ABSTRACT SARS-CoV-2 spreads pandemically since 2020; in 2021, effective vaccinations became available and vaccination campaigns commenced. Still, it is hard to track the spread of the infection or to assess vaccination success in the broader population. Measuring specific anti-SARS-CoV-2 antibodies is the most effective tool to track the spread of the infection or successful vaccinations. The need for venous-blood sampling however poses a significant barrier for large studies. Dried-blood-spots on filter-cards (DBS) have been used for SARS-CoV-2 serology in our laboratory, but so far not to follow quantitative SARS-CoV-2 anti-spike reactivity in a longitudinal cohort. We developed a semi-automated protocol or quantitative SARS-CoV-2 anti-spike serology from self-sampled DBS, validating it in a cohort of matched DBS and venous-blood samples ( n = 825). We investigated chromatographic effects, reproducibility, and carry-over effects and calculated a positivity threshold as well as a conversion formula to determine the quantitative binding units in the DBS with confidence intervals. Sensitivity and specificity reached 96.63% and 97.81%, respectively, compared to the same test performed in paired venous samples. Between a signal of 0.018 and 250 U/mL, we calculated a correction formula. Measuring longitudinal samples during vaccinations, we demonstrated relative changes in titers over time in several individuals and in a longitudinal cohort over four follow-ups. DBS sampling has proven itself for anti-nucleocapsid serosurveys in our laboratory. Similarly, anti-spike high-throughput DBS serology is feasible as a complementary assay. Quantitative measurements are accurate enough to follow titer dynamics in populations also after vaccination campaigns. This work was supported by the Bavarian State Ministry of Science and the Arts; LMU University Hospital, LMU Munich; Helmholtz Center Munich; University of Bonn; University of Bielefeld; German Ministry for Education and Research (proj. nr.: 01KI20271 and others) and the Medical Biodefense Research Program of the Bundeswehr Medical Service. Roche Diagnostics provided kits and machines for analyses at discounted rates. The project is funded also by the European-wide Consortium ORCHESTRA. The ORCHESTRA project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101016167. The views expressed in this publication are the sole responsibility of the author, and the Commission is not responsible for any use that may be made of the information it contains. IMPORTANCE SARS-CoV-2 has been spreading globally as a pandemic since 2020. To determine the prevalence of SARS-CoV-2 antibodies among populations, the most effective public health tool is measuring specific anti-SARS-CoV-2 antibodies induced by infection or vaccination. However, conducting large-scale studies that involve venous-blood sampling is challenging due to the associated feasibility and cost issues. A more cost-efficient and less invasive method for SARS-CoV-2 serological testing is using Dried-Blood-Spots on filter cards (DBS). In this paper, we have developed a semi-automated protocol for quantifying SARS-CoV-2 anti-spike antibodies from self-collected DBS. Our laboratory has previously successfully used DBS sampling for anti-nucleocapsid antibody surveys. Likewise, conducting high-throughput DBS serology for anti-spike antibodies is feasible as an additional test that can be performed using the same sample preparation as the anti-nucleocapsid analysis. The quantitative measurements obtained are accurate enough to track the dynamics of antibody levels in populations, even after vaccination campaigns.
Background Childhood tuberculosis (TB) remains underdiagnosed. The novel lateral flow FujiLAM assay detects lipoarabinomannan (LAM) in urine, but data on performance in children remain limited. Methods We conducted a systematic review assessing the diagnostic performance of FujiLAM for diagnosing paediatric TB. The last search was conducted in November 2021. Results We included three studies with data from 698 children for FujiLAM. For FujiLAM, sensitivity using a microbiological reference standard were 60% (95% CI 15 to 95), 42% (95% CI 31 to 53) and 63% (95% CI 50 to 75), respectively. Specificity was 93% (95% CI 85 to 98), 92% (95% CI 85 to 96) and 84% (95% CI 80 to 88). Using a composite reference standard, sensitivity was 11% (95% CI 4 to 22), 27% (95% CI 20 to 34) and 33% (95% CI 26 to 40), and specificity was 92% (95% CI 73 to 99), 97% (95% CI 87 to 100) and 85% (95% CI 79 to 89). Subgroup analyses for sensitivity of FujiLAM in children living with HIV (CLHIV) compared with those who were negative for HIV infection were inconsistent across studies. Among CLHIV, sensitivity appeared higher in those with greater immunosuppression, although wide CIs limit the interpretation of observed differences. Meta-analysis was not performed due to considerable study heterogeneity. Conclusion The high specificity of FujiLAM demonstrates its potential as a point-of-care (POC) rule-in test for diagnosing paediatric TB. As an instrument-free POC test that uses an easy-to-obtain specimen, FujiLAM could significantly improve TB diagnosis in children in low-resource settings, however the small number of studies available highlight that further data are needed. Key priorities to be addressed in forthcoming paediatric evaluations include prospective head-to-head comparisons with AlereLAM using fresh specimens, specific subgroup analysis in CLHIV and extrapulmonary disease and studies in different geographical locations. CRD42021270761.
Abstract Despite intensive research since the emergence of SARS-CoV-2, it has remained unclear precisely which components of the early immune response protect against the development of severe COVID-19. Here, we perform a comprehensive immunogenetic and virologic analysis of nasopharyngeal and peripheral blood samples obtained during the acute phase of infection with SARS-CoV-2. We find that soluble and transcriptional markers of systemic inflammation peak during the first week after symptom onset and correlate directly with upper airways viral loads (UA-VLs), whereas the contemporaneous frequencies of circulating viral nucleocapsid (NC)-specific CD4 + and CD8 + T cells correlate inversely with various inflammatory markers and UA-VLs. In addition, we show that high frequencies of activated CD4 + and CD8 + T cells are present in acutely infected nasopharyngeal tissue, many of which express genes encoding various effector molecules, such as cytotoxic proteins and IFN-γ. The presence of IFNG mRNA-expressing CD4 + and CD8 + T cells in the infected epithelium is further linked with common patterns of gene expression among virus-susceptible target cells and better local control of SARS-CoV-2. Collectively, these results identify an immune correlate of protection against SARS-CoV-2, which could inform the development of more effective vaccines to combat the acute and chronic illnesses attributable to COVID-19.
Population-based serological studies allow to estimate prevalence of SARS-CoV-2 infections despite a substantial number of mild or asymptomatic disease courses. This became even more relevant for decision making after vaccination started. The KoCo19 cohort tracks the pandemic progress in the Munich general population for over two years, setting it apart in Europe.Recruitment occurred during the initial pandemic wave, including 5313 participants above 13 years from private households in Munich. Four follow-ups were held at crucial times of the pandemic, with response rates of at least 70%. Participants filled questionnaires on socio-demographics and potential risk factors of infection. From Follow-up 2, information on SARS-CoV-2 vaccination was added. SARS-CoV-2 antibody status was measured using the Roche Elecsys® Anti-SARS-CoV-2 anti-N assay (indicating previous infection) and the Roche Elecsys® Anti-SARS-CoV-2 anti-S assay (indicating previous infection and/or vaccination). This allowed us to distinguish between sources of acquired antibodies.The SARS-CoV-2 estimated cumulative sero-prevalence increased from 1.6% (1.1-2.1%) in May 2020 to 14.5% (12.7-16.2%) in November 2021. Underreporting with respect to official numbers fluctuated with testing policies and capacities, becoming a factor of more than two during the second half of 2021. Simultaneously, the vaccination campaign against the SARS-CoV-2 virus increased the percentage of the Munich population having antibodies, with 86.8% (85.5-87.9%) having developed anti-S and/or anti-N in November 2021. Incidence rates for infections after (BTI) and without previous vaccination (INS) differed (ratio INS/BTI of 2.1, 0.7-3.6). However, the prevalence of infections was higher in the non-vaccinated population than in the vaccinated one. Considering the whole follow-up time, being born outside Germany, working in a high-risk job and living area per inhabitant were identified as risk factors for infection, while other socio-demographic and health-related variables were not. Although we obtained significant within-household clustering of SARS-CoV-2 cases, no further geospatial clustering was found.Vaccination increased the coverage of the Munich population presenting SARS-CoV-2 antibodies, but breakthrough infections contribute to community spread. As underreporting stays relevant over time, infections can go undetected, so non-pharmaceutical measures are crucial, particularly for highly contagious strains like Omicron.
Abstract Vaccine breakthrough infections with SARS-CoV-2 Omicron induced a higher level of protection compared to triple vaccination and contributed to herd immunity on a population level. To address the underlying immunological mechanisms, we studied the evolution of SARS-CoV-2-specific antibody and Tcell responses during vaccination and upon breakthrough infection in Bavarian residents between February 2021 and December 2022. Further, we investigated the temporal distance between completed vaccination and break-through infection, as well as any occurring re-infection. Each vaccination significantly increased peak neutralization titers against Wuhan, Delta, and Omicron BA.5 with simultaneous increases in circulating spike-specific Tcell frequencies. After vaccination, Omicron BA.5 neutralization titers were most significantly associated with a reduced hazard rate for SARS-CoV-2 infection, also when accounting for spikespecific Tcell responses. Yet, 97% of triple vaccinees became SARS-CoV-2 infected, often within a few months after their third vaccination. Breakthrough infections further boosted neutralization magnitude and breadth, broadened virusspecific Tcell responses to non-vaccine-encoded antigens and protected with an efficiency of 88% from further infections by December 2022. This effect was then assessed by utilizing mathematical modelling, which accounted for time-dependent infection risk in Bavaria, as well as the antibody and Tcell concentration at any time point after breakthrough infection. Our findings suggest that cross-variant protective hybrid immunity induced by vaccination and breakthrough infection was an important contributor to the reduced virus transmission observed in Bavaria in late 2022 and thereafter.
Risk factors for disease progression and severity of SARS-CoV-2 infections require an understanding of acute and long-term virological and immunological dynamics. Fifty-one RT-PCR positive COVID-19 outpatients were recruited between May and December 2020 in Munich, Germany, and followed up at multiple defined timepoints for up to one year. RT-PCR and viral culture were performed and seroresponses measured. Participants were classified applying the WHO clinical progression scale. Short symptom to test time (median 5.0 days; p = 0.0016) and high viral loads (VL; median maximum VL: 3∙10
Abstract Despite intensive research since the emergence of SARS-CoV-2, it has remained unclear precisely which components of the early immune response protect against the development of severe COVID-19. To address this issue, we performed a comprehensive immunogenetic and virologic analysis of nasopharyngeal and peripheral blood samples obtained during the acute phase of infection with SARS-CoV-2. We found that soluble and transcriptional markers of systemic inflammation peaked during the first week after symptom onset and correlated directly with the upper airways viral loads (UA-VLs), whereas the contemporaneous frequencies of circulating viral nucleocapsid (NC)-specific CD4+ and CD8+ T cells correlated inversely with various inflammatory markers and UA-VLs. In addition, we observed high frequencies of activated CD4+ and CD8+ T cells in acutely infected nasopharyngeal tissue, many of which expressed genes encoding various effector molecules, such as cytotoxic proteins and IFN-γ. The presence of functionally active T cells in the infected epithelium was further linked with common patterns of gene expression among virus-susceptible target cells and better local control of SARS-CoV-2. Collectively, these results identified an immune correlate of protection against SARS-CoV-2, which could inform the development of more effective vaccines to combat the acute and chronic illnesses attributable to COVID-19.
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