A Novel Virus-Like Particle Based Vaccine Platform Displaying the Placental Malaria Antigen VAR2CSA

Abstract

Placental malaria caused by Plasmodium falciparum is a major cause of mortality and severe morbidity. Clinical testing of a soluble protein-based vaccine containing the parasite ligand, VAR2CSA, has been initiated. VAR2CSA binds to the human receptor chondroitin sulphate A (CSA) and is responsible for sequestration of Plasmodium falciparum infected erythrocytes in the placenta. It is imperative that a vaccine against malaria in pregnancy, if administered to women before they become pregnant, can induce a strong and long lasting immune response. While most soluble protein-based vaccines have failed during clinical testing, virus-like particle (VLP) based vaccines (e.g., the licensed human papillomavirus vaccines) have demonstrated high efficacy, suggesting that the spatial assembly of the vaccine antigen is a critical parameter for inducing an optimal long-lasting protective immune response. We have developed a VLP vaccine display platform by identifying regions of the HPV16 L1 coat protein where a biotin acceptor site (AviTagTM) can be inserted without compromising VLP-assembly. Subsequent biotinylation of Avi-L1 VLPs allow us to anchor monovalent streptavidin (mSA)-fused proteins to the biotin, thereby obtaining a dense and repetitive VLP-display of the vaccine antigen. The mSA-VAR2CSA antigen was delivered on the Avi-L1 VLP platform and tested in C57BL/6 mice in comparison to two soluble protein-based vaccines consisting of naked VAR2CSA and mSA-VAR2CSA. The mSA-VAR2CSA Avi-L1 VLP and soluble mSA-VAR2CSA vaccines induced higher antibody titers than the soluble naked VAR2CSA vaccine after three immunizations. The VAR2CSA Avi-L1 VLP vaccine induced statistically significantly higher endpoint titres compared to the soluble mSA-VAR2CSA vaccine, after 1st and 2nd immunization; however, this difference was not statistically significant after 3rd immunization. Importantly, the VLP-VAR2CSA induced antibodies were functional in inhibiting the binding of parasites to CSA. This study demonstrates that the described Avi-L1 VLP-platform may serve as a versatile system for facilitating optimal VLP-display of large and complex vaccine antigens.

The principles and applications of avidin-based nanoparticles in drug delivery and diagnosis

“…This, in turn, can be utilized to fuse the antigen with monovalent streptavidin without disrupting the assembly of VLPs and their activity. [85]…”

Engineering virus-like particles as vaccine platforms

“…Sortase-mediated conjugation allows for site-directed ligation of cargoes (including peptides and small molecules) bearing a specific amino acid tag (LPETG) to VLPs that have been modified to include a target sequence (a stretch of glycine residues) [21]. Similarly, VLPs have been engineered to display poly-histidine stretches (for non-covalent conjugation to antigens with NTA-Ni 2+ moiety) [22], methionine analogues for use with click chemistry [23], or other proteins or tags that allow for non-covalent [24,25] or covalent [26] interactions. These techniques allow VLPs to display diverse antigens, including peptides, full-length proteins, carbohydrates, and other small molecules.…”

Bacterial superglue generates a full-length circumsporozoite protein virus-like particle vaccine capable of inducing high and durable antibody responses

“…HbsAg VLPs) leads to induction of strong and durable antibody responses [18, 19]. Recent studies have shown that vaccine antigens presented on VLP platforms effectively induce high titred antibody responses against poorly immunogenic antigens [20, 21]. One of these studies utilizes a split-intein (SpyTag/SpyCatcher) conjugation system to covalently attach antigens on the surface of rigid Acinetobacter phage AP205 VLPs.…”