Examining the outcomes of enhanced CD28 signaling in vivo using ‘humanized’ mice

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Presentation Time: 02:15 PM - 02:30 PM
Abstract ID: 4737 - B

Presenting Author:
Alexander Brady , Graduate Student at Cornell Univ. Col. of Vet. Med.

Abstract:

CD28 signaling is stronger in humans than in mice, as demonstrated by the phase one clinical trial of a CD28 superagonist antibody. In mice CD28 superagonist expanded regulatory T cells and reduced autoimmune disease, but in humans it induced life-threatening cytokine storm. The final signaling domain in human CD28 is PYAPP, while in mice it is PYAPA. We used CRISPR/Cas9 to develop a ‘humanized’ mouse with a CD28 A->P substitution (CD28^A210P) to examine the outcomes of this variation on T cell-driven disease. In vitro, CD28^A210P T cells had increased signaling, cytokine production, and proliferation. In vivo, after injection with CD28 superagonist, CD28^A210P mice had increased weight loss, cytokine production, and less Treg expansion, supporting that humanized CD28 signaling could contribute to the excessive inflammatory response. Following LCMV cl13 infection, CD28^A210P mice display enhanced early Th1 and CD8 T cell responses with exacerbated weight loss but then underwent increased exhaustion, leading to rapid recovery of weight. Similarly, CD28^A210P mice show increased EAE incidence but milder symptoms, coinciding with an increase in CNS-infiltrating CD8 T cells which play a regulatory role in EAE. This study shows enhanced CD28 signaling due to an amino acid variation can alter T cell driven disease and reveals nuances in immunoregulation. This expands our knowledge of CD28, with potential implications for immunotherapeutics that target or utilize CD28 signaling.