Adenosine deaminase-1 (ADA-1) Induces Maturation and Skewing of Cytokine and Chemokine Production in Dendritic Cells to Improve Adaptive Immune Responses

Dendritic cells (DCs) are critical mediators of antigen-specific immunity through their ability to present antigen and drive T cell differentiation into different effector subsets such as follicular helper T cells (TFH). TFH cells provide both physical and cytokine-mediated stimuli to B cells resulting in somatic hypermutation and class-switching of B cell receptors. Molecules that target TFH cells, such as adenosine deaminase-1 (ADA-1), would improve humoral immunity. We have previously demonstrated that co-delivery of plasmid-encoded adenosine deaminase with an HIV-1 envelope and SARS-CoV-2 DNA vaccines in vivo, enhanced both humoral and cellular responses. However, the mechanism by which ADA-1 is acting as an adjuvant remains to be elucidated. To this end, we treated monocyte-derived DCs from healthy human donors in vitro with recombinant ADA-1 protein and evaluated the expression of maturation markers, cytokines and chemokines. ADA-1-treated DCs had a significantly increased expression of CD40 and CD86 as well as HLA-DR compared to their unstimulated, immature counterparts. The level of co-stimulatory marker and HLA-DR expression on ADA-1-treated DCs was similar to that on LPS/IFN-γ-treated DCs, indicating ADA-1-mediated DC maturation. ADA-1-treated DCs also exhibited a significant increase in IL-6, IL-1ß and CXCL13 expression. IL-6 is a key pro-TFH cytokine and IL-1ß and CXCL13 may play a role in TFH cell differentiation, function, and proliferation. Ongoing studies are aimed to drive ADA-1 overexpression in DCs and evaluate effects on antigen presentation. Overall, elucidating the mechanism of ADA-1’s adjuvanticity, will allow for its progression as a clinical adjuvant. </p