Enhancing Effector T Cell Migration to Mucosal Regions Using Rexinoids and Plasmid Adjuvants

Mucosal membranes represent a major site of pathogen transmission and cancer development. Enhancing T cell migration to mucosal surfaces could improve immune-based therapies for these diseases, yielding better clinical outcomes. All-trans-retinoic acid (ATRA) is a biologically active form of vitamin A that has been shown to increase T cell migration to mucosal sites, however its therapeutic use is limited by its toxicity potential and unstable nature. ATRA-related compounds with lower toxicity and higher stability were assessed for their ability to induce similar immune migration effects as ATRA, using in vitro and in vivo model systems. Chapter 2 summarizes the first project, in which synthetic, ATRA-like compounds called rexinoids were used to modulate T cell expression of mucosal homing proteins chemokine receptor 9 (CCR9) and integrin alpha 4 beta 7 (α4β7), and alter their physical migration in vitro. Several rexinoids independently mimicked the activity of ATRA to enhance protein expression and migration, while others worked synergistically with subtoxic doses of ATRA to produce similar results. Furthermore, rexinoid administration in vivo was well-tolerated by animal models, a finding not seen with ATRA. Chapter 3 focuses on the second project, where plasmids containing ATRA-synthesizing proteins were assessed for their in vivo ability to act as mucosal vaccine adjuvants and enhance T cell migration to mucosal sites during DNA vaccination. Though increased mucosal migration was seen with use of the adjuvant plasmids, these findings were not determined to be significant. Immune-mediated protection following viral challenge was also not determined to be significant in animal models receiving both vaccine and adjuvant plasmids. The data shows that several novel rexinoids may possess enhanced clinical utility compared to ATRA, lending support for their use in immunotherapeutic approaches towards mucosal maladies. While the potential mucosal vaccine adjuvants did not show great significance in enhancing T cell migration or viral protection, further optimization of the model system may produce better results. This work helps advance knowledge of immune cell trafficking to afflicted mucosal regions. It can be used as a basis for understanding migration to other body areas, as well as for the development of better immune-based treatments.