Neutralization of SARS-CoV-2 Omicron XBB.1.5 and JN.1 variants after COVID-19 booster-vaccination and infection.

SARS-CoV-2 Omicron lineages continue to emerge and evolve into new sublineages, causing infection waves throughout 2022 and 2023, which has been attributed to immune escape. We examined neutralizing antibody responses to the recently emerged SARS-CoV-2 JN.1 variant in comparison to ancestral D614G and Omicron BA.1, BA.2, BA.5, and XBB.1.5 variants. We tested 79 human sera from cohorts with different combinations of vaccinations and infections, including 23 individuals who had been repeatedly exposed to Omicron. Individuals with a monovalent XBB.1.5 vaccine booster or XBB.1.5 breakthrough infection had robust antibody levels against all variants tested; however, JN.1 evaded antibodies in individuals after single Omicron BA.1, BA.2 or BA.5 breakthrough infections. Moreover, in the non-vaccinated cohort, serum antibodies demonstrated almost no cross-neutralization activities against D614G, XBB.1.5 and JN.1. after infections with earlier Omicron variants. These findings show that SARS-CoV-2-immunity is heterogeneous, depending on different combinations of vaccinations and infections, and emphasize the importance of considering different immune-backgrounds when evaluating novel variants.

Continued circulation of mpox: an epidemiological and phylogenetic assessment, European Region, 2023 to 2024.

During the summer of 2023, the European Region experienced a limited resurgence of mpox cases following the substantial outbreak in 2022. This increase was characterised by asynchronous and bimodal increases, with countries experiencing peaks at different times. The demographic profile of cases during the resurgence was largely consistent with those reported previously. All available sequences from the European Region belonged to clade IIb. Sustained efforts are crucial to control and eventually eliminate mpox in the European Region.

External quality assessments for SARS-CoV-2 genome detection in Austria : A comparison of the first postpandemic round with results from the pandemic era.

BACKGROUND: External quality assessment (EQA) schemes provide objective feedback to participating laboratories about the performance of their analytical systems and information about overall regional analytical performance. The EQAs are particularly important during pandemics as they also assess the reliability of individual test results and show opportunities to improve test strategies. With the end of the COVID-19 pandemic, the testing frequency significantly decreased in Austria. Here, we analyzed whether this decrease had an effect on participation and/or performance in SARS-CoV­2 virus detection EQAs, as compared to the pandemic era. MATERIAL AND METHODS: Identical samples were sent to all participating laboratories, and the EQA provider evaluated the agreement of the reported results with defined targets. The EQA was operated under two schemes with identical samples and therefore we analyzed it as a single EQA round. The performance of testing was reported as true positive ratios, comparing the post-pandemic data to previous rounds. Furthermore, subgroups of participants were analyzed stratified by laboratory type (medical or nonmedical) and the test system format (fully automated or requiring manual steps). RESULTS: While the frequency of false negative results per sample did not change during the 3 years of the pandemic (5.7%, 95% confidence interval [CI] 3.1-8.4%), an average per sample false negative ratio of 4.3% was observed in the first post-pandemic EQA (0%, 1.8%, and 11% for the 3 positive samples included in the test panel, n = 109 test results per sample). In this first post-pandemic EQA medical laboratories (average 0.4% false negative across 3 samples, n = 90) and automated test systems (average 1.2% false negative, n = 261) had lower false negative ratios than nonmedical laboratories (22.8%, n = 19) and manual test systems (16.7%, n = 22). These lower average ratios were due to a low concentration sample, where nonmedical laboratories reported 36.8% and manual test systems 54.5% true positive results. CONCLUSION: Overall ratios of true positive results were below the mean of all results during the pandemic but were similar to the first round of the pandemic. A lower post-pandemic true positive ratio was associated with specific laboratory types and assay formats, particularly for samples with low concentration. The EQAs will continue to monitor the laboratory performance to ensure the same quality of epidemiological data after the pandemic, even if vigilance has decreased.

Virus sequencing performance during the SARS-CoV-2 pandemic: a retrospective analysis of data from multiple rounds of external quality assessment in Austria.

Introduction: A notable feature of the 2019 coronavirus disease (COVID-19) pandemic was the widespread use of whole genome sequencing (WGS) to monitor severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Countries around the world relied on sequencing and other forms of variant detection to perform contact tracing and monitor changes in the virus genome, in the hopes that epidemic waves caused by variants would be detected and managed earlier. As sequencing was encouraged and rewarded by the government in Austria, but represented a new technicque for many laboratories, we designed an external quality assessment (EQA) scheme to monitor the accuracy of WGS and assist laboratories in validating their methods. Methods: We implemented SARS-CoV-2 WGS EQAs in Austria and report the results from 7 participants over 5 rounds from February 2021 until June 2023. The participants received sample material, sequenced genomes with routine methods, and provided the sequences as well as information about mutations and lineages. Participants were evaluated on the completeness and accuracy of the submitted sequence and the ability to analyze and interpret sequencing data. Results: The results indicate that performance was excellent with few exceptions, and these exceptions showed improvement over time. We extend our findings to infer that most publicly available sequences are accurate within ≤1 nucleotide, somewhat randomly distributed through the genome. Conclusion: WGS continues to be used for SARS-CoV-2 surveillance, and will likely be instrumental in future outbreak scenarios. We identified hurdles in building next-generation sequencing capacity in diagnostic laboratories. EQAs will help individual laboratories maintain high quality next-generation sequencing output, and strengthen variant monitoring and molecular epidemiology efforts.

Performance of SARS-CoV-2 nucleic acid amplification testing in Austria as measured by external quality assessment schemes during 3 years of the COVID-19 pandemic: an observational retrospective study.

BACKGROUND: The aim of external quality assessment (EQA) schemes is to evaluate the analytical performance of laboratories and test systems in a near-to-real-life setting. This monitoring service provides feedback to participant laboratories and serves as a control measure for the epidemiological assessment of the regional incidence of a pathogen, particularly during epidemics. Using data from EQA schemes implemented as a result of the intensive effort to monitor SARS-CoV-2 infections in Austria, we aimed to identify factors that explained the variation in laboratory performance for SARS-CoV-2 detection over the course of the COVID-19 pandemic. METHODS: For this observational study, we retrospectively analysed 6308 reverse transcriptase quantitative PCR (RT-qPCR) test results reported by 191 laboratories on 71 samples during 14 rounds of three SARS-CoV-2 pathogen detection EQA schemes in Austria between May 18, 2020, and Feb 20, 2023. We calculated the overall rates of false and true-negative, false and true-positive, and inconclusive results. We then assessed laboratory performance by estimating the sensitivity by testing whether significant variation in the odds of obtaining a true-positive result could be explained by virus concentration, laboratory type, or assay format. We also assessed whether laboratory performance changed over time. FINDINGS: 4371 (93·7%) of 4663 qPCR test results were true-positive, 241 (5·2%) were false-negative, and 51 (1·1%) were inconclusive. The mean per-sample sensitivity was 99·7% in samples with high virus concentrations (1383 [99·4%] true-positive, three [0·2%] false-negative, and five [0·4%] inconclusive results for 1391 tests in which the sample cycle threshold was ≤32), whereas detection rates were lower in samples with low virus concentrations (mean per-sample sensitivity 92·5%; 2988 [91·3%] true-positive, 238 [7·3%] false-negative, and 46 [1·4%] inconclusive results for 3272 tests in which the cycle threshold was >32). Of the 1645 results expected to be negative, 1561 (94·9%) were correctly reported as negative, 10 (0·6%) were incorrectly reported as positive, and 74 (4·5%) were reported as inconclusive. Notably, the overall performance of the tests did not change significantly over time. The odds of reporting a correct result were 2·94 (95% CI 1·75-4·96) times higher for a medical laboratory than for a non-medical laboratory, and 4·60 (2·91-7·41) times greater for automated test systems than for manual test systems. Automated test systems within medical laboratories had the highest sensitivity when compared with systems requiring manual intervention in both medical and non-medical laboratories. INTERPRETATION: High rates of false-negativity in all PCR analyses evaluated in comprehensive, multiple, and repeated EQA schemes outline a clear path for improvement in the future. The performance of some laboratories (eg, non-medical laboratories or those using non-automated test systems) should receive additional scrutiny-for example, by requiring additional EQA schemes for certification or accreditation-if the aggregated data from EQA rounds suggest lower sensitivity than that recorded by others. This strategy will provide assurances that epidemiological data as a whole are reliable when testing on such a large scale. Although performance did not improve over time, we cannot exclude extenuating circumstances-such as shortages and weakened supply chains-that could have prevented laboratories from seeking alternative methods to improve performance. FUNDING: None.

Effect of previous heterologous flavivirus vaccinations on human antibody responses in tick-borne encephalitis and dengue virus infections.

Arthropod-borne flaviviruses include a number of medically relevant human pathogens such as the mosquito-borne dengue (DEN), Zika, and yellow fever (YF) viruses as well as tick-borne encephalitis virus (TBEV). All flaviviruses are antigenically related and anamnestic responses due to prior immunity can modulate antibody specificities in subsequent infections or vaccinations. In our study, we analyzed the induction of broadly flavivirus cross-reactive antibodies in tick-borne encephalitis (TBE) and DEN patients without or with prior flavivirus exposure through TBE and/or YF vaccination, and determined the contribution of these antibodies to TBE and dengue virus (DENV) neutralization. In addition, we investigated the formation of cross-reactive antibodies in TBE-vaccination breakthroughs (VBTs). A TBEV infection without prior YF or TBE vaccination induced predominantly type-specific antibodies. In contrast, high levels of broadly cross-reactive antibodies were found in samples from TBE patients prevaccinated against YF as well as in DEN patients prevaccinated against TBE and/or YF. While these cross-reactive antibodies did not neutralize TBEV, they were effective in neutralizing DENV. This discrepancy points to structural differences between the two viruses and indicates that broadly cross-reactive epitopes are less accessible in TBEV than in DENV. In TBE VBT infections, type-specific antibodies dominated the antibody response, thus revealing no difference from that of unvaccinated TBE patients. Our results emphasize significant differences in the structural properties of different flaviviruses that have an impact on the induction of broadly cross-reactive antibodies and their functional activities in virus neutralization.

Bivalent COVID-19 mRNA booster vaccination (BA.1 or BA.4/BA.5) increases neutralization of matched Omicron variants.

We report SARS-CoV-2 neutralizing antibody titers in sera of triple-vaccinated individuals who received a booster dose of an original monovalent or a bivalent BA.1- or BA.4/BA.5-adapted vaccine or had a breakthrough infection with Omicron variants BA.1, BA.2 or BA.4/BA.5. A bivalent BA.4/BA.5 booster or Omicron-breakthrough infection induced increased Omicron-neutralization titers compared with the monovalent booster. The XBB.1.5 variant effectively evaded neutralizing-antibody responses elicited by current vaccines and/or infection with previous variants.

Respiratory syncytial virus surge in 2022 caused by lineages already present before the COVID-19 pandemic.

In 2022, Austria experienced a severe respiratory syncytial virus (RSV) epidemic with an earlier-than-usual start (Weeks 35/2021-45/2022) and increased numbers of pediatric patients in emergency departments. This surge came 2 years after a season with no cases detected as a result of coronavirus disease 2019 nonpharmaceutical interventions. We analyzed epidemiologic patterns and the phylodynamics of RSV based on approximately 30 800 respiratory specimens collected year-round over 10 years from ambulatory and hospitalized patients from 248 locations in Austria. Genomic surveillance and phylogenetic analysis of 186 RSV-A and 187 RSV-B partial glycoprotein sequences collected from 2018 to 2022 revealed that the 2022/2023 surge was driven by RSV-B in contrast to the surge in the 2021/2022 season that was driven by RSV-A. Whole-genome sequencing and phylodynamic analysis indicated that the RSV-B strain GB5.0.6a was the predominant genotype in the 2022/2023 season and emerged in late 2019. The results provide insight into RSV evolution and epidemiology that will be applicable to future monitoring efforts with the advent of novel vaccines and therapeutics.

Long-term follow-up of patients discontinuing bulevirtide treatment upon long-term HDV-RNA suppression.

Background & Aims: Bulevirtide (BLV) is a novel antiviral drug licensed for the treatment of chronic hepatitis D. Data on the safety and efficacy of stopping BLV therapy upon long-term HDV-RNA suppression are scarce. Methods: A total of seven patients (age, 31-68 years, four with cirrhosis) included in a prospective Austrian HDV registry discontinued BLV treatment (duration, 46-141 weeks) upon long-term HDV suppression (HDV-RNA negativity, 12-69 weeks). Pegylated interferon-ɑ2a was used in combination with BLV in two patients. HDV-RNA, alanine aminotransferase, and quantitative HBsAg levels were closely monitored during treatment-free follow-up. Results: The seven patients were followed up for 14 to 112 weeks. Six patients completed ≥24 weeks of follow-up. HDV-RNA became detectable again in three patients within 24 weeks, whereas one additional patient showed an HDV-RNA relapse after almost 1 year. All patients who relapsed at any point had undergone BLV monotherapy. Meanwhile, HDV-RNA remained undetectable in two patients who were treated with BLV + pegylated interferon-ɑ2a. Only one patient showed significant alanine aminotransferase increases within 24 weeks of follow-up. BLV was reintroduced in three patients after 13-62 BLV-free weeks and was well tolerated, and all patients achieved virologic response again. Conclusions: BLV discontinuation upon long-term HDV-RNA suppression seems safe. Retreatment with BLV was effective in case of virologic relapse. These findings are within a limited number of patients, and future studies are needed to define stopping rules and further investigate the safety of stopping BLV. Impact and Implications: Limited data exist on stopping bulevirtide (BLV) treatment in patients who achieve long-term HDV-RNA suppression. In a small cohort of seven Austrian patients discontinuing BLV therapy, HDV-RNA relapses were observed in four patients during long-term follow-up, whereas significant alanine aminotransferase increases were recorded in only one. Retreatment with BLV was effective in relapsers. The safety and efficacy of stopping BLV needs to be further studied in larger cohorts.

Classification of "Near-patient" and "Point-of-Care" SARS-CoV-2 Nucleic Acid Amplification Test Systems and a first approach to evaluate their analytical independence of operator activities.

BACKGROUND: European legislation defines as "near-patient testing" (NPT) what is popularly and in other legislations specified as "point-of-care testing" (POCT). Systems intended for NPT/POCT use must be characterized by independence from operator activities during the analytic procedure. However, tools for evaluating this are lacking. We hypothesized that the variability of measurement results obtained from identical samples with a larger number of identical devices by different operators, expressed as the method-specific reproducibility of measurement results reported in External Quality Assessment (EQA) schemes, is an indicator for this characteristic. MATERIALS AND METHODS: Legal frameworks in the EU, the USA and Australia were evaluated about their requirements for NPT/POCT. EQA reproducibility of seven SARS-CoV-2-NAAT systems, all but one designated as "POCT", was calculated from variabilities in Ct values obtained from the respective device types in three different EQA schemes for virus genome detection. RESULTS: A matrix for characterizing test systems based on their technical complexity and the required operator competence was derived from requirements of the European In Vitro Diagnostic Regulation (IVDR) 2017/746. Good EQA reproducibility of the measurement results of the test systems investigated implies that different users in different locations have no recognizable influence on their measurement results. CONCLUSION: The fundamental suitability of test systems for NPT/POCT use according to IVDR can be easily verified using the evaluation matrix presented. EQA reproducibility is a specific characteristic indicating independence from operator activities of NPT/POCT assays. EQA reproducibility of other systems than those investigated here remains to be determined.

Design of external quality assessment schemes and definition of the roles of their providers in future epidemics.

During an epidemic, individual test results form the basis of epidemiological indicators such as case numbers or incidence. Therefore, the accuracy of measures derived from these indicators depends on the reliability of individual results. In the COVID-19 pandemic, monitoring and evaluating the performance of the unprecedented number of testing facilities in operation, and novel testing systems in use, was urgently needed. External quality assessment (EQA) schemes are unique sources of data reporting on testing performance, and their providers are recognised contacts and support for test facilities (for technical-analytical topics) and health authorities (for planning the monitoring of infection diagnostics). To identify information provided by SARS-CoV-2 genome detection EQA schemes that is relevant for public health microbiology, we reviewed the current literature published in PubMed between January, 2020, and July, 2022. We derived recommendations for EQA providers and their schemes for best practices to monitor pathogen-detection performance in future epidemics. We also showed laboratories, test facilities, and health authorities the information and benefits they can derive from EQA data, and from the non-EQA services of their providers.

Poor Prognosis for Puumala Virus Infections Predicted by Lymphopenia and Dyspnea.

We investigated a prospective cohort of 23 patients who had Puumala virus infection in Austria to determine predictors of infection outcomes. We reviewed routinely available clinical and laboratory parameters collected when patients initially sought care. Low absolute lymphocyte count and dyspnea were parameters associated with a severe course of infection.

Low mortality despite temporary liver dysfunction in severe courses of acute hepatitis E.

BACKGROUND: Hepatitis E virus (HEV) infection can cause severe viral hepatitis and eventually liver failure. We aim to provide novel data on the epidemiology and the course of HEV infections from Q1/2008 to Q3/2018 at the Vienna General Hospital. METHODS: Of the 88,945 people tested, we identified HEV-IgM positive (+) or HEV-PCR (+) patients and retrospectively collated information on the course of infection from patient records. RESULTS: Among 151 HEV-IgM or PCR (+) (median age 51 years, 45.8% female), 7 (4.6%) had non-severe acute HEV infection (ALT ≥ 2-5-fold upper limit of normal, ULN), 11 (7.3%) had severe HEV infection without liver dysfunction (LD) (ALT > 5-fold ULN), and 9 (6.0%) with LD (ikterus or bilirubin > 5 mg/dL, OR coagulopathy or INR > 1.5, OR encephalopathy or ammonia > 100 µmol/L). HEV-RNA-PCR was performed in 58/190 (30.5%) HEV-IgM (+) patients and was positive in 19 (30.6%). Rates of HEV IgM/PCR positivity remained stable over the observation period. The HEV genotype (GT) was GT­1 in 71.4% (n = 5) and GT­3 in 28.6% (n = 2). Travel history was recorded for 9/20 (45.0%) of severe HEV and 12/20 (60.0%) patients with severe HEV infection were hospitalized. One patient with pre-existing liver disease and concomitant EBV infection required intensive care. No patient required transplantation and the 30-day mortality was 3/151 (1.9%). Despite the increased testing rates, the absolute number of diagnosed HEV infections at Vienna General Hospital remained constant between 2008 to 2018. CONCLUSION: Although approximately half of the patients with severe acute HEV infection required hospitalization, admissions to the intensive care unit (ICU) and short-term mortality were low.

Converting to an international unit system improves harmonization of results for SARS-CoV-2 quantification: Results from multiple external quality assessments.

BACKGROUND: The detection of SARS-CoV-2 vRNA in clinical samples has relied almost exclusively on RT-qPCR as the gold standard test. Published results from various external quality assessments ("ring trials") worldwide have shown that there is still a large variability in results reported for the same samples. As reference standards of SARS-CoV-2 RNA are available, we tested whether using standard curves to convert Ct values into copies/mL (cp/mL) improved harmonization. METHODS: Nine laboratories using 23 test systems (15 of which were unique) prepared standard dilution curves to convert Ct values of 13 SARS-CoV-2 positive samples to cp/mL (hereafter IU/mL). The samples were provided in three rounds of a virus genome detection external quality assessment (EQA) scheme. We tested the precision and accuracy of results reported in IU/mL, and attempted to identify the sources of variability. RESULTS: Reporting results as IU/mL improved the precision of the estimated concentrations of all samples compared to reporting Ct values, although some inaccuracy remained. Variance analysis showed that nearly all variability in data was explained by individual test systems within individual laboratories. When controlling for this effect, there was no significant difference between all other factors tested (test systems, EQA rounds, sample material). CONCLUSIONS: Converting results to copies/mL improved precision across laboratory test systems. However, it seems the results are still very specific to test systems within laboratories. Further efforts could be made to improve accuracy and achieve full harmonization across diagnostic laboratories.

Different Neutralization Profiles After Primary SARS-CoV-2 Omicron BA.1 and BA.2 Infections.

Background and Methods: The SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) Omicron (B.1.1.529) variant is the antigenically most distinct variant to date. As the heavily mutated spike protein enables neutralization escape, we studied serum-neutralizing activities of naïve and vaccinated individuals after Omicron BA.1 or BA.2 sub-lineage infections in live virus neutralization tests with Omicron BA.1, Omicron BA.2, wildtype (WT, B1.1), and Delta (B.1.617.2) strains. Serum samples obtained after WT infections and three-dose mRNA vaccinations with and without prior infection were included as controls. Results: Primary BA.1 infections yielded reduced neutralizing antibody levels against WT, Delta, and Omicron BA.2, while samples from BA.2-infected individuals showed almost no cross-neutralization against the other variants. Serum neutralization of Omicron BA.1 and BA.2 variants was detectable after three-dose mRNA vaccinations, but with reduced titers. Vaccination-breakthrough infections with either Omicron BA.1 or BA.2, however, generated equal cross-neutralizing antibody levels against all SARS-CoV-2 variants tested. Conclusions: Our study demonstrates that although Omicron variants are able to enhance cross-neutralizing antibody levels in pre-immune individuals, primary infections with BA.1 or BA.2 induced mostly variant-specific neutralizing antibodies, emphasizing the differently shaped humoral immunity induced by the two Omicron variants. These data thus contribute substantially to the understanding of antibody responses induced by primary Omicron infections or multiple exposures to different SARS-CoV-2 variants and are of particular importance for developing vaccination strategies in the light of future emerging variants.

Reduced Sensitivity of Commercial Spike-Specific Antibody Assays after Primary Infection with the SARS-CoV-2 Omicron Variant.

The SARS-CoV-2 Omicron variant is characterized by substantial changes in the antigenic structure of the Spike (S) protein. Therefore, antibodies induced by primary Omicron infection lack neutralizing activity against earlier variants. In this study, we analyzed whether these antigenic changes impact the sensitivity of commercial anti-SARS-CoV-2 antibody assays. Sera from 37 unvaccinated, convalescent individuals after putative primary Omicron infection were tested with a panel of 20 commercial anti-SARS-CoV-2 immunoassays. As controls, we used samples from 43 individuals after primary infection with the SARS-CoV-2 ancestral wild-type strain. In addition, variant-specific live-virus neutralization assays were used as a reference for the presence of SARS-CoV-2-specific antibodies in the samples. Notably, in Omicron convalescents, there was a statistically significant reduction in the sensitivity of all antibody assays containing S or its receptor-binding-domain (RBD) as antigens. Furthermore, antibody levels quantified by these assays displayed a weaker correlation with Omicron-specific neutralizing antibody titers than with those against the wild type. In contrast, the sensitivity of nucleocapsid-protein-specific immunoassays was similar in wild-type and Omicron-infected subjects. In summary, the antigenic changes in the Omicron S lead to reduced immunoreactivity in the current commercial S- and RBD-specific antibody assays, impairing their diagnostic performance. IMPORTANCE This study demonstrates that the antigenic changes of the SARS-CoV-2 Omicron variant affect test results from commercial Spike- and RBD-specific antibody assays, significantly diminishing their sensitivities and diagnostic abilities to assess neutralizing antibodies.

The First Case of Usutu Virus Neuroinvasive Disease in Austria, 2021.

Usutu virus (USUV) is a mosquito-borne flavivirus closely related to West Nile virus (WNV) that is endemic in many European countries. We report the first case of USUV neuroinvasive disease in Austria and discuss challenges in differentiating USUV from WNV infections in areas where both viruses are endemic.

Heterogeneous SARS-CoV-2-Neutralizing Activities After Infection and Vaccination.

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) with different resistance levels to existing immunity have recently emerged. Antibodies that recognize the SARS-CoV-2 spike (S) protein and exhibit neutralizing activities are considered the best correlate of protection and an understanding of humoral immunity is crucial for controlling the pandemic. We thus analyzed such antibodies in individuals recovered from infection in 2020 as well as vaccinees after two doses of an mRNA vaccine. Methods: Neutralizing antibody responses against three SARS-CoV-2 variants (D614G, VOCs Beta and Delta) were determined in serum samples from 54 infected individuals (24 non-hospitalized, 30 hospitalized) and 34 vaccinees shortly after symptom onset or second vaccination, respectively, as well as six months later. In addition, the effect of the S sequence of the infecting strain on neutralization was studied. Results: Non-hospitalized patients had the lowest neutralization titers against all variants, while those of hospitalized patients equaled or exceeded those of vaccinees. Neutralizing activity was lower against the two VOCs and declined significantly in all cohorts after six months. This decrease was more pronounced in hospitalized and vaccinated individuals than in non-hospitalized patients. Of note, the specific neutralizing activity (NT titer/ELISA value ratio) was higher in the infected cohorts than in vaccinees and did not differ between non-hospitalized and hospitalized patients. Patients infected with viral strains carrying mutations in the N-terminal domain of the spike protein were impaired in Beta VOC neutralization. Conclusions: Specific neutralizing activities were higher in infected than in vaccinated individuals, and no difference in the quality of these antibodies was observed between hospitalized and non-hospitalized patients, despite significantly lower titers in the latter group. Additionally, antibody responses of infected individuals showed greater heterogeneity than those of vaccinees, which was associated with mutations in the spike protein of the infecting strain. Overall, our findings yielded novel insights into SARS-CoV-2-specific neutralizing antibodies, evolving differently after virus infection and COVID-19 vaccination, which is an important issue to consider in ongoing vaccine strategy improvements.

Response-guided long-term treatment of chronic hepatitis D patients with bulevirtide-results of a "real world" study.

BACKGROUND AND AIM: Bulevirtide (BLV) blocks the uptake of the hepatitis D virus (HDV) into hepatocytes via the sodium/bile acid cotransporter NTCP. BLV was conditionally approved by the EMA but real-life data on BLV efficacy are limited. METHODS: Patients were treated with BLV monotherapy. Patients who did not achieve further decreases in HDV-RNA after 24 weeks were offered PEG-IFN as an add-on therapy in a response-guided manner. RESULTS: Twenty-three patients (m: 10, f: 13; mean age: 47.9 years, cirrhosis: 16; median ALT: 71 IU/ml; median HDV-RNA: 2.1 × 105 copies/ml) started BLV monotherapy (2 mg/day: 22; 10 mg/day: 1). Twenty-two completed ≥24 weeks of treatment (24-137 weeks): Ten (45%) were classified as BLV responders at week 24. BLV was stopped in two patients with >6 months HDV-RNA undetectability, but both became HDV-RNA positive again. One patient was transplanted at week 25. One patient terminated treatment because of side effects at week 60. Ten patients are still on BLV monotherapy. Adding PEG-IFN in eight patients induced an HDV-RNA decrease in all (1.29 ± 0.19 [SD] log within 12 weeks). HDV-RNA decreased by >2log or became undetectable in 45%(10/22), 55%(11/20), 65% (13/20) and 69% (9/13); and ALT levels normalised in 64% (14/22), 85% (17/20), 90% (18/20) and in 92% (12/13) patients at weeks 24, 36, 48 and 60, respectively. Portal pressure decreased in 40% (2/5) of patients undergoing repeated measurement under BLV therapy. CONCLUSION: Long-term BLV monotherapy is safe and effectively decreases HDV-RNA and ALT-even in patients with cirrhosis. The optimal duration of BLV treatment alone or in combination with PEG-IFN remains to be established. An algorithm for a response-guided BLV treatment approach is proposed.