A mathematical model for estimating residual transmission risk of occult hepatitis B virus infection with different blood safety scenarios

Biomarkers of transfusion transmitted occult hepatitis B virus infection: Where are we and what next?

Blood transfusion is a vital procedure, where transfusion-transmitted infection of hepatitis B virus (HBV) remains an important issue, especially from blood donors with occult hepatitis B virus infection (OBI). Occult hepatitis B virus infection is a complex entity to detect using surrogate blood biomarkers for intrahepatic viral transcriptional activity, requiring a continually refined battery of tests utilised for screening. This review aims to critically evaluate the latest advances in the current blood biomarkers to guide the identification of OBI donors and discuss novel HBV markers that could be introduced in future diagnostic practice. Challenges in detecting low HBV surface antigen levels, mutants, and complexes necessitate ultrasensitive multivalent dissociation assays, whilst HBV DNA testing requires improved sensitivity but worsens inaccessibility. Anti-core antibody assays defer almost all potentially infectious donations but have low specificity, and titres of anti-surface antibodies that prevent infectivity are poorly defined with suboptimal sensitivity. The challenges associated with these traditional blood HBV markers create an urgent need for alternative biomarkers that would help us better understand the OBI. Emerging viral biomarkers, such as pre-genomic RNA and HBV core-related antigen, immunological HBV biomarkers of T-cell reactivity and cytokine levels, and host biomarkers of microRNA and human leucocyte antigen molecules, present potential advances to gauge intrahepatic activity more accurately. Further studies on these markers may uncover an optimal diagnostic algorithm for OBI using quantification of various novel and traditional blood HBV markers. Addressing critical knowledge gaps identified in this review would decrease the residual risk of transfusion-transmitted HBV infection without compromising the sustainability of blood supplies.

Systematic review of prevalence and risk factors of transfusion transmissible infections among blood donors, and blood safety improvements in Southern Africa

Blood and blood products are listed as one of the essential medicines by the World Health Organization (WHO). In addition to inadequate supply, most sub-Saharan Africa (SSA) nations fail to meet their blood needs because many donated blood units are discarded because they are contaminated with transfusion-transmitted infections (TTIs). We sought to estimate the prevalence of TTIs, identify the risk factors for TTIs among blood donors, and identify the efforts and interventions that have been made to improve blood safety in Southern African nations, particularly the nations of the South African Development Community (SADC). We investigated the prevalence and risk factors for TTIs, blood safety interventions, and blood quality improvement in the SADC region from major PubMed/MEDLINE, Cochrane Library, and HINARI databases from 1 January 2011 to 31 April 2021. All investigations followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). In meta-analysis, we estimated the pooled TTIs prevalence and summarised the same using forest plots. A total of 180 articles published from the SSA region were identified covering our three targeted themes: TTI prevalence, risk factors for TTIs, and blood safety improvements. Of these 180 articles, only 27 (15%) focused on the SADC region. The overall pooled TTI prevalence estimate was 2.0% (95% CI: 1.0-3.0) and hepatitis B was the most prevalent TTI in the region (prevalence = 3.0; 95% CI: 2.0-5.0). The prevalence of HIV, HCV, and syphilis was 2.0% (95% CI: 1.0-4.0), 1.0% (95% CI: 0.0-2.0), and 2.0% (95% CI: 0.0-8.0), respectively. In general, replacement donors and first-time donors were more likely to be infected with TTIs than repeat donors. Twelve articles explored blood safety research in the region; however, they vary greatly highlighting the need for consistent and more comprehensive research. Few publications were identified that were from the SADC region, indicating lack of research or resources towards improving both quantity and quality of blood donation. TTI prevalence remains one of the highest in the world and blood safety recommendations vary across the region. More effort should be directed towards developing a cohesive regional blood transfusion policy and effective blood monitoring and evaluation strategies.

Efficacy of Different Testing Scenarios in Reducing Transfusion-Transmitted Hepatitis B Virus (TT-HBV) Infection Risk

The efficacy of different screening scenarios in reducing hepatitis B virus (HBV) transmission risk as compared to the risk without screening was modeled in 9,337,110 donations from four geographical regions that had been subjected to hepatitis B surface antigen (HBsAg) and individual donation nucleic acid amplification testing (ID-NAT). We used the Weusten models for estimating infectivity risk for Red Blood Cell (RBC) transfusions in eight HBV infection stages and then evaluated multiple screening strategies based on minipool (MP) and ID-NAT options of different sensitivity for their efficacy in reducing this risk. The efficacy in reducing HBV transmission risk by screening scenarios across the regions varied between 81% (HBsAg only) and 99.2% (ID-NAT and anti-HBc). Highly sensitive ID-NAT alone achieved a slightly higher risk reduction (97.6−99.0%) than minipool of 6 donations (MP6)-NAT in combination with HBsAg and anti-HBc (96.3−98.7%). In ID-NAT screened lapsed and repeat donors, the additional risk removed by HBsAg testing was minimal (<0.1%). The modeling outcomes in this and two previous reports using this multi-regional database suggest that one could consider an ID-NAT alone testing scenario as an alternative to MP-NAT and serology-based testing algorithms and restrict serologic testing to first-time donors only.

Prevalence of Occult Hepatitis B Virus Infection in Blood Donors with Negative ID-NAT in Switzerland

Introduction

Screening of hepatitis B surface antigen (HBsAg) and individual-donation nucleic acid amplification testing (ID-NAT) of blood donors have become standard to detect hepatitis B virus (HBV) infection. However, there is still a residual risk of HBV transmission by blood components of donors suffering from occult HBV infection (OBI). Therefore, many countries implemented universal testing of anti-HBV core antigen (anti-HBc) antibodies in order to increase blood safety. In Switzerland, anti-HBc testing is not part of the routine blood donor-screening repertoire. Therefore, we sought to assess prevalence of donors with OBI in a Swiss blood donor collective.

Methods

Blood donations were prospectively investigated for the presence of anti-HBc antibodies during two time periods (I: all donors, March 2017; II: first-time donors only, April 2017 until February 2018). Anti-HBc-positive findings were confirmed by an anti-HBc neutralization test. Discarded plasma samples of anti-HBc-confirmed positive donors were ultracentrifuged and subsequently retested by regular HBV-ID-NAT to search for traces of HBV.

Results

During time period I, 78 (1.6%) individuals out of 4,923 donors were confirmed anti-HBc-positive. Sixty-nine (88%) anti-HBc-positive samples were available and processed by ultracentrifugation followed by repeat HBV-ID-NAT. Four samples (5.8%) were found positive for HBV DNA. Sixty-five (94.2%) samples remained HBV NAT-negative upon ultracentrifugation. During time period II, 56 (0.9%) donor samples out of 6,509 exhibited anti-HBc-confirmed positive. Fifty-five (98%) samples could be reassessed by HBV-ID-NAT upon ultracentrifugation. Three (5.5%) samples contained HBV DNA and 52 (94.5%) samples remained HBV NAT-negative.

Conclusion

Overall, we detected 7 viremic OBI carriers among 11,432 blood donors, which tested negative for HBV by standard HBV-ID-NAT and HBsAg screening. In contrast, OBI carriers showed positive anti-HBc findings which could be confirmed in 83.8% of the cases. Thus, OBI might be missed by the current HBV screening process of Swiss blood donors. We suggest to review current HBV screening algorithm. Extended donor screening by anti-HBc testing may unmask OBI carriers and contribute to blood safety for the recipient of blood products.

Infectivity of hepatitis B virus (HBV) surface antigen (HBsAg) positive plasma with undetectable HBV-DNA: Can HBsAg screening be discontinued in Egyptian blood donors?

HBV infectivity data were reviewed and the 50% infectious dose (ID50 ) was reassessed in different HBsAg positive infection stages enabling modelling of transfusion-transmitted (TT)-HBV infection risk if HBsAg donor screening was replaced by individual donation nucleic acid amplification technology (ID-NAT). Quantitative HBsAg and HBV-DNA assays were performed against international standards to compare the ratio between potential infectious HBV virions and subviral HBsAg particles in Egyptian HBsAg positive blood donors as well as in Japanese chimpanzee samples of known infectivity. HBV-DNA load below the quantification limit of detection was estimated against a reference standard by replicate NAT testing (n = 25). Infectivity of chimpanzee samples collected during ramp-up and declining viremic phase were tested in a human liver chimeric mice (HLCM) model and compared with published infectivity data from different HBsAg positive infection stages. Lowest estimates of ID50 in HBsAg positive plasma were 3-6 HBV virions in chimpanzee studies. Infectivity decreased approximately 10-100-fold in the declining viremic phase using HLCM. In acute-phase samples, HBV to HBsAg particle ratios varied between 1:102 -104 but in HBsAg positive blood donors this particle ratio reached 1:106 -1012 when viral load was below 100 HBV-DNA copies/ml. Modelled TT-HBV risk of an HBsAg positive/ID-NAT nonreactive blood transfusion was estimated at 9%-46% for components containing 20-200 ml of plasma assuming an ID50 of 316 (point estimate between 100 and 1000) virions. In the Egyptian setting, discontinuation of HBsAg donor screening and reliance on ID-NAT alone seems to be unsafe.

Occult Hepatitis B virus (HBV) infection and challenges for hepatitis elimination: A literature review

Occult hepatitis B infection (OBI) is characterized by the detection of hepatitis B virus (HBV) DNA in serum or liver but negativity for hepatitis B surface antigen. OBI, which is thought to be maintained by host, immunological, viral and/or epigenetic factors, is one of the most challenging clinical features in the study of viral hepatitis. Currently, there is no validated detection test for OBI. It is believed that OBI is widely distributed throughout the world, with a higher prevalence in populations at high-risk HBV, but the detailed worldwide prevalence patterns are unknown. We conducted a survey of recently published studies on OBI rates across all continents. High prevalence rates of OBI are observed in some specific groups, including patients with hepatitis C virus, human immunodeficiency virus co-infection or hepatocellular carcinoma. In 2016, the World Health Organization adopted strategies to eliminate viral hepatitis by 2030, but the difficulties in detecting and treating OBI currently challenge this goal. Subjects with OBI can transmit HBV, and episodes of reactivation can occur. Further studies to understanding the mechanisms that drive the development of OBI are needed and can contribute to efforts at eliminating viral hepatitis.

Residual risk of transfusion-transmitted hepatitis B virus (TT-HBV) infection by NAT-screened blood components: A review of observed versus modeled infectivity from donors with window period and occult HBV infections

BACKGROUND

The residual transfusion-transmitted hepatitis B virus (TT-HBV) risk with different testing strategies depends on the sensitivity of screening assays, the prevalence of hepatitis B surface antigen (HBsAg) compared to HBV-DNA in window period (WP) and occult HBV infections (OBIs), and infectivity of blood in these infection stages. We compared modeled WP and OBI transmission risk in a multiregional individual donation nucleic acid amplification technology (ID-NAT) screening study with observed TT-HBV infection rates in several lookback studies.

STUDY DESIGN AND METHODS

The WP and OBI risk was estimated from ID-NAT screening data in six geographic regions. The 50% infectious dose (ID₅₀ ), a key factor in the applied risk models, was assumed to be 100-fold higher in OBI than in WP blood. The relative proportion of WP and OBI TT-risk was estimated for different screening scenarios and expressed as a percentage of the ID-NAT yield rate to allow for comparison with observed TT-rates in lookback studies.

RESULTS

Despite sevenfold to eightfold higher HBV ID-NAT yield rates in OBI than WP in South-East Asia and Europe, our models predicted that 40 (26-55)% of total residual TT-HBV risk was due to OBI, comparable to 37% observed in a Japanese hemovigilance study. Modeled TT-OBI risk was approximately 10-fold higher than observed rates of 2%-8% in five lookback studies but comparable to one other study (36%).

CONCLUSION

Although the observed TT-OBI rate was generally lower than the modeled risk, the relative risk of WP versus OBI transmission was not incompatible with the observational infectivity data. This supports the validity of our assumptions in the infectivity-based models for estimating worst-case residual risk with different testing scenarios.

An assessment of hepatitis B virus prevalence in South African young blood donors born after the implementation of the infant hepatitis B virus immunization program: Implications for transfusion safety

BACKGROUND

The prevalence of hepatitis B surface antigen is estimated to be 6.7% in the South African population and in April 1995 the nation introduced universal hepatitis B virus (HBV) vaccination for newborns and infants. We studied the temporal association of this program with HBV prevalence in young blood donors and the contemporary HBV incidence and residual risk of transfusion-transmitted HBV infection (TT-HBV).

METHODS

We used blood donation data from January 2011 to December 2019. Estimation of HBV prevalence donations made by first-time blood donors were analyzed by birth cohort and covariates. To estimate the incidence and residual risk of TT-HBV, mathematical models used data from both first time and repeat donors.

RESULTS

HBV prevalence in first-time donors decreased from 0.84% (95% confidence interval [CI] 0.78-0.90) in 2011 to 0.66% (95% CI 0.61-0.70) in 2019. The post-1995 birth cohort had a significantly lower HBV prevalence of 0.14% (95% CI 0.13-0.15) than the pre-1985 birth cohort of 1.29% (95% CI 1.25-1.33) and the odds of HBV infection were reduced in a multivariable model (odds ratio [OR] = 0.28, 95% CI 0.24-0.34). The residual risk of TT-HBV occurring from window-period, occult, and possible vaccine breakthrough infections were estimated at 36.9, 5.8, and 2.2 per million red blood cell transfusions, respectively.

CONCLUSION

Donors born after the start of routine HBV immunization had significantly lower prevalence of HBV infection, supporting the effectiveness of the vaccination program. The contemporary residual risk of TT-HBV has decreased and should decline further as more vaccinated young people join the donor pool.

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.

Hepatitis B infections among blood donors in England between 2009 and 2018: Is an occult hepatitis B infection a risk for blood safety?

INTRODUCTION

Hepatitis B virus (HBV) is one of the most frequent infections identified in blood donors in England and represents an ongoing blood safety risk. We have analyzed markers of HBV infections in blood donors in England between 2009 and 2018 and used these to estimate the likelihood of non-detection of occult HBV infection (OBI).

METHODS

We collected epidemiological, virological, and genotyping information on HBV cases identified in England, 2009-2018. The estimated risk of non-detection and likely transmission of OBI were compared to lookback and transfusion-transmitted infections surveillance data.

RESULTS

Six-hundered and fifty-five HBV-infected blood donors were identified in England during the 10-year period; 598 chronic, 32 acute, and 25 occult HBV infections. However, most donors with chronic and occult infections were born in Eastern Europe, Africa, or Asia (451/544, 83% and 14/24, 58%); acute infections were largely seen in UK-born donors (19/28, 68%). Genotyping of 266 HBV-positive samples revealed five genotypes (A-E), reflecting ethnicity and country of birth. Most OBIs were identified in repeat donors (19/25); lookback data identified a transmission rate of 8.3%. It is estimated that at least 13 potentially infectious donations from donors with OBI remain undetected annually, equating to an overall residual transmission risk of 3.1 per million donations using our current screening strategy of HBsAg screening with HBV nucleic acid testing (NAT) in pools of 24.

CONCLUSIONS

OBI accounted for the majority of the HBV residual risk in England. Further cost-benefit analysis is required to estimate if our current HBV screening strategy should be changed.

Challenges in transfusion-transmitted infection screening in Sub-Saharan Africa

In Sub-Saharan Africa, high clinical demand for transfusion faces endemic bloodborne infections and limited resources. Blood screening for transfusion-transmitted bloodborne pathogens is the cornerstone of blood safety. Although there have been substantial improvements over the years, challenges in transfusion-transmitted infection screening that have been identified repeatedly long ago still need to be addressed. Affordability and sustainability of state-of-the-art quality assessed serological and molecular assays, and associated confirmation strategies remain of real concern. In addition, limited resources and infrastructures hamper the development of adequate facilities, quality management, and staff qualification, and exacerbate shortage of reagents and equipment maintenance. It is also important to maintain effort in constituting pools of repeat voluntary non-remunerated donors. Alternative strategies for blood screening that take into account local circumstances might be desirable but they should rely on appropriate field evaluation and careful economic assessment rather than dogma established from high-resource settings.

Prevalence of occult HBV infection in Western countries

Due to a lack of standardized tests, it is difficult to obtain prevalence data and define the real impact of occult HBV infection (OBI) in Western countries. The present review article addresses the prevalence of OBI, defined as presence of hepatitis B virus (HBV) DNA in liver tissue or plasma in HBsAg-negative subjects, in Western countries. This varies in different studies according to the different methodologies used (based on serology vs virology), to the sample analyzed for the diagnosis (liver tissue vs plasma), to the different populations studied, to the different geographical variations in the HBV spread, to the host characteristics (age, gender, risk factors for acquiring HBV infection) and to the presence of other parenteral infections (hepatitis C virus and/or human immunodeficiency virus [HIV] infections). Considering the different liver diseases analyzed, that is in patients with cryptogenic cirrhosis or advanced liver fibrosis, the prevalence of OBI ranges 4% to 38%. Considering the different populations studied, in the case of parenteral blood exposure it is about 45%, in patients with chronic hepatitis C it is estimated at about 52%, in HIV-infected patients it ranges from 0% to 45%, in blood donors from 0% to 22.7% and in hemodialysis patients it ranges from 0% to 54%. In conclusion, OBI is a virological entity to be considered when performing the patient's evaluation for immunosuppressive diseases, liver pathologies, or for blood transfusions. Knowing the prevalence and clinical impact of OBI will allow better patient management.

Haemostatic function measured by thromboelastography and metabolic activity of platelets treated with riboflavin and UV light

BACKGROUND

Pathogen reduction technology (PRT) may damage platelet (PLT) components. To study this, metabolic activity and haemostatic function of buffy coat (BC) PLT concentrates, with or without riboflavin and UV light PRT treatment, were compared.

MATERIAL AND METHODS

Twenty-four BC PLT concentrates, leukoreduced and diluted in additive solution, were grouped into 12 type-matched pairs, which were pooled and divided into 12 non-PRT-treated BC PLT concentrates (control units) and 12 riboflavin and UV PRT-treated BC PLT concentrates (test units). Haemostatic function and metabolic parameters were monitored by thrombelastography at days 1, 3, 7 and 14 post collection in both PLT groups.

RESULTS

Loss of PLT discoid shape, glucose consumption, lactate production, and decrease in pH were greater in the PRT-treated PLTs than in control PLTs over time (p<0.001). PLT haemostatic function evaluated by clot strength was also significantly weaker in PRT-treated PLTs compared with the excellent clot quality of control PLTs at day 7 (maximum amplitude: 41.27 vs 64.27; p<0.001), and even at day 14 (21.16 vs 60.39; p<0.001) of storage.

DISCUSSION

Pathogen reduction technology treatment accelerates and increases platelet storage lesion, resulting in glucose depletion, lactate accumulation, PLT acidification, and discoid shape loss. The clots produced by control PLTs at day 14 were still remarkably strong, whereas at day 7 PRT-treated PLTs produced weaker clots compared to the control group. Clinical trials investigating the efficacy of PRT-treated PLTs transfused at the end of the storage period (day 7), when the in vitro clot strength is weaker, are needed.

Comprehensive analysis of hepatitis B virus infections in blood donors in southern China that are surface antigen positive but nucleic acid testing negative

BACKGROUND

Hepatitis B virus (HBV) infection is one of the major concerns for the safety of blood transfusion in high-prevalent countries such as in China. Prior studies outside of China have shown hepatitis B surface antigen (HBsAg) false-reactive rate of 0.02% to 0.04%. Similarly, false-negative HBsAg and HBV DNA results may occur in infected donors. Our study analyzed HBsAg enzyme-linked immunosorbent assay (ELISA)-reactive but NAT-negative donations in Shenzhen Blood Center, China.

STUDY DESIGN AND METHODS

HBsAg ELISA-positive/NAT-negative plasma samples identified from screening 101,025 donations during 2017-2018 were analyzed by molecular and serologic tests including neutralization, chemiluminescence immunoassays, and various HBV DNA amplification assays. Molecular characterizations of HBsAg-positive/NAT-negative samples were determined by quantitative polymerase chain reaction (qPCR) and nested PCR amplification of the basic core and precore promotor regions (295 base pairs) and HBsAg (S) region (496 base pairs).

RESULTS

Screening of 101,025 eligible blood donations identified 157 (0.16%, 95% confidence interval, 0.13%-0.18%) HBsAg ELISA-positive/NAT-negative plasma samples; of those, 71 (45.2%) were HBsAg confirmed positive by further HBsAg testing and DNA positive by molecular tests with increased sensitivity. Of the 71, all but one was antibody to hepatitis B core antigen reactive without antibody to hepatitis B surface antigen, yielding one recent (window-period) HBV infection. Of the remaining donations, 80 (51%) were not considered as HBV-infected donors, and 6 (3.8%) were interpreted as indeterminate since HBsAg results were discordant with unconfirmed HBV DNA results. In the 71 confirmed positives, HBsAg levels ranged from 0.05 to 400 IU/mL and HBV DNA from 6 to 2654 IU/mL; however, the correlation between the two was weak (R² = 0.24).

CONCLUSION

Fewer than half of HBsAg ELISA-positive/NAT-negative samples were confirmed as HBsAg positive. Our study demonstrates that in highly HBV-endemic countries, assays with high sensitivity and specificity may be required.

Viral safety of human platelet lysate for cell therapy and regenerative medicine: Moving forward, yes, but without forgetting the past

Growth factor-rich pooled human platelet lysate (HPL), made from human platelet concentrates, is one new blood-derived bioproduct that is attracting justified interest as a xeno-free supplement of growth media for human cell propagation for cell therapy. HPL can also find potentially relevant applications in the field of regenerative medicine. Therefore, the therapeutic applications of HPL go far beyond the standard clinical applications of the traditional blood products typically used in patients suffering from life-threatening congenital or acquired deficiencies in cellular components or proteins due to severe genetic diseases or trauma. A wider population of patients, suffering from various pathologies than has traditionally been the case, is thus, now susceptible to receiving a human blood-derived product. These patients would, therefore, be exposed to the possible, but avoidable, side effects of blood products, including transfusion-transmitted infections, most specifically virus transmissions. Unfortunately, not all manufacturers, suppliers, and users of HPL may have a strong background in the blood product industry. As such, they may not be fully aware of the various building blocks that should contribute to the viral safety of HPL as is already the case for any licensed blood products. The purpose of this manuscript is to reemphasize all the measures, including in regulatory aspects, capable of assuring that HPL exhibits a sufficient pathogen safety margin, especially when made from large pools of human platelet concentrates. It is vital to remember the past to avoid that the mistakes, which happened 30 to 40 years ago and led to the contamination of many blood recipients, be repeated due to negligence or ignorance of the facts.

The plasma supply in France

Contrary to economically comparable countries, France has had a versatile policy to process and manufacture therapeutic plasma, and to apply safety measures. This has principally affected the origin of plasma (whole blood supernatant versus apheresis), and the application or not of a chemical process. At the time being, the civilian and Army Forces blood establishments produce more than 99% of the plasma issued for patients in need; safety means consist in a large part of quarantine and, to a lesser extent, to a pathogen reduction technology process (Amotosalen-HCl-UVA). The blood establishments ship plasma to the national manufacturer of blood derivatives. Plasma in France is strictly within the Voluntary Non-Remunerated pathway with no breach to this principle to be expected for both labile components and source plasma. The constant hemovigilance allows reflection to make policies evolving, with respect to safety measures particularly to reduce cases of allergy.

High rate of occult hepatitis B virus infection in hemodialysis units of KwaZulu-Natal, South Africa

Occult hepatitis B virus (HBV) infection (OBI) is defined as the presence of HBV DNA in the liver with or without detectable HBV DNA in the serum of individuals testing HBV surface antigen (HBsAg) negative using currently available assays. The prevalence of OBI among patients receiving hemodialysis (HD) treatment remains poorly characterized in South Africa despite the high prevalence of HBV. We sought to determine the prevalence of OBI in HD units in tertiary hospitals of KwaZulu-Natal and to characterize the HBV S gene mutations potentially responsible for OBI. A cross-sectional descriptive study of residual diagnostic plasma samples from 85 HBsAg-negative patients receiving HD treatment was included. The PreS/S gene was amplified with a nested HBV polymerase chain reaction for downstream next-generation sequencing, to determine the viral genotype and identify S gene mutations associated with OBI. Nine of the 85 samples had OBI, based on detectable HBV DNA. The point prevalence of OBI was 10.6% (95% control interval: 5.5%-19.1%). Phylogenetic analysis of the samples with OBI showed that all belonged to genotype A. Three (~33%) samples had mutations in the major hydrophilic region (MHR) within the S gene, three (~33%) had mutations within the S gene but outside the MHR, whilst the remaining three had no mutations observed. The prevalence of OBI in HBsAg-negative patients undergoing HD was 10.6%, suggesting that OBI is a clinically significant problem in patients with HD in this region. The screening methods for HBV infection need to be revised to include nucleic acid testing.

Multiple HBV transfusion transmissions from undetected occult infections: revising the minimal infectious dose

OBJECTIVE

HBV infection by blood components is currently prevented in most developed countries by combining sensitive HBV surface antigen (HBsAg) assays, nucleic acid testing (NAT) and in a few of them antibodies against the HBV core antigen (anti-HBc) screening. HBV transmissions by blood components from three repeat donors tested negative for HBsAg and HBV DNA with a highly sensitive screening test (limit of detection (LOD): 3.4 IU/mL) were investigated.

DESIGN

30 of the 47 recipients of components produced from these three donors were examined. Transfusion transmission was confirmed by phylogenetic analysis of viral sequences obtained from recipients and donors following viral particle concentration.

RESULTS

9 of 31 (29%) recipients were infected: 7 infections were related to 200 mL of fresh frozen plasma and 2 infections to red blood cells containing 20 mL plasma. Transfusion transmission was confirmed by >99% identity of donor/recipient sequences in five cases, probable in three and possible in one. HBV active infection remained unsuspected for 24-57 months in three recipients. Five non-infected recipients carried anti-HBs when transfused. Six patients transfused with platelet concentrates treated with a pathogen reduction method were not infected. These data enabled to revise previous estimate of the minimal infectious dose from approximately 100 to 16 copies (or 3 IU) of HBV DNA.

CONCLUSIONS

HBV transfusion transmission from occult HBV infection carrying extremely low viral loads is related to plasma volume transfused and possibly prevented by anti-HBs. HBV blood safety could be further improved by either anti-HBc screening, HBV DNA NAT with a LOD of 0.8 copies/mL (0.15 IU/mL) or pathogen reduction of blood components.

Hepatitis B Virus Blood Screening: Need for Reappraisal of Blood Safety Measures?

Over the past decades, the risk of HBV transfusion–transmission has been steadily reduced through the recruitment of volunteer donors, the selection of donors based on risk-behavior evaluation, the development of increasingly more sensitive hepatitis B antigen (HBsAg) assays, the use of hepatitis B core antibody (anti-HBc) screening in some low-endemic countries, and the recent implementation of HBV nucleic acid testing (NAT). Despite this accumulation of blood safety measures, the desirable zero risk goal has yet to be achieved. The residual risk of HBV transfusion–transmission appears associated with the preseroconversion window period and occult HBV infection characterized by the absence of detectable HBsAg and extremely low levels of HBV DNA. Infected donations tested false-negative with serology and/or NAT still persist and derived blood components were shown to transmit the virus, although rarely. Questions regarding the apparent redundancy of some safety measures prompted debates on how to reduce the cost of HBV blood screening. In particular, accumulating data strongly suggests that HBsAg testing may add little, if any HBV risk reduction value when HBV NAT and anti-HBc screening also apply. Absence or minimal acceptable infectious risk needs to be assessed before considering discontinuing HBsAg. Nevertheless, HBsAg remains essential in high-endemic settings where anti-HBc testing cannot be implemented without compromising blood availability. HBV screening strategy should be decided according to local epidemiology, estimate of the infectious risk, and resources.

The current incidence, prevalence, and residual risk of hepatitis B viral infections among voluntary blood donors in China

BACKGROUND

There are few data available on the prevalence, incidence, and residual risk of transfusion-transmitted HBV (TT-HBV) infections among Chinese blood donors. This study investigated the demographic characteristics of blood donors, as well as the prevalence, incidence, and residual risk (RR) of TT-HBV infections in six large blood centers in different regions of China.

METHODS

The demographic characteristics and HBV screening test results of blood donors from six blood centers in different regions in China were collected and analyzed. The hepatitis B surface antigen (HBsAg) yield approach was used to estimate the incidence of HBV. Then, the RR of TT-HBV infections was evaluated using the incidence-window period model.

RESULTS

The majority of donors were between 18 and 35 years old (including 35), with the exception of the Changzhi Blood Center where a majority of donors were between 35 and 55 years old (including 55). The prevalences of HBV were 0.13%, 0.078%, 0.16%, 0.07%, 0.20%, 0.25% in Hefei, Dalian, Changzhi, Kaifeng, Mianyang and Fujian, respectively. The estimated corresponding incidences were 213.44, 161.59, 989.80, 278.05, 125.31 and 352.19 per 10⁵ person-years. Using an infectious window period of 59 days, the RR for HBV was estimated to be 34.14, 25.85, 158.35, 44.48, 20.04 and 56.35 per 10⁵ person-years in Hefei, Dalian, Changzhi, Kaifeng, Mianyang and Fujian, respectively.

CONCLUSION

Despite the introduction of more sensitive assays in blood screening, our data revealed that the current residual risk of TT-HBV infection was still high (overall 56.53 per 10⁵ py). A continuous monitoring of the residual risk of transfusion-transmitted infections is crucial for safe blood management.

Occult hepatitis B infection and transfusion-transmission risk

Advances in serology and viral nucleic acid testing (NAT) over the last decades significantly reduced the risk of transfusion-transmitted hepatitis B virus (HBV). The combination of HBsAg testing and NAT efficiently prevents the majority of HBV transmission. However, a specific residual risk remains associated with extremely low viral DNA levels in blood donors with occult HBV infection (OBI) that are intermittently or not detectable even by highly sensitive individual donation (ID) NAT. Studies have reported HBV transfusion-transmission with blood components from donors with OBI that contained low amount of viruses (<200 virions). HBV transfusion-transmission seems to depend on a combination of several factors including the volume of plasma associated with the infected blood components transfused, the anti-HBV immune status of both recipient and donor, and possibly the viral fitness of the infecting HBV strain. Models based on clinical and experimental evidences estimate a residual transmission risk of 3-14% associated with OBI donations testing HBsAg and ID-NAT non-reactive. Anti-HBc testing has the potential to improve further blood safety but it may also compromise blood availability in settings with medium/high HBV prevalence. Pathogen reduction procedures might be considered.