Management of hepatitis B virus (HBV) reactivation in patients with resolved HBV infection based on a highly sensitive HB core-related antigen assay

Current global applications of HBcrAg assays in the management of chronic hepatitis B

Hepatitis B core-related antigen (HBcrAg) is a vital marker for monitoring chronic hepatitis B (CHB) as it correlates with hepatitis B (HBV) DNA and covalently closed circular DNA (cccDNA). The iTACT-HBcrAg assay, approved in Japan, provides highly sensitive and automated testing, reducing patient burden by requiring smaller specimen volumes and offering shorter processing times. Crucial for managing HBV reactivation and predicting hepatocellular carcinoma, it delivers consistent and reliable results. In resource-limited regions, the HBcrAg-rapid diagnostic test (HBcrAg-RDT) facilitates early HBV detection and management. This point-of-care testing (POCT) tool requires no specialized equipment and provides results within 30 minutes, making it invaluable in areas lacking HBV DNA quantification. Trials in West Africa, Asia, and other developing regions demonstrate its sensitivity and specificity. Together, these advancements in iTACT-HBcrAg and HBcrAg-RDT assays enhance CHB patient care and contribute significantly to the global effort to eliminate HBV as a public health threat.

Clinical usefulness of an ultra-high-sensitivity hepatitis B surface antigen assay to determine the cessation of treatment for HBV reactivation

INTRODUCTION AND OBJECTIVES

We aimed to compare the usefulness of the ultra-high-sensitivity hepatitis B surface antigen (iTACT-HBsAg), high-sensitivity hepatitis B core-related antigen (iTACT-HBcrAg), and anti-HBs assays in determination of cessation of nucleot(s)ide analogue (NA) treatment to prevent against hepatitis B virus (HBV) reactivation.

PATIENTS AND METHODS

Twenty-two patients who developed HBV reactivation under immunosuppressive therapy or chemotherapy and had been administered NA and subsequently discontinued were enrolled. The stored serum samples taken at NA cessation were applied to iTACT-HBsAg (lower limit of detection; 0.0005 IU/mL), iTACT-HBcrAg (lower limit of detection; 2.1 log U/mL), and anti-HBs assays. Detection of serum HBV DNA level ≥1.3 log IU/mL after NA cessation was defined as virological relapse (VR).

RESULTS

Two patients were excluded due to re-introduction of NA despite a negligible level of HBV DNA (<1.3 log IU/mL). Of the remaining 20 patients, 11 (55 %) had HBcrAg <2.1 log U/mL at the cessation of NA, and 7 of the 11 patients (64 %) had no VR thereafter. On the other hand, 15 patients (75 %) had HBsAg <0.0005 IU/mL at the cessation of NA, and 13 of the 15 patients (87 %) subsequently lacked VR. Further, 12 patients (60 %) had anti-HBs ≥10 mIU/mL at the cessation of NA, and 10 of the 12 patients (83 %) had no VR thereafter. The iTACT-HBsAg assay had the highest positive predictive value and the best overall diagnostic performance for predicting non-VR after cessation of NA.

CONCLUSIONS

The iTACT-HBsAg assay was useful to determine the cessation of NA treatment to prevent against HBV reactivation.

Two Concepts of Hepatitis B Core-Related Antigen Assay: A Highly Sensitive and Rapid Assay or an Effective Tool for Widespread Screening

Hepatitis B core-related antigen (HBcrAg) reflects the activity of intrahepatic covalently closed circular DNA. HBcrAg can be detected even in chronic hepatitis B patients in whom serum HBV DNA or hepatitis B surface antigen is undetectable. The HBcrAg measurement system was developed based on two concepts. One is a fully-automated and highly-sensitive HBcrAg assay (iTACT-HBcrAg) and the other is a point-of-care testing (POCT) that can be used in in resource-limited areas. iTACT-HBcrAg is an alternative to HBV DNA for monitoring HBV reactivation and predicting the development of hepatocellular carcinoma. This validated biomarker is available in routine clinical practice in Japan. Currently, international guidelines for the prevention of mother-to-child transmission recommend anti-HBV prophylaxis for pregnant women with high viral loads. However, over 95% of HBV-infected individuals live in countries where HBV DNA quantification is widely unavailable. Given this situation, a rapid and simple HBcrAg assay for POCT would be highly effective. Long-term anti-HBV therapy may have potential side effects and appropriate treatment should be provided to eligible patients. Therefore, a simple method of determining the indication for anti-HBV treatment would be ideal. This review provides up-to-date information regarding the clinical value of HBcrAg in HBV management, based on iTACT-HBcrAg or POCT.

Clinical Significance and Remaining Issues of Anti-HBc Antibody and HBV Core-Related Antigen

Currently, hepatitis B virus (HBV) core antibody (anti-HBc antibody) and HBV core-related antigen (HBcrAg) are widely used as serum markers for diagnosis based on the HBV core region. This review focused on anti-HBc antibodies and HBcrAg and aimed to summarize the clinical significance of currently used assay systems and the issues involved. While anti-HBc is very significant for clinical diagnosis, the clinical significance of quantitative assay of anti-HBc antibody has been reevaluated with improvements in diagnostic performance, including its association with clinical stage and prediction of carcinogenesis and reactivation. In addition, concerning the new HBcrAg, a high-sensitivity assay method has recently been established, and its diagnostic significance, including the prediction of reactivation, is being reevaluated. On the other hand, the quantitative level of anti-HBc antibody expressed in different units among assay systems complicates the interpretation of the results. However, it is difficult to standardize assay systems as they vary in advantages, and caution is needed in interpreting the assay results. In conclusion, with the development of highly sensitive HBcrAg and anti-HBc antibody, a rapid and sensitive detection assay system has been developed and used in clinical practice. In the future, it is hoped that a global standard will be created based on the many clinical findings.

Hepatitis B core-related antigen: A novel and promising surrogate biomarker to guide anti-hepatitis B virus therapy

The current requirement for biomarkers to detect hepatitis B virus (HBV) infection is polarized. One is a fully-automated and highly sensitive measurement system; the other is a simple system for point-of-care testing (POCT) in resource-limited areas. Hepatitis B core-related antigen (HBcrAg) reflects intrahepatic covalently closed circular DNA and serum HBV DNA. Even in patients with undetectable serum HBV DNA or HBsAg loss, HBcrAg may remain detectable. Decreased HBcrAg levels are associated with reduction of the occurrence of hepatocellular carcinoma (HCC) in chronic hepatitis B. Recently, a fully-automated, novel high-sensitivity HBcrAg assay (iTACT-HBcrAg, cut-off value: 2.1 logIU/mL) has been developed. This attractive assay has been released in Japan very recently. iTACT-HBcrAg can be useful for monitoring HBV reactivation and prediction of HCC occurrence, as an alternative to HBV DNA. Moreover, monitoring HBcrAg may be suitable for determining the therapeutic effectiveness of approved drugs and novel drugs under development. Presently, international guidelines recommend anti-HBV prophylaxis for pregnant women with high viral loads to prevent mother-to-child transmission of HBV. However, >95% of HBV-infected individuals live in countries where HBV DNA quantification is not available. Worldwide elimination of HBV needs the scaling-up of examination and medication services in resource-limited areas. Based on this situation, a rapid and easy HBcrAg assay as a POCT is valuable. This review provides the latest information regarding the clinical use of a new surrogate marker, HBcrAg, in HBV management, based on iTACT-HBcrAg or POCT, and introduces novel agents targeting HBV RNA/protein.

Hepatitis B Core Antibody Level: A Surrogate Marker for Host Antiviral Immunity in Chronic Hepatitis B Virus Infections

The hepatitis B virus core protein (HBcAg) is a highly immunogenic particulate antigen. Nearly all patients with persistent or resolved hepatitis B virus (HBV) infection show seropositivity for hepatitis B core antibody (anti-HBc), which appears in the early stage of infection and is mostly present for life. Traditionally, the anti-HBc is regarded as an evidential serological marker of HBV infections. In the last ten years, several studies revealed the predictive value of quantitative anti-HBc (qAnti-HBc) level in the treatment response and clinical outcome of chronic HBV infections, implying new insights into this classic marker. Overall, qAnti-HBc should be regarded as an indicator of the host's immune response specific to HBV, which correlates with HBV-related hepatitis activity and liver pathology. This review summarized the latest understanding of the clinical values of qAnti-HBc for differentiating the CHB phase, predicting treatment response, and providing disease prognosis. Moreover, we also discussed the possible mechanism of qAnti-HBc regulation during different courses of HBV infection.

A longitudinal study to detect hepatitis B surface and core-related antigens in chronic hepatitis B patients with hepatitis B surface antigen seroclearance using highly sensitive assays

BACKGROUND

This study aimed to evaluate the usefulness of two novel assays, namely the iTACT-hepatitis B surface antigen (iTACT-HBsAg) and iTACT-hepatitis B core-related antigen (iTACT-HBcrAg) assays, in chronic hepatitis B (CHB) patients with HBsAg seroclearance (SC) documented by standard assays.

METHODS

HBsAg and HBcrAg were measured by the two iTACT-assays in 556 serial sera collected from 96 CHB patients at 7 different time points spanning from 5 years before to 10 years after SC and 120 HBsAg-negative, anti-HBc-positive individuals. As controls, 60 seronegative individuals, who were negative for HBsAg, anti-HBc and anti-HBs, were tested.

RESULTS

Using the iTACT-assays, HBsAg was detectable in 154/418 (36.8%) samples collected after SC. HBcrAg was detectable in 78.3% and 65.9% of samples collected before and after SC, respectively. The detectability rates of both HBsAg and HBcrAg progressively decreased over time after SC. At 10 years after SC, 20.4% and 64.5% of the patients still had detectable HBsAg and HBcrAg, respectively. 66 (71%) patients had detectable HBsAg and/or HBcrAg. Among the 120 HBsAg-negative, anti-HBc-positive individuals, 11 (9.2%) and 4 (3.3%) had detectable HBsAg and HBcrAg respectively. Both HBsAg and HBcrAg were undetectable in the controls.

CONCLUSION

The iTACT assays detected a low level of HBsAg and/or HBcrAg in >70% of patients even at 10 years after SC, suggesting that CHB patients with SC still harbour a low level of HBV protein expression. The clinical significance of detectable viral proteins after SC with regard to disease progression and HBV reactivation deserves further investigations.

Outcome of nucleos(t)ide analog cessation in patients with treatment for prevention of or against hepatitis B virus reactivation

AIM

We retrospectively investigated patients with administration of nucleos(t)ide analogs (NAs) for prevention of or against hepatitis B virus (HBV) reactivation, and their clinical outcomes after cessation of the NA.

METHODS

We enrolled 180 patients who were positive for HBsAg when they started immunosuppressive therapy or chemotherapy and an NA was administered to prevent HBV reactivation (HBV carrier group), and 82 patients with resolved HBV infection who started administration of an NA after HBV reactivation (de novo HBV group). Cessation of the NA depended on each physician's judgment without definite criteria.

RESULTS

A total of 27 patients in the HBV carrier group and 22 in the de novo HBV group stopped NA therapy. In the HBV carrier group, 16 patients experienced virological relapse, which was defined as HBV DNA levels ≥20 IU/ml, and one with hematological disease had an alanine aminotransferase flare after cessation of NA. Of the 16 patients, the NA was reintroduced in three, whereas, the remaining 13 had low levels of HBV DNA and no alanine aminotransferase flare. In the de novo HBV group, virological relapse occurred in six patients, and one with hematological disease had an alanine aminotransferase flare after cessation of the NA. The NA was reintroduced in four of the six patients.

CONCLUSIONS

We may be able to consider to cease NA therapy proactively in HBV carriers and resolved patients with non-hematological disease, if their primary diseases are under remission after completion of immunosuppressive therapy or chemotherapy. However, careful follow up is necessary after stopping NA therapy.