Ultracentrifugation of serum samples allows detection of hepatitis C virus RNA in patients with occult hepatitis C

No evidence of occult hepatitis C virus (HCV) infection in serum of HCV antibody-positive HCV RNA-negative kidney-transplant patients

Persistence of hepatitis C virus (HCV) in patients who cleared HCV is still debated. Occult HCV infection is described as the presence of detectable HCV RNA in liver or peripheral blood mononuclear cells (PBMCs) of patients with undetectable plasma HCV-RNA by conventional PCR assays. We have assessed the persistence of HCV in 26 kidney-transplant patients, followed up for 10.5 years (range 2-16), after HCV elimination while on hemodialysis. If HCV really did persist, arising out of the loss of immune control caused by institution of the regimen of immunosuppressive drugs after kidney transplantation, HCV reactivation would have taken place. Their immunosuppression relied on calcineurin inhibitors (100%), and/or steroids (62%), and/or antimetabolites (94%). An induction therapy, given to 22 patients, relied on rabbit antithymocyte globulin (59%) or anti-IL2-receptor blockers (32%). All patients had undetectable HCV RNA as ascertained by several conventional tests. At the last follow-up, no residual HCV RNA was detected in the five liver biopsies, the 26 plasma, and in the 37 nonstimulated and 24 stimulated PBMCs tested with an ultrasensitive RT-PCR assay (detection limit, 2 IU/ml). No biochemical or virologic relapse was seen during follow-up. The absence of HCV relapse in formerly HCV-infected immunocompromised patients suggests the complete eradication of HCV after its elimination while on dialysis.

Occult HCV infection: an unexpected finding in a population unselected for hepatic disease

Background

Occult Hepatitis C virus (HCV) infection is a new pathological entity characterized by presence of liver disease and absence or very low levels of detectable HCV-RNA in serum. Abnormal values of liver enzymes and presence of replicative HCV-RNA in peripheral blood mononuclear cells are also observed. Aim of the study was to evaluate occult HCV occurrence in a population unselected for hepatic disease.

Methodology/Principal Findings

We chose from previous epidemiological studies three series of subjects (n = 276, age range 40–65 years) unselected for hepatic disease. These subjects were tested for the presence of HCV antibodies and HCV-RNA in plasma and in the peripheral blood mononuclear cells (PBMCs) by using commercial systems. All subjects tested negative for HCV antibodies and plasma HCV-RNA and showed normal levels of liver enzymes; 9/276 patients (3.3%) were positive for HCV-RNA in PBMCs, identifying a subset of subjects with potential occult HCV infection. We could determine the HCV type for 8 of the 9 patients finding type 1a (3 patients), type 1b (2 patients), and type 2a (3 patients).

Conclusions

The results of this study show evidence that occult HCV infection may occur in a population unselected for hepatic disease. A potential risk of HCV infection spread by subjects harbouring occult HCV infection should be considered. Design of prospective studies focusing on the frequency of infection in the general population and on the clinical evolution of occult HCV infection will be needed to verify this unexpected finding.

Accurate strand-specific quantification of viral RNA

The presence of full-length complements of viral genomic RNA is a hallmark of RNA virus replication within an infected cell. As such, methods for detecting and measuring specific strands of viral RNA in infected cells and tissues are important in the study of RNA viruses. Strand-specific quantitative real-time PCR (ssqPCR) assays are increasingly being used for this purpose, but the accuracy of these assays depends on the assumption that the amount of cDNA measured during the quantitative PCR (qPCR) step accurately reflects amounts of a specific viral RNA strand present in the RT reaction. To specifically test this assumption, we developed multiple ssqPCR assays for the positive-strand RNA virus o'nyong-nyong (ONNV) that were based upon the most prevalent ssqPCR assay design types in the literature. We then compared various parameters of the ONNV-specific assays. We found that an assay employing standard unmodified virus-specific primers failed to discern the difference between cDNAs generated from virus specific primers and those generated through false priming. Further, we were unable to accurately measure levels of ONNV (−) strand RNA with this assay when higher levels of cDNA generated from the (+) strand were present. Taken together, these results suggest that assays of this type do not accurately quantify levels of the anti-genomic strand present during RNA virus infectious cycles. However, an assay permitting the use of a tag-specific primer was able to distinguish cDNAs transcribed from ONNV (−) strand RNA from other cDNAs present, thus allowing accurate quantification of the anti-genomic strand. We also report the sensitivities of two different detection strategies and chemistries, SYBR® Green and DNA hydrolysis probes, used with our tagged ONNV-specific ssqPCR assays. Finally, we describe development, design and validation of ssqPCR assays for chikungunya virus (CHIKV), the recent cause of large outbreaks of disease in the Indian Ocean region.

Presence of HCV-RNA after ultracentrifugation of serum samples during the follow-up of chronic hepatitis C patients with a sustained virological response may predict reactivation of hepatitis C virus infection

BACKGROUND

Concentration of viral particles by ultracentrifugation of serum prior to PCR allows detection of hepatitis C virus (HCV) RNA in patients with undetectable viral RNA by conventional PCR assays.

AIM

To analyse if HCV-RNA is detected after serum ultracentrifugation in chronic hepatitis C patients with a sustained virological response to antiviral therapy (defined as serum HCV-RNA negativity by conventional assays 6 months after the end of therapy).

METHODS

HCV-RNA was tested using real-time PCR in ultracentrifuged sera collected during the post-treatment follow-up (mean: 42 +/- 27 months) in 57 sustained virological responders (SVR).

RESULTS

After serum ultracentrifugation, HCV-RNA was detected on at least one occasion during the follow-up in 29/57 (51%) SVR. Thirteen (23%) of these 57 SVR suffered a reactivation 18 +/- 8 months after the end of therapy (reappearance of serum HCV-RNA detectable by conventional assays). Among reactivated patients, 11/13 (85%) had HCV-RNA in ultracentrifuged serum samples (detectable 10 +/- 5 months before reactivation), while HCV-RNA was positive after ultracentrifugation in 18/44 (41%) long-term SVR (P = 0.01). Persistence of detectable HCV-RNA after serum ultracentrifugation was associated with reactivation (P = 0.001).

CONCLUSIONS

Serum ultracentrifugation prior to PCR allows detection of HCV-RNA in SVR and its persistence may predict late reactivation.

Hepatitis C virus RNA quantitation in venous and capillary small-volume whole-blood samples

Quantitation of hepatitis C virus (HCV) RNA in plasma and serum samples is a costly procedure in both time and reagents. Additionally, cell-associated viral RNA may not be detected. This study evaluated the accuracy of HCV RNA quantitation in small-volume whole-blood (WB) samples, which would be appropriate for point-of-care diagnostic devices. HCV RNA was extracted from 222 clinical plasma and WB samples of 82 patients with chronic hepatitis C by a specific locked nucleic acid-mediated capture method and quantified by real-time reverse transcription-PCR. The results were compared to the reference plasma viral load determined with the COBAS AmpliPrep/TaqMan (CAP/CTM) HCV test. This assay had an analytical sensitivity of 9 IU per 10-microl sample (95% limit of detection [95% LOD]), a linearity range of 500 to 5 x 10(6) IU/ml, and was accurate in testing 10 HCV subtypes (<0.22 log10 unit) in plasma. The assay was matrix equivalent for plasma and WB samples (coefficient of determination [R2] of 0.943) and had a specificity of 100% (n = 20) in WB samples. The HCV RNA concentration in clinical WB samples exceeded the estimated hematocrit-corrected plasma viral loads by 0.22 log10 unit, but absolute quantitation results in plasma and WB samples were identical (95% confidence interval, -0.06 to 0.04 log10 unit). The sensitivity in WB samples was 100% (n = 141) for plasma concentrations above the 95% LOD. Quantitation results in 10-microl WB samples correlated linearly with the CAP/CTM HCV plasma test results (R2 = 0.919; n = 140) and did not differ between capillary and venous samples (R2 = 0.960; n = 40). This study shows that HCV RNA quantitation in 10-microl WB samples is appropriate for monitoring viral loads of >900 IU/ml, although the use of WB does not increase the diagnostic sensitivity.

Hepatitis C virus infection in the family setting of patients with occult hepatitis C

Family members of patients with chronic hepatitis C virus (HCV) infection are at increased risk of HCV infection but the prevalence of HCV among family members of patients with occult HCV infection is not known. Anti-HCV, serum HCV RNA and levels of liver enzymes were determined in 102 family members of 50 index patients with occult HCV infection and in 118 family members of 59 chronic hepatitis C index patients. HCV RNA and/or anti-HCV were detected in 10/102 (9.8%) relatives of patients with occult HCV infection and in 4/118 (3.4%) of patients with chronic hepatitis C. Fourteen additional family members (seven were relatives of index patients with occult HCV infection) had abnormal values of liver enzymes without serological markers of HCV infection. Two of these patients (who were relatives of two index patients with occult HCV infection) underwent a liver biopsy and were diagnosed with an occult HCV infection because HCV RNA was detected in the liver cells in the absence of serological HCV markers. In conclusion, the prevalence of HCV infection among family members of patients with occult HCV infection was similar to that found among family members of patients with chronic hepatitis C. This stresses the need to adopt strategies to prevent the transmission of HCV in the family setting of patients with occult HCV infection.

Identification of serologically silent occult hepatitis C virus infection by detecting immunoglobulin G antibody to a dominant HCV core peptide epitope

BACKGROUND/AIMS

Occult HCV infection has been described among anti-HCV-HCV RNA-negative individuals with abnormal transaminase values in whom HCV RNA is detected in liver.

METHODS

IgG antibody to an HCVcore-derived peptide (anti-HCVcore) was investigated in 145 patients with serologically silent occult HCV infection.

RESULTS

At the time of the diagnostic biopsy 45/145 (31%) occult HCV-infected patients tested IgG anti-HCVcore-positive but none of the 140 patients with HCV-unrelated liver disease (P<0.001). Among 23 IgG anti-HCVcore-positive patients at baseline, 22 remained antibody-reactive (one became antibody-negative). Similarly, 17/31 baseline anti-HCVcore-negative patients remained non-reactive whereas 14 seroconverted to IgG anti-HCVcore (although transiently in 10 patients). Thus, a total of 59/145 (40.7%) patients with occult HCV infection showed IgG anti-HCVcore reactivity at any time point analyzed, including 14 initially non-reactive patients. By supplemental immunoblot assay 16 sera reacted weakly with an HCVcore-peptide band (indeterminate result) of which 10 (62.5%) reacted in the IgG anti-HCVcore assay. Occult HCV-infected patients who tested anti-HCVcore-positive showed more frequently signs of necro-inflammation (P=0.035) and greater percentages of HCV RNA-positive hepatocytes (P=0.004) compared with those anti-HCVcore-negative.

CONCLUSIONS

This work documents that IgG anti-HCVcore testing identifies occult HCV infection among seronegative, non-viremic patients using screening tests and may be useful in tracking anti-HCV-negative infections.

Histological changes in HCV antibody-positive, HCV RNA-negative subjects suggest persistent virus infection

It is unclear whether hepatitis C virus (HCV) has been eradicated or persists at a low level in HCV antibody-positive HCV RNA-negative individuals. The natural history and liver histology are not well characterized. One hundred seventy-two HCV antibody-positive, serum HCV RNA-negative patients underwent diagnostic liver biopsy between 1992 and 2000 and were followed a median 7 years (range, 5-12). Patients with any possible cause of liver injury other than HCV were excluded. A single histopathologist scored sections using Ishak criteria. Characterization of the inflammatory infiltrate in selected cases used a novel semiquantitative technique and compared with HCV RNA-positive patients and healthy controls. One hundred two patients were excluded because of a risk factor for liver injury other than HCV. Seventy patients met the study criteria; four (5.7%) became HCV RNA-positive during follow-up. Sixty-six cases remained HCV RNA-negative; five (7.5%) had a normal liver biopsy; 54 (82%) had fibrosis (stage 2 or 3 in 16 (24%)). Nonviremic cases revealed expanded portal tracts (P < 0.05), with fewer CD4+ (P < 0.05) and more CD8+ cells (P < 0.05) than healthy controls, but were indistinguishable from HCV RNA-positive cases for these parameters. Lobular CD4 staining, absent in healthy controls, was noted in both HCV RNA-negative and -positive cases and was more marked in the latter (P < 0.05) with a sinusoidal lining cell distribution.

CONCLUSION

Nonviremic HCV antibody-positive patients have a liver biopsy that is usually abnormal. Fibrosis was present in most with similar inflammatory infiltrate to viremic cases. The presence of a CD8+ rich inflammatory infiltrate suggests an ongoing immune response in the liver, supporting the view that HCV may persist in the liver in the majority of HCV RNA-negative cases.

A new method of concentrating hepatitis B virus (HBV) DNA and HBV surface antigen: an application of the method to the detection of occult HBV infection

BACKGROUND

The risk of post-transfusion hepatitis B virus (HBV) infection has been reduced after the implementation of HBV nucleic acid amplification technology (NAT). However, the problem of HBV DNA-positive and HBV surface antigen (HBsAg)-negative occult HBV infections remains to be solved. This is in part due to the HBV DNA load being too low to detect these occult HBV infections using mini-pool NAT. In Japan, the assay for the antibody against the HBV core antigen (anti-HBc) has not completely excluded occult HBV infection. To solve this problem, we have developed a new method of concentrating HBV DNA and HBsAg simultaneously to increase the sensitivity of detection tests.

METHODS

Virus concentration is achieved by the enhancement of the agglutination of viruses using poly-L-lysine in the presence of a bivalent metal. Poly-L-lysine-coated magnetic beads are used to shorten the time of each step of the concentration procedure. Seventy-seven anti-HBc-positive and HBsAg-negative donations were examined. HBsAg and anti-HBc were tested by enzyme immunoassay (EIA) (AxSYM; Abbott) and haemagglutination inhibition test (Japanese Red Cross), respectively.

RESULTS

HBV surface antigen and HBV DNA levels were concentrated up to four- to sevenfold. Using this method, 35 of the 77 anti-HBc-positive and HBsAg-negative donors were HBV DNA-positive by individual NAT and a further five donors became HBV DNA-positive by HBV concentration. Twenty-seven of 40 occult HBV infections became HBsAg-positive by HBsAg concentration.

CONCLUSION

Our new method of concentrating HBV and HBsAg increased the sensitivities of EIA and HBV NAT, and enabled us to detect 27 of 40 occult HBV infections by HBsAg EIA.

Detection of hepatitis C virus in thyroid tissue from patients with chronic HCV infection

Thyroid dysfunctions are common in chronic hepatitis C virus (HCV) infection. HCV-RNA has been detected by reverse-transcription polymerase chain reaction (PCR) in thyroid from HCV infected patients with acquired immunodeficiency syndrome. However, morphological evidence of HCV replication in thyroid cells from immune competent patients has not been provided. In situ hybridization and real-time-PCR were used to analyze HCV-RNA replication in thyroid tissue from 11 patients (3 anti-HCV, serum HCV-RNA positive; 8 anti-HCV negative). Genomic and antigenomic HCV-RNA was detected in the thyroid of the 3 anti-HCV positive patients at concentrations of 2.6 x 10(4), 1.7 x 10(4), and 8.6 x 10(3) copies/microg of total RNA (genomic) and 3.2 x 10(2), 4.3 x 10(3) and 2.9 x 10(2) HCV-RNA copies/microg of total RNA (antigenomic). No HCV-RNA was detected in the thyroid tissue of the 8 anti-HCV negative patients. Presence of genomic/antigenomic HCV-RNA in the 3 anti-HCV positive cases was confirmed by in situ hybridization. Signals were observed in the cytoplasm of the thyroid cells. In conclusion, the data obtained indicate that HCV may infect cells of the thyroid in immune competent patients with chronic HCV infection. The pathogenic implications of this finding merit further research.

Occult hepatitis B virus and hepatitis C virus infections

Occult HBV infection is a well-recognised clinical entity characterised by the detection of HBV-DNA in serum and/or in liver in the absence of detectable hepatitis B surface antigen (HBsAg). Occult HBV infection has been described not only in patients who have resolved an acute or chronic HBV infection but also in patients without any serological markers of a past HBV infection. Occult HBV infection in patients with chronic HCV infection may induce more severe liver disease and lower response rate to interferon treatment. The existence of occult HCV infections has been also reported more recently. Occult HCV infection is characterised by the presence of HCV-RNA in liver and peripheral blood mononuclear cells in the absence of detectable serum HCV-RNA. Occult HCV infection may occur under two different clinical situations: in hepatitis C antibody-(anti-HCV) negative and serum HCV-RNA-negative patients with abnormal liver function tests and in anti-HCV-positive patients who have no detectable serum HCV-RNA and who have normal liver enzymes. The clinical relevance of occult HCV infections is still under investigation.

Occult hepatitis C virus infection among hemodialysis patients

Occult hepatitis C virus (HCV) infection (i.e., detectable HCV-RNA in the liver or peripheral blood mononuclear cells) in the absence of both serum HCV-RNA and anti-HCV antibodies has not been investigated in hemodialysis patients. In this study, real-time PCR and in situ hybridization was used to test for the presence of genomic and antigenomic HCV-RNA in peripheral blood mononuclear cells of 109 hemodialysis patients with abnormal levels of liver enzymes. Occult HCV infection, determined by the presence of genomic HCV-RNA, was found in 45% of the patients; 53% of these patients had ongoing HCV replication, indicated by the presence of antigenomic HCV-RNA. Patients with occult HCV infection had spent a significantly longer time on hemodialysis and had significantly higher mean alanine aminotransferase levels during the 6 mo before study entry. Logistic regression analysis revealed that mortality was associated with age >60 yr (odds ratio 3.30; 95% confidence interval 1.05 to 10.33) and the presence of occult HCV infection (odds ratio 3.84; 95% confidence interval 1.29 to 11.43). In conclusion, the prevalence of occult HCV infection is high among hemodialysis patients with persistently abnormal values of liver enzymes of unknown cause. The clinical significance of occult HCV infection in these patients requires further study.

Desperately seeking hepatitis C virus

Spanish investigators described recently the so-called occult hepatitis C virus (HCV) infection, emphasizing the detection of genomic and antigenomic HCV RNA strands in liver and peripheral blood mononuclear cells. Therefore, the persistence of viral replication in occult HCV infection should be considered as a putative source of infection among family members and patients undergoing invasive procedures, transfusion or transplantation. Additionally, the most worrisome finding is that an occult HCV infection may persist in patients with sustained virological response.

Occult persistence and lymphotropism of hepatitis C virus infection

Recent discovery of occult hepatitis C virus (HCV) infection persisting after spontaneous or antiviral therapy-induced resolution of hepatitis C was made possible by the introduction of nucleic acid amplification assays capable of detecting HCV RNA at sensitivities superseding those offered by clinical tests. Although individuals with this seemingly silent HCV infection are usually anti-HCV antibody reactive and have normal liver function tests, occult HCV infection has also been reported in anti-HCV-negative individuals with persistently elevated liver enzymes of unknown etiology. Studies have shown that HCV RNA can persist for years in serum, lymphomononuclear cells and liver in the absence of clinical symptoms, although histological evidence of a mild inflammatory liver injury can be occasionally encountered. Furthermore, while HCV RNA can be detected in circulating lymphoid cells in approximately 30% of cases, a short-term culture under stimulatory conditions augments HCV replication in these cells allowing detection of virus in otherwise HCV-negative cases. HCV infects different immune cell subsets, including CD4⁺ and CD8⁺ T lymphocytes, B cells and monocytes. Studies employing clonal sequencing and single-stranded conformational polymorphism analyses have revealed unique HCV variants residing in immune cells, further strengthening the notion of HCV lymphotropism. Overall, the data accumulated suggest that occult HCV infection is a common consequence of resolution of symptomatic hepatitis C and that examination of the cells of the immune system is an effective approach to diagnosis of HCV infection and its long-term persistence. Further work is required to fully realize pathogenic and epidemiological consequences of occult HCV persistence.

From bed to bench: Which attitude towards the laboratory liver tests should health care practitioners strike?

There is a general consensus in re-interpreting the so-called liver function tests in the light of novel discoveries. At the same time, recent evidence favours the use of different laboratory data to assess liver damage, fibrosis or regenerative process, but this point is not always shared. Actually, balancing the need for diagnosis, prognostic evaluation and therapy response of liver disease with a good cost/benefit ratio is very difficult. New tests are probably not needed but the aim should be for better utilization of existing tests to contain the increasing cost of health care.