Viruses Infecting the European Catfish (Silurus glanis).

In aquaculture, disease management and pathogen control are key for a successful fish farming industry. In past years, European catfish farming has been flourishing. However, devastating fish pathogens including limiting fish viruses are considered a big threat to further expanding of the industry. Even though mainly the ranavirus (Iridoviridea) and circovirus (Circoviridea) infections are considered well- described in European catfish, more other agents including herpes-, rhabdo or papillomaviruses are also observed in the tissues of catfish with or without any symptoms. The etiological role of these viruses has been unclear until now. Hence, there is a requisite for more detailed information about the latter and the development of preventive and therapeutic approaches to complete them. In this review, we summarize recent knowledge about viruses that affect the European catfish and describe their origin, distribution, molecular characterisation, and phylogenetic classification. We also highlight the knowledge gaps, which need more in-depth investigations in the future.

Pigeon adenovirus and pigeon torque teno virus associated with acute multifocal hepatic necrosis in pigeons in Queensland, Australia.

In 2018, an outbreak resulting in deaths of 28 breeding pigeons was reported north of Brisbane, Australia. The affected birds had runny nasal discharge and poor body condition. Two birds were submitted to Biosecurity Sciences Laboratory, Brisbane, for investigation. A range of diagnostic tests excluded a number of known pathogens, and no virus was isolated in cell culture. Histopathological examination revealed severe acute multifocal necrosis in the liver with eosinophilic intranuclear inclusions in hepatocytes and Kupffer cells. High-throughput sequencing (HTS) revealed full-length sequences for pigeon adenovirus 1 (PiAd-A) and pigeon torque teno virus (PTTV). This report indicates concomitant PiAd-1and PTTV infections in Australian pigeons.

Function and Regulation of Nuclear DNA Sensors During Viral Infection and Tumorigenesis.

IFI16, hnRNPA2B1, and nuclear cGAS are nuclear-located DNA sensors that play important roles in initiating host antiviral immunity and modulating tumorigenesis. IFI16 triggers innate antiviral immunity, inflammasome, and suppresses tumorigenesis by recognizing double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), damaged nuclear DNA, or cooperatively interacting with multiple tumor suppressors such as p53 and BRCA1. hnRNPA2B1 initiates interferon (IFN)-α/ß production and enhances STING-dependent cytosolic antiviral signaling by directly binding viral dsDNA from invaded viruses and facilitating N6 -methyladenosine (m6A) modification of cGAS, IFI16, and STING mRNAs. Nuclear cGAS is recruited to double-stranded breaks (DSBs), suppresses DNA repair, and promotes tumorigenesis. This review briefly describes the nuclear functions of IFI16, hnRNPA2B1, and cGAS, and summarizes the transcriptional, post-transcriptional, and post-translational regulation of these nuclear DNA sensors.

Metagenomic analysis of DNA viruses from posttransplant lymphoproliferative disorders.

Posttransplant lymphoproliferative disorders (PTLDs), 50%-80% of which are strongly associated with Epstein-Barr virus (EBV), carry a high morbidity and mortality. Most clinical/epidemiological/tumor characteristics do not consistently associate with worse patient survival, so our aim was to identify if other viral genomic characteristics associated better with survival. We extracted DNA from stored paraffin-embedded PTLD tissues at our center, identified viral sequences by metagenomic shotgun sequencing (MSS), and analyzed the data in relation to clinical outcomes. Our study population comprised 69 PTLD tissue samples collected between 1991 and 2015 from 60 subjects. Nucleotide sequences from at least one virus were detected by MSS in 86% (59/69) of the tissues (EBV in 61%, anelloviruses 52%, gammapapillomaviruses 14%, CMV 7%, and HSV in 3%). No viruses were present in higher proportion in EBV-negative PTLD (compared to EBV-positive PTLD). In univariable analysis, death within 5 years of PTLD diagnosis was associated with anellovirus (P = 0.037) and gammapapillomavirus (P = 0.036) detection by MSS, higher tissue qPCR levels of the predominant human anellovirus species torque teno virus (TTV; P = 0.016), T cell type PTLD, liver, brain or bone marrow location. In multivariable analyses, T cell PTLD (P = 0.006) and TTV PCR level (P = 0.012) remained significant. In EBV-positive PTLD, EBNA-LP, EBNA1 and EBNA3C had significantly higher levels of nonsynonymous gene variants compared to the other EBV genes. Multiple viruses are detectable in PTLD tissues by MSS. Anellovirus positivity, not EBV positivity,was associated with worse patient survival in our series. Confirmation and extension of this work in larger multicenter studies is desirable.

FATAL RANAVIRUS INFECTION IN A GROUP OF ZOO-HOUSED MELLER'S CHAMELEONS (TRIOCEROS MELLERI).

A group of five juvenile Meller's chameleons (Trioceros melleri) experienced 100% mortality over a period of 1 mo due to ranavirus infection. The index case was found dead without premonitory signs. The three subsequent cases presented with nonspecific clinical signs (lethargy, decreased appetite, ocular discharge) and were ultimately euthanatized. The final case died after initially presenting with skin lesions. Postmortem examination revealed thin body condition in all five animals and mild coelomic effusion and petechiae affecting the tongue and kidneys of one animal. Microscopically, all animals had multifocal necrosis of the spleen, liver, and kidney; four of five animals had necrosis of the nasal cavity; and two of five had necrosis of adrenal tissue, bone marrow, and skin. Numerous basophilic intracytoplasmic inclusions were present in the liver of all animals and nasal mucosa of three of the five animals. Consensus polymerase chain reaction for herpesvirus and adenovirus were negative, whereas ranavirus quantitative polymerase chain reaction was positive. Virus isolation followed by whole genome sequencing and Bayesian phylogenetic analysis classified the isolates as a strain of frog virus 3 (FV3) most closely related to an FV3 isolate responsible for a previous outbreak in the zoo's eastern box turtle (Terrapene carolina carolina) group. This case series documents the first known occurrence of ranavirus-associated disease in chameleons and demonstrates the potential for interspecies transmission between chelonian and squamate reptiles.

Hypoxia inducible factor one alpha and human viral pathogens.

If the oxygen tension level is 21% in ambient air, it is only between 14% and 1% in vivo. Consequently, viral pathogens are exposed and must adapt to these fluctuating oxygen levels to colonize the host and cause diseases. The problem is that for many years, the virological studies have been performed at 21% oxygen levels and consequently this is a real handicap to have a correct view of the mechanistic aspects of human viral infections. In this brief review, we describe for some selected examples the interactions of human viruses with this relative hypoxia observed in vivo.

Pathogenesis of Frog Virus 3 ( Ranavirus, Iridoviridae) Infection in Wood Frogs ( Rana sylvatica).

Wood frogs ( Rana sylvatica) are highly susceptible to infection with Frog virus 3 (FV3, Ranavirus, Iridoviridae), a cause of mass mortality in wild populations. To elucidate the pathogenesis of FV3 infection in wood frogs, 40 wild-caught adults were acclimated to captivity, inoculated orally with a fatal dose of 104.43 pfu/frog, and euthanized at 0.25, 0.5, 1, 2, 4, 9, and 14 days postinfection (dpi). Mild lesions occurred sporadically in the skin (petechiae) and bone marrow (necrosis) during the first 2 dpi. Severe lesions occurred 1 to 2 weeks postinfection and consisted of necrosis of medullary and extramedullary hematopoietic tissue, lymphoid tissue in spleen and throughout the body, and epithelium of skin, mucosae, and renal tubules. Viral DNA was first detected (polymerase chain reaction) in liver at 4 dpi; by dpi 9 and 14, all viscera tested (liver, kidney, and spleen), skin, and feces were positive. Immunohistochemistry (IHC) first detected viral antigen in small areas devoid of histologic lesions in the oral mucosa, lung, and colon at 4 dpi; by 9 and 14 dpi, IHC labeling of viral antigen associated with necrosis was found in multiple tissues. Based on IHC staining intensity and lesion severity, the skin, oral, and gastrointestinal epithelium and renal tubular epithelium were important sites of viral replication and shedding, suggesting that direct contact (skin) and fecal-oral contamination are effective routes of transmission and that skin tissue, oral, and cloacal swabs may be appropriate antemortem diagnostic samples in late stages of disease (>1 week postinfection) but poor samples to detect infection in clinically healthy frogs.

Hematological and Histological Changes in Prussian Carp Carassius gibelio Infected with Cyprinid Herpesvirus 2.

Outbreaks of cyprinid herpesvirus 2 (CyHV-2) disease, also known as herpesviral hematopoietic necrosis, among cultured Prussian Carp Carassius gibelio has occurred each year in Jiangsu province, China, since 2009. In autumn 2014, hematological, blood biochemical, and histological changes in naturally infected moribund Prussian Carp were investigated after CyHV-2 was confirmed as the sole etiologic agent by etiological analyses. Total erythrocyte count, total leukocyte count, hemoglobin concentration, and thrombocyte count were significantly reduced (P < 0.01), whereas erythrocyte osmotic brittleness was significantly increased (P < 0.01) in infected fish compared with control fish. In addition, monocyte count was higher (P < 0.01) and lymphocyte count was lower (P < 0.01) in diseased fish than in control fish. The blood biochemical analyses indicated significant increases (P < 0.01) in the activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase as well as in the levels of total protein, globulin, total bilirubin, creatinine, and urea along with significant decreases (P < 0.01) in glucose and albumin in the diseased group. Histopathological examinations indicated that the kidneys and spleens of moribund Prussian Carp were the most severely lesioned organs, followed by the gills and hearts. Hypertrophied nuclei with marginated chromatin also appeared in the hearts and renal tubular epithelia from diseased fish. Pathological analysis of blood cells showed that approximately 78% of erythrocytes and 94% of leukocytes were lesioned with different levels of degeneration and necrosis in the diseased group. These previously unreported observations may be useful in the diagnosis of CyHV-2 disease. Received May 11, 2015; accepted March 24, 2016.

Concurrence of Iridovirus, Polyomavirus, and a Unique Member of a New Group of Fish Papillomaviruses in Lymphocystis Disease-Affected Gilthead Sea Bream.

UNLABELLED: Lymphocystis disease is a geographically widespread disease affecting more than 150 different species of marine and freshwater fish. The disease, provoked by the iridovirus lymphocystis disease virus (LCDV), is characterized by the appearance of papillomalike lesions on the skin of affected animals that usually self-resolve over time. Development of the disease is usually associated with several environmental factors and, more frequently, with stress conditions provoked by the intensive culture conditions present in fish farms. In gilthead sea bream (Sparus aurata), an economically important cultured fish species in the Mediterranean area, a distinct LCDV has been identified but not yet completely characterized. We have used direct sequencing of the virome of lymphocystis lesions from affected S. aurata fish to obtain the complete genome of a new LCDV-Sa species that is the largest vertebrate iridovirus sequenced to date. Importantly, this approach allowed us to assemble the full-length circular genome sequence of two previously unknown viruses belonging to the papillomaviruses and polyomaviruses, termed Sparus aurata papillomavirus 1 (SaPV1) and Sparus aurata polyomavirus 1 (SaPyV1), respectively. Epidemiological surveys showed that lymphocystis disease was frequently associated with the concurrent appearance of one or both of the new viruses. SaPV1 has unique characteristics, such as an intron within the L1 gene, and as the first member of the Papillomaviridae family described in fish, provides evidence for a more ancient origin of this family than previously thought. IMPORTANCE: Lymphocystis disease affects marine and freshwater fish species worldwide. It is characterized by the appearance of papillomalike lesions on the skin that contain heavily enlarged cells (lymphocysts). The causative agent is the lymphocystis disease virus (LCDV), a large icosahedral virus of the family Iridoviridae In the Mediterranean area, the gilthead sea bream (Sparus aurata), an important farmed fish, is frequently affected. Using next-generation sequencing, we have identified within S. aurata lymphocystis lesions the concurrent presence of an additional LCDV species (LCDV-Sa) as well as two novel viruses. These are members of polyomavirus and papillomavirus families, and here we report them to be frequently associated with the presence of lymphocysts in affected fish. Because papillomaviruses have not been described in fish before, these findings support a more ancient origin of this virus family than previously thought and evolutionary implications are discussed.

Ranavirus in an outbreak of dermatophilosis in captive inland bearded dragons (Pogona vitticeps).

BACKGROUND: Various pathogens cause skin diseases in lizards. An outbreak of skin disease occurred in a population of 100 inland bearded dragons at a breeding facility in Japan; 50 developed skin lesions and 15 mortalities were reported. HYPOTHESIS/OBJECTIVES: To identify the pathogens responsible for the skin lesions and to determine the cause of death. ANIMALS: Eight specimens (three dead, two euthanized, three living) were randomly selected from a group of inland bearded dragons with skin lesions consisting of multifocal superficial dermatitis. METHODS: Biopsy samples were taken from skin lesions and healthy skin of the live specimens. Postmortem examinations were performed on the dead and euthanized specimens. Skin samples were processed for microbiological culture, 16S ribosomal DNA (rDNA) sequencing for bacteria, ranavirus major capsid protein (MCP) gene sequencing and histopathological examination. Histopathological examinations were also performed on postmortem tissue samples. RESULTS: Both Austwickia chelonae and ranavirus (DNA) were detected in the skin lesions. Pathological examination revealed no significant visceral lesions caused by A. chelonae or ranavirus infection in dead specimens. CONCLUSIONS AND CLINICAL IMPORTANCE: To the best of the authors' knowledge this is the first report of dermatophilosis due to A. chelonae infection in lizards and the first description of a concurrent infection with a ranavirus. The combined infection associated with the skin lesions may have been the primary cause of death. Co-infection with a ranavirus should be considered as a possible factor in cases of reptilian dermatophilosis.

Broad and potent antiviral activity of the NAE inhibitor MLN4924.

In terms of infected human individuals, herpesviruses range among the most successful virus families. Subclinical herpesviral infections in healthy individuals contrast with life-threatening syndromes under immunocompromising and immunoimmature conditions. Based on our finding that cytomegaloviruses interact with Cullin Roc ubiquitin ligases (CRLs) in the context of interferon antagonism, we systematically assessed viral dependency on CRLs by utilizing the drug MLN4924. CRL activity is regulated through the conjugation of Cullins with the ubiquitin-like molecule Nedd8. By inhibiting the Nedd8-activating Enzyme (NAE), MLN4924 interferes with Nedd8 conjugation and CRL activity. MLN4924 exhibited pronounced antiviral activity against mouse and human cytomegalovirus, herpes simplex virus (HSV)- 1 (including multi-drug resistant clinical isolates), HSV-2, adeno and influenza viruses. Human cytomegalovirus genome amplification was blocked at nanomolar MLN4924 concentrations. Global proteome analyses revealed that MLN4924 blocks cytomegaloviral replication despite increased IE1 amounts. Expression of dominant negative Cullins assigned this IE regulation to defined Cullin molecules and phenocopied the antiviral effect of MLN4924.

A microRNA from infectious spleen and kidney necrosis virus modulates expression of the virus-mock basement membrane component VP08R.

Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the genus Megalocytivirus, family Iridoviridae. Infection of ISKNV is characterized by a unique pathological phenomenon in that the infected cells are attached by lymphatic endothelial cells (LECs). ISKNV mediates the formation of a virus-mock basement membrane (VMBM) structure on the surface of infected cells to provide attaching sites for LECs. The viral protein VP08R is an important component of VMBM. In this study, a novel ISKNV-encoded microRNA, temporarily named ISKNV-miR-1, was identified. ISKNV-miR-1 is complementary to the VP08R-coding sequence and can modulate VP08R expression through reducing its mRNA level. This suggests that formation of VMBM may be under fine regulation by ISKNV.

Production and characterization of a monoclonal antibody against a late gene encoded by grouper iridovirus 64L.

Viral envelope proteins play important roles in viral infection and assembly. The grouper iridovirus ORF 64L (GIV-64L) was predicted to encode an envelope protein and was conserved in all sequenced Ranaviruses. In this study, the complete nucleotide sequence of the GIV-64L gene (1215 bp) was cloned into the isopropyl ß-D-1-thiogalactopyranoside (IPTG) induction prokaryotic expression vector pET23a. The approximately 50.2 kDa recombinant GIV-64L-His protein was induced, purified and used as an immunogen to immunize BALB/c mice. Three monoclonal antibodies (mAbs), all IgG1 class antibodies against GIV-64L protein, were produced by enzyme-linked immunosorbent assay. Reverse transcription polymerase chain reaction analyses revealed GIV-64L to be a late gene when expressed in grouper kidney cells during GIV infection with cycloheximide (an inhibitor of protein synthesis) or cytosine arabinoside (an inhibitor of DNA synthesis) present. Finally, one of the established mAbs, GIV-64L-mAb-17, was used in Western blotting and an immunofluorescence assay, which showed that GIV-64L protein was expressed at 24 h post-infection and localized only in the cytoplasm in GIV-infected cells, packed into a whole virus particle. The presently characterized GIV-64L mAbs should have widespread applications in GIV immunodiagnostics and other research, and these results should offer important insights into the pathogenesis of GIV.

Nonclassical MHC-Restricted Invariant Vα6 T Cells Are Critical for Efficient Early Innate Antiviral Immunity in the Amphibian Xenopus laevis.

Nonclassical MHC class Ib-restricted invariant T (iT) cell subsets are attracting interest because of their potential to regulate immune responses against various pathogens. The biological relevance and evolutionary conservation of iT cells have recently been strengthened by the identification of iT cells (invariant Vα6 [iVα6]) restricted by the nonclassical MHC class Ib molecule XNC10 in the amphibian Xenopus laevis. These iVα6 T cells are functionally similar to mammalian CD1d-restricted invariant NKT cells. Using the amphibian pathogen frog virus 3 (FV3) in combination with XNC10 tetramers and RNA interference loss of function by transgenesis, we show that XNC10-restricted iVα6 T cells are critical for early antiviral immunity in adult X. laevis. Within hours following i.p. FV3 infection, iVα6 T cells were specifically recruited from the spleen into the peritoneum. XNC10 deficiency and concomitant lack of iVα6 T cells resulted in less effective antiviral and macrophage antimicrobial responses, which led to impaired viral clearance, increased viral dissemination, and more pronounced FV3-induced kidney damage. Together, these findings imply that X. laevis XNC10-restricted iVα6 T cells play important roles in the early anti-FV3 response and that, as has been suggested for mammalian invariant NKT cells, they may serve as immune regulators polarizing macrophage effector functions toward more effective antiviral states.

First case of ranavirus and associated morbidity and mortality in an eastern mud turtle Kinosternon subrubrum in South Carolina.

Ranaviruses are double-stranded DNA viruses that infect amphibians, fish, and reptiles, causing global epidemics in some amphibian populations. It is important to identify new species that may be susceptible to the disease, particularly if they reside in the same habitat as other at-risk species. On the Savannah River Site (SRS) in Aiken, South Carolina, USA, ranaviruses are present in several amphibian populations, but information is lacking on the presence, prevalence, and morbidity of the virus in reptile species. An eastern mud turtle Kinosternon subrubrum captured on the SRS in April 2014 exhibited clinical signs of a ranaviral infection, including oral plaque and conjunctivitis. Quantitative PCR analyses of DNA from liver tissue, ocular, oral, nasal, and cloacal swabs were all positive for ranavirus, and sequencing of the template confirmed infection with a FV3-like ranavirus. Histopathologic examination of postmortem tissue samples revealed ulceration of the oral and tracheal mucosa, intracytoplasmic epithelial inclusions in the oral mucosa and tongue sections, individualized and clusters of melanomacrophages in the liver, and bacterial rods located in the liver, kidney, heart, stomach, and small intestine. This is the first report of morbidity and mortality of a mud turtle with a systemic ranaviral infection.

Morphological changes in amphibian and fish cell lines infected with Andrias davidianus ranavirus.

Andrias davidianus ranavirus (ADRV) is an emerging viral pathogen that causes severe disease in Chinese giant salamanders, the largest extant amphibian in the world. A fish cell line, Epithelioma papulosum cyprinid (EPC), and a new amphibian cell line, Chinese giant salamander spleen cell (GSSC), were infected with ADRV and observed by light and electron microscopy. The morphological changes in these two cell lines infected with ADRV were compared. Cytopathic effect (CPE) began with rounding of the cells, progressing to cell detachment in the cell monolayer, followed by cell lysis. Significant CPE was visualized as early as 24 h post infection (hpi) in EPC cells and at 36 hpi in GSSC cells. Microscopical examination showed clear and significant CPE in EPC cells, while less extensive and irregular CPE with some adherent cells remaining was observed in GSSC cells. Following ADRV infection, CPE became more extensive. Transmission electron micrographs showed many virus particles around cytoplasmic vacuoles, formed as crystalline arrays or scattered in the cytoplasm of infected cells. Infected cells showed alteration in nuclear morphology, with condensed and marginalized nuclear chromatin on the inner aspect of the nuclear membrane and formation of a cytoplasmic viromatrix adjacent to the nucleus in both cell lines. Some virus particles were also detected in the nucleus of infected GSSC cells. Both cell lines are able to support replication of ADRV and can therefore be used to investigate amphibian ranaviruses.

Clinical signs, pathology and dose-dependent survival of adult wood frogs, Rana sylvatica, inoculated orally with frog virus 3 Ranavirus sp., Iridoviridae.

Amphibian populations suffer massive mortalities from infection with frog virus 3 FV3, genus Ranavirus, family Iridoviridae, a pathogen also involved in mortalities of fish and reptiles. Experimental oral infection with FV3 in captive-raised adult wood frogs, Rana sylvatica Lithobates sylvaticus, was performed as the first step in establishing a native North American animal model of ranaviral disease to study pathogenesis and host response. Oral dosing was successful LD50 was 10(2.93 2.423.44) p.f.u. for frogs averaging 35mm in length. Onset of clinical signs occurred 614days post-infection p.i. median 11 days p.i. and time to death was 1014 days p.i. median 12 days p.i.. Each tenfold increase in virus dose increased the odds of dying by 23-fold and accelerated onset of clinical signs and death by approximately 15. Ranavirus DNA was demonstrated in skin and liver of all frogs that died or were euthanized because of severe clinical signs. Shedding of virus occurred in faeces 710 days p.i. 34.5days before death and skin sheds 10 days p.i. 01.5days before death of some frogs dead from infection. Most common lesions were dermal erosion and haemorrhages haematopoietic necrosis in bone marrow, kidney, spleen and liver and necrosis in renal glomeruli, tongue, gastrointestinal tract and urinary bladder mucosa. Presence of ranavirus in lesions was confirmed by immunohistochemistry. Intracytoplasmic inclusion bodies probably viral were present in the bone marrow and the epithelia of the oral cavity, gastrointestinal tract, renal tubules and urinary bladder. Our work describes a ranaviruswood frog model and provides estimates that can be incorporated into ranavirus disease ecology models.

Does Teno Torque Virus Induce Autoimmunity After Hematopoietic Stem Cell Transplantation? A Case Report.

Teno Torque virus, member of the family of Anelloviridae, has been associated with many autoimmune diseases such as idiopathic hepatitis, systemic lupus erythematosus, and multiple sclerosis. Its viral load tends to be higher in the bone marrow and in tissues with high turnover rate. We report here a case of an 11-month-old infant affected by acute myeloid leukemia who underwent hematopoietic stem cell transplantation, and after 6 months had autoimmune hepatitis and atopic dermatitis. Extremely high-cytokine IP-10 and eotaxin levels were found in her sera, and serological tests and RT-PCR for viruses showed positive results exclusively for Teno Torque virus.

[GENUS ANELLOVIRIDAE VIRUSES IN CHRONIC LIVER DISEASE].

AIM: Viruses from genus Anelloviridae (TTV, TTMDV and TTMV) are small DNA viruses that are widespread in human popu- lation. Data on tissue tropism, cell localization and morphometry of anelloviruses are scarce. The purpose of this study was to determine the prevalence of TTV, TTMDV and TTMV in persons with liver disease and in healthy individuals, as well as electron-microscopic verification of Anelloviridae species. METHODS: Detection of anelloviral DNA was performed in serum samples from 203 patients with liver diseases of various etiology and 115 voluntary blood donors using PCR with primers allowing to differentiate TTV, TTMDV TTMV based on the length of amplified fragment. Histopathological and electron microscopic studies were performed for liver biopsy specimens from 203 patients with liver disease. RESULTS: High prevalence (70-90%) of all three anelloviruses in healthy individuals and patients with liver disease was demonstrated, with high frequency of triple TTV, TTMDV and TTMV infection (52.2-55.7%). Electron-microscopic study of liver biopsy specimens from TTMDV monoinfected patients gave a submicroscopic image of TTMDV virions with diameter 35.86 ± 2.04 nm. Electron microscopic studies confirmed the nature of liver damage in TTMDV monoinfection: accumulation of virus in the hepatocytes, significant cyropathy with enlightenment matrix of the cytoplasm and reduction of intracellula organelles involved in protein synthesis, portal and perivascular perisinusoidal fibrosis. TTV, TTMDV and TTMV virions were dentified in hepatocytes, confirming these viruses to be hepatotropic. CONCLUSION: Our results demonstrate that anelloviruses are lymphotropic viruses, individual genotypes of those might be hepatotropic and pathogenic to liver.

TLR9 transcriptional regulation in response to double-stranded DNA viruses.

The stimulation of TLRs by pathogen-derived molecules leads to the production of proinflammatory cytokines. Because uncontrolled inflammation can be life threatening, TLR regulation is important; however, few studies have identified the signaling pathways that contribute to the modulation of TLR expression. In this study, we examined the relationship between activation and the transcriptional regulation of TLR9. We demonstrate that infection of primary human epithelial cells, B cells, and plasmacytoid dendritic cells with dsDNA viruses induces a regulatory temporary negative-feedback loop that blocks TLR9 transcription and function. TLR9 transcriptional downregulation was dependent on TLR9 signaling and was not induced by TLR5 or other NF-κB activators, such as TNF-α. Engagement of the TLR9 receptor induced the recruitment of a suppressive complex, consisting of NF-κBp65 and HDAC3, to an NF-κB cis element on the TLR9 promoter. Knockdown of HDAC3 blocked the transient suppression in which TLR9 function was restored. These results provide a framework for understanding the complex pathways involved in transcriptional regulation of TLR9, immune induction, and inflammation against viruses.