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Purpose ATR inhibitors (ATRi) are in early phase clinical trials and have been shown to sensitise to chemotherapy and radiotherapy preclinically. Limited data have been published about the effect of these drugs on the tumor microenvironment. Experimental Design We used an immunocompetent mouse model of HPV-driven malignancies to investigate the ATR inhibitor AZD6738 in combination with fractionated radiation (RT). Gene expression analysis and flow cytometry were performed post-therapy. Results Significant radiosensitization to RT by ATRi was observed alongside a marked increase in immune cell infiltration. We identified increased numbers of CD3+ and NK cells but most of this infiltrate was composed of myeloid cells. ATRi plus radiation produced a gene expression signature matching a type I/II interferon response with upregulation of genes playing a role in nucleic acid sensing. Increased MHC I levels were observed on tumor cells, with transcript-level data indicating increased antigen processing and presentation within the tumor. Significant modulation of cytokine gene expression (particularly CCL2, CCL5 and CXCL10) was found in vivo, with in vitro data indicating CCL3, CCL5 and CXCL10 are produced from tumor cells after ATRi + RT. Conclusions We show that DNA damage by ATRi and RT leads to an interferon response through activation of nucleic acid sensing pathways. This triggers increased antigen presentation and innate immune cell infiltration. Further understanding of the effect of this combination on the immune response may allow modulation of these effects to maximise tumor control through anti-tumor immunity.

Over the last decade, invasive fungal infections have emerged as a growing threat to human health worldwide and novel treatment strategies are urgently needed. In this context, investigations into host-pathogen interactions represent an important and promising field of research. Antigen presenting cells such as macrophages and dendritic cells are strategically located at the frontline of defence against potential invaders. Importantly, these cells express germline encoded pattern recognition receptors (PRRs), which sense conserved entities from pathogens and orchestrate innate immune responses. Herein, we review the latest findings regarding the biology and functions of the different classes of PRRs involved in pathogenic fungal recognition. We also discuss recent literature on PRR collaboration/crosstalk and the mechanisms involved in inhibiting/regulating PRR signalling. Finally, we discuss how the accumulated knowledge on PRR biology, especially Dectin-1, has been used for the design of new immunotherapies against fungal infections.

The macrophage-inducible C-type lectin (Mincle) is an innate immune receptor on myeloid cells sensing diverse entities including pathogens and damaged cells. Mincle was first described as a receptor for the mycobacterial cell wall glycolipid, trehalose-6,6′-dimycolate, or cord factor, and the mammalian necrotic cell-derived alarmin histone deacetylase complex unit Sin3-associated protein 130. Upon engagement by its ligands, Mincle induces secretion of innate cytokines and other immune mediators modulating inflammation and immunity. Since its discovery more than 25 years ago, the understanding of Mincle’s immune function has made significant advances in recent years. In addition to mediating immune responses to infectious agents, Mincle has been linked to promote tumor progression, autoimmunity, and sterile inflammation; however, further studies are required to completely unravel the complex role of Mincle in these distinct host responses. In this review, we discuss recent findings on Mincle’s biology with an emphasis on its diverse functions in immunity.

PfCDPK1 is a Plasmodium falciparum calcium-dependent protein kinase, which has been identified as a potential target for novel antimalarial chemotherapeutics. In order to further investigate the role of PfCDPK1, we established a high-throughput in vitro biochemical assay and used it to screen a library of over 35,000 small molecules. Five chemical series of inhibitors were initially identified from the screen, from which series 1 and 2 were selected for chemical optimization. Indicative of their mechanism of action, enzyme inhibition by these compounds was found to be sensitive to both the ATP concentration and substitution of the amino acid residue present at the “gatekeeper” position at the ATP-binding site of the enzyme. Medicinal chemistry efforts led to a series of PfCDPK1 inhibitors with 50% inhibitory concentrations (IC50s) below 10 nM against PfCDPK1 in a biochemical assay and 50% effective concentrations (EC50s) less than 100 nM for inhibition of parasite growth in vitro. Potent inhibition was combined with acceptable absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties and equipotent inhibition of Plasmodium vivax CDPK1. However, we were unable to correlate biochemical inhibition with parasite growth inhibition for this series overall. Inhibition of Plasmodium berghei CDPK1 correlated well with PfCDPK1 inhibition, enabling progression of a set of compounds to in vivo evaluation in the P. berghei rodent model for malaria. These chemical series have potential for further development as inhibitors of CDPK1.

Candida spp. elicit cytokine production downstream of various pathogen recognition receptors, including C-type lectin-like receptors, TLRs, and nucleotide oligomerization domain (NOD)–like receptors. IL-12 family members IL-12p70 and IL-23 are important for host immunity against Candida spp. In this article, we show that IL-27, another IL-12 family member, is produced by myeloid cells in response to selected Candida spp. We demonstrate a novel mechanism for Candida parapsilosis–mediated induction of IL-27 in a TLR7-, MyD88-, and NOD2-dependent manner. Our data revealed that IFN-β is induced by C. parapsilosis, which in turn signals through the IFN-α/β receptor and STAT1/2 to induce IL-27. Moreover, IL-27R (WSX-1)–deficient mice systemically infected with C. parapsilosis displayed enhanced pathogen clearance compared with wild-type mice. This was associated with increased levels of proinflammatory cytokines in the serum and increased IFN-γ and IL-17 responses in the spleens of IL-27R–deficient mice. Thus, our data define a novel link between C. parapsilosis, TLR7, NOD2, IFN-β, and IL-27, and we have identified an important role for IL-27 in the immune response against C. parapsilosis. Overall, these findings demonstrate an important mechanism for the suppression of protective immune responses during infection with C. parapsilosis, which has potential relevance for infections with other fungal pathogens.

The causative agent of tuberculosis, Mycobacterium tuberculosis (M. tuberculosis), contains an abundant cell wall glycolipid and a crucial virulence factor, trehalose-6,6’-dimycolate (TDM). TDM causes delay of phagosome maturation and thus promotes survival of mycobacteria inside host macrophages by a not fully understood mechanism. TDM signals through the Monocyte-INducible C-type LEctin (Mincle), a recently identified pattern recognition receptor. Here we show that recruitment of Mincle by TDM coupled to immunoglobulin (Ig)G-opsonised beads during Fcγ receptor (FcγR)-mediated phagocytosis interferes with phagosome maturation. In addition, modulation of phagosome maturation by TDM requires SH2-domain-containing inositol polyphosphate 5’ phosphatase (SHP-1) and the FcγRIIB, which strongly suggests inhibitory downstream signalling of Mincle during phagosome formation. Overall, our study reveals important mechanisms contributing to the virulence of TDM.

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