Fatal hepatitis B reactivation in a patient receiving chemoradiation for cervical cancer.

INTRODUCTION: Hepatitis B virus (HBV) infection remains a global public health threat, with approximately 257 million people suffering from chronic HBV infection worldwide in 2015. HBV reactivation is a known complication of immunosuppressive therapy in people suffering with chronic HBV. Medications commonly associated with HBV reactivation include B-cell depleting agents and anthracycline derivatives. There have been very few documented cases of chemoradiation inducing HBV reactivation among scientific literature. CASE REPORT: A 44-year-old woman with chronic HBV infection and [FIGO] stage IIIB cervical cancer developed marked transaminitis and increased HBV viral load after receiving treatment with three doses of cisplatin and one dose of carboplatin with concurrent radiation for cervical cancer.Management and outcome: The patient was admitted for acute liver failure and quickly developed encephalopathy, with treatment complicated by coagulopathy, hypoglycemia, and metabolic acidosis. The patient remained unresponsive to maximal therapeutic efforts and was mechanically ventilated for airway protection. She subsequently died after experiencing ventricular tachycardia followed by asystole. DISCUSSION: There are currently no standardized guidelines for the screening of HBV infection or prophylaxis treatment algorithm for patients undergoing chemoradiation. When initiating treatment with immunosuppressive therapy, it is important to screen all patients for chronic HBV infection and to work with an interdisciplinary team of oncologists, hepatologists, and pharmacists to initiate prophylactic antiviral therapy and closely monitor to minimize the risk of HBV reactivation.

Low-Level Ionizing Radiation Induces Selective Killing of HIV-1-Infected Cells with Reversal of Cytokine Induction Using mTOR Inhibitors.

HIV-1 infects 39.5 million people worldwide, and cART is effective in preventing viral spread by reducing HIV-1 plasma viral loads to undetectable levels. However, viral reservoirs persist by mechanisms, including the inhibition of autophagy by HIV-1 proteins (i.e., Nef and Tat). HIV-1 reservoirs can be targeted by the "shock and kill" strategy, which utilizes latency-reversing agents (LRAs) to activate latent proviruses and immunotarget the virus-producing cells. Yet, limitations include reduced LRA permeability across anatomical barriers and immune hyper-activation. Ionizing radiation (IR) induces effective viral activation across anatomical barriers. Like other LRAs, IR may cause inflammation and modulate the secretion of extracellular vesicles (EVs). We and others have shown that cells may secrete cytokines and viral proteins in EVs and, therefore, LRAs may contribute to inflammatory EVs. In the present study, we mitigated the effects of IR-induced inflammatory EVs (i.e., TNF-α), through the use of mTOR inhibitors (mTORi; Rapamycin and INK128). Further, mTORi were found to enhance the selective killing of HIV-1-infected myeloid and T-cell reservoirs at the exclusion of uninfected cells, potentially via inhibition of viral transcription/translation and induction of autophagy. Collectively, the proposed regimen using cART, IR, and mTORi presents a novel approach allowing for the targeting of viral reservoirs, prevention of immune hyper-activation, and selectively killing latently infected HIV-1 cells.

Analysis of Hepatitis B Virus Reactivation After Radiotherapy in Patients With Hepatocellular Carcinoma Using the Lyman NTCP Model.

PURPOSE: To analyze the correlation of hepatitis B virus reactivation with patient-related and treatment-related dose-volume factors and to describe the feasibility of hepatitis B virus reactivation analyzed by a normal tissue complication probability model for patients with hepatocellular carcinoma treated with radiotherapy. MATERIALS AND METHODS: Ninety patients with hepatitis B virus-related hepatocellular carcinoma treated with radiotherapy were enrolled in this retrospective study and were followed from June 2009 to December 2015. Of the 90 patients, 78 had received conventional fractionation radiotherapy to a mean dose of 39.6 to 50.4 Gy and 12 patients were scheduled to receive hypofractionation. The physical doses were converted into 2 Gy equivalents for analysis. The parameters, TD50 (1), n, and m, of the Lyman-Kutcher-Burman normal tissue complication probability model were derived using maximum likelihood estimation. Bootstrap and leave-one-out were employed to against model overfitting and improve the model stability. RESULTS: Radiation-induced liver diseases were 17.8%, hepatitis B virus reactivation was 22.2%, and hepatitis B virus reactivation-induced hepatitis was 21.1%, respectively. In multivariate analysis, the V5Gy was associated with hepatitis B virus reactivation; TD50 (1), m, and n were 32.3, 0.55, and 0.71 Gy, respectively, for hepatitis B virus reactivation. Bootstrap and leave-one-out results showed that the hepatitis B virus parameter fits were extremely robust. CONCLUSION: A Lyman-Kutcher-Burman normal tissue complication probability model has been established to predict hepatitis B virus reactivation for patients with hepatocellular carcinoma who received radiotherapy.

A case of herpes simplex virus reactivation after fractional ablative carbon dioxide laser to treat a burn scar.

Fractional photothermolysis was initially introduced by Manstein in 2004 .Fractional CO2 laser technology introduced has allowed physicians to obtain good cosmetic results with a lower rate of complications than non-fractionated ablative laser treatment. However, adverse effects may still occur.Reported cases of HSV infection after fractional photothermolysis are rare. A 48-year-old woman with Fitzpatrick skin type III presented with a scar in her perioral area desiring esthetic improvement of her burn scar. She didn't have a history of recurrent herpes simplex virus (HSV) infection periorally. A fractionated resurfacing laser Quadralase (Candela) was used to treat her perioral burn scar. Two sessions were performed with a month interval. Five days after the second session of laser therapy even after she took antiviral prophylaxis based on valacyclovir 500mg twice daily 24 hours before the laser session and 3 days after, she presented with a rash on the perioral area preceded by pain. Correlation of the history and the clinical presentation was consistent with HSV reactivation. Treatment was initiated with acyclovir 10mg/kg/8h administered intravenously for 10 days with a clearing of her vesicular eruption. Fractional CO2 laser is a very safe procedure when used with accepted parameters. Early recognition, close monitoring and careful wound care will prevent long term sequelae when complications occur.

Reactivation of Latent Epstein-Barr Virus: A Comparison after Exposure to Gamma, Proton, Carbon, and Iron Radiation.

Among the many stressors astronauts are exposed to during spaceflight, cosmic radiation may lead to various serious health effects. Specifically, space radiation may contribute to decreased immunity, which has been documented in astronauts during short- and long-duration missions, as evidenced by several changes in cellular immunity and plasma cytokine levels. Reactivation of latent herpes viruses, either directly from radiation of latently infected cells and/or from perturbation of the immune system, may result in disease in astronauts. Epstein‒Barr virus (EBV) is one of the eight human herpes viruses known to infect more than 90% of human adults and persists for the life of the host without normally causing adverse effects. Reactivation of several latent viruses in astronauts is well documented, although the mechanism of reactivation is not well understood. We studied the effect of four different types of radiation, (1) 137Cs gamma rays, (2) 150-MeV protons, (3) 600 MeV/n carbon ions, and (4) 600 MeV/n iron ions on the activation of lytic gene transcription and of reactivation of EBV in a latently infected cell line (Akata) at doses of 0.1, 0.5, 1.0, and 2.0 Gy. The data showed that for all doses used in this study, lytic gene transcription was induced and median viral loads were significantly higher for all types of radiation than in corresponding control samples, with the increases detected as early as four days post-exposure and generally tapering off at later time points. The viability and size of EBV-infected Akata cells were highly variable and exhibited approximately the same trend in time for all radiation types at 0.1, 0.5, 1.0, and 2.0 Gy. This work shows that reactivation of viruses can occur due to the effect of different types of radiation on latently infected cells in the absence of changes or cytokines produced in the immune system. In general, gamma rays are more effective than protons, carbon ions, and iron ions in inducing latent virus reactivation, though these high-energy particles did induce more sustained and later reactivation of EBV lytic gene transcription. These findings also challenge the common relative biological effectiveness concept that is often used in radiobiology for other end points.

Hepatitis B virus reactivation after radiotherapy for hepatocellular carcinoma and efficacy of antiviral treatment: A multicenter study.

Convincing data that support routine use of preventive therapy against hepatitis B virus (HBV) reactivation in radiotherapy (RT) for hepatocellular carcinoma (HCC) are lacking. The aim of this study was to investigate the incidence, clinical significance, and risk factors of HBV reactivation after RT. Medical records of 133 HBsAg (+) HCC patients who received radiotherapy from March 2009 to February 2016 were reviewed. Patients were divided into two groups: 1) non-antiviral group, those who did not receive antiviral therapy before RT (n = 27); and antiviral group (those who underwent antiviral therapy before RT) (n = 106). Factors related to HBV reactivation in HCC patients were evaluated. 17 (12.7%) of 133 patients developed HBV reactivation after RT. Patients in the antiviral group had significantly lower rates of HBV reactivation than those in the non-antiviral group (7.5% vs. 33.3%, p<0.001). HBV related hepatitis was also lower in the antiviral group (3.8% vs. 14.8%, p = 0.031). In multivariate analysis, absence of antiviral treatment (OR: 8.339, 95% CI: 2.532-27.470, p<0.001) and combined treatment of RT with transarterial chemoembolizatoin (TACE) (OR: 5.313, 95% CI: 1.548-18.232, p = 0.008) were risk factors for HBV reactivation. HBV reactivation can occur after radiotherapy. Combination treatment of RT with TACE and non-antiviral treatment are major risk factors for HBV reactivation during or after RT. Therefore, preventive antiviral therapy should be recommended for patients with HCC who are scheduled to receive RT.

Extermination of influenza virus H1N1 by a new visible-light-induced photocatalyst under fluorescent light.

A new visible-light-induced photocatalyst based on several transition metals (iron, magnesium and manganese)-loaded TiO2 was evaluated for its anti-viral activity with influenza virus H1N1. Under a fluorescent lamp of 1000 lx, λ > 410 nm, the virus was eradicated to more than 99% within 30 min. Since this photocatalyst can be used for coating plastics, wall papers and walls, it would be desirable to use this photocatalyst to reduce viral transmission via droplets and aerosols as well as surface contact for disinfection.

Lack of TNF-α signaling through p55 makes the mice more susceptible to acute infection but does not alter state of latency and reactivation of HSV-1.

TNF-α has been shown to play an important role in pathogenesis and latency of HSV-1 infections. TNF-α signals through TNFR1 (p55) and TNFR2 (p75), and signaling through p55 generally results in gene activation leading to induction of inflammatory responses. Here, we studied the role of TNF-α signaling in latent virus reactivation in p55-knock out (KO) mouse model of ocular HSV-1 infection. We found that KO mice are more susceptible to HSV-1 infection compared to wild type C57Bl/6 mice. While the absence of TNFRI signaling enhanced the ganglion latent DNA content by two folds, there was no difference in the maintenance and reactivation of latent HSV-1. Strikingly, interfering with inflammatory responses through PGE2 synthesis by treating latently infected wild type mice with indomethacin (COX inhibitor) prior to UV-exposure prevented HSV-1 reactivation. These results suggest that reactivation of latent HSV-1 might result from the cumulative effects of a cascade of inflammatory cytokines including TNF-α.

The role of oxidative stress in EBV lytic reactivation, radioresistance and the potential preventive and therapeutic implications.

Epstein-Barr virus (EBV) is an important cancer causing virus. Cancer associated with EBV account for approximately 1.5% of all cancers, and represent 1.8% of all cancer deaths worldwide. EBV reactivation plays an important role in the development of EBV-related diseases and is closely related with patients' survival and clinical stages of EBV-related cancers. The therapy regarding to EBV-related cancers is very urgent, especially in endemic areas. Generating oxidative stress is a critical mechanism by which host cells defend against infection by virus. In addition, ROS-mediated oxidative stress plays a significant but paradoxical role acting as a "double-edged sword" to regulate cellular response to radiation, which is the main therapy strategy for EBV-related cancers, especially nasopharyngeal carcinoma. Therefore, in this review we primarily discuss the possible interplay among the oxidative stress, EBV lytic reactivation and radioresistance. Understanding the role of oxidative stress in EBV lytic reactivation and radioresistance will assist in the development of effective strategies for prevention and treatment of EBV-related cancers.

Enhancing effect of 50 Hz rotating magnetic field on induction of Shiga toxin-converting lambdoid prophages.

Studies aimed at investigating factors and mechanism of induction of prophages, a major pathogenesis factor of Shiga toxin-producing Escherichia coli (STEC), are considered important to develop an effective treatment for STEC infections. In this study, we demonstrated the synergistic effect of the rotating magnetic field (RMF) of induction B = 34 mT and frequency ƒ = 50 Hz at a constant temperature of 37 °C and mitomycin C (MMC), that resulted in a higher level of induction of stx-carrying lambdoid Stx prophages. This is a first report on the induction of lambdoid Stx prophages in response to the enhancing effect of popular inductor (mitomycin C) under the influence of RMF.

Characterization of Functional Prophages in Clostridium difficile.

Bacteriophages (phages) are present in almost, if not all ecosystems. Some of these bacterial viruses are present as latent "prophages," either integrated within the chromosome of their host, or as episomal DNAs. Since prophages are ubiquitous throughout the bacterial world, there has been a sustained interest in trying to understand their contribution to the biology of their host. Clostridium difficile is no exception to that rule and with the recent release of hundreds of bacterial genome sequences, there has been a growing interest in trying to identify and classify these prophages. Besides their identification in bacterial genomes, there is also growing interest in determining the functionality of C. difficile prophages, i.e., their capacity to escape their host and reinfect a different strain, thereby promoting genomic evolution and horizontal transfer of genes through transduction, for example of antibiotic resistance genes. There is also some interest in using therapeutic phages to fight C. difficile infections.The objective of this chapter is to share with the broader C. difficile research community the expertise we developed in the study of C. difficile temperate phages. In this chapter, we describe a general "pipeline" comprising a series of experiments that we use in our lab to identify, induce, isolate, propagate, and characterize prophages. Our aim is to provide readers with the necessary basic tools to start studying C. difficile phages.

The Role of the Exo-Xis Region in Oxidative Stress-Mediated Induction of Shiga Toxin-Converting Prophages.

Previous studies indicated that these genetic elements could be involved in the regulation of lysogenization and prophage induction processes. The effects were dramatic in Shiga toxin-converting phage Φ24(B) after treatment with oxidative stress-inducing agent, hydrogen peroxide, while they were less pronounced in bacteriophage λ and in both phages irradiated with UV. The hydrogen peroxide-caused prophage induction was found to be RecA-dependent. Importantly, in hydrogen peroxide-treated E. coli cells lysogenic for either λ or Φ24(B), deletion of the exo-xis region resulted in a significant decrease in the levels of expression of the S.O.S. regulon genes. Moreover, under these conditions, a dramatic decrease in the levels of expression of phage genes crucial for lytic development (particularly xis, exo, N, cro, O, Q, and R) could be observed in Φ24(B)-, but not in λ-bearing cells. We conclude that genes located in the exo-xis region are necessary for efficient expression of both host S.O.S regulon in lysogenic bacteria and regulatory genes of Shiga toxin-converting bacteriophage Φ24(B).

Potential of Radiation-Induced Cellular Stress for Reactivation of Latent HIV-1 and Killing of Infected Cells.

The use of highly active antiretroviral therapy against HIV-1 for last two decades has reduced mortality of patients through extension of nonsymptomatic phase of infection. However, HIV-1 can be preserved in long-lived resting CD4(+) T cells, which form a viral reservoir in infected individuals, and potentially in macrophages and astrocytes. Reactivation of viral replication is critical since the host immune response in combination with antiretroviral therapy may eradicate the virus (shock and kill strategy). In this opinion piece, we consider potential application of therapeutic doses of irradiation, the well-known and effective stress signal that induces DNA damage and activates cellular stress response, to resolve two problems: activate HIV-1 replication and virion production in persistent reservoirs under cART and deplete infected cells through selective cell killing using DNA damage responses.

Prior Corneal Scarification and Injection of Immune Serum are Not Required Before Ocular HSV-1 Infection for UV-B-Induced Virus Reactivation and Recurrent Herpetic Corneal Disease in Latently Infected Mice.

PURPOSE: Blinding ocular herpetic disease in humans is due to spontaneous reactivation of herpes simplex virus type 1 (HSV-1) from latency, rather than to primary acute infection. Mice latently infected with HSV-1 undergo little or no in vivo spontaneous reactivation with accompanying virus shedding in tears. HSV-1 reactivation can be induced in latently infected mice by several in vivo procedures, with UV-B-induced reactivation being one commonly used method. In the UV-B model, corneas are scarified (lightly scratched) just prior to ocular infection to increase efficiency of the primary infection and immune serum containing HSV-1 neutralizing antibodies is injected intraperitoneally (i.p.) to increase survival and decrease acute corneal damage. Since scarification can significantly alter host gene transcription in the cornea and in the trigeminal ganglia (TG; the site of HSV-1 latency) and since injection of immune serum likely modulates innate and adaptive herpes immunity, we investigated eliminating both treatments. MATERIAL AND METHODS: Mice were infected with HSV-1 with or without corneal scarification and immune serum. HSV-1 reactivation and recurrent disease were induced by UV-B irradiation. RESULTS: When corneal scarification and immune serum were both eliminated, UV-B irradiation still induced both HSV-1 reactivation, as measured by shedding of reactivated virus in tears and herpetic eye disease, albeit at reduced levels compared to the original procedure. CONCLUSION: Despite the reduced reactivation and disease, avoidance of both corneal scarification and immune serum should improve the clinical relevance of the UV-B mouse model.

Impaired Fas-Fas Ligand Interactions Result in Greater Recurrent Herpetic Stromal Keratitis in Mice.

Herpes simplex virus-1 (HSV-1) infection of the cornea leads to a potentially blinding condition termed herpetic stromal keratitis (HSK). Clinical studies have indicated that disease is primarily associated with recurrent HSK following reactivation of a latent viral infection of the trigeminal ganglia. One of the key factors that limit inflammation of the cornea is the expression of Fas ligand (FasL). We demonstrate that infection of the cornea with HSV-1 results in increased functional expression of FasL and that mice expressing mutations in Fas (lpr) and FasL (gld) display increased recurrent HSK following reactivation compared to wild-type mice. Furthermore, both gld and lpr mice took longer to clear their corneas of infectious virus and the reactivation rate for these strains was significantly greater than that seen with wild-type mice. Collectively, these findings indicate that the interaction of Fas with FasL in the cornea restricts the development of recurrent HSK.

Therapeutic doses of irradiation activate viral transcription and induce apoptosis in HIV-1 infected cells.

The highly active antiretroviral therapy reduces HIV-1 RNA in plasma to undetectable levels. However, the virus continues to persist in the long-lived resting CD4(+) T cells, macrophages and astrocytes which form a viral reservoir in infected individuals. Reactivation of viral transcription is critical since the host immune response in combination with antiretroviral therapy may eradicate the virus. Using the chronically HIV-1 infected T lymphoblastoid and monocytic cell lines, primary quiescent CD4(+) T cells and humanized mice infected with dual-tropic HIV-1 89.6, we examined the effect of various X-ray irradiation (IR) doses (used for HIV-related lymphoma treatment and lower doses) on HIV-1 transcription and viability of infected cells. Treatment of both T cells and monocytes with IR, a well-defined stress signal, led to increase of HIV-1 transcription, as evidenced by the presence of RNA polymerase II and reduction of HDAC1 and methyl transferase SUV39H1 on the HIV-1 promoter. This correlated with the increased GFP signal and elevated level of intracellular HIV-1 RNA in the IR-treated quiescent CD4(+) T cells infected with GFP-encoding HIV-1. Exposition of latently HIV-1infected monocytes treated with PKC agonist bryostatin 1 to IR enhanced transcription activation effect of this latency-reversing agent. Increased HIV-1 replication after IR correlated with higher cell death: the level of phosphorylated Ser46 in p53, responsible for apoptosis induction, was markedly higher in the HIV-1 infected cells following IR treatment. Exposure of HIV-1 infected humanized mice with undetectable viral RNA level to IR resulted in a significant increase of HIV-1 RNA in plasma, lung and brain tissues. Collectively, these data point to the use of low to moderate dose of IR alone or in combination with HIV-1 transcription activators as a potential application for the "Shock and Kill" strategy for latently HIV-1 infected cells.

Impact of irradiation and immunosuppressive agents on immune system homeostasis in rhesus macaques.

In this study we examined the effects of non-myeloablative total body irradiation (TBI) in combination with immunosuppressive chemotherapy on immune homeostasis in rhesus macaques. Our results show that the administration of cyclosporin A or tacrolimus without radiotherapy did not result in lymphopenia. The addition of TBI to the regimen resulted in lymphopenia as well as alterations in the memory/naive ratio following reconstitution of lymphocyte populations. Dendritic cell (DC) numbers in whole blood were largely unaffected, while the monocyte population was altered by immunosuppressive treatment. Irradiation also resulted in increased levels of circulating cytokines and chemokines that correlated with T cell proliferative bursts and with the shift towards memory T cells. We also report that anti-thymocyte globulin (ATG) treatment and CD3 immunotoxin administration resulted in a selective and rapid depletion of naive CD4 and CD8 T cells and increased frequency of memory T cells. We also examined the impact of these treatments on reactivation of latent simian varicella virus (SVV) infection as a model of varicella zoster virus (VZV) infection of humans. None of the treatments resulted in overt SVV reactivation; however, select animals had transient increases in SVV-specific T cell responses following immunosuppression, suggestive of subclinical reactivation. Overall, we provide detailed observations into immune modulation by TBI and chemotherapeutic agents in rhesus macaques, an important research model of human disease.

Risk factors for hepatitis B virus reactivation after conformal radiotherapy in patients with hepatocellular carcinoma.

This study investigated whether conformal radiotherapy affects hepatitis B virus (HBV) reactivation, and the risk factors for HBV reactivation in patients with HBV-related hepatocellular carcinoma (HCC). Sixty-nine patients with HCC were included in this retrospective study. Before radiotherapy (RT), all patients underwent imaging examinations and some baseline examinations, including CBC, liver function test, renal function test, α-fetoprotein level, hepatitis B (HB) surface antigen, HB surface Ab, HB e antigen, HB e Ab, and serum HBV DNA quantification. During the period of RT and at least 16 weeks after the end of RT, CBCs were carried out weekly and the other tests were monitored monthly or more frequently if necessary. The clinical features and dosimetric parameters of RT were recorded. Univariate and multivariate logistic regression algorithms were used to analyze the risk factors of HBV reactivation. The incidence of complications in the study population was as follows: radiation-induced liver disease, 17.4%; HBV reactivation, 24.6%; and HBV reactivation-induced hepatitis, 21.7%. The HBV DNA level and dose volume parameters including normal liver volume, V20, and mean dose were associated with HBV reactivation. There was a relatively high incidence of HBV reactivation in HCC patients after the end of conformal RT. The serum HBV DNA level and some dosimetric parameters related to normal liver, including normal liver volume, V20, and mean dose, were the prognosis factors of HBV reactivation and should be carefully considered before conformal RT.

TLR4-dependant immune response, but not hepatitis B virus reactivation, is important in radiation-induced liver disease of liver cancer radiotherapy.

Toll-like receptor 4 (TLR4) is an important trigger of the immune response against hepatitis B virus (HBV) infection and liver injuries. The roles of HBV reactivation versus TLR4-dependant immune response may be critical factors in preventing radiation-induced liver diseases (RILDs) after liver cancer radiotherapy. This study consists of three phases. In the primary phase, livers of mutant TLR4 (TLR4(-)) mice were irradiated with 30 Gy in either the absence or presence of HBV infection. The latter was done by introduction of plasmid pAAV/HBV 1.2. In the advanced phase, RILDs were compared in normal TLR4 (TLR4(+)) versus TLR4(-) mice. In the validation phase, 28 liver cancer patients who had undergone radiotherapy before hepatectomy were enrolled. Liver biopsies near tumors, irradiated with 35-48 Gy, were used to construct tissue microarrays. HBV reactivation, TLR4 expression, and severity of RILDs were studied in both mouse and human. More HBV reactivation, without significant RILD, was observed in irradiated versus unirradiated TLR4(-) mice. RILD scores of TLR4(+) mice were higher than TLR4(-) mice. In humans, serious RILDs tended to develop in patients with high TLR4 expression, but not in patients with low TLR4 or high HBV surface antigen expression. High TLR4 expression was seen in only 2 of 12 HBV-reactive patients, but in HBV-nonreactive patients, it was seen in 6 of 9 (P < 0.03). In summary, RILDs correlated with high TLR4 expression, but not with HBV reactivation, which is inhibited in liver with high TLR4 expression after liver cancer radiotherapy.

Characterization of Epstein-Barr virus reactivation in a modeled spaceflight system.

Epstein-Barr virus (EBV) is the causative agent of mononucleosis and is also associated with several malignancies, including Burkitt's lymphoma, Hodgkin's lymphoma, and nasopharyngeal carcinoma, among others. EBV reactivates during spaceflight, with EBV shedding in saliva increasing to levels ten times those observed pre-and post-flight. Although stress has been shown to increase reactivation of EBV, other factors such as radiation and microgravity have been hypothesized to contribute to reactivation in space. We used a modeled spaceflight environment to evaluate the influence of radiation and microgravity on EBV reactivation. BJAB (EBV-negative) and Raji (EBV-positive) cell lines were assessed for viability/apoptosis, viral antigen and reactive oxygen species expression, and DNA damage and repair. EBV-infected cells did not experience decreased viability and increased apoptosis due to modeled spaceflight, whereas an EBV-negative cell line did, suggesting that EBV infection provided protection against apoptosis and cell death. Radiation was the major contributor to EBV ZEBRA upregulation. Combining modeled microgravity and radiation increased DNA damage and reactive oxygen species while modeled microgravity alone decreased DNA repair in Raji cells. Additionally, EBV-infected cells had increased DNA damage compared to EBV-negative cells. Since EBV-infected cells do not undergo apoptosis as readily as uninfected cells, it is possible that virus-infected cells in EBV seropositive individuals may have an increased risk to accumulate DNA damage during spaceflight. More studies are warranted to investigate this possibility.