Early detection of hepatitis B surface antigen and detection of HBsAg mutants: a comparison of five assays

Laboratory Diagnosis and Monitoring of Viral Hepatitis

Many microbes, toxins, autoimmune diseases, and neoplastic diseases may cause liver inflammation; however, 5 viruses whose main pathogenesis is liver disease are referred to as hepatitis A, B, C, D, and E viruses. These viruses cause a significant burden of global illness. With the exception of hepatitis A virus, all may cause chronic infection potentially leading to cirrhosis and hepatocellular carcinoma. Excellent serologic and nucleic acid detection methods are available for determining the precise cause and, in some cases, the duration of infection. Diagnostics are critical for identifying individuals needing treatment and for monitoring the treatment success.

Characterization of overt and occult hepatitis B virus infection among HTLV-1 positive healthy carriers in the Northeast of Iran; AN HTLV-I endemic area

To date, no studies have provided data on hepatitis B virus (HBV) prevalence among asymptomatic, healthy human T-lymphotropic virus (HTLV-I) positive carriers. This sero- and molecular epidemiology study was performed on patients in the Northeast of Iran, which is an endemic area for HTLV-I infection. A total of 109 sera were collected from HTLV-I positive healthy carriers who were admitted to Ghaem Hospital, Mashhad City. All were tested for HBV serology and subsequently, real time PCR was carried out on the samples, regardless of the results of the serology. Standard PCR and direct sequencing were applied on positive samples. All cases were negative for HBsAg, Anti-HBc, and anti-HBs were positive in 34 (31.1%), and 35 (32%) individuals, respectively. There were 19 (17.4%) cases that were positive only for anti-HBs, and they had already received HBV vaccine. 16 (15%) were positive for both anti-HBs and anti-HBc, indicating a past-resolved HBV infection. 18 (16.5%) were isolated as anti-HBc, and 56 (51.3%) were negative for all HBV serological markers. Only one subject (0.9%) had detectable HBV DNA (2153 copy/ml), and assigned as being an occult HBV infection. The low prevalence of HBsAg, despite the high percentage of anti-HBc positive cases, might be related to the suppression effect of HTLV-I on surface protein expression. The low prevalence of HBV infection among HTLV-I positive healthy carriers from an endemic region, indicates that the epidemiology of HTLV-I and HBV coinfection is related to the endemicity of HBV in that region, rather than HTLV-I endemicity.

Prevalence of hepatitis B and C viral co-infections among HIV-1 infected individuals in Nairobi, Kenya

Background

Hepatitis B virus (HBV) and Hepatitis C virus (HCV) co-infections among HIV-1 infected individuals are growing worldwide health problems characterized by lack of effective vaccines, need for expensive treatment, chronicity of morbidity and associated mortality. Their prevalence and distribution patterns continue to vary across geographical locations with high prevalence being detected among high risk populations. To determine the prevalence of HBV and HCV among HIV-1 infected individuals, blood samples were collected from consenting study subjects visiting comprehensive HIV clinics in Nairobi during the period between October and December 2009.

Methods

Blood samples from volunteers were screened with ELISA tests for detecting HIV, HBV surface antigen (HBsAg) and anti-HCV antibodies.

Results

In a total of three (300) hundred infected individuals consisting of 129 (43%) males and 171 (57%) females 15.3% (46/300) were HIV-1 co-infected with either HBV or HCV or both, 10.3% (31/300) with HIV-1 and HCV and 6% (18/300) with HIV-1 and HBV infections. However, only three individuals (1%) were coinfected with the three viruses (HIV/HBV/HCV).

Conclusion

Though, low levels of co-infection with all three viruses were reported, there could be higher prevalence rates than reported here especially among high risk populations.

[Evaluation of indigenously manufactured immunochromatographic assay systems for rapid detection of hepatitis B surface antigen and antibody.]

BACKGROUND

We evaluated three indigenously produced immunochromatography (ICA) kits for the rapid detection of hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs) by comparing them with a microparticle enzyme immunoassay (MEIA).

METHODS

HBsAg and anti-HBs were tested by the ICA kits manufactured by three domestic companies, SD HBsAg and Anti-HBs (Standard Diagnostics, Inc., Yongin, Korea); Asan Easy Test(R) HBsAg and Anti-HBs (Asan Pharm Co., Ltd., Whasung, Korea); and GENEDIA(R) HBsAg Rapid Device and Anti-HBs Rapid Device (Green Cross MS, Inc., Yongin, Korea).

RESULTS

Results by ICA agreed completely with those of MEIA in all the 20 HBsAg-negative sera and in all the anti-HBs-negative sera except one sample. Among the 20 HBsAg-positive sera by MEIA, 17 were positive by ICA using Green Cross MS, 16 using Asan Pharm Co., and 13 using SD and reverse passive hemagglutination. Among the 20 anti-HBs-positive sera by MEIA, 19 were positive by ICA using Green Cross MS and Asan Pharm Co., 17 using SD, and 18 by passive hemagglutination. Elapsed time for the control and test line to be visualized in ICA might be longer and the color of the lines lighter when using SD than Green Cross MS or Asan Pharm Co.

CONCLUSIONS

Three indigenously produced ICA kits are as sensitive as MEIA for the detection of anti-HBs, but are less sensitive than MEIA for HBsAg. The ICA kits for the rapid detection of HBsAg might be recommended for a limited use in the clinical laboratory.

HBsAg variants: diagnostic-escape and diagnostic dilemma

A wide variety of commercial assays is available for the detection of hepatitis B surface antigen (HBsAg). Clearly, the sensitivity of an assay to detect a variant is dependent on the anti-HBs usage. Thus, it is not surprising that there are examples of variants that cannot be detected by all assays. Data from Europe, Asia and Africa about HBsAg variants which are not recognized by either monoclonal or polyclonal antibodies specific for wild-type group 'a' determinant, but positive by DNA polymerase chain reaction (PCR) in chronic patients and from vaccinated children are increasing. This would impose a challenge for public health issues of hepatitis B virus. In this review we tried to summarize the discrepancies between results of HBsAg assays and to explain some rationales for these inconsistencies.

Reducing the risk of hepatitis B virus transfusion-transmitted infection

Before 1970, approximately 6% of multi-transfused recipients acquired a transfusion-transmitted Hepatitis B virus (HBV) infection. The safety improvements since then have been tremendous. From a level of a few infections per 1000 donations, the risk today, depending on the screening algorithm and additional measurements performed, has decreased to around 1:500,000 to 1:1,000,000, an improvement greater than 1000-fold compared to 50 years ago. This enormous gain in safety has been achieved through many factors, including development of increasingly more sensitive Hepatitis B antigen (HBsAg) assays; the adoption in some countries of hepatitis B core antibody (anti-HBc) screening; an improved donor selection procedure; HBV vaccination programs; and finally the introduction of HBV nucleic acid testing (NAT). Because there is a tendency in transfusion medicine to add one safety measure on top of another to approach the ultimate goal of zero risks, costs become increasingly a matter of debate. It is obvious that any new measure in addition to existing methods or measures will have very poor cost effectiveness. Therefore each country needs to perform its own calculation based on the country’s own epidemiology, resources, political and public awareness of the risks, in order to choose the correct and most cost-efficient measures. Ideally, each country would make decisions regarding implementation of additional blood safety measures in the context of both the perceived benefit and the allocation of overall health care resources.

Hepatitis B virus transfusion risk in China: proficiency testing for the detection of hepatitis B surface antigen

Because of the high prevalence of Hepatitis B virus (HBV), HBsAg tests play an extremely significant role in donor screening in China. In our multicentre study, the HBsAg assays used in blood screening were evaluated for their analytical sensitivity and the ability to detect mutants. A panel of eight samples was sent to 85 blood banks. The panel included four HBsAg-positive serum samples at concentrations of 0·16, 0·46, 0·9 and 1·73 IU mL(-1) ; three recombinant HBsAg mutants (G145R, T131I and K141E) with defined concentrations and one negative sample. All laboratories were required to detect the samples with their routine procedures.All the 85 blood banks reported their results before the closing date, and 170 data sets were submitted. The wild-type samples at concentrations of 1·73 and 0·9 IU mL(-1) were correctly identified as positive in all data sets, whereas the other two samples (at concentrations 0·16 and 0·46 IU mL(-1) ) were not consistently detected as positive. Regarding the mutants, significantly different results were reported among all the assays involved. All users of Hepanostika HBsAg Ultra and most users (16/17) of Abbott Murex HBsAg Version 3 detected all mutant samples, whereas some of the commercial assays failed to detect any of the three mutant samples. Some HBsAg assays with unsatisfactory sensitivities and capabilities of mutant detection were used by a large percentage of blood banks, which might lead to a high transfusion risk in China. A list of assays of high sensitivity and good ability of mutant detection should be recommended for use in blood screening.

Differential reactivity of mouse monoclonal anti-HBs antibodies with recombinant mutant HBs antigens

AIM: To investigate the reactivity of a panel of 8 mouse anti-hepatitis B surface antigen (HBsAg) monoclonal antibodies (mAbs) using a collection of 9 recombinant HBsAg mutants with a variety of amino acid substitutions mostly located within the “a” region.

METHODS: The entire HBs genes previously cloned into a mammalian expression vector were transiently transfected into COS7 cells. Two standard unmutated sequences of the ayw and adw subtypes served as controls. Secreted mutant proteins were collected and measured by three commercial diagnostic immunoassays to assess transfection efficiency. Reactivity of anti-HBs mAbs with mutated HBsAgs was determined by sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS: Reactivity of anti-HBs mAbs with mutated HBsAgs revealed different patterns. While three mutants reacted strongly with all mAbs, two mutants reacted weakly with only two mAbs and the remaining proteins displayed variable degrees of reactivity towards different mAbs. Accordingly, four groups of mAbs with different but overlapping reactivity patterns could be envisaged. One group consisting of two mAbs (37C5-S7 and 35C6-S11) was found to recognize stable linear epitopes conserved in all mutants. Mutations outside the “a” determinant at positions 120 (P→S), 123(T→N) and 161 (M→T) were found to affect reactivity of these mAbs.

CONCLUSION: Our findings could have important implications for biophysical studies, vaccination strategies and immunotherapy of hepatitis B virus (HBV) mutants.

Evaluation of 17 CE-marked HBsAg assays with respect to clinical sensitivity, analytical sensitivity, and hepatitis B virus mutant detection

Seventeen HBsAg assays, in use in the European market (CE-marked), were assessed for their diagnostic sensitivity using 38 commercially available seroconversion panels, and for their analytical sensitivity with the HBsAg ad and ay standards of the Paul-Ehrlich-Institut (PEI). In addition, the ability to detect HBsAg mutants was investigated by means of 21 recombinant HBsAg mutant samples and 5 natural mutants. Analysis of seroconversion data revealed that there were marked differences in the sensitivity among the CE-marked HBsAg assays. Differences in the window period between the most and the least sensitive assays were up to 2 weeks. Analytical sensitivities of the investigated assays ranged from 0.009 to 0.05 PEI-U/ml for HBsAg ad standard (relating to approximately 0.018 to 0.100 IU/ml of the 2nd WHO HBsAg standard) and 0.012 to 0.11 PEI-U/ml for the ay standard. Clinical and analytical sensitivities were basically correlated. The capacity to detect mutant HBsAg forms was influenced by the assay format and the properties of the monoclonal antibodies used for coating of the solid phase or in the conjugate. While some assays detected all mutants others exhibited weaknesses especially in recognising HBsAg mutations affecting loop 2 of the HBsAg a-determinant. The results obtained with the recombinant mutants were largely confirmed by the investigation of clinical samples. The study gives a broad overview of the current state of the art of about 70% of the HBsAg assays currently available in Europe. The overall sensitivity has not been improved further since 1995 when the most sensitive assay was introduced into the market. In addition, detection of HBsAg mutants seems problematic with several assays. It is concluded that there is potential to improve clinical sensitivity and mutant recognition of HBsAg assays.

Hepatitis B virus blood screening: unfinished agendas

The risk of transfusion-transmitted hepatitis B virus (TTHBV) has been steadily reduced through the use of volunteer donors, enhanced donor questioning, and increasingly sensitive hepatitis B surface antigen (HBsAg) tests. In a few countries, screening by antibody to hepatitis B core antigen (anti-HBc) and/or hepatitis B virus (HBV) nucleic acid amplification tests (NAT) has also been introduced. Nevertheless, the risk of TTHBV in most countries is higher than the risk of either human immunodeficiency virus-1 (HIV-1) or hepatitis C virus (HCV). HBV screening practices vary both in terms of the markers screened and the tests employed, and are often dependent on a country's healthcare resources. Anti-HBc screening could be employed as an additional safety feature in HBV low-prevalence countries, but would lead to the rejection of a high percentage of otherwise acceptable donations in HBV moderate- and high-prevalence countries. It has been argued that only individual-donor HBV NAT testing would substantially reduce the risk of TTHBV beyond that achieved by the most sensitive HBsAg tests. However, studies from countries with low, moderate and high HBV prevalence have demonstrated NAT yield from window period- and late stage HBV-infected donors, even using minipool testing following the most sensitive HBsAg tests.

HBV virological assessment

Management of hepatitis B virus (HBV) infected patients involves serological diagnosis, quantitation of HBV-DNA and measurement of HBV drug resistance. Different serological markers such as HBsAg, anti-HBs, anti-HBc (total and IgM), HBeAg and anti-HBe are assessed by immunoassays in order to define the infection status. The emergence of surface mutants however is a continuous challenge to design more effective immunoassays. Commercially available quantitative HBV-DNA assays with increased sensitivity and wider linear range give a more accurate estimate of viral replication and contribute decisively in the initiation and the monitoring of the response to HBV therapy. Genotypic drug resistance assays are important diagnostic tools, since the administration of nucleoside/nucleotide analogues to HBV infected patients leads to the development of drug resistance patterns very much dependent on the treatment regimen. Special issues have to be taken into consideration regarding HBV/HIV-1 co-infected patients, since concominant HIV and HBV replication results in higher rates of HBV replication. Current efforts are focused on the standardization of HBV-DNA assays (qualitative and quantitative), of HBV drug resistance assays as well as in the development of new assays and markers that will help in the prognosis and management of HBV infection (quantitative detection of pre-core mutants and HBV ccc-DNA assays).

Detecting hepatitis B surface antigen mutants

Hepatitis B viral mutants can emerge in patients as a result of selection pressure from either immune response or treatment options. Mutations that occur within the immunodominant epitopes of hepatitis B surface antigen (HBsAg) allow mutant virus to propagate in the presence of a neutralizing immune response, while wild-type virus is reduced to undetectable levels. HBsAg mutants present as false-negative results in some immunoassays. An understanding of immunoassay reactivity with HBsAg mutants is key to establishing an appropriate testing algorithm for hepatitis B virus detection programs.

A new HBsAg screening assay designed for sensitive detection of HBsAg subtypes and variants

The design of a new HBsAg screening assay, the Hepanostika HBsAg Ultra is based on the use of monoclonal antibodies raised against native wild-type HBsAg and reactive with HBsAg in which the common 'a'-determinant is modified by site-directed mutagenesis of four of the cysteine moieties. The design was checked using the same cysteine variants and samples from patients known to be infected with HBsAg variants. The results found were compared with other state-of-the-art commercial screening assays. The design of the Hepanostika HBsAg Ultra enabled detection of all variant HBsAg-positive samples in contrast to the other commercial assays. An additional 980 samples were tested to assess the specificity and sensitivity of the Hepanostika HBsAg Ultra. Screening of presumed negative serum and plasma samples resulted in a specificity of 100%. This makes the Hepanostika HBsAg Ultra the first screening assay with a design able to detect HBsAg variants with high sensitivity and specificity.

Detecting Hepatitis B Surface Antigen Mutants

Hepatitis B viral mutants can emerge in patients as a result of selection pressure from either immune response or treatment options. Mutations that occur within the immunodominant epitopes of hepatitis B surface antigen (HBsAg) allow mutant virus to propagate in the presence of a neutralizing immune response, while wild-type virus is reduced to undetectable levels. HBsAg mutants present as false-negative results in some immunoassays. An understanding of immunoassay reactivity with HBsAg mutants is key to establishing an appropriate testing algorithm for hepatitis B virus detection programs.

Epitope mapping of recombinant hepatitis B surface antigen by murine monoclonal antibodies

Hepatitis B surface antigen (HBsAg) induces a potent protective antibody response in immunized healthy individuals. The antibody response in humans is largely directed to a restricted conformational immunodominant region of HBsAg, identified as "a" determinant. Our aim was generation and characterization of murine monoclonal antibodies (MAbs) against recombinant HBsAg and their use for epitope mapping of the antigen. Hybridoma cells were established from Balb/c mice immunized with recombinant HBsAg of the "adw" subtype and cloned by limiting dilution. Specificity of MAbs was studied by indirect ELISA and immunoblotting. Topology of the epitopes was analyzed by competitive and inhibition ELISA. Eight hybridoma clones producing MAbs specific for the immunogen were established. Five of the MAbs recognized overlapping conformational epitopes, whereas the remaining three MAbs were found to identify linear epitopes. Cross-inhibition studies suggest recognition of mutually exclusive epitopes by these MAbs. Our data suggest that, similar to the human system, the mouse antibody response is largely directed to restricted conformational overlapping epitopes of HBsAg.

Diversity and origin of hepatitis B virus in Dutch blood donors

Two considerations led us to study the genetic diversity and origin of hepatitis B virus (HBV) in Dutch blood donors. Firstly, an HBV-infected Dutch blood donor was found negative by four assays used commonly for detection of HBV surface antigen (HBsAg). How variable is HBsAg among HBV infected blood donors? Secondly, the WHO recommends universal vaccination against HBV, but north-west European countries limit vaccination to groups at risk of HBV. This policy may reduce hepatitis B among low-risk, unvaccinated persons if HBV strains that infect low-risk persons stem from local at-risk groups. Studying the nucleotide sequence of the S-gene of HBV from 63 Dutch blood donors, considerable variation was found. The majority of the donor strains (52/63, 83%) appears closely related to local HBV isolates as present in intravenous drug users, immigrants, and homosexual men. The remaining 11 (17%) HBV strains belong to various non-Western genotypes. This implies that an indigenous Dutch HBV strain (heterosexually transmitted, not associated with intravenous drug abuse, or immigrants) does not exist, and it supports the policy in low endemic countries to limit vaccination to at-risk groups. On the other hand, it must be realised that, after 20 years of vaccination of at-risk groups, HBV still circulates in the at-risk groups and Dutch blood donors acquire the HBV strains involved.

Sensitive detection of HBsAg mutants by a gap ligase chain reaction assay

Hepatitis B virus (HBV) surface gene variants have been associated with diagnostic escape and immune escape following vaccination. The most common mutation observed in these variants is a glycine-to-arginine substitution at amino acid 145 (G145R). In order to sensitively detect the presence of this mutant in serum, a new molecular detection system was developed; in this new system, a gap ligase chain reaction (gLCR) assay was coupled with electrochemiluminescence detection of reaction products. The gLCR assay could detect approximately 10 copies of mutant DNA and could discriminate low levels of mutant DNA in the presence of excess wild-type DNA. Detection of the G145R mutant in clinical specimens was evaluated by testing 56 suspect serum specimens. The G145R mutation was observed in 18 of 28 HBV-DNA-positive samples. The approximate percentage of mutant present in each specimen was calculated by comparison with a standard curve of an increasing ratio of mutant DNA to wild-type DNA. Most samples contained a very low percentage of mutant virus (approximately 5%), with an observed range of approximately 3 to 74%. The G145R mutation was most frequently observed in specimens producing a diagnostic anomaly or from transplant patients but was also observed in specimens from vaccinated individuals and specimens in which HBsAg diagnostic escape was suspected. Therefore, the gLCR assay is a sensitive and specific method for detection of G145R mutants, which could be modified to include the detection of other HBV mutants.