Detection and Enumeration of Cytokine-Secreting Cells by FluoroSpot

Deciphering cellular complexity: advances and future directions in single-cell protein analysis

Single-cell protein analysis has emerged as a powerful tool for understanding cellular heterogeneity and deciphering the complex mechanisms governing cellular function and fate. This review provides a comprehensive examination of the latest methodologies, including sophisticated cell isolation techniques (Fluorescence-Activated Cell Sorting (FACS), Magnetic-Activated Cell Sorting (MACS), Laser Capture Microdissection (LCM), manual cell picking, and microfluidics) and advanced approaches for protein profiling and protein-protein interaction analysis. The unique strengths, limitations, and opportunities of each method are discussed, along with their contributions to unraveling gene regulatory networks, cellular states, and disease mechanisms. The importance of data analysis and computational methods in extracting meaningful biological insights from the complex data generated by these technologies is also highlighted. By discussing recent progress, technological innovations, and potential future directions, this review emphasizes the critical role of single-cell protein analysis in advancing life science research and its promising applications in precision medicine, biomarker discovery, and targeted therapeutics. Deciphering cellular complexity at the single-cell level holds immense potential for transforming our understanding of biological processes and ultimately improving human health.

High-Plex ELISPOT: FOLISPOT Based on Fluorescence Detection and DNA Complementary Pairing

Enzyme-linked immunospot (ELISPOT) is one of the most important methods to measure the number of specific cells by detecting protein secretion at a single-cell level. However, traditional ELISPOT based on enzyme-substrate color development can only detect one target. Therefore, scientists developed multiple-target ELISPOT based on enzyme-substrate coloring. Besides, FluoroSPOT that can detect 2-4 fluorescent signals are developed. Nevertheless, the maximum detection targets of multiple-target ELISPOT and FluoroSPOT are around 4, and the signal amplification system can be further optimized. Fluorescence-based oligo-linked immunospot (FOLISPOT), which utilized DNA-barcoded antibodies to provide a highly multiplexed method with signal amplification, was developed to detect multiple targets simultaneously. In this method, multiple targets can be detected in one round and multiple rounds of detection can be conducted, and thus a large number of targets can be detected. Besides, signal amplification is achieved by DNA complementary pairing and modular orthogonal DNA concatemers, and thus cells secreting limited amounts of proteins can be detected. According to the studies, FOLISPOT can detect more spots than ELISPOT and can detect targets that are undetectable by ELISPOT. Furthermore, FOLISPOT can be utilized to detect more than 6 targets, by allowing sequential detection of multiple targets in one round and sequential detection in multiple rounds.

Evaluation of Cellular Immune Response to Adeno-Associated Virus-Based Gene Therapy

The number of approved or investigational late phase viral vector gene therapies (GTx) has been rapidly growing. The adeno-associated virus vector (AAV) technology continues to be the most used GTx platform of choice. The presence of pre-existing anti-AAV immunity has been firmly established and is broadly viewed as a potential deterrent for successful AAV transduction with a possibility of negative impact on clinical efficacy and a connection to adverse events. Recommendations for the evaluation of humoral, including neutralizing and total antibody based, anti-AAV immune response have been presented elsewhere. This manuscript aims to cover considerations related to the assessment of anti-AAV cellular immune response, including review of correlations between humoral and cellular responses, potential value of cellular immunogenicity assessment, and commonly used analytical methodologies and parameters critical for monitoring assay performance. This manuscript was authored by a group of scientists involved in GTx development who represent several pharma and contract research organizations. It is our intent to provide recommendations and guidance to the industry sponsors, academic laboratories, and regulatory agencies working on AAV-based GTx viral vector modalities with the goal of achieving a more consistent approach to anti-AAV cellular immune response assessment.