Abstract
As viruses continue to mutate the need for rapid high titer neutralizing antibody responses has been highlighted. To meet these emerging threats, agents that enhance vaccine adjuvant activity are needed that are safe with minimal local or systemic side effects. To respond to this demand, we sought small molecules that would sustain and improve the protective effect of a currently approved adjuvant, monophosphoryl lipid A (MPLA), a Toll-like receptor 4 (TLR4) agonist. A lead molecule from a high-throughput screen, (N-(4-(2,5-dimethylphenyl)thiazol-2-yl)-4-(piperidin-1-ylsulfonyl)benzamide, was identified as a hit compound that sustained NF-κB activation by a TLR4 ligand, lipopolysaccharide (LPS), after an extended incubation (16 h). In vitro, the resynthesized compound (2D216) enhanced TLR4 ligand-induced innate immune activation and antigen presenting function in primary murine bone marrow-derived dendritic cells without direct activation of T cells. In vivo murine vaccination studies demonstrated that compound 2D216 acted as a potent co-adjuvant when used in combination with MPLA that enhanced antigen-specific IgG equivalent to that of AS01B. The combination adjuvant MPLA/2D216 produced Th1 dominant immune responses and importantly protected mice from lethal influenza virus challenge. 2D216 alone or 2D216/MPLA demonstrated minimal local reactogenicity and no systemic inflammatory response. In summary, 2D216 augmented the beneficial protective immune responses of MPLA as a co-adjuvant and showed an excellent safety profile.
Highlights
Adjuvants are used to enhance the potencies of protein and peptide-based vaccines [1, 2]
In the high-throughput screening (HTS) campaign, we identified a hit compound N-(4-(2,5dimethylphenyl)thiazol-2-yl)-4-(piperidin-1-ylsulfonyl) benzamide (2D216, Figure 1A), which prolonged NF-kB reporter activation induced by LPS, a TLR4 ligand, as a primary stimulus
We hypothesized that this compound might enhance the activation of antigen-presenting cells (APCs) in combination with a TLR4 ligand
Summary
Adjuvants are used to enhance the potencies of protein and peptide-based vaccines [1, 2]. Ligands for pattern recognition receptors (PRRs) are critical activators of innate immunity. The FDA has approved a TLR4 ligand, monophosphoryl lipid A (MPLA), and a TLR9 ligand, CpG 1018, for clinical use as vaccine adjuvants [3,4,5]. Despite these advances, single-agent adjuvants are not always sufficient to generate high titer protective antibody responses in vulnerable populations, including the elderly and immunocompromised hosts [3, 6, 7]
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