Characterization of occult hepatitis B virus infection from blood donors in China. J Clin Microbiol. 2011;49:1730-1737. [PMID: 21411575 DOI: 10.1128/jcm.00145-11]

Prevalence and molecular characteristics of occult hepatitis B virus infection among blood donors in Huzhou City, eastern China

Occult hepatitis B virus (HBV) infection (OBI) is a significant challenge for HBV prevention and control. We investigated the prevalence and surface (S) gene mutations of OBI among blood donors in Huzhou City, eastern China. The hepatitis B surface antigen (HBsAg) was routinely screened among 44,256 blood donors. HBV-DNA was detected using the Roche cobas®system. Serum samples that were HBsAg negative and HBV-DNA positive were selected, and the HBV S gene was amplified and sequenced. HBV genotype and S gene mutations were analyzed. The OBI rate in these blood donors was 0.070 % (31/44,256). Among the blood donors with OBI, only two cases (2/31, 6.5 %) were anti-HBc negative. The S gene sequences of 28 samples were successfully obtained, and we found that HBV genotype C (21/28, 70 %) was predominant among blood donors with OBI. Most S gene mutations were associated with OBI, and the high frequency mutations included N40S, G44E, Q51R/P, T113A/S,T118K/M, P120Q/S/T, and Y161F/S. Notably, amino acid substitutions at some sites differed from those reported previously, such as Y72F, G102V, P127L, Q129P, and S143T. Additionally, six novel mutations (S31I/N/R, P46L, S58C, C76Y, Y200F/C, and I208T) that may be associated with OBI were found. OBI was detected in a certain proportion of blood donors in Huzhou City. S gene mutations play an important role in OBI development. Further research is required to explore the functions of novel S gene mutants in OBI pathogenesis. The findings of this study may provide important insights to prevent HBV transmission through blood transfusions.

The prevalence of occult hepatitis B infection among the blood donors in a donation center in Beijing

Occult HBV infection (OBI) remains a potential threat for blood safety. The prevalence of OBI was investigated in a blood donation center of Chinese PLA General Hospital to improve HBV blood safety. 229446 samples from blood donors were screened by two different enzyme-linked immunosorbent assay (ELISA) kits. 78 samples were HBV DNA positive among 212134 ELISA nonreactive donor samples. The prevalence of OBI was 0.04% (76/212134). Ten samples of OBI were permitted by the donors' content for further research, and all of these were below 200IU/mL, and six of these were below 20IU/mL(6/10,60%). Genotype B and genotype C was 20% (2/10) and 80% (8/10), respectively. 16 amino acid mutations were detected in the S region of OBI, included three mutations in MHR region of S. The prevalence of OBI is rare in this donation center. These mutations we found may contribute to the multifactorial occurrence of OBI.

Genetic diversity and occult hepatitis B infection in Africa: A comprehensive review

BACKGROUND

Occult hepatitis B infection (OBI) is a globally prevalent infection, with its frequency being influenced by the prevalence of hepatitis B virus (HBV) infection in a particular geographic region, including Africa. OBI can be transmitted through blood transfusions and organ transplants and has been linked to the development of hepatocellular carcinoma (HCC). The associated HBV genotype influences the infection.

AIM

To highlight the genetic diversity and prevalence of OBI in Africa.

METHODS

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and involved a comprehensive search on PubMed, Google Scholar, Science Direct, and African Journals Online for published studies on the prevalence and genetic diversity of OBI in Africa.

RESULTS

The synthesis included 83 articles, revealing that the prevalence of OBI varied between countries and population groups, with the highest prevalence being 90.9% in patients with hepatitis C virus infection and 38% in blood donors, indicating an increased risk of HBV transmission through blood transfusions. Cases of OBI reactivation have been reported following chemotherapy. Genotype D is the predominant, followed by genotypes A and E.

CONCLUSION

This review highlights the prevalence of OBI in Africa, which varies across countries and population groups. The study also demonstrates that genotype D is the most prevalent.

Effect of S-region mutations on HBsAg in HBsAg-negative HBV-infected patients

BACKGROUND

Occult HBV infection (OBI) is a special form of hepatitis B virus (HBV) infection that may cause Liver cirrhosis and hepatocellular carcinoma, causing significant harm to patients. Given the insidious nature of OBI, it is usually not easy to be detected. Most of the samples currently studied are concentrated on blood donors, however, patients in this special state have not been fully studied. This project aimed to study the effect of HBV S region mutations on HBsAg in patients with clinical OBI.

METHODS

Collect 107 HBsAg-/HBV DNA + blood samples from Beijing Youan Hospital, Capital Medical University from August 2022 to April 2023. Next, the successfully extracted and amplified HBV DNA S regions were sequenced. Construct mutant plasmids to verify the cell function of the high-frequency mutation sites and explore the possible molecular mechanism.

RESULTS

Sixty-eight HBsAg-negative samples were sequenced, revealing high-frequency amino acid substitution sites in the HBV S protein, including immune escape mutations (i.e., sY100C、sK122R、sI126T、sT131P、and sS114T) and TMD (Transmembrane domain) region substitutions (i.e., sT5A、sG10D、sF20S、and sS3N). We constructed a portion of the mutant plasmids and found that sT5A, sF20S, sG10D, sS3N, sI68T, and sI126T single point mutations or combined mutations may decrease HBsAg expression or change the antigenicity of HBsAg leading to detection failure.

CONCLUSIONS

HBsAg-negative patients may show various mutations and amino acid replacement sites at high frequency in the HBV S-region, and these mutations may lead to undetectable Hepatitis B surface antigen (HBsAg), HBsAg antigenic changes or secretion inhibition.

Occult Hepatitis B Virus Infection and Liver Fibrosis in Chinese Patients

BACKGROUND

The impact of hepatitis B surface antigen (HBsAg)-negative/hepatitis B virus (HBV) DNA-positive occult HBV infection (OBI) on the severity of liver fibrosis remains unclear.

METHODS

A total of 1772 patients negative for HBsAg but positive for antibody to hepatitis B core antigen (HBcAg), stratified by the presence or absence of OBI, were selected for long-term carriage leading to elevation of ≥2 of 4 liver fibrosis indexes-hyaluronic acid (HA), laminin, type III procollagen peptide (PCIII), and type IV collagen (CIV)-at testing in a Chinese hospital. Patients were tested for serum viral load, HBV markers, and histopathological changes in liver biopsy specimens.

RESULTS

OBI was identified in 148 patients with liver fibrosis (8.4%), who had significantly higher levels of HA, laminin, PCIII, and CIV than 1624 fibrotic patients without OBI (P < .05). In 36 patients with OBI who underwent liver biopsy, significant correlations were observed between OBI viral load and serum HA levels (P = .01), PCIII levels (P = .01), and pathological histological activity index (HAI) scores (P < .001), respectively; HAI scores and PCIII levels (P = .04); HBcAg immunohistochemical scores and HA levels (P < .001); and HBcAg immunohistochemical scores and PCIII levels (P = .03). Positive fluorescent in situ hybridization results were significantly more frequent in patients with OBIs (80.6% vs 37.5% in those without OBIs). Among patients with OBIs, HBcAg was detected in the liver tissue in 52.8% and HBsAg in 5.6%.

CONCLUSIONS

OBI status appears to be associated with liver fibrosis severity.

Haplotype-dependent HLA-DRB1-DQB1 susceptibility to occult HBV infection in Xi'an Han population

BACKGROUND

Occult hepatitis B virus (HBV) infection (OBI) is primarily characterized by the persistence of HBV-DNA in the liver tissues and/or in the serum without detectable HBsAg. Human leukocyte antigen (HLA) polymorphisms have been found to be strongly associated with HBV in different ethnic backgrounds. The association of HLA-DRB1-DQB1 haplotypes with OBI has not been previously reported in China. The aim of this study was to identify the potential association of HLA-DRB1-DQB1 haplotypes that may be involved in OBI genetic susceptibility.

METHODS

A case-control study was conducted between 107 OBI subjects and 280 healthy controls from the blood donors in the Shaanxi Province Blood Center. The HLA-DRB1, DQB1 loci were genotyped using polymerase chain reaction-sequence based typing (PCR-SBT). Based on the genotype data of the two loci, haplotype estimation was performed.

RESULTS

HLA-DRB1*07:01-DQB1*02:02 (pc = 0.344 × 10^-3 , OR = 3.489, 95%CI = 2.000-6.088) and HLA-DRB1*09:01-DQB1*03:03 (pc = 0.02, OR = 2.370, 95%CI = 1.450-3.873) serve as the possible risk and susceptibility haplotypes for OBI in Xi'an Han after Bonferroni correction.

CONCLUSIONS

This study demonstrated that HLA II haplotypes were significantly associated with OBI in the Xi'an Han population. To the best of our knowledge, this is the first study to associate HLA-DRB1-DQB1 haplotypes with OBI, which can provide valuable insights into the relationship between the various genetic factors and immune responses in the Xi'an population. The findings can also form the basis for future studies about the role of HLA in OBI.

Low Risk of Occult Hepatitis B Infection among Vietnamese Blood Donors

Occult hepatitis B infection (OBI) is characterized by the presence of low levels of hepatitis B virus (HBV) DNA and undetectable HBsAg in the blood. The prevalence of OBI in blood donors in Asia ranges from 0.013% (China) to 10.9% (Laos), with no data available from Vietnam so far. We aimed to investigate the prevalence of OBI among Vietnamese blood donors. A total of 623 (114 women and 509 men) HBsAg-negative blood donors were screened for anti-HBc and anti-HBs by ELISA assays. In addition, DNA from sera was isolated and nested PCR was performed for the HBV surface gene (S); a fragment of the S gene was then sequenced in positive samples. The results revealed that 39% (n = 242) of blood donors were positive for anti-HBc, and 70% (n = 434) were positive for anti-HBs, with 36% (n = 223) being positive for both anti-HBc and anti-HBs. In addition, 3% of blood donors (n = 19) were positive for anti-HBc only, and 34% (n = 211) had only anti-HBs as serological marker. A total of 27% (n = 170) were seronegative for any marker. Two of the blood donors (0.3%) were OBI-positive and sequencing revealed that HBV sequences belonged to HBV genotype B, which is the predominant genotype in Vietnam.

Estimates of the prevalence of occult HBV infection in Asia: a systematic review and meta-analysis

PURPOSE

Occult Hepatitis B virus infection (OBI) is of great significance to the transmission of Hepatitis B virus (HBV) and the evolution of the patient's clinical outcome. We conducted a systematic review and meta-analysis to estimate the prevalence of OBI in Asia.

METHODS

Literature search was conducted in PubMed, Cochrane Library database, Web of Science and Embase with the keywords of 'Hepatitis B virus', 'occult infection', 'prevalence'. 70 studies were included in the meta-analysis. Meta-analysis was performed using random-effects models to calculate the pooled prevalence of OBI and 95% confidence interval (CI). The data were analyzed in R 4.1.2.

RESULTS

The overall prevalence of OBI was 4% (95%CI: 0.03-0.06) in Asia. Subgroup analysis based on geographic region showed a prevalence of 3% (95%CI 0.02-0.06) in East Asia, 9% (95%CI 0.05-0.15) in West Asia, 3% (95%CI 0.01-0.11) in Southern Asia and 9% (95%CI 0.05-0.15) in Southeast Asia. Subgroup analysis demonstrated a prevalence of 1% (95%CI 0.00-0.02) in general population, 5% (95%CI: 0.03-0.08) in high-risk population, 9% (95%CI: 0.03-0.22) in the human immunodeficiency virus (HIV)-infected patient, 18% (95%CI: 0.09-0.32) in the hepatopathy patients.

CONCLUSION

Based on the meta-analysis of the prevalence of OBI in different populations, we concluded that the prevalence of OBI in the high-risk population, hepatopathy patients, and HIV-infected patients was higher than that in the general population. A systematic review showed that OBI was associated with disease progression and prognosis. Therefore, these populations should be routinely screened for OBI and promptly intervened to avoid promoting disease progression.

The Investigation of HBV Pre-S/S Gene Mutations in Occult HBV Infected Blood Donors with anti-HBs Positive

Introduction

The coexistence of hepatitis B virus (HBV) and hepatitis B surface antibodies (anti-HBs) in occult hepatitis B virus infection (OBI) is a contradictory phenomenon, and the underlying mechanism is not fully understood. The characteristics of pre-S/S mutations in OBI genotypes B and C (OBI_B and OBI_C) in the presence or absence of anti-HBs were analyzed extensively in this study. Methodology. The amino acid substitutions of envelope proteins of 21 OBI strains, including 4 HBs (+) OBI_B, 6 HBs (−) OBI_B, 6 HBs (+) OBIc, and 5 HBs (−) OBI_C samples, were analyzed and fully compared among groups of HBV genotypes and the presence of anti-HBs.

Results

The mutation rates in pre-S1, pre-S2, and S proteins of OBI_C were significantly higher than wild-type HBV (wt-HBV) genotype C strains, but only the mutation rate of S protein in OBI_B was significantly higher compared to wild-type HBV genotype B. The mutation rates in S protein of anti-HBs (−) OBI were higher than anti-HBs(+) OBI samples (4.40% vs. 2.43% in genotype B, P > 0.05; 6.81% vs. 3.47% in genotype C, P < 0.05). For these high-frequency substitutions in the pre-S/S region, the mutations sN40S and sK122R were found in 27.3% and 45.5% of anti-HBs (−) OBI strains, respectively. 7 substitutions were uniquely found in OBI_C strains and 9 substitutions were commonly detected in OBI_B and OBI_C strains.

Conclusions

These results suggested that the mutations might occur randomly and were not selected by antibody pressure.

Occult Hepatitis B Virus Infection: An Update

Occult hepatitis B virus (HBV) infection (OBI) refers to a condition in which replication-competent viral DNA is present in the liver (with detectable or undetectable HBV DNA in the serum) of individuals testing negative for the HBV surface antigen (HBsAg). In this peculiar phase of HBV infection, the covalently closed circular DNA (cccDNA) is in a low state of replication. Many advances have been made in clarifying the mechanisms involved in such a suppression of viral activity, which seems to be mainly related to the host's immune control and epigenetic factors. OBI is diffused worldwide, but its prevalence is highly variable among patient populations. This depends on different geographic areas, risk factors for parenteral infections, and assays used for HBsAg and HBV DNA detection. OBI has an impact in several clinical contexts: (a) it can be transmitted, causing a classic form of hepatitis B, through blood transfusion or liver transplantation; (b) it may reactivate in the case of immunosuppression, leading to the possible development of even fulminant hepatitis; (c) it may accelerate the progression of chronic liver disease due to different causes toward cirrhosis; (d) it maintains the pro-oncogenic properties of the "overt" infection, favoring the development of hepatocellular carcinoma.

Occult Hepatitis B Infection among Hemodialysis in Tabriz, Northwest of Iran: Prevalence and Mutations within the S Region

Regardless of the extensive screening for the detection of hepatitis B surface antigen (HBsAg), hemodialysis (HD) patients are still severely at the risk of occult hepatitis B virus infection (OBI), especially in developing countries. OBI is defined as the presence of HBV DNA with undetectable HBsAg in the liver and/or Serum. This study aims to determine the prevalence of OBI in HD patients in Tabriz Province, northwest of Iran, and inquire about the mutations in the detected HBsAg. In this cross-sectional descriptive study, ELISA method assessed serum and plasma samples of 118 HBsAg-negative patients undergoing HD treatment for HBV serological markers (HBsAg and Anti-HBc). Specific primers by nested polymerase chain reaction have been utilized to examine HBV DNA; also, direct sequencing of surface genes was carried out to characterize the viral genotypes and S gene mutations. Finally, followed by real-time PCR, the quantity of viral load in OBI-positive patients was determined. A total of 118 HD patients were included (63.6% were male and 36.4% female), with an overall mean age of 60.8 ± 12.8 years old. The prevalence of antihepatitis B core antibody (Anti-HBc) in the study population was 26.3% (31/118). Five patients (4.2%) were positive for HBV DNA and labeled OBI-positive; their plasma HBV-DNA load was less than 100 IU/ml. Following the phylogenetic analysis, the samples with OBI roughly belonged to genotype D, subtype ayw2 and only two had mutations within the S ’gene’s major hydrophilic region (MHR), including T123I, C124F, and P127T. This study reports the prevalence of OBI in the HBsAg-negative HD patients being at a rate of 4.2%, which can be a clinically vital consideration in this region. HBV serologic screening approaches need to be renewed to cover nucleic acid testing in the setting of hemodialysis and all the other high-risk groups associated with it (i.e., blood and organ donors).

Molecular characteristics of the full-length genome of occult hepatitis B virus from blood donors in China

The characteristics of a large sample size of the full-length genome of occult hepatitis B virus (HBV) infection (OBI) have not been extensively explored in China. Voluntary blood donors who were HBsAg-negative/HBV NAT-positive (HBsAg−/HBV NAT+) were identified by blood screening and recruited. Blood samples were tested for HBV serologic markers, viral loads, and PCR to identify OBI. HBV full-length genomes were obtained by amplifying two fragments using nested PCR. The characterization of OBI strains was based on sequence analyses compared with HBsAg+ strains obtained from the same donor population. Of the 50 full-length genomes of 172 identified OBI strains, 33 were classified as genotype B (OBI_B) and 17 strains as genotype C (OBI_C). Significantly higher nucleotide variabilities were observed in the Pre-S2/S promoter region (SP2) and core upstream regulatory sequence (CURS) in OBI_B than in their HBsAg+ controls (P < 0.05). Both OBI_B and OBI_C showed higher amino acid (aa) variabilities in Pol and Pre-S/S regions than their controls (P < 0.05). In addition, 19 novel OBI-related mutations were found spanning the four open reading frames (ORFs) of the HBV genome. Four novel deletions and one novel insertion were also found in OBI_C strains. Several novel OBI-related mutations spanning the four ORFs of the virus were identified by characterizing a large sample size of the full-length OBI genome, which may affect the production of HBsAg and contribute to the occult infection of HBV.

High-Frequency Notable HBV Mutations Identified in Blood Donors With Occult Hepatitis B Infection From Heyuan City of Southern China

Background

All Chinese blood centers have implemented mini pool (MP) HBV nucleic acid testing (NAT) together with HBsAg ELISA in routine donor screening since 2015. The prevalence of occult hepatitis B virus infection (OBI) in donors from different regions varies, and the molecular characterization of the HBV DNA and clinical outcomes of these OBIs remain largely unexplored.

Methods

Blood donations from Heyuan city in Southern China were screened by HBsAg ELISA and HBV MP8 NAT. Donations with HBsAg-/HBV DNA+ were collected for this study. Molecular characterizations of HBV DNAs were further analyzed by various DNA amplification assays including quantitative PCR (qPCR) and nested PCR, amplifying the basic core and pre-core promoter regions (BCP/PC). The HBsAg (S) region from HBV DNA was isolated by high-volume nucleic acid extraction. Notable mutations were identified by comparison to the HBV reference sequences. The clinical outcomes of the donors with OBIs were further followed for nearly 3 years.

Results

Seventy OBIs from 44,592 donations (0.15%) that we identified and reported previously were enrolled for this current study. HBV sequences were obtained from 44/70 OBIs, and genotyping analysis showed that 42/44 (95.2%) OBIs were genotype B, and 2/44 (4.8%) were genotype C. Interestingly, mutation analysis revealed that various mutations including M133L/T, F134L, P142L, V168A, R169H, S174N, L175S, and V177A of HBV DNA affecting HBsAg detection were observed in genotype B OBIs. Two notable mutations, T47K and L53S, were identified in genotype C OBIs. Follow-up studies showed that 3/31 (9.7%) OBIs converted to HBsAg+ as chronic infections while 1/31 (3.2%) HBV DNA was undetectable (classified as recovery) and 27/31 (87.1%) remained as OBIs.

Conclusion

Various notable mutations affecting HBsAg detection were observed in blood donors with OBIs in Heyuan city of Southern China. Follow-up studies showed that most OBIs remained as OBIs with fluctuating or low viral loads. Higher sensitive HBV ID NAT is recommended for donor screening to further reduce the transmission risk of OBIs.

High resolution HLA-DRB1 analysis and shared molecular amino acid signature of DRβ1 molecules in Occult hepatitis B infection

AIM

To investigate the association of human leukocyte antigen (HLA)-DRB1 alleles and the variations of polymorphic amino acid changes in DRβ1 chain in Shaanxi Han population with Occult hepatitis B infection (OBI).

METHODS

High-resolution HLA-DRB1 genotyping was performed in 107 OBI carriers and 280 normal controls. Sequence information was used to assign which amino acids were encoded at all polymorphic positions. Three-dimensional modeling was performed to explore the effect of the key residues on the HLA-DRB1 molecule.

RESULTS

Strong susceptible association for allele DRB1*07:01 was observed in OBI carriers. The amino acid variation at HLA-DRβ1 molecule revealed susceptible associations for residues Gln^4β, Val^57β(P9), Ser^60β(P9) and Val^78β(P4), the amino acids Arg^4β, Asp^57β(P9), Tyr^60β(P9) and Tyr^78β(P4) showed protective associations.

CONCLUSION

Alleles DRB1*07:01 showed strong susceptible associations in OBI carriers. The amino acid variations in DRβ molecules revealed significant molecular markers for susceptibility and protection from OBI in Shaanxi Han population.

Hepatitis B Virus Chronic Infection in Blood Donors from Asian and African High or Medium Prevalence Areas: Comparison According to Sex

Immune control of various infectious diseases, particularly viral, was shown to be more efficient for females than males. Response to viral vaccines (HAV, HBV) was higher in females. Data on hepatitis B virus (HBV) markers accumulated over 15 years in blood donors was stratified according to sex, including HBsAg, HBV viral load and levels of anti-HBs in areas where genotypes B and C (China), genotype D (Iran, Lebanon, Tunisia) and genotype E (Ghana, Burkina Faso, Gabon) were prevalent. HBsAg was screened by either ELISA or rapid tests, anti-HBc and anti-HBs by ELISA, HBV DNA load by a standardized method across sites. In Ghanaian children less than 5 years, HBV DNA load was significantly lower in females than in males (p = 0.035). In China, Ghana, Burkina Faso and Gabon blood donors, median HBsAg prevalence was ~5% and 3% in China, ~8.5% and 4.5% in Gabon, ~16% and 11% in Burkina Faso and ~11% and 7% in Ghana for male and female donors, respectively (p < 0.001). In HBsAg+ Ghanaian blood donors, distribution and median viral load were not significantly different between sexes; occult hepatitis B infections (OBI) were significantly more frequent in males. In Chinese blood donor anti-HBc+ and anti-HBs+, anti-HBs levels tended to be higher in males but vaccinated donors’ anti-HBs+ only, while anti-HBs levels were females > males. In areas where genotypes B-E are dominant, the prevalence of chronic HBV infection (HBsAg+) seems better controlled before age 16−18 by females infected vertically or horizontally. OBIs appear considerably more frequent in men, suggesting lower efficacy of HBV infection control. Female blood donors appear significantly safer from HBV than males, and their donation should be encouraged.

The impact of nucleic acid testing to detect human immunodeficiency virus, hepatitis C virus, and hepatitis B virus yields from a single blood center in China with 10-years review

BACKGROUND

Since 2010, the Blood Center of Zhejiang province, China, has conducted a pilot nucleic acid amplification testing (NAT) screening of blood donors for Hepatitis B virus (HBV), Hepatitis C virus (HCV), and Human immunodeficiency virus (HIV). This study aims to assess the results of NAT testing over 10 years to establish the effects and factors influencing NAT yields of HBV, HCV, and HIV.

METHODS

Blood donations from seven different blood services were screened for HBV DNA, HCV RNA, and HIV RNA using 6 mini pools (6MP) or individual donation (ID)-NAT method between August 1, 2010, and December 31, 2019, at the NAT centralized screening center. We compared 3 transcription-mediated amplification (TMA) assays and 2 polymerase chain reaction (PCR) assays. Further, HBV, HCV, and HIV NAT yields were calculated and donor characteristics and prevalence of HBV NAT yields analyzed. Donors with HCV and HIV NAT yield were also followed up.

RESULTS

1916.31 per million donations were NAT screening positive overall. The NAT yields for HBV, HCV, HIV and non-discriminating reactive were 1062.90 per million, 0.97 per million, 1.45 per million, and 850.99 per million, respectively, which varied in the seven blood services and different years. HBV NAT yields were higher than those of HCV and HIV and varied across demographic groups. Risk factors included being male, old age, low education level, and first-time donors. We found no differences in NAT yields of HBV, HCV, and HIV between the 3 TMA and 2 PCR assays; nonetheless, statistically, significant differences were noted between the five assays.

CONCLUSION

In summary, NAT screening in blood donations reduces the risk of transfusion-transmitted infections and shortens the window period for serological marker screening. Therefore, a sensitive NAT screening method, ID-NAT workflow, and recruitment of regular low-risk donors are critical for blood safety.

E2 Site Mutations in S Protein Strongly Affect Hepatitis B Surface Antigen Detection in the Occult Hepatitis B Virus

The mechanism of occult hepatitis B infection (OBI) has not yet been fully clarified. Our previous research found that novel OBI-related mutation within S protein, E2G, could cause the hepatitis B surface antigen (HBsAg) secretion impairment, which resulted in intracellular accumulation in OBI of genotype B. Here, to further explore the role of E2 site mutations in the occurrence of OBI, we analyzed these site mutations among 119 OBI strains identified from blood donors. Meanwhile, 109 wild-type HBV strains (HBsAg positive/HBV DNA positive) were used as control group. Furthermore, to verify the E2 site mutations, two conservative 1.3-fold full-gene expression vectors of HBV genotype B and C (pHBV1.3B and pHBV1.3C) were constructed. Then, the E2 mutant plasmids on the basis of pHBV1.3B or pHBV1.3C were constructed and transfected into HepG2 cells, respectively. The extracellular and intracellular HBsAg were analyzed by electrochemical luminescence and cellular immunohistochemistry. The structural characteristics of S proteins with or without E2 mutations were analyzed using relevant bioinformatics software. E2 mutations (E2G/A/V/D) existed in 21.8% (26/119) of OBIs, while no E2 mutations were found in the control group. E2G/A/V/D mutations could strongly affect extracellular and intracellular level of HBsAg (p < 0.05). Notably, unlike E2G in genotype B that could cause HBsAg intracellular accumulation and secretion decrease (p < 0.05), E2G in genotype C could lead to a very significant HBsAg decrease both extracellularly (0.46% vs. pHBV1.3C) and intracellularly (11.2% vs. pHBV1.3C) (p < 0.05). Meanwhile, for E2G/A mutations, the relative intracellular HBsAg (110.7-338.3% vs. extracellular) and its fluorescence intensity (1.5-2.4-fold vs. with genotype-matched pHBV1.3B/C) were significantly higher (p < 0.05). Furthermore, N-terminal signal peptides, with a typical cleavage site for peptidase at positions 27 and 28, were exclusively detected in S proteins with secretion-defective mutants (E2G/A). Our findings suggest that: (1) E2G/A/V/D mutations were confirmed to significantly influence the detection of HBsAg, (2) the underlying mechanism of OBI caused by E2G mutation is quite different between genotype B and genotype C, and (3) E2G/A could produce a N-terminal truncated S protein, which might attribute to the HBsAg secretion impairment in the OBIs.

Associations Between Gastric Cancer Risk and Virus Infection Other Than Epstein-Barr Virus: A Systematic Review and Meta-analysis Based on Epidemiological Studies

INTRODUCTION

Besides Helicobacter pylori and Epstein-Barr virus, other viruses might play potential roles in gastric carcinogenesis. This systematic review and meta-analysis was conducted to compare the prevalence of the viruses between gastric cancer (GC) and any controls.

METHODS

Comprehensive literature was searched up to January 25, 2019, and search was updated on April 6, 2020. The studies that compared the prevalence of viruses other than Epstein-Barr virus between GC and healthy or nonmalignant controls were eligible. Stata 12.0 software was used for heterogeneity tests and meta-analyses. Meanwhile, subgroup analysis, sensitivity analysis, and publication bias evaluation were performed where applicable. The power (1-β) was estimated by the PASS 11 software for each individual study.

RESULTS

A total of 41 eligible studies were included, concerning 11 kinds of viruses. Prevalence were significantly higher in GC for hepatitis B virus (odds ratio [OR] = 1.39, 95% confidence interval [CI] 1.11-1.75), human cytomegalovirus (OR = 2.25, 95% CI 1.14-4.43), human papillomavirus (HPV) (OR = 1.63, 95% CI 1.05-2.54), and John Cunningham virus (OR = 2.52, 95% CI 1.26-5.04). In subgroup analyses, HPV-16 infection was significantly associated with GC (OR = 2.42, 95% CI 1.00-5.83).

DISCUSSION

This study demonstrated that hepatitis B virus, human cytomegalovirus, HPV, and John Cunningham virus were more prevalent in GC. However, the causal relationship between their infection and risk of GC remains inconclusive, and further investigations are required.

Characteristic of HBV nucleic acid amplification testing yields from blood donors in China

BACKGROUND

Nucleic acid amplification testing (NAT) for blood screening has been previously performed in some countries to determine NAT yields. The current study sought to explore the non-discriminating reactive NAT yields using individual-NAT (ID-NAT) and characteristics of HBV NAT yields through a 10-year retrospective analysis in Zhejiang, China.

METHODS

Blood donations were analyzed using individual-NAT mode by the transcription-mediated amplification (TMA) method. Supplementary HBV serological tests were performed using chemiluminescent immunoassay, and HBV viral load assay was performed by real-time polymerase chain reaction. Follow-up studies were performed in partial donors with low HBV viral loads.

RESULTS

Non-discriminating reactive NAT yields and HBV NAT yields varied in different years. The yields ranged from 853.73 per million to 2018.68 per million and 624.60 per million to 1669.50 per million, respectively. In the 476 NAT yields, 19 were probable window periods (WP), 33 probable occult hepatitis B virus infections (OBIs), 409 were confirmed OBIs and 15 were chronic HBV infections. ID-NAT results were categorized in four groups, and the findings showed that the levels of HBV DNA viral loads were different in the four different groups (χ² = 275.02, p < 0.01). HBV viral load distribution was significantly different between anti-HBs positive and anti-HBc positive samples (χ² = 49.429, p < 0.01). Notably, only 42.03% donors were NAT repeated positive in the 138 repeat donors' follow up tests.

CONCLUSION

NAT screening of blood donations can reduce the risk of transfusion-transmitted HBV infections. Positive proportions of anti-HBs and anti-HBc are correlated with the HBV viral load level. However, low level of viral load donors pose risks in HBV NAT assays, and show fluctuating state for HBV viral load and leads to non-repeated NAT results during follow up studies.

High Frequency Occult Hepatitis B Virus Infection Detected in Non-Resolved Donations Suggests the Requirement of Anti-HBc Test in Blood Donors in Southern China

Background

Most Chinese Blood Centers adopted mini pool (MP) nucleic acid testing (NAT) for HBV screening due to high cost of Individual donation (ID) NAT, and different proportions of MP-reactive but ID-non-reactive donations (MP+/ID-, defined as non-resolved donations) have been observed during daily donor screening process. Some of these non-resolved donations are occult HBV infections (OBIs), which pose potential risk of HBV transmission if they are not deferred. This study is aimed to further analyze these non-resolved donations.

Methods

The non-resolved plasma samples were further analyzed by serological tests and various HBV DNA amplification assays including quantitative PCR (qPCR) and nested PCR amplifying the basic core and pre-core promoter regions (BCP/PC; 295 base pairs) and HBsAg (S) region (496 base pairs). Molecular characterizations of HBV DNA+ non-resolved samples were determined by sequencing analysis.

Results

Of 17,226 MPs from 103,356 seronegative blood donations, 98 MPs were detected reactive for HBV. Fifty-six out of these 98 (57.1%) reactive MPs were resolved as HBV DNA+, but the remaining 42 pools (42.9%, 252 donations) were left non-resolved with a high rate (53.2%) of anti-HBc+. Surprisingly, among 42 non-resolved MPs, 17 contained one donation identified as OBIs by alternative NAT assays. Sequence analysis on HBV DNAs extracted from these OBI donations showed some key mutations in the S region that may lead to failure in HBsAg detection and vaccine escape.

Conclusion

A total of 53.2% of the non-resolved donations were anti-HBc+, and OBIs were identified in 40.5% of these non-resolved pools. Therefore, non-resolved donations with anti-HBc+ might pose potential risk for HBV transmission. Our present analysis indicates that anti-HBc testing in non-resolved donations should be used to identify OBIs in order to further increase blood safety in China.

Role of core protein mutations in the development of occult HBV infection

BACKGROUND & AIMS

Occult HBV infection (OBI) is associated with transfusion-transmitted HBV infection and hepatocellular carcinoma. Studies on OBI genesis have concentrated on mutations in the S region and the regulatory elements. Herein, we aimed to determine the role of mutations in the core region on OBIs.

METHODS

An OBI strain (SZA) carrying 9 amino acid (aa) substitutions in the core protein/capsid (Cp) was selected by sequence alignment and Western blot analysis from 26 genotype B OBI samples to extensively explore the impact of Cp mutations on viral antigen production in vitro and in vivo.

RESULTS

A large panel of 30 Cp replicons were generated by a replication-competent pHBV1.3 carrying SZA or wild-type (WT) Cp in a 1.3-fold over-length of HBV genome, in which the various Cp mutants were individually introduced by repairing site mutations of SZA-Cp or creating site mutations of WT-Cp by site-directed mutagenesis. The expression of HBcAg, HBeAg, and HBsAg and viral RNA was quantified from individual SZA and WT Cp mutant replicons in transfected Huh7 cells or infected mice, respectively. An analysis of the effect of Cp mutants on intracellular or extracellular viral protein production indicated that the W62R mutation in Cp had a critical impact on the reduction of HBcAg and HBeAg production during HBV replication, whereas P50H and/or S74G mutations played a limited role in influencing viral protein production invivo.

CONCLUSIONS

W62R and its combination mutations in HBV Cp might massively affect HBcAg and HBeAg production during viral replication, which, in turn, might contribute to the occurrence of OBI.

LAY SUMMARY

Occult hepatitis B virus infections (OBIs) have been found to be associated with amino acid mutations in the S region of the HBV, but the role of mutations in the core protein (Cp) remains unclear. In this study, an OBI strain (SZA) carrying 9 amino acid substitutions in Cp has been examined comprehensively in vitro and in vivo. The W62R mutation in Cp majorly reduces HBcAg and HBeAg production during HBV replication, potentially contributing to the occurrence of OBI.

Novel hepatitis B virus surface antigen mutations associated with occult genotype B hepatitis B virus infection affect HBsAg detection

The causative factors of occult hepatitis B infection are complicated and not yet been fully elucidated. Mutations in hepatitis B virus (HBV) S gene are one of the factors may contributing to occult infection. In this study, 89 blood donors with genotype B occult HBV infection were investigated. Fifty-seven hepatitis B surface antigen (HBsAg)-positive/HBV DNA-positive blood donors served as control group for comparison. Occult HBV-related mutations with a high incidence (P < .05) in the S gene were identified. To further verify these occult infection-related mutations, a conservative full-gene expression vector of HBV B genotype (pHBV1.3B) was constructed. Then, the mutant plasmids on the basis of pHBV1.3B were constructed and transfected into HepG2 cells. Extracellular as well as intracellular HBsAg was analysed by electrochemical luminescence and cellular immunohistochemistry. Ten occult infection-related mutations (E2G, Q101R, K122R, M133T, D144E, G145R, V168A, S174N, L175S and I226S) were significantly more frequent in the occult infection group (P < .05). Five of the ten mutations (E2G, D144E, G145R, V168A and S174N) strongly decreased extracellular HBsAg level (P < .05) in the transfection system. Notably, the E2G mutation had the most significant impact on the ratio of extracellular HBsAg (3.8% vs pHBV1.3B) and intracellular HBsAg (239.3% vs pHBV1.3B) (P < .05), and the fluorescence density of E2G mutant HBsAg was significantly higher than that of pHBV1.3B (P < .0001). Hence, ten mutations were associated with genotype B occult HBV infection; E2G and V168A were novel mutations which we confirmed significantly affect HBsAg detection. E2G might cause HBsAg secretion impairment that results in intracellular accumulation and a decrease in HBsAg secretion.

Occult HBV infection in Chinese blood donors: role of N-glycosylation mutations and amino acid substitutions in S protein transmembrane domains

Occult hepatitis B virus infection (OBI) is a low-level asymptomatic phase of HBV infection. Evidence of OBI clinical relevance is emerging but the mechanisms of its occurrence remain unclear. In this study, the molecular characteristics of 97 confirmed OBI from Chinese blood donors were analyzed and relevant mutations were identified. Recombinant HBsAg bearing these mutations were expressed in vitro and the antigenicity and HBsAg secretion properties were analyzed. Results showed that 45 (46.4%) genotype B, 50 (51.5%) genotype C, and 2 (2.1%) genotype D sequences were identified. Two groups of mutations in the S gene were significantly associated with OBI. The first group included mutations creating new N-linked glycosylation sites at positions s116, s123, s130, and s131 + s133 or removing the existing one at s146. Mutations TCT123-125NCT/NFT were associated with reduced antigenicity, while TST116-118NST, GTS130-132NTS, and TSM131-133NSS/NYT/NST were associated with varying levels of impaired HBsAg secretion. N146 mutations had no effect on HBsAg production pattern. The second group included substitutions within the S transmembrane domains TMD1-3. Only mutations C85R, L87R, L88R, and C90R within TMD2 were associated with defective HBsAg production. These mutations appear to be rare and mostly strain specific but they may contribute to the multifactorial occurrence of OBI.

Occurrence of occult hepatitis B virus infection associated with envelope protein mutations according to anti-HBs carriage in blood donors

OBJECTIVES

Occult hepatitis B virus infection (OBI) carries a risk of hepatitis B virus (HBV) transmission and hepatocellular carcinoma. As previous studies have had a limited sample size, the characteristics of OBI with genotype B and C (OBI_B and OBI_C) mutations relating to hepatitis B surface antibody (anti-HBs) elicited by vaccination or a limited host immune response to HBV have not been fully explored.

METHODS

In this study, the occurrence of OBI_B or OBI_C strains associated with envelope protein (pre-S/S) amino acid substitutions obtained from 99 blood donors stratified according to anti-HBs carriage were characterized extensively.

RESULTS

According to the presence of anti-HBs within each genotype, the number and frequency of substitution sites specific for anti-HBs(-) OBI_B were higher than those specific for anti-HBs(+) OBI_B strains (67 vs 31; 117 vs 41), but the reverse pattern was found in OBI_C strains (3 vs 24; 3 vs 26). Mutations pre-s₁T68I and sQ129R/L were found uniquely in 15-25% of anti-HBs(+) OBI_B carriers and mutation pre-s₁A54E was found preferentially in anti-HBs(+) OBI_C, while 17 substitutions were found preferentially in 11-38% of anti-HBs(-) OBI_B strains. In the major hydrophilic region (MHR) region, mutations sS167 in OBI_B, sT118 in OBI_C, and sA166 in both genotypes were possibly immune-induced escape mutation sites.

CONCLUSIONS

Several mutations in pre-S/S of OBI appeared to be associated with carrier anti-HBs pressure, which might be risk factors for potential reactivation of viruses under anti-HBs selection in OBI carriers.

Update of the statements on biology and clinical impact of occult hepatitis B virus infection

In October 2018 a large number of international experts with complementary expertise came together in Taormina to participate in a workshop on occult hepatitis B virus infection (OBI). The objectives of the workshop were to review the existing knowledge on OBI, to identify issues that require further investigation, to highlight both existing controversies and newly emerging perspectives, and ultimately to update the statements previously agreed in 2008. This paper represents the output from the workshop.

Nearly half of Ultrio plus NAT non-discriminated reactive blood donors were identified as occult HBV infection in South China

Background

Blood donor plasma samples were detected by the Ultrio Plus NAT system for HBV, HCV and HIV-1 in Shenzhen blood center, China. Reactive samples underwent further discriminatory testing of a single virus by the same methodology. A large number of cases of non-discriminated reactive (NDR) donors were found, leaving potential risk of transmitting HBV if not deferrals. This study identified those non-discriminated samples.

Methods

The NDR plasma samples from blood donation screening were detected and classified by additional molecular and serological tests. Molecular characterizations of DNA+ NDR were determined by sequencing analysis.

Results

A number of 259 (0.21%) NDR plasma samples from screening of 123,280 eligible blood donors were detected, which presented a higher rate (91.1%) of anti-HBc reactivity and nearly half (46.7%) of HBV DNA+ that classified as occult HBV infection (OBI). Most OBI strains were wild-type HBV, but some substitutions V168A, S174 N, V177A, Q129R/L/H, G145A/R in S region of genotype B (OBI_B) and T47K/V/A, P49H/L, Q101R/H/K, S174 N, L175S, V177A, T118 M/R/K, G145R/A/K/E, R160K/N in S region of genotype C (OBI_C) strains were identified in high frequency.

Conclusion

Nearly half of NDR blood samples were identified as OBI, in which a number of important mutations were detected. NDR donation might have potential risk for HBV transmission, but need to be further investigated.

Chronic hepatitis B virus infection and total and cause-specific mortality: a prospective cohort study of 0.5 million people

OBJECTIVES

Chronic hepatitis B virus (HBV) infection is associated with a higher risk of liver diseases. Substantial uncertainty remains, however, about the associations of HBV infection with mortality from extrahepatic causes, especially from subtypes of cardiovascular diseases. We prospectively examined the association of chronic HBV infection with total and cause-specific mortality.

DESIGN

Population-based prospective cohort study.

SETTING

China Kadoorie Biobank in which participants from 10 geographically diverse areas across China were enrolled between 2004 and 2008.

PARTICIPANTS

475 801 participants 30-79 years of age without reporting major chronic diseases at baseline were enrolled. Hepatitis B surface antigen (HBsAg) was tested using an on-site rapid test strip at baseline.

PRIMARY AND SECONDARY OUTCOME MEASURES

Total and cause-specific mortality.

RESULTS

A total of 35 822 deaths were recorded during ~10 years of follow-up. In multivariable-adjusted analyses, compared with HBsAg-negative participants, HBsAg-positive participants had an increased risk of total mortality (HR=2.01, 95% CI: 1.91 to 2.12), which was higher in men (HR=2.16, 95% CI: 2.01 to 2.31) than in women (HR=1.74, 95% CI: 1.60 to 1.90). Presence of HBsAg was associated with increased mortality from liver cancer (1339 deaths, HR=13.95, 95% CI: 12.46 to 15.62), infections (410 deaths, HR=10.30, 95% CI: 8.21 to 12.94), digestive diseases (688 deaths, HR=6.83, 95% CI: 5.49 to 8.50), intracerebral haemorrhage (4077 deaths, HR=1.38, 95% CI: 1.14 to 1.68) and ischaemic heart diseases (4624 deaths, HR=1.31, 95% CI: 1.09 to 1.58). The positive association between HBsAg status and risk of death was stronger in participants younger than 50 years, smokers, physically active or non-hypertensive participants.

CONCLUSIONS

Among Chinese adults, chronic HBV infection was associated with increased mortality from a range of hepatic and extrahepatic diseases.

Incidence of hepatitis B virus infection in young Chinese blood donors born after mandatory implementation of neonatal hepatitis B vaccination nationwide

This study was carried out to determine the incidence of hepatitis B virus (HBV) infection in the young generation born after mandatory implementation of hepatitis B vaccination since 1992. Repeat blood donors born between 1992 and 1997 were enrolled, who gave blood at least twice during the past 3 years. Donors were tested for HBV infection markers of HBsAg, anti-HBc, anti-HBs and viral DNA by immunoassays (EIAs) and nucleic acid tests (NAT). A total of 14 937 pre-donation screening qualified young repeat donors aged 18-23 years were tested with 9 (0.06%) being HBsAg by EIA and 10 (1:1494) HBV DNA positive by Ultrio NAT (10.4 IU/mL), respectively. HBV DNA was further detected in 1:192 (9/1732) anti-HBc+ repeat donors with Ultrio Plus NAT (3.4 IU/mL). Most cases were identified as occult HBV infection (OBI). Of 14 937 repeat donors, 20.9% were anti-HBc+ positive, while approximately 50% of 12 024 repeat donors were anti-HBs negative or had levels <100 IU/L. HBsAg+ or OBI strains were classified as wild type of genotype B or genotype C. Incident HBV infection in repeat donors was approximately 1:18.5 person-years (1.1%/year) but significantly less frequent in donors with confirmed HBV vaccination (2.4%-3.3%) than those unsure of vaccination status (10.5%; P = .0023). Hepatitis B virus vaccination appears largely protective of HBV infection, but incidence of infections increases in young adults with mostly undetectable or low anti-HBs or occasionally high anti-HBs. A boost of hepatitis B vaccine for adolescents prior to age 18 years may reduce HBV infection, and implementation of more sensitive NAT in blood donation screening may improve HBV safety in blood transfusion.

The dynamics of integration, viral suppression and cell-cell transmission in the development of occult Hepatitis B virus infection

BACKGROUND

Out of several phases of HBV infection, the least understood phase is occult hepatitis B virus infection. The paucity of data due to non-availability of biological tissues and the prerequisite of ultra-sensitive assays for the detection of occult hepatitis B virus infection prompted us to utilize mathematical modeling in determining mechanisms that lead to occult hepatitis B virus infection and characteristics of HBV infection during occult hepatitis B virus infection.

METHODS

We proposed two mathematical models (M1 and M2), considering two different phenomenon for episomal maintenance and accumulation of covalently closed circular DNA (cccDNA) in infected hepatocytes: (i) M1 - recirculation of the relaxed circular DNA/double-stranded linear DNA from cytoplasm to the nucleus, and (ii) M2 - reinfection of infected hepatocytes with virions. We further incorporated the dynamics of integrated Hepatitis B virus DNA (iHBV) to investigate its role in the development of occult hepatitis B virus infection.

RESULTS

The analysis showed that the main mechanism for the spread of infection during occult hepatitis B virus infection is cell-to-cell transmission and not cell-free virus transmission. A significant viral suppression (of at least 99% from its peak production values) was essential but not sufficient in the development of occult hepatitis B virus infection under M1; however under M2, the viral suppression was neither sufficient nor essential as the inhibition of the production of HBsAg without viral suppression can also explain the development of occult hepatitis B virus infection. Our analysis also revealed that occult hepatitis B virus infection seropositive cases are more likely to progress into liver cirrhosis compared to occult hepatitis B virus infection seronegative cases. The iHBV was found to be mostly silent (by either being absent or non-productive for HBsAg) during occult hepatitis B virus infection.

CONCLUSION

The viral suppression is neither essential nor sufficient to explain the development of occult hepatitis B virus infection on its own. Not only the viral suppression but the inhibition -of the production and the export of HBsAg from cccDNA and iHBV also plays an important role in the development of occult hepatitis B virus infection. This is the first study, which incorporates the dynamics of iHBV and shows that HBV primarily spreads via cell-cell transmission during occult hepatitis B virus infection.

Occult Hepatitis B Virus Infection in Hyperlipidemia Patients

Chronic hepatitis B virus (HBV) infection is associated with lower prevalence of hyperlipidemia (HLP). However, occult HBV infection (OBI) in HLP patients has not yet been explored. OBI is defined as the presence of detectable HBV DNA in serum or liver tissue but undetectable HBV surface antigen in serum. In this study, 1,036 HLP patients and 1,134 replacement blood donor controls were recruited. Among them, 252 HLP patients and 255 blood donors with antibody to HBV core positive were selected and analyzed. HBV DNA was confirmed by nucleic acid testing assays, and nucleotide mutations were analyzed. OBI was detected in 9.5% (24/252) of HLP patients and 2.4% (6/255) of blood donors, respectively (P < 0.001). In HLP population, 41.7% of OBI and 13.6% of non-OBI carriers were associated with daily alcohol consuming > 30 g/day (P < 0.01), while in control population those rates were not statistically different between OBI and non-OBI carriers (P > 0.05). Viral load of OBI in HLP patients was higher than that of OBI in blood donors (P < 0.05), which was a positive correlation between total cholesterol and HBV viral load levels (r = 0.474 P = 0.019). HBV vaccination rate was found significantly lower in OBI HLP patients than that in non-OBI HLP patients (P < 0.01). Importantly, mutations were found in basic core promoter region of HBV among OBI HLP patients. In conclusion, the frequency of OBI is significantly higher in HLP patients, especially those patients with heavy daily alcohol consumption.

Association of human leukocyte antigen polymorphisms with occult hepatitis B virus infection in a Shaanxi Han population

BACKGROUND

Occult hepatitis B virus (HBV) infection (OBI) is defined as HBV DNA detection in serum or in the liver by sensitive diagnostic tests in HBV surface antigen (HBsAg) negative patients with or without serologic markers of previous HBV exposure. Because the human leukocyte antigen (HLA) system is an integral component of the immune response, we hypothesized that the highly polymorphic HLA genes were the key determinants of HBV persistence and clearance. The present study aimed to calculate the allelic frequency of HLA loci and investigate the association between HLA alleles and the outcome of OBI in Shaanxi Han population in the northwest of China.

METHODS

We conducted a case-control study between 107 OBI subjects and 280 healthy control individuals from blood donors of Shaanxi Blood Center. Five HLA loci, including HLA-A,-B,-C,-DRB1 and -DQB1, were selected and further genotyped using a polymerase chain reaction sequence-based typing (SBT) method.

RESULTS

Using the chi-squared test, we found that the allele frequencies of HLA-B*44:03 [odds ratios (OR) = 2.146, 95% confidence interval (CI) = 1.070-4.306, p = 0.028]; C*07:01 (OR = 4.693, CI = 1.822-12.086, p = 0.000); DQB1*02:02 (OR = 1.919, CI = 1.188-3.101, p = 0.007); and DRB1*07:01 (OR = 2.012, CI = 1.303-3.107, p = 0.001) were markedly higher in the OBI group compared to the healthy control group. The allele frequencies of HLA-DRB1*08:03 (OR = 0.395, CI = 0.152-1.027, p = 0.049); DRB1*15:01 (OR = 0.495, CI = 0.261-0.940, p = 0.029); and DQB1*06:02 (OR = 0.500, CI = 0.249-1.005, p = 0.048) were obviously lower in the OBI group compared to the healthy control group. These data indicated that HLA-B*44:03, C*07:01, DQB1*02:02 and DRB1*07:01 were related to OBI infection, whereas HLA-DRB1*08:03, DRB1*15:01 and DQB1*06:02 alleles were associated with HBV DNA clearance in a Shaanxi Han population.

CONCLUSIONS

The results of the present study suggest that host HLA gene is an important influencing factor for OBI pathogenesis.

The characteristics of hepatitis B surface antigen (HBsAg)-negative hepatitis B virus (HBV) infection in Chinese blood donors: a follow-up study of donors tested negative for HBsAg and reactive for simultaneous nucleic acid testing of HBV, hepatitis C virus, and human immunodeficiency virus

BACKGROUND

The real infection status of hepatitis B virus (HBV) of hepatitis B surface antigen (HBsAg)-negative yet nucleic acid test (NAT)-positive blood donors is difficult to clarify. Detailed follow-up study is needed for analyzing the infectivity of these blood donors.

STUDY DESIGN AND METHODS

Blood donors who screened negative for HBsAg and reactive for simultaneous NAT of HBV, hepatitis C virus (HCV), and human immunodeficiency virus (HIV) were included in a follow-up epidemiologic questionnaire survey and contributed follow-up samples for further testing. The follow-up samples were tested repeatedly for the serologic markers and HBV DNA. The genotypes and sequence mutations of HBV infected by 11 HBV DNA-positive donors were analyzed through the amplification and sequencing of HBV S region.

RESULTS

Of the 46 donors included in this study, 89.1% were infected with HBV (41/46), including one (2.2%) window period infection, three (6.5%) recovered infections, and 37 (80.4%) occult HBV infections (OBIs). The S region of HBV was successfully amplified and sequenced for seven donors, five infected with Genotype B (71.4%), one with Genotype C (14.3%), and one with Genotype D (14.3%). Mutations in the S region were detected in four donors (57.1%) CONCLUSIONS: This is the first detailed study with multiple follow-up testing of the HBV infection status among blood donors who were tested negative for HBsAg and reactive for simultaneous NAT of HBV, HCV, and HIV. Most of these donors were infected with HBV with very low viral load. Our findings indicate that it is important to improve the sensitivity of NAT so as to decrease the residual risk of transfusion-transmitted HBV infection.

Screening and diagnosis of HBV in low-income and middle-income countries

HBV testing and diagnosis of HBV-related liver disease in low-income and middle-income countries differs substantially from that in developed countries in terms of access to resources and expensive technologies requiring highly specialized staff. For identification and classification of HBV infection, genomic amplification methods to detect and quantify HBV DNA are often nonexistent or available only in central laboratories of major cities. When samples from peripheral locations do arrive, delays in receiving results generate loss to follow-up. Testing is often limited to measurement of hepatitis B surface antigen (HBsAg), alanine aminotransferase levels, aspartate aminotransferase to platelet ratio index and hepatitis B e antigen (HBeAg) to determine indications for antiviral therapy (AVT). Utilization of AVT is limited by cost and availability, particularly when patients are not covered by health insurance. The natural history of HBV infection is influenced by genotypes B and C in East Asia, where decades of immune tolerance have led to mostly vertical transmission; in sub-Saharan Africa, where genotypes A1 and E predominate, infection is transmitted horizontally between young children, followed by a nonreplicative phase. In both regions, cirrhosis and hepatocellular carcinoma are common and would be considerably ameliorated by AVT. Implementation of the HBV vaccine since the 1990s in Asia and 2000s in Africa has decreased the incidence of HBV, but vaccine failure and insufficiently effective prevention remain concerning issues.

Serological Patterns and Molecular Characterization of Occult Hepatitis B Virus Infection among Blood Donors

BACKGROUND

Hepatitis B infections, characterized by the presence of a viral genome without detectable hepatitis B surface antigen (HBsAg; Occult hepatitis B infection [OBI]), have been reported recently.

OBJECTIVES

We performed serological and molecular characterization of OBI among blood donors at Jiangsu province blood center during years 2013 and 2014.

METHODS

All donor samples were routinely screened by double enzyme-linked immunosorbent assay (ELISA) for hepatitis C virus (HCV), hepatitis B virus (HBV), human immunodeficiency virus (HIV), Treponema pallidum (TP), and alanine aminotransferase (ALT). Single-reactive, nonreactive, and ALT-elevated samples were pooled or resolved by nucleic acid testing (NAT). Seromarkers were examined in HBsAg-/DNA+ samples. After 1 to 12 months of follow up, seromarkers were screened again to verify OBI samples.

RESULTS

We studied 157119 samples from blood donors. A total of 154397 ELISA nonreactive donor samples were identified, and HBV DNA was detected in 81 samples; no samples were positive for HIV or HCV RNA. Hepatitis B virus viral loads in most donors were less than 20 - 200 IU/mL. There was only one HBsAg-positive sample. Eighty HBsAg-/DNA+ samples were evaluated further. Of these samples, 85% (68/80) were reactive for anti-HBc and 36.2% (29/800) were reactive for anti-HBc and anti-HBs; 11.3% (9/80) did not have any detectable serological markers. Twenty-nine donors were followed up. One was HBsAg ELISA positive, and of six seronegative donors, all had anti-HBc and anti-HBs, but were negative for DNA. Samples were HBV genotypes B, C and D. Mutations in the S region of HBV DNA included S114T, G119R, P120S, T125M, C139Y, T140I, C147W, T148A, A159V/G, E164D, V168A, and R169C.

CONCLUSIONS

Overall, we found that OBI was rare, but that the prevalence of OBI was slightly higher in Jiangsu than in other areas of China.

Prevalence of hepatitis B surface antigen (HBsAg) in a blood donor population born prior to and after implementation of universal HBV vaccination in Shenzhen, China

Background

Neonatal hepatitis B vaccination program at birth has been implemented nationwide since 1992 in China. However, current HBV prevalence status in blood donors has not been entirely examined, which may impact HBV safety in blood donations as the vaccinees over 18 years old progressively become the majority population of blood donors.

Methods

In this study, 569,145 blood donors were screened for HBsAg by rapid tests and enzyme immunoassays, among them 475,538 blood samples with negative HBsAg were further screened for HBV DNA by nucleic acid testing between 2005 and 2014 at Shenzhen blood center.

Results

An overall 2.3 % HBsAg prevalence was found in the blood donor population during the past 10 years (2.86 % in 2005, 1.76 % in 2010, and 2.79 % in 2014, respectively). HBsAg seroconversion occurred in 0.37 % of repeat-donors. When stratified by age, the prevalence of HBsAg was found significantly higher in younger donors age 18–25 years (2.73 %) than in those 26–35 years (2.13 %), 36–45 years (2.03 %) and 46–58 years (1.71 %) (P < 0.001), unexpectedly suggesting that younger donors remained at risk of chronic HBV infection. Assuming that donors aged 18–22 born before or after 1992 were non-vaccinated and vaccinated, respectively, HBsAg prevalence was higher in first-time donors born ≥1992 (3.9 %) than prior to 1992 (3.5 %, P = 0.005). The incidence of HBV infection in the 5-year period examined was significantly lower in repeat-donors born ≥1992 (0.27 %) than prior to 1992 (0.6 %, P = 0.008). The yield of HBV DNA+/HBsAg- donors was 1:3,302, including 1:4,486 occult infections and 1:43,231 window period infections.

Conclusion

Young blood donors born after implementation of universal HBV vaccination in China presented higher prevalence of HBsAg but lower incidence of HBsAg seroconversion than older, presumed unvaccinated, donors. HBV vaccine boosting for adolescents at 15–17 years old prior to reaching blood donor age might help improve blood safety.

Characterisation and follow-up study of occult hepatitis B virus infection in anti-HBc-positive qualified blood donors in southern China

BACKGROUND

Most major Chinese blood centres look for hepatitis B surface antigen (HBsAg) and perform nucleic acid testing to screen blood for hepatitis B virus infection. The search for antibodies to the core of hepatitis B virus (anti-HBc) has not been implemented because it would lead to a high rate of discarded blood units. The aim of this study was to evaluate the prevalence of occult HBV infection among anti-HBc-positive qualified blood donors in southern China.

MATERIALS AND METHODS

We tested anti-HBc-positive blood donations negative for HBsAg and HBV DNA by standard NAT from Shenzhen for the presence of HBV DNA by sensitive nested and quantitative polymerase chain reactions. Anti-HBs titres were quantified. HBV DNA-positive donors were traced and followed-up.

RESULTS

Of the 1,033 qualified donors, 47.4% (95% CI: 44.4 to 50.5%) carried anti-HBc as evidence of exposure to HBV. The rate of anti-HBc positivity increased steadily with age, ranging from 32.6% in the age group <30 years to 69.8% in the age group <50 years (p<0.001). Of the 1,033 donors, 777 (75.2%; 95% CI: 72.4 to 77.8%) carried anti-HBs (>10 IU/L). HBV DNA was detected in 14 donors who were anti-HBc-positive, HBsAg-negative and negative by routine NAT. Seven of those 14 specimens had an anti-HBs titre above 100 mIU/mL. The prevalence of OBI in anti-HBc-positive qualified blood donors was 2.86% (95% CI: 1.57 to 4.75%). Eight of the 14 OBI cases were genotype B and one was genotype C; 7/14 cases were followed-up, one case converted to anti-HBe. HBV DNA became undetectable in all follow-up samples.

DISCUSSION

A small proportion of anti-HBc-positive qualified donors carry HBV DNA after HBsAg and NAT screening. This finding suggests the possibility of HBV transmission from asymptomatic donors, especially in areas of high HBV prevalence. More sensitive NAT rather than anti-HBc testing should be considered to improve blood safety.

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.

Are current screening protocols for chronic hepatitis B virus infection adequate?

Chronic hepatitis B virus (HBV) infection screening usually includes only HBV surface antigen (HBsAg) testing; HBV core and surface antibody (anti-HBc, anti-HBs) assays, indicating resolved infection and immunity, are not routinely performed. Yet, serum HBV DNA is measurable in approximately 10% of HBsAg-negative/anti-HBc-positive cases, representing occult HBV infection (OBI). Patient blood samples from 2 Veterans Affairs medical center look-back investigations were screened for HBV infection using HBsAg enzyme immunoassays. Supplementary testing included anti-HBc and anti-HBs enzyme immunoassays. For anti-HBc-positive samples, HBV DNA testing was performed. Background OBI prevalence was further estimated at these 2 facilities based on HBV serology testing results from 1999-2012. Finally, a literature review was performed to determine OBI prevalence in the published literature. Of 1887 HBsAg-negative cohort patients, 98 (5.2%) were anti-HBc positive/anti-HBs negative; and 175 (9.3%), anti-HBc positive/anti-HBs positive. Six of 273 were HBV DNA positive, representing 0.3% of the total tested and 2.2% who were anti-HBc positive/anti-HBs negative or anti-HBc positive/anti-HBs positive. Among 32,229 general population veterans at these 2 sites who had any HBV testing, 4/108 (3.7%) were HBV DNA positive, none of whom were part of the cohort. In 129 publications with HBsAg-negative patients, 1817/1,209,426 (0.15%) had OBI. However, excluding blood bank studies with greater than 1000 patients, the OBI rate increased to 1800/17,893 (10%). OBI is not rare and has implications for transmission and disease detection. HBsAg testing alone is insufficient for detecting all chronic HBV infections. These findings may impact blood donation, patient HBV screening, follow-up protocols for patients assumed to have cleared the infection, and initiation of immunosuppression in patients with distant or undetected HBV.

Association of preS/S Mutations with Occult Hepatitis B Virus (HBV) Infection in South Korea: Transmission Potential of Distinct Occult HBV Variants

Occult hepatitis B virus infection (HBV) is characterized by HBV DNA positivity but HBV surface antigen (HBsAg) negativity. Occult HBV infection is associated with a risk of HBV transmission through blood transfusion, hemodialysis, and liver transplantation. Furthermore, occult HBV infection contributes to the development of cirrhosis and hepatocellular carcinoma. We recently reported the characteristic molecular features of mutations in the preS/S regions among Korean individuals with occult infections caused by HBV genotype C2; the variants of preS and S related to severe liver diseases among chronically infected patients were also responsible for the majority of HBV occult infections. We also reported that HBsAg variants from occult-infected Korean individuals exhibit lower HBsAg secretion capacity but not reduced HBV DNA levels. In addition, these variants exhibit increased ROS-inducing capacity compared with the wild-type strain, linking HBV occult infections to liver cell damage. Taken together, our previous reports suggest the transmission potential of distinct HBV occult infection-related variants in South Korea.

Occult hepatitis B virus infection and blood transfusion

Transfusion-transmitted infections including hepatitis B virus (HBV) have been a major concern in transfusion medicine. Implementation of HBV nucleic acid testing (NAT) has revealed occult HBV infection (OBI) in blood donors. In the mid-1980s, hepatitis B core antibody (HBc) testing was introduced to screen blood donors in HBV non-endemic countries to prevent transmission of non-A and non-B hepatitis. That test remains in use for preventing of potential transmission of HBV from hepatitis B surface antigen (HBsAg)-negative blood donors, even though anti-hepatitis C virus tests have been introduced. Studies of anti-HBc-positive donors have revealed an HBV DNA positivity rate of 0%-15%. As of 2012, 30 countries have implemented HBV NAT. The prevalence of OBI in blood donors was estimated to be 8.55 per 1 million donations, according to a 2008 international survey. OBI is transmissible by blood transfusion. The clinical outcome of occult HBV transmission primarily depends on recipient immune status and the number of HBV DNA copies present in the blood products. The presence of donor anti-HBs reduces the risk of HBV infection by approximately five-fold. The risk of HBV transmission may be lower in endemic areas than in non-endemic areas, because most recipients have already been exposed to HBV. Blood safety for HBV, including OBI, has substantially improved, but the possibility for OBI transmission remains.

High prevalence of anti-hepatitis B core antigen in hepatitis B virus-vaccinated Chinese blood donors suggests insufficient protection but little threat to the blood supply

BACKGROUND

In East Asia, individuals systematically vaccinated at birth to hepatitis B virus (HBV) are an increasing part of the blood donor population. Their environment presents a high risk of contact with HBV. HBV vaccine efficacy and potential safety risk carried by vaccinated donors were examined.

STUDY DESIGN AND METHODS

A total of 2028 vaccinated blood donors were recruited in 2012 and 2013 and tested for serologic (hepatitis B surface antigen [HBsAg], antibody to hepatitis B surface antigen [anti-HBs], and antibody to hepatitis B core antigen [anti-HBc]) and molecular (HBV DNA) markers of HBV. HBsAg, anti-HBs, and viral load were quantified.

RESULTS

Donors 18 to 21 years systematically vaccinated at birth and 22 to 25 years and older donors had both 30.0% negative serology and 1.8% anti-HBc only but the latter group carried significantly higher prevalence of anti-HBc (p < 0.0001). Anti-HBc, mostly associated with anti-HBs, increased from 10.7% at age 18 to 31.5% at age 25. The level of anti-HBs was significantly higher in anti-HBc-positive donors than in anti-HBs-only donors (p < 0.0001). Samples from 24 donors contained low viral load (25 ± 22 IU/mL), half of them undetected by standard nucleic acid testing (NAT), and were classified as four recent infections, 17 occult HBV infections (OBI), and three primary OBIs. Eighteen of 24 carried anti-HBs; 14 of 15 strains were wild-type Genotype B and one was Genotype C.

CONCLUSIONS

In an environment of frequent high Genotype B or C viremia, blood donors vaccinated at birth are frequently but mildly infected: asymptomatic and normal alanine aminotransferase level, identified by anti-HBc seroconversion and boosting of anti-HBs. Low viral load and frequent anti-HBs limit transfusion risk.

Infection of common marmosets with hepatitis C virus/GB virus-B chimeras

The development of vaccination and novel therapy for hepatitis C virus (HCV) has been hampered by the lack of suitable small-animal models. GB virus B (GBV-B), closely related to HCV, causes viral hepatitis in common marmosets (Callithrix jacchue jacchus) and might represent an attractive surrogate model for HCV infection. However, differences exist between GBV-B and HCV in spite of a short genetic distance between the two viruses. Here we report common marmosets infected with two HCV/GBV-B chimeras containing HCV structural genes coding for either whole core and envelope proteins (CE1E2p7) or full envelope proteins (E1E2p7) substituted for the counterpart elements of GBV-B. Naïve animals intrahepatically injected with chimeric RNA transcripts or intravenously injected with sera from primary infected animals produced high levels of circulating infectious chimeric viruses and they developed chronic infection. Tacrolimus-treated marmosets inoculated with a CE1E2p7 chimera had higher viral loads and long-term persistent infection. A moderate elevation of serum aspartate aminotransferase (AST) levels was observed in parallel with viral replication. Chimeras recovered from liver samples revealed 1/958 adaptive viral mutations. Histopathological changes typical of viral hepatitis were observed in liver tissues from all types of HCV chimeras-infected marmosets. HCV core and E2 proteins were detected in liver tissues from infected animals by immunohistochemical staining. Fluctuations of chimeric virus replication in marmosets with spontaneous and sporadic viral clearance might be related to specific antibody and T-cell response to HCV proteins in vivo. Replication of CE1E2p7 chimera was observed in primary hepatocyte cultures by immunofluorescent staining in vitro.

CONCLUSION

Infectious HCV chimeras causing chronic hepatitis in marmosets might constitute a small primate model suitable for evaluation of virus-cell interaction, vaccination, and antiviral therapy against HCV infection.

Performance of two real-time PCR assays for hepatitis B virus DNA detection and quantitation

In-house developed real-time PCR (qPCR) techniques could be useful conjunctives to the management of hepatitis B virus (HBV) infection in resource-limited settings with high prevalence. Two qPCR assays (qPCR1 and qPCR2), based on primers/probes targeting conserved regions of the X and S genes of HBV respectively, were evaluated using clinical samples of varying HBV genotypes, and compared to the commercial Roche Cobas AmpliPrep/Cobas TaqMan HBV Test v2.0. The lower detection limit (LDL) was established at 104 IU/ml for qPCR1, and 91 IU/ml for qPCR2. Good agreement and correlation were obtained between the Roche assay and both qPCR assays (r = 0.834 for qPCR1; and r = 0.870 for qPCR2). Differences in HBV DNA load of > 0.5 Log10 IU/ml between the Roche and the qPCR assays were found in 49/122 samples of qPCR1, and 35/122 samples of qPCR2. qPCR1 tended to underestimate HBV DNA quantity in samples with a low viral load and overestimate HBV DNA concentration in samples with a high viral load when compared to the Roche test. Both molecular tools that were developed, used on an open real-time PCR system, were reliable for HBV DNA detection and quantitation. The qPCR2 performed better than the qPCR1 and had the additional advantage of various HBV genotype detection and quantitation. This low cost quantitative HBV DNA PCR assay may be an alternative solution when implementing national programmes to diagnose, monitor and treat HBV infection in low- to middle-income countries where testing for HBV DNA is not available in governmental health programmes.

A pilot study on screening blood donors with individual-donation nucleic acid testing in China

BACKGROUND

Nucleic acid amplification testing (NAT) is not yet obligatory in China for blood donor screening and the risk of enzyme immunoassay (EIA)-negative, NAT-reactive donations in Chinese blood donors has rarely been reported. The aim of this study was to screen a population of Chinese blood donors using a triplex individual-donation (ID)-NAT assay and assess the safety benefits of implementing NAT.

MATERIALS AND METHODS

Between 1st August, 2010 and 31st December, 2011 all donations at a Chinese blood centre were screened individually using the Procleix® Ultrio® assay, a multiplex NAT assay for the detection of hepatitis B virus (HBV) DNA, hepatitis C virus (HCV) RNA and human immunodeficiency virus-1 (HIV-1) RNA. All donations were also screened for HBsAg, anti-HIV and anti-HCV using two different EIA for each marker. Samples with discordant results between NAT and EIA were further tested with an alternative NAT assay (Cobas® TaqMan®). Potential yield cases (serologically negative/NAT-reactive donors) were further evaluated when possible.

RESULTS

During the study period a total of 178,447 donations were screened by NAT and EIA, among which 169 HBV NAT yield cases (0.095%) were detected. No N AT yield cases were found for HIV-1 or HCV. For the HBV NAT yield cases, follow-up results showed that 11 (6.51%) were probable or confirmed HBV window period infections, 5 (2.96%) were chronic HBV carriers and 153 (90.53%) were probable or confirmed occult HBV infections. There was a statistically significant difference between the NAT-positive rates for first-time vs repeat donations (0.472% vs 0.146%, respectively; P<0.001).

DISCUSSION

Our data demonstrate that the potential HBV yield rate was 1:1,056 for blood donations in the Zhejiang province of China. Implementation of NAT will provide a significant increment in safety relative to serological screening alone.

Six-year pilot study on nucleic acid testing for blood donations in China

A six-year pilot study on nucleic acid testing for HBV, HCV and HIV-1 has been undertaken on sero-negative plasmas in mini-pool and individual donation testing at Shenzhen Blood Center. Of 307,740 sero-negative blood samples, 95 of 102 HBV DNA yields were confirmed positive, 80/95 (84.2%) were classified as occult HBV infection (OBI) and 15 (15.8%) as window period cases. Amongst OBIs, 45% carried anti-HBc only, 41.3% anti-HBc and anti-HBs and 13.7% anti-HBs only. HBV DNA yield was 1:3239. One HCV WP and one HIV-1 infected donations were detected. High residual risk was found in current blood donations screening in China.

Stochastic model for estimating the risk of transfusion-transmitted hepatitis B in Vietnam

BACKGROUND AND OBJECTIVE

Transfusion-transmitted hepatitis B virus (HBV) infection may originate from hepatitis B surface antigen (HBsAg) false-negative blood donors, HBsAg negative and anti-HBc positive blood donors and blood donors with both tests negative. HBV DNA may be present in all these cases and blood may be infectious. The aim of the study was to estimate the risk of transfusion-transmitted HBV in Vietnam using a stochastic Monte Carlo model.

METHODS

A cross-sectional study of HBV prevalence in 1200 potential blood donors in rural Vietnam is used as basis for the Monte Carlo model together with expert panel estimates of occult hepatitis B infection (OBI) prevalence in blood donors.

RESULTS

With 1 000 000 blood donors running in the model, the potential OBI ranged from 658 to 747 blood units per million at 5 percentile and from 1342 to 2507 blood units per million at 95 percentile resulting in the risk of post-transfusion hepatitis ranging from 66 to 250 blood units per million assuming that risk of post-transfusion from potential OBI is 10%. Using the manufacturer's HBsAg sensitivity, the mean rate of blood units per million donations having false-negative HBsAg results was 298 (5-95 percentile: 14-893). When the test sensitivity was set lower, false-negative tests was observed at a mean of 1087 per million (5-95 percentile: 762-3220). The fraction of potential OBI donors increased with the increasing age in both genders.

CONCLUSION

Current HBsAg screening in Vietnam is insufficient in eliminating the risk of transfusion-transmitted HBV infection. The major risk factors are HBsAg false-negative results and OBI. Increased test sensitivity and locally validated HBsAg assays are recommended.

Enhanced detection of hepatitis B virus in Hong Kong blood donors after introduction of a more sensitive transcription-mediated amplification assay

BACKGROUND

A total of 517,072 and 399,326 consecutive donations were screened for hepatitis B virus (HBV) by individual-donation nucleic acid testing (ID-NAT) using Ultrio and Ultrio Plus assays (Novartis Diagnostics), respectively. The impact of more sensitive HBV detection by the latter assay version was established by comparing NAT yield and transmission risk.

STUDY DESIGN AND METHODS

Donations were screened simultaneously for HBV serologic markers and ID-NAT, followed by discriminatory assay and confirmatory test algorithms. Window period (WP) reduction and residual HBV transmission risk were computed using mathematical modeling.

RESULTS

HBV NAT-yield rates for both WP and occult HBV infection (OBI) increased significantly from 1:34,471 to 1:17,362 (p = 0.036) and from 1:5120 to 1:2450 (p < 0.0001), despite a 1.2- and 1.6-fold decrease in hepatitis B surface antigen (HBsAg) incidence and prevalence rates respectively. After adjusting for this bias, the WP and OBI NAT-yield improvement factors were 2.3 and 3.4, respectively, higher than a less than 1.5-fold increase estimated from analytical sensitivity studies on HBV Genotype A and C standards. The current WP transmission risk with Ultrio Plus screening was estimated at 1:55,000 compared to 1:22,000 with HBsAg testing.

CONCLUSION

The observed greater than twofold enhanced WP NAT yield with the Ultrio Plus assay can be explained by greater than 10-fold increased analytical sensitivity in detecting the HBV Genotype B and C strains in Hong Kong. Direct comparison studies of the two assay versions on dilutions of HBV NAT-yield samples are required to confirm this hypothesis.