe H 3 R was first described in 1983 as a presynaptic autoreceptor, which mediates synthesis of histamine and inhibition of its release from histaminergic neurons in slices of rat cerebral cortex. 1) Localisation studies in rodents show a predominance in distinct regions of the central nervous system (CNS) as the H 3 R is mainly located in cerebral cortex, hippocampus, amygdala, nucleus accumbens, globus pallidus, striatum, and hypothalamus 2-5) ( Fig. 1). In addition, it is expressed in the peripheral nervous system, e.g. in gastrointestinal tract, airways and cardiovascular system. 6) Molecular aspects of the receptor, [7][8][9][10] structure-activity relationships (SAR) of ligands, [11][12][13][14][15][16][17][18][19] and pharmacology [20][21][22][23][24][25][26] have recently been resumed in many excellent reviews. This contribution focuses on the development of clinical candidates and the multifaceted potential indications targeted.In mammalian brain histaminergic neurons originate in the tuberomammillary nucleus (TMN) spreading into above mentioned brain regions, where they control histamine levels by regulation of synthesis and liberation rates 27) and modulate different neuronal systems. 28) H 3 R expression is not solely restricted to histaminergic neurons: due to its function as a heteroreceptor it can be found on colocalised neurons, and H 3 R activation modulates the release of various important neurotransmitters, i.e. dopamine, [29][30][31][32][33] acetylcholine, [34][35][36][37] norepinephrine, 38,39) serotonin, 40,41) GABA, [42][43][44] glutamate, 45) and substance P. [46][47][48] Therefore, histaminergic neurons and the cross-linkage between major neurotransmitter systems are involved in many (patho)physiological brain functions, including vigilance, memory processes, feeding behaviour and locomotor activity (Fig. 2). Interneuron cross-talk and adaptive processes seem to be important factors in H 3 Rmediated signalling. Molecular AspectsThe human histamine H 3 receptor (hH 3 R) cDNA firstly described 1999 encodes a 445 amino acid protein and belongs to the his...

The application of adoptive T cell therapies, including those using chimeric antigen receptor (CAR)-modified T cells, to solid tumors requires combinatorial strategies to overcome immune suppression associated with the tumor microenvironment. Here we test whether the inflammatory nature of oncolytic viruses and their ability to remodel the tumor microenvironment may help to recruit and potentiate the functionality of CAR T cells. Contrary to our hypothesis, VSVmIFNβ infection is associated with attrition of murine EGFRvIII CAR T cells in a B16EGFRvIII model, despite inducing a robust proinflammatory shift in the chemokine profile. Mechanistically, type I interferon (IFN) expressed following infection promotes apoptosis, activation, and inhibitory receptor expression, and interferon-insensitive CAR T cells enable combinatorial therapy with VSVmIFNβ. Our study uncovers an unexpected mechanism of therapeutic interference, and prompts further investigation into the interaction between CAR T cells and oncolytic viruses to optimize combination therapy.

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