occult hepatitis c: how convincing are the current data?

REVIEWS

Occult Hepatitis C: How Convincing Are theCurrent Data?

Martin-Walter Welker and Stefan Zeuzem

Sustained virologic response (SVR), defined as unde-tectable hepatitis C virus (HCV) RNA in serum 24weeks after withdrawal of (pegylated)-interferon-

alfa (PEG-IFN)-based antiviral therapy, has become theprimary goal for therapy of patients infected with HCV.Recent reports about “occult” persistence of HCV infec-tion despite constantly negative serum HCV RNA1-14

have led to uncertainty in patients and physicians. Thisreview gives a summary of available data regarding “oc-cult” HCV infection.

Definition of “Occult” HCV Infection“Occult” HCV infection has been defined as detection

of HCV RNA in liver tissue alone or in liver tissue as wellas in peripheral blood mononuclear cells (PBMCs) de-spite constantly undetectable levels of HCV RNA in se-rum.15 Two forms have been distinguished: (1) detectionof HCV RNA in liver tissue of patients with liver diseaseof unknown origin (anti-HCV negative, serum HCVRNA negative) and (2) detection of HCV RNA in livertissue in patients with spontaneous or treatment-inducedHCV RNA clearance from serum (anti-HCV positive,serum HCV RNA negative).8,10

Methods Used in Studies on “Occult” HCVInfection

HCV is a plus-strand RNA virus, which replicates via acomplementary RNA minus-strand.16 The hepatocyte isthe primary target cell, but HCV is potentially also lym-

photropic.17-23 Because HCV has no known ability tointegrate its nucleotide sequence into the host genomeand due to the short half-life of HCV of at most 3hours,24,25 uninterrupted viral replication is required tomaintain infection. Detection of the antigenomic strandis considered an indicator of viral replication.

The studies describing “occult” HCV infection in dif-ferent clinical settings are based on detection of genomicand antigenomic HCV RNA in various compart-ments.3,5,7,8,10,26-28 Testing for HCV RNA in liver speci-mens is considered the gold standard. Because liver biopsyis an invasive procedure, HCV RNA detectability wasinvestigated only in PBMCs within some studies.15

The required sensitive methods are sophisticated andchallenging molecular biological techniques.3,5,7,8,10,26-28

In addition to commercially available test systems, in-house nested reverse transcription–polymerase chainreaction (RT-PCR) protocols and nucleic acid hybridiza-tion (NAH) RT-PCR were used with sensitivities rangingfrom 1-100 IU/mL. Furthermore, PBMCs were mitogen-stimulated in cell culture within some studies in order toincrease the quantity of potential viral particles.27,29,30

“Occult” HCV Infection Type A: Patients with LiverDisease of Unknown Origin

In approximately 10% of patients with abnormal liverfunction tests, the etiology is unknown, but detection ofhepatitis B virus (HBV) DNA as well as HCV RNA inserum or liver has been described.31-33 Only few studiesfocus on “occult” HCV infection as a possible cause ofcryptogenic liver disease (Table 1), and data are conflict-ing.2,10,34-40

In the analysis by Castillo et al., which first described“occult” HCV infection in patients with liver disease ofunknown origin,15 100 patients with persistently abnor-mal aminotransferase and gamma glutamyl transpepti-dase values were investigated.10 All known causes of liverdisease were excluded, such as viral (HBV, HCV) andautoimmune hepatitis as well as alcoholic, drug-induced,metabolic, and genetic liver disorders. Strategies to avoidcross-contamination and to provide optimized testingconditions, including use of several negative controls andenhanced sample processing, were applied according tothe respective method section. An unexpectedly highnumber of 57 of 100 liver samples (57%) tested positive

Abbreviations: HBV, hepatitis B virus; HCC, hepatocellular carcinoma; HCV,hepatitis C virus; NAH, nucleic acid hybridization; PBMC, peripheral bloodmononuclear cell; RBV, ribavirin; RT-PCR, reverse transcription-polymerase chainreaction; TMA, transcription-mediated assay; PEG-IFN, pegylated interferon-alfa;SVR, sustained virologic response; vge, virus genome equivalents.

From the Medizinische Klinik 1, Klinikum der Johann Wolfgang Goethe-Uni-versitat, Frankfurt am Main, Germany.

Received July 10, 2008; accepted October 16, 2008.Address reprint requests to: Prof. Dr. Stefan Zeuzem, Medizinische Klinik 1,

Klinikum der Johann Wolfgang Goethe-Universitat, Theodor-Stern-Kai 7, 60590Frankfurt am Main, Germany. E-mail: [email protected]; fax:�49-69-6301-87676.

Copyright © 2008 by the American Association for the Study of Liver Diseases.Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/hep.22706Potential conflict of interest: Dr. Zeuzem is a clinical investigator, consultant,

and is on the speaker’s bureau for Roche and Schering-Plough.

665

for genomic HCV RNA by RT-PCR. Antigenomic HCVRNA was detectable in 48 of these 57 samples (84%) by insitu hybridization. In addition, PBMCs from 40 of the 57patients (70%) were found positive for HCV RNA.10

Genotyping, a test which typically requires the presenceof at least 20,000 IU/mL,41,42 was successful. Core anti-gen, however, was not detected in liver samples, possiblydue to low expression levels. Infectious virus particleswere also not isolated, and therefore replication was notultimately proven.

Within a subsequent study, 10 of the 57 patientswere treated with PEG-IFN plus ribavirin (RBV) for24 weeks.13 Primary inclusion criteria were detectabil-ity of HCV RNA in liver and PBMCs, absence of anti-HCV and HCV RNA in serum, elevation of alanineaminotransferase level, and proof of necroinflamma-tory activity in liver biopsy. Twenty-four weeks afterthe end of treatment, PBMCs tested negative for HCVRNA in 7 of 10 patients (70%) and a sustained bio-chemical response was achieved in 6 of 10 patients(60%). A complete biochemical and virologic responsein PBMCs was achieved in 3 of 10 patients (30%).However, HCV RNA remained detectable in five offive liver biopsy samples (100%).

The high prevalence of “occult” HCV infection in pa-tients with cryptogenic liver disease described by Castilloet al.10 has not been confirmed by other groups. Tagiuri etal. investigated 26 patients with cryptogenic liver diseaseas well as 57 patients with alcoholic and nonalcoholicfatty liver disease. HCV RNA was undetectable in both

serum and PBMCs within all 26 and 57 patients, respec-tively.37

“Occult” HCV Infection Type B: Patients withResolved HCV Infection

Two clinical situations can be distinguished: (1) spon-taneously resolved hepatitis C and (2) (PEG-)IFN–basedtreatment-induced SVR. More data is available on thelatter, and patients with spontaneously resolved HCV in-fection are sometimes analyzed together with treated pa-tients.

(1) “Occult” HCV Infection Type B in Patientswith Spontaneously Resolved Hepatitis C. Fluctuat-ing serum HCV RNA concentrations in patients withacute hepatitis C infection are well known, leading totemporarily undetectable levels in individual constella-tions. Most data indicate that circulating HCV RNA inserum closely reflects intrahepatic HCV RNA kineticsand that (repeated) testing of serum is effective to dif-ferentiate between persistent and cured HCV infec-tion.25,43-49

Data regarding detection of HCV RNA in compart-ments (PBMCs, liver) other than serum in populations ofpatients with spontaneously resolved hepatitis C (anti-HCV positive, serum HCV RNA negative, no formerantiviral treatment) are conflicting.7,47,50-54 The rates ofdetectability of HCV RNA in PBMCs range from 0%-50%.7,50,54 Within the largest study (n � 69, including sixpatients with SVR after IFN-based antiviral therapy),HCV RNA could neither be detected by cell-associatedtranscription-mediated assay (TMA; sensitivity, 2-50HCV RNA copies in 5 � 106 PBMCs) nor by nestedRT-PCR (sensitivity, 15-150 HCV RNA molecules in5 � 106 PBMCs), respectively.50 Within two smallerstudies, HCV RNA was detected in 6 of 12 and 3 of 30PBMC samples (50% and 10%), respectively.7,54 Therates of detectability of HCV RNA in liver biopsies rangefrom 0%-83%. Four studies reported a high percentage(27 of 44 [61%], 10 of 12 [83%], 10 of 12 [83%], one oftwo [50%]) of intrahepatic detection of HCV RNA.7,51-53

In contrast, within a cohort of 33 women, who had re-ceived HCV contaminated anti-D immunoglobulin,none was found to be intrahepatic HCV RNA positive.47

(2) “Occult” HCV Infection Type B in Patientswith (PEG-)IFN–Induced Sustained Virologic Re-sponse. In patients with chronic hepatitis C and(PEG-)IFN–induced SVR, late relapse is rare (Tables 2and 3).55,56 Similar results have been obtained for patientswith IFN-induced SVR after acute hepatitis C infec-tion.57 Generally, these patients are considered to becured, whereas the clinical significance of residual detec-

Table 1. Studies Investigating HCV RNA Detectability in Liverand PBMC Samples in Patients with Cryptogenic Liver

Disease

Year AuthorHCV RNA Detection

in LiverHCV RNA Detection

in PBMC

1994 Kodali40 not done not done1996 Geller34 0/10 (0%) not done1997 Schmidt39 not done not done2003 Verslype38 1/67 (1%)*† not done2004 Castillo10 57/100 (57%) 40/100 (40%)2005 Castillo2 not done 26/42 (62%)‡§2008 Barril36 not done 49/109 (45%)‡§2008 Halfon35 not done 0/22 (0%)†2008 Tagiuri37 not done 0/96 (0%)†Total 58/177(33%) 115/369(31%)

*All 67 liver specimens were tested by immunohistochemical staining againstHCV-E2. Six cases were positive. Intrahepatic HCV-RNA was tested only in thesesix cases.

†Patients with cryptogenic and nonviral liver disease.‡Patients with end-stage renal disease and abnormal aminotransferase values

of unknown origin.§Overlap of patient cohorts cannot be excluded from information provided in

the publications.

666 WELKER AND ZEUZEM HEPATOLOGY, February 2009

tion of HCV RNA fragments in various compartmentsremains unclear.

Data about persistent detection of HCV RNA inPBMCs in patients with treatment-induced SVR are con-flicting, because some studies found genomic and antige-nomic HCV RNA in PBMCs3,7,9,10,27,58-68 while othersdid not.50,69-76 Detection of HCV RNA in PBMCs inpatients with SVR could reflect prolonged clearance ofviral residues from this compartment, as indicated by lon-gitudinal testing of 10 patients with SVR.77

In liver specimens, most studies show only a small per-centage of persistent detection of HCV RNA after(PEG-)IFN–induced SVR (Table 4). A higher percentageof intrahepatic positive cases was reported by Castillo etal.8 They found antigenomic HCV RNA in 15 of 20 liversamples and genomic HCV RNA in 19 of 20 liver samples(75% and 95%) obtained 35.4 months (mean � standarddeviation, 35.0 months) after withdrawal of (PEG-)IFN–based antiviral therapy as well as in 12 of 20 and 13 of 20PBMC samples (60% and 65%), respectively.8 The HCV

Table 2. Late Virologic Relapse Rates Defined by Detection of HCV RNA in Serum in Patients with Former Chronic HepatitisC and Sustained Virologic Response After (PEG-)Interferon-Alfa–Based Antiviral Therapy

Year Author Therapy Follow-Up Late Virologic Relapse

1994 Romeo72 1 17.5 months (mean)* 0/9 (0%)1995 Reichard119 1 24 months* 0/14 (0%)1996 Chemello120 1 48 months* 8/88 (9%)1996 Vento121 1 84.5 months* 25/29 (86%)1997 De Mitri69 1 36 months* 0/16 (0%)1997 Marcellin28 1 48.0 years (mean)* 3/75 (4%)1997 Teramura71 1 21.1 months (mean)* 0/16 (0%)1998 Camma122 1 34.4 months (mean)* 3/53 (6%)1998 Larghi123 1 39 months (median)* 2/25 (8%)1998 Lau124 1 108 months* 0/5 (0%)1998 Sim125 1 48.2 months (median)* 0/5 (0%)1999 Reichard126 1 64.8 months (mean)* 2/26 (8%)1999 Schvarcz127 2 � 24 months* 11/12 (92%)2000 Collier128 1 38 months (mean)* 2/16 (13%)2001 Bruno129 1 96 months (mean)* 0/36 (0%)2001 Giannini130 1 38 months (mean)* 0/15 (0%)2002 Dalgard131 1, 2 64 months (median)* 1/45 (2%)2003 Adinolfi132 2 12 months* 6/15 (40%)2003 Mozer-Lisewska133 1 24 months* 0/4 (0%)2003 Toccaceli134 1 36.0–76.3 months* 0/87 (0%)2004 Khokhar135 2 36 months* 5/57 (9%)2004 Pham27 1, 2 12 to 60 months* 11/11 (100%)2004 Tsuda136 1 81.6 months (median)* 0/38 (0%)2005 El-Raziky62 2, 4 30 months (mean)* 1/83 (1%)2005 Gallegos63 4 22 months (mean)* 0/25 (0%)2005 Radkowski3 2 64.2 months (mean)* 4/17 (23%)2006 Chavalitdhamrong137 1, 3 35.4 months (mean)* 0/171 (0%)2006 Ciancio138 2 86 months (median)* 11/97 (11%)2006 Desmond139 1, 2, 4 33.1 months (mean)** 1/147 (1%)2006 Formann140 1, 2, 4 29 months (median)* 0/187 (0%)2006 Fytili141 4 � 6 months* 11/50 (22%)2006 Giannini64 1, 2, 4 50.3 months (mean)* 0/80 (0%)2006 Jeffrey142 2 �12 months* 0/22 (0%)2006 Kim143 2 41 months (median)* 0/57 (0%)2006 McHutchison78 1, 2 65.5 months (mean)* 5/302 (2%)2006 Moreno118 1–4 42 months* 0/132 (0%)2007 Basso144 4 28.7 months (median)* 11/110 (10%)2007 Pradat145 1, 2 5–7 years*** 7/87 (8%)2007 Swain146,147 3, 4 49.2 months (mean)* 8/997 (� 1%)2007 Torres-Ibara148 1, 2, 4 36–108 months* 0/75 (0%)2008 Kelly149 2 60 months (mean)* 1/42 (2%)2008 Manns150 3, 4 57 months (mean)* 4/227 (2%)2008 Martino-Peignoux151 2, 4 42 months (mean)* 0/278 (0%)a

2008 Maylin70 1–4 39.2 months (median)* 0/345 (0%)a

Total 143/4228 (3%)

1, IFN monotherapy; 2, IFN/RBV combination therapy; 3, PEG-IFN monotherapy; 4, PEG-IFN/RBV combination therapy.*After end-of-treatment. **After SVR. ***After inclusion in initial study.†Overlap of patient cohorts cannot be excluded from information provided in the abstracts.

HEPATOLOGY, Vol. 49, No. 2, 2009 WELKER AND ZEUZEM 667

core region was amplified, cloned, and sequenced. Al-though the phylogenetic tree showed an apparent cluster-ing between the clones of the core sequences compared toGenBank sequences of genotype 1 to 6, there was nodifference compared to the known pretreatment geno-type. Also, the genetic distances among clones were lowerthan among patients, which argues against contamina-tion.

The question of why late relapse is so rare (Tables 2 and3) remains unanswered when infectious HCV RNA ispresent in liver tissue within the majority of patients withSVR as indicated by the study by Castillo et al.8 More-over, these results were not confirmed within recent andlarger studies, characterized by appropriate sample pro-cessing and use of highly sensitive tests (Table 4).64,70,76,78

“Occult” HCV Infection Versus Low-LevelReplicative Hepatitis C

“Absence” of HCV RNA in serum could be explainedby very low level viremia, not detectable by tests even witha lower detection limit of 50 IU/mL. Four articles reportdetection of HCV RNA in serum or whole blood samplesin the constellation of “occult” HCV infection type A or Bunder circumstances of enhanced sensitivity. Methodsapplied comprise enrichment of suspected virus particlesby ultracentrifugation of serum, use of whole blood sam-ples instead of serum or plasma, or use of more sensitivetests, e.g., nested real-time RT-PCR (lower detectionlimit, �5 IU/mL) or NAH RT-PCR (lower detectionlimit, �10 virus genome equivalents [vge]/mL).1,5,6,27

Within one article, samples from patients already de-

scribed by Castillo et al. were analyzed, which limits thenumber of patients actually investigated.6,10

Within the largest study comprising 106 patients with“occult” HCV infection (serum HCV RNA negative,liver HCV RNA positive) by Bartolome et al., sensitivitywas enhanced by ultracentrifugation of serum samplesbefore performance of real-time RT-PCR.1 Unfortu-nately, no information was provided from which a popu-lation of this large number of patients with “occult” HCVinfection was derived. After ultracentrifugation, 62 of 106serum samples (58%) tested positive for HCV RNA.TMA was performed in a subpopulation of 10 patientswith detectable HCV RNA in serum after ultracentrifu-gation. The viral load of these specimens was reported tobe within a range from 60-160 vge/mL.1 Surprisingly,TMA, a highly sensitive molecular assay (sensitivity, �10IU/mL, �50 vge/mL),79,80 tested negative in all 10 sam-ples.

Furthermore, the data were not confirmed within arecent study investigating 80 patients with (PEG-)IFN �RBV–induced SVR. In this study, a very sensitive PCRhybridization assay (sensitivity, 1-5 IU/mL) was used andall serum (mean follow-up, 50.3 months) and all liver(follow-up at least 42.0 months after SVR) samples testednegative for HCV RNA.64

“Occult” HCV Infection and Immune ResponseAdaptive cellular response mechanisms, especially spe-

cific T cell responses, are believed to play a key role inrecovery from HCV infection as well as in chronic hepa-titis C.81-90 Nevertheless, HCV can escape from specific

Table 3 Late Virologic Relapse Rates Defined by Detection of HCV RNA in Serum in Immunocompromised Patients withFormer Chronic Hepatitis C and Sustained Virologic Response After (PEG-)Interferon-Alfa–Based Antiviral Therapy

Year Author Therapy SVR Achieved Follow-Up

LateVirologicRelapse Clinical Context

2004 Soriano152 1, 2, 4 – 58 months (mean) 0/77 (0%) HIV�2007 Posthouwer153 1, 2, 4 – Up to 15 years 0/100 (0%) Hemophilia patients, HIV�

1, 2, 4 0/19 (0%) Hemophilia patients, HIV�

2003 Bizollon49 2 After transplantation 3 years 1/14 (7%) Liver transplant patients2004 Abdelmalek154 1, 2 After transplantation 24.7 months (mean) 0/29 (0%) Liver transplant patients2005 Bizollon155 2 After transplantation 52 months (mean) 2/34 (6%) Liver transplant patients2006 Mukherjee156 4 Before transplantation 28 months (mean) 0/3 (0%) Liver transplant patients2007 Lilly157 not specified After transplantation Up to 84 months 1/75 (1%) Liver transplant patients2007 Sharma158 4 After transplantation 25 months (median) 0/9 (0%) Liver transplant patients

2001 Casanovas-Taltavull159 1 After transplantation � 41months (mean) 1/9 (11%) Kidney transplant patients2003 Kamar74 1 After transplantation � 22.5 months 0/16 (0%) Kidney transplant patients2003 Luciani160 1 Before transplantation 57 months 0/1 (0%) Kidney transplant patients2005 Mahmoud161 1 After transplantation � 41.5 months (mean) 2/10 (20%) Kidney transplant patients1999 Bjoro162 1 – 24 months 0/3 (0%) Primary hypogammaglobulinemia patientsTotal 7/399 (2%)

1, IFN monotherapy; 2, IFN/RBV combination therapy; 3, PEG-IFN monotherapy; 4, PEG-IFN/RBV combination therapy.


humoral and cellular responses.91,92 Antibodies to HCVproteins can decrease in patients who have cleared HCVRNA from their serum despite persistence of a specificcellular response.85 HCV-specific lymphocytes can be theonly evidence of former HCV infection in otherwise se-ronegative patients.93,94

Quiroga et al. analyzed specific T cell responses inpatients with detection of HCV RNA in liver tissuedespite repeatedly negative tests for HCV RNA andanti-HCV antibodies in serum.14 They identified func-tional virus-specific memory CD4(�) and CD8(�) Tcells and reported that magnitudes of T cell responseswere inversely correlated with the extent of HCV RNAin liver tissue.14 On one hand, this could reflect ongo-ing interaction of the specific cellular immune systemwith persistent, but immunologically well-controlledviral replication. On the contrary, the results could beexplained by coexistence of memory cells with viralresiduals of unknown clinical significance after re-solved HCV infection.

Chronic hepatitis C is well known for its associationwith autoantibodies and autoimmune disorders.95-97

Quiroga et al. found anti-GOR immunglobulin G anti-bodies in 22 of 110 anti-HCV negative, liver HCV RNApositive patients (20%) in comparison with 70 of 110patients with chronic hepatitis C (64%), and none withina control group of 120 patients with liver diseases unre-lated to HCV.98 In patients with chronic hepatitis C, the

clinical significance of non organ-specific autoantibodytiters, e.g., low titer antinuclear antibodies, is controver-sial.96,99 The clinical significance of autoantibodies in pa-tients with “occult” HCV infection remains even moreundefined.

Mixed cryoglobulinemia is considered an extrahepaticmanifestation of HCV infection. A possible association of“occult” HCV infection and cryoglobulinemia was sug-gested by case report series with limited numbers of pa-tients.100,101 In three of three patients who were negativefor anti-HCV and serum HCV RNA with essential cryo-globulinemia, HCV RNA was detected in cryoprecipi-tates.100 In patients with SVR after antiviral therapy dueto chronic hepatitis C who were suffering from mixedcryoglobulinemia, genomic and antigenomic HCV RNAsequences were detected in five of nine PBMC samples(56%).101

On the other hand, a recent study failed to demon-strate “occult” HCV infection in a heterogeneous co-hort of patients with resolved HCV infection andvasculitis (n � 8) as well as in patients without HCVinfection who had connective tissue disease (n � 23).35

Although HCV RNA was detected in PBMC samplesfrom a heterogeneous control group of serum HCVRNA–positive patients, no HCV RNA was detected inPBMCs from patients with resolved or without HCVinfection (zero of eight and 0 of 23, respectively).35

More studies on the possible association of “occult”

Table 4. Long-Term Detectability of Hepatic HCV RNA After (PEG-)Interferon-Alfa–Induced SVR in Patients with FormerChronic Hepatitis C

Year Author Therapy Follow-UpHepatic HCV

RNA Detectability

1994 Romeo72 1 17.5 months (mean)* 1/7 (14%)1995 Reichard119 1 24 months* 1/12 (8%)1995 Shindo163 1 12 months* 3/22 (14%)1997 Di Mitri69 1 6–18 months* 0/16 (0%)1997 Marcellin28 1 12 to 60 months* 0/27 (0%)1997 Teramura71 1 21.1 months (mean)* 0/16 (0%)1998 Larghi123 1 6 to 12 months* 3/25 (12%)1998 Lau124 1 114 months* 0/5 (0%)2002 McHutchison48 1, 2 5.5 months* 7/400 (2%)2003 Bizollon49 2 36 months* 1/14 (7%)†2004 Tsuda136 1 87.6 months (median)** 0/15 (0%)2005 Radkowski3 1, 2 63.6 months (mean)* 3/11 (27%)2006 Castillo8 1–4 35.4 months (mean)* 19/20 (95%)2006 Giannini64 1–4 42.0 months* 0/80 (0%)2006 McHutchison78 1, 2 � 60 months* 0/8 (0%)2006 Moreno118 1–4 42 months (mean)* 4/104 (4%)2008 Martinot-Peignoux151 2, 4 38.4 months (mean)* 0/38 (0%)2008 Maylin70 1–4 22.8 months* 2/114 (2%)Total 44/934 (5%)

1, IFN monotherapy; 2, IFN/RBV combination therapy; 3, PEG-IFN monotherapy; 4, PEG-IFN/RBV combination therapy.*After end-of-treatment. **After pretreatment liver biopsy.†SVR achieved after liver transplantation.§Overlap of patient cohorts cannot be excluded from information provided in the abstracts.


HCV infection with mixed cryoglobulinemia andother autoimmune disorders are needed, especially re-garding the potential therapeutic benefits of (PEG)IFN– based therapy.

“Occult” HCV Infection in ImmunocompromisedPatients

Acquired impairment of the immune system may re-sult from human immunodeficiency virus (HIV) infec-tion, severe underlying illness, e.g., patients with end-stage renal disease, and immunosuppressive therapy, e.g.,after organ transplantation. Reactivation of HCV in pa-tients with compromised immunity has been reportedwithin case reports and small studies.26,102-105 Late re-lapse, however, in immunocompromised patients achiev-ing SVR after (PEG-)IFN–based antiviral therapy is rare(Table 3).

Presence of HCV RNA in serum of HIV-infected pa-tients without detectable anti-HCV antibodies has beendescribed.106,107 HCV replication despite lack of measur-able humoral response is sometimes misnamed “occult”hepatitis C. It should be clearly distinguished from “oc-cult” HCV infection defined by detection of HCV RNAin PBMCs or liver despite undetectable HCV RNA inserum.

In patients suffering from end-stage renal disease inchronic hemodialysis programs, persistence of HCVRNA in PBMCs in 2 of 11 patients (18%) despite tran-siently negative HCV RNA in serum was reported.108 Inthe largest study focusing on “occult” HCV infection inpatients with end-stage renal disease, HCV RNA was de-tected in 49 of 109 PBMC samples (45%).36

Patients undergoing liver transplantation with SVR af-ter (PEG-)IFN–based antiviral therapy have shown long-term histological improvement and clearance of serumand intrahepatic HCV RNA.49 Available data at this timeargue against frequent persistence of infectious HCV par-ticles in PBMCs or liver in patients achieving SVR. Clin-ically most important, late virologic relapse rates arecomparable between patients with and without compro-mised immune systems (Tables 2 and 3).

Clinical Significance of “Occult” HCV InfectionThe crucial question remains whether detection of

HCV RNA fragments, even from the antigenomic strand,should be interpreted as ongoing viral replication or mo-lecular biological residuals of a resolved virus infection.Even more uncertainty arises about the clinical signifi-cance of these findings.

One study compared “occult” HCV infection andovert chronic hepatitis C. Aminotransferase values andhistological scores were lower in the group classified as

having “occult” HCV infection, but cholesterol and tri-glyceride levels were higher. However, this study lacked acontrol group of patients with cryptogenic, intrahepaticHCV RNA–negative liver disease.12

Castillo et al. compared the histological changes in 76patients without serum markers for HBV or HCV infec-tion, but intrahepatic detection of only HBV DNA (n �17), only HCV RNA (n � 35), or detection of both HBVDNA and HCV RNA (n � 24). No histopathologicaldifferences were observed within these groups.11

Incidence of hepatocellular carcinoma (HCC) riseswith progression of the disease to liver cirrhosis and is lowin patients without cirrhosis with chronic hepatitis C.However, even low serum HCV RNA concentrationswere reported to be associated with hepatocarcinogenesisin patients with cirrhosis.109 Detection of HCV RNA hasbeen described in both nontumoral and tumoral liver tis-sue of patients with HCC, despite negative serum HCVRNA.4,110 “Occult” HCV infection has been associatedwith HCC, but a causal relationship between detection ofHCV RNA fragments in tissue samples from patientswith HCC and liver carcinogenesis has not yet beenproven.

ConclusionsDetection of HCV RNA sequences in PBMCs or liver

specimens despite undetectable levels of HCV RNA inserum has been described. However, the significance ofthese findings for the clinical course for the majority ofpatients is uncertain.

Data are conflicting in patients with idiopathic liverdisease. Some groups report detection of HCV RNA se-quences in various compartments while other groupsfailed to detect HCV RNA. Replication of HCV was notshown by virus isolation or confirmed by detection of viralproteins in any study.

Patients achieving SVR after (PEG-)IFN–based anti-viral therapy have a low risk of late virologic relapse.55,56 Itis actually unknown how many of these patients withreported late relapse have “true” relapse and how manywere reinfected. SVR has been linked with constant im-provement of quality of life,111,112 histological improve-ment,48,113 decreased risk of development of livercancer,114,115 and reduced liver-related mortality.116,117

Data about persistent detection of HCV RNA in liversamples or PBMCs are conflicting, but the majority ofdata indicate that patients with SVR also clear HCV RNAfrom liver.48,118

Articles on “occult” HCV infection that report veryhigh rates of detectability of HCV RNA in patients withcryptogenic liver disease or former hepatitis C were pub-lished by yet only five groups.1-8,10-15,68,98,100 Their reports


about detection of HCV RNA in liver despite constantlynegative HCV RNA in serum in a high percentage werenot confirmed by recent studies, but more results must beawaited before a final conclusion can be drawn. Studiesinvestigating potential infectiousness of subjects with “oc-cult” HCV infection have not been conducted. Yet, thereis no reported case proving transmission of HCV from apatient with “occult” HCV infection.

In conclusion, HCV-infected patients with no detect-able HCV RNA in serum 24 weeks after the end of treat-ment should remain to be considered noninfectious andcured of their infection. Further follow-up data areneeded regarding spontaneous relapse and recurrence ofinfection in these patients. Therefore, in patients withSVR, annual surveillance including HCV RNA testingseems clinically reasonable despite a lack of formal cost-effectiveness analyses.

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occult hepatitis c: how convincing are the current data?

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