Microfluidic Immuno-Serolomic Assay Reveals Systems Level Association with COVID-19 Pathology and Vaccine ProtectionHow to develop highly informative serology assays to evaluate the quality of immune protection against coronavirus disease-19 (COVID-19) has been a global pursuit over the past years. Here, a microfluidic high-plex immuno-serolomic assay is developed to simultaneously measure50 plasma or serum samples for50 soluble markers including 35proteins, 11 anti-spike/receptor binding domian (RBD) IgG antibodies spanningmajor variants, and controls. This assay demonstrates the quintuplicate test in a single run with high throughput, low sample volume, high reproducibilityand accuracy. It is applied to the measurement of 1012 blood samples including in-depth analysis of sera from 127 patients and 21 healthy donors over multiple time points, either with acute COVID infection or vaccination. The protein analysis reveals distinct immune mediator modules that exhibit a reduced degree of diversity in protein-protein cooperation in patients with hematologic malignancies or receiving B cell depletion therapy. Serological analysis identifies that COVID-infected patients with hematologic malignancies display impaired anti-RBD antibody response despite high level of anti-spike IgG, which can be associated with limited clonotype diversity and functional deficiency in B cells. These findings underscore the importance to individualize immunization strategies for these high-risk patients and provide an informative tool to monitor their responses at the systems level.
BSBM-18 SINGLE-CELL PROFILING TUMOR-INFILTRATING IMMUNE CELLS REVEALS CXCL13+ FOLLICULAR HELPER-LIKE CD4+ T CELLS IN HUMAN BRAIN TUMORSWhile therapies enhancing antitumor T cell function have clinical efficacy for patients with brain metastases, patients with high-grade gliomas fail to benefit. How the brain tumor microenvironment differentially shapes T cell function remains unknown. We performed droplet-based single-cell RNA and T cell receptor sequencing on immune cells from tumor and blood of patients with newly diagnosed non-small cell lung cancer brain metastases (n=10) and high-grade glioma (n=12). In total, we examined 220,049 high-quality immune cells, including 159,043 T cells. Tumor-infiltrating T cells in metastases were more abundant (p=0.005), more clonally expanded (p=0.039), and had a less diverse clonal repertoire (p=0.033). While no differences were observed among CD8+ T cells, a population of CXCL13+CD4+ T cells was more abundant in metastases (6.03% vs. 1.82%, p=0.004). This population expressed genes encoding transcriptional factors (BCL6, MAF), co-inhibitory receptors (PDCD1, LAG3, TIGIT), and effector cytokines (IL21, IL4, IFNG) characteristic of follicular helper T cells though notably lacked expression for the canonical chemokine receptor CXCR5. CXCL13+CD4+ T cells were highly expanded, had minimal clonal overlap with other populations, largely confined to the tumor, associated with germinal center B cell and plasma cell signatures, and resembled T cell populations predictive of anti-PD-1 therapy response in extracranial disease. Based on the expression of potential ligand-receptors and downstream signaling targets, CXCL13+CD4+ T cells were predicted to interact with B cells and antigen-presenting cells, as seen in tertiary lymphoid structures. To investigate the relevance of CXCL13+CD4+ T cells in glioblastoma, we analyzed bulk RNA sequencing data from The Cancer Genome Atlas (n=160) and observed a trend towards longer overall survival in patients with high follicular helper-like expression. In summary, we identified a follicular helper-like CD4+ T cell population that is preferentially found in brain metastases and may be a feature of productive antitumor immune responses in human brain tumors.