SARS-CoV-2 Epitopes Are Recognized by a Public and Diverse Repertoire of Human T Cell Receptors.

Understanding the hallmarks of the immune response to SARS-CoV-2 is critical for fighting the COVID-19 pandemic. We assessed antibody and T cell reactivity in convalescent COVID-19 patients and healthy donors sampled both prior to and during the pandemic. Healthy donors examined during the pandemic exhibited increased numbers of SARS-CoV-2-specific T cells, but no humoral response. Their probable exposure to the virus resulted in either asymptomatic infection without antibody secretion or activation of preexisting immunity. In convalescent patients, we observed a public and diverse T cell response to SARS-CoV-2 epitopes, revealing T cell receptor (TCR) motifs with germline-encoded features. Bulk CD4+ and CD8+ T cell responses to the spike protein were mediated by groups of homologous TCRs, some of them shared across multiple donors. Overall, our results demonstrate that the T cell response to SARS-CoV-2, including the identified set of TCRs, can serve as a useful biomarker for surveying antiviral immunity.

Novel curcumin derivatives as P-glycoprotein inhibitors: Molecular modeling, synthesis and sensitization of multidrug resistant cells to doxorubicin.

The MDR1/P-glycoprotein (Pgp)/ABCB1 multidrug transporter is being investigated as a druggable target for antitumor therapy for decades. The natural product curcumin is known to provide an efficient scaffold for compounds capable of blocking Pgp mediated efflux and sensitization of multidrug resistant (MDR) cells to the Pgp transported drug doxorubicin (Dox). We performed molecular dynamics simulations and docking of curcumin derivatives into the Pgp model. Based on these calculations, a series of pyrazolocurcumin derivatives with predicted metabolic stability and/or improved binding affinity were proposed for synthesis and evaluation of MDR reversal potency against Dox selected K562/4 subline, a derivative of K562 human chronic myelogenous leukemia cell line. Compounds 16 and 19 which are both dimethylcurcumin pyrazole derivatives bearing an N-p-phenylcarboxylic amide substitution, were the most potent Pgp blockers as determined by intracellular Dox accumulation. Furthermore, at non-toxic submicromolar concentrations 16 and 19 dramatically sensitized K562/4 cells to Dox. Together with good water solubility of 16 and 19, these results indicate that the new pyrazolo derivatives of curcumin are a promising scaffold for development of clinically applicable Pgp antagonists.

Protective C allele of the single-nucleotide polymorphism rs1335532 is associated with strong binding of Ascl2 transcription factor and elevated CD58 expression in B-cells.

CD58 is expressed on the surface of antigen-presenting cells, including B-cells, and provides co-stimulation to regulatory T-cells (Treg) through CD2 receptor binding. Tregs appear to be essential suppressors of tissue-specific autoimmune responses. Thereby, CD58 plays protective role in multiple sclerosis (MS) and CD58 was identified among several loci associated with MS susceptibility. Minor (C) variant of the single-nucleotide polymorphism (SNP) rs1335532 is associated with lower MS risk according to genome-wide association studies (GWAS) and its presence correlates with higher CD58 mRNA levels in MS patients. We found that genomic region containing rs1335532 has enhancer properties and can significantly boost the CD58 promoter activity in lymphoblast cells. Using bioinformatics and pull-down assay we found that the protective (C) rs1335532 allele created functional binding site for ASCL2 transcription factor, a target of the Wnt signaling pathway. Both in B-lymphoblastoid cell lines and in primary B-cells, as well as in a monocytic cell line, activation of Wnt signaling resulted in an increased CD58 promoter activity in the presence of the protective but not the risk allele of rs1335532, whereas ASCL2 knockdown abrogated this effect. In summary, our results suggest that ASCL2 mediates the protective function of rs1335532 minor (C) allele in MS.

Immune selection of tumor cells in TCR ß-chain transgenic mice.

The concept of immunological surveillance implies that immunogenic variants of tumor cells arising in the organism can be recognized by the immune system. Tumor progression is provided by somatic evolution of tumor cells under the pressure of the immune system. The loss of MHC Class I molecules on the surface of tumor cells is one of the most known outcomes of immune selection. This study developed a model of immune selection based on the immune response of TCR 1d1 single ß-chain transgenic B10.D2(R101) (K(d)I(d)D(b)) mice to allogeneic EL4 (H-2(b)) thymoma cells. In wild-type B10.D2(R101) mice, immunization with EL4 cells induced a vigorous CTL response targeted to the H-2K(b) molecule and results in full rejection of the tumor cells. In contrast, transgenic mice developed a compromised proliferative response in mixed-lymphocyte response assays and were unable to reject transplanted allogeneic EL4 cells. During the immune response to EL4 cells, CD8(+) T-lymphocytes with endogenous ß-chains accumulated predominantly in the spleen of transgenic mice and only a small part of the T-lymphocytes expressing transgenic ß-chains became CD8(+)CD44(+)CD62L(-) effectors. Then, instead of a full elimination of tumor cells as in wild-type mice, a reproducible prolonged equilibrium phase and subsequent escape was observed in transgenic mice that resulted in death of 90% of the mice in 40-60 days after grafting. Prolonged exposure of tumor cells to the pressure of the immune system in transgenic mice in vivo resulted in a stable loss of H-2K(b) molecules on the EL4 cell surface. Genetic manipulation of the T-lymphocyte repertoire was sufficient to reproduce the classic pattern of interactions between tumor cells and the immune system, usually observed in reliable syngeneic models of anti-tumor immunity. This newly-developed model could be used in further studies of immunoregulatory circuits common for transplantational and anti-tumor immune responses.