Second hepatitis C virus transmission by blood components since introduction of mandatory NAT screening in Germany.

BACKGROUND: Viral safety of blood products in Germany has improved significantly over the last two decades. We describe the second documented transfusion-transmitted (TT) episode for the hepatitis C virus (HCV) in Germany since mandatory nucleic acid amplification techniques (NAT) screening was introduced in 1999. STUDY DESIGN AND METHODS: When a repeat donor who had tested negative for anti-HCV tested positive for HCV RNA by NAT in a minipool (MP) of eight, a look-back procedure was initiated. Qualitative, quantitative and genotyping assays were used to investigate the titers of the quarantined fresh frozen plasma (FFP) from the donor and a serum sample from the recipient of the pooled platelet concentrate (PPC). Amplified products of 5'UTR and HVR1 were used for sequence comparison to characterize the HCV genomic identity of donor and recipient samples. RESULTS: All NAT tests utilized in this procedure were able to detect a low HCV RNA titer (~15 IU/ml) in the FFP from the donation. Dilution of FFP by factor 8 was performed to mimic an MP, and the detection rate correlated well with the claimed sensitivity of the tests. Analysis of donor and recipient samples revealed genotype 3a viral transmission confirmed by sequence analysis. CONCLUSION: This TT HCV case could have been prevented by individual donation (ID) NAT. However, a low titer blood donation in the window period (WP) is very rare. Residual risk calculation for TT HCV in the WP revealed that, compared to MP-NAT testing, ID-NAT would improve blood safety only marginally.

Genome Sequences of West Nile Virus Reference Materials.

We report the sequences of two West Nile virus (WNV) strains (lineages 1 and 2) developed by the Paul-Ehrlich-Institut as reference materials. The materials are calibrated against the 1st World Health Organization WNV RNA International Standard and are intended for use in nucleic acid technology assays supporting transfusion safety.

Reliable quantification of plasma HDV RNA is of paramount importance for treatment monitoring: A European multicenter study.

OBJECTIVES: Quantification of plasma hepatitis D virus (HDV) RNA is the essential tool for patient management under antiviral therapy. The aim of this European multicenter study was to improve the comparability of quantitative results reported by different laboratories using the CE/IVD-labeled RoboGene HDV RNA Quantification Kit 2.0 (Roboscreen GmbH) with different manual or automated nucleic acid extraction protocols/platforms and amplification/detection devices. METHODS: For harmonization of HDV RNA concentrations obtained by different protocols, correction factors (CF) were determined using the 1st WHO International Standard for HDV RNA. The limit of detection (LOD) and accuracy were determined for each protocol by using reference material. Furthermore, clinical samples were analyzed and results compared. RESULTS: The CF ranged from 20 to 1,870 depending on the protocol used. The LOD was found between 4 and 450 IU/ml. When accuracy was tested, external quality control (EQC) samples containing low HDV RNA concentrations were not detected by those protocols with higher LODs. For EQC samples, the maximum standard deviation of HDV RNA concentrations was found to be 0.53 log10 IU/ml, for clinical samples 0.87 log10 IU/mL. CONCLUSION: To ensure reliability in quantification of HDV RNA, any modification of the extraction and amplification/detection protocol validated by the manufacturer requires revalidation. With the 1st WHO International Standard for HDV RNA, the CF could easily be calculated leading to harmonization of quantitative results. This warrants both accurate monitoring of response to existing anti-HDV treatment and comparability of study results investigating novel anti-HDV drugs.

Detection of hepatitis C virus and parvovirus B19 in human plasma pools by nucleic-acid amplification techniques - Trends in results of EDQM proficiency testing studies from 2004 to 2018.

The European Directorate for the Quality of Medicines & HealthCare (EDQM) has run proficiency testing schemes on the detection of viral contaminants in human plasma pools by nucleic-acid amplification techniques since 1999 for hepatitis C virus and since 2004 for parvovirus B19. A retrospective analysis was performed to assess their impact and identify trends and progress in the results obtained by participating laboratories over a 15-year span, from 2004 to 2018. The results demonstrate that overall performance improved over that time, especially among the regular participants. Participation in these proficiency testing schemes is therefore recommended for all interested control laboratories. This analysis also shows that hepatitis C virus detection now seems well established compared to that of parvovirus B19, which still appears more challenging.

Immunoreactivity pattern of monoclonal antibodies against Hepatitis B vaccine with global Hepatitis B virus genotypes.

Hepatitis B surface antigen (HBsAg) specific monoclonal antibodies (mAbs) are potentially valuable therapeutic and diagnostic tool. We have previously established and characterized a panel of mAbs derived from immunized BALB/c mice with a yeast-derived recombinant HB vaccine subgentoype A2 and HBsAg subtype adw2. This study was conducted to evaluate the reactivity pattern of this anti-HBs mAbs panel with various genotypes and subgenotypes of HBV using the first WHO HBV genotype reference panel containing 15 serum samples representing the subgenotypes A1, A2, B1, B2, C2, D1-D3, E, F2, and H. Ten out of 21 anti-HBs mAbs were able to strongly recognize all gentopye/subtypes of HBsAg provided in the WHO reference panel. However, 10 out of 21 anti-HBs mAbs showed a moderate to profound loss of reactivity with HBV genotypes/HBsAg subtypes D2/ayw3, E/ayw4, F2/adw4, and H/adw4. Two mAbs from the second group displayed a profoundly reduced reactivity with only 1 out of 3 C2/adr genotype/subtype samples. The amino acid alignment of these 3 samples showed that this particular sample contains amino acid substitution at residue 127, which is located inside "a" determinant. This amino acid substitution, which profoundly affected the reactivity of anti-HBs antibodies, has been previously reported only in D/ayw3, E/ayw4, F/adw4, and H. Interestingly, the amino acid alignment of the samples in this WHO panel showed that P127T substitution can also be found in C2/adr. Comparing amino acids sequences inside the antigenic loop (AGL) showed that D2/ayw3 contains a T118A/P127T double substitution, E/ayw4 contains P127L/T140S, F2/adw4 contains P127L/T140S/ F158L, and H/adw4 contains P127L substitution. Therefore, amino acid variability at positions 118, 127, 140, and 158 was found to cause significant loss of reactivity with anti-HBs mAbs. Since HBsAg variability in different genotypes of HBV can profoundly affect the reactivity of anti-HBs mAbs, analytical sensitivity for HBsAg assays should be considered based on the circulating and common HBV variants in the relevant countries.

Detection of hepatitis B virus infection in German blood donors 2008-2015.

BACKGROUND AND OBJECTIVES: Assessment of HBV-NAT testing compared to HBsAg and anti-HBc screening in German blood establishments for the period 2008-2015. MATERIALS AND METHODS: Blood donations screened for HBsAg and anti-HBc along with HBV-NAT were evaluated. Sensitivity of HBsAg and HBV-NAT tests was compared in 30 HBV seroconversion panels and with the viral load of the NAT-only cases. Residual risk for HBV in the WP was modelled. RESULTS: A total of 45 270 111 donations were evaluated. There were 29 NAT-only cases in the HBsAg-negative HBV-WP, one by ID-NAT and 28 by MP-NAT. MP-NAT, on average, showed higher sensitivity than HBsAg testing: MP-NAT-LoD of 146 IU/ml vs. 362 IU/ml HBV DNA for positive HBsAg detection (range 135-1502 IU/ml), resulting in 3·1 days (range 2·0-4·8 days) earlier HBV detection. Viral loads of the NAT-only cases confirmed the sensitivity of the HBV tests in the seroconversion study. One HBsAg-negative case was due to a new HBsAg mutant combination. There was one HBsAg-reactive only case. In addition, HBV incidence in the HBV-WP included 41 HBsAg-/HBV-NAT-positives and three HBV transmission cases. The residual risk for HBsAg was estimated to be 1:1 619 419-1 268 474 compared to 1:2 793 365-2 134 702 for MP-NAT. Within chronic HBV (HBsAg-/anti-HBc-positive and MP-NAT-negative) 70% were ID-NAT positive at low viral load (median 20 IU/ml). Among anti-HBc-only, supplementary ID-NAT detected 23 occult HBV infections. CONCLUSIONS: In the HBV-WP, MP-NAT provided a higher sensitivity than HBsAg testing, obtained a considerably higher yield and reduced the risk for HBV transmission. In later HBV stages, anti-HBc screening and HBV-ID-NAT intercepted potentially infectious donations.

Prevalence of antibodies against Hepatitis D virus (HDV) in blood donors in Northern Germany.

OBJECTIVE: To assess the prevalence of HDV infections in German blood donors. METHOD: 167 donors with acute/chronic or resolved HBV infection and detectable antibodies against Hepatitis B core antigen (anti-HBc) were tested for antibodies against HDV (anti-HDV) by competitive ELISA. Samples with detectable anti-HDV or with HBsAg and/or HBV DNA were additionally investigated for HDV RNA. RESULTS: In nine (5.4 %) of the 167 donors, also HBsAg and HBV DNA were detectable. Anti-HDV was detectable in two of the 167 donors (1.2 %), additional four donors (2.4 %) had a borderline result. All of these donors tested negative for HBsAg and HBV DNA. Neither in samples with anti-HDV nor in HBsAg-/HBV DNA-positive samples, HDV RNA was detectable. CONCLUSIONS: At least 1.2 % of anti-HBc-positive blood donors have had an HDV infection. Although there is some evidence for a somewhat higher prevalence of HDV, the overall prevalence of HDV in Northern Germany is low.

Effectiveness of blood donor screening by HIV, HCV, HBV-NAT assays, as well as HBsAg and anti-HBc immunoassays in Germany (2008-2015).

BACKGROUND AND OBJECTIVES: In Germany, in addition to standard blood donor screening, further mandatory tests were introduced for HCV-RNA, HIV-1-RNA and for anti-HBc. Screening for HBV-DNA is optional. This study investigates the benefits of these additional tests for the detection of HIV, HCV, and HBV infections among German blood donors. MATERIALS AND METHODS: From 2008 to 2015 we collected data on blood donations exclusively testing NAT positive (NAT yield) or reactive in only one of the screening assays. Assuming a Poisson distribution, we calculated NAT yield/reactive only rates on a per donation basis (number of yield/reactive only cases divided by the number of donations tested in the period under review) with 95% confidence intervals. RESULTS: Responding establishments covered 95% of the donations. We identified 20 HIV-1-NAT, 61 HCV-NAT and 29 HBV-NAT yield cases among approximately 46 million blood donations tested corresponding to 0·43 HIV-1 NAT, 1·32 HCV-NAT, and 0·64 HBV-NAT yield cases per million blood donations tested. For one HBsAg reactive only case and 23 anti-HBc reactive only cases in repeat donors, infection was confirmed by ID-NAT which translates into 0·02 and 0·55 cases per million donations tested. During the 8-year-observation period, one HIV-1, no HCV and four HBV transmissions associated with donations in the viremic pre-seroconversion window period were reported. CONCLUSION: Annually, NAT screening alone detected 2·5 HIV-1, 7·6 HCV, and 3·6 HBV infectious donations; anti-HBc screening alone identified 2·9 infectious donations of repeat donors with occult HBV infection. Overall, the survey results support that the currently practiced donor HIV/HCV/HBV screening strategy in Germany does ensure a high standard of blood safety.

Impact of hepatitis E virus testing on the safety of blood components in Germany - results of a simulation study.

Hepatitis E virus (HEV) infections may be acquired through transfusion of blood components. As transfusion-transmitted infections mostly affect vulnerable individuals, measures to ensure the supply of safe blood components are under discussion. On the basis of the epidemiological situation in Germany, different testing strategy scenarios were investigated through simulation studies. Testing for HEV RNA by nucleic acid amplification technique (NAT) assays with a pool size of 96, and a 95% LoD of 20 IU/ml will result in an 80% reduction in expected HEV transmissions as well as of consequent chronic infections with subsequent severe complications.

Human immunodeficiency virus 1 dual-target nucleic acid technology improves blood safety: 5 years of experience of the German Red Cross blood donor service Baden-Württemberg-Hessen.

BACKGROUND: RNA viruses are associated with a high frequency of mutations because of the missing proofreading function of polymerases, such as reverse transcriptase. Between 2007 and 2010, six blood donations with false-negative nucleic acid technology (NAT) results were reported in Germany. Therefore, NAT screening in two viral genome regions was introduced by our blood donation service in 2010 on a voluntary basis and became mandatory in Germany since the beginning of 2015. STUDY DESIGN AND METHODS: Blood donor screening was done using, in parallel, the German Red Cross (GRC) HIV-1 CE long terminate repeats (LTR) PCR kit and the GRC HIV-1 gag CE PCR kit. In total, 7 million blood donations were screened during the study period from 2010 to 2014 with the GRC dual-target human immunodeficiency virus 1 (HIV-1) NAT system. Additionally, three suspicious specimens were analyzed by four monotargeted NAT assays and by five dual-target NAT assays. RESULTS: Three of 7 million donations tested negative using the 5'LTR-polymerase chain reaction, but they were positive if amplification was performed in the gag region. HIV antibodies were detected in all three donations. Nucleic acid sequence analysis identified a deletion of 22 bases within the 5'LTR probe binding region. Three different ltr-based monotargeted assays missed two donations, except for a low-reactive result obtained by one of the assays. In total, the detection rates for HIV-1-positive donations were 37.5% (3/8) for monotargeted assays and 100% (10/10) for dual-target assays. CONCLUSION: The current data demonstrate that dual-target NAT systems reduce the risk of false-negative HIV-1 NAT screening results.

Construction of a hepatitis B virus neutralizing chimeric monoclonal antibody recognizing escape mutants of the viral surface antigen (HBsAg).

Hepatitis B virus (HBV) infection is a global burden on the health-care system and is considered as the tenth leading cause of death in the world. Over 248 million patients are currently suffering from chronic HBV infection worldwide and annual mortality rate of this infection is 686000. The "a" determinant is a hydrophilic region present in all antigenic subtypes of hepatitis B surface antigen (HBsAg), and antibodies against this region can neutralize the virus and are protective against all subtypes. We have recently generated a murine anti-HBs monoclonal antibody (4G4), which can neutralize HBV infection in HepaRG cells and recognize most of the escape mutant forms of HBsAg. Here, we describe the production and characterization of the chimeric human-murine antibody 4G4 (c-4G4). Variable region genes of heavy and light chains of the m-4G4 were cloned and fused to constant regions of human kappa and IgG1 by splice overlap extension (SOE) PCR. The chimeric antibody was expressed in Chinese Hamster Ovary (CHO)-K1 cells and purified from culture supernatant. Competition ELISA proved that both antibodies bind the same epitope within HBsAg. Antigen-binding studies using ELISA and Western blot showed that c-4G4 has retained the affinity and specificity of the parental murine antibody, and displayed a similar pattern of reactivity to 13 escape mutant forms of HBsAg. Both, the parental and c-4G4 showed a comparably high HBV neutralization capacity in cell culture even at the lowest concentration (0.6µg/ml). Due to the ability of c-4G4 to recognize most of the sub-genotypes and escape mutants of HBsAg, this antibody either alone or in combination with other anti-HBs antibodies could be considered as a potent alternative for Hepatitis B immune globulin (HBIG) as an HBV infection prophylactic or for passive immunotherapy against HBV infection.

Blood donor screening for West Nile virus (WNV) revealed acute Usutu virus (USUV) infection, Germany, September 2016.

Between 1 June and 31 December 2016, 13,023 blood donations from the University Hospital Aachen in Germany were routinely screened for West Nile virus (WNV) RNA using the cobas TaqScreen WNV Test. On 28 September 2016, one blood donor was tested positive. Subsequent analysis revealed an acute Usutu virus (USUV) infection. During the ongoing USUV epizootics in Germany, blood transfusion services, public health authorities and clinicians should be aware of increased human USUV infections.

Comparative characterization of hepatitis B virus surface antigen derived from different hepatitis B virus genotypes.

For human hepatitis B virus eight distinct and two candidate genotypes are described. These genotypes differ with respect to geographic distribution, molecular virology and virus-associated pathogenesis. Comparative analysis of HBV genotypes revealed, with exception of HBV/G that shows impaired HBsAg release, that no fundamental disparities between genotypes exist regarding glycosylation, subcellular distribution, release of HBsAg and formation of subviral particles. However, there are distinctions regarding the proportion of L to M to S HBs proteins detected intra- and extracellularly for different genotypes. 2D electrophoresis revealed different posttranslational modification patterns for LHBs. In light of the relevance of HBsAg as diagnostic marker, detectability of purified recombinant HBsAg of various genotypes by HBsAg-specific detection systems licensed in Europe was investigated, showing similar sensitivities for genotypes included in this analysis. These data indicate that recombinant HBsAg reproducibly purified following a defined protocol might be used as an alternative to reference materials currently established.

International collaborative study on the 3rd WHO International Standard for hepatitis B surface antigen.

BACKGROUND: The WHO International Standard (IS) for hepatitis B surface antigen (HBsAg) is used to standardize HBsAg assays. Stocks of the 2nd IS for HBsAg are depleted. The proposal to establish its replacement was endorsed by WHO in 2012. OBJECTIVE: Preparation of a freeze-dried candidate 3rd IS (NIBSC 12/226); evaluation of its suitability in a WHO international collaborative study; calibration of its potency in International Units (IU). STUDY DESIGN: The 3rd IS is based on plasma-derived, purified, inactivated HBsAg from Vietnam. Qualitative and quantitative HBsAg assays were used to evaluate 12/226 alongside the 2nd IS and 1st IS. Blinded study samples included a duplicate of 12/226, a negative control and two diluted plasma samples representing hepatitis B virus (HBV) genotypes A and B. RESULTS: Twelve laboratories from 9 countries returned 22 data sets from 15 methods. The overall geometric mean potency of 12/226 is 47.3IU/mL (±13% CV) when compared to the 2nd IS with HBV subgenotype A2. The 3rd IS has HBV subgenotype B4 with a heterogeneous HBsAg subtype population of ayw1 and adw2. Some genotype-dependent effects on the inter-laboratory variability were observed but overall mean potencies were virtually identical irrespective of the IS used for calibration. Stability studies indicate that the candidate is stable for long-term use. CONCLUSIONS: 12/226 was established in October 2014 by the WHO Expert Committee on Biological Standardization as the 3rd IS for HBsAg with a potency of 47.3IU per ampoule maintaining the continuity in the standardization of HBsAg assays.

Standardization of NAT for Blood-Borne Pathogens.

Assays based on nucleic acid amplification technology (NAT) are increasingly used for screening of blood and for diagnosis or monitoring of patients. Both regulatory requirements for blood screening and international recommendations for the treatment of patients are based on common reference materials available globally for the standardization of NAT assays. World Health Organization International Standards (WHO ISs) and International Reference Panels (WHO IRPs) are primary reference materials. The characterization and manufacture of WHO reference materials as well as their evaluation is performed on behalf of the WHO by collaborating centers; their establishment is decided upon by the WHO Expert Committee on Biological Standardization (ECBS). The potency of the first WHO IS is defined by the 'international unit' (IU) which should be maintained upon replacement of the IS. The IU, unlike copy number or genome equivalent, is defined by the IS with a physical existence, is available worldwide, and allows traceability and comparability of results. The anticipated use of WHO ISs is the calibration of secondary standards or the validation of essential assay features, e.g. limit of detection.

World Health Organization International Standard To Harmonize Assays for Detection of Mycoplasma DNA.

Nucleic acid amplification technique (NAT)-based assays (referred to here as NAT assays) are increasingly used as an alternative to culture-based approaches for the detection of mycoplasma contamination of cell cultures. Assay features, like the limit of detection or quantification, vary widely between different mycoplasma NAT assays. Biological reference materials may be useful for harmonization of mycoplasma NAT assays. An international feasibility study included lyophilized preparations of four distantly related mycoplasma species (Acholeplasma laidlawii, Mycoplasma fermentans, M. orale, M. pneumoniae) at different concentrations which were analyzed by 21 laboratories using 26 NAT assays with a qualitative, semiquantitative, or quantitative design. An M. fermentans preparation was shown to decrease the interassay variation when used as a common reference material. The preparation was remanufactured and characterized in a comparability study, and its potency (in NAT-detectable units) across different NATs was determined. The World Health Organization (WHO) Expert Committee on Biological Standardization (ECBS) established this preparation to be the "1st World Health Organization international standard for mycoplasma DNA for nucleic acid amplification technique-based assays designed for generic mycoplasma detection" (WHO Tech Rep Ser 987:42, 2014) with a potency of 200,000 IU/ml. This WHO international standard is now available as a reference preparation for characterization of NAT assays, e.g., for determination of analytic sensitivity, for calibration of quantitative assays in a common unitage, and for defining regulatory requirements in the field of mycoplasma testing.

Intracellular accumulation of subviral HBsAg particles and diminished Nrf2 activation in HBV genotype G expressing cells lead to an increased ROI level.

BACKGROUND & AIMS: Hepatitis B virus genotype G (HBV/G) is characterized by a lack of HBeAg secretion and very low HBsAg secretion. This study aimed at (1) comparing HBV genotype G and A2 with respect to morphogenesis and release of HBV-derived particles, (2) characterizing factors contributing to HBV/G-associated pathogenesis. METHODS: HBV/G- and HBV/A-expressing hepatoma cells and infected HepaRG cells were analyzed by confocal laser scanning microscopy, Western blot, real-time PCR, density gradient centrifugation, and electron microscopy. Modulation of the transcription factors Nrf2 and AP-1 was analyzed. RESULTS: While the release of viral particles is not affected in HBV/G replicating cells, the secretion of subviral particles is impaired, although they are produced in high amounts. These subviral particles, which display an increased density and a predominantly filamentous morphology, accumulate at the endoplasmic reticulum. The PreS1PreS2 domain of genotype G, which forms aggregates, causes the block of HBsAg-secretion at the ER and leads to decreased transcriptional activator function of LHBs. Intracellular accumulation of HBsAg and impaired induction of the cytoprotective transcription factor Nrf2 lead to an elevated level of ROIs. This results in activation of JNK and as a consequence in Ser-phosphorylation of IRS-1, which is known to impair insulin signaling, a key factor for liver regeneration. CONCLUSIONS: Although competent for release of viral particles, secretion of subviral particles is impaired in HBV/G expressing cells leading to ER-stress. In parallel, HBV-induced Nrf2 activation diminishes, which causes a decrease of the capacity to inactivate ROIs. This might be related to genotype-specific pathogenesis.

Risk Minimization Measures for Blood Screening HIV-1 Nucleic Acid Amplification Technique Assays in Germany.

BACKGROUND: Several publications describe HIV-1 RNA false-negative results or viral load underquantitation associated with Communauté Européenne(CE)-marked qualitative or quantitative nucleic acid amplification technique (NAT) assays. 6 cases occurred during blood screening in Germany, with 2 of them causing HIV-1 transmissions to recipients of blood components. The implicated NAT assays were mono-target assays amplifying in different viral genome regions (gag or long terminal repeat). METHODS: Specimens characterized by HIV-1 NAT underquantitation or false-negative NAT results were comparatively investigated in CE-marked HIV-1 NAT systems of different design to identify potential reasons. The target regions of the viral nucleic acids were sequenced and these sequences compared to primers and probes of the assays. Potential risk minimization measures were considered for quantitative and blood-screening HIV-1 NAT systems. RESULTS: Nucleotide sequencing of the viral target region in cases of HIV-1 RNA underquantitation or false-negative test results revealed new HIV-1 variants that were mismatched with primers and probes used in some mono-target assays. So far, dualtarget NAT assays have not been associated with mismatch-based false-negative test results. From 2015, the Paul Ehrlich Institute will request HIV-1 NAT assays of dual-target design or an analogous solution for further reducing the risk in blood screening. CONCLUSION: HIV differs from other blood-borne viruses with regard to its fast evolution of new viral variants. The evolution of new sequences is hardly predictable; therefore, NAT assays with only 1 target region appear to be more vulnerable to sequence variations than dual-target assays. The associated risk may be higher for HIV-1 NAT assays used for blood screening compared to quantitative assays used for monitoring HIV-1-infected patients. In HIV-1 screening NAT assays of dual-target design may adequately address the risk imposed by new HIV-1 variants.

Infectivity of blood products from donors with occult hepatitis B virus infection.

BACKGROUND: Occult hepatitis B virus (HBV) infection (OBI) is identified in 1:1000 to 1:50,000 European blood donations. This study intended to determine the infectivity of blood products from OBI donors. STUDY DESIGN AND METHODS: Recipients of previous donations from OBI donors were investigated through lookback (systematic retrieval of recipients) or traceback (triggered by clinical cases). Serologic and genomic studies were undertaken on consenting donors and recipients. Multiple variables potentially affecting infectivity were examined. RESULTS: A total of 45 of 105 (42.9%) donor-recipients pairs carried antibodies to HBV core (anti-HBc) as evidence of previous HBV infection. Subtracting 15% of anti-HBc population background, the adjusted transmission rate was 28%. Anti-HBc prevalence increased to 28 of 44 (63.8%) in unvaccinated recipients receiving anti-HBs-negative OBI blood products. In contrast, four of 26 (15.4%) recipients of anti-HBs-positive products were anti-HBc positive. Transmission with anti-HBs-negative products depended on volume of plasma transfused (85%-100% with 200 mL of fresh frozen plasma [FFP], 51% with 50 mL in platelet concentrates [PCs], and 24% with 20 mL in red blood cells [RBCs], p < 0.0001 FFP vs. RBCs). The 50% minimum infectious dose of OBI HBV DNA was estimated at 1049 (117-3441) copies. Donor and recipient strains sequence homology of at least 99% confirmed transfusion-transmitted infection in 10 cases and excluded it in one case. CONCLUSION: Blood products from donors with OBI carry a high risk of HBV transmission by transfusion. This risk is dependent on presence of anti-HBs and viral dose. This may justify safety measures such as anti-HBc and HBV nucleic acid test screening depending on epidemiology.