Objectives Accurate SARS-CoV-2 serological assays are urgently needed to help diagnose infection, determine past exposure of populations and assess the response to future vaccines. The study aims at assessing the performance of the multiplex D-tek COVIDOT 5 IgG assay for the detection of SARS-CoV-2 IgG antibodies (N, S1+S2, S1, S2 and RBD). Methods Sensitivity and dynamic trend to seropositivity were evaluated in 218 samples obtained from 46 rRT-PCR confirmed COVID-19 patients. Non-SARS-CoV-2 sera (n=118) collected before the COVID-19 pandemic with a potential cross-reaction to the SARS-CoV-2 immunoassay were included in the specificity analysis. Results A gradual dynamic trend since symptom onset was observed for all IgG antibodies. Sensitivities before day 14 were suboptimal. At ≥21 days, sensitivities reached 100% (93.4–100%) for N, S1+S2, S2 and RBD-directed IgG and 96.3% (87.3–99.6%) for S1-directed IgG. In 42 out of 46 patients (91.3%), all five antibodies were detected at ≥14 days. The four remaining patients had between 2 and 4 positive antibodies at their respective maximal follow-up period. The specificity was 100 % for S1+S2, S2 and RBD, 98.3% for N and 92.4% (86.0–96.5%) for S1-directed IgG. The combined use of antigens increases the early sensitivity whilst enforcing high specificity. Conclusions Sensitivities at ≥21 days and specificities were excellent, especially for N, S1+S2, S2 and RBD-directed IgG. Caution is however required when interpreting single S1-directed reactivities. Using a multiplex assay complies with the orthogonal testing algorithm of the CDC and allows a better and critical interpretation of the serological status of a patient.

SummaryHuman apolipoprotein L1 (APOL1) kills African trypanosomes except Trypanosoma rhodesiense and Trypanosoma gambiense, the parasites causing sleeping sickness. APOL1 uptake into trypanosomes is favoured by its association with the haptoglobinrelated protein-haemoglobin complex, which binds to the parasite surface receptor for haptoglobinhaemoglobin. As haptoglobin-haemoglobin can saturate the receptor, APOL1 uptake is increased in haptoglobin-poor (hypohaptoglobinaemic) serum (HyHS). While T. rhodesiense resists APOL1 by RNA polymerase I (pol-I)-mediated expression of the serum resistance-associated (SRA) protein, T. gambiense resists by pol-II-mediated expression of the T. gambiense-specific glycoprotein (TgsGP). Moreover, in T. gambiense resistance to HyHS is linked to haptoglobin-haemoglobin receptor inactivation by mutation. We report that unlike T. gambiense, T. rhodesiense possesses a functional haptoglobinhaemoglobin receptor, and that like T. gambiense experimentally provided with active receptor, this parasite is killed in HyHS because of receptormediated APOL1 uptake. However, T. rhodesiense could adapt to low haptoglobin by increasing transcription of SRA. When assayed in Trypanosoma brucei, resistance to HyHS occurred with pol-I-, but not with pol-II-mediated SRA expression. Similarly, T. gambiense provided with active receptor acquired resistance to HyHS only when TgsGP was moved to a pol-I locus. Thus, transcription by pol-I favours adaptive gene regulation, explaining the presence of SRA in a pol-I locus.

No abstract

No abstract

Background We report on sample IS/17575 since it generated highly divergent results in the Belgian SARS-CoV-2 serology EQA scheme. Materials and methods Sample IS/17575 was serum originating from a 30 years old male patient. 124 diagnostic laboratories analysed this sample. Results A total of 168 results was returned (including 5 doubles). Overall, 38 were positive. All tests against S1 were positive except the Euroimmun IgG ELISA and the Ortho clinical Diagnostics VITROS IgG CLIA. All tests against S1/S2 (Liaison, Diasorin) resulted in a signal above cutoff. Assays against RBD, mostly generate a negative result. An exception are the Wantai SARS-CoV-2 ELISA's. All tests targeting N protein were negative. Conclusion The survey shows, when > 6 months post-infection, assays targeting at least S1, and preferably S1 combined with S2, are the most sensitive. This finding accentuates the necessity of EQA schedules and antigenic composition of serologic SARS-CoV-2 assays.

The optimal thromboprophylactic strategy for patients affected by Coronavirus disease 2019 (COVID-19) has been debated among experts. This study evaluated the safety and efficacy of a thromboprophylaxis algorithm. This was a retrospective, single-center study in critically ill patients admitted to the intensive care unit (University affiliated Hospital) for acute respiratory failure due to Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2). From March 16 to April 9, 2020, thromboprophylaxis was adjusted according to weight (control group, n = 19) and after this date, thromboprophylaxis depended on an algorithm based on thrombotic and hemorrhagic risk factors (protocol group, n = 13). With regard to safety (number of major bleeding events and blood transfusions), the groups were not significantly different. With regard to efficacy, the number of thrombotic events decreased from 37 to 0%, p = 0.025 after implementation of the algorithm. Also, peak fibrinogen dropped from 8.6 (7.2–9.3) to 6.5 (4.6–8.4) g/L, p = 0.041 and D-dimers from 2194 (1464–3763) to 1486 (900–2582) ng/mL, p = 0.0001. In addition, length of stay declined from 19 (10–31) to 5 (3–19) days, p = 0.009. In conclusion, a tailored thromboprophylaxis algorithm (risk stratification based on clinical parameters and biological markers) reduce thrombotic phenomena in critically ill COVID-19 patients without increasing major bleeding. Supplementary Information The online version of this article (10.1007/s11239-021-02514-3) contains supplementary material, which is available to authorized users.

Objective Patients and physicians are increasingly requesting their clinical laboratory to provide SARS-CoV-2 serology interpretation. Our study aimed to assess the evolution of SARS-CoV-2 antibodies in Moderna-vaccinated health care workers. Methods We analyzed the evolution of mRNA-1273 (Moderna)–elicited antibodies by 2 high-throughput assays, TrimericS IgG (Diasorin) and SARS-CoV-2 IgG-II (Abbott). Results After the first injection, the COVID-19–recovered vaccinees showed a serological response as strong as that observed 1 month after the second injection in participants without COVID-19 history. Although remaining above the positivity thresholds, the TrimericS immunoglobulin G (IgG) and anti-RBD (receptor-binding domain) IgG levels fell considerably between 1 and 7 months postvaccination, dropping to 10.6% and 13% for the COVID-19 recovered subgroup and to 11.7% and 9.3% for the COVID-19 naive subgroup. Conclusion Regardless of the test used, a decrease in circulating anti-SARS-CoV-2 IgG levels should be expected a few months after vaccination. As this decline does not preclude the efficacy of immune response, caution is necessary when interpretating postvaccination serological data.

5190 Objectives: Definition of the primary antibodies panel for 10 colours flow cytometry able to describe normal and clonal T, B lymphocytes and plamocytes in blood and bone marrow. Once clonalities are detected, the complete characterisation of Chronic Lymphoproliferative Diseases (CLPD) is supported by secondary panels chosen based on the results of CD5/CD10 expression for clonal B lymphocytes, CD27/CD38 for plasmatocytes and CD3/CD27 for clonal T cells. Materials and Methods: Blood and bone marrow of patients (N=50) with CLPD (mainly B-CLL). Samples are enumerated by haematology analyzer DxH 800 then 106 cells are washed three times, stained with the antibodies combination and red blood cells lysed with Versalyse (TM. Beckman Coulter). The samples were analysed on a 10 colours Navios flow cytometer (Beckman Coulter Fullerton, CA). The staining panel consists of 14 antibodies (CD45, CD8, CD4, CD5, CD3, CD19, CD38, λ, κ, CD23, CD5, CD10, CD14, CD27) conjugated with 10 different fluorochromes. The fixed gating strategy allows linking Navios analysis software to the middleware Remisol which drives the choice of the secondary panel. In some cases a third tube is performed for Ki67 or Zap-70 intra-cytoplasmic staining. Results: Monocytes are removed on the basis of their CD14/CD4 expression. B lymphocytes are CD19 positive. Normal naïve/memory B cells, hematogones and plasma cells are defined by their CD27, CD10 and CD38 expression. Eventual monoclonality is sought by analysis of the distribution of Kappa and Lambda light chains. A first classification of B cell lymphoma is achieved with the CD5 and CD10 expression of the clone (CD5+/CD10−: B-CLL MCL and few MZL, CD5−/CD10−: MZL and related, CD5−/CD10+ DLBCL and FL). Analysis of CD27, CD20 and CD23 expression allows discriminating between CD5+/CD10- lymphomas. All the 50 samples were correctly detected as CLPD and the automated Remisol choice of the second panel fit to the final diagnosis of all the cases of this small series. T lymphocytes are defined by their CD3 and CD5 expression. The analysis of CD4/CD8 balance and CD27/CD5 distribution are first line test when T cell clonality is suspected. There is a special gating to detect CD3-CD4+ T cell lymphoma and double negativity of CD4 and CD8 is a surrogate marker for gamma/delta T cells. NK cells are mentioned as not-T not-B lymphocytes, without specific staining. Conclusion/Discussion:This 10 colours 14 antibodies panel allows describing in one tube normal T and B cells, hematogones, memory and naives B cells plasma cells and detects T and B clonalities. This panel follows a similar logic than the Euroflow LST tube but with 10 colours and with Beckman Coulter's technology and antibodies. Moreover, this combination helps discriminating rapidly the CD5+/CD10- lymphomas while the complete characterisation of CD5 negative lymphomas only require less than 6 antibodies second tube. This is a paperless (all the process is driven and controlled by Remisol), fast and inexpensive diagnostic approach (always less than 20 antibodies required). Disclosures: Pradier: Beckman Coulter: Consultancy, Membership on an entity's Board of Directors or advisory committees.