Immunization with an inactivated virus is one of the strategies currently being tested towards developing a SARS-CoV-2 vaccine. One of the methods used to inactivate viruses is exposure to high doses of ionizing radiation to damage their nucleic acids. While gamma (γ) rays effectively induce lesions in the RNA, envelope proteins are also highly damaged in the process. This in turn may alter their antigenic properties, affecting their capacity to induce an adaptive immune response able to confer effective protection. Here, we modeled the effect of sparsely and densely ionizing radiation on SARS-CoV-2 using the Monte Carlo toolkit Geant4-DNA. With a realistic 3D target virus model, we calculated the expected number of lesions in the spike and membrane proteins, as well as in the viral RNA. Our findings showed that γ rays produced significant spike protein damage, but densely ionizing charged particles induced less membrane damage for the same level of RNA lesions, because a single ion traversal through the nuclear envelope was sufficient to inactivate the virus. We propose that accelerated charged particles produce inactivated viruses with little structural damage to envelope proteins, thereby representing a new and effective tool for developing vaccines against SARS-CoV-2 and other enveloped viruses.

MR-linac technology enhances the precision of therapeutic radiation by clarifying the tumor-normal tissue interface and provides the potential for adaptive treatment planning. Accurate delineation of tumors on diagnostic magnetic resonance imaging (MRI) frequently requires gadolinium-based contrast agents (GBCAs). Despite generally being considered safe, previous literature suggests that GBCAs are capable of contrast-induced acute kidney injury (AKI). It is unclear if the risk for AKI is enhanced when GBCAs are administered concurrently with ionizing radiotherapy. During irradiation, gadolinium may be liberated from its chelator which may induce AKI. The goal of this work was to determine if radiation combined with GBCAs increased the incidence of AKI. Using a preclinical MRI-guided irradiation system, where MRI acquisitions and radiation delivery are performed in rapid succession, tumor-bearing mice with normal kidney function were injected with GBCA and treated with 2, 8 or 18 Gy irradiation. Renal function was assessed on days three and seven postirradiation to assess for AKI. No clinically relevant changes in blood urea nitrogen and creatinine were observed in any combination of GBCA and radiation dose. From these data, we conclude that GBCA in combination with radiation does not increase the risk for AKI in mice. Additional investigation of multiple doses of GBCA administered concurrently with irradiation is warranted to evaluate the risk of chronic kidney injury.

The effects of radiation exposure on germ cells and the gonads have been well studied at acute high-dose exposures, but the effects of chronic low-dose-rate (LDR) irradiation, particularly relevant for radiation protection, on germ cells and the gonads are largely unknown. Our previous study revealed that chronic exposure of mice to medium-dose-rate (MDR, 200 or 400 mGy/day) gamma-rays in utero for the entire gestation period (18 days) induced only a mild degree of general growth retardation, but with very drastic effects on the gonads and germ cells. In the current study, we further investigated the histomorphological changes in the gonads and the number of germ cells from gestation day (GD) 18 fetuses irradiated with MDR throughout the entire gestation period. The germ cells in the testes and ovaries of the MDR-irradiated fetuses were almost obliterated. Gestation day 18 fetuses exposed to LDR (20 mGy/day) radiation for the entire gestation period showed decreases in the number of the germ cells, which were not statistically significant or only marginally significant at most. Further investigations on the effects of LDR irradiation in utero using more sensitive methods are necessary.

In this work, individual radiosensitivity was evaluated using DNA damage response and chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBLs) for the prediction of acute toxicities of chemoradiotherapy (CRT) in esophageal cancer patients. Eighteen patients with esophageal cancer were enrolled in this prospective study. Prescribed doses were 60 Gy in 11 patients and 50 Gy in seven patients. Patients received 2 Gy radiotherapy five days a week. PBLs were obtained during treatment just before and 15 min after 2 Gy radiation therapy on the days when the cumulative dose reached 2, 20, 40 Gy and 50 or 60 Gy. PBLs were also obtained four weeks and six months after radiotherapy in all and 13 patients, respectively. Dicentric and ring chromosomes in PBLs were counted to evaluate the number of CAs. Gamma-H2AX foci per cell were scored to assess DNA double-strand breaks. We analyzed the association between these factors and adverse events. The number of γ-H2AX foci before radiotherapy showed no significant increase during CRT, while their increment was significantly reduced with the accumulation of radiation dose. The mean number of CAs increased during CRT up to 1.04 per metaphase, and gradually decreased to approximately 60% six months after CRT. Five patients showed grade 3 toxicities during or after CRT (overreactors: OR), while 13 had grade 2 or less toxicities (non-overreactors: NOR). The number of CAs was significantly higher in the OR group than in the NOR group at a cumulative dose of 20 Gy (mean value: 0.63 vs. 0.34, P = 0.02), 40 Gy (mean value: 0.90 vs. 0.52, P = 0.04), and the final day of radiotherapy (mean value: 1.49 vs. 0.84, P = 0.005). These findings suggest that number of CAs could be an index for predicting acute toxicities of CRT for esophageal cancer.

With the use of ionizing radiation comes the risk of accidents and malevolent misuse. When unplanned exposures occur, there are several methods which can be used to retrospectively reconstruct individual radiation exposures; biological methods include analysis of aberrations and damage of chromosomes and DNA, while physical methods rely on luminescence (TL/OSL) or EPR signals. To ensure the quality and dependability of these methods, they should be evaluated under realistic exposure conditions. In 2019, EURADOS Working Group 10 and RENEB organized a field test with the purpose of evaluating retrospective dosimetry methods as carried out in potential real-life exposure scenarios. A 1.36 TBq ¹⁹²Ir source was used to irradiate anthropomorphic phantoms in different geometries at doses of several Gy in an outdoor open-air geometry. Materials intended for accident dosimetry (including mobile phones and blood) were placed on the phantoms together with reference dosimeters (LiF, NaCl, glass). The objective was to estimate radiation exposures received by individuals as measured using blood and fortuitous materials, and to evaluate these methods by comparing the estimated doses to reference measurements and Monte Carlo simulations. Herein we describe the overall planning, goals, execution and preliminary outcomes of the 2019 field test. Such field tests are essential for the development of new and existing methods. The outputs from this field test include useful experience in terms of planning and execution of future exercises, with respect to time management, radiation protection, and reference dosimetry to be considered to obtain relevant data for analysis.

Tritium has been receiving worldwide attention, particularly because of its production and use in existing fission reactors and future nuclear fusion technologies, leading to an increased risk of release in the environment. Linking human health effects to low-dose tritium exposures presents a challenge for many reasons. Among these: biological effects strongly depend on the speciation of tritiated products and exposure pathway; large dosimetric uncertainties may exist; measurements using in vitro cell cultures generally lack a description of effects at the tissue level, while large-scale animal studies might be ethically questionable and too highly demanding in terms of resources. In this context, three-dimensional models of the human airway epithelium are a powerful tool to investigate potential toxicity induced upon inhalation of radioactive products in controlled physiological conditions. In this study we exposed such a model to tritiated water (HTO) for 24 h, with a range of activity levels (up to ∼33 kBq µl^–1 cm^–2). After the exposures, we measured cell viability, integrity of epithelial layer and pro-inflammatory response at different post-exposure time-points. We also quantified tritium absorption and performed dosimetric estimates considering HTO passage through the epithelial layer, leading to reconstructed upper limits for the dose to the tissue of less than 50 cGy cumulative dose for the highest activity. Upon exposure to the highest activity, cell viability was not decreased; however, we observed a small effect on epithelial integrity and an inflammatory response persisting after seven days. These results represent a reference condition and will guide future experiments using human airway epithelium to investigate the effects of other peculiar tritiated products.

Long non-coding RNAs are involved in the tumorigenesis of non-small cell lung cancer (NSCLC). Here we investigated whether LINC00476 affects the proliferation, invasion and migration of NSCLC cells via the SETDB1-activated Wnt/β-catenin pathway. The expression of LINC00476, SETDB1, Wnt1 and β-catenin were determined in NSCLC tumor tissues and the paired adjacent tissues, as well as in NSCLC cell lines and bronchial epithelioid cell lines. Cell proliferation, invasion and migration were determined using cell counting kit-8 assay and transwell assay. The relationship between LINC00476 and SETDB1 was elucidated using RNA pull-down, RNA immunoprecipitation and ubiquitination assays. LINC00476 was found to be significantly downregulated, while SETDB1, Wnt1 and β-catenin were upregulated in NSCLC tumor tissues and cell lines compared to the normal ones. Overexpression of LINC00476 promoted the proliferation, invasion and migration of NSCLC cells, and suppressed tumor growth in the mouse xenograft. Meanwhile, overexpression of LINC00476 induced the degradation of SETDB1 by promoting its ubiquitination. The simultaneous overexpression of LINC00476 and SETDB1 negated the inhibition of LINC00476 overexpression on the proliferation, invasion and migration of NSCLC cells. In conclusion, these findings indicate that LINC00476 acts as a tumor suppressor in NSCLC by downregulating SETDB1, which provides a novel target in the treatment of NSCLC.

Workers of the Commissariat for Atomic Energy and Alternative Energy (CEA) may be potentially exposed to tritium over long periods. We aimed to assess the effect of tritium exposure on mortality in a cohort of employees followed by radiotoxicological monitoring. A total of 1,746 employees who worked for at least six months at one of three CEA centers were included between 1962 and 2011 (median follow-up 29.6 years). The cumulative dose of tritium was based on the quantification of tritium present from urinary excretion monitoring data from the beginning of occupational exposure to the end of such exposure or December 2011. Mortality was first compared to that in the French population using the standardized mortality ratio (SMR). Then, mortality risk ratios (RRs) per category of cumulative dose of tritium were estimated using categorical Poisson models adjusted for age at the onset of exposure, age, calendar period, sex, smoking, employment status, CEA center, and taking into account the number of person-years. The main causes of mortality were tumors (48%) and cardiovascular diseases (20%). The comparison of mortality within the cohort to that in the French population highlighted a lower rate for all-cause mortality and that due to cancer, related to the healthy worker effect bias. The regression model showed no effect of cumulative dose on all-cause mortality. The risk of death for most malignancies was positive, but not significant for the higher classes of doses relative to the reference class. The highest risk (not significant) was present for the class of higher doses for tumors of the larynx, trachea, bronchi and lung. The risk was significant for the higher doses for tumors of the pancreas and bladder (based on a limited number of cases: five and six deaths, respectively). Significantly more smokers died from tumors of the respiratory system than non-smokers, as expected. We were unable to show an effect of cumulative tritium dose due to the small size of the cohort and the low exposure level. However, our study underlines the need to continue following tritium-exposed workers and conducting multicenter studies.

Numerous studies have strongly supported the application of gold nanoparticles (GNPs) as radio-enhanced agents. In our previous study, the local effect model (LEM I) was adopted to predict the cell survival for MDA-MB-231 cells exposed to 150 kVp X rays after 500 µg/ml GNPs treatment. However, microdosimetric quantities could not be obtained, which were correlated with biological effects on cells. Thus, we developed microdosimetric kinetic model (MKM) for GNP radio-enhancement (GNP-MKM), which uses the microdosimetric quantities such as dose-mean lineal energy with subcellular domain size. Using the Monte Carlo simulation tool Geant4, we estimated the dose-mean lineal energy with secondary radiations from GNPs and absorbed dose in the nucleus. The variations in MKM parameters for different domain sizes, and GNP concentrations, were calculated to compare the survival fractions predicted by both models. With a domain radius of 500 nm and a threshold dose of 20 Gy, the sensitizer enhancement ratio predicted by GNP-MKM and GNP-LEM was 1.41 and 1.29, respectively. The GNP-MKM predictions were much more strongly dependent on the domain size than were the GNP-LEM on the threshold dose. These findings provide another method to predict survival fraction for the GNP radio-enhancement.

Mouse models of radiation-induced thymic lymphoma are commonly used to study the biological effects of total-body irradiation (TBI) on the formation of hematologic malignancies. It is well documented that radiation-induced thymic lymphoma can be inhibited by protecting the bone marrow (BM) from irradiation; however, the mechanisms underlying this phenomenon are poorly understood. Here, we aimed to address this question by performing transplantation of BM cells from genetically engineered mice that have defects in tumor immunosurveillance or occupying different thymic niches. We found that BM cells from mice that have impaired tumor immunosurveillance, by deleting tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ) or perforin-1 (PRF1), remained sufficient to suppress the formation of radiation-induced thymic lymphoma. On the other hand, BM cells from Rag2^–/–; γc^–/– mice and Rag2^–/– mice, which have defects in occupying thymic niches beyond double negative (DN2) and DN3, respectively, failed to inhibit radiation-induced lymphomagenesis in the thymus. Taken together, based on our findings, we propose a model where unirradiated BM cells suppress radiation-induced lymphomagenesis in the thymus by competing with tumor-initiating cells for thymic niches beyond the DN3 stage.