Do quantitative levels of antispike-IgG antibodies aid in predicting protection from SARS-CoV-2 infection? Results from a longitudinal study in a police cohort.

In a COVID-19 sero-surveillance cohort study with predominantly healthy and vaccinated individuals, the objectives were (i) to investigate longitudinally the factors associated with the quantitative dynamics of antispike (anti-S1) IgG antibody levels, (ii) to evaluate whether the levels were associated with protection from SARS-CoV-2 infection, and (iii) to assess whether the association was different in the pre-Omicron compared with the Omicron period. The QuantiVac Euroimmun ELISA test was used to quantify anti-S1 IgG levels. The entire study period (16 months), the 11-month pre-Omicron period and the cross-sectional analysis before the Omicron surge included 3219, 2310, and 895 reactive serum samples from 949, 919, and 895 individuals, respectively. Mixed-effect linear, mixed-effect time-to-event, and logistic regression models were used to achieve the objectives. Age and time since infection or vaccination were the only factors associated with a decline of anti-S1 IgG levels. Higher antibody levels were significantly associated with protection from SARS-CoV-2 infection (0.89, 95% confidence interval [CI] 0.82-0.97), and the association was higher during the time period when Omicron was predominantly circulating compared with the ones when Alpha and Delta variants were predominant (adjusted hazard ratio for interaction 0.66, 95% CI 0.53-0.84). In a prediction model, it was estimated that >8000 BAU/mL anti-S1 IgG was required to reduce the risk of infection with Omicron variants by approximately 20%-30% for 90 days. Though, such high levels were only found in 1.9% of the samples before the Omicron surge, and they were not durable for 3 months. Anti-S1 IgG antibody levels are statistically associated with protection from SARS-CoV-2 infection. However, the prediction impact of the antibody level findings on infection protection is limited.

Prevalence of anti-tick-borne encephalitis virus (TBEV) antibodies in Swiss blood donors in 2014-2015.

BACKGROUND: Disease morbidity of tick-borne encephalitis (TBE) has been increasing over the last decades. Since the 1990s, however, no extensive seroprevalence studies on TBE in humans have been performed in Switzerland. Here we assessed the prevalence of anti-TBE virus (TBEV) antibodies among different groups of the Swiss blood donor population. MATERIALS AND METHODS: The study was carried out from July 2014 to January 2015. Blood donors participating in the study (n=9,328) were asked to fill in a questionnaire relating to vaccination against or infection with different flaviviruses, and blood samples were collected. All samples were screened for the presence of anti-TBEV IgG antibodies using ELISA testing. Seropositivity rates in different groups of blood donors were compared using Chi square tests with Bonferroni correction. RESULTS: In 2014 and 2015, 24.6% of healthy Swiss blood donors indicated vaccination against TBE. Among vaccinated blood donors, antibody prevalence was significantly higher in younger (<40y: 85.3%) than older individuals (≥40 to <55y: 80.0%, ≥55y: 76.7%; p=0.005). In non-vaccinated individuals, antibody prevalence was significantly higher in younger (<40y: 10.0%) than older (≥40 to <55y: 4.0%, ≥55y: 3.9%; p<0.005), male (6.8%) than female (3.7%, p<0.0001), and blood donors from endemic (7.0%) than border (6.2%) or non-endemic regions (4.2%, p<0.001). Possible asymptomatic infection, as defined by positive IgG ELISA results in blood donors indicating no vaccination against TBEV, was found in 5.6%. DISCUSSION: Our data importantly complement the knowledge on TBEV vaccination rates and estimate the frequency of subclinical TBE in Switzerland.

Evolution of Blood Safety in Switzerland over the Last 25 Years for HIV, HCV, HBV and Treponema pallidum.

During the last few decades, efforts to increase the safety of blood and blood products have mainly focused on preventing the viral infections HCV, HIV, HBV and Treponema pallidum. The evolution of these approaches and the achieved increase in safety is shown for the last 25 years in Switzerland. In detail, the prevalences and incidences of the infection disease and the theoretical estimated residual risks (RR) of these blood-borne infections are presented. Prevalences, incidences and, in particular, the RR have decreased considerably over the last 25 years. This was achieved primarily by the adoption of strict criteria for the selection of blood donors, refined questionnaires, the introduction of increasingly sensitive serological screening tests and the implementation of nucleic acid testing (NAT) for these blood-borne pathogens. These NAT assays have significantly shortened the window period between infection and the first detection of the infectious agent in the blood of an infected individual. A form of "real life" comparison or confirmation is provided by the reported lookback procedures (LBP) and the haemovigilance data of the Swiss competent authority, Swissmedic. These data are in agreement, and thus support the very low prevalences, incidences and RR.

Serosurveillance after a COVID-19 vaccine campaign in a Swiss police cohort.

INTRODUCTION: To assess the risk for COVID-19 of police officers, we are studying the seroprevalence in a cohort. The baseline cross-sectional investigation was performed before a vaccination campaign in January/February 2021, and demonstrated a seroprevalence of 12.9%. Here, we demonstrate serosurveillance results after a vaccination campaign. METHODS: The cohort consists of 1022 study participants. The 3- and 6-month follow-up visits were performed in April/May and September 2021. Data on infection and vaccination rates were obtained via measuring antibodies to the nucleocapsid protein and spike protein and online questionnaires. RESULTS: The mean age of the population was 41 (SD 8.8) years, 72% were male and 76% had no comorbidity. Seroconversion was identified in 1.05% of the study population at the 3-month visit and in 0.73% at the 6-month visit, resulting in an infection rate of 1.8% over a time period of 6 months. In comparison, the infection rate in the general population over the same time period was higher (3.18%, p = .018). At the 6-month visit, 77.8% of participants reported being vaccinated once and 70.5% twice; 81% had an anti-S antibody titer of >250 U/ml and 87.1% of ≥2 U/ml. No significant association between infection and job role within the department, working region, or years of experience in the job was found. Anti-spike antibody titers of vaccinated study participants showed a calculated decreasing trend 150-200 days after the second vaccine dose. CONCLUSION: These data confirm the value of the vaccination campaign in an exposed group other than healthcare professionals.

A Multidimensional Cross-Sectional Analysis of Coronavirus Disease 2019 Seroprevalence Among a Police Officer Cohort: The PoliCOV-19 Study.

BACKGROUND: Protests and police fieldwork provide a high-exposure environment for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. In this cross-sectional analysis, we investigated the seroprevalence among a police cohort, and sociodemographic, work, and health-related factors associated with seropositivity. METHODS: Study participants were invited for serological testing of SARS-CoV-2 and to complete online questionnaires. Serum neutralization titers toward the wild-type SARS-CoV-2 spike protein (expressing D614G) and the Alpha and Beta variants were measured in seropositive study participants. RESULTS: A total of 978 police personnel representing 35% of the entire staff participated from February to March 2021. The seroprevalence was 12.9%. It varied by geographic region, ranged from 9% to 13.5% in 3 regions, including the city; and was 22% in Bernese Seeland/Jura with higher odds for seropositivity (odds ratio [OR], 2.38 [95% confidence interval {CI}, 1.28-4.44], P=.006). Job roles with mainly office activity were associated with a lower risk of seropositivity (OR, 0.33 [95% CI, .14-.77], P=.010). Self-reported compliance with mask wearing during working hours was 100%; 45% of seropositive vs 5% of seronegative participants (P<.001) reported having had contact with a proven coronavirus disease 2019 (COVID-19) case living in the same household prior to serological testing. The level of serum antibody titers correlated with neutralization capacity. Antibodies derived from natural SARS-CoV-2 infection effectively neutralized the SARS-CoV-2 spike protein, but were less effective against the Alpha and Beta variants. CONCLUSIONS: The seroprevalence of anti-SARS-CoV-2 antibodies of police officers was comparable to that reported in the general population, suggesting that the personal protective equipment of the police is effective, and that household contacts are the leading transmission venues. The level of serum antibody titers, in particular that of anti-spike antibodies, correlated well with neutralization capacity. Low antibody titers acquired from natural infection were not effective against variants. CLINICAL TRIALS REGISTRATION: NCT04643444.

Comparison of a New IgG-EIA for the Detection of Anti-Plasmodium Antibodies with Two Currently Used Assays.

BACKGROUND: Malaria is a mosquito-borne infectious disease caused by protozoan parasites of the genus Plasmodium. As migration of populations from endemic areas to Europe and overseas recreational travel to endemic regions increase, there is also a growing risk of transfusion-transmitted tropical diseases by blood components. MATERIAL AND METHODS: In the present study two routine Plasmodium spp. ELISA (CAPTIA™ Malaria EIA, Trinity Biotech, and Malaria EIA, BioRad) were compared with a new commercial ELISA (ELISA IgG, EUROIMMUN). From December 1, 2015 until November 30, 2016, 1,096 plasma samples from blood donors with a potential risk of malaria infection were collected at two blood transfusion centres in Germany and Switzerland. RESULTS: The samples were tested comparatively with the ELISA from EUROIMMUN and the routine test used at the respective centre. Thirty-four of 595 (5.7%) tested blood samples from centre 1 and 49 of 501 (9.8%) tested blood samples from centre 2 showed reactivity on either or both ELISAs. All 83 reactive samples were sent for confirmation to the Diagnostic Centre of the Swiss Tropical and Public Health Institute (Swiss TPH) in Basel, Switzerland. Sixteen samples, which previously were reactive in the routine Plasmodium spp. EIA assays, were proven positive after confirmation testing (i.e., 4 positive and 12 inconclusive results), indicating an anti-Plasmodium antibody prevalence in blood donations of 1.5%. From these 16 reactive samples, 13 were also detected by the index test, resulting in an assay sensitivity of 81.2%. A specificity of 98.6% was calculated (1,065/1,080 confirmed negative samples). The overall agreement with the reference centre was 95.8% in centre 1 and 94% in centre 2. CONCLUSION: The comparison of the new EUROIMMUN ELISA and the established CAPTIA™ Malaria EIA (Trinity Biotech) and Malaria EIA (BioRad) used for routine blood donor screening in two laboratory blood donation centres revealed that all tested ELISAs show comparable sensitivities and are equally suitable for anti-Plasmodium antibody screening in blood banks.

Multicentre Performance Evaluation of the Elecsys Anti-SARS-CoV-2 Immunoassay as an Aid in Determining Previous Exposure to SARS-CoV-2.

INTRODUCTION: We performed a multicentre evaluation of the Elecsys® Anti-SARS-CoV-2 immunoassay (Roche Diagnostics), an assay utilising a recombinant protein representing the nucleocapsid (N) antigen, for the in vitro qualitative detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: Specificity was evaluated using serum/plasma samples from blood donors and routine diagnostic specimens collected before September 2019 (i.e., presumed negative for SARS-CoV-2-specific antibodies); sensitivity was evaluated using samples from patients with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection. Point estimates and 95% confidence intervals (CIs) were calculated. Method comparison was performed versus commercially available assays. RESULTS: Overall specificity for the Elecsys Anti-SARS-CoV-2 immunoassay (n = 9575) was 99.85% (95% CI 99.75-99.92): blood donors (n = 6714; 99.82%), routine diagnostic specimens (n = 2861; 99.93%), pregnant women (n = 2256; 99.91%), paediatric samples (n = 205; 100.00%). The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated significantly higher specificity versus LIAISON SARS-CoV-2 S1/S2 IgG (99.71% vs. 98.48%), EUROIMMUN Anti-SARS-CoV-2 IgG (100.00% vs. 94.87%), ADVIA Centaur SARS-CoV-2 Total (100.00% vs. 87.32%) and iFlash SARS-CoV-2 IgM (100.00% vs. 99.58%) assays, and comparable specificity to ARCHITECT SARS-CoV-2 IgG (99.75% vs. 99.65%) and iFlash SARS-CoV-2 IgG (100.00% vs. 100.00%) assays. Overall sensitivity for Elecsys Anti-SARS-CoV-2 immunoassay samples drawn at least 14 days post-PCR confirmation (n = 219) was 93.61% (95% CI 89.51-96.46). No statistically significant differences in sensitivity were observed between the Elecsys Anti-SARS-CoV-2 immunoassay versus EUROIMMUN Anti-SARS-CoV-2 IgG (90.32% vs. 95.16%) and ARCHITECT SARS-CoV-2 IgG (84.81% vs. 87.34%) assays. The Elecsys Anti-SARS-CoV-2 immunoassay showed significantly lower sensitivity versus ADVIA Centaur SARS-CoV-2 Total (85.19% vs. 95.06%) and iFlash SARS-CoV-2 IgG (86.25% vs. 93.75%) assays, but significantly higher sensitivity versus the iFlash SARS-CoV-2 IgM assay (86.25% vs. 33.75%). CONCLUSION: The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated very high specificity and high sensitivity in samples collected at least 14 days post-PCR confirmation of SARS-CoV-2 infection, supporting its use to aid in determination of previous exposure to SARS-CoV-2.

Safe-Testing Algorithm for Individual-Donation Nucleic Acid Testing: 10 Years of Experience in a Low-Prevalence Country.

INTRODUCTION: A highly sensitive and specific nucleic acid test (NAT) for the blood-borne viruses human immunodeficiency virus (HIV), hepatitis C (HCV), and hepatitis B (HBV) is essential for the safety of blood components. Since more than 2 decades, NAT screening of blood donations has become standard in developed countries that have implemented the individual-donation (ID-NAT) and mini-pool NAT (MP-NAT) approaches. With this powerful technique, confirmation of initial reactive (IR) NAT samples becomes a challenge. Different algorithms are currently in use to eliminate false reactive results. To show that the algorithm implemented in 2007, that uses repeat testing of IR samples in duplicate runs, is a safe strategy, especially in low endemic countries, data from a 10-year experience of ID-NAT were extensively analyzed when follow-up data were available. METHODS: From July 2007 to December 2014, the Procleix Ultrio assay on a Procleix Tigris system, and from January 2015 to December 2017, the cobas MPX on a cobas 8800 platform, were used for ID-NAT screening. All IR samples were subjected to repeat testing in duplicate independent runs. Only when both tests remained negative were the products released. Donor data from the last 10 years were investigated retrospectively, looking for the reoccurrence of a reactive result in a follow-up sample. Only those donors with at least an x + 1 donation result were included for the confirmation of a false reactive result. RESULTS: From the 1,830,657 donations tested, 2,450 samples were IR (0.13%); only 228 were repeat reactive ([RR], 18 HIV, 61 HCV, and 149 HBV samples), and 2,222 were non-RR (0.12%). Follow-up data were available from 1,267 donors (57%) for further analysis. All except one of these donors were ID-NAT-negative in all follow-up samples. The one exception was from a donor who acquired a fresh HBV infection 10 years after the IR donation (in the x + 28 donation) and subsequently seroconverted. Subsequent serological tests from all succeeding donations (x + 1, x + 2, etc.) were negative in all the other cases, proving that no seroconversion took place after the IR ID-NAT result. CONCLUSIONS: The algorithm to deal with IR ID-NAT donations using duplicate repeat testing is very safe and cost-effective in low-prevalence countries. There is no unnecessary destruction of blood products, no counseling of false reactive donors, and also no need to add further complexity to the screening algorithm.

Low-Frequency Blood Group Antigens in Switzerland.

BACKGROUND: High-frequency blood group antigens (HFA) are present in >90% of the human population, according to some reports even in >99% of individuals. Therefore, patients lacking HFA may become challenging for transfusion support because compatible blood is hardly found, and if the patient carries alloantibodies, the cross-match will be positive with virtual every red cell unit tested. METHODS: In this study, we applied high-throughput blood group SNP genotyping on >37,000 Swiss blood donors, intending to identify homozygous carriers of low-frequency blood group antigens (LFA). RESULTS: 326 such individuals were identified and made available to transfusion specialists for future support of patients in need of rare blood products. CONCLUSION: Thorough comparison of minor allele frequencies using population genetics revealed heterogeneity of allele distributions among Swiss blood donors which may be explained by the topographical and cultural peculiarities of Switzerland. Moreover, geographically localized donor subpopulations are described which contain above-average numbers of individuals carrying rare blood group genotypes.

Current hepatitis E virus seroprevalence in Swiss blood donors and apparent decline from 1997 to 2016.

Background and aimHepatitis E virus (HEV) is a virus of emerging importance to transfusion medicine. Studies from several European countries, including Switzerland, have reported high seroprevalence of hepatitis E as a consequence of endemic infections. Published HEV seroprevalence estimates within developed countries vary considerably; primarily due to improved diagnostic assays. The purpose of this study was to investigate the seroprevalence of anti-HEV IgG in Swiss blood donations. Methods: We used the highly sensitive Wantai HEV IgG EIA and assessed regional distribution patterns. We analysed age- and sex-matched archive plasma dating back 20 years from canton Bern to investigate recent changes in HEV seroprevalence levels. Results: On average, 20.4% (95% confidence intervals: 19.1-21.8) of the 3,609 blood samples collected in 2014-16 were anti-HEV IgG positive; however, distinct differences between geographical regions were observed (range: 12.8-33.6%). Seroprevalence increased with age with 30.7% of males and 34.3% of women being positive donors over > 60 years old. Differences between sexes may be attributed to dissimilarities in the average age of this group. Within the specified region of the Bern canton, overall prevalence has declined over two decades from 30.3% in 1997/98 to 27.0% in 2006 and 22.3% in 2015/6. Conclusions: HEV seroprevalence in Switzerland is high, but has declined over the last decades. The result shows that primarily endemic HEV infections occur and that current blood products may pose a risk to vulnerable transfusion recipients. Nucleic acid screening of all blood products for HEV will begin in November 2018.

Protocol of a Multicenter International Randomized Controlled Manikin Study on Different Protocols of Cardiopulmonary Resuscitation for laypeople (MANI-CPR).

INTRODUCTION: Out-of-hospital cardiac arrest is one of the leading causes of death in industrialised countries. Survival depends on prompt identification of cardiac arrest and on the quality and timing of cardiopulmonary resuscitation (CPR) and defibrillation. For laypeople, there has been a growing interest on hands-only CPR, meaning continuous chest compression without interruption to perform ventilations. It has been demonstrated that intentional interruptions in hands-only CPR can increase its quality. The aim of this randomised trial is to compare three CPR protocols performed with different intentional interruptions with hands-only CPR. METHODS AND ANALYSIS: This is a prospective randomised trial performed in eight training centres. Laypeople who passed a basic life support course will be randomised to one of the four CPR protocols in an 8 min simulated cardiac arrest scenario on a manikin: (1) 30 compressions and 2 s pause; (2) 50 compressions and 5 s pause; (3) 100 compressions and 10 s pause; (4) hands-only. The calculated sample size is 552 people. The primary outcome is the percentage of chest compression performed with correct depth evaluated by a computerised feedback system (Laerdal QCPR). ETHICS AND DISSEMINATION: . Due to the nature of the study, we obtained a waiver from the Ethics Committee (IRCCS Policlinico San Matteo, Pavia, Italy). All participants will sign an informed consent form before randomisation. The results of this study will be published in peer-reviewed journal. The data collected will also be made available in a public data repository. TRIAL REGISTRATION NUMBER: NCT02632500.

Selective Testing of At-Risk Blood Donors for Trypanosoma cruzi and Plasmodium spp. in Switzerland.

BACKGROUND: Population migrations and overseas recreational travel to regions at risk for tropical diseases are increasing. A major challenge in non-endemic countries is to decrease the number of blood donor deferrals due those tropical disease pathogens, without compromising the high level of blood safety. The protozoans Trypanosoma cruzi and Plasmodium spp., the causative organisms of Chagas disease (CD) and malaria are becoming a major focus in the blood transfusion community. METHODS: National guidelines of the Blood Transfusion Service of the Swiss Red Cross propose an algorithm for dealing with these pathogens, including a mandatory selective serological testing of donors at risk. RESULTS: 6,978 donors at risk for CD were tested. Three of them were confirmed anti-T. cruzi -positive, and in one case a transfusion-transmitted infection was highly possible. The specificity of the assay was 99.94%. For malaria 12,887 donors were at risk and 178 were confirmed positive. The specificity of the assays was 92.8%. CONCLUSION: CD and malaria in non-endemic countries may represent a certain risk for blood transfusion. Switzerland chose a selective testing approach. The specificity of the assays is a crucial topic for this approach because it ensures a minimal loss of false-reactive donors and helps towards an easier counselling of implicated donors.

Comparison of a conventional HIV 1/2 line immunoassay with a rapid confirmatory HIV 1/2 assay.

The performance of the rapid confirmatory HIV 1/2 assay Geenius was compared with the conventional HIV 1/2 line immunoblot (INNO-LIA HIV I/II Score). One hundred HIV 1/2 confirmed positive samples from donors and patients and 136 negative screening samples from blood donors were evaluated with both assays. A 20 member performance panel consisting of different HIV 1 and 2 subtypes was also analysed. Ninety-nine of the confirmed HIV positive samples were positive with both assays. One sample was positive with the INNO-LIA HIV I/II Score but indeterminate with the Geenius HIV 1/2. From 136 negative blood donor samples (negative with a combo HIV assay and a highly sensitive ID-NAT), 125 were concordant negative. Six and five samples were incorrectly indeterminate with the INNO-LIA HIV I/II Score and the Geenius HIV 1/2, respectively. One sample was weak positive with the INNO-LIA HIV I/II Score but negative with the Geenius HIV 1/2. The 20 member performance showed equivalent results with both assays. The rapid assay showed a comparable sensitivity and specificity for confirmation for positive and negative HIV donor and patient samples as well for a 20 member performance panel.

Hepatitis B virus DNA viral load determination in hepatitis B surface antigen-negative Swiss blood donors.

BACKGROUND: Nucleic acid test (NAT) hepatitis B virus (HBV) screening for all blood donations with a sensitivity limit of 25 IU/mL in the individual donation is mandatory in Switzerland since 2009. The aims of the two studies were to define the percentage of antibody to hepatitis B core antigen (anti-HBc) or anti-HBc and antibody to hepatitis B surface antigen (anti-HBs)-positive donors bearing HBV DNA and to gather HBV viral load data on HBV NAT yields during the routine screening since the introduction of the HBV NAT. STUDY DESIGN AND METHODS: Archive samples from anti-HBc-positive donors (Group I) were analyzed with a quantitative HBV DNA test and further with anti-HBc and anti-HBs assays. In addition, all the HBV NAT-only-yield samples (Group II) from the routine donor screening performed between July 2007 and May 2013 were included in the study. RESULTS: From the 667 samples investigated (131 donors), three donors (2.3%) had donated eight samples (1.2%) with detectable HBV DNA; however, all had very low viral loads (≤ 10 IU/mL). From the 1,160,426 donations screened with the routine HBV NAT assay, 16 HBV NAT yields were detected: two window period (WP) and 14 occult hepatitis B infection (OBI) cases. In eight of these positive donations (two WP and six OBI), the HBV viral loads were not more than 10 IU/mL, in three cases between 10 and 25 IU/mL, and in the remaining five donations between 37 and 166 IU/mL. CONCLUSION: The highly sensitive HBV NAT assay with a threshold significantly below 10 IU/mL is a valuable alternative to anti-HBc and a less sensitive HBV NAT screening in blood donor screening.

Reverse vertical transmission of hepatitis B virus (HBV) infection from a transfusion-infected newborn to her mother.

BACKGROUND & AIMS: Clinical cases of viral infections possibly involving the transfusion of blood components are systematically investigated. METHODS: Serological and molecular markers of hepatitis B virus were used including HBsAg, anti-HBc, anti-HBs, HBV DNA, and viral load. Full genome sequencing and phylogenetic analyses were performed. RESULTS: An acute HBV infection was diagnosed in the mother of a 16-month-old daughter who had been transfused at age three weeks with one quarter of a regular red cell concentrate (RCC). The repeat donor of the index donation was free of HBV markers in two previous donations but seroconverted to anti-HBc and anti-HBs 3 months post-donation of a unit containing only low level of HBV DNA. One other newborn recipient of the same RCC was asymptomatically HBV infected. A third newborn recipient whose mother had been HBV vaccinated and carried moderate level of anti-HBs was not infected. Full length nucleotide sequence identity between HBV strains from the mother and the two infected transfusion recipients provided evidence of the transfusion origin of all three infections in the absence of donor sequence. CONCLUSIONS: Reverse vertical HBV transmission was likely the result of casual mother contact with a baby carrying extremely high viral load. The blood products intended to immunodeficient newborn should be submitted to more thorough viral testing considering their increased susceptibility to infections.

Efficacy of individual nucleic acid amplification testing in reducing the risk of transfusion-transmitted hepatitis B virus infection in Switzerland, a low-endemic region.

BACKGROUND: The risk of transfusion-transmitted hepatitis B virus (HBV) in Switzerland by testing blood donors for hepatitis B surface antigen (HBsAg) alone has been historically estimated at 1:160,000 transfusions. The Swiss health authorities decided not to introduce mandatory antibody to hepatitis B core antigen (anti-HBc) testing but to evaluate the investigation of HBV nucleic acid testing (NAT). STUDY DESIGN AND METHODS: Between June 2007 and February 2009, a total of 306,000 donations were screened routinely for HBsAg and HBV DNA by triplex individual-donation (ID)-NAT (Ultrio assay on Tigris system, Gen-Probe/Novartis Diagnostics). ID-NAT repeatedly reactive donors were further characterized for HBV serologic markers and viral load by quantitative polymerase chain reaction. The relative sensitivity of screening for HBsAg, anti-HBc, and HBV DNA was assessed. The residual HBV transmission risk of NAT with or without anti-HBc and HBsAg was retrospectively estimated in a mathematical model. RESULTS: From the 306,000 blood donations, 31 were repeatedly Ultrio test reactive and confirmed HBV infected, of which 24 (77%) and 27 (87%) were HBsAg and anti-HBc positive, respectively. Seven HBV-NAT yields were identified (1:44,000), two pre-HBsAg window period (WP) donations (1:153,000) and five occult HBV infections (1:61,000). Introduction of ID-NAT reduced the risk of HBV WP transmission in repeat donors from 1:95,000 to 1:296,000. CONCLUSIONS: Triplex NAT screening reduced the HBV WP transmission risk approximately threefold. NAT alone was more efficacious than the combined use of HBsAg and anti-HBc. The data from this study led to the decision to introduce sensitive HBV-NAT screening in Switzerland. Our findings may be useful in designing more efficient and cost-effective HBV screening strategies in low-prevalence countries.

Blood donor screening: how to decrease the risk of transfusion-transmitted hepatitis B virus?

QUESTIONS UNDER STUDY: The risk of transfusion-transmitted HBV remains significant in Switzerland, where routine screening for hepatitis B virus (HBV) in blood donations relies solely on serological hepatitis B surface antigen (HBsAg) testing. This study was designed to determine the prevalence of anti-hepatitis B core (anti-HBc) and HBV nucleic acid testing (NAT) positive donations in two different Swiss donor populations, to help in deciding whether supplemental testing may bring additional safety to blood products. METHODS: In a first population of donors, 18143 consecutive donations were screened initially for HBsAg, anti-HBc (with one EIA assay) and with HBV NAT in minipools of 24 donations. The screening repeatedly reactive anti-HBc donations were then "confirmed" with two supplemental anti-HBc assays, an anti-hepatitis B surface assay (anti-HBs) and with single donation HBV NAT. In a second population of donors, 4186 consecutive donations were screened initially with two different anti-HBc assays in addition to the mandatory HBsAg screening test. The screening repeatedly reactive donations with at least one anti-HBc assay were tested for anti-HBs. RESULTS: In the first subset of 18143 donations, 17593 (97.0%) were negative for HBsAg, anti-HBc and HBV NAT in minipools. 549 (3.0%) were HBsAg and HBV NAT negative, but repeatedly reactive for anti-HBc. Of these 549 donations, 287 could not be "confirmed" with two additional anti-HBc assays and were negative with an anti-HBs assay, as well as with single donation HBV NAT. Only 211 (1.2% of the total screened donations) were "confirmed" positive with at least one of two supplemental anti-HBc assays. One repeatedly reactive HBsAg donation, from a first-time donor, was confirmed positive for HBsAg and anti-HBc, as well as with single donation HBV NAT. In the second subset of 4186 donations, 4014 (95.9%) were screened negative for HBsAg and for anti-HBc, tested with two independent anti-HBc assays. 172 donations (4.1%) were HBsAg negative but repeatedly reactive with at least one of the two anti-HBc assays. Of these 172 samples, 86 were reactive with the first anti-HBc assay only, 13 were reactive with the second anti-HBc assay only and 73 (1.7% of the total screened donations) were "confirmed" positive with both anti-HBc assays. CONCLUSION: The prevalence of anti-HBc "confirmed" positive donations in the two Swiss blood donor populations studied was low (<2%) and we found only one HBV NAT positive (HBsAg positive) donation among more than 18000. Concerning blood product safety, an increase in the deferral rate of less than 2% of anti-HBc positive, potentially infectious donors, would in our opinion make routine anti-HBc testing of blood donations cost-effective. There is however still a need for more specific assays to avoid an unacceptably high deferral rate of "false" positive donors. In contrast, the introduction of HBV NAT in minipools gives minimal benefit due to the inadequate sensitivity of the assay. It remains to evaluate more extensively the value of individual donation NAT, alone or in addition to anti-HBc, as supplemental testing in the context of several Swiss blood donor populations.

Spectrotype analysis and clonal characteristics of human anti-Gal alpha1-3Gal antibodies.

Galalpha1-3Gal (anti-Gal), a polyclonal so-called natural antibody (Ab), is present in large amounts in human serum not only as IgG-, but also as IgM- and IgA-isotypes. It has gained a particular interest in the context of xenotransplantation, because the endothelial pig cells express the terminal Galalpha1-3Gal determinant on several adhesion molecules. Little is known of it's function and direct examination of the structure of the Ig genes responsible for coding anti-Gal is lacking. We used the technique of isoelectric focussing (IEF)/affinity immunoblotting for direct analysis of the clonal distribution and spectrotype analysis of IgM- and IgG anti-Gal. By single cell analysis of magnetic bead and fluorescent-activated cell sorter (FACS) isolated mature anti-Gal bearing human B cells from whole blood we analyzed the VH gene families involved in anti-Gal production. Oligoclonal and individually distinct IgG banding patterns were found with isoelectric points between 4 and 9. IgM spectrotypes revealed to be more uniform with a polyclonal banding pattern of more than 12 bands at a pH between 4.7 and 7. IgG- and IgM-banding patterns over a period of 6 months remained unchanged. Single cell polymerase chain reaction (PCR), with all family specific primers, revealed the use of the VH2f gene family for the IgG2 isoptype. The differences found in the spectrotype banding patterns of IgG and IgM could be explained by the suggestion that anti-Gal IgM were produced by the use of unmutated germline genes and the possibility of the absence of somatic mutations. The greater clonal heterogeneity in the IgG population could be explained by somatic hypermutations during the switch from IgM to IgG. The use of this VH2f gene family, which is also involved in the generation of Abs against bacterial pathogens, could mean that this is a predominant region used for the generation of such natural occurring antibodies.