Histopathological and immunohistochemical studies of hepatitis A virus infection in marmoset Callithrix jacchus

Utility of Common Marmoset (Callithrix jacchus) Embryonic Stem Cells in Liver Disease Modeling, Tissue Engineering and Drug Metabolism

The incidence of liver disease is increasing significantly worldwide and, as a result, there is a pressing need to develop new technologies and applications for end-stage liver diseases. For many of them, orthotopic liver transplantation is the only viable therapeutic option. Stem cells that are capable of differentiating into all liver cell types and could closely mimic human liver disease are extremely valuable for disease modeling, tissue regeneration and repair, and for drug metabolism studies to develop novel therapeutic treatments. Despite the extensive research efforts, positive results from rodent models have not translated meaningfully into realistic preclinical models and therapies. The common marmoset Callithrix jacchus has emerged as a viable non-human primate model to study various human diseases because of its distinct features and close physiologic, genetic and metabolic similarities to humans. C. jacchus embryonic stem cells (cjESC) and recently generated cjESC-derived hepatocyte-like cells (cjESC-HLCs) could fill the gaps in disease modeling, liver regeneration and metabolic studies. They are extremely useful for cell therapy to regenerate and repair damaged liver tissues in vivo as they could efficiently engraft into the liver parenchyma. For in vitro studies, they would be advantageous for drug design and metabolism in developing novel drugs and cell-based therapies. Specifically, they express both phase I and II metabolic enzymes that share similar substrate specificities, inhibition and induction characteristics, and drug metabolism as their human counterparts. In addition, cjESCs and cjESC-HLCs are advantageous for investigations on emerging research areas, including blastocyst complementation to generate entire livers, and bioengineering of discarded livers to regenerate whole livers for transplantation.

Comparative Pathology of Hepatitis A Virus and Hepatitis E Virus Infection

Hepatitis A virus (HAV) and hepatitis E virus (HEV) cause acute, self-limiting hepatic infections that are usually spread by the fecal-oral route in humans. Naturally occurring and experimental infections are possible in a variety of nonhuman primates and, in the case of HEV, a number of other species. Many advances in understanding the pathogenesis of these viruses have come from studies in experimental animals. In general, animals infected with these viruses recapitulate the histologic lesions seen in infected humans, but typically with less severe clinical and histopathological manifestations. This review describes the histopathologic changes associated with HAV and HEV infection in humans and experimental animals.

A novel hepatovirus identified in wild woodchuck Marmota himalayana

Hepatitis A virus (HAV) is a hepatotropic picornavirus that causes acute liver disease worldwide. Here, we report on the identification of a novel hepatovirus tentatively named Marmota Himalayana hepatovirus (MHHAV) in wild woodchucks (Marmota Himalayana) in China. The genomic and molecular characterization of MHHAV indicated that it is most closely related genetically to HAV. MHHAV has wide tissue distribution but shows tropism for the liver. The virus is morphologically and structurally similar to HAV. The pattern of its codon usage bias is also consistent with that of HAV. Phylogenetic analysis indicated that MHHAV groups with known HAVs but forms an independent branch, and represents a new species in the genus Hepatovirus within the family Picornaviridae. Antigenic site analysis suggested MHHAV has a new antigenic property to other HAVs. Further evolutionary analysis of MHHAV and primate HAVs led to a most recent common ancestor estimate of 1,000 years ago, while the common ancestor of all HAV-related viruses including phopivirus can be traced back to 1800 years ago. The discovery of MHHAV may provide new insights into the origin and evolution of HAV and a model system with which to explore the pathogenesis of HAV infection.

Anti-duck virus hepatitis mechanisms of Bush Sophora Root polysaccharide and its sulfate verified by intervention experiments

In our previous study, Bush Sophora Root polysaccharide (BSRPS) and its sulfate (sBSRPS) exhibited anti-duck virus hepatitis (DVH) abilities as well as anti-oxidative and immuno-enhancement effects. The aim of this paper was to ulteriorly investigate the exact anti-DVH mechanisms of BSRPS and sBSRPS by intervention experiments. Hinokitiol and FK506 were used as the pro-oxidant and immunosuppressant, respectively. The dynamic deaths, oxidative and immune evaluation indexes and hepatic pathological change scores were detected. When was intervened by hinokitiol, sBSRPS still possessed therapeutic effect while BSPRS was useless. Under the condition of immunosuppression, BSRPS lost a part role in treating DVH; however such a role of sBSRPS completely exhausted. These results suggested both anti-oxidative and immuno-enhancement effects of BSRPS played roles in healing DVH, and the former was more crucial; unlike BSRPS, only immuno-enhancement ability of sBSRPS was imperative for its curative effect on DVH.

Animal Models of Human Viral Diseases

As the threat of exposure to emerging and reemerging viruses within a naive population increases, it is vital that the basic mechanisms of pathogenesis and immune response be thoroughly investigated. By using animal models in this endeavor, the response to viruses can be studied in a more natural context to identify novel drug targets, and assess the efficacy and safety of new products. This is especially true in the advent of the Food and Drug Administration's animal rule. Although no one animal model is able to recapitulate all the aspects of human disease, understanding the current limitations allows for a more targeted experimental design. Important facets to be considered before an animal study are the route of challenge, species of animals, biomarkers of disease, and a humane endpoint. This chapter covers the current animal models for medically important human viruses, and demonstrates where the gaps in knowledge exist.

Experimental hepatitis A virus (HAV) infection in cynomolgus monkeys (Macaca fascicularis): evidence of active extrahepatic site of HAV replication

This work studied the replication sites of hepatitis A virus (HAV) in cynomolgus monkeys (Macaca fascicularis) after intravenous inoculation. The cynomolgus monkeys were inoculated with the Brazilian hepatitis A virus strain (HAF-203). Monkeys were euthanized on days 15, 30, 45 and 60 postinoculation (pi). Liver samples, submandibular salivary gland, mesenteric lymph node and tonsils were removed for virological and pathological evaluation. Immunofluorescence analyses on liver and salivary gland sections using confocal laser scanning microscopy revealed the presence of HAV antigen (HAV Ag). The presence of HAV genome was monitored by real-time PCR. The HAV RNA was detected at 7 days postinoculation (dpi), concomitantly in serum, saliva and faeces. The highest HAV viral load was observed in faeces at 15 dpi (10(5) copies/ml), followed by serum viral load of 10(4) copies/ml at 20 dpi and saliva viral load of 10(3 )copies/ml at 7 dpi. The animals showed first histological and biochemical signs of hepatitis at 15 dpi. The HAV antigen (Ag) was present from day 7 until day 60 pi in the liver and salivary glands. The HAV replicative intermediate was also detected in the liver (4.5 x 10(4) copies/mg), salivary glands (1.9 x 10(3) copies/mg), tonsils (4.2 x 10(1) copies/mg) and lymph nodes (3.4 x 10(1) copies/mg). Our data demonstrated that the salivary gland as an extrahepatic site of early HAV replication could create a potential risk of saliva transmitted infection. In addition, the cynomolgus monkey was confirmed as a suitable model to study the pathogenesis of HAV human infection.

Experimental hepatitis A virus (HAV) infection in Callithrix jacchus: early detection of HAV antigen and viral fate

Common marmosets (Callithrixjacchus) were orally inoculated with a Brazilian strain (HAF-203) of hepatitis A virus (HAy). Three monkeys were euthanized at postinoculation hours 6, 12 and 24 to investigate the early events of HAV infection. Following others three inoculated and one control marmosets remained throughout the 46 day to evaluation of viral excretion. Different samples were collected to detect sequential presence of HAV RNA by nested reverse transcription-polymerase chain reaction (RT-PCR) in liver, saliva, bile and stools at 6 hours to 461h days postinoculation. Liver tissues were examined by immunofluorescence assay in a confocal laser-scanning microscope for the presence of HAV antigen. HAV RNA was detected in saliva during the course of the study, in bile from 24 hours to 46 days. in stools from 7 to 46 days and liver at 12 hours postinfection. In immunofluorescence of liver stained preparations, viral antigen was present at six hours after inoculation throughout the remainder of the 46-day study. The animals developed histological and biochemical acute hepatitis after second week postinoculation. Spleen, duodenum, and mesenteric lymph nodes specimens were negative for HAV antigens. This study supports the possibility that in Callithrixjacchus orally inoculated with hepatitis A virus the saliva route may be additional way of viral elimination. The viral replication in the liver was responsible for biliary HAV presence and latter HAV detection in fecal samples.

Experimental hepatitis A virus infection in guinea pigs

Although many of the properties of hepatitis A virus (HAV) are known, several aspects of HAV pathogenesis are still not understood, such as the mechanism underlying the hepatotropism or HAV replication in extrahepatic sites. Detailed studies of these aspects were hampered mostly by the lack of accessible animal models, since only nonhuman primates are susceptible to experimental infections. An alternative animal model would also be of interest to assess the primary replication site and for the evaluation of the safety and efficacy of vaccines. A study was undertaken to determine whether HAV can infect guinea pigs and whether they are useful as a model for studying aspects of HAV pathogenesis and for the evaluation of vaccines. HAV variants adapted to primate or guinea pig tissue culture were used to inoculate guinea pigs intraperitoneally and by the oral route. The animals were observed for clinical disease, shedding of HAV in stools, viremia, seroconversion, evidence for liver damage by biochemical liver function tests, virus presence in the liver, development of hepatic histopathological changes, and occurrence of HAV in extrahepatic organs. The animals developed an active, clinically inapparent infection with specific histopathological changes in the liver. Although virus replication occurred, as shown by RT-PCR and isolation of infectious virus from feces and serum, it seems unlikely that guinea pigs are suitable for studying the clinical features of hepatitis A, because the clinical and laboratory parameters remained normal. However, guinea pigs appear useful for studying some aspects of HAV pathogenesis and for testing the safety of vaccines.

Animal models of hepatitis A and E

Several useful animal models for both hepatitis A and E have been identified, characterized, and refined. At present, all of the best models utilize nonhuman primates: chimpanzees, tamarin species, and owl monkeys for hepatitis A; and macaque species, chimpanzees, and owl monkeys for hepatitis E. Pigs may prove useful for some studies of hepatitis E, and it is hoped that serological evidence of widespread infection of rats with an HEV-like agent may lead to the development of an animal model based on laboratory rats. As has been the case for each of the hepatitis viruses as they have been discovered, the development of useful and reproducible animal model systems has been critical for moving the field forward as expeditiously as possible.

Inducible nitric oxide synthase (iNOS) expression in liver and splenic T lymphocyte rise are associated with liver histological damage during experimental hepatitis A virus (HAV) infection in Callithrix jacchus

Callithrix jacchus is considered a reliable animal model for hepatitis A virus (HAV) infection. All three HAV orally inoculated marmosets developed hepatitis - the infection was monitored by continuous virus shedding, high levels of serum enzyme alanine aminotransferase, specific antibody and seroconversion 3-6 weeks after HAV inoculation. HAV antigen was detected in liver by immunofluorescence 4 days post inoculation (PI) and onwards. To gain insight into the biological role of inducible nitric oxide synthase (iNOS) during immune-related acute liver injury the enzyme was searched in frozen biopsies: immunofluorescent labeling was found in the cytoplasm of liver cells mainly Kupffer's cells and spleen macrophages (CD68+) starting 11 days PI with maximum intensity on the fifth to sixth week PI. Necroinflammatory liver lesions characteristic of viral hepatitis were also observed at 10 days PI with maximum severity at 4 to 6 weeks PI. Furthermore, T lymphocytes (CD2+) were raised at this time point. No difference was evident in the frequency of B lymphocytes (CD20+). Therefore, iNOS expression preceded necroinflammatory liver lesion and maximal immunofluorescence reaction was coincident with tissue injury, supporting the hypothesis that NO contributes to hepatic cytotoxic mechanism but also to virus clearance. The concomitant rise in T-lymphocyte population may suggest a role for these cells in this and/or other independent HAV-induced pathological changes.

The use of non-human primates as animal models for the study of hepatitis viruses

Hepatitis viruses belong to different families and have in common a striking hepatotropism and restrictions for propagation in cell culture. The transmissibility of hepatitis is in great part limited to non-human primates. Enterically transmitted hepatitis viruses (hepatitis A virus and hepatitis E virus) can induce hepatitis in a number of Old World and New World monkey species, while the host range of non-human primates susceptible to hepatitis viruses transmitted by the parenteral route (hepatitis B virus, hepatitis C virus and hepatitis delta virus) is restricted to few species of Old World monkeys, especially the chimpanzee. Experimental studies on non-human primates have provided an invaluable source of information regarding the biology and pathogenesis of these viruses, and represent a still indispensable tool for vaccine and drug testing.