Soft-shelled turtle iridovirus enters cells via cholesterol-dependent, clathrin-mediated endocytosis as well as macropinocytosis.

Ranaviruses are nucleoplasmic large DNA viruses that can cause major economic losses in the aquaculture industry and pose a severe threat to global ecological diversity. The available literature demonstrates that classifiable members of the genus Ranavirus enter cells via multiple and complicated routes. Here, we demonstrated the underlying cellular entry mechanism of soft-shelled turtle iridovirus (STIV) using green fluorescence tagged recombinant virus. Treatment with chlorpromazine, sucrose, ethyl-isopropyl amiloride, chloroquine or bafilomycin A1 all significantly decreased STIV infection, suggesting that STIV uses clathrin-mediated endocytosis and macropinocytosis to enter cells via a pH-dependent pathway. Depletion of cellular cholesterol with methyl-ß-cyclodextrin significantly inhibited STIV entry, but neither filipin III nor nystatin did, suggesting that STIV entry was cholesterol dependent but caveola independent. Treatment with dynasore, genistein, ML-7 or cytochalasin D all significantly inhibited STIV infection, indicating that Rac GTPase and myosin II activity were required for the macropinocytosis-like pathway as well as actin polymerization. Our findings suggest that the molecular events involved in STIV entry are not identical to those of other ranavirus isolates. Our results also extend our understanding of the molecular mechanism of iridovirus entry and pathogenesis.

Role of BK polyomavirus (BKV) and Torque teno virus (TTV) in liver transplant recipients with renal impairment.

PURPOSE: Renal impairment is a common complication after liver transplantation (LT). While BK polyomavirus (BKV) has been linked to renal failure in kidney transplant recipients, Torque teno virus (TTV) is a surrogate marker for immunosuppression that does not have a clear association with any human disease. The impact of BKV and TTV on renal impairment after LT is unknown. METHODOLOGY: In this retrospective study, urine and serum samples from 136 liver transplant recipients were screened for BKV and TTV by quantitative PCR. In addition, serum was screened for BKV-specific antibodies and the VP1 typing region was sequenced for BKV genotyping. All parameters were correlated with clinical data.Results/Key findings. BK viruria was detected up to 21 years after transplantation in 16.9 % of cases. BK viraemia was detected in 8.7 % of patients with BK viruria up to 4 years after LT. BKV-specific antibodies were detected in 93.6 % of all LT recipients and correlated with BKV viral load in urine. There was no correlation between renal impairment and the detection of BK DNA in urine (OR 0.983). TTV DNA was detected in 84.6 % of serum samples and in 66.6 % of urine samples. The TTV viral load in serum correlated with the BKV viral load but had no impact on renal impairment. CONCLUSION: Our data indicate that the detection of BKV and TTV is not a risk factor for renal impairment after LT. A correlation of TTV and BKV viral load seems to be an indicator for the immune status of the host.

Malignancy and chemotherapy induced haemophagocytic lymphohistiocytosis in children and adolescents-a single centre experience of 20 years.

Haemophagocytic lymphohistiocytosis (HLH) is a possibly life-threatening syndrome of immune dysregulation and can be divided into primary (hereditary) and secondary forms (including malignancy-associated HLH (M-HLH)). We retrospectively analysed epidemiological, clinical, virological and laboratory data from patients with M-HLH treated at our department between 1995 and 2014. Out of 1.706 haemato-/oncologic patients treated at our department between 1995 and 2014, we identified 22 (1.29%) patients with secondary HLH (1.3-18.0, median 10.1 years; malignancy induced n = 2; chemotherapy induced n = 20). Patients with acute myeloblastic leukaemia (AML) developed HLH significantly more often than patients with acute lymphoblastic leukaemia (ALL) (10/55, 18.2% vs. 6/148, 4.1%, p = 0.0021). As possible viral triggers, we detected BKV (53.8% of the tested patients), HHV-6 (33.3%), EBV (27.8%), CMV (23.5%), ADV (16.7%) and PVB19 (16.7%) significantly more frequently than in haemato-/oncologic patients without HLH. Despite lacking evidence of concurrent bacterial infection, C-reactive protein (CRP) and procalcitotnin (PCT) were elevated in 94.7 and 77.7% of the patients, respectively. Ferritin and sIL2R were markedly elevated in all patients. HLH-associated mortality significantly (p = 0.0276) decreased from 66.6% (1995-2004) to 6.25% (2005-2014), suggesting improved diagnostic and therapeutic management. Awareness of HLH is important, and fever refractory to antibiotics should prompt to consider this diagnosis. Elevated ferritin and sIL2R seem to be good markers, while inflammatory markers like CRP and PCT are not useful to discriminate viral triggered HLH from severe bacterial infection. Re-/activation of several viruses may play a role as possible trigger.

A tumour necrosis factor receptor-like protein encoded by Singapore grouper iridovirus modulates cell proliferation, apoptosis and viral replication.

It has been demonstrated that tumour necrosis factor receptor (TNFR) homologues encoded by viruses are usually involved in virus immune evasion by regulating the host immune response or mediating apoptotic cell death. Here, a novel TNFR-like protein encoded by Singapore grouper iridovirus (SGIV VP51) was cloned and characterized. Amino acid analysis showed that VP51 contained three cysteine-rich domains (CRDs) and a transmembrane domain at its C terminus. The expression of VP51 in vitro enhanced cell proliferation, and affected cell cycle progression via altering the G1/S transition. Furthermore, VP51 overexpression improved cell viability during SGIV infection via inhibiting virus-induced apoptosis, evidenced by the reduction of apoptotic bodies and the decrease of caspase-3 activation. In addition, overexpression of VP51 increased viral titre and the expression of viral structural protein gene MCP and cell proliferation promoting gene ICP-18. In contrast, the expression of the viral apoptosis inducing gene, LITAF, was significantly decreased. Although all three CRDs were essential for the action of VP51, CRD2 and CRD3 exerted more crucial roles on virus-induced apoptosis, viral gene transcription and virus production, while CRD1 was more crucial for cell proliferation. Together, SGIV TNFR-like products not only affected cell cycle progression and enhanced cell growth by increasing the expression of the virus encoded cell proliferation gene, but also inhibited virus-induced apoptotic cell death by decreasing the expression of the viral apoptosis inducing gene. Our results provided new insights into understanding the underlying mechanism by which iridovirus regulated the apoptotic pathway to complete its life cycle.

Serum torque teno virus DNA titer in idiopathic pulmonary fibrosis patients with acute respiratory worsening.

OBJECTIVE: Acute respiratory worsening is defined as the unexpected rapid deterioration of idiopathic pulmonary fibrosis (IPF), and idiopathic acute respiratory worsening is known as an acute exacerbation of IPF. Torque teno virus (TTV) is a circular single-stranded DNA virus whose pathological significance remains unclear. The aim of the present study was to investigate the prevalence and titer of TTV DNA in IPF patients with acute respiratory worsening. METHODS: The serum TTV DNA titer was measured using real-time PCR in nine IPF patients (two treated with steroids and immunosuppressants; seven treated without steroids or immunosuppressants) who developed acute worsening, including five patients with acute exacerbation. The serum TTV DNA titer was also measured in eight stable IPF cases and four IPF cases of lung cancer. In addition, in order to examine time course changes in the TTV DNA titer, the titer was measured more than once, with an interval of four weeks or longer, in eight patients. RESULTS: Among the nine IPF patients with acute worsening, the TTV DNA titer was above 1×10(6) copies/mL in two subjects without acute exacerbation who had been continuously treated with steroids and immunosuppressants. Meanwhile, the mean TTV DNA titer was 2.4±2.6 (×10(4) copies/mL) in the five patients with acute exacerbation and 3.1±3.4 (×10(4) copies/mL) in the eight patients with stable IPF. Moreover, the TTV DNA titers were increased in all three IPF patients who started treatment with steroids and immunosuppressants. CONCLUSION: Our results suggest that it is unlikely that TTV is directly involved in the onset of acute exacerbation of IPF and that the serum TTV DNA titer potentially reflects the immunosuppressive state of the host due to treatment.

Involvement of the PI3K and ERK signaling pathways in largemouth bass virus-induced apoptosis and viral replication.

Increased reports demonstrated that largemouth Bass, Micropterus salmoides in natural and artificial environments were always suffered from an emerging iridovirus disease, largemouth Bass virus (LMBV). However, the underlying mechanism of LMBV pathogenesis remained largely unknown. Here, we investigated the cell signaling events involved in virus induced cell death and viral replication in vitro. We found that LMBV infection in epithelioma papulosum cyprini (EPC) cells induced typical apoptosis, evidenced by the appearance of apoptotic bodies, cytochrome c release, mitochondrial membrane permeabilization (MMP) destruction and reactive oxygen species (ROS) generation. Two initiators of apoptosis, caspase-8 and caspase-9, and the executioner of apoptosis, caspase-3, were all significantly activated with the infection time, suggested that not only mitochondrion-mediated, but also death receptor-mediated apoptosis were involved in LMBV infection. Reporter gene assay showed that the promoter activity of transcription factors including p53, NF-κB, AP-1 and cAMP response element-binding protein (CREB) were decreased during LMBV infection. After treatment with different signaling pathway inhibitors, virus production were significantly suppressed by the inhibition of phosphatidylinositol 3-kinase (PI3K) pathway and extracellular-signal-regulated kinases (ERK) signaling pathway. Furthermore, LMBV infection induced apoptosis was enhanced by PI3K inhibitor LY294002, but decreased by addition of ERK inhibitor UO126. Therefore, we speculated that apoptosis was sophisticatedly regulated by a series of cell signaling events for efficient virus propagation. Taken together, our results provided new insights into the molecular mechanism of ranavirus infection.

Differential viral propagation and induction of apoptosis by grouper iridovirus (GIV) in cell lines from three non-host species.

Grouper iridovirus (GIV), belonging to the Ranavirus genus of the Iridoviridae family, was demonstrated to differentially express viral genes and induce apoptosis in three non-host fish cell lines rainbow trout monocyte/macrophage (RTS11), chinook salmon embryonic (CHSE-214) and fathead minnow Epithelioma papulosum cyprinid (EPC). These cells were challenged with GIV and virus entry into all three cell lines was confirmed by the expression of viral immediate early genes. The expression of the late major capsid protein gene was detected in CHSE-214 and EPC, but not in RTS11, suggesting an earlier termination in the viral replication cycle in RTS11. Approximately 12h after infection with GIV, cell death was prominent in all three non-host cell lines. Death was later confirmed to be apoptosis by the presence of chromosomal DNA fragmentation and phosphatidylserine externalization. To determine whether apoptosis was protein related or gene expression related, the three cell lines were challenged with heat-inactivated GIV and UV-treated GIV (GIV(UV)). The heat inactivation abolished apoptosis in all three cell lines, but each cell line responded differently to GIV(UV). Relative to GIV, GIV(UV) caused no apoptosis in CHSE-214, decreased apoptosis in RTS11, and increased apoptosis in EPC. These results suggest that early GIV gene expression was needed for apoptosis in CHSE-214 but impeded apoptosis in EPC. At the cellular level, only EPC is a permissive host as EPC was the only cell line of the three capable of producing a moderate increase in virus titer. The three non-host cell lines present a good system for potentially identifying different components of GIV-induced apoptotic pathways in future studies.

Infectious spleen and kidney necrosis virus (a fish iridovirus) enters Mandarin fish fry cells via caveola-dependent endocytosis.

Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the genus Megalocytivirus from the family Iridoviridae. Megalocytiviruses have been implicated in more than 50 fish species infections and currently threaten the aquaculture industry, causing great economic losses in China, Japan, and Southeast Asia. However, the cellular entry mechanisms of megalocytiviruses remain largely uncharacterized. In this study, the main internalization mechanism of ISKNV was investigated by using mandarin fish fry (MFF-1) cells. The progression of ISKNV infection is slow, and infection is not inhibited when the cells are treated with ammonium chloride (NH(4)Cl), chloroquine, sucrose, and chlorpromazine, which are inhibitors of clathrin-dependent endocytosis. The depletion of cellular cholesterol by methyl-ß-cyclodextrin results in the significant inhibition of ISKNV infection; however, the infection is resumed with cholesterol replenishment. Inhibitors of caveolin-1-involved signaling events, including phorbol 12-myristate 13-acetate (PMA), genistein, and wortmannin, impair ISKNV entry into MFF-1 cells. Moreover, ISKNV entry is dependent on dynamin and the microtubule cytoskeleton. Cofraction analysis of ISKNV and caveolin-1 showed that ISKNV colocates with caveolin-1 during virus infection. These results indicate that ISKNV entry into MFF-1 cells proceeds via classical caveola-mediated endocytosis and is dependent on the microtubules that serve as tracks along which motile cavicles may move via a caveola-caveosome-endoplasmic reticulum (ER) pathway. As a fish iridovirus, ISKNV entry into MFF-1 cells is different from the clathrin-mediated endocytosis of frog virus 3 entry into mammalian cells (BHK-21) at 28°C, which has been recognized as a model for iridoviruses. Thus, our work may help further the understanding of the initial steps of iridovirus infection.

Singapore grouper iridovirus, a large DNA virus, induces nonapoptotic cell death by a cell type dependent fashion and evokes ERK signaling.

Virus induced cell death, including apoptosis and nonapoptotic cell death, plays a critical role in the pathogenesis of viral diseases. Singapore grouper iridovirus (SGIV), a novel iridovirus of genus Ranavirus, causes high mortality and heavy economic losses in grouper aquaculture. Here, using fluorescence microscopy, electron microscopy and biochemical assays, we found that SGIV infection in host (grouper spleen, EAGS) cells evoked nonapoptotic programmed cell death (PCD), characterized by appearance of cytoplasmic vacuoles and distended endoplasmic reticulum, in the absence of DNA fragmentation, apoptotic bodies and caspase activation. In contrast, SGIV induced typical apoptosis in non-host (fathead minnow, FHM) cells, as evidenced by caspase activation and DNA fragmentation, suggesting that SGIV infection induced nonapoptotic cell death by a cell type dependent fashion. Furthermore, viral replication was essential for SGIV induced nonapoptotic cell death, but not for apoptosis. Notably, the disruption of mitochondrial transmembrane potential (ΔΨm) and externalization of phosphatidylserine (PS) were not detected in EAGS cells but in FHM cells after SGIV infection. Moreover, the extracellular signal-regulated kinase (ERK) signaling was involved in SGIV infection induced nonapoptotic cell death and viral replication. This is a first demonstration of ERK-mediated nonapoptotic cell death induced by a DNA virus. These findings contribute to understanding the mechanisms of iridovirus pathogenesis.

Context-dependent effects of ranaviral infection on northern leopard frog life history traits.

Pathogens have important effects on host life-history traits, but the magnitude of these effects is often strongly context-dependent. The outcome of an interaction between a host and an infectious agent is often associated with the level of stress experienced by the host. Ranavirus causes disease and mortality in amphibian populations in various locations around the world, but most known cases of ranaviral infection have occurred in North America and the United Kingdom. While Ranavirus virulence has been investigated, the outcome of Ranavirus infection has seldom been related to the host environment. In a factorial experiment, we exposed Northern leopard frog (Lithobates pipiens, formerly Rana pipiens) tadpoles to different concentrations of Ranavirus and investigated the effect of host density on certain life-history traits, namely survival, growth rate, developmental stage and number of days from virus exposure to death. Our results suggest a prominent role of density in driving the direction of the interaction between L. pipiens tadpoles and Ranavirus. We showed that increasing animal holding density is detrimental for host fitness as mortality rate is higher, day of death earlier, development longer and growth rate significantly lower in high-density tanks. We observed a linear increase of detrimental effects when Ranavirus doses increased in low-density conditions, with control tadpoles having a significantly higher overall relative fitness. However, this pattern was no longer observed in high-density conditions, where the effects of increasing Ranavirus dose were limited. Infected and control animals fitness were consequently similar. We speculate that the host may eventually diverts the energy required for a metabolic/immune response triggered by the infection (i.e., direct costs of the infection) to better cope with the increase in environmental "stress" associated with high density (i.e., indirect benefits of the infection). Our results illustrate how the net fitness of organisms may be shaped by ecological context and emphasize the necessity of examining the direct/indirect costs and benefits balance to fully understand host-pathogen interactions.

Pathogen host switching in commercial trade with management recommendations.

Global wildlife trade exacerbates the spread of nonindigenous species. Pathogens also move with hosts through trade and often are released into naïve populations with unpredictable outcomes. Amphibians are moved commercially for pets, food, bait, and biomedicine, and are an excellent model for studying how wildlife trade relates to pathogen pollution. Ranaviruses are amphibian pathogens associated with annual population die-offs; multiple strains of tiger salamander ranaviruses move through the bait trade in the western United States. Ranaviruses infect amphibians, reptiles, and fish and are of additional concern because they can switch hosts. Tiger salamanders are used as live bait for freshwater fishing and are a potential source for ranaviruses switching hosts from amphibians to fish. We experimentally injected largemouth bass with a bait trade tiger salamander ranavirus. Largemouth bass became infected but exhibited no signs of disease or mortality. Amphibian bait ranaviruses have the potential to switch hosts to infect fish, but fish may act as dead-end hosts or nonsymptomatic carriers, potentially spreading infection as a result of trade.

The discovery and characterization of Mimivirus, the largest known virus and putative pneumonia agent.

During recent years, the usefulness of amoebal co-cultures as an alternative means of isolating and cultivating fastidious microorganisms has been increasingly recognized. While characterizing a collection of bacteria that had been isolated using this approach, we encountered an organism that, on preliminary analysis, appeared to be a gram-positive coccus. However, additional examination revealed that it was not a bacterium but rather, surprisingly, a virus. The dimensions of the virus particle (diameter, 0.8 microm) and its genome size (1.2 Mb) are far more akin to those of bacteria than to those of previously recognized viruses. These characteristics, together with such features as the breadth and complexity of its gene content, challenge the current definition of a "virus." Furthermore, the virus, now named "Mimivirus," has been implicated as an agent of pneumonia in humans and, thus, should be considered a putative emerging pathogen.

High torquetenovirus loads are correlated with bronchiectasis and peripheral airflow limitation in children.

BACKGROUND: The aim of the study was to evaluate the prevalence of torquetenovirus (TTV) infection in a group of children with recurrent lower respiratory tract infections and radiologic evidence of bronchiectasis. Correlations between TTV loads and severity of bronchiectasis and between TTV loads and lung function were evaluated. METHODS: In 38 subjects, high-resolution computed tomography (HRCT) and plasma tests for TTV detection and quantification were done. In 21/38 subjects, spirometry was also performed. RESULTS: TTV was found in 31/38 (81.6%) patients. The correlation between TTV loads and severity of bronchiectasis was statistically significant (r = 0.548; P = 0.01). TTV loads showed inverse correlation with FEF25-75% (r = -0.541; P = 0.011), and FEF25-75%/FVC (r = -0.512; P = 0.018). Inverse correlation was found also between severity of bronchiectasis and functional lung parameters: FEF25-75% (r = -0.635; P = 0.002), FEV1/FVC (r = -0.541; P = 0.011), and FEF25-75%/FVC (r = -0.645; P = 0.002). CONCLUSIONS: This study demonstrated the high prevalence of TTV infection in children with bronchiectasis. Moreover, we have shown a significant correlation between TTV loads and airflow limitation within the peripheral airways, as well as between severity of bronchiectasis and decrease of lung function.

Challenging successive mosquito generations with a densonucleosis virus yields progressive survival improvement but persistent, innocuous infections.

Research on cultivated shrimp suggests that they have the capability to tolerate viral pathogens in a highly specific manner by mechanisms currently unknown. The phenomenon is difficult to study in detail because they have a generation time of 1-2yr and lack continuous cell lines. Thus, we developed a mosquito-densovirus model to examine whether similar phenomena occur in insects. Serial challenge of five generations with a stock densovirus (AThDNV) resulted in progressive survival increases from 15% to 58%. Prevalence of AThDNV infection in surviving mosquito larvae (confirmed by PCR, histology, in situ hybridization and transmission electron microscopy) was relatively high (e.g. 36% in F2) but they grew normally to establish each succeeding generation. At the end of five generations, comparison of deduced amino acid sequences from genome fragments revealed a significantly higher (p=0.02) estimated prevalence of defective targets in the survivor virus population (29.7%+/-10.0 SD) than in the stored viral population (3.3%+/-5.8 SD). The results paralleled those reported for serially passaged C6/36 mosquito cell cultures infected with a densovirus. There, reduced infection rates are ascribed to the production of defective interfering particles (DIP). Thus, it is possible that the presence of prior AThDNV infections with a high level of DIP contributed to improved survival in our challenged F4 mosquito population. If so, it suggests that persistent viral infections in arthropods may serve in a specific, adaptive manner to reduce the incidence and severity of disease.

SEN virus prevalence among non-B and non-C hepatitis patients with high liver function tests in the south of Turkey.

We investigated the characteristics and detection rates of SEN virus (SENV) infection among 100 Turkish patients who had with high alanine aminotransferase (ALT) and aspartate aminotransferase levels but were negative for HBV DNA and HCV RNA and had no history of transfusion. As a control group, we also analyzed 50 healthy individuals who had normal ALT levels, were negative for HBV DNA and HCV RNA, and had no history of transfusion. The serum samples of patient and controls were analyzed by PCR to detect the presence of SENV DNA and its two genotypes (SENV-H and SENV-D). We detected SENV DNA in 13 of 100 (13%) patients. Five of 13 (38.46%) patients were positive for SENV-D and 8 of 13 (61.53%) patients were positive for SENV-H DNA. We also detected SENV DNA in 5 of 50 (10%) patients in the control group. Two of 5 (40%) patients were positive for SENV-D and 3 of 5 (60%) patients were positive for SENV-H DNA in the control group. SENV was detected at almost the same frequency in the patient and control group. SENV did not seem to contribute to the pathogenesis of liver disease (P > 0.05) in this cohort. Our results also showed that SENV transmission was not only associated with blood transfusion but also with some other possible routes.

Influence of temperature on Ranavirus infection in larval salamanders Ambystoma tigrinum.

Temperature strongly influenced percent mortality and time to death of salamanders exposed to the Ambystoma tigrinum virus (iridovirus) (ATV). Most salamanders survived when exposed at 26 degrees C, whereas all died at 18 degrees C and nearly all died at 10 degrees C. Some asymptomatic salamanders that survived 60 d at 10 or 26 degrees C were found to be carrying virus. Polymerase chain reaction (PCR) confirmed the presence of virus in ATV-exposed salamanders but was found to be less sensitive than cell culture in detecting ATV at low concentrations. PCR products were 100% identical to ATV in the major capsid protein sequence. Virus titer was higher in salamanders held at 10 degrees C than at 18 degrees C but little virus, if any, was present in the small number of salamanders that died at 26 degrees C. These results may help explain periodic viral epizootics in field populations of A. tigrinum where water temperatures fluctuate widely.

Induction of apoptosis in a flounder gill cell line by lymphocystis disease virus infection.

Lymphocystis disease virus (LCDV), a large icosahedral DNA virus classified to the iridovirus family, is the causative agent of lymphocystis, a disease which occurs in marine and freshwater fish species and is characterized by formation of papilloma-like lesions on the surface of the skin. In vitro, LCDV infection causes flounder gill cells, an adherent cell line, to exhibit an obvious cytopathic effect (CPE). In order to test whether apoptosis is responsible for the observed CPE, cells infected with LCDV at a multiplicity of infection (m.o.i.) of 5 PFU per cell were examined at various time intervals for the appearance of apoptotic signs. Nuclear fragmentation, DNA laddering and caspase activation were observed in the infected cells at the time (i.e. 10 days post-infection) when an intensive CPE was observed. These findings demonstrate that LCDV is capable of inducing apoptosis in vitro, which is different from the result of LCDV infection in vivo, and consequently suggest an intricate LCDV-host interaction.

Experimental infection of lacertids with lizard erythrocytic viruses.

OBJECTIVE: Lizard erythrocytic viruses (LEVs) produce inclusions in the cytoplasm of erythrocytes, but their impact on the infected host is poorly understood. This work reports on an experimental study of the infection process in Lacerta monticola and Lacerta schreiberi from Serra da Estrela Mountain, Portugal. METHODS: A time sequence light microscope and transmission electron microscope (TEM) study of the infection process was performed in peripheral blood erythrocytes of experimentally infected lizards. Virions were searched for by TEM in visceral organs and bone marrow of the animals. RESULTS: Infection was usually restricted to erythrocytes, but occasionally became systemic and induced disease. In the first case, a prevalence of infected erythrocytes of up to 98% followed by recovery was observed. In the latter, infection spread to leukocytes, leading to the death of the infected animals. CONCLUSIONS: The potential of LEVs to induce systemic infections was demonstrated. Sequential TEM examination of LEV-infected cells is described for the first time, demonstrating features such as dense inclusions related to virus nucleoid formation, intranuclear virions, intermediate structures in virion capsid morphogenesis and virus release by budding.

SEN virus infection does not affect the progression of non-A to -E liver disease.

SEN virus (SEN V) was discovered recently as a potential causative agent of non-A, non-B, non-C, and non-E (non-A to -E) hepatitis. The aim of this study was to obtain information about the prevalence of this virus in Japan and its association with non-A to -E liver disease. Sixty-seven patients hospitalized for non-A to -E liver disease, including hepatocellular carcinoma (19 patients), cirrhosis (7 patients), chronic hepatitis (18 patients), and acute hepatitis (23 patients), were tested, along with 49 blood donors. The patients were admitted to Nihon University Hospital between 1991 and 1998. SEN V DNA was detected by a nested polymerase chain reaction, targeting the 5' untranslated region. SEN V DNA was detected in 14 of 49 (28.6%) blood donors and in 33 of 67 (49.3%) patients with non-A to -E liver disease. The prevalence of SEN V DNA was similar among patients with various liver diseases, including hepatocellular carcinoma (42.1%), cirrhosis (57.1%), chronic hepatitis (55.6%) and acute hepatitis (47.8%) and among blood donors (28.6%). There were no significant differences in the clinical profiles of patients with SEN V DNA-positive or -negative chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Similarly, there were no significant differences in the clinical profiles between patients with SEN V DNA-positive and -negative acute hepatitis. In conclusion, SEN V infection is present among many blood donors and is common in patients with non-A to -E liver disease. There are insufficient data to prove a causal role for SEN virus infection in non-A to -E liver disease.