Follow-up of hepatitis C virus infection in chimpanzees: determination of viraemia and specific humoral immune response

Cytokine profile and viral diversity in the early seronegative stage of community-acquired hepatitis C virus (HCV) infection

Most Hepatitis C virus (HCV)-infected subjects develop chronic infection, whereas a minority clear the virus in the early phase of infection. We analyzed factors associated with outcome (chronicity vs clearance) during the preclinical seronegative phase of community-acquired HCV infection. Among 17.5 million blood donations in the years 2000-2016, 124 blood donors were found to be HCV RNA-positive/anti-HCV-negative. All were contacted after 0.5-12.7 years and 40 responded and provided blood sample. Hypervariable region 1 was analyzed by ultradeep pyrosequencing and cytokines in serum were quantified by Luminex (R&D Systems) multiplex immunoassay. Twenty-one (52.5%) donors were found to be HCV-RNA-positive, while 19 (47.5%) were HCV RNA negative (none received antiviral treatment). All but one seroconverted to anti-HCV. Donors with resolving hepatitis did not differ significantly from donors with chronic infection with respect to age, genotypes, IL28B polymorphisms, number of viral variants, nucleotide diversity per site or the overall number of nucleotide substitutions. However, the former group had significantly higher levels of IL-1beta, IL-1RA, IL-6, IFN-gamma and FGF-2 in serum. In our study of community-acquired acute hepatitis C approximately half of all subjects eliminated the virus spontaneously, and this clearance was associated with marked cytokine response in the early seronegative stage of infection.

T-bet-expressing B cells during HIV and HCV infections

T-bet-expressing B cells, first identified as perpetuators of autoimmunity, were recently shown to be critical for murine antiviral responses. While their role in human viral infections remains unclear, B cells expressing T-bet or demonstrating a related phenotype have been described in individuals chronically infected with HIV or HCV, suggesting these cells represent a component of human antiviral responses. In this review, we discuss the induction of T-bet in B cells following both HIV and HCV infections, the factors driving T-bet⁺ B cell expansions, T-bet's relationship to atypical memory B cells, and the consequences of T-bet induction. We propose potential antiviral roles for T-bet⁺ B cells and discuss whether this population poses any utility to the HIV and HCV immune responses.

Immunopathogenesis of Hepatitis C Virus Infection

Despite advances in therapy, hepatitis C virus infection remains a major global health issue with 3 to 4 million incident cases and 170 million prevalent chronic infections. Complex, partially understood, host-virus interactions determine whether an acute infection with hepatitis C resolves, as occurs in approximately 30% of cases, or generates a persistent hepatic infection, as occurs in the remainder. Once chronic infection is established, the velocity of hepatocyte injury and resultant fibrosis is significantly modulated by immunologic as well as environmental factors. Immunomodulation has been the backbone of antiviral therapy despite poor understanding of its mechanism of action.

Relationship between humoral response against hepatitis C virus and disease overcome

Abstract

Hepatitis C virus infection leads to liver disease whose severity can range from mild to serious lifelong illness. However the parameters involved in the evolution of the disease are still unknown. Among other factors, the virus-elicited antibody profile is suspected to play a role in the outcome of the disease. Analysis of the relationship between anti-virus antibodies and disease state requires the analysis of a large number of serums from patients (hepatitis C virus+) and of epitopes from the viral proteins. Such a study would benefit from microarray-based screening systems that are appropriate for high-throughput assays.

We used a method combining peptide chips and surface plasmon resonance imaging previously shown to be suitable for analyzing complex mediums and detecting peptide-protein interactions. 56 peptides covering the entire viral proteome were grafted on chips and their interaction with antibodies present in the 68 injected serums from infected and non-infected donors was measured. Statistical analyses were conducted to determine a possible relationship between antibodies (specificity and amount) and disease states.

A good discrimination between infected and non-infected donors validated our approach, and several correlations between antibodies profiles and clinical parameters have been identified. In particular, we demonstrated that ratios between particular antibodies levels allow for accurate discrimination of patients according to their pathologic states.

Conclusion

Humoral response against hepatitis C virus linear epitopes is partly modified according to the disease state. This study highlights the importance of considering relative quantities of antibodies with different specificities rather than the amount of each antibody.

Electronic supplementary material

The online version of this article (doi: 10.1186/2193-1801-3-56) contains supplementary material, which is available to authorized users.

The status of liver transplantation for hepatitis C

The hepatitis C virus (HCV) infects 3% of the world's population, or approximately 170 million people. Most of those acutely infected progress to chronic infection and are unresponsive to existing antiviral treatment. Over a 20-year period, chronic HCV infection leads to cirrhosis and the sequelae of end-stage liver disease, including hepatic encephalopathy, ascites, variceal haemorrhage and hepatocellular carcinoma. Orthotopic liver transplantation (OLT) is the optimal treatment for decompensated HCV cirrhosis, but is limited by organ availability and universal graft reinfection. This review discusses the results with OLT for HCV from the Dumont-UCLA Liver Transplant Center and discusses future directions in the management of HCV.

Selection of different 5' untranslated region hepatitis C virus variants during post-transfusion and post-transplantation infection

BACKGROUND

Hepatitis C virus (HCV) translation is initiated in a cap-independent manner by an internal ribosome entry site (IRES) located within the 5' untranslated region (5'UTR). Sequence changes in this region could affect translation efficiency and presumably viral replication.

AIM

To determine translation efficiency of 5'UTR variants developing during post-transfusion hepatitis C in two immunocompetent subjects and in two immunosuppressed liver recipients with recurrent HCV.

METHODS

Sequential samples were screened for 5'UTR changes by single-strand conformation polymorphism followed by cloning and sequencing whenever band pattern suggested sequence changes. 5'UTR variants were tested for IRES activity using a bicistronic dual luciferase expression plasmid transfected into HepG2 and Huh7 cell-lines.

RESULTS

In the transfused patients, translation efficiency of 5'UTR variants from early post-transfusion samples was 5.1- to 13.7-fold higher than that of predominant variants found in late follow-up samples. Post-transplant variants in the other two patients had 2.6- to 5.9-fold higher translation efficiency than those present only in pretransplant samples.

CONCLUSION

In the immunocompetent host there may be selection of low translation efficiency HCV variants over the course of infection. However, in immunosuppressed subjects the opposite seems to be true as low translation efficiency variants are superseded by high translation efficiency variants.

Humoral immune response in acute hepatitis C virus infection

BACKGROUND

There is little information on the timing, magnitude, specificity, and clinical relevance of the antibody response to acute hepatitis C virus (HCV) infection. We investigated the specificity, titer, and neutralizing potential of antibody responses to acute infection by examining 12 injection drug users before, during, and after infection.

METHODS

Seroconversion was defined as incident detection of HCV-specific antibodies by using a commercially available enzyme-linked immuosorbent assay (ELISA). HCV protein-specific antibody responses were measured using recombinant antigens in an ELISA. For neutralization assays, plasma was incubated with human immunodeficiency virus (HIV)-HCV H77 or control HIV-murine leukemia virus (MLV) pseudotype virus and then allowed to infect Hep3B hepatoma cells.

RESULTS

The mean time to HCV seroconversion was 6 weeks after the onset of viremia. Antibody responses to nonstructural proteins were detected before responses to the structural proteins, and antibodies to both were primarily restricted to the immunoglobulin G1 (IgG1) subclass. The maximum median end point titers for antibody responses to structural and nonstructural proteins were 1 : 600 and 1 : 6400, respectively. Antibodies that neutralized a retroviral pseudotype bearing HCV 1a envelope glycoproteins were detected at seroconversion in only 1 subject and at 6-8 months after seroconversion in 3 subjects. The delayed appearance of neutralizing antibodies was consistent with the late development of antibodies specific for the viral envelope glycoproteins, which are believed to mediate virus neutralization.

CONCLUSION

The humoral immune response to acute HCV infection is of relatively low titer, is restricted primarily to the IgG1 subclass, and is delayed. A better understanding of why production of neutralizing antibody is delayed may improve efforts to prevent HCV infection.

Evaluation of five hepatitis C virus screening tests and two supplemental assays: performance when testing sera from sexually transmitted diseases clinic attendees in the USA

The performances of five screening tests (recombinant peptide-based first and second generation tests from Abbott and Ortho, and a synthetic peptide-based test from Biochem Immunosystems) and two supplemental tests: recombinant peptide- based, Abbott neutralization test and Chiron second generation recombinant immunoblot assay (RIBA 2), were evaluated for their ability to detect hepatitis C virus (HCV) antibodies in a population of 276 individuals attending a sexually transmitted diseases (STD) clinic in the USA. Although the five screening tests produced a variable number (35-62) of repeatedly reactive samples, only 13% (36/276) were classified as true positives by the supplemental tests. Thirty-four of the 36 were reactive by all screening tests and 32 of the true positives were reactive by both supplemental tests, while 2 did not neutralize but were reactive in the RIBA 2 test. Of the remaining 2 of the true positives which were discordant by several of the screening assays, 1 was confirmed by both supplemental assays but the other required a chemiluminescent enhancement technique to show positivity in RIBA 2. The sensitivities of the first and second generation Abbott and Ortho tests ranged from 97% to 100% and that of the Biochem test was 94%. The specificities of these tests ranged from 89.2% to 99.6%. The second generation Ortho test presented 9.4% (26/276) false positives. The use of second generation Ortho as a screening test would lead to an excessive number of confirmatory false positives. the positive predictive values of the screening tests ranged from 58.1% to 97.1%. Although the synthetic peptide based Biochem test exhibited the best overall indices, the presence of 2 false negative results would prevent its use as a singular screening test. Nevertheless its high specificity may lend itself to be used as a second screening test before confirmatory testing with RIBA 2.

Accumulation of B lymphocytes with a naive, resting phenotype in a subset of hepatitis C patients

Chronic infection with hepatitis C virus (HCV) is associated with disturbances of B lymphocyte activation and function: autoantibody production, mixed cryoglobulinemia, and B cell lymphomas. It has been proposed that these abnormalities reflect chronic antigenic stimulation or aberrant signaling through the B cell coreceptor, the latter mediated by binding of the HCV E2 glycoprotein to CD81. To test this hypothesis, we measured expression of activation and differentiation markers on peripheral blood B cells from patients with chronic HCV infection. Thirty-six HCV patients with and without mixed cryoglobulinemia were compared with 18 healthy control volunteers and 17 sustained virologic responders who had cleared HCV infection. Ten of the 36 HCV patient samples showed increased B cell frequencies; B cell frequency was higher in patients with more severe hepatic fibrosis. However, these samples lacked evidence of Ag-driven activation or proliferation. The expanded cells were low in the activation markers CD25, CD69, CD71, CD80, and CD86. Proliferation of circulating B cells was unchanged in HCV patients. These cells did not express the differentiation marker CD27, suggesting that they were not enriched in memory B cells. Furthermore, the expanded B cells expressed both IgD and IgM, suggesting that they were antigenically naive. Together, these results indicate that B cell expansion in the peripheral blood of HCV patients is not associated with Ag-mediated activation and differentiation. Instead, factors other than antigenic stimulation may promote the accumulation of peripheral blood B cells with a naive phenotype in a subset of HCV patients.

Lack of susceptibility of Chacma baboons (Papio ursinus orientalis) to hepatitis C virus infection

The main reason to ascertain whether baboons are susceptible to infection with hepatitis C virus (HCV) is the need to replace chimpanzees, which are endangered, as an animal model for undertaking research into the biology and host-virus interactions of HCV, and for developing a vaccine against this virus. A second reason is that baboons are a possible source of xenografts for human liver transplantation. We inoculated serum containing HCV into four Chacma baboons and monitored them for 52 weeks for evidence of infection. Serum was tested for antibody to HCV, HCV RNA, and aminotransferase concentrations at 2-week intervals for 26 weeks and thereafter at 4-week intervals. Liver tissue was examined at 28 and 52 weeks for histopathological changes and viral RNA, and at 52 weeks for viral particles using electron microscopy. Reverse transcription-polymerase chain reaction assay was used to detect HCV RNA, and the results were confirmed by Southern hybridization. Serum aminotransferase concentrations remained within the normal range and liver histology was normal during the follow-up period. Passive transmission of anti-HCV to the baboons was observed during the first 4 weeks. HCV RNA was not detectable in any serum or liver sample and electron microscopy failed to reveal viral particles in liver tissue. In conclusion, we did not find Chacma baboons to be susceptible to infection with HCV, although we cannot deny that in an immunosuppressed liver transplant recipient, infection of a baboon xenograft might occur. Another animal model for HCV infection must be sought.

Changes in hepatitis C virus population in serum and peripheral blood mononuclear cells in chronically infected patients receiving liver graft from infected donors

BACKGROUND

We have previously studied hepatitis C (HCV)-infected recipients of livers from HCV-infected donors and found that either the donor's strain or the recipient's strain predominate in serum. The current study was undertaken to determine whether these changes are complete and whether they are reflected in the population of virus associated with peripheral blood mononuclear cells (PBMCs).

METHODS

We analyzed HCV ribonucleic acid from sequential serum and PBMC samples from 11 and 8 patients, respectively. The relatively stable NS5 region was chosen for analysis because it allowed for dependable identification of donor and recipient strains. Viral sequences were analyzed by direct sequencing and by sensitive strain-specific polymerase chain reaction assays. These assays were capable of detecting the minor sequence present at a concentration 1:104-10-7 below that of the major sequence.

RESULTS

Five patients retained their original infecting strain; the donor strain was detected only transiently. In the remaining six patients, recipient strain was detected for the first few weeks, after which only the donor strain was consistently present. However, in one patient the second nondominant strain was detected from the background of the major strain on a single occasion 8 months after transplantation. All changes in serum were closely paralleled by those occurring in PBMCs.

CONCLUSIONS

Viral population changes in the setting of liver transplantation from HCV-infected donors to HCV-infected recipients occur simultaneously in PBMCs and serum. The takeover of one strain by another in PBMC- and serum-derived viral populations seemed to be complete and long lasting.

Differences in HCV antibody patterns in haemodialysis patients infected with the same virus isolate

Eight cases of de novo hepatitis C virus (HCV) infection in a haemodialysis unit in Rio de Janeiro, Brazil, were retrospectively studied. HCV viraemia was demonstrated by RT nested PCR in seven of the seroconverters. Genotyping showed that six patients were infected with a genotype 1b strain and one with a genotype 1a strain. A phylogenetic analysis of nucleotide sequences of the HCV core region revealed that five of the six 1b isolates form a separate cluster when compared with other 38 HCV 1b core sequences randomly chosen from the GenBank. The revealed sequence similarities indicated the nosocomial spread of a single HCV strain within the unit. To investigate whether the patients infected with the same viral isolate display similar patterns of antibody response to individual proteins, serial serum samples were examined. A line immunoassay for qualitative and semi-quantitative determination of specific antibodies against recombinant and synthetic HCV antigens was employed. Despite infection with the same virus strain, the patients sera demonstrated different patterns of reactivity against individual structural and nonstructural HCV proteins immediately after seroconversion. For each patient, however, antibody responses remained mostly stable throughout the follow-up of 8 to 24 months.

Priming of hepatitis C virus-specific cytotoxic T lymphocytes in mice following portal vein injection of a liver-specific plasmid DNA

The immunology of hepatitis C virus (HCV) infection should be studied in the context of HCV antigen expression in the liver, because HCV primarily infects this organ. Indeed, the nature, function, and fate of T cells primed after antigen expression in the liver might differ from those primed when antigens are expressed systemically or in other organs, because the nature of the antigen-presenting cells (APCs) involved may be different. In addition, the normal liver contains a resident population of lymphocytes that differ from those present at other sites. Thus, we investigated whether HCV-specific CD8(+) cytotoxic T cells (CTLs) could be elicited following portal vein (PV) injection of plasmid DNA in mice whose hepatic veins were transiently occluded. We show that PV injection of mice with "naked" DNA expressing the HCV-NS5a protein, under the control of a liver-specific enhancer/promoter, resulted in NS5a expression in the liver and the priming of HCV-specific CTLs. These results suggested that such a model might be relevant to the study of HCV-specific immune responses primed during natural infection.

Viral persistence, antibody to E1 and E2, and hypervariable region 1 sequence stability in hepatitis C virus-inoculated chimpanzees

The relationship of viral persistence, the immune response to hepatitis C virus (HCV) envelope proteins, and envelope sequence variability was examined in chimpanzees. Antibody reactivity to the HCV envelope proteins E1 or E2 was detected by enzyme-linked immunosorbent assay (ELISA) in more than 90% of a human serum panel. Although the ELISAs appeared to be sensitive indicators of HCV infection in human serum panels, the results of a cross-sectional study revealed that a low percentage of HCV-inoculated chimpanzees had detectable antibody to E1 (22%) and E2 (15%). Viral clearance, which was recognized in 28 (61%) of the chimpanzees, was not associated with an antibody response to E1 or E2. On the contrary, antibody to E2 was observed only in viremic chimpanzees. A longitudinal study of animals that cleared the viral infection or became chronically infected confirmed the low level of antibody to E1, E2, and the HVR-1. In 10 chronically infected animals, the sequence variation in the E2 hypervariable region (HVR-1) was minimal and did not coincide with antibody to E2 or to the HVR-1. In addition, low nucleotide and amino acid sequence variation was observed in the E1 and E2 regions from two chronically infected chimpanzees. These results suggest that mechanisms in addition to the emergence of HVR-1 antibody escape variants are involved in maintaining viral persistence. The significance of antibodies to E1 and E2 in the chimpanzee animal model is discussed.

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.

Analysis of hepatitis C virus-inoculated chimpanzees reveals unexpected clinical profiles

The clinical course of hepatitis C virus (HCV) infections in a chimpanzee cohort was examined to better characterize the outcome of this valuable animal model. Results of a cross-sectional study revealed that a low percentage (39%) of HCV-inoculated chimpanzees were viremic based on reverse transcription (RT-PCR) analysis. A correlation was observed between viremia and the presence of anti-HCV antibodies. The pattern of antibodies was dissimilar among viremic chimpanzees and chimpanzees that cleared the virus. Viremic chimpanzees had a higher prevalence of antibody reactivity to NS3, NS4, and NS5. Since an unexpectedly low percentage of chimpanzees were persistently infected with HCV, a longitudinal analysis of the virological profile of a small panel of HCV-infected chimpanzees was performed to determine the kinetics of viral clearance and loss of antibody. This study also revealed that a low percentage (33%) of HCV-inoculated chimpanzees were persistently viremic. Analysis of serial bleeds from six HCV-infected animals revealed four different clinical profiles. Viral clearance with either gradual or rapid loss of anti-HCV antibody was observed in four animals within 5 months postinoculation. A chronic-carrier profile characterized by persistent HCV RNA and anti-HCV antibody was observed in two animals. One of these chimpanzees was RT-PCR positive, antibody negative for 5 years and thus represented a silent carrier. If extrapolated to the human population, these data would imply that a significant percentage of unrecognized HCV infections may occur and that silent carriers may represent potentially infectious blood donors.

Comparative features of hepatitis C virus infection in humans and chimpanzees

Several features of human HCV infection are recapitulated in the chimpanzee model. Most importantly, the frequency of persistent infection is high in both species, and virus replication occurs despite evidence of cellular and humoral immune responses. A key difference is that necroinflammatory lesions in chronically infected chimpanzees are almost always mild, whereas in humans the disease spectrum is very wide, ranging from mild to severe hepatitis and end-stage cirrhosis requiring transplantation. Understanding the basis for both the similarities and differences in persistent hepatitis C in the two species will probably be important for the development of effective prevention and therapy of HCV infection.

Present and Future Prospects for Using Alternatives to Chimpanzees in Research

Three chimpanzee studies of hepatitis C infection were found to be duplicative of each other and of research with human volunteers. Research into taste neurophysiology also used chimpanzees, although data which are highly relevant (but less specific) can be obtained from human studies. The use of chimps to study benzene metabolism was found to be poorly planned and unjustifiable. Scientifically, chimps are not always the best “models” for humans, and their use raises insurmountable ethical concerns. Many alternatives are already available, but researchers will need to adjust their perspectives on the usefulness of different types of data.

Hepatitis C virus: historical perspective and current concepts

Over the past 30 years, hepatitis C has emerged from shadowy enigma to important public health problem. The existence of the etiological agent of this disease was first appreciated two decades ago but significant progress in its understanding had to await its molecular characterization within the past 5 years. The virus is a member of the family Flaviviridae and is the cause of approximately 20% of clinical viral hepatitis in the United States. While the control of the transmission of hepatitis C virus in blood and blood products has been nothing less than spectacular, the control of community-acquired hepatitis C will be a major challenge to the scientific and medical communities.

Importance of the polymerase chain reaction in the study of hepatitis C virus infection

Recently, the principal etiological agent of parenterally transmitted non-A, non-B hepatitis was molecularly cloned from the plasma of an experimentally infected chimpanzee and has been named hepatitis C virus. Determination of the complete nucleotide sequence of the hepatitis C virus genome was a crucial step in preparing the way for future study of this medically important human pathogen. Due to the very low concentration of virus in serum, amplification of viral RNA sequences by reverse transcription and polymerase chain reaction is the only practical method currently available for demonstrating viremia in patients with hepatitis C virus infection. This review examines the pivotal role of the polymerase chain reaction in understanding the biology of hepatitis C virus.