Polymeric Linear Peptide Chimeric Vaccine-Induced Antimalaria Immunity Is Associated with Enhanced In Vitro Antigen Loading

Abstract

Immunization of mice with Plasmodium berghei or Plasmodium yoelii synthetic linear peptide chimeras (LPCs) based on the circumsporozoite protein protects against experimental challenge with viable sporozoites. The immunogenicity of LPCs is significantly enhanced by spontaneous polymerization. To better understand the antigenic properties of polymeric antimalarial peptides, we studied the immune responses elicited in mice immunized with a polymer or a monomer of a linear peptide construct specific for P. yoelii and compared the responses of antigen-presenting cells following incubation with both peptide species. Efficient uptake of the polymeric peptide in vitro resulted in higher expression of the coactivation markers CD80, CD40, and CD70 on dendritic cells and higher proinflammatory cytokine production than with the monomeric peptide. Macropinocytosis seems to be the main route used by polymeric peptides internalized by antigen-presenting cells. Spontaneous polymerization of synthetic antimalarial-peptide constructs to target professional antigen-presenting cells shows promise for simple delivery of subunit malaria vaccines.Malaria is globally the most devastating vector-borne disease, responsible for more than 1 million fatalities annually (37). Malaria is also one of the most deadly transmissible diseases (6). The development of a safe and effective malaria vaccine remains an urgent, yet unmet, medical need for vast populations living in areas of endemicity (6, 39). Although revived interest in malaria research and vaccine development has recently inspired a wave of clinical trials with some promising vaccine candidates, an ideal formulation remains a distant prospect (15, 39). The lack of surrogate markers to predict protection and the complexity of the parasite life cycle have hindered the development of effective vaccines. Epidemiological and clinical evidence from vaccine trials suggest that an ideal malaria vaccine should include several antigens (14, 16). However, the inclusion of multiple antigens in a single vaccine formulation is logistically challenging and requires the use of efficient delivery systems. We have used polymeric linear peptide chimeras (LPCs) as a simple and efficient alternative to deliver subunit vaccines (8,36).Proof-of-principle studies confirmed that immunization with LPCs containing circumsporozoite protein sequences elicited protection against malaria challenge using Plasmodium berghei and Plasmodium yoelii rodent malaria models (8, 36). LPCs are synthetic linear peptides that contain a Plasmodium promiscuous CD4 ϩ T-cell epitope synthesized in tandem with B-cell and cytotoxic T-lymphocyte (CTL) epitopes. A distinguishing feature of LPCs is the inclusion of amino-and carboxyl-terminal cysteine residues that form cross-linkages for spontaneous polymerization. This results in an array of homopolymeric peptide species, easily confirmed using mass spectroscopy (8). Peptide homopolymerization is critical for antigenicity and immunogenicity (8).To better understand the protective eff...

A chimeric protein-based malaria vaccine candidate induces robust T cell responses against Plasmodium vivax MSP119

“…Three factors could explain the improved cellular immunogenicity of our construct: (1) The defined P. vivax promiscuous T cell epitopes, specially PvT53 and PvT19, have been shown to increase the immunogenicity of diverse antigens, as closely related as the P. falciparum CSP (NANP) 3 repeats 24 , or as far as B cell epitopes of the Tau and Amyloid-Beta proteins related to Alzheimer disease 51 . (2) We have shown the ability of our chimeric proteins with the topology used for the design of PvRMC-MSP1 to enhance dendritic cells uptake and maturation 52 . (3) Our promiscuous T cell epitopes resemble a family of compounds that are known as cell penetrating peptides (CPPs) 52 .…”

Multiple Antigen Peptide Vaccines againstPlasmodium falciparumMalaria

“…Some of the perceived major arguments against the peptide-based vaccine approach include their short linear nature that prohibited the inclusion of multiple protective B-cell and T-cell epitopes in the same construct and the presumed inability to create the Cys-Cys disulfide bonds in conformationdependent epitopes. However, recent studies suggest that protein domains that mimic the native protein structure can be created in chemically synthesized peptide constructs that include conformationally correct Cys-Cys bonds to create immunologically active molecules (7,48,49). In addition, recently it has been suggested that large-scale and costeffective synthesis of peptide-based vaccines is possible (8).…”

Induction of Multifunctional Broadly Reactive T Cell Responses by a Plasmodium vivax Circumsporozoite Protein Recombinant Chimera

“…We have previously shown that positively charged polymeric synthetic peptide constructs (PvRMC-CSP exhibits an isoelectric point of 9.39) are internalized by antigenpresenting cells via endocytosis (67). In this work, peptide uptake was enhanced by the interaction of positively charged residues with negatively charged membranes similar to the mechanism used by a family of compounds called cell-penetrating peptides.…”

“…In this work, peptide uptake was enhanced by the interaction of positively charged residues with negatively charged membranes similar to the mechanism used by a family of compounds called cell-penetrating peptides. The endocytosis of these peptides upregulated cytokine production and expression of cell surface maturation markers by DCs and ultimately was related to protection in mice against a P. yoelii challenge (67).…”