Alpaca single B cell interrogation and heavy-chain-only antibody discovery on an optofluidic platform

Function-first discovery of high affinity monoclonal antibodies using Nanovial-based plasma B cell screening

Antibody discovery technologies, essential for research and therapeutic applications, have evolved significantly since the development of hybridoma technology. Various in vitro (display) and in vivo (animal immunization and B cell-sequencing) workflows have led to the discovery of antibodies against diverse antigens. Despite this success, standard display and B-cell sequencing-based technologies are limited to targets that can be produced in a soluble form. This limitation inhibits the screening of function-inducing antibodies, which require the target to be expressed in cells to monitor function or signaling, and antibodies targeting proteins that maintain their physiological structure only when expressed on cell membranes, such as G-protein coupled receptors (GPCRs). A high-throughput two-cell screening workflow, which localizes an antibody-secreting cell (ASC) and a cell expressing the target protein in a microenvironment, can overcome these challenges. To make function-first plasma cell-based antibody discovery accessible and scalable, we developed hydrogel Nanovials that can capture single plasma cells, target-expressing cells, and plasma cell secretions (antibodies). The detection and isolation of Nanovials harboring the antigen-specific plasma cells are then carried out using a flow cytometry cell sorter - an instrument that is available in most academic centers and biopharmaceutical companies. The antibody discovery workflow employing Nanovials was first validated in the context of two different cell membrane-associated antigens produced in recombinant form. We analyzed over 40,000 plasma cells over two campaigns and were able to identify a diversity of binders that i) exhibited high affinity (picomolar) binding, ii) targeted multiple non-overlapping epitopes and iii) demonstrated high developability scores. A campaign using the two-cell assay targeting the immune checkpoint membrane protein PD-1 yielded cell binders with similar EC50s to clinically used Pembrolizumab and Nivolumab. The highest selectivity for binders was observed for sorted events corresponding with the highest signal bound to target cells on Nanovials. Overall, Nanovials can provide a strong foundation for function-first antibody discovery, yielding direct cell binding information and quantitative data on prioritization of hits with flexibility for additional functional readouts in the future.

Monoclonal Antibody Generation Using Single B Cell Screening for Treating Infectious Diseases

The screening of antigen-specific B cells has been pivotal for biotherapeutic development for over four decades. Conventional antibody discovery strategies, including hybridoma technology and single B cell screening, remain widely used based on their simplicity, accessibility, and proven track record. Technological advances and the urgent demand for infectious disease applications have shifted paradigms in single B cell screening, resulting in increased throughput and decreased time and labor, ultimately enabling the rapid identification of monoclonal antibodies with desired biological and biophysical properties. Herein, we provide an overview of conventional and emergent single B cell screening approaches and highlight their potential strengths and weaknesses. We also detail the impact of innovative technologies-including miniaturization, microfluidics, multiplexing, and deep sequencing-on the recent identification of broadly neutralizing antibodies for infectious disease applications. Overall, the coronavirus disease 2019 (COVID-19) pandemic has reinvigorated efforts to improve the efficiency of monoclonal antibody discovery, resulting in the broad application of innovative antibody discovery methodologies for treating a myriad of infectious diseases and pathological conditions.

A method for rapid nanobody screening with no bias of the library diversity

Nanobody, referred to the variable domain of heavy-chain-only antibodies, has several advantages such as small size and feasible Escherichia coli expression, making them promising for scientific research and therapies. Conventional nanobody screening and expression methods often suffer from the need for subcloning into expression vectors and amplification-induced diversity loss. Here, we developed an integrated method for simultaneous screening and expression. Nanobody libraries were cloned and secretly expressed in the culture medium. Target-specific nanobodies were isolated through 1-3 rounds of dilution and regrowth following the Poisson distribution. This ensured no dismissal of positive clones, with populations of positive clones increasing over 10-fold in each dilution round. Ultimately, we isolated 5 nanobodies against death domain receptor 5 and 5 against Pyrococcus furiosus DNA polymerase directly from their immunized libraries. Notably, our approach enables nanobody screening without specialized instruments, demonstrating broad applicability in routine monoclonal nanobody production for diverse biomedical applications.