Low impact of regular PCR testing on presence at work site during the COVID-19 pandemic: experiences during an open observational study in Lower Saxony 2020-21.

BACKGROUND: Since social distancing during the COVID-19-pandemic had a profound impact on professional life, this study investigated the effect of PCR testing on on-site work. METHODS: PCR screening, antibody testing, and questionnaires offered to 4,890 working adults in Lower Saxony were accompanied by data collection on demographics, family status, comorbidities, social situation, health-related behavior, and the number of work-related contacts. Relative risks (RR) with 95 % confidence intervals were estimated for the associations between regular PCR testing and other work and health-related variables, respectively, and working on-site. Analyses were stratified by the suitability of work tasks for mobile office. RESULTS: Between April 2020 and February 2021, 1,643 employees underwent PCR testing. Whether mobile working was possible strongly influenced the work behavior. Persons whose work was suitable for mobile office (mobile workers) had a lower probability of working on-site than persons whose work was not suitable for mobile office (RR = 0.09 (95 % CI: 0.07 - 0.12)). In mobile workers, regular PCR-testing was slightly associated with working on-site (RR = 1.19 (0.66; 2.14)). In those whose working place was unsuitable for mobile office, the corresponding RR was 0.94 (0.80; 1.09). Compared to persons without chronic diseases, chronically ill persons worked less often on-site if their workplace was suitable for mobile office (RR = 0.73 (0.40; 1.33)), but even more often if their workplace was not suitable for mobile office (RR = 1.17 (1.04; 1.33)). CONCLUSION: If work was suitable for mobile office, regular PCR-testing did not have a strong effect on presence at the work site. TRIAL REGISTRATION: An ethics vote of the responsible medical association (Lower Saxony, Germany) retrospectively approved the evaluation of the collected subject data in a pseudonymized form in the context of medical studies (No. Bo/30/2020; Bo/31/2020; Bo/32/2020).

Comparison of two antibody screening systems for SARS-CoV-2 antibody detection in recovered and vaccinated subjects - test performance and possible indicators for immunity.

BACKGROUND: Detection of seroconversion after SARS-CoV-2-infection or vaccination is relevant to discover subclinical cases and recognize patients with a possible immunity. OBJECTIVES: Test performance, effects of age, time-point of seroconversion and immune status regarding neutralizing antibodies (NAbs) and T-cell-reactivity were investigated. STUDY DESIGN: Two antibody assays (Viramed-Test for S/N-specific IgG, Roche-Test for N-specific IgA, -M, -G) were evaluated with classified samples. In total, 381 subjects aged 6-99 years, who had either recovered from the disease or had been vaccinated, were screened for SARS-CoV-2-specific antibodies. This screening was part of an open observational study with working adults. Additionally, children and adults were analyzed in a longitudinal COVID-19 study in schools. For immunity evaluation, virus neutralization tests and ELISpot tests were performed in a subgroup of subjects. RESULTS: Viramed revealed a slightly lower test performance than Roche, but test quality was equally well in samples from very young or very old donors. The time-point of seroconversion after the respective immunization detected by the two tests was not significantly different. N-specific antibodies, detected with Roche, highly correlated with NAbs in recovered subjects, whereas a positive Viramed-Test result was paralleled by a positive ELISpot result. CONCLUSION: Viramed-Test was not as sensitive as Roche-Test, but highly specific and beneficial to distinguish between recovered and vaccinated status. For both tests correlations with humoral and cellular immunity were found. Of note, the expected early detection of IgA and IgM by the Roche-Test did not prove to be an advantage over IgG testing by Viramed.

An Antibody-Aptamer-Hybrid Lateral Flow Assay for Detection of CXCL9 in Antibody-Mediated Rejection after Kidney Transplantation.

Chronic antibody-mediated rejection (AMR) is a key limiting factor for the clinical outcome of a kidney transplantation (Ktx), where early diagnosis and therapeutic intervention is needed. This study describes the identification of the biomarker CXC-motif chemokine ligand (CXCL) 9 as an indicator for AMR and presents a new aptamer-antibody-hybrid lateral flow assay (hybrid-LFA) for detection in urine. Biomarker evaluation included two independent cohorts of kidney transplant recipients (KTRs) from a protocol biopsy program and used subgroup comparisons according to BANFF-classifications. Plasma, urine and biopsy lysate samples were analyzed with a Luminex-based multiplex assay. The CXCL9-specific hybrid-LFA was developed based upon a specific rat antibody immobilized on a nitrocellulose-membrane and the coupling of a CXCL9-binding aptamer to gold nanoparticles. LFA performance was assessed according to receiver operating characteristic (ROC) analysis. Among 15 high-scored biomarkers according to a neural network analysis, significantly higher levels of CXCL9 were found in plasma and urine and biopsy lysates of KTRs with biopsy-proven AMR. The newly developed hybrid-LFA reached a sensitivity and specificity of 71% and an AUC of 0.79 for CXCL9. This point-of-care-test (POCT) improves early diagnosis-making in AMR after Ktx, especially in KTRs with undetermined status of donor-specific HLA-antibodies.

Combined Prospective Seroconversion and PCR Data of Selected Cohorts Indicate a High Rate of Subclinical SARS-CoV-2 Infections-an Open Observational Study in Lower Saxony, Germany.

Despite lockdown measures, intense symptom-based PCR, and antigen testing, the SARS-CoV-2 pandemic spread further. In this open observational study conducted in Lower Saxony, Germany, voluntary SARS-CoV-2 PCR tests were performed from April 2020 until June 2021, supported by serum antibody testing to prove whether PCR testing in subjects with none or few symptoms of COVID-19 is a suitable tool to manage the pandemic. In different mobile stations, 4,817 subjects from three different working fields participated in the PCR testing. Serum antibody screening using the SARS-CoV-2 ViraChip IgG (Viramed, Germany) and the Elecsys Anti-SARS-CoV-2 assay (Roche, Germany) was performed alongside virus neutralization testing. Subjects were questioned regarding comorbidities and COVID-19 symptoms. Fifty-one subjects with acute SARS-CoV-2 infection were detected of which 31 subjects did not show any symptoms possibly characteristic for COVID-19. An additional 37 subjects reported a previous SARS-CoV-2 infection (total prevalence 1.82%). Seroconversion was discovered in 58 subjects with known SARS-CoV-2 infection and in 58 subjects that never had a positive PCR test. The latter had a significantly lower Charlson Comorbidity Index, and one third of them were asymptomatic. In 50% of all seroconverted subjects, neutralizing serum antibodies (NAbs) were detectable in parallel to N/S1 (n = 16) or N/S1/S2 antigen specific antibodies (n = 40) against SARS-CoV-2. NAb titers decreased within 100 days after PCR-confirmed SARS-CoV-2 acute infection by at least 2.5-fold. A relatively high rate of subclinical SARS-CoV-2 infections may contribute to the spread of SARS-CoV-2, suggesting that in addition to other intervention strategies, systematic screening of asymptomatic persons by PCR testing may significantly enable better pandemic control. IMPORTANCE Within this open observational study, repeated PCR (n > 4,700) and antibody screening (n > 1,600) tests were offered in three different working fields. The study identified 51 subjects with acute SARS-CoV-2 infection and 37 subjects reported to have had a positive PCR test taken externally. Thirty-one of the 51 subjects did not display any symptoms prior to testing. In addition, 58 subjects without PCR-confirmed SARS-CoV-2 infection were identified by seroconversion. Subjects, that had undergone SARS-CoV-2 infection without having noticed, more often had a low grade of immunization with no NAbs, but may have relevantly contributed to the spread of the pandemic. Based on these results, we suggest that both regular PCR and rapid test screening of symptomatic and asymptomatic individuals, specifically within groups or workplaces identifiable as having close quarter contact, thus increased infection transference risk, is necessary to better assess and therefore reduce the spread of a pandemic virus.

A new lateral flow assay to detect sIL-2R during T-cell mediated rejection after kidney transplantation.

Kidney is the most frequently transplanted among all solid organs worldwide. Kidney transplant recipients (KTRs) undergo regular follow-up examinations for the early detection of acute rejections. The gold standard for proving a T-cell mediated rejection (TCMR) is a biopsy of the renal graft often occurring as indication biopsy, in parallel to an increased serum creatinine that may indicate deterioration of renal transplant function. The goal of the current work was to establish a lateral flow assay (LFA) for diagnosing acute TCMR to avoid harmful, invasive biopsies. Soluble interleukin-2 (IL-2) receptor (sIl-2R) is a potential biomarker representing the α-subunit of the IL-2 receptor produced by activated T-cells, e.g., after allogen contact. To explore the diagnostic potential of sIL-2R as a biomarker for TCMR and borderline TCMR, plasma and urine samples were collected from three independent KTR cohorts with various distinct histopathological diagnostic findings according to BANFF (containing 112 rsp. 71 rsp. 61 KTRs). Samples were analyzed by a Luminex-based multiplex technique and cut off-ranges were determined. An LFA was established with two specific sIL-2R-antibodies immobilized on a nitrocellulose membrane. A significant association between TCMR, borderline TCMR and sIL-2R in plasma and between TCMR and sIL-2R in urine of KTRs was confirmed using the Mann-Whitney U test. The LFA was tested with sIL-2R-spiked buffer samples establishing a detection limit of 25 pM. The performance of the new LFA was confirmed by analyzing urine samples of the 2nd and 3rd patient cohort with 35 KTRs with biopsy proven TCMRs, 3 KTRs diagnosed with borderline TCMR, 1 mixed AMR/TCMR rsp. AMR/borderline TCMR and 13 control patients with a rejection-free kidney graft proven by protocol biopsies. The new point-of-care assay showed a specificity of 84.6% and sensitivity of 87.5%, and a superior estimated glomerular filtration rate (eGFR) at the time point of biopsy (specificity 30.8%, sensitivity 85%).

Development of an Aptamer-Based Lateral Flow Assay for the Detection of C-Reactive Protein Using Microarray Technology as a Prescreening Platform.

For improved cost-effectiveness and temperature-stability, a ready to use lateral flow assay (LFA) is developed in this work for detecting inflammation/infection biomarker C-reactive protein (CRP) in human patient samples on the basis of aptamers. In prescreening investigations, an aptamer with CRP affinity was immobilized on microarray chips in forward and sandwich formats to optimize assay conditions. We suggest these microarray techniques as a resource-sparing and fast-screening instrument for evaluation of various conditions. The capability of the aptamer to detect CRP was shown. Optimized assay conditions were consequently transferred to the LFA-platform. Here we could demonstrate for the first time an aptamer-based LFA for the detection of CRP in human patient samples in pathologically relevant concentrations. The cutoff for CRP detection is set at 10 mg/L, providing a distinctive "yes" (≥10 mg/L CRP) or "no" (<10 mg/L CRP) answer for the patient. The resulting aptamer-based LFA is promising with regard to its application as point-of-care testing (POCT) for efficient monitoring, especially of patients affected by frequent infections or inflammations.