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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Hepatology. Author manuscript; available in PMC 2013 April 1.
Published in final edited form as:
Published online 2012 February 29. doi:  10.1002/hep.24754
PMCID: PMC3310282
NIHMSID: NIHMS333355

Hepatitis C virus reinfection and superinfection among treated and untreated participants with recent infection

Abstract

Background and aims

To evaluate reinfection and superinfection during treatment for recent HCV.

Methods

ATAHC was a prospective study of the natural history and treatment of recent HCV. Reinfection and superinfection were defined by detection of infection with an HCV strain distinct from the primary strain (using RT-PCR and subtype-specific nested RT-PCR assays) in the setting of spontaneous or treatment-induced viral suppression (one HCV RNA <10 IU/ml) or persistence (HCV RNA >10 IU/mL from enrolment to week 12).

Results

Among 163, 111 were treated, 79% (88 of 111) had treatment-induced viral suppression and 60% (67 of 111) achieved SVR. Following treatment-induced viral suppression, recurrence was observed in 19% (17 of 88), including 12 with relapse and five with reinfection [4.7 cases per 100 person-years (py), 95% CI; 1.9, 11.2]. Among 52 untreated, 58% (30 of 52) had spontaneous viral suppression and recurrence was observed in 10% (3 of 30), including two with reinfection. Following reinfection, ALT levels >1.5× the upper limit of normal were observed in 71% (5 of 7). Among 37 with persistence, superinfection was observed in 16% (3 of 19) of those treated and 17% (3 of 18) of those untreated. In adjusted analysis, reinfection/superinfection occurred more often in participants with poorer social functioning at enrolment and more often in those with ongoing injecting drug use (IDU).

Conclusions

Reinfection and superinfection can occur during treatment of recent HCV and are associated with poor social functioning and ongoing IDU. ALT levels may be a useful clinical marker of re-exposure.

Keywords: acute, treatment, HCV, mixed infection, injecting drug use, HIV

The majority of new cases of hepatitis C virus (HCV) infection in the developed world occur among injecting drug users (IDUs) (1). Pegylated-interferon (PEG-IFN) and ribavirin combination therapy is effective in ~55% of patients (2), but treatment uptake among active IDUs is extremely low (35). Although converging patient, provider, organizational and structural barriers complicate HCV care among IDUs (6), response to therapy in this group are similar to those observed in clinical trials (7). However, there is still a general reluctance to provide treatment largely driven by concerns of adherence, social instability, side effects, co-morbid psychiatric disease and the perceived risk of reinfection following successful treatment (6). While the concern of reinfection is often cited as a reason for not offering treatment to IDUs (6), little is known about reinfection in the setting of treatment.

Reinfection following successful treatment for HCV can occur (812). Few studies have evaluated the incidence of reinfection following successful HCV treatment and the incidence of reinfection has been reported as less than five cases per 100 person years (812). Studies of reinfection following treatment-induced clearance are limited by the small sample sizes (n<40), incomplete longitudinal follow-up, insensitive detection methods and the few cases of reinfection that have been detected.

Ongoing risk behaviors can also lead to HCV re-exposure in the setting of persistent viremia (e.g. no period of aviremia). The detection of multiple unique HCV viral strains at one single time-point is often referred to as HCV mixed infection and could be the result of simultaneous exposure or superinfection. HCV super-infection is used to define the presence of a new infection with a strain different to the initial infection in participants with persistent HCV infection (13, 14). There are no studies of HCV mixed infection or superinfection in the setting of treatment for HCV infection. HCV re-exposure and superinfection during the early stages of HCV treatment could impact virological suppression and treatment outcomes.

The Australian Trial in Acute Hepatitis C (ATAHC) is a prospective trial of the natural history and treatment of recently acquired HCV infection, consisting mainly of IDUs (15). The aim of the current study was to investigate the epidemiological, virological and clinical characteristics of HCV reinfection and superinfection among treated and untreated participants with recent HCV infection.

Methods

Study participants

ATAHC was a prospective cohort study of the natural history and treatment of recent HCV infection (15). Recruitment of HIV infected and uninfected participants was from June 2004 through November 2007. Recent infection with either acute or early chronic HCV infection with the following eligibility criteria:

First positive anti-HCV antibody within 6 months of enrolment; and either

  1. Acute clinical hepatitis C infection, defined as symptomatic seroconversion illness or alanine aminotransferase (ALT) level greater than 10 times the upper limit of normal (ULN, >400 U/L) with exclusion of other causes of acute hepatitis, at most 12 months before the initial positive anti-HCV antibody; or
  2. Asymptomatic hepatitis C infection with seroconversion, defined by a negative anti-HCV antibody in the two years prior to the initial positive anti-HCV antibody.

All participants with detectable HCV RNA during screening were assessed for HCV treatment. Participants unwilling to undergo treatment and those with undetectable HCV RNA at screening continued to be followed. From screening, participants were followed for up to 12 weeks to allow for spontaneous clearance and if HCV RNA remained detectable were offered treatment. Participants were then seen at baseline and 12 weekly intervals for up to 144 weeks (participants receiving treatment were also seen at 4-weekly intervals up to week 12).

All study participants provided written informed consent. The study protocol was approved by local ethics committees. The study was registered with clinicaltrials.gov registry (NCT00192569).

HCV treatment

Participants who began HCV treatment received PEG-IFN α-2a 180 µg weekly for 24 weeks. Due to non-response at week 12 in the initial two participants with HCV/HIV coinfection, the study protocol was amended to provide PEG-IFN and ribavirin combination therapy for 24 weeks in this group. Ribavirin was prescribed at a dose of 1000–1200 mg for those with genotype 1 and 800 mg in those with genotype 2/3.

Detection and quantification of HCV RNA

HCV RNA assessment was performed at all scheduled study visits, initially with a qualitative HCV-RNA assay (TMA assay, Versant, Bayer, Australia, lower limit of detection 10 IU/ml) and if detectable repeated on a quantitative assay (Versant HCV RNA 3.0 Bayer, Australia lower limit of detection 615 IU/ml). HCV genotyping using a commercial assay (Versant LiPa2, Bayer, Australia) was performed on all participants with detectable HCV RNA at screening for clinical decision making. Additional HCV genotyping using sequencing methodologies were also performed on longitudinal samples as described below.

HCV virological suppression, persistence, reinfection and superinfection

Participants with HCV virological suppression (spontaneous or treatment-induced) were defined by one detectable HCV RNA test followed by ≥one undetectable qualitative HCV RNA test(s) (<10 IU/mL). The estimated date of HCV virological suppression was calculated as the midpoint between the dates of the last detectable HCV RNA test and the first undetectable qualitative HCV RNA test. Participants with HCV virological persistence (in the presence or absence of treatment) were defined by one detectable HCV RNA test followed by ≥one detectable HCV RNA test(s), with no undetectable qualitative HCV RNA tests (<10 IU/mL).

Participants with HCV RNA recurrence (detectable HCV RNA following HCV virological suppression) were identified. HCV RNA sequencing was performed (details below) on the first available detectable HCV RNA sample and the first available detectable HCV RNA sample following HCV RNA recurrence. HCV reinfection was defined by the detection of infection with an HCV strain which was distinct from the primary infecting strain among participants with either spontaneous or treatment-induced HCV virological suppression (as described above, ≥one undetectable qualitative HCV RNA test(s) <10 IU/mL).

Participants with HCV virological persistence from the screening/baseline time-point to the first available sample with detectable HCV RNA at ≥12 weeks were identified and HCV RNA sequencing was performed on these samples. Participants with HCV mixed infection were defined by the detection of two distinct HCV strains at the same time-point [<94% E1/HVR1 sequence match between viruses, as described in Pham et al. (16)]. Participants with HCV superinfection were defined by the detection of an HCV strain which was distinct from the primary infecting strain in those with HCV virological persistence [<94% E1/HVR1 sequence match between both time-points as described in Pham et al. (16)]. Among those in whom HCV superinfection was identified, strain-specific nRT-PCR(16) was used to exclude the possibility that the viral strain at the time of superinfection was present at earlier time-points. Participants with HCV virological persistence and no HCV superinfection were defined by the detection of infection with an HCV strain which demonstrated close sequence identity to the primary infecting strain in those with HCV virological persistence with E1/HVR1 sequence data matching >97.6% between both time points, as described in Pham et al. (16).

The estimated date of reinfection and superinfection were calculated as the midpoint between the dates of the last undetectable qualitative HCV RNA test (or detectable test for those with superinfection) and the first detectable HCV RNA test at the time of HCV reinfection (or superinfection).

Detection of HCV reinfection, mixed infection and superinfection

The methods for this work have been previously described (16). Briefly, RNA was extracted from 140 µl of sera using the QIAmp Viral RNA extraction kit (QIAGEN, Hilden, Germany) (16). The E1/HVR1 region encoding the last 171 bp of Core, E1, and the HVR-1 of E2 (840 bp - nucleotides 744 to 1583, with reference to HCV strain H77, GenBank accession number AF009606) was amplified by a real-time nested reverse transcriptase polymerase chain reaction (nRT-PCR), using reagents and reaction conditions described in (16). Mixed infection at a single timepoint was detected by performing four Core real-time subtype-specific nRT-PCRs for HCV 1a, 1b, 2a and 3a (16).

Statistical analyses

Rates of HCV reinfection were calculated using person-time of observation. Confidence intervals (CI) for rates were calculated using Poisson distribution. The time at risk for participants with sustained viral suppression and no viral recurrence was calculated from the estimated date of viral suppression until the date of the last HCV RNA test during follow-up. The time at risk for participants with viral recurrence (viral relapse or reinfection) was calculated from the estimated date of viral suppression until the first positive HCV RNA test of viral recurrence.

Logistic regression was used to estimate crude and adjusted odds ratios (OR) and corresponding 95% CI to identify factors associated with HCV reinfection/superinfection. In unadjusted analyses, potential predictors were determined a priori and included sex, age, social functioning score at enrolment (median), current depression at enrolment, HIV infection at enrolment, IDU (ever, previous 6 months at enrolment and previous 30 days at enrolment) and IDU during follow-up (previous 30 days). Social functioning was calculated using a validated scale from the Opiate Treatment Index (17) and addresses employment, residential stability, and inter-personal conflict as well as social support (higher score reflects poorer social functioning, range score 0–48). Further, in a separate model among those with a history of IDU, we hypothesized that peak IDU frequency, syringe borrowing and methamphetamine injecting were associated with reinfection/superinfection. All variables with P<0.20 in bivariate analysis were considered in multivariate logistic regression models using a backwards stepwise approach. Statistically significant differences were assessed at p<0.05; p-values are two-sided. All final adjusted models included only factors that remained significant at the 0.05 level. All analyses were performed using the statistical package Stata v10.1 (College Station, TX, United States).

Role of funding source

The funding sources for the study did not contribute to study design, data collection, analysis, or interpretation, and had no role in writing of the manuscript or decision to submit the paper for publication.

Results

Participant characteristics

Between June 2004 and February 2008, 163 participants with recent HCV were enrolled in ATAHC (15). The study characteristics and outcomes have been published previously (15). Briefly, the majority were male (72%) and had a history of IDU (76%). Overall, 35% reported IDU within the last month at enrolment (Table 1).

Table 1
Enrolment Characteristics of Participants (n=163)

At enrolment, 17 participants were negative for HCV RNA. The remaining 146 participants were positive for HCV RNA at enrolment and were thus eligible to receive HCV treatment. Of these, 111 initiated HCV treatment. Among those initiating treatment, 74 were infected with HCV alone (received PEG-IFN monotherapy) and 37 were HCV/HIV co-infected (received PEG-IFN alfa-2a monotherapy, n=2; received PEG-IFN alfa-2a +RBV combination therapy, n=35).

HCV reinfection among treated participants with recent infection

Of 111 treated in the ATAHC study, 79% (88 of 111) had treatment-induced virological suppression (Figure 1) and 60% (67 of 111) achieved an SVR. Participants were followed for a mean of 1.2 years following treatment-induced virological suppression (median, 1.1 years; IQR, 0.7, 1.9 years; range, 0.1, 2.9 years) and 0.5 years following SVR (median, 0.5 years; IQR, 0.0, 1.7 years; range, 0, 2.0 years).

Figure 1
Overview of study population at risk of HCV reinfection.

Following treatment-induced virological suppression, HCV RNA recurrence was observed in 19% (17 of 88, Figure 1) and HCV RNA sequencing identified viral relapse in 12 participants with homologous viruses at both timepoints (14%; 12 of 88) and five participants with reinfection (6%; 5 of 88). Among the five with reinfection, three were infected with a single heterologous genotype and ID810 demonstrated mixed reinfection with both HCV 1a and 3a viruses (Figure 3A). The one participant with possible reinfection (ID 2303) had a HCV RNA recurrence following SVR which could not be sequenced due to low-level viremia (1,463 IU/mL) and subsequently spontaneously cleared infection (four HCV RNA negative tests after clearance, with the last test 1.4 years following the first negative test). HCV reinfection occurred 19 weeks (ID1101), 28 weeks (ID637), 31 weeks (ID 2303), 41 weeks (ID810) and 68 weeks (ID2601) following the end of treatment. The demographic characteristics of participants with reinfection are shown in Tables 1 and and22.

Figure 3Figure 3
Natural history of HCV reinfection in A) treated (n=5); and B) untreated (n=2) participants with recent HCV infection and virological suppression. Circles indicate HCV RNA (light grey shading indicates persistent viremia) and squares indicate ALT levels. ...
Table 2
Detailed demographic, behavioural and virological characteristics of participants with HCV reinfection and superinfection.

Incidence of HCV reinfection was 4.7 cases per 100 person-years (py) (95% CI; 1.9, 11.2) following treatment-induced virological suppression and 12.3 per 100 py (95% CI; 5.1, 29.6) following SVR. Ongoing IDU during follow-up was reported in 38% of participants with treatment-induced virological suppression (33 of 88). HCV reinfection in this sub-group was 7.3 per 100 py (95% CI; 2.3, 22.6).

HCV reinfection among untreated participants with recent infection

Of 52 untreated participants in the ATAHC study, 58% (30 of 52) had spontaneous virological suppression and HCV RNA recurrence was observed in 10% (3 of 30). HCV RNA sequencing identified viral relapse in one participant with a homologous viral strain at both time-points and two participants with reinfection (one confirmed by sequencing and one possible). Patient ID 635 spontaneously resolved a HCV 3a infection and following four negative HCV RNA tests was subsequently reinfected with a HCV 2a strain 28 weeks after primary clearance. The one participant with possible reinfection (ID206) could not be sequenced at the time-point of primary infection due to low level HCV RNA (<10 IU/mL).

Incidence of HCV reinfection was 6.1 per 100 py (95% CI; 1.5, 24.6) following spontaneous virological suppression. Incidence of HCV reinfection stratified by HCV treatment status, HIV infection status or IDU during follow-up is shown in Table 4.

Table 4
Incidence of reinfection among participants with treatment-induced (n=118) or spontaneous (n=30) virological suppression during recent HCV infection.

Natural history of HCV reinfection

The individual HCV RNA and ALT profiles of the seven participants with reinfection (five treated and two untreated) are shown in Figure 3. ALT and HCV RNA changes were common following reinfection (Figure 3, Table 3). Five of seven participants (71%) demonstrated peak ALT levels greater than 1.5 times the upper limit of normal around the time of HCV reinfection (319, 1875, 1135, 361 and 894 U/L, Table 3) compared to one of seven at enrolment (14%, 120 U/L, Table 3). Reinfection remained persistent in three of seven cases (43%). Among those with HCV reinfection, two participants demonstrated evidence of HCV mixed infection during follow-up (ID810 and ID2601, Figure 3).

Table 3
ALT levels, HCV RNA and virological outcomes among participants with HCV reinfection (n=7) and superinfection (n=6) during recent HCV infection.

HCV superinfection among treated and untreated participants with recent infection

Among treated participants with HCV RNA persistence (lack of virological suppression through week 12) RNA sequencing detected 16% (3 of 19) with superinfection (Figure 2). Among untreated participants with HCV RNA persistence, 17% (3 of 18) were superinfected. The demographic and detailed demographic characteristics of participants with superinfection are shown in Tables 1 and and22.

Figure 2
Overview of study population at risk of HCV superinfection.

Natural history of HCV superinfection

The individual HCV RNA, ALT profiles and virological outcomes of these six participants with superinfection are shown in Figure 4 and Table 3. ALT and HCV RNA changes were common following superinfection. Five of six participants (83%) demonstrated peak ALT levels greater than 1.5 times the upper limit of normal around the time of superinfection (983, 181, 428, 224 and 355 U/L) as compared to three of six at enrolment (50%; 215, 114 and 130 U/L; Table 2). Further, five of six participants (83%) demonstrated greater peak HCV RNA levels at the time of superinfection as compared to enrolment (ID110, 5.7 vs. 4.7; ID2010, 6.9 vs. 5.4; ID602, 4.9 vs. 3.0; ID1403, 5.8 vs. 5.0 and ID2002, 4.7 vs. 3.3 log10 IU/ml, Table 3). Among those with HCV superinfection, two participants demonstrated evidence of HCV mixed infection during follow-up (ID 110 and ID2010, Figure 4).

Figure 4Figure 4
Natural history of HCV superinfection in A) treated (n=3); and B) untreated (n=3) with recent HCV infection and persistence. Circles indicate HCV RNA (light grey shading indicates persistent viremia) and squares indicate ALT levels. Subtypes are colour-coded ...

Risk factors for HCV reinfection/superinfection

The demographic characteristics of the seven participants with reinfection and six participants with superinfection are shown in Tables 1 and and2.2. In four of seven participants with reinfection (ID637, ID1101, ID2303 and ID206), IDU was the attributed mode of acquisition for both initial infection and reinfection. In the three other participants (ID635, ID810 and ID2601, all HIV-infected males), both initial infection and reinfection were attributed to high-risk homosexual contact, although two of these cases (ID635 and ID 2601) also reported IDU (frequency less than weekly and denied any injecting equipment sharing) at the time of both exposures. In all six participants with superinfection, IDU was the attributed mode of acquisition for both initial infection and reinfection.

Factors associated with reinfection/superinfection were evaluated by comparing participants with reinfection/superinfection (n=13) to those demonstrating virological suppression without reinfection and those with viral persistence without superinfection (n=137, Supplementary Table 1). In unadjusted analyses in the overall population, reinfection/superinfection occurred more often in those with poor social functioning, those with IDU in previous 6 months at enrolment and those with IDU during follow-up. In adjusted analysis, reinfection/superinfection occurred more often in participants with poorer social functioning at enrolment [score ≤14 vs. score >14 adjusted OR (AOR) 6.05, 95% confidence interval (95% CI), 1.19, 30.87, P=0.030] and those with IDU during follow-up (AOR 4.35, 95% CI, 1.09, 17.45, P=0.038).

We performed further analyses to assess specific injecting behaviors during follow-up associated with reinfection/superinfection among those with a history of IDU (n=112, Supplementary Table 2). In unadjusted analyses in those with a history of IDU, reinfection/superinfection occurred more often in those with poor social functioning, ≥daily peak IDU frequency during follow-up, syringe borrowing during follow-up and methamphetamine/cocaine injecting during follow-up. In adjusted analysis, reinfection/superinfection occurred more often in participants with poorer social functioning at enrolment [score ≤14 vs. score >14 AOR 5.85, 95% CI, 1.11, 30.92, P=0.038] and in those with methamphetamine injecting during follow-up (AOR 7.29, 95% CI, 1.86, 28.54, P=0.004).

DISCUSSION

In this prospective study, we have characterized the virological, clinical and epidemiological features of reinfection/superinfection in treated and untreated participants with recent HCV, consisting predominantly of IDUs. Among those with reinfection and superinfection, elevations in HCV RNA and ALT levels around the time of secondary infection were common, providing potentially useful clinical markers for re-exposure. Reinfection/superinfection was associated with poor social functioning at enrolment and ongoing IDU (but not injecting at enrolment). Among injectors, the greatest odds of reinfection/superinfection occurred among those with poor social functioning at enrolment and ongoing methamphetamine IDU. The outcomes of infection following reinfection and superinfection were heterogeneous, with four of seven participants with reinfection demonstrating spontaneous clearance of reinfection (including two following treatment). This study provides a greater understanding of the natural history and factors associated with reinfection/superinfection, particularly in the setting of HCV treatment among IDUs.

Elevations in ALT occurred in almost three-quarters of participants following reinfection/superinfection. The observed increases in ALT following reinfection are consistent with data from chimpanzees (1822) and a small series of case studies in humans (11, 23). Similarly, the observed increases in ALT following superinfection is consistent with available data from a small number of superinfection case studies in chimpanzees (24) and humans (25, 26). It is possible that given the frequency of testing, elevations in ALT in some participants may have been missed. However, it is interesting that those with reinfection and superinfection were similar with respect to the observed increases in ALT following re-exposure. Increases in HCV RNA levels occurred in greater than three-quarters of participants around the time of HCV superinfection. These data have important clinical implications as regular monitoring of ALT and HCV RNA elevations among participants at high-risk may provide a clinically useful tool for detecting re-infection and superinfection.

Reinfection and superinfection were independently associated with poor social functioning at enrolment and ongoing IDU (but not IDU at the time of study enrolment). Among those with a history of IDU, the greatest risk of reinfection/superinfection infection was among those with poor social functioning at enrolment and ongoing methamphetamine IDU. Given the small number of cases of reinfection and superinfection reported in studies performed to date (16, 2734), there are no previous studies which have identified factors independently associated with reinfection and/or superinfection. Although IDU during follow-up was associated with reinfection/superinfection, a history of IDU and recent IDU (past 30 days and past 6 months) at study enrolment were not. Thus, within IDU populations it may be difficult to predict on the basis of injecting characteristics at enrolment who will subsequently become reinfected/superinfected with HCV. As such, it is important to ensure that adequate harm reduction measures are in place for those who relapse back to ongoing IDU.

Among treated participants, the rate of reinfection was 4.7 cases per 100 person-years in those with virologic suppression and 12.3 cases per 100 person-years in those with SVR. Our results are slightly higher than previously reported retrospective studies of reinfection following successful treatment of chronic HCV infection among IDUs (812). In Germany, among 18 IDUs followed for a mean of 2.8 years after successful treatment for HCV infection (50% relapsed to IDU following treatment), 0–2 cases of reinfection were observed (reinfection <4.1 cases per 100 person-years) (8). Similar results were reported from 27 IDUs followed for 5.4 years following SVR in Norway (9). The incidence of reinfection was 0.8 cases per 100 person-years, 2.5 cases per 100 person-years among the 9 of 27 (33%) that returned to IDU during follow-up (9). In Canada, two reinfections were observed among 35 IDUs with SVR and the rates of reinfection were 3.2 per 100 p-y (95% CI:0.4, 11.5) overall and 5.3 per 100 p-y (95% CI:0.6, 19.0) among those reporting injecting following SVR (11). The observed rate does not support withholding therapy for IDU populations, where the greatest burden of HCV-related disease is concentrated. However, given that reinfection can occur, education around harm reduction and the risks of reinfection following successful treatment should be incorporated into the plan of care for those with a history of IDU.

There are a number of limitations to this study. Among participants with superinfection, it is possible that the viral strain at the time of superinfection was present at enrolment. Although the subtype-specific nRT-PCR assays were sensitive (86 IU/mL), we cannot exclude the possibility of the presence of a virus previously present in low copy number. Further, in those with HCV persistence, we cannot exclude the possibility of rapid clearance with subsequent reinfection between testing intervals. This may have been more possible in untreated participants, given that participants were tested for HCV RNA more frequently (monthly) during treatment. We also cannot exclude the possibility that some reinfections with rapid clearance occurred during periods when sampling of HCV RNA was only every 12 weeks, potentially also underestimating the rate of reinfection. That being said, this would not have had a major impact on the detection of HCV reinfections that remain persistent, which is clinically more important. It is possible that some of those with HCV persistence following reinfection were not followed for a sufficient time to allow for spontaneous clearance. If those with HCV reinfection and persistence subsequently cleared infection given longer follow up, this would have underestimated the proportion with clearance of HCV reinfection. However, the two with clearance of reinfection had two negative HCV RNA tests ≥60 days following clearance (well-accepted definition of spontaneous clearance), so we are confident of clearance in these participants.

The study findings have important implications for the clinical management of HCV in IDUs and for HCV vaccine development. Regular HCV RNA and/or ALT testing could be used as useful clinical tools for the detection of some cases of HCV reinfection/superinfection. Although this study was performed among those with recent HCV, it is possible that sharp ALT rises sometimes observed in chronic HCV may be attributed to superinfection. Although many clinicians may not have access to the sequencing technologies employed here, a standard HCV genotype following suspected reinfection or superinfection (based on ALT or HCV RNA elevations) may identify some individuals with re-exposure. Those at greatest risk of HCV reinfection/superinfection include IDUs, particularly those with poor social functioning and ongoing injecting (particularly methamphetamine). Social functioning at baseline may provide some indication of those most likely to become reinfected/superinfected. Harm reduction and education around the risks of HCV reinfection and superinfection should be incorporated into the clinical management of all IDUs initiating treatment for HCV. However, IDUs should not be denied care on the basis of concerns of HCV reinfection. These results also have implications for HCV vaccine design. The observation that both participants with spontaneous HCV clearance and two of five with treatment-induced clearance demonstrated spontaneous clearance following HCV reinfection is important. It suggests that the induction of partial protective immunity may be possible, providing hope for a vaccine which enhances spontaneous HCV clearance.

Supplementary Material

Supp Table S1-S2

Acknowledgments

Grant Support: This study was funded by the National Institutes of Health grant RO1 DA 15999-01. The Kirby Institute for infection and immunity in society is funded by the Australian Government Department of Health and Ageing and is affiliated with the Faculty of Medicine, University of New South Wales. Roche Pharmaceuticals supplied financial support for pegylated IFN–alfa-2a/ribavirin. STP was supported by a University International Postgraduate Award. GD and AL were supported by National Health and Medical Research Council Practitioner Research Fellowships. MH was supported by a National Health and Medical Research Council Career Development Award and a VicHealth Senior Research Fellowship. JK and RB were supported by National Health and Medical Research Council Research Fellowships.

Abbreviations

ALT
Alanine transaminase
ATAHC
Australian Trial in Acute Hepatitis C
CI
confidence interval
E1/HVR1
envelope glycoprotein-1 and hypervariable region 1 on E2
HCV
hepatitis C virus
HIV
human immunodeficiency virus
IDU
injecting drug user
MSM
men who have sex with men
nRT-PCR
nested reverse transcription - polymerase chain reaction
PEG-IFN
pegylated-interferon
P-Y
person-year
RBV
ribavirin
RNA
Ribonucleic acid
SVR
Sustained virological response
ULN
upper limit of the normal range

Footnotes

Disclosures: GD, GM and JK have received research support from Roche Pharmaceuticals. GD is on the speaker’s bureau for Roche Pharmaceuticals. GD and GM are members of advisory board for Roche Pharmaceuticals. GD and BY have received travel grants from Roche Pharmaceuticals. GD is a consultant/advisor for Merck, Tibotec, and Abbott. JG is a member of an advisory board for Merck. GM is a consultant/advisor for Bristol-Myers Squibb, Gilead, Merck and Roche.

Author Contributions: Authors GJD, GVM, MH and JMK designed the original ATAHC study and wrote the protocol. Authors JG, STP, GVM, KP, JMK, GJD and PAW designed the HCV reinfection and superinfection study. Authors STP and RAB performed all laboratory work. Author JG drafted the primary statistical analysis plan, which was reviewed by KP, STP, GJD, GVM and PAW. The primary statistical analysis was conducted by JG and KP. All authors reviewed data analysis. Authors JG, STP, GD and PAW wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.

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