SARS-CoV-2 (COVID-19)-specific T cell and B cell responses in convalescent rheumatoid arthritis: Monozygotic twins pair case observation.

Rheumatoid arthritis (RA) patients present higher risk of SARS-CoV-2 infection (COVID-19), and proper management of the disease in this population requires a better understanding of how the immune system controls the virus. We analyzed the T cell and B cell phenotypes, and their repertoire in a pair of monozygotic twins with RA mismatched for COVID-19 infection. Twin- was not infected, while Twin+ was infected and effectively controlled the infection. We found no significant changes on the αß T cell composition, while γδ T cells and B cells presented considerable expansion of memory population in Twin+ and robust T/B cell responses to several SARS-CoV-2 peptides. T cell receptor ß/γ-chain and immunoglobulin heavy chain next-generation sequencing depicted a remarkable higher diversity in Twin+ compared with Twin-, despite no significant changes being found in variable/joining family usage. Repertoire overlap analyses showed that, although being identical twins, very few clones were shared between them, indicating that COVID-19 may lead to deep changes on the immune cell repertoire in RA patients. Altogether, our results indicate that RA patients may develop robust and persistent COVID-19-specific T/B cell responses; γδ T cells and B cells may play a key role in the management of COVID-19 in RA, and the infection may lead to a profound reshaping of immune cell receptor specificities.

Using PBMCs in a Multiplex FluoroSpot Assay for Detection of Innate Immune Response-Modulating Impurities (IIRMIs).

The ELISA-based monocyte activation test (MAT) facilitates the replacement of the rabbit pyrogen test (RPT) for the detection of Innate Immune Response-Modulating Impurities (IIRMIs) in injectable drugs by activation of monocytes in human peripheral blood mononuclear cells (PBMCs). We describe the use of a triple-color IL-1ß/IL-6/TNF-α FluoroSpot assay as a sensitive tool for quantification of the frequencies of IIRMI-activated monocytes as well as determination of the relative amount of pyrogenic cytokine(s) produced by each activated cell.

Triple-Color FluoroSpot Analysis of Polyfunctional Antigen-Specific T Cells by Quantification of Spot-Forming Units and Relative Spot Volumes.

Switching from ELISpot to FluoroSpot enables the analysis of spot-forming units representing cells producing different cytokines as well as the frequencies of spots derived from cells co-secreting multiple cytokines. Due to the fluorescent read-out signal, sophisticated reader instruments can also measure the relative spot volume, making it possible to differentiate between spots generated by cells secreting different levels of one or more cytokines. Here we describe how triple FluoroSpot assays can be used to define polyfunctional T cells secreting multiple cytokines and how different T-cell populations can differ in the levels of cytokines they secrete.

Multiplex analysis of antigen-specific memory B cells in humans using reversed B-cell FluoroSpot.

Analysis of B-cell specificities at the single cell level provides important information on how the B-cell compartment responds when challenged by infection or vaccination. We recently developed a reversed B-cell FluoroSpot assay and showed that it could be used to detect B cells specific for different antigens simultaneously in a mouse model. The aim of this study was to further develop the method to detect and quantify antigen-specific memory B cells (MBCs) in humans where circulating antigen-specific cells are less frequent. We show that MBCs specific for three antigens, tetanus toxoid, hepatitis B surface antigen and cytomegalovirus pp65, could be detected simultaneously in one well. In addition to enumerating antigen-specific MBCs, we also assessed the spot volume to estimate the intensity of the response in individual cells and found this to be a new and sensitive approach to study MBC responses after vaccination. This unique B-cell FluoroSpot approach provides a simple and sensitive multiplex analysis of MBCs and can be adapted to most antigens and host species.