Small Molecule Calcium Channel Activator Potentiates Adjuvant Activity.

Area of Science:

• Immunology
• Vaccinology
• Medicinal Chemistry

Background:

• Current vaccines often require adjuvants to enhance immune responses.
• There is a need for fully synthetic adjuvants that improve vaccine efficacy and durability.
• Previous work identified small molecules, including 2D216, that extend NF-κB activation.

Purpose of the Study:

• To elucidate the mechanism of action of the synthetic adjuvant 2D216 in human cells.
• To investigate the potential of 2D216 and its analogs as co-adjuvants with existing vaccine components.
• To explore novel pathways for adjuvant activity beyond direct pattern recognition receptor (PRR) agonism.

Main Methods:

• Utilized reporter cell lines, RNA-sequencing, calcium (Ca2+) flux assays, and immunoblots to study 2D216's effects.
• Assessed 2D216's impact on mitogen-activated protein kinases, PRRs, and T cell activation.
• Evaluated analogs of 2D216 in Toll-like receptor 4 (TLR4) ligand-stimulated autologous mixed lymphocyte reactions (MLRs).

Main Results:

• 2D216 elevated intracellular Ca2+ via plasma membrane channels, leading to nuclear factor of activated T-cells (NFAT) translocation.
• 2D216 did not directly activate most PRRs but enhanced cytokine production and costimulatory molecule expression on antigen-presenting cells.
• Analog 2E151 demonstrated greater potency than 2D216 in enhancing TLR4-stimulated MLRs.

Conclusions:

• 2D216 functions as a co-adjuvant by modulating intracellular Ca2+ and NFAT signaling, complementing TLR4 stimulation.
• This mechanism differs from direct PRR agonism, offering a novel strategy for adjuvant development.
• Synthetic molecules like 2D216 and its analogs hold promise for enhancing human vaccine-induced immune responses.