Boosting Humoral Immune Responses to Tumor-associated Carbohydrate Antigens with Virus-like Particles

The development of carbohydrate-based anticancer vaccines is an attractive approach towards the prevention and treatment of cancer. The weak immunogenicity of carbohydrate antigens and tolerance by the immune system are major obstacles towards the design of effective cancer vaccines. Recently, virus-like particles have been shown to be a promising platform to overcome the aforementioned difficulties. In this chapter, we provide an overview on the structural and immunological features of virus-like particles in eliciting anti-carbohydrate antibody responses. The immuno-potentiating activities of several virus-like particle systems are compared, and insights into critical factors of virus-like particles that help shape the anti-carbohydrate responses are discussed.

Nano-decoration of the Hemagglutinating Virus of Japan envelope (HVJ-E) using a layer-by-layer assembly technique

In this study, we created a nanoscale layer of hyaluronic acid (HA) on the inactivated Hemagglutinating Virus of Japan envelope (HVJ-E) via a layer-by-layer (LbL) assembly technique for CD-44 targeted delivery. HVJ-E was selected as the template virus because it has shown a tumor-suppressing ability by eliciting inflammatory cytokine production in dendritic cells. Although it has been required to increase the tumor-targeting ability and reduce nonspecific binding because HVJ-E fuses with virtually all cells and induces hemagglutination in the bloodstream, complete modifications of single-envelope-type viruses with HA have been difficult. Therefore, we studied the surface ζ potential of HVJ-E at different pH values and carefully examined the deposition conditions for the first layer using three cationic polymers: poly-L-lysine (PLL), chitosan (CH), and glycol chitosan (GC). GC-coated HVJ-E particles showed the highest disperse ability under physiological pH and salt conditions without aggregation. An HA layer was then prepared via alternating deposition of HA and GC. The successive decoration of multilayers on HVJ-E has been confirmed by dynamic light scattering (DLS), ζ potentials, and transmission electron microscopy (TEM). An enzymatic degradation assay revealed that only the outermost HA layer was selectively degraded by hyaluronidase. However, entire layers were destabilized at lower pH. Therefore, the HA/GC-coated HVJ-E describe here can be thought of as a potential bomb for cancer immunotherapy because of the ability of targeting CD44 as well as the explosion of nanodecorated HA/GC layers at endosomal pH while preventing nonspecific binding at physiological pH and salt conditions such as in the bloodstream or normal tissues.

Viral capsids as self-assembling templates for new materials

The self-assembling protein shells of viruses have provided convenient scaffolds for the construction of many new materials with well-defined nanoscale architectures. In some cases, the native amino acid functional groups have served as nucleation sites for the deposition of metals and semiconductors, leading to organic-inorganic composites with interesting electronic, magnetic, optical, and catalytic properties. Other approaches have involved the covalent modification of the protein monomers, typically with the goal of generating targeting delivery vehicles for drug and imaging cargo. Covalently modified capsid proteins have also been used to generate periodic arrays of chromophores for use in light harvesting and photocatalytic applications. All of these research areas have taken advantage of the low polydispersity, high chemical stability, and intrinsically multivalent properties that are uniquely offered by these biological building blocks.

Altering the landscape of viruses and bionanoparticles

In recent years, protein-based nanoparticles or bionanoparticles (BNPs), have been used as primary building blocks to generate ornate nanomaterials for a wide-range of applications. Over the past fifty years, numerous BNPs have been chemically modified or genetically engineered to function as smart drug/gene delivery vehicles, advanced vaccine vehicles, and isolated reaction vessels for inorganic, metallic, and semi-conductive depositions. These studies have contributed invaluable insights to the expansive capabilities of these simple, yet highly robust, nanosized building materials. Here we highlight some of the recent progress in the chemical modifications of BNPs and hopefully inspire the development of many new materials in the near future.

How rigid are viruses

Viruses have traditionally been studied as pathogens, but in recent years they have been adapted for applications ranging from drug delivery and gene therapy to nanotechnology, photonics, and electronics. Although the structures of many viruses are known, most of their biophysical properties remain largely unexplored. Using Brillouin light scattering, we analyzed the mechanical rigidity, intervirion coupling, and vibrational eigenmodes of Wiseana iridovirus (WIV). We identified phonon modes propagating through the viral assemblies as well as the localized vibrational eigenmode of individual viruses. The measurements indicate a Young's modulus of approximately 7 GPa for single virus particles and their assemblies, surprisingly high for "soft" materials. Mechanical modeling confirms that the DNA core dominates the WIV rigidity. The results also indicate a peculiar mechanical coupling during self-assembly of WIV particles.

Polyaniline-carbon nanotube composites

The key developments in polyaniline-carbon nanotube (PANI-CNT) composites are reviewed. Apart from in situ chemical polymerization and electrochemical deposition, a number of interesting approaches including the use of aniline functionalized CNTs and ultrasound/microwave/γ-radiation initiated polymerization have been used in the preparation of composites. The structure and properties of these composites have been investigated by a variety of techniques including absorption, infrared (IR), Raman, X-ray photoelectron spectroscopy methods, scanning electron and scanning probe microscopy techniques, cyclic voltammetry, and thermogravimetry. The experimental results indicate favorable interaction between PANI and CNTs. The CNT content in these composites controls their conductive, mechanical, and thermal properties. The most interesting characteristic is their easy dispersibility in aqueous solution. The performance evaluation studies of PANI-CNT composites in a number of applications including supercapacitors, fuel cells, sensors, and actuators are highlighted.

Plant viruses as biotemplates for materials and their use in nanotechnology

In recent years, plant virus capsids, the protein shells that form the surface of a typical plant virus particle, have emerged as useful biotemplates for material synthesis. All virus capsids are assembled from virus-coded protein subunits. Many plant viruses assemble capsids with precise 3D structures providing nanoscale architectures that are highly homogeneous and can be produced in large quantities. Capsids are amenable to both genetic and chemical modifications allowing new functions to be incorporated into their structure by design. The three capsid surfaces, the interior surface, the exterior surface, or the interface between coat protein subunits, can be independently functionalized to produce multifunctional biotemplates. In this review, we examine the recent advances in using plant virus capsids as biotemplates for nanomaterials and their potential for applications in nanotechnology, especially medicine.

Cowpea mosaic virus capsid: a promising carrier for the development of carbohydrate based antitumor vaccines

Immunotherapy targeting tumor cell surface carbohydrates is a promising approach for cancer treatment. However, the low immunogenecity of carbohydrates presents a formidable challenge. We describe here the enhancement of carbohydrate immunogenicity by an ordered display on the surface of the cowpea mosaic virus (CPMV) capsid. The Tn glycan, which is overexpressed on numerous cancer cell surfaces, was selected as the model antigen for our study. Previously it has been shown that it is difficult to induce a strong T cell-dependent immune response against the monomeric form of Tn presented in several ways on different carriers. In this study, we first synthesized Tn antigens derivatized with either a maleimide or a bromoacetamide moiety that was conjugated selectively to a cysteine mutant of CPMV. The glycoconjugate was then injected into mice and pre- and post-immune antibody levels in the mice sera were measured by enzyme-linked immunosorbant assays. High total antibody titers and, more importantly, high IgG titers specific for Tn were obtained in the post-immune day 35 serum, suggesting the induction of T cell-dependent antibody isotype switching by the glycoconjugate. The antibodies generated were able to recognize Tn antigens presented in their native conformations on the surfaces of both MCF-7 breast cancer cells and the multidrug resistant breast cancer cell line NCI-ADR RES. These results suggest that the CPMV capsid can greatly enhance the immunogenicity of weak antigens such as Tn and this can provide a promising tool for the development of carbohydrate based anti-cancer vaccines.

Monodisperse polymer-virus hybrid nanoparticles

Self-assembly of polystyrene sulfonate and modified cowpea chlorotic mottle virus protein yields monodisperse icosahedral nanoparticles of 16 nm size.