Soluble Proteins Induce Strong CD8+ T Cell and Antibody Responses through Electrostatic Association with Simple Cationic or Anionic Lipopeptides That Target TLR2

Abstract

The low immunogenicity exhibited by most soluble proteins is generally due to the absence of molecular signatures that are recognized by the immune system as dangerous. In this study, we show that electrostatic binding of synthetic branched cationic or anionic lipopeptides that contain the TLR-2 agonist Pam2Cys markedly enhance a protein’s immunogenicity. Binding of a charged lipopeptide to oppositely charged protein Ags resulted in the formation of stable complexes and occurs at physiologic pH and salt concentrations. The induction of cell-mediated responses is dependent on the electrostatic binding of lipopeptide to the protein, with no CD8+ T cells being elicited when protein and lipopeptide possessed the same electrical charge. The CD8+ T cells elicited after vaccination with lipopeptide–protein Ag complexes produced proinflammatory cytokines, exhibited in vivo lytic activity, and protected mice from challenge with an infectious chimeric influenza virus containing a single OVA epitope as part of the influenza neuraminidase protein. Induction of a CD8+ T cell response correlated with the ability of lipopeptide to facilitate Ag uptake by DCs followed by trafficking of Ag-bearing cells into draining lymph nodes. Oppositely charged but not similarly charged lipopeptides were more effective in DC uptake and trafficking. Very high protein-specific Ab titers were also achieved by vaccination with complexes composed of oppositely charged lipopeptide and protein, whereas vaccination with similarly charged constituents resulted in significant but lower Ab titers. Regardless of whether similarly or oppositely charged lipopeptides were used in the induction of Ab, vaccination generated dominant IgG1 isotype Abs rather than IgG2a.

Efficient Induction of Antitumor Immunity by Synthetic Toll-like Receptor Ligand–Peptide Conjugates

“…We have studied different clinically feasible TLR-L targeting systems to overcome the suboptimal CD8 þ CTL induction, to counteract improper polarization and regulation of T-cell responses, and to enhance peptide delivery to DCs. Several studies show that random coupling of TLR-L to protein antigen is an attractive approach to deliver antigens to DCs and induces an antigenspecific T-cell immune response (9)(10)(11)(12)(13). Likewise, coupling of minimal CTL epitopes to a synthetic TLR2-L has been reported to be an efficient vaccine modality (14).…”

A new TLR2 agonist promotes cross-presentation by mouse and human antigen presenting cells

“…[16][17][18] Here, we show that SMIP2.1 is also a good inducer of a CTL response when mixed with the antigen as aqueous suspension using either mice or human cells. Mice that received OVA-specific OT-I TCR transgenic cells by adoptive transfer showed increased CD8 C T cell proliferation, cytokine production, and cytotoxic activity upon inclusion of SMIP2.1 in the OVA vaccine formulation.…”

“…17 However, these 2 approaches may complicate large-scale production of vaccines. For example, scale-up of chemical conjugation of a soluble antigen with a lipopeptide can be challenging because of the different solubility characteristics of these 2 components.…”

Lipidated promiscuous peptides vaccine for tuberculosis-endemic regions

“…Employing different models, the efficacy of peptide-based vaccines containing Pam2Cys have been demonstrated in the context of infectious diseases, cancer, and neutralization of the reproductive hormone gonadotropin-releasing hormone (GnRH). In each case, these vaccine candidates have generated not only successful but also long-lasting immune responses [7,[42][43][44][45][46][47][48][49][50][51][52][53]. DCs can express on their surface both peptide-loaded and empty MHC molecules, and thus they can efficiently capture peptides directly from the extracellular milieu for Review Trends in Molecular Medicine October 2012, Vol.…”

“…Pam2Cys-lipidated peptides induce robust antibody titers and vigorous and selective T cell responses [7,[42][43][44][45][46][47][48][49][50]. As a consequence, lipidated peptides can be used as vaccines in several situations where the efficacy of conventional vaccines has been compromised.…”