Partial control of hepatitis delta virus superinfection by immunisation of woodchucks (<i>Marmota monax</i>) with hepatitis delta antigen expressed by a recombinant vaccinia or baculovirus

A woodchuck-derived hepatitis delta virus (HDV) inoculum was created by transfection of a genotype I HDV cDNA clone directly into the liver of a woodchuck that was chronically infected with woodchuck hepatitis virus. All woodchucks receiving this inoculum became positive for HDV RNA in serum, and 67% became chronically infected, similar to the rate of chronic HDV infection in humans. Analysis of HDV sequences obtained at 73 weeks postinfection indicated that changes had occurred at a rate of 0.5% per year; many of these modifications were consistent with editing by host RNA adenosine deaminase. The appearance of sequence changes, which were not evenly distributed on the genome, was correlated with the course of HDV infection. A limited number of modifications occurred in the consensus sequence of the viral genome that altered the sequence of the hepatitis delta antigen (HDAg). All chronically infected animals examined exhibited these changes 73 weeks following infection, but at earlier times, only one of the HDV carriers exhibited consensus sequence substitutions. On the other hand, sequence modifications in animals that eventually recovered from HDV infection were apparent after 27 weeks. The data are consistent with a model in which HDV sequence changes are selected by host immune responses. Chronic HDV infection in woodchucks may result from a delayed and weak immune response that is limited to a small number of epitopes on HDAg.Hepatitis delta virus (HDV) is an obligate subviral satellite of hepatitis B virus (HBV) that causes both acute and chronic liver disease in humans (13). The HDV virion is composed of a ribonucleoprotein core and an envelope formed by the surface antigen protein (HBsAg) of HBV (3-5). The envelope is the sole helper function provided by HBV. HDV is able to replicate within cells in the absence of HBV (17) but requires HBsAg for the packaging and release of HDV virions (29, 33) as well as for infectivity (32). In addition to the envelope of its natural helper HBV, HDV can be packaged by the surface antigen of related hepadnaviruses, including woodchuck hepatitis virus (WHV) (27, 29) and woolly monkey hepatitis B virus (18), and can produce both acute and chronic infection in woodchucks that are chronically infected with WHV (20,27,30).There are two modes of HDV infection: superinfection of an individual with chronic HBV infection and coinfection with both viruses of an individual who has not been exposed previously to HBV. While the latter type of exposure typically leads to recovery from both viral infections, the former results in chronic HDV infection with a frequency of 70% to 80% (13). The determinants of the outcome of HDV superinfection are not known. Previous studies of viral genetic changes during infection have analyzed HDV RNA obtained either from the sera of chronically infected patients during the course of HDV infection (7,14,19) or from the liver of a woodchuck infected with virus that had been passaged several times (21). These studies did not address whether genetic cha...

Section: Vol 80 2006 Hdv Genetic Changes During Acute or Chronic Inmentioning

confidence: 99%

Genetic Changes in Hepatitis Delta Virus from Acutely and Chronically Infected Woodchucks

Casey

Tennant

Gerin

2006

“…It also has been suggested that cytotoxic-T-cell epitopes of HDV may be located at the carboxyl end (amino acids 77 to 195) of S-HDAg (14). In a longitudinal analysis of the HDV genome at different time points during chronic HDV infection, the emergence of amino acid changes at the carboxyl end of S-HDAg (amino acids 170 to 195) usually occurred after a severe hepatitis attack (29).…”

mentioning

confidence: 99%

VariedImmunity Generated in Mice by DNA Vaccines with Large and SmallHepatitis DeltaAntigens

Huang

Hsu

et al. 2003

Hepatitis delta virus (HDV) is a defective single-stranded RNA virus. The assembly and transmission of HDV require a supply of hepatitis B surface antigen (HBsAg) from hepatitis B virus (HBV) (21, 25). HDV superinfection can lead to fulminant hepatic failure and also has a high probability of progressing to chronic hepatitis or cirrhosis (8,22,24,27,28). Furthermore, HDV superinfection can increase the risk of hepatocellular carcinoma and mortality in patients with HBVrelated cirrhosis (6). Although the present HBV vaccine is very effective, about 350 million individuals are already chronically infected by HBV worldwide (4). At present, interferon is the only licensed drug for treating chronic hepatitis D, but the relapse rate is high after discontinuation (5). The development of a prophylactic or therapeutic HDV vaccine has a potential use for HBV carriers who are at risk of HDV superinfection and for those who have been infected by HDV already. DNA vaccination is a promising method for preventing and treating persistent viral infections. Previous results suggested that DNA vaccines can produce Th1 immune responses against HDV (11).HDV has two forms of viral proteins, large and small hepatitis D antigens (HDAg). The mRNA encoding large HDAg (L-HDAg) contains a UGG tryptophan codon at the site of the UAG amber termination codon of small HDAg (S-HDAg) because of an RNA editing event (1, 2, 3). Therefore, L-HDAg contains an additional 19 amino acids at the C terminus. LHDAg can be isoprenylated at a unique cysteine located 4 amino acids from the C terminus (7). Mutation of this unique cysteine of L-HDAg to serine can block isoprenylation and HDV assembly (7). Evidence has shown that these additional 19 amino acids of L-HDAg can alter the overall conformation and hydrophobicity of HDAg (12,13,15,18). S-HDAg also contains a unique conformation at the C terminus. This conformation is detectable with a monoclonal antibody (9E4) which is specific for S-HDAg and which does not react with L-HDAg. When isoprenylation is inhibited, this epitope become exposed in L-HDAg (12, 13). Based on this evidence, host immune responses may be different when immunization is carried out with endogenous L-HDAg versus S-HDAg.A previous study demonstrated that an L-HDAg-encoding DNA vaccine could produce low titers of anti-HDV antibodies (11). However, in a subsequent study with the HDV DNA vaccine, no HDAg-specific antibody titers were detectable by a commercial enzyme-linked immunosorbent assay (ELISA) or by a Western blot assay (17). This discrepancy needs further study for clarification.The immunogenic domain of HDV recognized by chronically HDV-infected patients includes amino acids 2 to 7, 63 to 74, 86 to 91, 94 to 100, 159 to 172, 174 to 195, and 197 to 207 (23). It also has been suggested that cytotoxic-T-cell epitopes of HDV may be located at the carboxyl end (amino acids 77 to 195) of . In a longitudinal analysis of the HDV genome at different time points during chronic HDV infection, the emergence of amino acid changes at the c...

“…Since the 1980s, several vaccine strategies have been investigated in woodchucks (reviewed in reference 10). Only after immunization with vaccines that are known to induce a CD8 ϩ T cell response, namely, vaccinia virus and DNA-based vaccines, was a modulation of the course of superinfection described (15,24). However, none of the animals had been protected against HDV infection so far.…”

Section: Discussionmentioning

confidence: 99%

“…For the protection of chronically HBV-or WHV-infected patients or woodchucks from HDV superinfection virus-specific T cells would have to circulate in high numbers at the time point of HDV superinfection to inhibit rapid infection of numerous hepatocytes. This could explain why only a delay of the appearance of HDV RNA and not long-term protection was observed after immunization with DNA or vaccinia virus (15,24). Another explanation for the different outcomes of vaccination prior to superinfection or to simultaneous infection may be a dysfunction of HDV-specific T cells in the state of chronic HBV infection by the presence of regulatory T cells (Treg cells).…”

Section: Discussionmentioning

confidence: 99%

Prime/Boost Immunization with DNA and Adenoviral Vectors Protects from Hepatitis D Virus (HDV) Infection after Simultaneous Infection with HDV and Woodchuck Hepatitis Virus

Fiedler

Kosinska

Schumann

et al. 2013

Hepatitis D virus (HDV) superinfection of hepatitis B virus (HBV) carriers causes severe liver disease and a high rate of chronicity. Therefore, a vaccine protecting HBV carriers from HDV superinfection is needed. To protect from HDV infection an induction of virus-specific T cells is required, as antibodies to the two proteins of HDV, p24 and p27, do not neutralize the HBV-derived envelope of HDV. In mice, HDV-specific CD8 ؉ and CD4 ؉ T cell responses were induced by a DNA vaccine expressing HDV p27. In subsequent experiments, seven naive woodchucks were immunized with a DNA prime and adenoviral boost regimen prior to simultaneous woodchuck hepatitis virus (WHV) and HDV infection. Five of seven HDV-immunized woodchucks were protected against HDV infection, while acute self-limiting WHV infection occurred as expected. The two animals with the breakthrough had a shorter HDV viremia than the unvaccinated controls. The DNA prime and adenoviral vector boost vaccination protected woodchucks against HDV infection in the setting of simultaneous infection with WHV and HDV. In future experiments, the efficacy of this protocol to protect from HDV infection in the setting of HDV superinfection will need to be proven. H epatitis delta virus (HDV) superinfection of hepatitis B virus (HBV) carriers causes the most severe hepatitis in humans.Nearly all patients develop chronic HDV infection that has a high probability of progressing to liver cirrhosis and hepatocellular carcinoma (1, 2). Worldwide, approximately 15 million patients are affected with HDV. About 8% of HBV surface antigen (HBsAg)-positive patients in several European countries have tested positive for antibodies against HDV (2). Therapeutic options for HBV/HDV carriers are limited. Only in about 25% of the patients does alpha interferon therapy result in sustained viral clearance (3).HBV carriers are at risk of being superinfected with HDV. Therefore, a vaccine protecting HBV carriers from HDV superinfection would be eligible. A main obstacle for the design of a vaccine against HDV infection is the fact that antibodies to the two proteins of HDV, p24 and p27, do not neutralize the HDV particle. The HDV protein/RNA complex is covered by the envelope protein of HBV (HBsAg). Therefore, classical vaccines which induce neutralizing antibodies cannot be expected to prevent HDV infection.Immunizations with nucleoproteins of, e.g., influenza A virus-, HBV-, or woodchuck hepatitis virus (WHV) induced virus-specific T cells and were able to suppress replication, e.g., by cytokine secretion. In a second step, these virus-specific T cells are able to eliminate infected cells by their cytolytic activity and thus prevent the spread of the virus (4-7). T cell vaccines may not provide sterile immunity, because they do not induce neutralizing antibodies. However, T cell vaccines may stop infection via the cellular immune response at a very early phase of infection. Most conventional vaccines for humans induce sufficient amounts of neutralizing antibodies which prevent infection. ...