Surrogate Biomarkers of Disease Progression in Human Pegivirus Seropositive Human Immunodeficiency Virus-Infected Individuals.

Scientific observations indicate that an actively prevailing systemic condition could alleviate the pathology of another disease. Human pegivirus (HPgV), a highly ubiquitous flavivirus is believed to be associated with slow human immunodeficiency virus (HIV) disease progression, and has seldom been linked to hepatic pathology. In this study, we investigated whether HPgV seropositivity had any impact on surrogate markers of HIV disease progression in a cohort of HIV-infected HPgV seropositive (n = 28) and seronegative (n = 12) individuals who were prospectively evaluated for absolute CD4+ T cell counts, plasma viral load (PVL), liver enzymes, and plasma cytokine levels. The HIV PVL was relatively lower in HPgV seropositive than in HPgV seronegative HIV-infected subjects. Clinical markers of hepatic injury were significantly low among HPgV seropositive HIV-infected participants. HPgV seropositive individuals showed significantly higher levels of interleukin-7 (IL-7), and although not significant, the levels of IL-6 were lower among HPgV seropositive subjects. Spearman correlation analysis showed that the absolute CD4+T cell count was inversely correlated with HIV PVL. Exposure to HPgV appears to have a positive prognostic impact on the levels of surrogate biomarkers of HIV disease progression.

Flaviviridae Viruses and Oxidative Stress: Implications for Viral Pathogenesis.

Oxidative stress is induced once the balance of generation and neutralization of reactive oxygen species (ROS) is broken in the cell, and it plays crucial roles in a variety of natural and diseased processes. Infections of Flaviviridae viruses trigger oxidative stress, which affects both the cellular metabolism and the life cycle of the viruses. Oxidative stress associated with specific viral proteins, experimental culture systems, and patient infections, as well as its correlations with the viral pathogenesis attracts much research attention. In this review, we primarily focus on hepatitis C virus (HCV), dengue virus (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and tick-borne encephalitis virus (TBEV) as representatives of Flaviviridae viruses and we summarize the mechanisms involved in the relevance of oxidative stress for virus-associated pathogenesis. We discuss the current understanding of the pathogenic mechanisms of oxidative stress induced by Flaviviridae viruses and highlight the relevance of autophagy and DNA damage in the life cycle of viruses. Understanding the crosstalk between viral infection and oxidative stress-induced molecular events may offer new avenues for antiviral therapeutics.

First description of Theiler's disease-associated virus infection and epidemiological investigation of equine pegivirus and equine hepacivirus coinfection in Brazil.

Recent advances in the study of equine pegivirus (EPgV), Theiler's disease-associated virus (TDAV) and equine hepacivirus (EqHV) highlight their importance to veterinary and human health. To gain some insight into virus distribution, possible risk factors, presence of liver damage and genetic variability of these viruses in Brazil, we performed a cross-sectional study of EPgV and TDAV infections using a simultaneous detection assay, and assessed EqHV coinfection in different horse cohorts. Of the 500 serum samples screened, TDAV, EPgV and EPgV-EqHV were present in 1.6%, 14.2% and 18.3%, respectively. EPgV-positive horses were present in four Brazilian states: Espírito Santo, Mato Grosso do Sul, Minas Gerais and Rio de Janeiro. Serum biochemical alterations were present in 40.4% of EPgV-infected horses, two of them presenting current liver injury. Chance of infection was 2.7 times higher in horses ≤5 years old (p = 0.0008) and 4.9 times higher in horses raised under intensive production systems (p = 0.0009). EPgV-EqHV coinfection was 75% less likely in horses older than 5 years comparatively to those with ≤5 years old (p = 0.047). TDAV-positive animals were detected in different horse categories without biochemical alteration. Nucleotide sequences were highly conserved among isolates from this study and previous field and commercial product isolates (≥88% identity). Tree topology revealed the formation of two clades (pp = 1) for both EPgV and TDAV NS3 partial sequences. In conclusion, the widespread presence of EPgV-RNA suggests an enzootic infection with subclinical viremia in Brazil. Horse management can influence virus spread. This first report of TDAV-infected horses outside the USA reveals the existence of subclinical viremic horses in distant geographical regions. EPgV and TDAV have similar circulating isolates worldwide. These findings contribute to global efforts to understand the epidemiology and pathogenesis of these equine viruses.

Hepatic immunopathology during occult hepacivirus re-infection.

Despite drug advances for Hepatitis C virus (HCV), re-infections remain prevalent in high-risk populations. Unfortunately, the role of preexisting viral immunity and how it modulates re-infection is unclear. GBV-B infection of common marmosets is a useful model to study tissue immune responses in hepacivirus infections, and in this study we re-challenged 4 animals after clearance of primary viremia. Although only low-to-absent viremia was observed following re-challenge, GBV-B viral RNA was detectable in liver, confirming re-infection. Microscopic hepatic lesions indicated severe-to-mild lymphocyte infiltration and fibrosis in 3 out of 4 animals. Further, GBV-B-specific T cells were elevated in animals with moderate-to-severe hepatopathology, and up to 3-fold increases in myeloid dendritic and activated natural killer cells were observed after infection. Our data indicate that occult hepacivirus re-infections occur and that new liver pathology is possible even in the presence of anti-hepacivirus T cells and in the absence of high viremia.

Prevalence and Clinical Impact of Human Pegivirus-1 Infection in HIV-1-Infected Individuals in Yunnan, China.

Human Pegivirus-1 (HPgV-1) may have a beneficial impact on disease progression in human immunodeficiency virus-1 (HIV-1) infection. However, analysis of the genotypic diversity of HPgV-1 and its relevance to the progression of HIV-1 disease remains limited. A total of 1062 HIV-1-infected individuals were recruited in all sixteen prefectures of Yunnan province, China. The reverse transcription nested polymerase chain reaction (RT-nPCR), phylogenetic analyses, and clinical data analyses were used to detect HPgV-1 infection, determine genotype, and analyze HPgV-1 genotype impact on HIV-1 disease progression. The overall positive rate of HPgV-1 RNA was 23.4% (248/1062), and the frequency of HPgV-1 infection in injecting drug users (IDUs) (28.5%, 131/460) was significantly higher than in heterosexuals (19.4%, 117/602). Multiple genotypes were identified in 212 subjects with successful sequencing for the E2 gene, including genotype 7 (55.7%), genotype 3 (34.9%), genotype 4 (4.7%), genotype 2 (3.3%), and an unclassified group (1.4%). Moreover, genotype 7 predominated in IDUs, whereas genotype 3 was the most common in heterosexuals. Our results revealed that HPgV-1 genotype 7 groups exhibited significantly lower HIV-1 viral load and higher CD4⁺ cell counts. This finding suggests that HPgV-1 genotype 7 may be associated with a better progression of HIV-1 disease.

Flaviviruses.

What do Zika, Dengue and West Nile viruses have in common? All are members of a family of viruses called the Flaviviruses. Here, Sonja Best lays out the essentials of this group of significant human pathogens.

The effect of Tembusu virus infection in different week-old Cherry Valley breeding ducks.

To study the effect of Tembusu virus (TMUV) infection on Cherry Valley Breeding ducks of different ages, 350 five-week-old ducks were divided into 14 groups. Ducks in seven experimental group were respectively infected with 1.265×10(5) mean embryo lethal dose (ELD50) of TMUV-AHQY strain (in 4.2mL) by intravenous route. Ducks in control groups were inoculated with Phosphate-buffered Saline (PBS) in the same way. Clinical symptoms, gross and microscopic lesions, viral loads and serum antibodies were detected and recorded for 20days after infection. Some ducks infected at 7 and 21 week s of age showed severe clinical symptoms including depression and inappetence, and no obvious clinical symptoms were seen in other week-old infected ducks. Severe gross lesions including hepatomegaly, meningeal congestion, myocardial hemorrhage, intestinal, myocardial and pulmonary edema were observed in ducks infected at 7, 18 and 21 weeks of age. No or mild gross lesions were observed in ducks infected at 14 and 16 weeks of age. The main microscopic lesions including hyperaemia, degeneration and necrosis of different cells and inflammatory cellular infiltration mainly consisting of mononuclear cells or lymphocytes were observed in ducks infected at 7 and 21 week of age. But relatively intact structures and rare lymphocytic infiltration were presented in ducks infected at 14 and 16 weeks of age. Viral antigen was more frequently observed in organ slices collected from 7 week-old infected ducks and few positive staining was found in 14 and 16 week-old infected ducks. Less viral loads in different tissues and swabs were detected by a quantitative real-time PCR assay. The level of viral loads in the tissues of ducks infected at 14 and 16 weeks of age was very lower than that of ducks infected at 7 and 21 weeks of age. Meanwhile, less viral copy numbers were detected in swab samples collected from 14 and 16 week-old infected ducks. Ducks infected at 14-week-old developed significantly higher serum neutralizing antibody titers than those infected at other week of age. These results indicated that the effect of TMUV infection on Cherry Valley ducks is partly related to weeks of age. 7-10 week-old and 18-21 week-old ducks were more susceptible to TMUV infection, but 14-16 week-old ducks were more resistant to this disease.

Infection of Common Marmosets with GB Virus B Chimeric Virus Encoding the Major Nonstructural Proteins NS2 to NS4A of Hepatitis C Virus.

UNLABELLED: A lack of immunocompetent-small-primate models has been an obstacle for developing hepatitis C virus (HCV) vaccines and affordable antiviral drugs. In this study, HCV/GB virus B (GBV-B) chimeric virus carrying the major nonstructural proteins NS2 to NS4A (HCV NS2 to -4A chimera) was produced and used to infect common marmosets, since HCV NS2 to NS4A proteins are critical proteases and major antigens. Seven marmosets were inoculated intrahepatically with HCV NS2 to -4A chimera RNA for primary infection or intravenously injected with chimera-containing serum for passage infection. Three animals used as controls were injected with phosphate-buffered saline (PBS) or GBV-B, respectively. Six of seven HCV NS2 to -4A chimera-infected marmosets exhibited consistent viremia and one showed transient viremia during the course of follow-up detection. All six infected animals with persistent circulating viremia presented characteristics typical of viral hepatitis, including viral RNA and proteins in hepatocytes and histopathological changes in liver tissue. Viremia was consistently detected for 5 to 54 weeks of follow-up. FK506 immunosuppression facilitated the establishment of persistent chimera infection in marmosets. An animal with chimera infection spontaneously cleared the virus in blood 7 weeks following the first inoculation, but viral-RNA persistence, low-level viral protein, and mild necroinflammation remained in liver tissue. The specific antibody and T-cell response to HCV NS3 in this viremia-resolved marmoset was boosted by rechallenging, but no viremia was detected during 57 weeks of follow-up. The chimera-infected marmosets described can be used as a suitable small-primate animal model for studying novel antiviral drugs and T-cell-based vaccines against HCV infection. IMPORTANCE: HCV infection causes approximately 70% of chronic hepatitis and is frequently associated with primary liver cancer globally. Chimpanzees have been used as a reliable primate model for HCV infection, but ethical considerations have restricted their utility in biomedical research. GB virus B (GBV-B) is a flavivirus related to HCV. It can infect common marmosets, a New World small primate, and induces viral hepatitis similar to HCV infection in humans. To minimize differences between GBV-B and HCV, we generated HCV NS2 to -4A/GBV-B chimeric viruses and established a chimera-infected marmoset model. HCV NS2 to -4A chimera-infected marmosets provide a small-animal model for evaluating novel antiviral drugs targeting HCV NS3-NS4A protease and T-cell-based HCV vaccines.

IL-33 signaling is essential to attenuate viral-induced encephalitis development by downregulating iNOS expression in the central nervous system.

BACKGROUND: Viral encephalitis is a common cause of lethal infections in humans, and several different viruses are documented to be responsible. Rocio virus is a flavivirus that causes a severe lethal encephalitis syndrome in humans and also mice, providing an interesting model to study the CNS compartmentalized immune response. Interleukin 33 (IL-33), a member of the IL-1 family, is an immunomodulatory cytokine that is highly expressed in the CNS. However, the role of IL-33 on viral encephalitis remains unclear. Therefore, we aimed to explore how the IL-33/ST2 axis regulates the local immune response during Rocio virus infection. METHODS: Wild-type (WT), ST2 (ST2(-/-)), and nitric oxide synthase-deficient mice (iNOS(-/-)) and Stat6 (Stat6(-/-))-deficient mice were infected with different concentrations of the Rocio virus by intraperitoneal route, the cytokine mRNA level in CNS was analyzed by qPCR, and cellular immunophenotyping was performed on infected mice by the flow cytometry of isolated CNS mononuclear cells. RESULTS: We have shown that the mRNA expression of IL-33 and ST2 receptors is increased in the CNS of Rocio virus-infected WT mice and that ST2(-/-) mice showed increased susceptibility to infection. ST2 deficiency was correlated with increased tissue pathology, cellular infiltration, and tumor necrosis factor alpha (TNF-α) and interferon-gamma (IFN-γ) mRNA levels and higher viral load in the CNS, compared with wild-type mice. The increased Th1 cytokine levels released in the CNS acted on infiltrating macrophages, as evidenced by flow cytometry characterization of cellular infiltrates, inducing the expression of iNOS, contributing to brain injury. Moreover, iNOS(-/-) mice were more resistant to Rocio virus encephalitis, presenting a lower clinical score and reduced mortality rate, despite the increased tissue pathology. CONCLUSIONS: We provide evidences of a specific role for IL-33 receptor signaling in nitric oxide induction through local IFN-γ modulation, suggesting that nitric oxide overproduction might have an important role in the progression of experimental viral encephalitis.

Human Pegivirus (HPgV; formerly known as GBV-C) inhibits IL-12 dependent natural killer cell function.

Human Pegivirus (HPgV, formally GB virus C) infects lymphocytes and NK cells in vivo, and infection is associated with reduced T cell and NK cell activation in HIV-infected individuals. The mechanism by which HPgV inhibits NK cell activation has not been assessed. Following IL-12 stimulation, IFNγ expression was lower in HIV-HPgV co-infected subjects compared to HIV mono-infected subjects (p=0.02). In addition, HPgV positive human sera, extracellular vesicles containing E2 protein, recombinant E2 protein and synthetic E2 peptides containing a predicted Tyk2 interacting motif inhibited NK cell IL-12-mediated IFNγ release. E2 protein also inhibited Tyk2 activation following IL-12 stimulation. In contrast, cytolytic NK cell function was not altered by HPgV. Inhibition of NK cell-induced proinflammatory/antiviral cytokines may contribute to both HPgV persistence and reduced immune activation during HIV-coinfection. Understanding mechanisms by which HPgV alters immune activation may contribute towards novel immunomodulatory therapies to treat HIV and inflammatory diseases.

GB virus C infection and B-cell, natural killer cell, and monocyte activation markers in HIV-infected individuals.

GB virus C (GBV-C), a pan-lymphotropic flavivirus capable of persistent infection, is associated with prolonged survival and reduced T-cell activation in HIV-infected patients. GBV-C was associated with reduced CD56brt/CD16- natural killer cell and monocyte activation, and a trend toward reduced B-cell activation by measuring cell surface activation markers or HIV entry coreceptors. The GBV-C association was independent of HIV viral load. Thus, GBV-C may influence non-T-cell immune activation in individuals with HIV infection.

Adapted Tembusu-like virus in chickens and geese in China.

An outbreak of egg drop disease occurred in many chicken and goose farms in China in 2011. By using an NS5-specific reverse transcriptase PCR (RT-PCR), we found that 56% of chicken and 38% of goose samples were positive for Tembusu-like virus (TMUV). Isolates showed high sequence homology to duck TMUVs, and chickens and geese showed signs of egg drop disease after experimental infection with duck TMUV. Our data suggest TMUV has adapted in domestic birds.

An experimental model of meningoencephalomyelitis by Rocio flavivirus in BALB/c mice: inflammatory response, cytokine production, and histopathology.

Rocio virus (ROCV) is a flavivirus, probably transmitted by Culex mosquitoes and maintained in nature as a zoonosis of wild birds. Rocio virus caused a human epidemic of severe encephalitis that lasted from 1973 to 1980 in the Ribeira valley, in the southeastern coast of Brazil. After this outbreak, serologic evidence of ROCV circulation has been reported and public health authorities are concerned about a return of ROCV outbreaks in Brazil. We show here a study on the pathogenesis and the physiopathology of ROCV disease in the central nervous system of a Balb/C young adult mice experimental model. The animals were intraperitoneally infected by ROCV and followed from 0 to 9 days after infection, when all of them died. Nervous tissue samples were collected from infected animals for immunohistochemistry and molecular biology analysis. We observed the virus in the central nervous system, the inflammatory changes induced by Th1 and Th2 cytokines, and the final irreversible damage of nervous tissues by neuronal degeneration and apoptosis. These findings can help to better understand the pathogenesis and physiopathology of the human meningoencephalomyelitis by ROCV and other flaviviruses.

Hepatitis G virus associated aplastic anemia: a recent case from Pakistan.

BACKGROUND: Aplastic anemia (AA) is a serious and rare disorder characterized by a hypocellular bone marrow. Hepatitis associated aplastic anemia (HAAA) is a variant of aplastic anemia in which aplastic anemia follows an acute attack of hepatitis. Several reports have noted an association between HGV and hepatitis-associated aplastic anemia besides other hepatitis causing viruses. CASE PRESENTATION: A female girl of age 11 year with a history of loose motion for one month, vomiting for last 15 days and poor oral intake for last few days is reported here. The physical examination presents fever, pallor whereas bleeding, hepatomegaly, Splenomegaly and bruising were absent, abdominal ultrasonography confirmed the absence of hepatomegaly, Splenomegaly and lymphodenopathy. The laboratory investigation parameters were: haemoglobin 6.2 g/L, total leucocytes count 1.51, neutrophils 0.47%, absolute reticulocyte count 0.5%, Monocytes 0.16%, red cell count 3.2 mil/uL, Picked cell volume (PCV) 30.13%, Mean Corpuscular Volume (MCV) 78 fL, Mean Corpuscular Hemoglobin (MCH) 26.3 pg. The liver enzymes were alanine aminotransferease (ALT) 98 IU/L, aspartate aminotransferase (AST) 114 IU/L. Serologic and molecular tests for hepatitis A, B, C, D, E, TTV, B19 were negative, whereas HGV RNA PCR test was found positive for hepatitis G virus. The bone marrow aspirate and trephine biopsy examination revealed hypo- cellularity, erythropoiesis, myelopoiesis and megakaryopoiesis. CONCLUSION: HAAA is an uncommon but severe condition, which may occur following idiopathic cases of acute hepatitis. Our finding suggests the involvement of HGV in the development of aplastic anemia. In patients presenting with pancytopenia after an episode of acute hepatitis, the definitive diagnosis should be considered and confirmed by RT-PCR and if possible by bone marrow biopsy.

The natural history of non-human GB virus C in captive chimpanzees.

GB virus C (GBV-C) is a common, non-pathogenic human virus that infects lymphocytes. Persistent GBV-C infection of humans with coexistent human immunodeficiency virus (HIV) infection is associated with prolonged survival, and GBV-C replication inhibits HIV replication in vitro. A GBV-C virus variant was identified in chimpanzees in 1998 and was named GBV-C(trog) or GBV-C(cpz). The prevalence and natural history of GBV-C in chimpanzees remains uncharacterized. We examined the sera from 235 captive chimpanzees for the presence of GBV-C viraemia, viral persistence and clearance, E2 antibody kinetics and RNA sequence diversity. Sequences from six isolates shared more sequence identity with GBV-C(cpz) than with human GBV-C. The prevalence of GBV-C(cpz) viraemia and E2 antibody in chimpanzees (2.5 and 11 %, respectively) was similar to human GBV-C prevalence in healthy human blood donors (1.8 and 9 %, respectively). Persistent GBV-C(cpz) infection occurred in two of the six viraemic animals and was documented for 19 years in one animal. Host subspecies troglodyte GBV-C isolates and published verus GBV-C isolates shared a high degree of sequence identity, suggesting that GBV-C in chimpanzees should be identified with a chimpanzee designation (GBV-C(cpz)). The prevalence and natural history of chimpanzee GBV-C variant (GBV-C(cpz)) appears to be similar to human GBV-C infection. The chimpanzee could serve as an animal model to study HIV-GBV-C co-infection.

Emergence and establishment of Usutu virus infection in wild and captive avian species in and around Zurich, Switzerland--genomic and pathologic comparison to other central European outbreaks.

In late summer 2006 considerable mortality in wild and captive Passeriformes and Strigiformes was observed in Zurich, Switzerland. All animals were found in a range of 2 km(2). Observed clinical signs involved depression, ruffled plumage, incoordination, seizures and peracute death. Nutritional status was generally moderate to poor in wild birds, and variable in captive animals. Necropsy showed marked splenomegaly, a mild hepatomegaly, and pulmonary hyperemia in most animals. Histopathologic lesions were very discrete and consisted mainly of neuronal necrosis, leucocytolysis in and around the brain blood vessels, and miliary liver necrosis. The diagnosis Usutu virus (USUV) infection was established by USUV-specific immunohistochemistry and reverse transcription-polymerase chain reaction. Partial nucleotide sequence comparisons revealed>99% identity between the viruses that emerged in Zurich in 2006, in Vienna in 2001, and in Budapest in 2005. Since 2008 a significantly lower mortality was observed in wild Passeriformes, but USUV infection was confirmed for the first time beyond Zurich city limits. Indoor housing and regular treatment against ectoparasites are likely to have prevented acute USUV disease in captive Strigiformes. USUV is a mosquito-borne flavivirus causing fatalities in various avian species. After the initial European outbreaks in Austria in 2001 it appears that the virus has extended its range in Central Europe and has established a transmission cycle between local bird and mosquito species. Further episodes of increased avian mortality in the forthcoming years, with impact on wild and captive bird populations, predominantly Passeriformes and Strigiformes, can be anticipated. Furthermore, the possibility of broader dispersal of USUV in Europe during the next mosquito seasons must be considered and an increased mortality in Passeriformes and Strigiformes must be expected until protective "flock immunity" is established. Collections of valuable and endangered Passeriformes and Strigiformes, especially young of the year, should therefore be housed indoors or treated against ectoparasites at acceptable intervals between July and September each year.

Analysis of GB virus C infection among HIV-HCV coinfected patients.

The aim of this study was to evaluate the effect of GB virus C on laboratory markers and histological parameters among HIV-seropositive patients coinfected with HCV. Lower degrees of hepatic lesions were observed in the triple-infected patients, in comparison with HIV-HCV coinfected patients who were negative for GBV-C RNA.

Analysis of GB virus C infection among HIV-HCV coinfected patients / Análise da infecção pelo vírus GB-C em pacientes com coinfecção VIH-VHC

The aim of this study was to evaluate the effect of GB virus C on laboratory markers and histological parameters among HIV-seropositive patients coinfected with HCV. Lower degrees of hepatic lesions were observed in the triple-infected patients, in comparison with HIV-HCV coinfected patients who were negative for GBV-C RNA.

O objetivo do estudo foi avaliar o efeito da infecção pelo vírus GB-C em marcadores laboratoriais e parâmetros histológicos em pacientes HIV soropositivos coinfectados com VHC. Menor grau de lesão hepática foi observado nos pacientes com tripla infecção em comparação aos pacientes coinfectados com VIH-VHC negativos para GBV-C RNA.

Cellular inflammatory response to flaviviruses in the central nervous system of a primate host.

Flaviviruses such as tick-borne encephalitis virus, Japanese encephalitis virus, West Nile virus, and St. Louis encephalitis virus are important neurotropic human pathogens, typically causing a devastating and often fatal neuroinfection. Flaviviruses induce neuroinflammation with typical features of viral encephalitides, including inflammatory cell infiltration, activation of microglia, and neuronal degeneration. Development of safe and effective live-virus vaccines against neurotropic flavivirus infections demands a detailed knowledge of their neuropathogenesis in a primate host that is evolutionarily close to humans. Here, we used computerized morphometric analysis to quantitatively assess the cellular inflammatory responses in the central nervous system (CNS) of rhesus monkeys infected with three antigenically divergent attenuated flaviviruses. The kinetics, spatial pattern, and magnitude of microglial activation, trafficking of T and B cells, and changes in T cell subsets within the CNS define unique phenotypic signatures for each of the three viruses. Our results provide a benchmark for investigation of cellular inflammatory responses induced by attenuated flaviviruses in the CNS of primate hosts and provide insight into the neuropathogenesis of flavivirus encephalitis that might guide the development of safe and effective live-virus vaccines.

Hepatitis G virus genomic RNA is pathogenic to Macaca mulatta.

AIM: To explore the pathogenicity and infectivity of hepatitis G virus (HGV) by observing replication and expression of the virus, as well as the serological and histological changes of Macaca mulatta infected with HGV genomic RNA or HGV RNA-positive serum. METHODS: Full-length HGV cDNA clone (HGVqz) was constructed and proved to be infectious, from which HGV genomic RNA was transcribed in vitro. Macaca mulatta BY1 was intra-hepatically inoculated with HGV genomic RNA, HGV RNA-positive serum from BY1 was intravenously inoculated into Macaca mulatta BM1, and then BB1 was infected with serum from BM1. Serum and liver tissue were taken regularly, and checked with RT-PCR, in situ hybridization and other immunological, serological, histological assays. RESULTS: Serum HGV RNA was detectable in all the 3 Macaca mulattas, serological and histological examinations showed the experimental animals had slightly elevated alanine transaminase (ALT) and developed HGV viremia during the infectious period. The histology, immunohis-tochemistry, and in situ hybridization in liver tissues of the inoculated animals demonstrated a very mild hepatitis with HGV antigen expression in cytoplasm of hepatocytes. RT-PCR and quantitative PCR results showed that HGV could replicate in liver. CONCLUSION: The genomic RNA from full-length HGV cDNA is infectious to the Macaca mulatta and can cause mild hepatitis. HGV RNA-positive serum, from HGV RNA inoculated Macaca mulatta, is infectious to other Macaca mulattas. Macaca mulatta is susceptible to the inoculated HGV, and therefore can be used as an experimental animal model for the studies of HGV infection and pathogenesis.