Current Status and Perspectives of Therapeutic Antibodies Targeting the Spike Protein S2 Subunit against SARS-CoV-2.

The global coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has devastated public health and the global economy. New variants are continually emerging because of amino acid mutations within the SARS-CoV-2 spike protein. Existing neutralizing antibodies (nAbs) that target the receptor-binding domain (RBD) within the spike protein have been shown to have reduced neutralizing activity against these variants. In particular, the recently expanding omicron subvariants BQ 1.1 and XBB are resistant to nAbs approved for emergency use by the United States Food and Drug Administration. Therefore, it is essential to develop broad nAbs to combat emerging variants. In contrast to the massive accumulation of mutations within the RBD, the S2 subunit remains highly conserved among variants. Therefore, nAbs targeting the S2 region may provide effective cross-protection against novel SARS-CoV-2 variants. Here, we provide a detailed summary of nAbs targeting the S2 subunit: the fusion peptide, stem helix, and heptad repeats 1 and 2. In addition, we provide prospects to solve problems such as the weak neutralizing potency of nAbs targeting the S2 subunit.

Kaposi's sarcoma-associated herpesvirus replication and transcription activator protein activates CD274/PD-L1 gene promoter.

Kaposi's sarcoma-associated herpesvirus (KSHV) is responsible for the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. The expression of immunosuppressive genes, such as IL-10 and CD274/PD-L1 is observed during KSHV-associated pathogenesis, and the modulation of the host immune system by KSHV contributes to establishing viral persistence in the host. Understanding the mechanism that allows the virus to evade host cell immunity would be helpful in order to develop therapeutic strategies for KSHV malignancy. In this study, we show that KSHV replication and transcriptional activator (K-RTA), an essential activator of the viral lytic cycle, transactivates the CD274/PD-L1 gene promoter. Mechanistically, we demonstrate that the binding of K-RTA to the cellular specificity protein 1 (SP1) is critical for K-RTA-mediated CD274/PD-L1 promoter activation. These findings suggest that K-RTA cooperates with intracellular SP1 to activate the expression of CD274/PD-L1, which helps the virus regulate immune checkpoints to escape and survive.

The function of SARS-CoV-2 spike protein is impaired by disulfide-bond disruption with mutation at cysteine-488 and by thiol-reactive N-acetyl-cysteine and glutathione.

Viral spike proteins play important roles in the viral entry process, facilitating attachment to cellular receptors and fusion of the viral envelope with the cell membrane. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein binds to the cellular receptor angiotensin converting enzyme-2 (ACE2) via its receptor-binding domain (RBD). The cysteine residue at position 488, consisting of a disulfide bridge with cysteine 480 is located in an important structural loop at ACE2-binding surface of RBD, and is highly conserved among SARS-related coronaviruses. We showed that the substitution of Cys-488 with alanine impaired pseudotyped SARS-CoV-2 infection, syncytium formation, and cell-cell fusion triggered by SARS-CoV-2 spike expression. Consistently, in vitro binding of RBD and ACE2, spike-mediated cell-cell fusion, and pseudotyped viral infection of VeroE6/TMPRSS2 cells were inhibited by the thiol-reactive compounds N-acetylcysteine (NAC) and a reduced form of glutathione (GSH). Furthermore, we demonstrated that the activity of variant spikes from the SARS-CoV-2 alpha and delta strains were also suppressed by NAC and GSH. Taken together, these data indicate that Cys-488 in spike RBD is required for SARS-CoV-2 spike functions and infectivity, and could be a target of anti-SARS-CoV-2 therapeutics.

Anti-HBV drug entecavir ameliorates DSS-induced colitis through PD-L1 induction.

PD-L1-mediated signaling is one of the major processes that regulate local inflammatory responses in the gut. To date, protective effects against colitis through direct Fc-fused PD-L1 administration or indirect PD-L1 induction by probiotics have been reported. We have previously shown that the anti-HBV drug entecavir (ETV) induces PD-L1 expression in human hepatocytes. In the present study, we investigated whether ETV induces PD-L1 expression in intestinal cells and provides a protective effect against DSS-induced colitis. ETV induced PD-L1 expression in epithelial cells, rather than T and B cells, improving the symptoms of colitis. In the mechanistic analysis, Th17 cell differentiation was inhibited and B cell infiltration into the lamina propria was reduced. In addition, PD-L1 expression was positively correlated with Foxp3 or CSF1-R. In conclusion, ETV upregulated PD-L1 expression in epithelial cells and ameliorated inflammation in DSS-induced colitis. These results suggest that ETV may be a potential therapeutic agent as a PD-L1 enhancer for the treatment of human IBD.

SARS-CoV-2 Spike Protein Mutation at Cysteine-488 Impairs Its Golgi Localization and Intracellular S1/S2 Processing.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein binds to the cellular receptor-angiotensin-converting enzyme-2 (ACE2) as the first step in viral cell entry. SARS-CoV-2 spike protein expression in the ACE2-expressing cell surface induces cell-cell membrane fusion, thus forming syncytia. To exert its fusogenic activity, the spike protein is typically processed at a specific site (the S1/S2 site) by cellular proteases such as furin. The C488 residue, located at the spike-ACE2 interacting surface, is critical for the fusogenic and infectious roles of the SARS-CoV-2 spike protein. We have demonstrated that the C488 residue of the spike protein is involved in subcellular targeting and S1/S2 processing. C488 mutant spike localization to the Golgi apparatus and cell surface were impaired. Consequently, the S1/S2 processing of the spike protein, probed by anti-Ser-686-cleaved spike antibody, markedly decreased in C488 mutant spike proteins. Moreover, brefeldin-A-mediated endoplasmic-reticulum-to-Golgi traffic suppression also suppressed spike protein S1/S2 processing. As brefeldin A treatment and C488 mutation inhibited S1/S2 processing and syncytia formation, the C488 residue of spike protein is required for functional spike protein processing.

Direct Inhibition of SARS-CoV-2 Spike Protein by Peracetic Acid.

Peracetic acid (PAA) disinfectants are effective against a wide range of pathogenic microorganisms, including bacteria, fungi, and viruses. Several studies have shown the efficacy of PAA against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, its efficacy in SARS-CoV-2 variants and the molecular mechanism of action of PAA against SARS-CoV-2 have not been investigated. SARS-CoV-2 infection depends on the recognition and binding of the cell receptor angiotensin-converting enzyme 2 (ACE2) via the receptor-binding domain (RBD) of the spike protein. Here, we demonstrated that PAA effectively suppressed pseudotyped virus infection in the Wuhan type and variants, including Delta and Omicron. Similarly, PAA reduced the authentic viral load of SARS-CoV-2. Computational analysis suggested that the hydroxyl radicals produced by PAA cleave the disulfide bridges in the RBD. Additionally, the PAA treatment decreased the abundance of the Wuhan- and variant-type spike proteins. Enzyme-linked immunosorbent assay showed direct inhibition of RBD-ACE2 interactions by PAA. In conclusion, the PAA treatment suppressed SARS-CoV-2 infection, which was dependent on the inhibition of the interaction between the spike RBD and ACE2 by inducing spike protein destabilization. Our findings provide evidence of a potent disinfection strategy against SARS-CoV-2.

Extracellular vesicles secreted by HBV-infected cells modulate HBV persistence in hydrodynamic HBV transfection mouse model.

Hepatitis B, a viral infection that affects the liver, is thought to affect over 257 million people worldwide, and long-term infection can lead to life-threatening issues such as cirrhosis or liver cancer. Chronic hepatitis B develops by the interaction between hepatitis B virus (HBV) and host immune response. However, questions of how HBV-infected cells thwart immune system defenses remain unanswered. Extracellular vesicles (EVs) are used for cellular communication, carrying cargoes such as RNAs, proteins, and lipids and delivering them intracellularly after being endocytosed by target cells. HBV-infected liver cells secrete several types of EVs into body fluids such as complete and incomplete virions, and exosomes. We previously demonstrated that monocytes that incorporated EVs moved to immunoregulatory phenotypes via up-regulation of PD-L1, an immunocheckpoint molecule, and down-regulation of CD69, a leukocyte activation molecule. In this study, we transfected mice with HBV using hydrodynamic injection and studied the effects of EVs secreted by HBV-infected liver cells. EVs secreted from cells with HBV replication strongly suppressed the immune response, inhibiting the eradication of HBV-replicating cells in the mice transfected with HBV. EVs were systemically incorporated in multiple organs, including liver, bone marrow (BM), and intestine. Intriguingly, the BM cells that incorporated EVs acquired intestinal tropism and the dendritic cell populations in the intestine increased. These findings suggest that the EVs secreted by HBV-infected liver cells exert immunosuppressive functions, and that an association between the liver, bone marrow, and intestinal tract exists through EVs secreted from HBV-infected cells.

PD-L1 is induced on the hepatocyte surface via CKLF-like MARVEL transmembrane domain-containing protein 6 up-regulation by the anti-HBV drug Entecavir.

Chronic hepatitis B is now controllable when treated with nucleoside reverse transcriptase inhibitors (NRTIs), which inhibit hepatitis B virus (HBV) replication. However, once the NRTIs are discontinued, most patients relapse, necessitating lifelong NRTIs treatment. HBV infection relapse is assumed to be caused by the persistent existence of covalently closed circular DNA (cccDNA) in the nuclei of infected hepatocytes. The mechanism by which cccDNA-positive hepatocytes escape immune surveillance during NRTIs treatment remains elusive. Entecavir (ETV), a commonly used NRTI, post-transcriptionally up-regulates programmed cell death-ligand 1 (PD-L1), an immune checkpoint molecule, on the cell surface of hepatocytes regardless of HBV infection. Up-regulation by ETV depends on up-regulation of CKLF-like MARVEL transmembrane domain-containing 6, a newly identified potent regulator of PD-L1 expression on the cell surface. ETV-treated hepatic cells suppressed the activity of primary CD3 T cells and programmed cell death protein-1 (PD-1)-over-expressed Jurkat cells. Finally, ETV induces PD-L1 in primary hepatocytes infected by HBV. These results provide evidence that ETV considerably up-regulates PD-L1 on the cell surface of infected hepatocytes, which may be one of the mechanisms by which infected hepatocytes subvert immune surveillance.

Effects of tolvaptan in patients with chronic kidney disease and chronic heart failure.

BACKGROUND: Tolvaptan, a vasopressin V2 receptor blocker, has a diuretic effect for patients with heart failure. However, there were a few data concerning the effects of tolvaptan in patients with chronic kidney disease (CKD). METHODS: We retrospectively analyzed 21 patients with chronic heart failure and CKD. Tolvaptan was co-administered with other diuretics in-use, every day. We compared clinical parameters before and after the treatments with tolvaptan. Furthermore, we examined the correlations between baseline data and the change of body weight. RESULTS: Tolvaptan decreased the body weight and increased the urine volume (p = 0.001). The urine osmolality significantly decreased throughout the study period. Urinary Na/Cr ratio and FENa changed significantly after 4 h, and more remarkable after 8 h (p = 0.003, both). Serum creatinine increased slightly after 1 week of treatment (p = 0.012). The alteration of body weight within the study period correlated negatively with the baseline urine osmolality (r = -0.479, p = 0.038), the baseline urine volume (r = -0.48, p = 0.028), and the baseline inferior vena cava diameter (IVCD) (r = -0.622, p = 0.017). Hyponatremia was improved to the normal value, and the augmentations of the sodium concentration were negatively associated with the basal sodium levels (p = 0.01, r = -0.546). CONCLUSIONS: Tolvaptan is effective in increasing diuresis and improved hyponatremia, even in patients with CKD. The baseline urine osmolality, urine volume, and IVCD may be useful predictors for diuretic effects of tolvaptan.

Efficacy of cyclosporine combination therapy for new-onset minimal change nephrotic syndrome in adults.

BACKGROUND: Cyclosporine and prednisolone combination therapy has been used in the treatment of minimal change nephrotic syndrome (MCNS). However, few studies have evaluated the efficacy of cyclosporine combined with intravenous methylprednisolone pulse therapy (MPT) as a first-line treatment for new-onset MCNS. We conducted a retrospective clinical study to evaluate the efficacy and safety of cyclosporine combined with MPT and oral prednisolone for new-onset MCNS in adults. METHODS: Forty-six adult patients with biopsy-proven MCNS were analyzed retrospectively. This study included three groups. Group 1 (n = 17) was treated with intravenous MPT (0.5 or 1.0 g/day for 3 days) followed by oral cyclosporine (2-3 mg/kg/day) and prednisolone (30 mg/day). Group 2 (n = 15) was treated with intravenous MPT followed by oral prednisolone (0.4-0.8 mg/kg/day). Group 3 (n = 14) was treated with oral prednisolone (0.6-1.0 mg/kg/day) alone. RESULTS: The length of hospital stay was the shortest in Group 1 (P < 0.001). The mean duration to achieve <20 mg/day of prednisolone was also the shortest in Group 1 (P < 0.05). Complete remission rates were 100 % in Group 1, 85.7 % in Group 2, and 69.2 % in Group 3 during the 9-month follow-up (P = 0.073). The rate of adverse effects caused by prednisolone was less in Group 1 (P < 0.05). Multivariate analysis revealed that the independent determinants of durations of remission were the selectivity index (P = 0.004), eGFR (P = 0.001) and the use of cyclosporine (P = 0.045). CONCLUSIONS: Combination therapy with cyclosporine may be a beneficial treatment option for new-onset MCNS in adults because of its clinical efficacy and safety.

[Development of a batched image delete system for multi-vender picture archiving and communication system environment].

A picture archiving and communication system (PACS) for multi-vendor imaging servers is useful, since it can provide a variety of image-processing services. However, to delete an image file in the PACS, it is necessary to delete not only the image but all its associated images that are stored in multiple servers: this is a lengthy and painstaking process. To reduce this workload, we have developed a system consisting of a computer program with a graphical user interface that can delete the target image and all related images by means of batch processing. The developed system creates an extensible markup language (XML)-format file that describes the operation for deleting an image and forwards the XML file to the main server. Using a Windows file-sharing system (SMB/CIFS), each server shares the XML file and deletes the images in its own database in response to the instructions described in the XML file. We can also rigorously manage information concerning the deleted images using the information that is output from the main server to external storage. We also discuss the degree of load reduction in our system compared with that of ordinary systems.

Overcoming antibody-resistant SARS-CoV-2 variants with bispecific antibodies constructed using non-neutralizing antibodies.

A current challenge is the emergence of SARS-CoV-2 variants, such as BQ.1.1 and XBB.1.5, that can evade immune defenses, thereby limiting antibody drug effectiveness. Emergency-use antibody drugs, including the widely effective bebtelovimab, are losing their benefits. One potential approach to address this issue are bispecific antibodies which combine the targeting abilities of two antibodies with distinct epitopes. We engineered neutralizing bispecific antibodies in the IgG-scFv format from two initially non-neutralizing antibodies, CvMab-6 (which binds to the receptor-binding domain [RBD]) and CvMab-62 (targeting a spike protein S2 subunit epitope adjacent to the known anti-S2 antibody epitope). Furthermore, we created a bispecific antibody by incorporating the scFv of bebtelovimab with our anti-S2 antibody, demonstrating significant restoration of effectiveness against bebtelovimab-resistant BQ.1.1 variants. This study highlights the potential of neutralizing bispecific antibodies, which combine existing less effective anti-RBD antibodies with anti-S2 antibodies, to revive the effectiveness of antibody therapeutics compromised by immune-evading variants.

Effects of carvedilol as third-line add-on therapy on blood pressure and glucose metabolism in type 2 diabetic patients with chronic renal disease stage 3 and above.

BACKGROUND: We evaluated the effect of coadministration of ß-blocker (carvedilol) as the third agent with angiotensin II receptor blockers (ARB) and calcium channel blockers (CCB) on blood pressure (BP) regulation and glucose metabolism. METHODS: Diabetic patients who did not achieve the therapeutic BP goal (140/90 mmHg) by ARB and CCB combination therapy were recruited. This study was designed to compare the BP regulating effects by adding carvedilol (10 mg/day, n=30) and by doubling the dose of either ARB (n=34) or CCB (n=31). Serum glucose metabolism was examined. RESULTS: The carvedilol group showed a decrease (P<0.01) in BP from 166±11/90±8 to 156±9/84±7 mmHg at 12 weeks. In the ARB and CCB groups, BP also decreased (P<0.01) from 164±11/87±8 to 153±10/83±8 and 163±7/87±8 to 153±8/84±9 mmHg at 12 weeks. The rates of achieving therapeutic goal at 12 weeks were 36.7% in the carvedilol, 38.2% in the ARB and 41.9% in the CCB group. Serum glucose metabolism did not change in all groups. CONCLUSIONS: These results suggest that adding carvedilol decreased BP as safely as increasing the dose of ARB or CCB in patients with diabetic nephropathy.

The antiplatelet effect of mirtazapine is mediated by co-blocking 5-HT2A and α2-adrenergic receptors on platelets: An in vitro human plasma-based study.

Mirtazapine (MTZ) is a noradrenergic and specific serotonergic antidepressant that has been associated with an increased risk of bleeding. However, there is insufficient evidence confirming this association. We hypothesised that 5-HT2A and α2 receptor-mediated inhibitory effects of MTZ on platelets suppress platelet aggregation and increase the risk of bleeding. In this study, we examined the antiplatelet effect of MTZ on human platelets to test our hypothesis. Blood samples for platelet aggregation tests were obtained from 14 healthy volunteers. The antiplatelet effect of MTZ was evaluated using light transmission aggregometry. MTZ significantly suppressed platelet aggregation mediated both by the synergistic interaction of serotonin (5-HT) and adrenaline and the synergistic interaction of ADP and 5-HT or adrenaline. In conclusion, MTZ exerts its antiplatelet effects by co-blocking the 5-HT2A and α2-adrenergic receptors on platelets and also suppresses platelet aggregation induced by ADP and 5-HT or adrenaline. Therefore, when MTZ is used, especially for patients with a high risk of bleeding, the significance of its use must be considered carefully. In addition, the platelet aggregation pattern by adrenaline + 5-HT, ADP + adrenaline, and ADP + 5-HT was similar between humans and mice; however, this study did not directly compare the effects of MTZ on human and murine platelets. Therefore, under the conditions for inducing platelet aggregation using adrenaline + 5-HT, ADP + adrenaline, and ADP + 5-HT, mouse platelets can be used in the evaluation of the efficacy of antiplatelet drugs in humans.

Risk Factors Associated With Unplanned Acute Care in Outpatient Chemotherapy With Oral Anticancer Drugs as Monotherapy or Combination Therapy With Injectable Anticancer Drugs.

BACKGROUND/AIM: Recently, the number of patients with cancer receiving outpatient chemotherapy using oral anticancer drugs has increased, but the currently available outpatient cancer chemotherapy is not safer than that available before. The present study aimed to identify risk factors associated with unplanned acute care (UAC) requiring outpatient chemotherapy-related consultation and hospitalisation. PATIENTS AND METHODS: We conducted a case- control study among 1,674 patients who received oral anticancer drug treatment either alone or in combination with injectable anticancer drugs at National Cancer Center Hospital East, Japan, between December 1, 2014, and November 30, 2015. RESULTS: Body mass index (BMI) was identified as a risk factor for UAC during chemotherapy. Patients with a BMI of <18.5 kg/m2, classified as underweight according to the World Health Organization classification of nutritional status, had a significantly higher risk of UAC. CONCLUSION: A low BMI immediately before the occurrence of chemotherapy-related UAC is a risk factor for adverse effects; therefore, underweight patients need more careful monitoring and supportive care.

Human hepatocyte-derived extracellular vesicles attenuate the carbon tetrachloride-induced acute liver injury in mice.

Acute liver injury (ALI) induced by chemicals or viruses can progress rapidly to acute liver failure (ALF), often resulting in death of patients without liver transplantation. Since liver transplantation is limited due to a paucity of donors, expensive surgical costs, and severe immune rejection, novel therapies are required to treat liver injury. Extracellular vesicles (EVs) are used for cellular communication, carrying RNAs, proteins, and lipids and delivering them intercellularly after being endocytosed by target cells. Recently, it was reported that EVs secreted from human hepatocytes have an ability to modulate the immune responses; however, these roles of EVs secreted from human hepatocytes were studied only with in vitro experiments. In the present study, we evidenced that EVs secreted from human hepatocytes attenuated the CCL4-induced ALI by inhibiting the recruitment of monocytes through downregulation of chemokine receptor in the bone marrow and recruitment of neutrophils through the reduction of C-X-C motif chemokine ligand 1 (CXCL1) and CXCL2 expression levels in the liver.

Silent brain infarction and rapid decline of kidney function in patients with CKD: a prospective cohort study.

BACKGROUND: Several reports have found that chronic kidney disease (CKD) is an independent risk factor for stroke. However, little is known about whether cerebrovascular disease conversely predicts the outcome of kidney function. In view of the similarities between vascular beds of the kidney and brain, we hypothesized that silent brain infarction (SBI) could reflect the degree of injury in renal small vessels and predict the risk of progression of kidney disease. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 142 patients with CKD (stages 3-5) admitted to our clinic for education about CKD from January 2006 to July 2007 were recruited and followed up for 2 years. PREDICTOR: SBI. OUTCOMES: Composite primary outcomes: doubling of serum creatinine level, development of end-stage renal disease defined as dialysis or transplant, and death from cardiovascular causes. Secondary outcome: rate of decrease in estimated glomerular filtration rate. MEASUREMENTS: Brain magnetic resonance imaging was performed to determine the presence or absence of SBI. RESULTS: At baseline, 87 patients had SBI. During follow-up, 43 patients (30.3%) developed the following primary outcomes: doubling of serum creatinine level (8 patients), dialysis therapy (32 patients), and death from cardiovascular causes (3 patients). In crude analysis, the presence of SBI predicted time to primary outcomes (P=0.01). A multivariate Cox model confirmed the presence of SBI to be an independent predictor of study outcomes (HR, 2.16; 95% CI, 1.01-4.64; P=0.04). Estimated glomerular filtration rate decreased more in patients with SBI than in those without SBI (-0.11/y vs -0.06/y relative to baseline value; P=0.005). LIMITATIONS: Study size was small. CONCLUSION: We showed that SBI was an important independent prognostic factor for the progression of kidney disease in patients with CKD. Our findings suggest that patients with SBI should be considered a high-risk population for decreased kidney function.

An Automatic Image Collection System for Multicenter Clinical Studies.

The acquisition of medical images from multiple medial institutions has become important for high-quality clinical studies. In recent years, electronic data submission has enabled the transmission of image data to independent institutions more quickly and easily than before. However, the selection, anonymization, and transmission of medical images still require human resources in the form of clinical research collaborators. In this study, we developed an image collection system that works with the electronic data capture (EDC) system. In this image collection system, medical images are selected based on EDC input information, patient ID is anonymized to a subject ID issued by the EDC, and the selected anonymized images are transferred to the research institute without human intervention. In the research institute, clinical information registered by the EDC and clinical images collected by the image collection system are managed by the same subject ID and can be used for clinical studies. In October 2019, our image collection system was introduced to 13 medical institutions and has now begun collecting medical images from the in-hospital picture archiving and communication system (PACS) of those institutions.

Overexpression of miR-669m inhibits erythroblast differentiation.

MicroRNAs (miRNAs), one of small non-coding RNAs, regulate many cell functions through their post-transcriptionally downregulation of target genes. Accumulated studies have revealed that miRNAs are involved in hematopoiesis. In the present study, we investigated effects of miR-669m overexpression on hematopoiesis in mouse in vivo, and found that erythroid differentiation was inhibited by the overexpression. Our bioinformatic analyses showed that candidate targets of miR-669m which are involved in the erythropoiesis inhibition are A-kinase anchoring protein 7 (Akap7) and X-linked Kx blood group (Xk) genes. These two genes were predicted as targets of miR-669m by two different in silico methods and were upregulated in late erythroblasts in a public RNA-seq data, which was confirmed with qPCR. Further, miR-669m suppressed luciferase reporters for 3' untranslated regions of Akap7 and Xk genes, which supports these genes are direct targets of miR-669m. Physiologically, miR-669m was not expressed in the erythroblast. In conclusion, using miR-669m, we found Akap7 and Xk, which may be involved in erythroid differentiation, implying that manipulating these genes could be a therapeutic way for diseases associated with erythropoiesis dysfunction.

Dasatinib exacerbates splenomegaly of mice inoculated with Epstein-Barr virus-infected lymphoblastoid cell lines.

Latent infection of Epstein-Barr virus (EBV) is associated with a poor prognosis in patients with B cell malignancy. We examined whether dasatinib, a multi kinase inhibitor, which is broadly used for chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia is effective on EBV-positive B cell malignancies, using lymphoblastoid cell lines (LCLs) in vitro and in vivo. As a result, in vitro experiments showed that dasatinib induced cell death of the EBV-LCLs which was not accompanied with a lytic reactivation of EBVs. To evaluate the effectiveness in EBV latency type III represented by immunodeficiency lymphoma, LCL-inoculated immunodeficient NOD/shi-scid/Il2rgnul (NOG) mice were treated with dasatinib. However, in vivo experiments revealed that dasatinib treatment exacerbated tumor cell infiltration into the spleen of LCL-inoculated NOG mice, whereas tumor size at the inoculated site was not affected by the treatment. These results suggest that dasatinib exacerbates the pathogenesis at least in some situations although the drug is effective in vitro. Hence, we should carefully examine a possibility of dasatinib repositioning for EBV+ B cell malignancies.