Serological evidence for a hepatitis e virus-related agent in goats in the United States

Hepatitis E virus (HEV) causes an important public health disease in many developing countries and is also endemic in some industrialized countries. In addition to humans, strains of HEV have been genetically identified from pig, chicken, rat, mongoose, deer, rabbit and fish. While the genotypes 1 and 2 HEV are restricted to humans, the genotypes 3 and 4 HEV are zoonotic and infect humans and other animal species. As a part of our ongoing efforts to search for potential animal reservoirs for HEV, we tested goats from Virginia for evidence of HEV infection and showed that 16% (13/80) of goat sera from Virginia herds were positive for IgG anti-HEV. Importantly, we demonstrated that neutralizing antibodies to HEV were present in selected IgG anti-HEV positive goat sera. Subsequently, in an attempt to genetically identify the HEV-related agent from goats, we conducted a prospective study in a closed goat herd with known anti-HEV seropositivity and monitored a total of 11 kids from the time of birth until 14 weeks of age for evidence of HEV infection. Seroconversion to IgG anti-HEV was detected in seven of the 11 kids, although repeated attempts to detect HEV RNA by a broad-spectrum nested RT-PCR from the faecal and serum samples of the goats that had seroconverted were unsuccessful. In addition, we also attempted to experimentally infect laboratory goats with three well-characterized mammalian strains of HEV but with no success. The results indicate that a HEV-related agent is circulating and maintained in the goat population in Virginia and that the goat HEV is likely genetically very divergent from the known HEV strains.

Mutational analysis of the hepatitis C virus E1 glycoprotein in retroviral pseudoparticles and cell-culture-derived H77/JFH1 chimeric infectious virus particles

Cell entry by enveloped viruses is mediated by viral glycoproteins, and generally involves a short hydrophobic peptide (fusion peptide) that inserts into the cellular membrane. An internal hydrophobic domain within E1 (aa262-290) of hepatitis C virus (HCV) may function as a fusion peptide. Retrovirus-based HCV-pseudotyped viruses (HCVpp; genotype 1a) containing Ala or Pro substitutions at conserved amino acid positions within this putative fusion peptide were generated. Mutation of conserved residues significantly reduced efficiency of HCVpp entry into Huh-7 cells. The majority of amino acid substitutions appeared to disrupt necessary interactions between E1 and E2. For some mutants, reductions in HCVpp-associated E1 were associated with the incorporation of a high molecular weight, hyperglycosylated E2 that displayed decreased CD81-binding. Other entry-deficient mutants displayed normal E1E2 incorporation into pseudoparticles and normal CD81-binding, and therefore might affect viral fusion. One mutant (S283P) consistently displayed two- to threefold higher infectivity than did wild-type. Three mutations that decreased HCVpp infectivity also reduced levels of HCVcc infectious virus production. However, the S283P mutation had a different effect in the two systems as it did not increase production of infectious HCVcc. This comprehensive mutational analysis of the putative HCV fusion peptide provides insight into the role of E1 in its interaction with E2 and in HCV entry.

Hepatitis E: an emerging awareness of an old disease

Although hepatitis E was recognized as a new disease in 1980, the virus was first visualized in 1983 and its genome was cloned and characterized in 1991, the disease is probably ancient but not recognized until modern times. Hepatitis E is the most important or the second most important cause of acute clinical hepatitis in adults throughout Asia, the Middle East and Africa. In contrast, hepatitis E is rare in industrialized countries, but antibody (anti-HEV) is found worldwide. HEV is a small round RNA-containing virus that is the only member of the genus Hepevirus in the family Hepeviridae. Although similar to hepatitis A virus in appearance, there are significant differences between the two viruses. Hepatitis E is principally the result of a water-borne infection in developing countries and is thought to be spread zoonotically (principally from swine) in industrialized countries. Because diagnostic tests vary greatly in specificity, sensitivity and availability, hepatitis E is probably underdiagnosed. At present, control depends upon improved hygiene; a highly efficacious vaccine has been developed and tested, but it is not presently available.

Characterization of hepatitis E-specific cell-mediated immune response using IFN-gamma ELISPOT assay

In developing countries, hepatitis E (HEV) and hepatitis A (HAV) are the major causes of acute viral hepatitis with similar feco-oral modes of transmission. In contrast to the high seroprevalence of hepatitis A infection, a low seroprevalence of HEV among children in endemic areas has been reported. These data suggest the possibility that silent HEV infection is undiagnosed by the current available methods. Many of the serological tests used for HEV diagnosis have poor specificity and are unable to differentiate among different genotypes of HEV. Moreover, the RT-PCR used for HEV isolation is only valid for a brief period during the acute stage of infection. Cell-mediated immune (CMI) responses are highly sensitive, and long lasting after sub-clinical infections as shown in HCV and HIV. Our objective was to develop a quantitative assay for cell-mediated immune (CMI) responses in HEV infection as a surrogate marker for HEV exposure in silent infection. Quantitative assessment of the CMI responses in HEV will also help us to evaluate the role of CMI in HEV morbidity. In this study, an HEV-specific interferon-gamma (IFN-gamma) ELISPOT assay was optimized to analyze HEV-specific CMI responses. We used peripheral blood mononuclear cells (PBMC) and sera from experimentally infected chimpanzees and from seroconverted and control human subjects to validate the assay. The HEV-specific IFN-gamma ELISPOT responses correlated strongly and significantly with anti-HEV ELISA positive/negative results (rho=0.73, p=0.02). Moreover, fine specificities of HEV-specific T cell responses could be identified using overlapping HEV ORF2 peptides.

A survey of zoonotic pathogens carried by Norway rats in Baltimore, Maryland, USA

Norway rats (Rattus norvegicus) carry several zoonotic pathogens and because rats and humans live in close proximity in urban environments, there exists potential for transmission. To identify zoonotic agents carried by rats in Baltimore, Maryland, USA, we live-trapped 201 rats during 2005-2006 and screened them for a panel of viruses, bacteria, and parasites. Antibodies against Seoul virus (57.7%), hepatitis E virus (HEV, 73.5%), Leptospira interrogans (65.3%), Bartonella elizabethae (34.1%), and Rickettsia typhi (7.0%) were detected in Norway rats. Endoparasites, including Calodium hepatica (87.9%) and Hymenolepis sp. (34.4%), and ectoparasites (13.9%, primarily Laelaps echidninus) also were present. The risk of human exposure to these pathogens is a significant public health concern. Because these pathogens cause non-specific and often self-limiting symptoms in humans, infection in human populations is probably underdiagnosed.

Determination and analysis of the complete genomic sequence of avian hepatitis E virus (avian HEV) and attempts to infect rhesus monkeys with avian HEV

Avian hepatitis E virus (avian HEV), recently identified from a chicken with hepatitis-splenomegaly syndrome in the United States, is genetically and antigenically related to human and swine HEVs. In this study, sequencing of the genome was completed and an attempt was made to infect rhesus monkeys with avian HEV. The full-length genome of avian HEV, excluding the poly(A) tail, is 6654 bp in length, which is about 600 bp shorter than that of human and swine HEVs. Similar to human and swine HEV genomes, the avian HEV genome consists of a short 5' non-coding region (NCR) followed by three partially overlapping open reading frames (ORFs) and a 3'NCR. Avian HEV shares about 50 % nucleotide sequence identity over the complete genome, 48-51 % identity in ORF1, 46-48 % identity in ORF2 and only 29-34 % identity in ORF3 with human and swine HEV strains. Significant genetic variations such as deletions and insertions, particularly in ORF1 of avian HEV, were observed. However, motifs in the putative functional domains of ORF1, such as the helicase and methyltransferase, were relatively conserved between avian HEV and mammalian HEVs, supporting the conclusion that avian HEV is a member of the genus Hepevirus. Phylogenetic analysis revealed that avian HEV represents a branch distinct from human and swine HEVs. Swine HEV infects non-human primates and possibly humans and thus may be zoonotic. An attempt was made to determine whether avian HEV also infects across species by experimentally inoculating two rhesus monkeys with avian HEV. Evidence of virus infection was not observed in the inoculated monkeys as there was no seroconversion, viraemia, faecal virus shedding or serum liver enzyme elevation. The results from this study confirmed that avian HEV is related to, but distinct from, human and swine HEVs; however, unlike swine HEV, avian HEV is probably not transmissible to non-human primates.

Detection of immunoglobulin M antibodies to hepatitis E virus by class capture enzyme immunoassay

The measurement of antibodies to hepatitis E virus (anti-HEV) has been essential for understanding the epidemiology of hepatitis E. Studies to determine the prevalence of HEV infections require a reliable serologic assay that is sensitive and specific. It is also important to distinguish the acute from the convalescent phase of an infection; this usually requires the detection of the immunoglobulin M (IgM) class of antibody. Few enzyme immunoassays (EIAs) that measure IgM anti-HEV have been described, and most have utilized the sandwich method. The present study describes an EIA that detects IgM anti-HEV by antibody class capture methodology. The assay was validated by using serum and/or plasma panels from experimentally infected nonhuman primates. It was used to demonstrate an anamnestic response and the reappearance of IgM anti-HEV in a chimpanzee experimentally challenged with HEV at two different times 45 months apart. The class capture method was more sensitive than the sandwich EIA when used to test clinical samples from two hepatitis E epidemics in Pakistan; it also had the advantage of distinguishing IgM anti-HEV in the presence of high titers of IgG anti-HEV.

Hepatitis E virus (HEV) capsid antigens derived from viruses of human and swine origin are equally efficient for detecting anti-HEV by enzyme immunoassay

The recombinant truncated ORF2 (capsid) antigen derived from the Meng strain of swine hepatitis E virus (HEV) differs from that of the Sar-55 strain of human HEV by approximately 5% at the amino acid level. Serial serum samples from two chimpanzees and six rhesus monkeys experimentally infected with HEV were tested with one enzyme immunoassay (EIA) based on the Sar-55 antigen and with a second EIA based on the Meng antigen. We obtained 98% agreement (kappa = 0.952) by direct comparison. The virtually identical results obtained with these antigens in detecting seroconversion following infection with HEV suggests that they were reacting with antibodies that detect the same or very similar epitopes of HEV. We then tested human and swine serum samples for anti-HEV in EIAs that utilized one or the other of the two ORF2 antigens and showed that these results were also virtually identical. The specimens tested included swine sera from the United States, Canada, China, Korea, and Thailand and sera from veterinarians, U.S. and non-U.S. volunteer blood donors, and U.S. and non-U.S. animal handlers. We tested 792 swine sera and obtained 93% agreement (kappa = 0.839). We similarly tested 882 human sera and obtained 99% agreement (kappa = 0.938). Moreover, we found virtually no difference in the levels of prevalence of anti-HEV as measured by the two tests, again suggesting that the antigens derived from human and swine HEV contain the same immunodominant epitopes.

Studies of hepatitis C virus in chimpanzees and their importance for vaccine development

Persistent infection with hepatitis C virus (HCV) is an important cause of chronic liver disease worldwide. Therefore, the development of vaccines to prevent HCV infection, or at least to prevent progression to chronicity, is a major goal. Potential HCV vaccine candidates include recombinant proteins, recombinant viruses, DNA constructs, synthetic peptides and virus-like particles. Various vaccine candidates have been shown to generate humoral and cellular immune responses in animals, primarily in mice. However, the efficacy of most vaccine candidates in protecting against HCV has not been tested because the chimpanzee, the only animal other than humans that is susceptible to HCV, is not readily available, requires special facilities, and is very expensive. The course of infection in chimpanzees is similar in its diversity to that in humans and detailed studies in this model are beginning to define the immune responses that can terminate HCV infection. Of relevance for vaccine evaluation was the titration in chimpanzees of different HCV variants to provide well-characterized challenge pools. In addition, monoclonal virus pools generated from chimpanzees infected with cloned viruses make it possible now to examine immunity to HCV without the confounding factor of antigenic diversity of the challenge virus (quasispecies). The vaccine trials performed in chimpanzees to date all have tested the efficacy of immunizations with various forms of the envelope proteins of HCV.

Four chimpanzee monoclonal antibodies isolated by phage display neutralize hepatitis a virus

Chimpanzee immunoglobulins are virtually identical to human immunoglobulins and may have clinically useful applications. Four chimpanzee monoclonal antibodies (MAbs) to the hepatitis A virus (HAV) capsid were isolated from a combinatorial cDNA library of gamma1/kappa antibody genes using phage display. Competition assays indicated that three of the MAbs recognized the same or overlapping epitopes, whereas the fourth recognized a different, nonoverlapping epitope on the HAV capsid. All four MAbs neutralized the homologous HAV strain, HM-175, in a radioimmunofocus assay and two of the four MAbs neutralized a heterologous simian HAV strain, AGM-27. From these data, we conclude that the MAbs must recognize at least three epitopes on the HAV capsid. Furthermore, competition assays performed with neutralizing murine MAbs suggested that three of the chimpanzee MAbs recognized epitopes on the HAV capsid which have not been defined previously.

Prevalence of antibodies to hepatitis E virus in veterinarians working with swine and in normal blood donors in the United States and other countries

Hepatitis E virus (HEV) is endemic in many developing and some industrialized countries. It has been hypothesized that animals may be the source of infection. The recent identification of swine HEV in U.S. pigs and the demonstration of its ability to infect across species have lent credence to this hypothesis. To assess the potential risk of zoonotic HEV infection, we tested a total of 468 veterinarians working with swine (including 389 U.S. swine veterinarians) and 400 normal U.S. blood donors for immunoglobulin G anti-HEV. Recombinant capsid antigens from a U.S. strain of swine HEV and from a human HEV strain (Sar-55) were each used in an enzyme-linked immunosorbent assay. The anti-HEV prevalence assayed with the swine HEV antigen showed 97% concordance with that obtained with the human HEV antigen (kappa = 92%). Among the 295 swine veterinarians tested from the eight U.S. states (Minnesota, Indiana, Nebraska, Iowa, Illinois, Missouri, North Carolina, and Alabama) from which normal blood donor samples were available, 26% were positive with Sar-55 antigen and 23% were positive with swine HEV antigen. In contrast, 18% of the blood donors from the same eight U.S. states were positive with Sar-55 antigen and 17% were positive with swine HEV antigen. Swine veterinarians in the eight states were 1.51 times more likely when tested with swine HEV antigen (95% confidence interval, 1.03 to 2.20) and 1.46 times more likely when tested with Sar-55 antigen (95% confidence interval, 0.99 to 2.17) to be anti-HEV positive than normal blood donors. We did not find a difference in anti-HEV prevalence between veterinarians who reported having had a needle stick or cut and those who had not or between those who spent more time (> or = 80% of the time) and those who spent less time (< or = 20% of the time) working with pigs. Similarly, we did not find a difference in anti-HEV prevalence according to four job categories (academic, practicing, student, and industry veterinarians). There was a difference in anti-HEV prevalence in both swine veterinarians and blood donors among the eight selected states, with subjects from Minnesota six times more likely to be anti-HEV positive than those from Alabama. Age was not a factor in the observed differences from state to state. Anti-HEV prevalence in swine veterinarians and normal blood donors was age specific and paralleled increasing age. The results suggest that swine veterinarians may be at somewhat higher risk of HEV infection than are normal blood donors.

Recombinant hepatitis E virus genomes infectious for primates: importance of capping and discovery of a cis-reactive element

Hepatitis E virus recombinant genomes transcribed in vitro from two cDNA clones differing by two nucleotides were infectious for chimpanzees. However, one cDNA clone encoded a virus that was attenuated for chimpanzees and unable to infect rhesus monkeys. The second cDNA clone encoded a virus that infected both chimpanzees and rhesus monkeys and caused acute hepatitis in both. One mutation differentiating the two clones identified a cis-reactive element that appeared to overlap the 3' end of the capsid gene and part of the 3' noncoding region. Capping of the RNA transcripts was essential for infectivity.

Immunogenicity and protective efficacy of a vaccine prepared from 53 kDa truncated hepatitis E virus capsid protein expressed in insect cells

Hepatitis E virus (HEV) is an enterically transmitted virus that causes acute hepatitis. Expression of recombinant HEV capsid protein in insect cells results in two major proteolytically-processed products of 56 and 53kDa which consist of amino acids (aa) 112-607 and 112-578, respectively. The only neutralization epitope identified to date is located at least partially between amino acids 578 and 607 meaning it should be present only in the 56 and not in the 53kDa protein. Previously, it was shown that vaccination with the 56kDa protein greatly reduced virus shedding and protected Rhesus monkeys from hepatitis E when challenged with a high intravenous dose of homologous or heterologous HEV. To evaluate the immunogenicity and protective efficacy of the 53kDa protein, we vaccinated Rhesus monkeys with this protein and challenged them with a high or low dose of homologous virus. Vaccination with the 53kDa protein greatly reduced virus shedding but did not protect against hepatitis following the high dose challenge. Virus was not detected in the vaccinated animals following the low dose challenge, suggesting that sterilizing immunity may have been achieved.

Host range studies of GB virus-B hepatitis agent, the closest relative of hepatitis C virus, in New World monkeys and chimpanzees

GB virus-B (GBV-B) is a member of the Flaviviridae family of viruses. This RNA virus causes acute resolving hepatitis in experimentally infected tamarins, but its natural host remains unknown. GBV-B and a related virus, GBV-A, were recovered from serum containing the "GB agent," which was believed to have originated from a surgeon (initials: GB) with acute hepatitis. GBV-B has special interest because it is the virus related most closely to hepatitis C virus, which is an important cause of acute and chronic liver disease in humans. In the present study, we found that the host range of GBV-B includes owl monkeys. Tamarins and owl monkeys belong to two different families of New World monkeys. The natural history of GBV-B in the two owl monkeys studied was similar to that previously found for tamarins and was characterized by early appearance of viremia and viral clearance. However, the peak viral titers of GBV-B observed in owl monkeys (10(5) genome equivalents [GE] /ml) were lower than those observed in experimentally infected tamarins (10(7)-10(8) GE/ml) and acute hepatitis was observed in only one animal. If GBV-B were indeed a virus of humans, it would be expected to infect chimpanzees, a surrogate of humans, because all recognized human hepatitis viruses are transmissible to chimpanzees and cause hepatitis. However, in the present study, we failed to transmit GBV-B to a naive chimpanzee. In addition, a second naive chimpanzee transfected intrahepatically with RNA transcripts from an infectious clone of GBV-B did not become infected. Thus, chimpanzees are apparently not susceptible to GBV-B. Finally, we failed to detect GBV-B in acute-phase serum from surgeon GB. Our data suggest that GBV-B is not a human virus and that GBV-B, like GBV-A, is a virus of New World monkeys.

Identification of the 5' terminal sequence of the SAR-55 and MEX-14 strains of hepatitis E virus and confirmation that the genome is capped

Hepatitis E virus (HEV) is a nonenveloped virus with a genome of single-stranded, positive-sense RNA. The 5' terminal sequence of two HEV strains (SAR-55 and MEX-14) was determined by a 5' RNA ligase-mediated rapid amplification of cDNA ends (RACE) method designed to select capped RNAs. The 5' noncoding region of the SAR-55 and MEX-14 strains were amplified, confirming that the genomic RNA of HEV is capped. The 5' noncoding region of the SAR-55 strain had 25 nucleotides, which is two less than reported for the Burmese strain, and that of the MEX-14 strain had 24 nucleotides, which is 21 more than reported previously [Huang et al., 1992].

Epidemiology of acute hepatitis in the Stann Creek District of Belize, Central America

Hepatitis is common in the Stann Creek District of southern Belize. To determine the etiologies, incidence, and potential risk factors for acute jaundice, we conducted active surveillance for cases. Cases of jaundice diagnosed by a physician within the previous 6 weeks were enrolled. Evaluation included a questionnaire and laboratory tests for hepatitis A, B, C, D, and E, a blood film for malaria, and a serologic test for syphilis. Etiologies of jaundice among 62 evaluable patients included acute hepatitis A, 6 (9.7%), acute hepatitis B, 49 (79.0%), hepatitis non-A-E, 2 (3.2%), and malaria, 5 (8.1%). There were no cases of acute hepatitis E. One patient each with antibody to hepatitis C and D were detected. The annualized incidence of hepatitis A was 0.26 per 1,000. All cases of hepatitis A were in children 4-16 years of age. The annualized incidence of hepatitis B, 2.17 per 1,000, was highest in adults aged 15-44 years (4.4 per 1,000) and was higher in men (36 cases; 3.09 per 1,000) than women (13 cases; 1.19 per 1,000). Four (31%) of the women with hepatitis B were pregnant. The annualized incidence was significantly higher in Mestizo (6.18 per 1000) and Maya (6.79 per 1,000) than Garifuna (0.38 per 1,000) or Creole (0.36 per 1,000). Persons with hepatitis B were significantly more likely to be born outside of Belize (82%), had been in Belize < 5 years (73%), and lived and worked in rural areas (96%) than was the general population. Of those > or = 14 years of age with hepatitis B, only 36% were married. Few persons admitted to transfusions, tattoos, IV drug use, multiple sexual partners, visiting prostitutes, or sexually transmitted diseases. Only 1 of 49 had a reactive test for syphilis. Six patients were hospitalized (including 3 with acute hepatitis B and one with hepatitis A), and none to our knowledge died. Acute hepatitis B is the most common cause of viral hepatitis in the Stann Creek District, but the modes of transmission remain obscure. Infants, women attending prenatal clinics, and new workers are potential targets for immunization with hepatitis B vaccine.

Recombinant vaccines for hepatitis E

Hepatitis E virus causes epidemics of acute hepatitis in many developing countries. It infrequently causes disease in developed countries, but avirulent strains might circulate. Some evidence suggests that hepatitis E might be a zoonosis. There is probably only a single serotype. A candidate vaccine consisting of baculovirus-expressed recombinant capsid protein protected macaques from hepatitis E--it passed phase I clinical trials and is currently scheduled for phase II/III clinical trials.

A virus discovery method incorporating DNase treatment and its application to the identification of two bovine parvovirus species

Identification of previously unrecognized viral agents in serum or plasma samples is of great medical interest but remains a major challenge, primarily because of abundant host DNA. The current methods, library screening or representational difference analysis (RDA), are very laborious and require selected sample sets. We have developed a simple and reproducible method for discovering viruses in single serum samples that is based on DNase treatment of the serum followed by restriction enzyme digestion and sequence-independent single primer amplification (SISPA) of the fragments, and have evaluated its performance on known viruses. Both DNA viruses and RNA viruses at a concentration of approximately 10(6) genome equivalents per ml were reproducibly identified in 50 microl of serum. While evaluating the method, two previously unknown parvoviruses were discovered in the bovine sera used as diluent. The near complete genome sequence of each virus was determined; their classification as two species (provisionally named bovine parvoviruses 2 and 3) was confirmed by phylogenetic analysis. Both viruses were found to be frequent contaminants of commercial bovine serum. DNase treatment of serum samples may prove to be a very useful tool for virus discovery. The DNase-SISPA method is suitable for screening of a large number of samples and also enables rapid sequence determination of high-titer viruses.

High-level expression of hepatitis C virus (HCV) structural proteins by a chimeric HCV/BVDV genome propagated as a BVDV pseudotype

A chimeric cDNA genome was constructed in which the core, E1 and E2 genes of hepatitis C virus (HCV) replaced the core, E(rns), E1 and E2 genes of bovine viral diarrhea virus (BVDV). High levels of HCV structural proteins were expressed in a small number of human or bovine cells following transfection with chimeric RNA. However, in one cell line, bovine embryonic trachea cells [EBTr(A)], the number of cells expressing HCV proteins increased to greater than 70% following serial passage of culture medium. These cells were persistently infected with a non-cytopathogenic BVDV helper virus. In these cells, the chimeric genome was packaged into infectious particles that accumulated in the culture medium at a titer as high as 10(7)-10(9) genome equivalents per ml. The virus particles were pseudotypes, because they were neutralized by anti-BVDV but not by anti-HCV.

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.

Failure to infect rhesus monkeys with hepatitis C virus strains of genotypes 1a, 2a or 3a

The chimpanzee is the only recognized animal model for the study of hepatitis C virus (HCV). However, recently it was reported that rhesus monkeys were susceptible to HCV and developed hepatitis during infection. In the present study, we inoculated two rhesus monkeys each with HCV strain H77 (genotype 1a), strain HC-J6 (genotype 2a) or strain S52 (genotype 3a). Weekly serum samples were tested for liver enzyme values, HCV antibodies and HCV RNA. We did not find evidence of HCV infection in any of the monkeys during 24 weeks of follow-up. Our study demonstrates that rhesus monkeys are not readily infected with HCV and apparently do not represent a useful animal model for the study of HCV.

Detection of antibodies to HAV 3C proteinase in experimentally infected chimpanzees and in naturally infected children

Commercial assays for the diagnosis of hepatitis A detect antibody to hepatitis A virus (anti-HAV), but they cannot discriminate between antibody resulting from infection and antibody induced by inactivated vaccine. With the licensing and increasing use of inactivated hepatitis A vaccines, there is a need for a test to distinguish between infection and vaccination. Since antibodies to viral non-structural proteins are elicited by infection but not by vaccination with inactivated vaccine, we developed and evaluated a test for such antibodies. The antibody response to the non-structural 3C proteinase (anti-3C) of virus HAV was studied by ELISA in chimpanzees experimentally infected with virulent (wild type) or with attenuated HAV strains and in children who received inactivated HAV vaccine or placebo during a vaccination trial in Nicaragua. Anti-3C was detected in 89% of 18 chimpanzees infected with wild-type HAV strains and 27% of 26 chimpanzees infected with attenuated HAV strains. There was a direct correlation between severity of hepatitis and magnitude of the anti-3C response. In the vaccine trial, anti-3C was detected only in children who were infected with HAV during the study; IgG anti-3C persisted for at least 15 months after infection in one child. Vaccinated and uninfected children remained negative for anti-3C. The anti-3C response can be regarded as an indicator of viral replication. Its detection should be useful for distinguishing between antibody acquired in response to HAV infection and antibody induced by immunization with inactivated vaccine.

Comparative pathogenesis of infection of pigs with hepatitis E viruses recovered from a pig and a human

Specific-pathogen-free pigs were inoculated with one of two hepatitis E viruses (HEV) (one recovered from a pig and the other from a human) to study the relative pathogenesis of the two viruses in swine. Fifty-four pigs were randomly assigned to three groups. Seventeen pigs in group 1 served as uninoculated controls, 18 pigs in group 2 were intravenously inoculated with the swine HEV recovered from a pig in the United States, and 19 pigs in group 3 were intravenously inoculated with the US-2 strain of human HEV recovered from a hepatitis patient in the United States. Two to four pigs from each group were necropsied at 3, 7, 14, 20, 27, or 55 days postinoculation (DPI). Evidence of clinical disease or elevation of liver enzymes or bilirubin was not found in pigs from any of the three groups. Enlarged hepatic and mesenteric lymph nodes were observed in both HEV-inoculated groups. Multifocal lymphoplasmacytic hepatitis was observed in 9 of 17, 15 of 18, and 16 of 19 pigs in groups 1 to 3, respectively. Focal hepatocellular necrosis was observed in 5 of 17, 10 of 18, and 13 of 19 pigs in groups 1 to 3, respectively. Hepatitis lesions were very mild in group 1 pigs, mild to moderate in group 2 pigs, and moderate to severe in group 3 pigs. Hepatic inflammation and hepatocellular necrosis peaked in severity at 20 DPI and were still moderately severe at 55 DPI in the group inoculated with human HEV. Hepatitis lesions were absent or nearly resolved by 55 DPI in the swine-HEV-inoculated pigs. All HEV-inoculated pigs seroconverted to anti-HEV immunoglobulin G. HEV RNA was detected by reverse transcriptase PCR in feces, liver tissue, and bile of pigs in both HEV-inoculated groups from 3 to 27 DPI. Based on evaluation of microscopic lesions, the US-2 strain of human HEV induced more severe and persistent hepatic lesions in pigs than did swine HEV. Pig livers or cells from the livers of HEV-infected pigs may represent a risk for transmission of HEV from pigs to human xenograft recipients. Since HEV was shed in the feces of infected pigs, exposure to feces from infected pigs represents a risk for transmission of HEV, and pigs should be considered a reservoir for HEV.

Clinical significance of hepatitis C virus genotypes and quasispecies

Hepatitis C virus (HCV) is a major cause of morbidity and mortality worldwide. The infection becomes chronic in about 85% of infected individuals, in the face of a strong humoral and cellular immune response. One of the most important features of HCV is its high degree of genetic variability, which is due to the inherent low fidelity of the viral replication machinery. As a consequence, HCV circulates in vivo as a population of divergent, albeit closely related, genomes exhibiting a distribution that follows the model referred to as a quasispecies. The genetic variability of HCV is complex and has been classified into four hierarchical strata: genotypes, subgenotypes, isolates, and quasispecies. Over the past few years, an extraordinary interest has been focused on the biologic and clinical implications of the genetic variability of HCV. Although there is consensus that the genotypes may influence the out come of antiviral therapy, their clinical significance in the natural history of the disease, as well as in transmission, infectivity, and pathogenesis of HCV infection, remains elusive. Conversely, evidence has accumulated that the quasispecies nature of HCV provides a large reservoir of biologically different viral variants that may have important clinical implications for viral persistence by immune escape mechanisms, for the generation of antiviral drug resistance, and for the development of an effective vaccine. This article reviews the state of the art on the biologic and clinical implications of the genetic variability of HCV.

Hepatitis C virus envelope protein E2 binds to CD81 of tamarins

Since recombinant envelope glycoprotein E2 of hepatitis C virus (HCV) binds to CD81 on human and chimpanzee cells, it has been suggested that CD81 may be a receptor for HCV. Humans and chimpanzees are the only species known to be susceptible to HCV infection. E2 has been reported not to bind to CD81 of the African green monkey, mouse, or rat, suggesting that binding of HCV to CD81 is species specific and may determine susceptibility to infection with HCV. We investigated the interaction between E2 of HCV and CD81 of tamarins, a group of small New World monkeys frequently used for the study of human viruses. Tamarins are not susceptible to HCV infection. Nonetheless, we found that three different forms of HCV E2 (intracellular, secreted, and cell surface-displayed) bound more efficiently to recombinant tamarin CD81 than to human CD81, as determined by ELISA and immunofluorescence. The affinity of the interaction was approximately 10-fold higher for tamarin than for human CD81. Binding of E2 to CD81 on cultured or primary tamarin cells was demonstrated by flow cytometry. In contrast to previous reports, there was also a low-affinity interaction between E2 and African green monkey CD81. Thus, the HCV E2 interaction with CD81 is not limited to humans and chimpanzees and does not predict susceptibility to HCV infection.

Hepatitis C virus lacking the hypervariable region 1 of the second envelope protein is infectious and causes acute resolving or persistent infection in chimpanzees

Persistent infection with hepatitis C virus (HCV) is among the leading causes of chronic liver disease. Previous studies suggested that genetic variation in hypervariable region 1 (HVR1) of the second envelope protein, possibly in response to host immune pressure, influences the outcome of HCV infection. In the present study, a chimpanzee transfected intrahepatically with RNA transcripts of an infectious HCV clone (pCV-H77C) from which HVR1 was deleted became infected; the DeltaHVR1 virus was subsequently transmitted to a second chimpanzee. Infection with DeltaHVR1 virus resulted in persistent infection in the former chimpanzee and in acute resolving infection in the latter chimpanzee. Both chimpanzees developed hepatitis. The DeltaHVR1 virus initially replicated to low titers, but virus titer increased significantly after mutations appeared in the viral genome. Thus, wild-type HCV without HVR1 was apparently attenuated, suggesting a functional role of HVR1. However, our data indicate that HVR1 is not essential for the viability of HCV, the resolution of infection, or the progression to chronicity.

Vaccination of chimpanzees with plasmid DNA encoding the hepatitis C virus (HCV) envelope E2 protein modified the infection after challenge with homologous monoclonal HCV

Hepatitis C virus (HCV) is an important cause of chronic liver disease worldwide. Development of vaccines to prevent HCV infection, or at least prevent progression to chronicity, is a major goal. In mice and rhesus macaques, a DNA vaccine encoding cell-surface HCV-envelope 2 (E2) glycoprotein stimulated stronger immune responses than a vaccine encoding intracellular E2. Therefore, we used DNA encoding surface-expressed E2 to immunize chimpanzees 2768 and 3001. Chimpanzee 3001 developed anti-E2 after the second immunization and antibodies to hypervariable region 1 (HVR1) after the third immunization. Although chimpanzee 2768 had only low levels of anti-E2 after the third immunization, an anamnestic response occurred after HCV challenge. CTL responses to E2 were not detected before challenge, but a strong response was detected after HCV challenge in chimpanzee 2768. An E2-specific CD4+ response was detected in chimpanzee 2768 before challenge and in both chimpanzees postchallenge. Three weeks after the last immunization, animals were challenged with 100 50% chimpanzee-infectious doses (CID(50)) of homologous monoclonal HCV. As a control, a naive chimpanzee was inoculated with 3 CID(50) of the challenge virus. The vaccine did not generate sterilizing immunity because both vaccinated chimpanzees were infected. However, both vaccinated chimpanzees resolved the infection early whereas the control animal became chronically infected. Compared with the control animal, hepatitis appeared earlier in the course of the infection in both vaccinated chimpanzees. Therefore, DNA vaccine encoding cell surface-expressed E2 did not elicit sterilizing immunity in chimpanzees against challenge with a monoclonal homologous virus, but did appear to modify the infection and might have prevented progression to chronicity.

Identification by phage display and characterization of two neutralizing chimpanzee monoclonal antibodies to the hepatitis E virus capsid protein

Two monoclonal antibodies (MAbs) against the ORF2 protein of the SAR-55 strain of hepatitis E virus (HEV) were isolated by phage display from a cDNA library of chimpanzee (Pan troglodytes) gamma1/kappa antibody genes. Both MAbs, HEV#4 and HEV#31, bound to reduced, denatured open reading frame 2 (ORF2) protein in a Western blot, suggesting that they recognize linear epitopes. The affinities (equilibrium dissociation constants, K(d)) for the SAR-55 ORF2 protein were 1.7 nM for HEV#4 and 5.4 nM for HEV#31. The two MAbs also reacted in an enzyme-linked immunosorbent assay with recombinant ORF2 protein from a heterologous HEV, the Meng strain. Each MAb blocked the subsequent binding of the other MAb to homologous ORF2 protein in indirect competition assays, suggesting that they recognize the same or overlapping epitopes. Radioimmunoprecipitation assays suggested that at least part of the linear epitope(s) recognized by the two MAbs is located between amino acids 578 and 607. MAbs were mixed with homologous HEV in vitro and then inoculated into rhesus monkeys (Macaca mulatta) to determine their neutralizing ability. Whereas all control animals developed hepatitis (elevated liver enzyme levels in serum) and seroconverted to HEV, those receiving an inoculum incubated with either HEV#4 or HEV#31 were not infected. Therefore, each MAb neutralized the SAR-55 strain of HEV in vitro.

The outcome of acute hepatitis C predicted by the evolution of the viral quasispecies

The mechanisms by which hepatitis C virus (HCV) induces chronic infection in the vast majority of infected individuals are unknown. Sequences within the HCV E1 and E2 envelope genes were analyzed during the acute phase of hepatitis C in 12 patients with different clinical outcomes. Acute resolving hepatitis was associated with relative evolutionary stasis of the heterogeneous viral population (quasispecies), whereas progressing hepatitis correlated with genetic evolution of HCV. Consistent with the hypothesis of selective pressure by the host immune system, the sequence changes occurred almost exclusively within the hypervariable region 1 of the E2 gene and were temporally correlated with antibody seroconversion. These data indicate that the evolutionary dynamics of the HCV quasispecies during the acute phase of hepatitis C predict whether the infection will resolve or become chronic.

Prevalence of antibodies to hepatitis E in two rural Egyptian communities

A population-based serosurvey in two rural Egyptian communities was used to assess age-specific prevalence of antibody to hepatitis E virus (anti-HEV). One community is in the Nile Delta (11,182 inhabitants; 3,997 participants) and the other in Upper Egypt (10,970 inhabitants; 6,029 participants). Samples were tested for anti-HEV with a commercial enzyme-linked immunoassay (ELISA) based on antigens derived from open reading frame (ORF)2 and ORF3. Although there was a clear difference in sensitivity among the lots of the commercial test used, it was still possible to determine the seroprevalence. The seroprevalence of anti-HEV exceeded 60% in the first decade of life, peaked at 76% in the second decade and remained above 60% until the eighth decade. Prevalence of this magnitude is among the highest reported in the world, with an age-specific pattern more similar to hyperendemic hepatitis A virus transmission than generally described. Lot-to-lot variation in the sensitivity of the commercial ELISA kit highlights a problem when comparing seroepidemiologic studies of different populations.

High prevalence of TT virus (TTV) in naive chimpanzees and in hepatitis C virus-infected humans: frequent mixed infections and identification of new TTV genotypes in chimpanzees

A recently discovered DNA virus, TT virus (TTV), is prevalent in humans. In the present study, the genetic heterogeneity of TTV was evaluated in hepatitis C virus (HCV)-infected patients and in chimpanzees. TTV DNA was detected by PCR in serum samples from all ten HCV-infected patients studied; at least five major TTV genotypes, all previously identified in humans, were recovered. Eight patients were infected with multiple variants of TTV. TTV DNA was detected by PCR in serum samples from 11 (65%) of 17 naive chimpanzees bred in captivity; a persistent infection was present in three of six animals. At least five chimpanzees were infected with more than one TTV variant. Detection of TTV DNA in chimpanzee faecal samples suggests the possibility of faecal-oral transmission. Phylogenetic analysis of ORF1 sequences amplified from chimpanzees identified three major genotypes which had not previously been recognized in humans.

Identification of hepatitis B virus indigenous to chimpanzees

Hepatitis B viruses (HBV) and related viruses, classified in the Hepadnaviridae family, are found in a wide variety of mammals and birds. Although the chimpanzee has been the primary experimental model of HBV infection, this species has not been considered a natural host for the virus. Retrospective analysis of 13 predominantly wild-caught chimpanzees with chronic HBV infection identified a unique chimpanzee HBV strain in 11 animals. Nucleotide and derived amino acid analysis of the complete HBV genome and the gene coding for the hepatitis B surface antigen (S gene) identified sequence patterns that could be used to reliably identify chimpanzee HBV. This analysis indicated that chimpanzee HBV is distinct from known human HBV genotypes and is closely related to HBVs previously isolated from a chimpanzee, gibbons, gorillas, and orangutans.

Delineation of a CpG phosphorothioate oligodeoxynucleotide for activating primate immune responses in vitro and in vivo

Oligodeoxynucleotides (ODN) containing unmethylated CpG dinucleotides within specific sequence contexts (CpG motifs) are detected, like bacterial or viral DNA, as a danger signal by the vertebrate immune system. CpG ODN synthesized with a nuclease-resistant phosphorothioate backbone have been shown to be potent Th1-directed adjuvants in mice, but these motifs have been relatively inactive on primate leukocytes in vitro. Moreover, in vitro assays that predict in vivo adjuvant activity for primates have not been reported. In the present study we tested a panel of CpG ODN for their in vitro and in vivo immune effects in mice and identified in vitro activation of B and NK cells as excellent predictors of in vivo adjuvant activity. Therefore, we tested >250 phosphorothioate ODN for their capacity to stimulate proliferation and CD86 expression of human B cells and to induce lytic activity and CD69 expression of human NK cells. These studies revealed that the sequence, number, and spacing of individual CpG motifs contribute to the immunostimulatory activity of a CpG phosphorothioate ODN. An ODN with a TpC dinucleotide at the 5' end followed by three 6 mer CpG motifs (5'-GTCGTT-3') separated by TpT dinucleotides consistently showed the highest activity for human, chimpanzee, and rhesus monkey leukocytes. Chimpanzees or monkeys vaccinated once against hepatitis B with this CpG ODN adjuvant developed 15 times higher anti-hepatitis B Ab titers than those receiving vaccine alone. In conclusion, we report an optimal human CpG motif for phosphorothioate ODN that is a candidate human vaccine adjuvant.

Effects of age and viral determinants on chronicity as an outcome of experimental woodchuck hepatitis virus infection

Acute hepadnavirus infections either resolve or progress to chronicity. Factors that influence chronicity as an outcome of hepatitis B virus (HBV) infection in humans can be studied experimentally in the woodchuck model. Accordingly, several woodchuck hepatitis virus (WHV) inocula were characterized. Representative inocula had high titers of infectious virus (approximately 10(7.7)-10(9.5) woodchuck 50% infectious doses per milliliter [WID(50%)/mL] by subcutaneous inoculation), with 1 WID(50%) ranging between 21 and 357 physical virion particles. WHV7P1 (standard high dose, 5 x 10(6) WID(50%)) produced a 72% chronicity rate (i.e., percent chronic of total infected) in neonatal woodchucks (1-3 days old). Comparable doses of WHV8P1 resulted in a lower chronicity rate in neonates (34% chronic) indicating that it represented a strain different from WHV7P1. Neonatal woodchucks were more susceptible to chronic infection by high doses of WHV7P1 (range, 65%-75% chronic) compared with 8-week-old weanlings (33% chronic) and adult woodchucks (0% chronic; i.e., all resolved). High doses of cloned wild-type viruses also induced high rates of chronicity in neonates (70%-80% chronic). Chronicity rates in neonates were decreased for low doses of WHV7P1 (500 WID(50%), 9% chronic) and for high doses of a precore WHeAg-minus mutant WHV8 clone (17% chronic). Thus, both age and viral determinants can influence chronicity as an outcome of experimental WHV infection. Standardized inocula will enable the study of mechanisms that initiate and maintain chronic hepadnavirus infection and also provide a means for developing WHV carriers for therapeutic studies.

High prevalence of TT virus (TTV) infection in patients on maintenance hemodialysis: frequent mixed infections with different genotypes and lack of evidence of associated liver disease

Recently, a novel DNA virus, TT virus (TTV), was identified in patients with post-transfusion non-A-G hepatitis. We analyzed the prevalence and clinical implications of TTV infection in a cohort of 96 Spanish patients on long-term hemodialysis. TTV DNA was detected by nested PCR in 51 (53%) of 96 patients, a prevalence significantly higher than that found in healthy blood donors. Persistent liver test abnormalities were found in only 2 (7.7%) of 26 patients infected with TTV alone, compared with 12 (75%) of 16 patients infected with hepatitis C or hepatitis B virus, or both (P < 0.01). Mixed infections with multiple strains of TTV, including different major genotypes, were common in patients on hemodialysis. These patients had received a significantly greater number of blood units (22.7 +/- 20) compared with patients apparently infected with a single strain of TTV (8.9 +/- 11) (P = 0.01). Phylogenetic analyses of TTV from infected patients identified strains of genotypes 1, 2, 3, and 4. In summary, TTV infection was common in patients on hemodialysis but was not associated with liver disease

Prevalence of antibodies to the hepatitis E virus in pigs from countries where hepatitis E is common or is rare in the human population

Hepatitis E virus (HEV) is a very important public health concern in many developing countries where epidemics of hepatitis E are common. Sporadic cases of clinical hepatitis E not only occur in these countries but also occur uncommonly in patients with no known epidemiological exposure to HEV in industrialized countries. The source of infection in industrialized countries is unknown but it has been suggested that animals might serve as a reservoir for HEV in both settings. We recently identified and characterized an HEV strain (swine HEV) that infects large numbers of pigs in the United States. To assess the potential of pigs to serve as a global reservoir of HEV, we measured the prevalence of HEV antibodies in pigs in two countries where hepatitis E is endemic and two countries where it is not. Swine herds in all four countries contained many pigs that were seropositive for IgG anti-HEV, although the percentage of seropositive pigs varied greatly from herd to herd. A very limited number of pig handlers in the two endemic countries were also tested and most of them were found to be seropositive for HEV. The results from this study suggest that hepatitis E is enzootic in pigs regardless of whether HEV is endemic in the respective human population. J. Med. Virol. 59:297-302, 1999. Published 1999 Wiley-Liss, Inc.

Evidence that the genomic RNA of hepatitis E virus is capped

Hepatitis E virus (HEV) is an unclassified virus with a positive-sense RNA genome and an undefined replication strategy. In order to determine whether the HEV genome is capped or not, we developed a reverse transcription-PCR assay that is based on the ability of a monoclonal antibody to recognize 7-methylguanosine (m(7)G). Antibody to m(7)G bound RNA extracted from virions of two different HEV genotypes. The cap analog competitively inhibited the binding of virion RNAs, demonstrating that HEV has a capped RNA genome.

Quasispecies in viral persistence and pathogenesis of hepatitis C virus

Hepatitis C virus (HCV) is an important cause of chronic liver disease worldwide. This RNA virus circulates as a quasispecies and its genetic heterogeneity has been implicated in the lack of protective immunity against HCV and in its persistence following infection. HCV might escape from immune surveillance by developing mutations in proteins that are subject to immune pressure.

Hepatitis C virus: an infectious molecular clone of a second major genotype (2a) and lack of viability of intertypic 1a and 2a chimeras

Of the six major genotypes of hepatitis C virus (HCV), infectious cDNA clones of only genotype 1 have been reported. Here, we report the construction of an infectious cDNA clone representing a second major HCV genotype, genotype 2. This infectious clone (pJ6CF) encodes the consensus polyprotein of strain HC-J6(CH), genotype 2a. Its encoded polyprotein differs from those of the infectious clones of genotypes 1a and 1b by approximately 30%. Intertypic chimeric cDNA clones constructed from infectious clones of genotypes 1a and 2a of HCV were not infectious. RNA transcripts of four chimeras containing the 2a structural genes (C, E1, and E2) in the backbone of an infectious genotype 1a clone (pCV-H77C) were not viable in a chimpanzee regardless of whether p7 was from the 1a or 2a clone. However, the chimpanzee was subsequently infected with RNA transcripts of each of the two infectious parent clones, indicating that the inability of the chimeras to replicate was intrinsic to the clones and not the result of preexisting protective immune responses.

Licensed recombinant hepatitis B vaccines protect chimpanzees against infection with the prototype surface gene mutant of hepatitis B virus

The emergence in vaccinated individuals of hepatitis B virus (HBV) mutants with amino acid substitutions within the a determinant of the surface protein has raised the possibility that such variants represent neutralization escape mutants. We previously demonstrated that one such mutant HBV, strain AS, with an arginine substituted for glycine at surface gene codon 145, was infectious and pathogenic in seronegative chimpanzees. In the present study, the protective efficacy of licensed hepatitis B vaccines was evaluated against challenge with this mutant virus. Four chimpanzees were immunized with 1 of 2 licensed recombinant hepatitis B vaccines. Shortly after the chimpanzees developed antibodies to hepatitis B surface antigen (anti-HBs), they were challenged intravenously with mutant HBV strain AS. Two unvaccinated chimpanzees served as positive controls. The 4 vaccinated chimpanzees did not develop evidence of HBV infection or hepatitis during 2 years following virus challenge. In contrast, the 2 unvaccinated chimpanzees developed HBV infection and hepatitis. Serum anti-HBs in the vaccinated chimpanzees reacted not only with wild-type surface antigen, but also with mutant surface antigen by competition enzyme-linked immunosorbent assay (ELISA). Thus, immunization of chimpanzees with licensed recombinant hepatitis B vaccines stimulates anti-HBs that is broadly reactive and affords protection against infection with a surface gene mutant of HBV, suggesting that properly immunized individuals are not at significant risk of infection with this prototype variant strain of HBV.

Evidence for widespread infection of wild rats with hepatitis E virus in the United States

Hepatitis E is an important medical pathogen in many developing countries but is rarely reported from the United States, although antibody to hepatitis E virus (anti-HEV) is found in > 1% of U.S. citizens. Zoonotic spread of the virus is suspected. Sera obtained from 239 wild rats trapped in widely separated regions of the United States were tested for anti-HEV. Seventy-seven percent of rats from Maryland, 90% from Hawaii, and 44% from Louisiana were seropositive for anti-HEV. Rats from urban as well as rural areas were seropositive and the prevalence of anti-HEV IgG increased in parallel with the estimated age of the rats, leading to speculation that they might be involved in the puzzling high prevalence of anti-HEV among some U.S. city dwellers. The discovery of a in rats in the United States and the recently reported discovery that HEV is endemic in U.S. swine raise many questions about transmission, reservoirs, and strains of HEV in developed countries.

Phylogenetic analysis of hepatitis E virus isolates from India (1976-1993)

Seventeen Indian hepatitis E virus (HEV) isolates, representing epidemic and sporadic hepatitis E cases during 1976-1991, were sequenced in the RNA polymerase (RNAP) region. Five isolates were also sequenced in the non-structural hypervariable region of open reading frame 1. Open reading frames 2 and 3 were sequenced only for the prototype isolate. On the basis of the comparison of all the available sequences of the conserved RNAP region, the HEV isolates were divided into three genotypes, differing from each other by >15%. Genotype I included African and Asian isolates, whereas II and III were represented by Mexican and US isolates, respectively. Genotype I was further divided into four sub-genotypes. The majority of the Indian isolates (15/20), along with the Burmese and Nepali isolates, belonged to genotype IA. Genotype IB included HEV isolates from China, Pakistan and the former USSR and 2/20 Indian isolates, which represented the oldest (1976) HEV sequenced so far. Genotype IC included both the African isolates, whereas 3/20 Indian isolates formed genotype ID. Nucleotide sequence analysis of other regions of the HEV genome also placed isolates in the same genotypes. Both the Indian cities experiencing second HEV epidemics, after intervals of 8 and 10 years, showed shifts in the sub-genotypes found; from IB (Ahm-76) to IA (Ahm-84) and from IA (Kol-81) to ID (Kol-91). However, no major shift in the genotypes was noted. Overall, HEV genotypes appear to be segregated geographically.

Route and method of delivery of DNA vaccine influence immune responses in mice and non-human primates

BACKGROUND

In spite of the large number of studies that have evaluated DNA-based immunization, few have directly compared the immune responses generated by different routes of immunization, particularly in non-human primates. Here we examine the ability of a hepatitis B surface antigen (HBsAg)-encoding plasmid to induce immune responses in mice and non-human primates (rhesus monkeys: Macaca mulatta) after delivery by a number of routes.

MATERIALS AND METHODS

Eight different injected [intraperitoneal (IP), intradermal (ID), intravenous (IV), intramuscular (IM), intraperineal (IPER), subcutaneous (SC), sublingual (SL), vaginal wall (VW)] and six noninjected [intranasal inhalation (INH), intranasal instillation (INS), intrarectal (IR), intravaginal (IVAG), ocular (Oc), oral feeding (oral)] routes and the gene gun (GG) were used to deliver HBsAg-expressing plasmid DNA to BALB/c mice. Sera were assessed for HBsAg-specific antibodies (anti-HBs, IgG, IgG1, IgG2a) and cytotoxic T lymphocyte (CTL) activity measured. Three of the most commonly used routes (IM, ID, GG) were compared in rhesus monkeys, also using HBsAg-expressing vectors. Monkeys were immunized with short (0-, 4- and 8-week) or long (0-, 12- and 24-week) intervals between boosts, and in the case of GG, also with different doses, and their sera were assessed for anti-HBs.

RESULTS

In one study, anti-HBs were detected in plasma of mice treated by five of eight of the injected and none of the six noninjected routes. The highest levels of anti-HBs were induced by IM and IV injections, although significant titers were also obtained with SL and ID. Each of these routes also induced CTL, as did IPER and VW and one noninjected route (INH) that failed to induce antibodies. In a second study, GG (1.6 microg) was compared to ID and IM (100 microg) delivery. Significant titers were obtained by all routes after only one boost, with the highest levels detected by IM. Delivery to the skin by GG induced exclusively IgG1 antibodies (Th2-like) at 4 weeks and only very low IgG2a levels at later times; ID-immunized mice had predominantly IgG1 at 4 weeks and this changed to mixed IgG1/IgG2a over time. Responses with IM injection (in the leg or tongue) were predominantly IgG2a (Th1-like) at all times. IV injection gave mixed IgG1/IgG2a responses. In monkeys, in the first experiment, 1 mg DNA IM or ID at 0, 4, and 8 weeks gave equivalent anti-HB titers and 0.4 microg at the same times by GG induced lower titers. In the second experiment, 1 mg DNA IM or ID, or 3.2 microg by GG, at 0, 12, and 24 weeks, gave anti-HB values in the hierarchy of GG > IM > ID. Furthermore, high titers were retained after a single immunization in mice but fell off over time in the monkeys, even after boost.

CONCLUSIONS

Route of administration of plasmid DNA vaccines influences the strength and nature of immune responses in mice and non-human primates. However, the results in mice were not always predictive of those in monkeys and this is likely true for humans as well. Optimal dose and immunization schedule will most likely vary between species. It is not clear whether results in non-human primates will be predictive of results in humans, thus additional studies are required. http://link.springer-ny.com/link/service/journals/00020/bibs /5n5p287. html

DNA immunization of mice and macaques with plasmids encoding hepatitis C virus envelope E2 protein expressed intracellularly and on the cell surface

We analyzed the humoral immune response elicited by hepatitis C virus (HCV) E2 protein expressed in vivo after injection of plasmid DNA into mice and rhesus macaques. Three plasmids were used for immunization: a plasmid containing the entire sequence of the E2 and p7 genes (pE2); a plasmid encoding a truncated form of the E2 protein targeted to the cell surface (pE2surf); a control plasmid (pDisplay) lacking an HCV insert. Each plasmid was injected intramuscularly into 5 mice and intraepidermally (via gene gun) into 5 mice. Immunization was repeated three times at three week intervals. Five macaques were injected intramuscularly (two with pE2, two with pE2surf and one with pDisplay) and immunization was repeated after 8 weeks. All mice immunized via gene gun with pE2 or pE2surf developed anti-E2. The animals immunized with pE2surf developed an earlier and stronger humoral immune response than those immunized with pE2. Only 2 of the mice injected by the intramuscular route, both immunized with pE2surf, developed detectable anti-E2. One of the two macaques immunized with pE2 and both macaques immunized with pE2surf developed anti-E2; the humoral immune response was much stronger in the animals immunized with pE2surf. Our results suggest that presentation of HCV E2 on the cell surface may increase its immunogenicity while preserving its ability to react with antibodies generated during a natural infection.

Experimental transmission of hepatitis C virus-associated fulminant hepatitis to a chimpanzee

Hepatitis C virus (HCV) was transmitted from a patient with fulminant hepatitis C to a chimpanzee. The patient had developed two episodes of fulminant hepatitis C, each occurring after a separate liver transplantation. Serial serum and liver samples from the patient and the chimpanzee were analyzed for HCV replication, genotype, quasispecies heterogeneity, and antibodies. In the patient, the levels of HCV replication in serum and liver correlated with the degree of hepatocellular necrosis and the clinical expression of fulminant hepatitis. The same HCV strain, genotype 1a, was recovered from both episodes of fulminant hepatitis. An unusually severe acute hepatitis was also observed in the chimpanzee. The viruses recovered from the patient and the chimpanzee were almost identical and displayed relatively little quasispecies heterogeneity. Thus, the same HCV strain induced two episodes of fulminant hepatitis in a single patient and severe hepatitis in a chimpanzee, suggesting that the pathogenicity or virulence of a specific HCV strain may be important in the pathogenesis of fulminant hepatitis C.