Experimental HBV and delta infections of chimpanzees: occurrence and significance of intrahepatic immune complexes of HBcAg and delta antigen

Preclinical animal models to evaluate therapeutic antiviral antibodies

Despite the availability of effective preventative vaccines and potent small-molecule antiviral drugs, effective non-toxic prophylactic and therapeutic measures are still lacking for many viruses. The use of monoclonal and polyclonal antibodies in an antiviral context could fill this gap and provide effective virus-specific medical interventions. In order to develop these therapeutic antibodies, preclinical animal models are of utmost importance. Due to the variability in viral pathogenesis, immunity and overall characteristics, the most representative animal model for human viral infection differs between virus species. Therefore, throughout the years researchers sought to find the ideal preclinical animal model for each virus. The most used animal models in preclinical research include rodents (mice, ferrets, …) and non-human primates (macaques, chimpanzee, ….). Currently, antibodies are tested for antiviral efficacy against a variety of viruses including different hepatitis viruses, human immunodeficiency virus (HIV), influenza viruses, respiratory syncytial virus (RSV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and rabies virus. This review provides an overview of the current knowledge about the preclinical animal models that are used for the evaluation of therapeutic antibodies for the abovementioned viruses.

Genetic diversity and worldwide distribution of the deltavirus genus: A study of 2,152 clinical strains

Hepatitis delta virus (HDV) is responsible for the most severe form of acute and chronic viral hepatitis. We previously proposed that the Deltavirus genus is composed of eight major clades. However, few sequences were available to confirm this classification. Moreover, little is known about the structural and functional consequences of HDV variability. One practical consequence is the failure of most quantification assays to properly detect or quantify plasmatic HDV RNA. Between 2001 and 2014, 2,152 HDV strains were prospectively collected and genotyped in our reference laboratory by means of nucleotide sequencing and extensive phylogenetic analyses of a 400-nucleotide region of the genome (R0) from nucleotides 889 to 1289 encompassing the 3' end of the delta protein-coding gene. In addition, the full-length genome sequence was generated for 116 strains selected from the different clusters, allowing for in-depth characterization of the HDV genotypes and subgenotypes. This study confirms that the HDV genus is composed of eight genotypes (HDV-1 to HDV-8) defined by an intergenotype similarity >85% or >80%, according to the partial or full-length genome sequence, respectively. Furthermore, genotypes can be segregated into two to four subgenotypes, characterized by an intersubgenotype similarity >90% (>84% for HDV-1) over the whole genome sequence. Systematic analysis of genome and protein sequences revealed highly conserved functional nucleotide and amino acid motifs and positions across all (sub)genotypes, indicating strong conservatory constraints on the structure and function of the genome and the protein.

CONCLUSION

This study provides insight into the genetic diversity of HDV and a clear view of its geographical localization and allows speculation as to the worldwide spread of the virus, very likely from an initial African origin. (Hepatology 2017;66:1826-1841).

A historical perspective on the discovery and elucidation of the hepatitis B virus

The discovery in 1965 of the "Australia antigen," subsequently identified as the hepatitis B virus surface antigen (HBsAg), was such a watershed event in virology that it is often thought to mark the beginning of hepatitis research, but it is more accurately seen as a critical breakthrough in a long effort to understand the pathogenesis of infectious hepatitis. A century earlier, Virchow provided an authoritative explanation of "catarrhal jaundice," which did not consider an infectious etiology, but the transmission of jaundice by human serum was clearly identified in two outbreaks in 1885, and the distinction between "infectious" and "serum" hepatitis was recognized by the early 1920s. The inability to culture a virus or reproduce either syndrome in laboratory animals led to numerous studies in human volunteers; by the end of World War II, it was known that the diseases were caused by different filterable agents, and the terms "hepatitis A" and "B" were introduced in 1947 (though some long-incubation cases then designated B must in retrospect have been hepatitis C). The development of a number of liver function tests during the 1950s led to the recognition of anicteric infections and the existence of chronic carriers, but little more could be done until an infectious agent had been identified. Once Blumberg and colleagues had found a specific viral marker, the vast amount of accumulated epidemiologic and clinical data, together with huge numbers of stored serum samples, enabled rapid progress in understanding hepatitis B, and revealed the existence of a vast population of chronically infected people in Asia, Oceania and Africa. In this article, we place the identification of the Australia antigen within the historical context of research on viral hepatitis. Following a chronological review from 1865 to 1965, we summarize how the discovery led to improved safety of blood transfusion, the development of a highly effective vaccine and the eventual identification of the hepatitis C, D and E viruses. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for chronic hepatitis B."

Course of hepatitis B and D virus infection in auxiliary liver grafts in hepatitis B-positive patients. A light-microscopic and immunohistochemical study

Four patients who received an auxiliary partial liver graft for decompensated liver cirrhosis due to hepatitis B (HBV), associated in two cases with hepatitis D virus (HDV) superinfection, were studied. The sequential appearance of hepatitis B and D antigens in the grafts was investigated in serial liver biopsies by immuno-histochemical methods and compared with the viral antigenic profiles of the host livers. The histological changes in the liver grafts were studied in relation to the viral expression patterns. One week after transplantation, expression of HBsAg was already apparent in two grafts. HBcAg was found in the graft of the only patient with HBcAg in the host liver. HDAg was expressed in the grafts of both patients with HDV superinfection; in one of these cases HDAg was present without HBsAg. At 3 months, viral antigen expression was maximal. Expression of HBsAg and HBcAg in the grafts of the two HDV-positive patients was, however, less extensive than in the two HBV-positive patients. All patients developed a mild lobular hepatitis, histologically demonstrated between the 47th and 107th posttransplantation day. In the two HBV-positive, HDV-negative patients, cirrhotic transformation of the graft occurred within 1 year. In the HDV-positive patients only a mild chronic active hepatitis with slight or moderate fibrosis was observed after 1 year. We conclude that recurrence of HBV and HDV infection in auxiliary liver grafts is demonstrable within 1-3 weeks. HBV infection in liver grafts may be a rapidly progressive disease. Coinfection with HDV does not aggravate the acute hepatitis and may even suppress the progression of chronic HBV.

Immuno-light and electron microscopic features of chronic hepatitis D

A morphologic study with immunohistochemical detection of the viral antigens of hepatitis B and Delta was performed on 36 liver specimens from patients with delta positive chronic viral hepatitis B. Electron microscopy was performed in 9 cases. No light microscopic or ultrastructural features specific for hepatitis D were observed. Lymphocytic infiltration occurred more often close to hepatocytes containing either hepatitis Delta antigen or hepatitis B core antigen in the cytoplasm, suggesting an involvement of cellular immune mechanisms in chronic hepatitis D as well as in hepatitis B. The simultaneous expression of both HBcAg and Delta antigen in occasional specimens over longer time periods indicates the possible co-existence of both viruses without mutual inhibition.

Immunoglobulin and hepatitis B surface antigen-specific circulating immune complexes in chronic hepatitis with hepatitis delta virus infection

IgM, IgG, and HBsAg containing circulating immune complexes (CIC) were determined, by conglutinin (K) and C1q assays, for assessing the role of CIC in hepatitis delta virus (HDV) infection in 54 HBsAg-negative controls and 85 HBsAg-positive patients with chronic hepatitis. The prevalence of HDV markers (HDV antigen and anti-HD) was 24.70% (21/85). CIC were a common feature of HDV infection with 95.24% of patients having at least one abnormal test result. The prevalence of elevated IgM-K, IgG-K, IgM-C1q, and IgG-C1q CIC were 85.71, 85.71, 57.14, and 85.71%, respectively. The prevalence of IgM class CIC were statistically higher in patients with HDV infection than in those without (P = .001 for the K assay and P = .023 for the C1q assay). There was no difference in the prevalence of IgG class CIC. Patients with HDV infection also have significantly higher median levels of IgM K-CIC (P = .002), IgG K-CIC (P = .049), and IgG C1q-CIC (P = .008). In patients with HDV infection, there was positive correlation between IgM C1q-CIC and transaminase levels (r = .519, P = .016 for AST; r = .500, P = .021 for ALT). There was no difference in the prevalence of HBsAg containing CIC between patients with HDV infection (76.19%) and those without (74.60%). In conclusion, IgM class CIC are the major CIC and correlate with disease activity in HDV infection. CIC may play a role in the pathogenesis of HDV infection.

Specific histologic features of Santa Marta hepatitis: a severe form of hepatitis delta-virus infection in northern South America

Stimulated by observations in an outbreak of hepatitis delta-virus infection among Yucpa Indians in Venezuela, in which unusual histologic features were found, we studied 100 cases of fatal hepatitis from Colombia, South America, which had been obtained by autopsy or viscerotomy. These cases were considered to be "Santa Marta hepatitis," or "hepatitis of the Sierra Nevada de Santa Marta," which has been observed in this region for more than 40 years. Of the 100 cases, 19 had a variety of histologic lesions or were normal, and hepatitis delta-virus antigen was not demonstrated immunocytochemically in any of them. By contrast, 81 cases had a characteristic histologic picture with intense microvesicular steatosis associated with conspicuous eosinophilic necrosis of the hepatocytes, which apparently were sluggishly removed by cytolysis. Hepatitis delta-virus antigen was detected in 70% of the 81 cases, and the absence of detection of this antigen was often associated with poor tissue preservation and more extensive hepatocyte necrosis. A smaller percentage of patients had hepatitis B virus antigens detectable in liver tissue. The characteristic lesion in these 81 cases could be distinguished from other causes of microvesicular steatosis by the extensive eosinophilic necrosis. Other variable accompanying features included intraacinar, mainly macrophagic, scavenger cell inflammation, intense portal inflammation, a parenchymal regeneration, and ductular and arteriolar proliferation. Santa Marta hepatitis as a severe form of hepatitis delta-virus infection differs markedly from fulminant delta-hepatitis in Europe and the United States in which the microsteatosis with marked eosinophilic degeneration is not found. The causes for these differences are unknown but may relate to nutritional factors or environmental toxins.(ABSTRACT TRUNCATED AT 250 WORDS)

[Frequency of delta infections in Heidelberg]

The frequency of delta infection was studied in sera of 203 patients with acute hepatitis B, further 461 hepatitis B virus surface antigen-(HBsAg)-positive patients and 117 HBsAg-negative controls by determination of anti-delta by a competitive enzyme immunoassay. Sera have been collected since 1974. None of the sera of acute hepatitis B was anti-delta-positive whereas seven of the HBsAg-positive carriers were anti-delta-positive. Two of the anti-delta-positive patients had chronic hepatitis, four had liver cirrhosis. One of the anti-delta-positive patients with liver cirrhosis died of liver failure. Risk factors included Italian origin and parenteral routes of infection. All sera of 19 relatives of three anti-delta-positive index cases remained anti-delta-negative.

Delta hepatitis agent: structural and antigenic properties of the delta-associated particle

Delta agent (delta) was serially passaged to a second and third hepatitis B surface antigen (HBsAg) carrier chimpanzee, using as inoculum the peak delta antigen (delta Ag) serum of an animal previously infected with human serum. The characteristics of serially transmitted delta Ag were similar to those described in first-passage animals. It was consistently detected before the development of anti-delta, in association with a 35- to 37-nm subpopulation of HBsAg particles and a unique low-molecular-weight (5.5 X 10(5)) RNA. RNase susceptibility of the delta-associated RNA and release of delta Ag activity upon treatment of delta-associated particles with detergent revealed that this particle is organized into a virion-like form with the RNA and delta Ag as internal components within a coat of HBsAg. Surface determinants of the delta-associated particle other than HBsAg were not detected by radioimmunoprecipitation experiments, using sera of humans and chimpanzees convalescent from delta hepatitis. The HBsAg-associated particle is the "candidate agent" of delta hepatitis.

Isolation and characterization of liver-derived hepatitis B e antigen

Two subpopulations of hepatitis B e antigen (HBeAg) were isolated from a human liver infected with hepatitis B virus. HBeAg extracted from liver homogenate subsequent to treatment with buffered 3 M NaSCN or 0.5 M MgCl2 banded at the density of 1.13 g/cm3 in CsCl and was polydispersed on gel filtration. In contrast, HBeAg released with phosphate-buffered saline (PBS) was detected mainly at a density of 1.20 g/cm3 in a CsCl gradient and consisted of low molecular weight species on gel chromatography. Polypeptides of 40,000 and 45,000 daltons were found in NaSCN and PBS-released HBeAg preparations, respectively. The results are interpreted as suggestive that liver HBeAg is a dimer of the major core particle polypeptide in different physicochemical forms.