Hepatitis C virus-specific T-cell immune responses in seronegative injection drug users

Summary.  T-cell responses to hepatits C virus (HCV) antigens have been reported in high-risk HCV seronegative persons, suggesting that an effective cellular immune response might be able to clear infection without the development of antibodies. Such findings, however, could be explained by waning antibody or cross-reactivity to other antigens. To address these issues, we evaluated HCV-specific T-cell responses in 26 young (age 18–33 years) aviremic, seronegative injection drug users (IDUs) (median duration of injection, 6 years) by interferon-γ enzyme-linked immunospot (ELISpot) assay using 429 overlapping HCV peptides pooled in 21 mixes. Seventeen aviremic, seropositive IDUs (spontaneous resolvers) and 15 healthy people were used as positive and negative controls, respectively. The percentage of patients with HCV-specific cellular immune responses was similar in seronegative and seropositive aviremic IDUs (46% vs 59%, P  = 0.4), while these responses were not detected in any of the negative controls. Among the seronegative IDUs, six (23%) had intermediate to very strong responses to 10–20 peptide mixes and another six (23%) had moderately strong responses for two to six mixes. The 12 seronegative IDUs with HCV-specific T-cell responses had higher demographical and behavioural risk profiles than the 14 IDUs without T-cell responses (estimated risk of HCV infection, 0.47 vs 0.26, P  < 0.01). In conclusion, HCV-specific T-cell responses are common among high-risk, seronegative IDUs. The responses are broad and are associated with risk factors for HCV exposure, suggesting that they reflect true exposure to HCV in seronegative persons.     

Hepatitis C virus-like particles induce virus-specific humoral and cellular immune responses in mice

We have recently described the production of hepatitis C virus-like particles (HCV-LPs) in insect cells that resemble the putative virions. Here we evaluate the humoral and cellular immunogenicity of the virus-like particles with or without viral p7 protein, a small viral polypeptide that resides between the structural and nonstructural regions of the HCV polyprotein and whose function has not been defined. Immunized BALB/c mice developed high titers of anti-E2 antibodies and virus-specific cellular immune responses including cytotoxic T lymphocytes and T helper responses with gamma interferon production. The virus-like particles without p7 generated a higher cellular immune response with a more T(H)1 profile than the particles with p7. Immunization of heat-denatured particles resulted in substantially lower humoral and cellular responses, suggesting that the immunogenicity is strongly dependent on particle formation. Administration of CpG oligonucleotide or cationic lipid 3beta-[N-(N',N'-dimethylaminoethane)carbamoyl]cholesterol (DC-Chol), two potent adjuvants, did not significantly enhance the immunogenicity of HCV-LPs. Our results indicate that HCV-LPs can induce humoral and cellular immune responses and offer a promising approach to vaccine development.     

Hepatitis C virus-like particles combined with novel adjuvant systems enhance virus-specific immune responses

We have previously described the generation of hepatitis C virus-like particles (HCV-LPs) in insect cells and shown that immunization with HCV-LPs elicited both humoral and cellular immune responses in mice. To further characterize the HCV-LPs as a vaccine candidate, we evaluated the effects of adjuvant AS01B (monophosphoryl lipid A [MPL] and QS21), CpG 10105, and the combination of the 2 adjuvants on the immunogenicity of HCV-LPs in AAD mice (transgenic for HLA-A2.1). All HCV-LP-immunized mice (with or without adjuvant) developed high titers of anti-HCV E1/E2 antibodies after 4 injections intramuscularly. However, antibody titers in mice immunized with HCV-LP plus AS01B, plus CpG 10105, or plus the combination of AS01B and CpG 10105 were 4, 3, and 10 times higher, respectively, than that of HCV-LP alone. Isotype analysis of the induced anti-envelope antibodies showed that HCV-LP alone induced a predominant immunoglobulin (Ig) G1 response. In contrast, when the 2 adjuvants AS01B and CpG 10105 were combined, the response became predominantly IgG2a whereas HCV-LP plus AS01B or CpG 10105 gave a mixed IgG1 and IgG2a response, indicating that AS01B and CpG 10105 promote a more T-helper type 1 (Th1) response and that combining the 2 adjuvants results in an additive or synergistic interaction. These observations were further confirmed by the results of CD4(+) enzyme-linked immunospot assay for interferon (IFN)-gamma and interleukin (IL)-4 and intracellular cytokine staining of IFN-gamma producing CD8(+) cells. In conclusion, HCV-LP is a promising vaccine candidate against HCV infection and the adjuvants used are potent immune enhancers for this approach.     

Early IL‐10 predominant responses are associated with progression to chronic hepatitis C virus infection in injecting drug users

Summary. The critical events in clearance or persistence of hepatitis C virus (HCV) infection are unknown but likely to be determined early in acute infection. Type 1 and type 2 cytokine production was assessed by HCV peptide ELISpot and multiplex in vitro cytokine production assays in longitudinally collected samples from 20 untreated participants enrolled in the Australian Trial in Acute Hepatitis C (ATAHC); a prospective cohort of acute HCV infection (77% injecting drug users, IDU). Significantly higher interleukin‐10 (IL‐10) production (P = 0.048), in the relative absence of interferon‐gamma (IFN‐γ) and IL‐2 production, was present early in HCV infection in those who progressed to chronic infection. In contrast, viral clearance was associated with a greater magnitude and broader specificity of IFN‐γ (magnitude P < 0.001, breadth P = 0.004) and IL‐2 responses, in the relative absence of IL‐10. Early IL‐10 production was correlated with higher HCV RNA level at baseline (P = 0.046) and week 12 (P = 0.018), while IFN‐γ and IL‐2 production was inversely correlated with HCV RNA level at baseline (IFN‐γP = 0.020, IL‐2 P = 0.050) and week 48 (IFN‐γP = 0.045, IL‐2 P = 0.026). Intracellular staining (ICS) indicated the HCV‐specific IFN‐γ response was primarily from CD8⁺ T cells and NK cells, whereas IL‐10 production was predominantly from monocytes, with a subset of IL‐10 producing CD8⁺ T cells present only in those who progressed to chronic infection. IL‐10, an immunoregulatory cytokine, appears to play a key role in progression to chronic HCV infection.     

Hepatitis C virus (HCV)-specific immune responses of long-term injection drug users frequently exposed to HCV

BACKGROUND: Injection drug users (IDUs) who successfully clear hepatitis C virus (HCV) have a reduced risk of developing chronic reinfection, despite their continuing exposure to the virus. To identify immunological correlates for this apparent protection, we studied HCV-specific immune responses in long-term IDUs (duration, >10 years). METHODS: HCV-specific T cell responses were assessed in proliferation, enzyme-linked immunospot (ELISPOT), interferon (IFN)-gamma secretion, and cytotoxicity assays, whereas HCV-specific antibodies were assessed in enzyme immunoassays (EIAs), chemiluminescent assays, and in vitro neutralization assays. RESULTS: HCV-specific T cell proliferation and IFN-gamma production were more common in nonviremic EIA-positive IDUs (16 [94%] of 17 IDUs) than in viremic EIA-positive IDUs (9 [45%] of 20 IDUs) (P= .003). They were also noted in 16 (62%) of 26 nonviremic EIA-negative IDUs. In contrast, 19 (90%) of 21 viremic IDUs displayed neutralizing antibodies (nAbs), compared with 9 (56%) of 16 nonviremic EIA-positive IDUs (P= .04) and 0 of 24 nonviremic EIA-negative IDUs. Nonviremic IDUs with nAbs were older (P= .0115) than those without nAbs, but these groups did not differ in terms of either injection drug use duration or HCV-specific T cell responses. CONCLUSION: The reduced risk of HCV persistence in IDUs previously recovered from HCV infection correlated with T cell responses, and prolonged antigenic stimulation appears to be required to maintain humoral responses.     

Hepatitis C virus reinfection in injection drug users

Spontaneous clearance of hepatitis C (HCV) may provide protection against reinfection. In a large community-based cohort study of 3,553 inner-city residents (mainly injection drug users), we identified HCV-infected individuals in whom virological clearance had occurred and compared the rate of reinfection in this group with that observed in previously uninfected members of the same cohort. We identified 926 HCV-uninfected and 658 HCV-infected viremic subjects at baseline, with 152 of 658 (23.1%) spontaneously clearing viremia over a median follow-up of 5.2 years (IQR, 2.8-7.4). At baseline, individuals with HCV clearance were more likely to be HIV coinfected (P < .001) and to be engaged in frequent illicit drug use (P = .004) and injection drug use (P < .001). The occurrence of HCV infection was lower in individuals with previous infection (14/152, 9.2%) compared with that in those without previous infection (172/926, 18.6%), with incidence rates of 1.8 (95% CI, 0.9-3.0 cases/100 person-years) and 8.1 (95% CI, 6.9-9.4 cases/100 person-years) cases/100 person-years, respectively, after accounting for follow-up. In a logistic regression analysis, with previous HCV infection assessed as a covariate with other potential confounding variables (age, sex, ethnicity, HIV infection, housing status, and illicit and injection drug use), individuals with previous HCV infection and viral clearance were 4 times less likely to develop infection than those infected for the first time (adjusted odds ratio, 0.23; 95% CI, 0.10-0.51, P < .001). In conclusion, individuals with clearance of HCV infection may have a lower risk of acquiring HCV than individuals who have never been infected, despite ongoing exposure to HCV.     

Hepatitis C virus and depression in drug users

Objective: Clinical case studies have implicated depression as a possible side-effect of interferon treatment for the Hepatitis C virus (HCV). However, because these studies generally did not include a pretreatment assessment of depression, it cannot be definitively stated whether depression is a side-effect of interferon treatment, a syndrome coexisting with HCV, or a common characteristic of individuals who are vulnerable to HCV infection. To gather more information about this issue, self-reported depressive symptomatology of drug users with HCV who have not received interferon treatment was compared to that of uninfected drug users.
Methods: Subjects were 309 drug users not currently in substance abuse treatment who were participating in a National Institute on Drug Abuse project. Subjects completed the Center for Epidemiological Studies-Depression (CES-D) instrument and provided a blood sample for HCV testing.
Results: Serological findings revealed that 52.4% of the subjects tested positive for HCV antibodies. Of the HCV-positive subjects, 57.2% had significant depressive symptomatology, whereas only 48.2% of the HCV-negative subjects did, for an overall rate of 52.6%. The two groups also differed on two specific dimensions of depression, with the HCV-positive group scoring lower on the Positive Affect scale and higher on the Somatic/Retarded Activity scale.
Conclusions: These findings reveal high levels of depressive symptomatology among drug users, as well as the possibility of a coexisting depressive syndrome with HCV infection. These findings raise the possibility that depression associated with interferon treatment may, at least partially, be accounted for by preexisting depression. Further research is needed to determine the nature and origins of depression in individuals in treatment with interferon for HCV with specific focus placed on determining the dimensions of depression associated with HCV infection and interferon treatment.     

Hepatitis C infection among drug users in northern Thailand

Illicit drug users are commonly infected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV). We evaluated the prevalence, incidence, and risk behaviors associated with HCV infection in 1,859 drug users in northern Thailand. The HCV prevalence was 27.3%: 86.0% among drug injectors (IDUs) and 5.3% among those who did not inject. Sexual behavior was not significantly associated with HCV among IDUs or drug users who used but didn't inject illicit drugs; only injection behaviors were independently associated with HCV in multivariate analysis. Among men, a history and increasing frequency of injecting drugs, older age, and a history of incarceration were associated with HCV infection. Among 514 opiate users who were HCV and HIV seronegative at baseline, 41 incident HCV infections and 6 HIV infections occurred on follow-up; the HCV incidence was 5.43/100 person-years; it was 44.3/100 person-years in IDUs and 1.9/100 person-years in non-injectors. HCV and HIV among drug users in Thailand are common and primarily associated with injection behavior.     

Isotype-specific characterization of antibody responses to Onchocerca volvulus in putatively immune individuals

Isotypejsubclass-specific antibody responses to adult Onchocerca volvulus extract (OvAg) were assessed by both ELISA and immunoblotting for a group of putatively immune individuals (PIs, n = 29) from a hyperendemic area in Ecuador and for a group of infected individuals (INFs, n = 47) from the same region. As a group, the Pis have been previously shown to possess lower levels of OvAg specific IgG1, IgG2, IgG3 and IgG4 than INFs but semiquantitative analysis revealed that the relative proportions of these subclasses differs between the two groups. The IgG of the PI group contained a higher proportion of IgG3 and a lower proportion of IgG4 than the INF group. The frequency distribution of IgG3 responses was similar for the PI and INF groups. The frequency distributions for IgG1, IgG4 and IgE were significantly different between the PI and INF groups. A subgroup of the Pis were identified from frequency distributions and multivariate plots of individual isotype responses as having antibody responses (mainly IgG4) possibly indicative of cryptic infection. High IgE responses were exclusive to INF individuals, and a rare response type of high IgG3 with negligible levels of other isotypes/subclasses was seen only in the PI group. However, the majority of the Pis had negligible responses for all antibody classes. Immunoblots demonstrated no obvious differences in qualitative recognition between the PIs and INFs.     

Hepatitis C virus-specific immune responses and quasi-species variability at baseline are associated with nonresponse to antiviral therapy during advanced hepatitis C

Pretreatment hepatitis C virus (HCV)-specific lymphoproliferative (LP) responses, neutralizing antibody (NA) responses, intrahepatic cytotoxic T lymphocyte (CTL) responses, and HCV quasi-species (QS) diversity and complexity were examined in patients with advanced hepatic fibrosis (Ishak fibrosis score of > or = 3) and prior nonresponse to interferon (IFN)- alpha therapy who were enrolled in the initial phase of the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis Trial. Positive baseline HCV E1- and/or E2-specific NA responses (P = .01) and higher baseline HCV QS diversity (P = .01) were more commonly found in patients who did not become sustained virologic responders (SVRs) at week 72 (W72) than they were in those who did. No patients with positive results for both the LP and NA assays achieved a sustained virologic response. Multiple logistic regression analysis revealed that, when the presence of cirrhosis, prior ribavirin therapy, genotype 1 infection, log serum HCV RNA level, and receipt of >80% of the prescribed medication were controlled for, a sustained virologic response (W72) was negatively correlated with positive baseline LP assay results (P = .02) and with 1 or more positive assays (LP, NA, or CTL) (P = .02). No differences were noted in baseline intrahepatic CTL activity between SVRs and non-SVRs. Thus, in patients with advanced hepatic fibrosis due to HCV infection, pretreatment HCV-specific immune responses and increased QS variability appear to hinder viral clearance by pegylated IFN- alpha 2a and ribavirin combination therapy.     

Polyomavirus-associated nephropathy: update on BK virus-specific immunity

The human polyomavirus type 1, also called BK virus (BKV), causes polyomavirus-associated nephropathy (PVAN) in 1-10% of renal transplant recipients, with graft loss in over 50% of cases. The risk factors for PVAN are not conclusively defined and likely involve complementing determinants of recipient, graft, and virus. A central element seems to be the failing balance between BKV replication and BKV-specific immune control, which can result from intense triple immunosuppression, HLA-mismatches, prior rejection and anti-rejection treatment, or BKV-seropositive donor/seronegative recipient pairs. Consistent with this general hypothesis, the timely reduction of immunosuppression in kidney transplant recipients reduced graft loss to less than 10% of cases. However, the BKV-specific humoral and cellular immune response is not well characterized. Recent work from several groups suggest that changes in antibody titers and BKV-specific CD4+ and CD8+ T cells may help to better define the risk and the course of PVAN in renal transplant patients.     

Cellular immune responses in transplantation-associated chronic viral infections

Abstract: Viral pathogens are important causes of morbidity following transplantation. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections represent two major viral complications in transplant recipients. Recent advances in methodology have led to a better understanding of host immune responses directed against chronic viral infections. We review the nature of antiviral immunity involved in control of CMV and EBV. Viral mechanisms of immune evasion and immunotherapeutic strategies in the transplantation setting will also be addressed.     

Hepatitis C virus screening in drug users in an addiction out-patient unit

AIM: To investigate the feasibility and efficacy of hepatitis C virus screening in drug users in an addiction out-patient unit. PATIENTS AND METHODS: All patients followed in an addiction out-patient unit were asked to undergo anti-hepatitis C virus antibody testing; further evaluation and treatment if indicated, were offered to positive patients. When treatment was initiated (Metavir score >=F2), patients were followed-up both by the hepatologist and the out-patient unit physician. RESULTS: Between July 1997 and September 2000, 404 consecutive patients (310 men, mean age: 32, alcohol intake >=50 g per day in 51%, 94% in opiate substitution program) were included. Sixty-six per cent (269/404) of patients agreed to undergo HCV antibodies testing: 84% had a positive test. 68% of these patients accepted ALT serum measurement and 120 had indications for liver biopsy. Eighty-eight liver biopsies were performed, showing severe fibrosis (Metavir score F3 or F4) in 20 cases (22%). Ethanol intake was significantly correlated to fibrosis (P<0.05). Antiviral treatment was indicated in 47 patients but was only initiated in 27 due to patient refusal (n=7) or contraindication (n=13). Treatment had to be discontinued in 12 cases because of psychiatric side effects (depression: n=3; delirium: n=3; severe irritability: n=3; relapse with heroin injection: n=3). Finally, only 5 patients were sustained responders. CONCLUSION: Despite the high seroprevalence of HCV antibodies in this unit, the benefits of antiviral therapy are low due to high drop out rate. Ethanol withdrawal should be the highest priority in these patients.     

Hepatitis C virus serology in parenteral drug users with chronic liver disease

Chronic liver disease is a common complication of parenteral drug use, and liver cirrhosis is frequently seen in users of both parenteral drugs and alcohol. In 1978-83, we studied 88 parenteral drug users with sufficient evidence of chronic liver disease to warrant liver biopsy. Current alcohol abuse was noted in 63 (72%), and six (7%) were former alcohol abusers. Cirrhosis was found in 33 (38%). Hepatitis C antibody (anti-HCV) was detected in 86 (98%). Also, 40 of the anti-HCV positive sera were tested with recombinant immunoblot assay and all of these were reactive. All but one of the 31 patients with anti-HCV and cirrhosis were alcohol abusers. We conclude that parenteral drug users with chronic liver disease almost always have evidence of HCV infection. By 1978-83, HCV infection had become well established in an addict population.     

Hepatitis C in injection drug users:It is time to treat

Injection drug users(IDUs)are at risk of hepatitis C virus(HCV)infection,due to needle and syringe sharing.Chronic HCV infection is a major cause of liver-related morbidity and mortality but can be cured with antiviral treatment leading to sustained viral response(SVR).It is well demonstrated that,when close cooperation between specialists in drug addiction and psychiatrists is assured,patients on maintenance treatment with methadone/buprenorphine can be treated for HCV with response rate,tolerability and side effects similar to those reported in non-IDUs.Current guidelines recommend that active injection drug use should not exclude patients from HCV treatment,but many services remain reluctant to treat IDUs.No significant pharmacodynamic interactions were reported between approved direct anti-viral agents(DAAs)and buprenorphine or methadone.Dose adjustments are not recommended;therefore DAAs appear to be the"perfect"therapy for patients taking opiate substitutive therapy.These suggestions have been recently recognized by the European Association for the Study of the Liver(EASL)and included in EASL Recommendations on Treatment of Hepatitis C 2016.Guidelines confirm that HCV treatment for IDUs should be considered on an individualized basis and delivered within a multidisciplinary team setting;a history of intravenous drug use and recent drug use at treatment initiation are not associated with reduced SVR and decisions to treat must be made on a case-by-case basis.