An anti-Galectin-3 intrabody improves primary and memory response of antigen-specific CD8+ T cells during viral infection

Genetic ablation approaches are routinely used to establish gene function, but these are not beyond limitations. The intracellularly expressed camelid single-domain antibodies (sdAbs), or nanobodies, can specifically disrupt molecular interactions and, therefore, help ascertain their role in the process of cellular differentiation. The approach has not been evaluated in differentiating T cells or the stimulating DCs during viral infection. We modified the intracellular response of Galectin-3 (Gal-3) using an -Gal-3 intrabody (IB) in antigen-specific CD8+ T cells and assessed their differentiation patterns during a resolving Influenza A virus encoding SIINFEKL epitope (IAV: WSN-SIINFEKL). The -Gal-3 IB expressors, compared to the cells genetically depleted of Gal-3, exhibit a significantly prolonged activation, enhanced proliferation, and elevated cytokine production following in vitro stimulation. The -Gal-3 IB expressing cells show enhanced functionality and generate an efficient effector response, favoring the generation of memory precursor effector cells (MPECs: CD127hiKLRG1lo) over short-lived effector cells (SLECs: CD127loKLRG1hi) in IAV-infected animals. Such a differentiation pattern results in improved differentiation of effector memory (CD44hiCD62LloCCR7lo) cells amongst the -Gal-3 IB-expressing cells. The generated memory cells are efficiently recalled upon challenge infection with MHV68-SIINFEKL and help control the infection better. Therefore, modifying the intracellular response of Gal-3 using a sdAb could improve the primary and memory response of antigen-specific CD8+ T cells.