Correlation between SARS-COV-2 antibody screening by immunoassay and neutralizing antibody testing.

BACKGROUND: The efficacy of convalescent plasma (CP), an alternative for the treatment of COVID-19, depends on high titers of neutralizing antibodies (nAbs), but assays for quantifying nAbs are not widely available. Our goal was to develop a strategy to predict high titers of nAbs based on the results of anti-SARS-CoV-2 immunoassays and the clinical characteristics of CP donors. STUDY DESIGN AND METHODS: A total of 214 CP donors were enrolled and tested for the presence of anti-SARS-CoV-2 antibodies (IgG) using two commercial immunoassays: EUROIMMUN (ELISA) and Abbott (Chemiluminescence). Quantification of nAbs was performed using the Cytopathic Effect-based Virus Neutralization test. Three criteria for identifying donors with nAbs ≥ 1:160 were tested: - C1: Curve ROC; - C2: Conditional decision tree considering only the IA results and - C3: Conditional decision tree including both the IA results and the clinical variables. RESULTS: The performance of the immunoassays was similar referring to both S/CO and predictive value for identifying nAbs titers ≥1:160. Regarding the studied criteria for identifying CP donors with high nAbs titers: (a) C1 showed 76.1% accuracy if S/CO = 4.65, (b) C2 presented 76.1% accuracy if S/CO ≥4.57 and (c) C3 had 71.6% accuracy if S/CO was ≥4.57 or if S/CO was between 2.68-4.57 and the last COVID-19-related symptoms were recent (within 19 days). CONCLUSION: SARS-CoV-2 IgG immunoassays (S/CO) can be used to predict high anti-SARS-CoV-2 nAbs titers. This study has proposed different criteria for identifying donors with ≥1:160 nAbs titers, all with high efficacy.

Epstein-Barr Viral Load is Associated to Response in AIDS-Related Lymphomas.

AIDS-related lymphoma (ARL) development is associated to immunodeficiency state with proliferation of B-cells driven by HIV itself and EBV infection. However, Epstein-Barr DNA is not detected in malignant cells of all ARL subtypes. A prospective and controlled study to analyze EBV viral load (VL) in plasma and peripheral blood mononuclear cells (PBMC) of ARL patients was performed to analyze if Epstein-Barr VL could be related to response in these patients. Fifteen patients with ARL were included in this study with measurement of EBV VL at three different periods of time: at lymphoma diagnosis, upon completion of chemotherapy, and 3 months after. Two control groups composed by HIV-negative and HIV-positive patients were also evaluated for EBV VL comparison. In situ hybridization for EBER was performed on diagnostic samples of all ARL patients. Median EBV VL in PBMC and plasma had a significant decrease (p = 0.022 and p = 0.003, respectively) after ARL treatment. EBER was positive in 7 (46.7 %) cases. Median EBV VL in PBMC before lymphoma treatment in patients positive for EBER was significantly higher compared to EBER negative cases (p = 0.041). Reduction of EBV viral load during treatment of lymphoma could be predictive of response. EBER expression was associated to advanced stages of disease and worse immune status. Our study suggests that measurement of EBV VL during ARL treatment could be used as a marker for response, but further studies are needed to validate this association.