Spaceflight-Associated Immune System Modifications

Spaceflight is an adverse environment characterized by a unique combination of stressors affecting almost all physiological systems, including the immune system. Indeed, several studies have shown that about 50% of the astronauts have faced immunological troubles. Here, we will review how spaceflight affects immune cell development, innate as well as adaptive immunity, required to ensure an efficient protection of the host, with a particular focus on T and B cells. Indeed, to better appreciate the risks associated to future long-duration space missions and to develop pharmacologic or nutritional countermeasures allowing immune system protection, it is mandatory to fully understand how these cell types are affected by space conditions. Finally, we will compare immune changes observed in astronauts with those encountered in the elderly, thereby illustrating the societal interest of space research

Low STING expression in a transplantable KrasG12D/P53ko lung cancer model contributes to SiglecF+ neutrophil and CD103+Treg accumulation in tumors

Lung cancer is the leading cause of mortality by cancer worldwide. Non-small cell lung cancer is the most common type of lung cancer and mutations in the KRAS gene are frequently found in this pathology. While immune checkpoint inhibitors are providing new hope for lung cancer care, only a subset of patients show durable benefit from these new therapies designed to drive an efficient anti-tumor immune response. Hence, it is crucial to better understand the mechanisms through which the tumor immune microenvironment is established in lung tumors. Using bioinformatics, we observed that high expression of the STimulator of INterferon Gene (STING) associates with a longer overall survival specifically in KRAS mutant cancer patients. In lung cancer cell lines, STING expression is linked to interferon response and epithelial-to-mesenchymal transition. Because STING activation in immune cells of the tumor microenvironment using specific agonists is an emerging strategy to trigger an anti-tumor immune response, we took advantage of two transplantable models of Kras driven lung cancer, expressing high or low levels of STING, to investigate the function of STING directly in cancer cells in vivo. We observed that high-STING expression and constitutive STING signaling were critical for transplanted tumor formation rather than playing a major role in tumor immunogenicity. Besides, low-STING expression in cancer cells is associated with an immunosuppressive tumor microenvironment characterized by the accumulation of tumor promoting SiglecF+ neutrophils and CD103+ regulatory T cells. In that model, knocking out STING increased the early response to anti-PD1 treatment. We conclude that low-STING expression in cancer cells might confer them an independence from pro-inflammatory signals and a greater immunosuppressive capability and aggressiveness

Gravitational Experimental Platform for Animal Models, a New Platform at ESA’s Terrestrial Facilities to Study the Effects of Micro- and Hypergravity on Aquatic and Rodent Animal Models

Using rotors to expose animals to different levels of hypergravity is an efficient means of understanding how altered gravity affects physiological functions, interactions between physiological systems and animal development. Furthermore, rotors can be used to prepare space experiments, e.g., conducting hypergravity experiments to demonstrate the feasibility of a study before its implementation and to complement inflight experiments by comparing the effects of micro- and hypergravity. In this paper, we present a new platform called the Gravitational Experimental Platform for Animal Models (GEPAM), which has been part of European Space Agency (ESA)’s portfolio of ground-based facilities since 2020, to study the effects of altered gravity on aquatic animal models (amphibian embryos/tadpoles) and mice. This platform comprises rotors for hypergravity exposure (three aquatic rotors and one rodent rotor) and models to simulate microgravity (cages for mouse hindlimb unloading and a random positioning machine (RPM)). Four species of amphibians can be used at present. All murine strains can be used and are maintained in a specific pathogen-free area. This platform is surrounded by numerous facilities for sample preparation and analysis using state-of-the-art techniques. Finally, we illustrate how GEPAM can contribute to the understanding of molecular and cellular mechanisms and the identification of countermeasures

N-protein mobilisation associated with the leaf senescence process in oilseed rape is concomitant with the disappearence of trypsin inhibitor activity

Brassica napus L. ( oilseed rape) is an important crop plant characterised by low nitrogen ( N) use efficiency. This is mainly due to a weak N recycling from leaves that is related to incomplete protein degradation. Assuming that protease inhibitors are involved throughout protein mobilisation, the goal of this study was to determine their role in the control of N mobilisation associated with leaf senescence. Results showed that a 19-kDa polypeptide exhibiting trypsin inhibitor ( TI) activity presented an increased gradient from the older to the younger leaves. According to the SAG12/Cab gene expression pro. le, which is an indicator of leaf senescence, mature leaves of nitrate-deprived plants presented an earlier initiation of senescence and a decrease in protein concentration when compared with nitrate-replete plants. This coincided with disappearance of both TI activity and a reduction in the transcript level of the BnD22 gene ( encoding a protein sharing homology with Kunitz protease inhibitor). In young leaves of N-deprived plants, initiation of senescence was delayed; soluble protein concentration was maintained while both TI activity and BnD22 transcripts were high. This indicates that in oilseed rape growing under nitrate deprivation, the more efficient N recycling from mature leaves contributes to the maintenance of growth in young leaves. The data suggest a significant role for protease inhibitors in the regulation of proteolytic processes associated with N mobilisation during leaf senescence

Minerals and Antioxidant Micronutrients Levels and Clinical Outcome in Older Patients Hospitalized for COVID-19 during the First Wave of the Pandemic

International audienceExcessive inflammatory response has been implicated in severe respiratory forms of coronavirus disease 2019 (COVID-19). Trace elements such as zinc, selenium, and copper are known to modulate inflammation and immunity. This study aimed to assess the relationships between antioxidant vitamins and mineral trace elements levels as well as COVID-19 severity in older adults hospitalized. In this observational retrospective cohort study, the levels of zinc, selenium, copper, vitamin A, β-carotene, and vitamin E were measured in 94 patients within the first 15 days of hospitalization. The outcomes were in-hospital mortality secondary to COVID-19 or severe COVID-19. A logistic regression analysis was conducted to test whether the levels of vitamins and minerals were independently associated with severity. In this cohort (average age of 78 years), severe forms (46%) were associated with lower zinc (p = 0.012) and β-carotene (p < 0.001) concentrations, and in-hospital mortality (15%) was associated with lower zinc (p = 0.009), selenium (p = 0.014), vitamin A (p = 0.001), and β-carotene (p = 0.002) concentrations. In regression analysis, severe forms remained independently associated with lower zinc (aOR 2.13, p = 0.018) concentrations, and death was associated with lower vitamin A (aOR = 0.165, p = 0.021) concentrations. Low plasma concentrations of zinc and vitamin A were associated with poor prognosis in older people hospitalized with COVID-19

B-cell homeostasis is maintained during two months of head-down tilt bed rest with or without antioxidant supplementation

Alterations of the immune system could seriously impair the ability to combat infections during future long-duration space missions. However, little is known about the effects of spaceflight on the B-cell compartment. Given the limited access to astronaut samples, we addressed this question using blood samples collected from 20 healthy male volunteers subjected to long-duration bed rest, an Earth-based analog of spaceflight. Hematopoietic progenitors, white blood cells, total lymphocytes and B-cells, four B-cell subsets, immunoglobulin isotypes, six cytokines involved in inflammation, cortisone and cortisol were quantified at five time points. Tibia microarchitecture was also studied. Moreover, we investigated the efficiency of antioxidant supplementation with a cocktail including polyphenols, omega 3, vitamin E and selenium. Our results show that circulating hematopoietic progenitors, white blood cells, total lymphocytes and B-cells, and B-cell subsets were not affected by bed rest. Cytokine quantification suggested a lower systemic inflammatory status, supported by an increase in serum cortisone, during bed rest. These data confirm the in vivo hormonal dysregulation of immunity observed in astronauts and show that bed rest does not alter B-cell homeostasis. This lack of an impact of long-term bed rest on B-cell homeostasis can, at least partially, be explained by limited bone remodeling. None of the evaluated parameters were affected by the administration of the antioxidant supplement. The non-effectiveness of the supplement may be because the diet provided to the non-supplemented and supplemented volunteers already contained sufficient antioxidants. Given the limitations of this model, further studies will be required to determine whether B-cell homeostasis is affected, especially during future deep-space exploration missions that will be of unprecedented durations

Accumulation of MDSC and Th17 Cells in Patients with Metastatic Colorectal Cancer Predicts the Efficacy of a FOLFOX-Bevacizumab Drug Treatment Regimen

International audienceHost immunity controls the development of colorectal cancer, and chemotherapy used to treat colorectal cancer is likely to recruit the host immune system at some level. Athough preclinical studies have argued that colorectal cancer drugs, such as 5-fluorouracil (5-FU) and oxaliplatin, exert such effects, their combination as employed in the oncology clinic has not been evaluated. Here, we report the results of prospective immuno-monitoring of 25 metastatic colorectal cancer (mCRC) patients treated with a first-line combination regimen of 5-FU, oxaliplatin, and bevacizumab (FOLFOX-bevacizumab), as compared with 20 healthy volunteers. Before this therapy was initiated, T regulatory cells (Treg), Th17, and granulocytic myeloid-derived suppressor cells (gMDSC) were increased significantly in mCRC, but only a high level of gMDSC was associated with a poor prognosis. Chemotherapy modulated the Treg/Th17 balance by decreasing Treg and increasing Th17 cell frequency by 15 days after the start of treatment. Increased Th17 frequency was associated with a poor prognosis. FOL-FOX-bevacizumab treatment elicited a decrease in gMDSC in 15 of 25 patients and was associated with a better survival outcome. Notably, the gMDSCs that expressed high levels of PD-L1, CD39, and CD73 exerted a robust immunosuppressive activity, relative to other myeloid cells present in blood, which could be reversed by blocking the CD39/CD73 and PD-1/PD-L1 axes. Our work underscores the critical prognostic impact of early modifications in Th17 and gMDSC frequency in mCRC. Furthermore, it provides a clinical rationale to combine FOLFOX-bevacizumab chemotherapy with inhibitors of ATP ectonucleotidases and/or anti-PD-1/PD-L1 antibodies to more effectively treat this disease. (C) 2016 AACR

The therapeutic effectiveness of 177Lu-lilotomab in B-cell non- Hodgkin lymphoma involves modulation of G2/M cell cycle arrest

International audienceSome patients with B-cell non-Hodkin lymphoma Lymphoma (NHL) become refractory to rituximab (anti-CD20 antibody) therapy associated with chemotherapy. Here, the effect of the anti-CD37 antibody-radionuclide conjugate lutetium-177 (177Lu)-lilotomab (Betalutin®) was investigated in preclinical models of NHL. In SCID mice bearing DOHH2 (transformed follicular lymphoma, FL) cell xenografts, 177Lu-lilotomab significantly delayed tumor growth, even at low activity (100 MBq/kg). In athymic mice bearing OCI-Ly8 (diffuse large B-cell lymphoma, DLBCL) or Ramos (Burkitt's lymphoma) cell xenografts, 177Lu-lilotomab activity had to be increased to 500 MBq/kg to show a significant tumor growth delay. Clonogenic and proliferation assays showed that DOHH2 cells were highly sensitive to 177Lu-lilotomab, while Ramos cells were the least sensitive, and U2932 (DLBCL), OCI-Ly8, and Rec-1 (mantle cell lymphoma) cells displayed intermediate sensitivity. The strong 177Lu-lilotomab cytotoxicity observed in DOHH2 cells correlated with reduced G2/M cell cycle arrest, lower WEE-1- and MYT-1-mediated phosphorylation of cyclin-dependent kinase-1 (CDK1), and higher apoptosis. In agreement, 177Lu-lilotomab efficacy in vitro, in vivo, and in patient samples was increased when combined with G2/M cell cycle arrest inhibitors (MK-1775 and PD-166285). These results indicate that 177Lu-lilotomab is particularly efficient in treating tumors with reduced inhibitory CDK1 phosphorylation, such as transformed FL

Yeast Virus-Derived Stimulator of the Innate Immune System Augments the Efficacy of Virus Vector-Based Immunotherapy

International audienceTo identify novel stimulators of the innate immune system, we constructed a panel of eight HEK293 cell lines double positive for human Toll-like receptors (TLRs) and an NF-B-inducible reporter gene. Screening of a large variety of compounds and cellular extracts detected a TLR3-activating compound in a microsomal yeast extract. Fractionation of this extract identified an RNA molecule of 4.6 kb, named nucleic acid band 2 (NAB2), that was sufficient to confer the activation of TLR3. Digests with singleand double-strand-specific RNases showed the double-strand nature of this RNA, and its sequence was found to be identical to that of the genome of the double-stranded RNA (dsRNA) L-BC virus of Saccharomyces cerevisiae. A large-scale process of production and purification of this RNA was established on the basis of chemical cell lysis and dsRNA-specific chromatography. NAB2 complexed with the cationic lipid Lipofectin but neither NAB2 nor Lipofectin alone induced the secretion of interleukin-12(p70) [IL-12(p70)], alpha interferon, gamma interferon-induced protein 10, macrophage inflammatory protein 1␤, or IL-6 in human monocyte-derived dendritic cells. While NAB2 activated TLR3, Lipofectin-stabilized NAB2 also signaled via the cytoplasmic sensor for RNA recognition MDA-5. A significant increase of RMA-MUC1 tumor rejection and survival was observed in C57BL/6 mice after prophylactic vaccination with MUC1-encoding modified vaccinia virus Ankara (MVA) and NAB2-Lipofectin. This combination of immunotherapies strongly increased at the injection sites the percentage of infiltrating natural killer (NK) cells and plasmacytoid dendritic cells (pDCs), cell types which can modulate innate and adaptive immune responses. IMPORTANCE Virus-based cancer vaccines offer a good alternative to the treatment of cancer but could be improved. Starting from a screening approach, we have identified and characterized an unexplored biological molecule with immunomodulatory characteristics which augments the efficacy of an MVA-based immunotherapeutic agent. The immune modulator consists of the purified dsRNA genome isolated from a commercially used yeast strain, NAB2, mixed with a cationic lipid, Lipofectin. NAB2-Lipofectin stimulates the immune system via TLR3 and MDA-5. When it was injected at the MVA vaccination site, the immune modulator increased survival in a preclinical tumor model. We could demonstrate that NAB2-Lipofectin augments the MVA-induced infiltration of natural killer and plasmacytoid dendritic cells. We suggest indirect mechanisms of activation of these cell types by the influence of NAB2-Lipofectin on innate and adaptive immunity. Detailed analysis of cell migration at the vaccine injection site and the appropriate choice of an immune modulator should be considered to achieve the rational improvement of virus vectorbased vaccination by immune modulators