Dietary tryptophan metabolite released by intratumoral Lactobacillus reuteri facilitates immune checkpoint inhibitor treatment.

The use of probiotics by cancer patients is increasing, including among those undergoing immune checkpoint inhibitor (ICI) treatment. Here, we elucidate a critical microbial-host crosstalk between probiotic-released aryl hydrocarbon receptor (AhR) agonist indole-3-aldehyde (I3A) and CD8 T cells within the tumor microenvironment that potently enhances antitumor immunity and facilitates ICI in preclinical melanoma. Our study reveals that probiotic Lactobacillus reuteri (Lr) translocates to, colonizes, and persists within melanoma, where via its released dietary tryptophan catabolite I3A, it locally promotes interferon-γ-producing CD8 T cells, thereby bolstering ICI. Moreover, Lr-secreted I3A was both necessary and sufficient to drive antitumor immunity, and loss of AhR signaling within CD8 T cells abrogated Lr's antitumor effects. Further, a tryptophan-enriched diet potentiated both Lr- and ICI-induced antitumor immunity, dependent on CD8 T cell AhR signaling. Finally, we provide evidence for a potential role of I3A in promoting ICI efficacy and survival in advanced melanoma patients.

The microbiota control the neonatal WNT-ernet.

The microbiome plays a fundamental role in maintaining intestinal stem cell (ISC)-niche equilibrium. In this issue of Immunity, Kim and colleagues uncover a mechanism by which the microbiota drives macrophage WNT ligand-release to maintain ISC-niche homeostasis during early postnatal development.

Adenovirus-vectored SARS-CoV-2 vaccine expressing S1-N fusion protein.

Additional COVID-19 vaccines that are safe and immunogenic are needed for global vaccine equity. Here, we developed a recombinant type 5 adenovirus vector encoding for the SARS-CoV-2 S1 subunit antigen and nucleocapsid as a fusion protein (Ad5.SARS-CoV-2-S1N). A single subcutaneous immunization with Ad5.SARS-CoV-2-S1N induced a similar humoral response, along with a significantly higher S1-specific cellular response, as a recombinant type 5 adenovirus vector encoding for S1 alone (Ad5.SARS-CoV-2-S1). Immunogenicity was improved by homologous prime-boost vaccination, and further improved through intramuscular heterologous prime-boost vaccination using subunit recombinant S1 protein. Priming with low dose (1 × 1010 v.p.) of Ad5.SARS-CoV-2-S1N and boosting with either wild-type recombinant rS1 or B.1.351 recombinant rS1 induced a robust neutralizing response, which was sustained against Beta and Gamma SARS-CoV-2 variants. This novel Ad5-vectored SARS-CoV-2 vaccine candidate showed promising immunogenicity in mice and supports the further development of COVID-19-based vaccines incorporating the nucleoprotein as a target antigen.

Tet2 deficiency drives liver microbiome dysbiosis triggering Tc1 cell autoimmune hepatitis.

The triggers that drive interferon-γ (IFNγ)-producing CD8 T cell (Tc1 cell)-mediated autoimmune hepatitis (AIH) remain obscure. Here, we show that lack of hematopoietic Tet methylcytosine dioxygenase 2 (Tet2), an epigenetic regulator associated with autoimmunity, results in the development of microbiota-dependent AIH-like pathology, accompanied by hepatic enrichment of aryl hydrocarbon receptor (AhR) ligand-producing pathobionts and rampant Tc1 cell immunity. We report that AIH-like disease development is dependent on both IFNγ and AhR signaling, as blocking either reverts ongoing AIH-like pathology. Illustrating the critical role of AhR-ligand-producing pathobionts in this condition, hepatic translocation of the AhR ligand indole-3-aldehyde (I3A)-releasing Lactobacillus reuteri is sufficient to trigger AIH-like pathology. Finally, we demonstrate that I3A is required for L. reuteri-induced Tc1 cell differentiation in vitro and AIH-like pathology in vivo, both of which are restrained by Tet2 within CD8 T cells. This AIH-disease model may contribute to the development of therapeutics to alleviate AIH.

Systemic Immunoregulatory Consequences of Gut Commensal Translocation.

One major determinant of systemic immunity during homeostasis and in certain complex multifactorial diseases (e.g. cancer and autoimmune conditions), is the gut microbiota. These commensals can shape systemic immune responses via translocation of metabolites, microbial cell wall components, and viable microbes. In the last few years, bacterial translocation has revealed itself as playing a key, and potentially causal role in mediating immunomodulatory processes in nongastrointestinal diseases. Moreover, recent observations regarding the presence of complex microbial communities and viable bacteria within gut-distal tissues during homeostasis challenge the current paradigm that healthy mammals are entirely sterile at nonmucosal sites. This review discusses our current understanding of how the gut microbiota orchestrates systemic immunity during noninfectious extraintestinal diseases and homeostasis, focusing on the translocation of viable bacteria to gut-distal sites.

Fascin-1 knock-down of human glioma cells reduces their microvilli/filopodia while improving their susceptibility to lymphocyte-mediated cytotoxicity.

Cancer cells derived from Glioblastoma multiforme possess membranous protrusions allowing these cells to infiltrate surrounding tissue, while resisting lymphocyte cytotoxicity. Microvilli and filopodia are supported by actin filaments cross-linked by fascin. Fascin-1 was genetically silenced within human U251 glioma cells; these knock-down glioma cells lost their microvilli/filopodia. The doubling time of these fascin-1 knock-down cells was doubled that of shRNA control U251 cells. Fascin-1 knock-down cells lost their transmigratory ability responding to interleukin-6 or insulin-like growth factor-1. Fascin-1 silenced U251 cells were more easily killed by cytolytic lymphocytes. Fascin-1 knock-down provides unique opportunities to augment glioma immunotherapy by simultaneously targeting several key glioma functions: like cell transmigration, cell division and resisting immune responses.

Long-range architecture in a viral RNA genome.

We have developed a model for the secondary structure of the 1058-nucleotide plus-strand RNA genome of the icosahedral satellite tobacco mosaic virus (STMV) using nucleotide-resolution SHAPE chemical probing of the viral RNA isolated from virions and within the virion, perturbation of interactions distant in the primary sequence, and atomic force microscopy. These data are consistent with long-range base pairing interactions and a three-domain genome architecture. The compact domains of the STMV RNA have dimensions of 10-45 nm. Each of the three domains corresponds to a specific functional component of the virus: The central domain corresponds to the coding sequence of the single (capsid) protein encoded by the virus, whereas the 5' and 3' untranslated domains span signals essential for translation and replication, respectively. This three-domain architecture is compatible with interactions between the capsid protein and short RNA helices previously visualized by crystallography. STMV is among the simplest of the icosahedral viruses but, nonetheless, has an RNA genome with a complex higher-order structure that likely reflects high information content and an evolutionary relationship between RNA domain structure and essential replicative functions.

Ionic liquids and acid gas capture: water and oxygen as confounding factors.

Amines dissolved in ionic liquids react rapidly with SO(2) to produce new materials. Compounds related to the stepwise conversion of SO(2) to sulfite and sulfate salts have been isolated. Trapping SO(2) in the form of the sulfite anion does not change the oxidation state of sulfur and should maintain the reversibility of the capture system.

Glioma cells display complex cell surface topographies that resist the actions of cytolytic effector lymphocytes.

Gliomas are invasive cancers that resist all forms of attempted therapy. Immunotherapy using Ag-pulsed dendritic cells has improved survival in some patients. We present evidence that another level of complexity may also contribute to lack of responses by the lymphocytes toward gliomas. Atomic force microscopy of four different glioma types-human U251 and rat T9 and F98 glioma cells, including freshly isolated human glioblastoma multiforme neurosphere cultures (containing "stem cell-like cells")-revealed a complex surface topography with numerous microvilli and filopodia. These structures were not found on other cell types. Electron microscopy and immunofluorescence microscopy of glioma cells confirmed that microvilli are present. U251 cells with microvilli resisted the cytolytic actions of different human effector cells, (lymphokine-activated killer cells, γδ T cells, conventional CTLs, and chimeric Ag-receptor-redirected T cells) better than their nonmicrovilli-expressing counterparts. Killer lymphocytes released perforin, which was detected within the glioma's microvilli/filopodia, indicating these structures can receive the cytolytic effector molecules, but cytotoxicity is suboptimal. Air-dried gliomas revealed nodes within the microvilli/filopodia. The microvilli that penetrated 0.4-µm transwell chamber's pores resisted the actions of CTLs and physical damage. Those nodelike structures may represent a compartmentalization that resists physical damage. These microvilli may play multiple roles in glioma biology, such as invasion and resistance to lymphocyte-mediated killing.

Acid ceramidase upregulation in prostate cancer cells confers resistance to radiation: AC inhibition, a potential radiosensitizer.

Radiation resistance in a subset of prostate tumors remains a challenge to prostate cancer radiotherapy. The current study on the effects of radiation on prostate cancer cells reveals that radiation programs an unpredicted resistance mechanism by upregulating acid ceramidase (AC). Irradiated cells demonstrated limited changes of ceramide levels while elevating levels of sphingosine and sphingosine-1-phosphate. By genetically downregulating AC with small interfering RNA (siRNA), we observed radiosensitization of cells using clonogenic and cytotoxicity assays. Conversely, AC overexpression further decreased sensitivity to radiation. We also observed that radiation-induced AC upregulation was sufficient to create cross-resistance to chemotherapy as demonstrated by decreased sensitivity to Taxol and C(6) ceramide compared to controls. Lower levels of caspase 3/7 activity were detected in cells pretreated with radiation, also indicating increased resistance. Finally, utilization of the small molecule AC inhibitor, LCL385, sensitized PPC-1 cells to radiation and significantly decreased tumor xenograft growth. These data suggest a new mechanism of cancer cell resistance to radiation, through upregulation of AC that is, in part, mediated by application of the therapy itself. An improved understanding of radiotherapy and the application of combination therapy achieved in this study offer new opportunities for the modulation of radiation effects in the treatment of cancer.

TY3 GAG3 protein forms ordered particles in Escherichia coli.

The yeast retrovirus-like element Ty3 GAG3 gene encodes a Gag3 polyprotein analogous to retroviral Gag. Gag3 lacks matrix, but contains capsid, spacer, and nucleocapsid domains. Expression of a Ty3 Gag3 or capsid domain optimized for expression in Escherichia coli was sufficient for Ty3 particle assembly. Virus-like ordered particles assembled from Gag3 were similar in size to immature particles from yeast and contained nucleic acid. However, particles assembled from the CA domain were variable in size and displayed much less organization than native particles. These results indicate that assembly can be driven through interactions among capsid subunits in the particle, but that the nucleocapsid domain, likely in association with RNA, confers order upon this process.