Potent neutralizing antibodies from COVID-19 patients define multiple targets of vulnerability.

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has had a large impact on global health, travel, and economy. Therefore, preventative and therapeutic measures are urgently needed. Here, we isolated monoclonal antibodies from three convalescent coronavirus disease 2019 (COVID-19) patients using a SARS-CoV-2 stabilized prefusion spike protein. These antibodies had low levels of somatic hypermutation and showed a strong enrichment in VH1-69, VH3-30-3, and VH1-24 gene usage. A subset of the antibodies was able to potently inhibit authentic SARS-CoV-2 infection at a concentration as low as 0.007 micrograms per milliliter. Competition and electron microscopy studies illustrate that the SARS-CoV-2 spike protein contains multiple distinct antigenic sites, including several receptor-binding domain (RBD) epitopes as well as non-RBD epitopes. In addition to providing guidance for vaccine design, the antibodies described here are promising candidates for COVID-19 treatment and prevention.

Interpolation method for accurate affinity ranking of arrayed ligand-analyte interactions.

The values of the affinity constants (kd, ka, and KD) that are determined by label-free interaction analysis methods are affected by the ligand density. This article outlines a surface plasmon resonance (SPR) imaging method that yields high-throughput globally fitted affinity ranking values using a 96-plex array. A kinetic titration experiment without a regeneration step has been applied for various coupled antibodies binding to a single antigen. Globally fitted rate (kd and ka) and dissociation equilibrium (KD) constants for various ligand densities and analyte concentrations are exponentially interpolated to the KD at Rmax = 100 RU response level (KD(R100)).

On-chip sample preparation by controlled release of antibodies for simple CD4 counting.

We present a simple system for CD4 and CD8 counting for point-of-care HIV staging in low-resource settings. Automatic sample preparation is achieved through a dried reagent coating inside a thin (26 µm) counting chamber, allowing the delayed release of fluorochrome conjugated monoclonal antibodies after the filling of the chamber with whole blood by capillary flow. A custom-built image cytometer is used to capture fluorescence images representing more than 1 µl of blood. The thin layer of blood in combination with the large image area allows the use of whole blood from a finger prick without the need for dilution, lysis or cell enrichment. Automatic cell counting of CD4(+) and CD8(+) T-lymphocytes correlates well with results obtained by flow cytometry.