Publications

SARS-CoV-2 mRNA vaccination generates protective B cell responses targeting the SARS-CoV-2 spike glycoprotein. Whereas anti-spike memory B cell responses are long lasting, the anti-spike humoral antibody response progressively wanes, making booster vaccinations necessary for maintaining protective immunity. Here, we qualitatively investigated the plasmablast responses by measuring from single cells within hours of sampling the affinity of their secreted antibody for the SARS-CoV-2 spike receptor binding domain (RBD) in cohorts of BNT162b2-vaccinated naive and COVID-19–recovered individuals. Using a droplet microfluidic and imaging approach, we analyzed more than 4,000 single IgG-secreting cells, revealing high interindividual variability in affinity for RBD, with variations over 4 logs. High-affinity plasmablasts were induced by BNT162b2 vaccination against Hu-1 and Omicron RBD but disappeared quickly thereafter, whereas low-affinity plasmablasts represented more than 65% of the plasmablast response at all time points. Our droplet-based method thus proves efficient at fast and qualitative immune monitoring and should be helpful for optimization of vaccination protocols.

https://insight.jci.org/articles/view/166602

Rheology of concentrated protein solutions is crucial for the understanding of macromolecular crowding dynamics as well as the formulation of protein therapeutics. The cost and scarcity of most protein samples prevents wide-scale rheological studies as conventional viscosity measurement methods require large sample volume. There is a growing need for a precise and robust viscosity measurement tool that minimizes consumption and simplifies the handling of highly concentrated protein solutions. This objective is achieved by combining microfluidics and microrheology: we developed a specific microsystem to study the viscosity of aqueous solutions at high concentrations. The PDMS chip allows in situ production, storing and monitoring of water-in-oil nanoliter droplets. We perform precise viscosity measurements inside individual droplets by particle-tracking microrheology of fluorescent probes. Pervaporation of water through a PDMS membrane induces aqueous droplet shrinking, concentrating the sample up to 150 times, thus allowing viscosity measurements along an extended concentration range in just one experiment. The methodology is precisely validated by studying the viscosity of sucrose solutions. Two model proteins are also studied with sample consumption reduced to as little as 1 μL of diluted solution, showcasing the viability of our approach for the study of biopharmaceuticals.

https://pubs.rsc.org/en/content/articlelanding/2023/lc/d3lc00073g

Increasing evidence suggests that natural killer (NK) cells are composed of distinct functional subsets. This multifunctional role has made them an attractive choice for anticancer immunotherapy. A functional NK cell repertoire is generated through cellular education, resulting in a heterogeneous NK cell population with distinct capabilities responding to different stimuli. The application of a high-throughput droplet-based microfluidic platform allows monitoring of NK cell-target cell interactions at the single-cell level and in real-time. A variable response of single NK cells toward different target cells is observed, and a distinct population of NK cells (serial killers) capable of inducing multiple target lysis is identified. By assessing the cytotoxic dynamics, it is shown that single umbilical cord blood-derived CD34+ hematopoietic progenitor (HPC)-NK cells display superior antitumor cytotoxicity. With an integrated analysis of cytotoxicity and cytokine secretion, it is shown that target cell interactions augment cytotoxic as well as secretory behavior of NK cells. By providing an integrated assessment of NK cell functions by microfluidics, this study paves the way to further functionally characterize NK cells ultimately aimed to improve cancer immunotherapy.

https://doi.org/10.1002/adbi.202200207