Semisynthetic Pneumococcal Glycoconjugate Nanovaccine.

Pneumococcal conjugate vaccines offer an excellent safety profile and high protection against the serotypes comprised in the vaccine. However, inclusion of protein antigens fromStreptococcus pneumoniaecombined with potent adjuvants and a suitable delivery system are expected to both extend protection to serotype strains not represented in the formulation and stimulate a broader immune response, thus more effective in young children, elderly, and immunocompromised populations. Along this line, nanoparticle (NP) delivery systems can enhance the immunogenicity of antigens by protecting them from degradation and increasing their uptake by antigen-presenting cells, as well as offering co-delivery with adjuvants. We report herein the encapsulation of a semisynthetic glycoconjugate (GC) composed of a synthetic tetrasaccharide mimicking theS. pneumoniae serotype 14 capsular polysaccharide (CP14) linked to the Pneumococcal surface protein A (PsaA) using chitosan NPs (CNPs). These GC-loaded chitosan nanoparticles (GC-CNPs) were not toxic to human monocyte-derived dendritic cells (MoDCs), showed enhanced uptake, and displayed better immunostimulatory properties in comparison to the naked GC. A comparative study was carried out in mice to evaluate the immune response elicited by the glycoconjugate-administered subcutaneously (SC), where the GC-CNPs displayed 100-fold higher IgG response as compared with the group treated with nonencapsulated GC. Overall, the study demonstrates the potential of this chitosan-based nanovaccine for efficient delivery of glycoconjugate antigens.

Single administration vaccines: delivery challenges, in vivo performance, and translational considerations.

INTRODUCTION: With a limited global supply of vaccines and an increasing vaccine hesitancy, improving vaccination coverage has become a priority. Current vaccination regimes require multiple doses to be administered in a defined schedule where missed doses may lead to incomplete vaccine coverage and failure of immunization programmes. As such, there is an ever-increasing demand to convert multi-dose injectable vaccines into single-dose formats, often called single administration vaccines (SAVs). AREAS COVERED: This review summarizes recent developments in the field of SAVs, with a focus on pulsatile or controlled-release formulations. It will identify the technical challenges, translational as well as commercial barriers to SAVs development. Furthermore, the progress of SAV formulations for hepatitis B and polio vaccines will be reviewed thoroughly as case studies, with a focus on the development challenges and the preclinical immunogenicity/reactogenicity data. EXPERT OPINION: Despite the efforts to develop SAVs, few attempts have advanced to Phase-I trials. Considering the SAV development journey and bottlenecks, including commercial barriers from the early stages, may overcome some of the hurdles around the technology. The renewed global focus on vaccines since the COVID-19 pandemic could facilitate development of a new generation of technologies for pandemic preparedness including strategies for SAVs.

On the use of adenovirus dodecahedron as a carrier for glycoconjugate vaccines.

Virus-Like Particles (VLPs) have been used as immunogenic molecules in numerous recombinant vaccines. VLPs can also serve as vaccine platform to exogenous antigens, usually peptides incorporated within the protein sequences which compose the VLPs or conjugated to them. We herein described the conjugation of a synthetic tetrasaccharide mimicking the Streptococcus pneumoniae serotype 14 capsular polysaccharide to recombinant adenoviral type 3 dodecahedron, formed by the self-assembling of twelve penton bases and investigated the induced immune response when administered subcutaneously (s.c.). Whether formulated in the form of a dodecahedron or disassembled, the glycoconjugate induced an anti-protein response after two and three immunizations equivalent to that observed when the native dodecahedron was administered. On the other hand, the glycoconjugate induced a weak anti-IgM response which diminishes after two doses but no IgM-to-IgG switch was observed in mice against the serotype 14 capsular polysaccharide. In definitive, the whole conjugation process preserved both particulate nature and immunogenicity of the adenoviral dodecahedron. Further studies are needed to fully exploit adenoviral dodecahedron potential in terms of plasticity towards sequence engineering and of its capacity to stimulate the immune system via the intranasal route of administration as well as to shift the response to the carbohydrate antigen by playing both with the carbohydrate to protein ratio and the length of the synthetic carbohydrate antigen.

A chitosan-based nanosystem as pneumococcal vaccine delivery platform.

Chitosan-based nanosystems have been described as interesting tools for antigen delivery and for enhancing the immunogenicity of nasally administered vaccines. As a possible vaccine delivery method, the chemical conjugation of chitosan nanocapsules with the Streptococcus pneumoniae cell membrane protein PsaA (pneumococcal surface adhesin A) is suggested here. The antigen PsaA, common to all pneumococcus serotypes, is expected to improve its uptake by immune cells and to activate specific T cells, generating an adaptive immune response against pneumococcus. With this aim, chitosan nanocapsules with thiol-maleimide conjugation between the polymer (chitosan) and the antigen (PsaA) were designed to enable the surface presentation of PsaA for immune cell recognition. Spherical-shaped particles, with a size of 266 ± 32 nm, positive charge of +30 ± 1 mV, and good stability profiles in simulated nasal fluids (up to 24 h) were achieved. PsaA association rates were three times higher compared with nanocapsules without covalent polymer-protein conjugation. Cytotoxicity studies in cell culture media showed non-toxic effect under 150 µg/mL concentration of nanocapsules, and subsequent studies on the maturation of immature dendritic cells in the presence of antigen-conjugated nanocapsules displayed peripheral blood mononuclear cell activation and lymphocyte differentiation after their presentation by dendritic cells. Secretion of TNFα following exposure to nanocapsules and the ability of nanocapsules to activate CD4 and CD8 T lymphocytes had also been studied. Antigen loaded nanocarrier uptake and presentation by professional presenting cells.

Preparation and characterization of lamotrigine containing nanocapsules for nasal administration.

Nanocapsules (NCs) have become one of the most researched nanostructured drug delivery systems due to their advantageous properties and versatility. NCs can enhance the bioavailabiliy of hydrophobic drugs by impoving their solubility and permeability. Also, they can protect these active pharmaceutical agents (APIs) from the physiological environment with preventing e.g. the enzymatic degradation. NCs can be used for many administration routes: e.g. oral, dermal, nasal and ocular formulations are exisiting in liquid and solid forms. The nose is one of the most interesting alternative drug administration route, because local, systemic and direct central nervous system (CNS) delivery can be achived; this could be utilized in the therapy of CNS diseases. Therefore, the goal of this study was to design, prepare and investigate a novel, lamotrigin containing NC formulation for nasal administration. The determination of micrometric parameters (particle size, polydispersity index, surface charge), in vitro (drug loading capacity, release and permeability investigations) and in vivo characterization of the formulations were performed in the study. The results indicate that the formulation could be a promising alternative of lamotrigine (LAM) as the NCs were around 305 nm size with high encapsulation efficiency (58.44%). Moreover, the LAM showed rapid and high release from the NCs in vitro and considerable penetration to the brain tissues was observed during the in vivo study.

Polymeric Core-Shell Combinatorial Nanomedicine for Synergistic Anticancer Therapy.

Core-shell nanostructures are promising platforms for combination drug delivery. However, their complicated synthesis process, poor stability, surface engineering, and low biocompatibility are major hurdles. Herein, a carboxymethyl chitosan-coated poly(lactide-co-glycolide) (cmcPLGA) core-shell nanostructure is prepared via a simple one-step nanoprecipitation self-assembly process. Engineered core-shell nanostructures are tested for combination delivery of loaded docetaxel and doxorubicin in a cancer-mimicked environment. The drugs are compartmentalized in a shell (doxorubicin, Dox) and a core (docetaxel, Dtxl) with loading contents of ∼1.2 and ∼2.06%, respectively. Carboxymethyl chitosan with both amine and carboxyl groups act as a polyampholyte in diminishing ζ-potential of nanoparticles from fairly negative (-13 mV) to near neutral (-2 mV) while moving from a physiological pH (7.4) to an acidic tumor pH (6) that can help the nanoparticles to accumulate and release the drug on-site. The dual-drug formulation was found to carry a clinically comparable 1.7:1 weight ratio of Dtxl/Dox, nanoengineered for the sequential release of Dox followed by Dtxl. Single and engineered combinatorial nanoformulations show better growth inhibition toward three different cancer cells compared to free drug treatment. Importantly, Dox-Dtxl cmcPLGA nanoparticles scored synergism with combination index values between 0.2 and 0.3 in BT549 (breast ductal carcinoma), PC3 (prostate cancer), and A549 (lung adenocarcinoma) cell lines, demonstrating significant cell growth inhibition at lower drug concentrations as compared to single-drug control groups. The observed promising performance of dual-drug formulation is due to the G2/M phase arrest and apoptosis.

Site-Specific Conjugation for Fully Controlled Glycoconjugate Vaccine Preparation.

Glycoconjugate vaccines are formed by covalently link a carbohydrate antigen to a carrier protein whose role is to achieve a long lasting immune response directed against the carbohydrate antigen. The nature of the sugar antigen, its length, its ratio per carrier protein and the conjugation chemistry impact on both structure and the immune response of a glycoconjugate vaccine. In addition it has long been assumed that the sites at which the carbohydrate antigen is attached can also have an impact. These important issue can now be addressed owing to the development of novel chemoselective ligation reactions as well as techniques such as site-selective mutagenesis, glycoengineering, or extension of the genetic code. The preparation and characterization of homogeneous bivalent pneumococcal vaccines is reported. The preparation and characterization of homogeneous bivalent pneumococcal vaccines is reported. A synthetic tetrasaccharide representative of the serotype 14 capsular polysaccharide of Streptococcus pneumoniae has been linked using the thiol/maleimide coupling chemistry to four different Pneumococcal surface adhesin A (PsaA) mutants, each harboring a single cysteine mutation at a defined position. Humoral response of these 1 to 1 carbohydrate antigen/PsaA conjugates have been assessed in mice. Our results showed that the carbohydrate antigen-PsaA connectivity impacts the anti-carrier response and raise questions about the design of glycoconjugate vaccine whereby the protein plays the dual role of immunogen and carrier.

Semisynthetic glycoconjugate based on dual role protein/PsaA as a pneumococcal vaccine.

Pneumococcal infections remain a major public health concern worldwide. The currently available vaccines in the market are based on pneumococcal capsular polysaccharides but they still need to be improved to secure an optimal coverage notably in population at risk. To circumvent this, association of virulence pneumococcal proteins to the polysaccharide valencies has been proposed with the hope to observe an additive - if not synergistic - protective effect. Along this line, the use of the highly conserved and ubiquitous pneumococcal surface adhesin A (PsaA) as a protein carrier for a synthetic pneumococcal oligosaccharide is demonstrated herein for the first time. A tetrasaccharide mimicking functional antigenic determinants from the S. pneumoniae serotype 14 capsular polysaccharide (Pn14TS) was chemically synthesised. The mature PsaA (mPsaA) was expressed in E. coli and purified using affinity chromatography. The Pn14PS was conjugated to mPsaA using maleimide-thiol coupling chemistry to obtain mPsaA-Pn14PS conjugate (protein/sugar molar ratio: 1/5.4). The mPsaA retained the structural conformation after the conjugation and lyophilisation. The prepared glycoconjugate adjuvanted with α-galactosylceramide, a potent activator of invariant Natural Killer T cells, was tested in mice for its immunological response upon subcutaneous injection in comparison with mPsaA alone and a model BSA conjugate (BSA-Pn14PS, used here as a control). Mice immunised with the mPsaA-Pn14TS produced a robust IgG response against mPsaA and against the capsular polysaccharide from pneumococcal serotype 14. These data provide the basis for novel pneumococcal vaccine development.