Recent developments in the diagnosis and monitoring of HBV infection and role of the genetic variability of the S gene

Liver organoids as a primary human model to study HBV-mediated Hepatocellular carcinoma. A review

Hepatitis B Virus (HBV) is the prevailing cause of chronic liver disease, which progresses to Hepatocellular carcinoma (HCC) in 75% of cases. It represents a serious health concern being the fourth leading cause of cancer-related mortality worldwide. Treatments available to date fail to provide a complete cure with high chances of recurrence and related side effects. The lack of reliable, reproducible, and scalable in vitro modeling systems that could recapitulate the viral life cycle and represent virus-host interactions has hindered the development of effective treatments so far. The present review provides insights into the current in-vivo and in-vitro models used for studying HBV and their major limitations. We highlight the use of three-dimensional liver organoids as a novel and suitable platform for modeling HBV infection and HBV-mediated HCC. HBV organoids can be expanded, genetically altered, patient-derived, tested for drug discovery, and biobanked. This review also provides the general guidelines for culturing HBV organoids and highlights their several prospects for HBV drug discovery and screening.

Development of sensitive and specific loop-mediated isothermal amplification combined with lateral flow device for the rapid detection of hepatitis B virus infection

Hepatitis B virus is a highly infectious blood borne microbial pathogen that causes several hepatic complications like liver cirrhosis and hepatocellular carcinoma. Several methods are available for the detection of HBV, but every method has their own merits and demerits, which restrict their use in clinical laboratories. The aim of this present study is the development of rapid, inexpensive, sensitive, and specific loop-mediated isothermal amplification followed by lateral flow device (LFD) for detection of HBV in blood specimens.

METHODS

HBV standard plasma panels and donor plasma specimens were used to evaluate the assay. HBV DNA was extracted by using QiAamp DNA Blood Mini Kit. Amplification was carried out at constant temperature 63 °C for 60 min. LAMP end products were analyzed by using ESE LAMP tube scanner, gel electrophoresis, UV-lamp, and lateral flow device.

RESULTS

HBV-LAMP-LFD assay revealed sensitivity of 92% (138/150) of HBV positive plasma specimens. Specificity of HBV-LAMP-LFD was calculated 100%.

CONCLUSION

Our study concludes that HBV-LAMP-LFD is rapid, easy to use, sensitive, and specific point-of-care diagnostic assay for the detection of hepatitis B virus in blood samples. This assay can be used in resource-limited settings as well as in HBV endemic areas.

A Study on Hepatitis B Viral Seromarkers and Associated Risk Factors among the Patients Suffering from Acute and Chronic Hepatitis B Infection

Background:

Hepatitis B viral infection is the most common cause of hepatitis, and it leads to serious liver diseases such as cirrhosis and hepatocellular carcinoma.

Aim:

The aim of the study is to differentiate acute hepatitis B and chronic hepatitis B (CHB) among patients seropositive for hepatitis B surface antigen (HBsAg).

Materials and Methods:

This study was carried out in the Department of Microbiology, Chettinad Hospital and Research Institute, Kelambakkam, Tamil Nadu, India, for a period of 6 months (January 2018–June 2018). Blood samples were collected from 87 patients for the detection of hepatitis B virus (HBV) serological markers. HBsAg, hepatitis B e antigen (HBeAg), anti-HBc total, anti-HBc IgM, and antibody to hepatitis B surface antigen were screened using the ELISA method. Detailed demographic profile including history of previous hepatitis infection, previous blood transfusion, and other related details were collected and documented using a structured questionnaire.

Results:

A total of 87 patients were HBsAg seropositive; among them, 55 (63.2%) were male and 32 (36.9%) were female. Based on the serological markers tested, 24 and 63 were suffering from acute and chronic HBV infections, respectively. Among the acute hepatitis B patients, all samples were seropositive for HBsAg, anti-HBc total, and anti-HBc IgM. HBeAg seromarker was found in 15 patients (62.5%). Among the CHB patients, all samples were seropositive for HBsAg and anti-HBc total. HBeAg seromarker was found in 28 patients with 44.4%. Alcohol consumption was the major risk factor for the transmission of HBV infection.

Conclusion:

An increased sample size and detailed study of high-risk behavior will provide an alarming awareness of their association.

Label free hepatitis B detection based on serum derivative surface enhanced Raman spectroscopy combined with multivariate analysis

Surface-enhanced Raman spectroscopy (SERS) was developed here for the non-invasive detection of the hepatitis B virus (HBV). Chronic hepatitis B virus (HBV) infection is a primary health problem in the world and may further develop into cirrhosis and hepatocellular carcinoma (HCC). SERS measurement was applied to two groups of serum samples. One group included 93 HBV patients and the other group included 94 healthy volunteers as control subjects. Tentative assignments of the Raman bands in the measured SERS spectra have shown the difference of the serum SERS spectra between HBV patients and healthy volunteers. The differences indicated an increase in the relative amounts of L-arginine, Saccharide band (overlaps with acyl band), phenylalanine and tyrosine, together with a decrease in the percentage of nucleic acid, valine and hypoxanthine in the serum of HBV patients compared with those of healthy volunteers. For better analysis of the spectral data, the first-order derivation was applied to the SERS data. Furthermore, principal components analysis (PCA), combined with linear discriminant analysis (LDA), were employed to distinguish HBV patients from healthy volunteers and to realize the diagnostic sensitivity of 78.5% and 91.4%, and specificity of 75% and 83% for SERS and the first order derivative SERS spectrum, respectively. These results suggest that derivative analysis could be an effective method to improve the classification of SERS spectra belonging to different groups. This exploratory work demonstrated that first-order derivative serum SERS spectrum combined with PCA-LDA has great potential for improving the detection of HBV.

Interaction of S17 Antibody with the Functional Binding Region of the Hepatitis B Virus Pre-S2 Epitope

To understand the mechanism for inhibition of hepatitis B virus (HBV) infection is important. In this study, single-chain variable fragment (scFv) antibodies were generated and directed to the pre-S2 epitope of HBV surface antigen (HBsAg). These human scFvs were isolated from a person with history of HBV infection by phage display technology. An evaluation of panning efficiency revealed that the eluted phage titer was increased, indicating that specific clones were enriched after panning. Selected scFvs were characterized with the recombinant HBsAg through Western blotting and enzyme-linked immunosorbent assay to confirm the binding ability. Flow cytometry analysis and immunocytochemical staining revealed that one scFv, S17, could recognize endogenous HBsAg expressed on the HepG2215 cell membrane. Moreover, the binding affinity of scFv S17 to the pre-S2 epitope was determined to be 4.2 × 10^-8 M. Two ion interactions were observed as the major driving forces for scFv S17 interacting with pre-S2 by performing a rational molecular docking analysis. This study provides insights into the structural basis to understand the interactions between an antibody and the pre-S2 epitope. The functional scFv format can potentially be used in future immunotherapeutic applications.

An ultra-sensitive Abbott ARCHITECT® assay for the detection of hepatitis B virus surface antigen (HBsAg)

BACKGROUND

Critical to the identification of HBV infection and the prevention of transfusion transmitted disease is the sensitive and accurate detection of Hepatitis B virus surface antigen (HBsAg). Improvements in HBsAg assay sensitivity approaching the performance of nucleic acid testing (NAT) are essential to further reduce the detection window for acute HBV infection in regions where NAT is not widely available.

OBJECTIVES AND STUDY DESIGN

An improved HBsAg assay on the fully-automated Abbott ARCHITECT^® platform was developed to improve sensitivity, mutant and genotype detection.

RESULTS

The analytical sensitivity of the improved prototype assay is 5.2 mIU/ml, which is 3.86- to 14.54-fold more sensitive than comparator assays based on the WHO International Reference Standard. The enhanced sensitivity was also demonstrated with 27 HBV seroconversion panels, detecting more panel members (191 of 364) vs. the ARCHITECT^® Qual I (144), Qual II (160) and PRISM^® (148) HBsAg assays. Further, the assay detected 7 of 12 HBV DNA positive/HBsAg negative samples, and detected all evaluated mutants and genotypes with higher sensitivity than the comparator assays. The improvement in sensitivity did not diminish assay specificity, attaining 100% (95% CI, 99.97-100%) on 10,633 blood donors.

CONCLUSIONS

An Abbott ARCHITECT^® HBsAg assay with clinical performance approaching that of mini-pool NAT (approximately 100 copies/ml was developed. The assay has superior HBsAg mutant and genotype detection and specificity, all of which are important for the diagnosis and management of HBV infection.

The Role of Affordable, Point-of-Care Technologies for Cancer Care in Low- and Middle-Income Countries: A Review and Commentary

As the burden of non-communicable diseases such as cancer continues to rise in low- and middle-income countries (LMICs), it is essential to identify and invest in promising solutions for cancer control and treatment. Point-of-care technologies (POCTs) have played critical roles in curbing infectious disease epidemics in both high- and low-income settings, and their successes can serve as a model for transforming cancer care in LMICs, where access to traditional clinical resources is often limited. The versatility, cost-effectiveness, and simplicity of POCTs warrant attention for their potential to revolutionize cancer detection, diagnosis, and treatment. This paper reviews the landscape of affordable POCTs for cancer care in LMICs with a focus on imaging tools, in vitro diagnostics, and treatment technologies and aspires to encourage innovation and further investment in this space.

Diagnosis of hepatitis B

Hepatitis B virus (HBV) infection is a major global health problems leading to severe liver disease such as cirrhosis and hepatocellular carcinoma (HCC). HBV is a circular, partly double-stranded DNA virus with various serological markers: hepatitis B surface antigen (HBsAg) and anti-HBs, anti-HBc IgM and IgG, and hepatitis B e antigen (HBeAg) and anti-HBe. It is transmitted by sexual, parenteral and vertical route. One significant method to diminish the burden of this disease is timely diagnosis of acute, chronic and occult cases of HBV. First step of HBV diagnosis is achieved by using serological markers for detecting antigens and antibodies. In order to verify first step of diagnosis, to quantify viral load and to identify genotypes, quantitative or qualitative molecular tests are used. In this article, the serological and molecular tests for diagnosis of HBV infection will be reviewed.

HIV therapy with unknown HBV status is responsible for higher rate of HBV genome variability in Ethiopia

BACKGROUND

In Ethiopia, HBV and HIV are co-circulating. Since patients are not routinely tested for HBV, the use of antiretroviral drugs could contribute to unintended HBV drug resistance and surface gene variability during HIV coinfection.

METHODS

A total of 161 hepatitis B surface antigen (HBsAg)-positive sera from 58 HIV-coinfected and 103 drug-naive HBV-monoinfected individuals were characterized for HBV drug resistance and immune escape HBsAg variants. HBV polymerase/surface gene fragment of 716 bp was analysed by direct sequencing.

RESULTS

In 34 out of 161 study subjects (21.1%) HBV drug resistance mutations (DRMs) were detected with a frequency of 3.1% rtL80F/I, 0.6% rtA181V, 1.2% rtT184S, 6.2% rtV173L, 10.6% rtL180M, 10.6% rtM204V/I and 8.1% rtI233V. The prevalence of the major DRMs in HBV-HIV-coinfected individuals was significantly higher than monoinfected individuals (41.4% versus 10.7%). Lamivudine selected DRMs, that is, rtL180M (29.3%) and rtM204V/I (29.3%) and rtV173L (15.5%) were more prevalent in HBV-HIV-coinfected individuals but absent in HBV-monoinfected individuals. Despite the finding that rtL180M and rtM204V/I were higher among ART-experienced individuals, the overall prevalence of DRMs (48.0% versus 36.4%) showed no significance difference among antiretroviral therapy (ART) status. The study also revealed higher frequency and heterogeneity of putative and known immune escape HBsAg mutations both in the major hydrophilic region (MHR; 68.3%) and outside the MHR (82.5%) of the surface gene. In particular, the 'a' determinant surface gene mutations (sT125S, sA128V, sQ129H/R, sT131I, sC137S, sT143M, sD144D/E, sG145R, sT148P) and the majority of clustered/multiple as well as drug selected immune escape HBsAg mutations were more prevalent in HBV-HIV-coinfected individuals.

CONCLUSIONS

HIV therapy without HBV co-management in Ethiopia fosters emergence and circulation of HBV variants of public health importance. It is highly recommended to include HBV testing and co-management as part of routine HIV care programmes for a better ART selection.

Genetic variation of occult hepatitis B virus infection

Occult hepatitis B virus infection (OBI), characterized as the persistence of hepatitis B virus (HBV) surface antigen (HBsAg) seronegativity and low viral load in blood or liver, is a special form of HBV infection. OBI may be related mainly to mutations in the HBV genome, although the underlying mechanism of it remains to be clarified. Mutations especially within the immunodominant “α” determinant of S protein are “hot spots” that could contribute to the occurrence of OBI via affecting antigenicity and immunogenicity of HBsAg or replication and secretion of virion. Clinical reports account for a large proportion of previous studies on OBI, while functional analyses, especially those based on full-length HBV genome, are rare.

Enhancement of PCR Detection Limit by Single-Tube Restriction Endonuclease-PCR (RE-PCR)

BACKGROUND

Polymerase chain reaction (PCR) is widely used in biological research and diagnostics because of its high sensitivity and specificity. However, the sensitivity of PCR is strongly influenced by topological characteristics of the template. Supercoiled templates are known to inhibit PCR, whereas linearized forms of the same supercoiled templates facilitate PCR.

OBJECTIVES

This study was conducted to compare the PCR efficiency of circular supercoiled DNA templates to their restriction endonuclease (RE)-mediated linearized forms. Additionally, we also evaluated the possibility of RE digestion of the circular supercoiled templates within the complete PCR buffer.

METHODS

Following a systematic approach, we demonstrated that circular supercoiled templates could be efficiently linearized by RE in the complete PCR buffer itself. This allowed linearization of circular supercoiled templates and their subsequent amplification in the PCR buffer in a single-tube format.

RESULTS

Using this extremely simple RE-PCR approach, we documented up to tenfold increases in detection efficiency of PCR with two different circular supercoiled templates of clinical origin, including an international calibration standard.

CONCLUSIONS

This inexpensive and easy approach to increasing PCR sensitivity can be easily adapted to any standard PCR protocol aimed at amplifying circular supercoiled genomes. Apart from its application in the development of sensitive clinical diagnostic PCR assays for a large number of organisms, this method could also prove to be very useful in simplifying the existing protocols for other applications where pre-PCR restriction digestion is required, such as mutation detection, genotyping, and selective template amplification.

Evaluation of a novel chemiluminescent microplate enzyme immunoassay for hepatitis B surface antigen detection

Hepatitis B virus surface antigen (HBsAg) is an important biomarker used in the diagnosis of hepatitis B virus (HBV) infection, but false-negative results are still reported in the detection of HBsAg using commercial assays. In this study, we evaluated the qualitative properties of a novel HBsAg chemiluminescence enzyme immunoassay (CLEIA) assay--WTultra. WHO standard sample dilution series and samples from low-level HBsAg carriers (<1 ng/mL) were used to evaluate the sensitivity of the WTultra assay. Boston Biomedica, Inc. (BBI) hepatitis B seroconversion panels were used to assess the ability of the WTultra assay to detect the window period. In addition, dilution series of 22 serum samples with different genotypes, serotypes and HBsAg mutations were used to assess the WTultra assay, and these were compared with other commercial assays. The lower detection limit of the WTultra assay was 0.012 IU/mL, and it showed a high sensitivity (97.52%, 95% CI, 94.95-99.00) in the detection of 282 low-level HBsAg carriers (<1 ng/mL). In samples with various HBV genotypes, serotypes and HBsAg mutations, the WTultra assay yielded 117 positive results in 132 samples, which was significantly higher than the results with the other four commercial assays (89, 83, 65 and 45, respectively, p<0.01). In the assays of mutant strains, the WTultra assay detected 82 positive results in 90 samples, which was significantly better than the results for the Hepanostika HBsAg Ultra (58 positive) and Architect (55 positive) (p<0.01) assays, which in turn were significantly better than the Murex V.3 (41 positive, p=0.026) and AxSYM V2 (29 positive, p<0.01) assays. However, in the detection of 42 samples of wild-type strains with various genotypes and serotypes, no significant differences were observed among the WTultra (35 positive), Architect (28 positive) and Hepanostika HBsAg Ultra (31 positive) assays. However, the WTultra assay detected significantly more samples than the Murex V.3 (24 positive, p<0.01) and AxSYM V2 (16 positive, p<0.01) assays. In conclusion, the WTultra HBsAg assay has a high detection sensitivity and presents excellent results for the detection of mutants.

Update on hepatitis B and C virus diagnosis

Viral hepatitis B and C virus (HBV and HCV) are responsible for the most of chronic liver disease worldwide and are transmitted by parenteral route, sexual and vertical transmission. One important measure to reduce the burden of these infections is the diagnosis of acute and chronic cases of HBV and HCV. In order to provide an effective diagnosis and monitoring of antiviral treatment, it is important to choose sensitive, rapid, inexpensive, and robust analytical methods. Primary diagnosis of HBV and HCV infection is made by using serological tests for detecting antigens and antibodies against these viruses. In order to confirm primary diagnosis, to quantify viral load, to determine genotypes and resistance mutants for antiviral treatment, qualitative and quantitative molecular tests are used. In this manuscript, we review the current serological and molecular methods for the diagnosis of hepatitis B and C.

Recent advances in molecular diagnostics of hepatitis B virus

Hepatitis B virus (HBV) is one of the important global health problems today. Infection with HBV can lead to a variety of clinical manifestations including severe hepatic complications like liver cirrhosis and hepatocellular carcinoma. Presently, routine HBV screening and diagnosis is primarily based on the immuno-detection of HBV surface antigen (HBsAg). However, identification of HBV DNA positive cases, who do not have detectable HBsAg has greatly encouraged the use of nucleic acid amplification based assays, that are highly sensitive, specific and are to some extent tolerant to sequence variation. In the last few years, the field of HBV molecular diagnostics has evolved rapidly with advancements in the molecular biology tools, such as polymerase chain reaction (PCR) and real-time PCR. Recently, apart of PCR based amplification methods, a number of isothermal amplification assays, such as loop mediated isothermal amplification, transcription mediated amplification, ligase chain reaction, and rolling circle amplification have been utilized for HBV diagnosis. These assays also offer options for real time detection and integration into biosensing devices. In this manuscript, we review the molecular technologies that are presently available for HBV diagnostics, with special emphasis on isothermal amplification based technologies. We have also included the recent trends in the development of biosensors and use of next generation sequencing technologies for HBV.

Quantification of hepatitis B surface antigen and E antigen: correlation between Elecsys and architect assays

Quantification of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) and their change model during treatment are emerging as a useful tool for assessing the outcome of hepatitis B virus (HBV) infection and predicting the efficacy of antiviral therapy. The aim of this study was to compare the performance of the Elecsys and Architect assays for HBsAg and HBeAg quantification. Quantification of HBsAg and HBeAg, determined by these two assays, were assessed in 1292 sera from patients with chronic hepatitis B(CHB). HBeAg quantification in serum was performed by calibrating the results through HBeAg Paul-Ehrlich international (PEI) reference standard. The HBV genotype was determined by direct sequencing and phylogenetic analysis. Of 1292 samples, the distribution of genotype was 514 (39.78%) genotype B, 776 (60.06%) genotype C, 2 (0.16%) genotype D. The results of HBsAg and HBeAg quantification between the Architect and Elecsys assays were significantly correlated (HBsAg: r = 0.939; HBeAg: r = 0.987), independent of HBV genotype and treatment phase. The mean differences between the two methods (the log10 [Elecsys] - the log10 [Architect]) were 0.075 log10  IU/mL and -0.149 log10 PE IU/mL in quantifying HBsAg and HBeAg, respectively. This study demonstrates a high correlation between the Elecsys and the Architect assays in quantifying HBsAg and HBeAg, regardless of HBV genotype. Both the two assays can be used to monitor the HBsAg and HBeAg levels in patients with chronic hepatitis B.

Hybrid nanocluster plasmonic resonator for immunological detection of hepatitis B virus

Approximately 88% of the world population lives in regions with intermediate to high incidence of Hepatitis B virus (HBV), yet current serological and DNA-based detection methods have limited sensitivity and convenience. Here, we describe a preassembled plasmonic resonance nanocluster for HBV detection. The gold nanoparticle acceptors (AuNPs), with HBV surface antigen (HBsAg) epitope, and quantum dot (QD) donors with Fab antibody, are assembled into an immuno-mediated 3D-oriented complex with enhanced energy transfer and fluorescence quenching. The coherent plasmonic resonance between Au and QD nanoparticles is exploited to achieve improved donor-acceptor resonance within the nanocluster, which in the presence of HBV viral particles is disassembled in a highly specific manner. The nanocluster provides high detection specificity and sensitivity of HBV, with a sensitivity limit down to 1-100 viral particles per microliter and to attomolar levels of HBsAg. This general platform could be used to establish multiplex diagnostic assays for a variety of other microbial pathogens.

Assessment of dried blood spot samples as a simple method for detection of hepatitis B virus markers

Detection of hepatitis B virus (HBV) serological markers in dried blood spot (DBS) samples by enzyme immunoassay (ELISA) has not yet been fully optimized. In this study, the ability to detect three HBV markers (HBsAg, anti-HBc, and anti-HBs) was evaluated in DBS samples using a modified commercial ELISA. Matched serum and DBS samples were obtained from individuals with or without a past history of HBV infection. Sera samples were tested according to the manufacturer's instructions, but for DBS testing, paper diameters, elution buffer, volume of input sample, and cut-off values were evaluated to optimize the assay. Stability studies were done on DBS stored at for up to 180 days at different temperatures. The absorbance values that yielded the maximum sensitivity and specificity were determined based on the area under the ROC curve (AUROC) and chosen as the cut-off value. Using this parameter, sensitivity was 90.5%, 97.6%, and 78% for anti-HBc, HBsAg, anti-HBs assays, respectively. Specificity was 92.6%, 96.7%, and 97.3% for anti-HBc, HBsAg, and anti-HBs assays, respectively. HBV markers could be detected in DBS samples until 63 days after sample collection at most temperatures, but storage at -20°C yielded more consistent results. These results indicate that modified ELISA can be used to detect HBV markers in DBS samples, particularly if the samples are stored appropriately.

An improved Abbott ARCHITECT assay for the detection of hepatitis B virus surface antigen (HBsAg)

BACKGROUND

The sensitive and accurate detection of hepatitis B virus surface antigen (HBsAg) is critical to the identification of infection and the prevention of transfusion transmitted disease. Improvement in HBsAg assay sensitivity is essential to reduce the window to detect an acute HBV infection. Additionally, the sensitive detection of HBsAg mutants that continue to evolve due to vaccine escape, immune selection and an error prone reverse transcriptase is a necessity.

OBJECTIVES AND STUDY DESIGN

A fully automated HBsAg prototype assay on the Abbott ARCHITECT instrument was developed to improve sensitivity and mutant detection. This magnetic microparticle-based assay utilizes anti-HBsAg monoclonal antibodies to capture antigen present in serum or plasma. Captured antigen is then detected using anti-HBsAg antibody conjugated with the chemiluminescent compound, acridinium.

RESULTS

The sensitivity of the ARCHITECT HBsAg prototype assay was improved as compared to the current ARCHITECT, PRISM, and competitor HBsAg assays. The enhancement in assay sensitivity was demonstrated by the use of commercially available HBV seroconversion panels. The prototype assay detected more panel members (185 of 383) vs. the current ARCHITECT (171), PRISM (181), or competitor HBsAg assays (73/140 vs. 62/140, respectively). The ARCHITECT prototype assay also efficiently detected all mutants evaluated. Finally, the sensitivity improvement did not compromise the specificity of the assay (99.94%).

CONCLUSIONS

An improved Abbott ARCHITECT HBsAg prototype assay with enhanced detection of HBsAg and HBsAg mutants, as well as equivalent specificity was developed for the detection, diagnosis, and management of HBV infection.

Comparison of the technical and clinical performance of the Elecsys HBsAg II assay with the Architect, AxSym, and Advia Centaur HBsAg screening assays

South East Asia has some of the highest prevalence rates of hepatitis B virus (HBV) infection (>or=8%) in the world, and the emergence of hepatitis B surface antigen (HBsAg) mutant strains is a growing problem. Assays with the highest levels of sensitivity, including mutant detection, should be used for routine HBsAg screening. In this large multicenter study, the clinical and technical performance of the fully automated Elecsys HBsAg II assay was compared with the Architect, AxSYM, and Advia Centaur HBsAg assays for HBsAg screening. Nine laboratories (three each from Thailand, Korea, and Singapore) compared the Elecsys HBsAg II assay with their routine HBsAg screening assay against a range of stored and routine clinical samples, including recombinant mutants. The Elecsys HBsAg II assay demonstrated equivalent sensitivity and specificity to the Architect HBsAg assay. However, the Elecsys HBsAg II assay recognized a native mutant sample (L94S, L97V, L98V, T123A) that the Architect HBsAg assay failed to detect. The AxSYM and Advia Centaur HBsAg assays appeared less sensitive for the detection of early HBV infection and also failed to detect some of the recombinant mutant strains. There was almost complete agreement between the Elecsys HBsAg II assay and comparator assays with respect to routine serum samples. The results of this study demonstrate that the Elecsys HBsAg II assay is a highly sensitive and specific screening assay for HBsAg and detects reliably the most important and clinically relevant HBV mutants and genotypes. It is suitable for routine HBsAg screening in Asia.

A novel immunoassay for PreS1 and/or core-related antigens for detection of HBsAg variants

A novel immunoassay that detects simultaneously hepatitis B virus (HBV) PreS1 and/or core-related antigens was developed and evaluated for its potential for detecting hepatitis B surface antigen (HBsAg) variants. The detection limits of the assay was 10(2.9+/-0.5)copies/mL (mean+/-SD) for HBsAg-positive sera with different genotypes, and 10(3.5+/-1.2)copies/mL for HBsAg variants sera. The specificity of the assay was 99.9% (95% CI: 99.7-99.9%, 4551 healthy individuals). The sensitivities were 93.9% (95% CI: 92.8-94.9%), 59.3% (95% CI: 38.7-77.6%) and 80% (95% CI: 44.4-97.5%) in three independent groups which include: 2065 hepatitis patients, 27 patients with occult hepatitis B and 10 HBsAg variants, respectively. In addition, a novel premature stop code mutation at position 112 of HBsAg was observed in two patients with chronic hepatitis B with different genotypes.

Detection of a premature stop codon in the surface gene of hepatitis B virus from an HBsAg and antiHBc negative blood donor

BACKGROUND

In blood donors, HBV infection is detected by the presence of serum hepatitis B surface antigen (HBsAg). However, some mutations in the surface gene region may result in altered or truncated HBsAg that can escape from immunoassay-based diagnosis. Such diagnostic escape mutants pose a potential risk for blood transfusion services.

RESULTS

In the present study, we report a blood donor seronegative for HBsAg and antiHBc, but positive for antiHBs who was HBV DNA positive by PCR. Sequencing of the HBsAg gene revealed presence of a point mutation (T-A) at 207th nucleotide of the HBsAg ORF, which resulted in a premature stop codon at position 69. This results in a truncated HBsAg gene lacking the entire 'a' determinant region. However, follow-up of the donor after 2 years revealed clearance of HBV DNA from the serum.

CONCLUSION

The case illustrates an unusual mutation, which causes HBsAg negativity. The finding emphasizes the importance of molecular assays in reducing the possibility of HBV transmission through blood transfusion. However, developing more sensitive serological assays, capable of detecting HBV mutants, is an alternative to expensive and complex amplification-based assays for developing countries.

Central African Republic is part of the West-African hepatitis B virus genotype E crescent

BACKGROUND

Recent studies have shown that Hepatitis B virus (HBV) genotype E predominates in a vast crescent in West-Africa spanning from Senegal to Angola.

OBJECTIVES

To determine whether HBV strains in the Central African Republic (CAR) belong predominately to the homogeneous West-African genotype E or whether they are more closely related to genotypes found in East Africa.

STUDY DESIGN

Serum samples were randomly collected from 196 patients admitted with symptoms of acute or chronic hepatitis to the Central Hospital in Bangui. Thirty complete and 36 partial sequences of HBV strains were obtained.

RESULTS

Ninety-four percent (62/66) of the strains belonged to genotype E, while genotype A1, most closely related to a strain from Tanzania and genotype D were detected in only one and three samples, respectively. One strain presented a recombination between the S and X gene of a genotype E precursor and a partial PreC/C gene of a genotype D precursor.

CONCLUSIONS

Genotype E is predominant in CAR with little overlap with genotypes from Eastern Africa, extending the West-African HBV genotype E crescent further to the East.

Hepatitis B virus genotype E surface antigen detection with different immunoassays and diagnostic impact of mutations in the preS/S gene

The major neutralizing epitope, the "a" determinant of the hepatitis B virus (HBV) genotype E surface antigen (HBsAg) is most divergent from that of genotype A, which is used for preparing monoclonal antibodies used in commercially available HBV reagents. To evaluate the performance of the latest generation of HBsAg detection assays with respect to genotype E HBsAg. Three commercial assays were evaluated using sera from 200 Nigerian patients compared to the preS/S sequence of DNA positive samples. Out of 200 samples, 61 and 103 gave concordant positive and negative results between the three HBsAg assays. Of 36 samples with discordant results, 35 were confirmed negative by neutralisation. One of the three assays showed significantly high rate of false positives (29 of 35). DNA positive samples with no detectable HBsAg or reduced HBsAg detection signals (<75% of mean signal obtained with HBsAg positive samples) revealed several mutations (V14A, F46S, N48T, L49R, I49T, D51G, A53V, P54L, Q82P, F83C, L127P, A184V, T189I, S204N, V224A), mostly outside the a-determinant. Several of these mutations are found as wild type nucleotides normally in genotype A and only exceptionally in genotype E. All three assays showed comparable sensitivities for genotype E HBsAg detection (98.4-100%) but differed considerably in specificity (84-99%). Failure to detect HBsAg antigen and differences in signal intensity were mainly associated with mutations in the preS/S gene outside the "a" determinant.

Evaluation of a new automated assay for hepatitis B surface antigen (HBsAg) detection VIDAS HBsAg Ultra

In a multicenter study a new automated screening assay, VIDAS HBsAg Ultra (long (L) and short (S) incubation protocol (Biomérieux, Marcy l'Etoile, France), was compared to a well established test (AxSYM HBsAg v2, Abbott Diagnostics, Wiesbaden, Germany) for the detection of hepatitis B virus (HBV) surface antigen (HBsAg). A total of 32 seroconversion panels, sera from the chronic phase of infection, dilution series of the WHO standard, S gene mutants (recombinant mutants and diluted and undiluted sera harbouring mutants with single or multiple amino acid (aa) substitutions, n = 40) and isolated anti-HBc positive samples were tested for the evaluation of sensitivity. Sera from HBsAg negative blood donors, pregnant women, hospitalized patients and potentially cross-reactive samples were investigated to determine the specificity of the new assay. The VIDAS HBsAg Ultra (L+S) had a higher sensitivity than the alternative assay for the detection of acute hepatitis B in seroconversion panels. The mean time of the diagnostic window was shortened with the VIDAS HBsAg Ultra (L) and (S) in comparison with the AxSYM HBsAg v2 by 1.06 and 0.66 days, respectively. The VIDAS HBsAg Ultra (L) did not detect one diluted sample out of six bearing the single aa G145R substitution, and two out of 12 diluted samples harbouring multiple aa substitutions. The analytical sensitivity of the assays varied from one surface mutant to another. While no false positive results were obtained with the VIDAS HBsAg Ultra (L+S) among potentially interfering samples, four false positives were detected with the AxSYM HBsAg v2. The respective values for sensitivity for the VIDAS HBsAg Ultra (L), (S) and the AxSYM HBsAg v2 were 99.07%, 97.87% and 94.14%. The specificities were 100% (VIDAS HBsAg Ultra L and S) and 99.6% (AxSYM HBsAg v2). In conclusion, the VIDAS HBsAg Ultra is highly sensitive and specific and represents an improvement for the detection of HBsAg in routine diagnostic laboratories.

Relative colonizing abilities of human fecal and K 12 strains of Escherichia coli in the large intestines of streptomycin-treated mice

Male CD-1 mice, fed streptomycin in their drinking water, were used to study colonization of the mouse intestine by both fecal Escherichia coli strains isolated from healthy humans and Escherichia coli K12 strains which are routinely used as hosts for recombinant DNA. Prior to use in mice, all the strains were made resistant to streptomycin. Several facts emerged from these studies: (a) Strains isolated from different healthy humans colonized the mouse intestine with equal ability (approximately 10(8) cells/g feces), but may have colonized biochemically distinct sites. (b) K12 strains tested had, at most, one hundredth the colonizing ability of human fecal strains. (c) Rifampicin-resistant mutants of strains which contain one or no plasmids were poor colonizers relative to their parents. (d) Rifampicin-resistant mutants of strains which contain six or more plasmids retained the colonizing abilities of their parents. (e) Introduction of the F-amp or pJBK5 plasmid into HS-4, a human fecal strain which does not normally carry these plasmids, reduced its colonizing ability 1000-fold. (f) Strains used in this study colonized the mouse caecum and colon exclusively. The system presented here offers a simple, rapid test to determine whether a specific genetic alteration in a bacterium (e.g. antibiotic resistance) results in enhanced, reduced, or unchanged colonizing ability. Such a test might prove to be of value as a part of the clinical testing of antibiotics.