Lipid and carbohydrate based adjuvant/carriers in immunology

Carbohydrate-containing nanoparticles as vaccine adjuvants

Introduction: Adjuvants are essential to vaccines for immunopotentiation in the elicitation of protective immunity. However, classical and widely used aluminum-based adjuvants have limited capacity to induce cellular response. There are increasing needs for appropriate adjuvants with improved profiles for vaccine development toward emerging pathogens. Carbohydrate-containing nanoparticles (NPs) with immunomodulatory activity and particulate nanocarriers for effective antigen presentation are capable of eliciting a more balanced humoral and cellular immune response.Areas covered: We reviewed several carbohydrates with immunomodulatory properties. They include chitosan, β-glucan, mannan, and saponins, which have been used in vaccine formulations. The mode of action, the preparation methods, characterization of these carbohydrate-containing NPs and the corresponding vaccines are presented.Expert opinion: Several carbohydrate-containing NPs have entered the clinical stage or have been used in licensed vaccines for human use. Saponin-containing NPs are being evaluated in a vaccine against SARS-CoV-2, the pathogen causing the on-going worldwide pandemic. Vaccines with carbohydrate-containing NPs are in different stages of development, from preclinical studies to late-stage clinical trials. A better understanding of the mode of action for carbohydrate-containing NPs as vaccine carriers and as immunostimulators will likely contribute to the design and development of new generation vaccines against cancer and infectious diseases.

Carbohydrate Immune Adjuvants in Subunit Vaccines

Modern subunit vaccines are composed of antigens and a delivery system and/or adjuvant (immune stimulator) that triggers the desired immune responses. Adjuvants mimic pathogen-associated molecular patterns (PAMPs) that are typically associated with infections. Carbohydrates displayed on the surface of pathogens are often recognized as PAMPs by receptors on antigen-presenting cells (APCs). Consequently, carbohydrates and their analogues have been used as adjuvants and delivery systems to promote antigen transport to APCs. Carbohydrates are biocompatible, usually nontoxic, biodegradable, and some are mucoadhesive. As such, carbohydrates and their derivatives have been intensively explored for the development of new adjuvants. This review assesses the immunological functions of carbohydrate ligands and their ability to enhance systemic and mucosal immune responses against co-administered antigens. The role of carbohydrate-based adjuvants/delivery systems in the development of subunit vaccines is discussed in detail.

Fundamentals of Vaccine Delivery in Infectious Diseases

Infectious diseases continue to be the major causes of illness, disability, and death. Moreover, in recent years, new infectious agents and diseases are being identified, and some diseases that were previously considered under control have reemerged. Furthermore, antimicrobial resistance has grown rapidly in a variety of hospital as well as community acquired infections. Thus, humanity still faces big challenges in the prevention and control of infectious diseases. Vaccination, generally considered to be the most effective method of preventing infectious diseases, works by presenting a foreign antigen to the immune system to evoke an immune response. The administered antigen can either be a live, but weakened, form of a pathogen (bacteria or virus), a killed or inactivated form of the pathogen, or a purified material such as a protein. However, no vaccine is completely safe; therefore, vaccine safety research and monitoring are necessary to minimize vaccine related harms. From the formulation point of view, the goal continues to be to improve the quality and global availability of vaccine delivery systems. This chapter provides an introduction to vaccine formulation, describes the delivery routes that are utilized, and discusses the factors that affect the safety and stability of a vaccine formulation.

Chitosan-based systems for the delivery of vaccine antigens

This review discusses the current status of chitosan and its derivatives as adjuvants and delivery systems in vaccine delivery, and their future possibilities and challenges. After a brief introduction to adjuvants and delivery systems, chitosan will be described in detail in regard to vaccine formulation. Applications of chitosan and its derivatives will be reviewed and their proposed mechanisms in the enhancement of immune responses will be discussed.

Glycopeptide dendrimers, part III: a review. Use of glycopeptide dendrimers in immunotherapy and diagnosis of cancer and viral diseases

Glycopeptide dendrimers containing different types of tumor associated-carbohydrate antigens (T(N), TF, sialyl-T(N), sialyl-TF, sialyl-Le(x), sialyl-Le(a) etc.) were used in diagnosis and therapy of different sorts of cancer. These dendrimeric structures with incorporated T-cell epitopes and adjuvants can be used as antitumor vaccines. Best results were obtained with multiantigenic vaccines, containing, e.g. five or six different TAAs. The topic of TAAs and their dendrimeric forms at molecular level are reviewed, including structure, syntheses, and biological activities. Use of glycopeptide dendrimers as antiviral vaccines against HIV and influenza is also described. Their syntheses, physico-chemical properties, and biological activities are given with many examples.

Hollow carbonaceous capsules from glucose solution

An easy hydrothermal method was developed for preparing hollow carbonaceous capsules with reactive surface layer and tunable void size, and shell thickness through a hydrothermal method at 180 degrees C, using only the anionic surfactant sodium dodecyl sulfate (SDS) and glucose as starting material. Ag nanoparticles of less than 10 nm were loaded onto the surface of capsules under ambient condition. Products were characterized with TEM, SEM, and FT-IR spectra. The process is green, cheap, and easy. Since no toxic materials were used in preparation and as-prepared capsules a shared reactive surface layer and a stable carbonaceous framework, the capsules might find application in fields such as biochemistry, pharmaceutics, and clinical diagnostics.

Advances in potential M-protein peptide-based vaccines for preventing rheumatic fever and rheumatic heart disease

Rheumatic fever (RF) and rheumatic heart disease (RHD) are postinfectious complications of an infection (or repeated infection) with the Gram-positive bacterium, Streptococcus pyogenes (also known as group A streptococcus, GAS). RF and RHD are global problems and affect many indigenous populations of developed countries and many developing countries. However, RF and RHD are only part of a larger spectrum of diseases caused by this organism. The development of a vaccine against GAS has primarily targeted the abundant cell-surface protein called the M-protein. This review focuses on different M-protein-based-subunit vaccine approaches and the different delivery technologies used to administer these vaccine candidates in preclinical studies.

Encapsulation of lipopeptides within liposomes: Effect of number of lipid chains, chain length and method of liposome preparation

The purpose of this study was to systematically investigate the effect of lipid chain length and number of lipid chains present on lipopeptides on their ability to be incorporated within liposomes. The peptide KAVYNFATM was synthesized and conjugated to lipoamino acids having acyl chain lengths of C8, C12 and C16. The C12 construct was also prepared in the monomeric, dimeric and trimeric form. Liposomes were prepared by two techniques: hydration of dried lipid films (Bangham method) and hydration of freeze-dried monophase systems. Encapsulation of lipopeptide within liposomes prepared by hydration of dried lipid films was incomplete in all cases ranging from an entrapment efficiency of 70% for monomeric lipoamino acids at a 5% (w/w) loading to less than 20% for di- and trimeric forms at loadings of 20% (w/w). The incomplete entrapment of lipopeptides within liposomes appeared to be a result of the different solubilities of the lipopeptide and the phospholipids in the solvent used for the preparation of the lipid film. In contrast, encapsulation of lipopeptide within liposomes prepared by hydration of freeze-dried monophase systems was high, even up to a loading of 20% (w/w) and was much less affected by the acyl chain length and number than when liposomes were prepared by hydration of dried lipid films. Freeze drying of monophase systems is better at maintaining a molecular dispersion of the lipopeptide within the solid phospholipid matrix compared to preparation of lipid film by evaporation, particularly if the solubility of the lipopeptide in solvents is markedly different from that of the polar lipids used for liposome preparation. Consequently, upon hydration, the lipopeptide is more efficiently intercalated within the phospholipid bilayers.

Concomitant helper response rescues otherwise low avidity CD8+ memory CTLs to become efficient effectors in vivo

This report seeks a means of maximizing memory CD8 T cell responses to peptide immunization. Delivery of the CD8 peptide epitope by stress protein, heat shock protein (hsp)70, results in excellent immunogenicity at the acute phase but memory responses were poor both in terms of the number of responding cells as well as their functional avidity. We demonstrate for the first time that hsp70 can also be used as a vehicle to achieve CD4 T cell responses to loaded peptide epitopes and that coimmunization with hsp70 loaded with both CD8 and CD4 peptide epitopes may increase memory up to 3-fold. Furthermore, CD8+ T cell memory responses were of higher avidity measured both by in vitro cytotoxicity assays and a new methodology that measures the avidity of CTL activity in vivo in mice. Our results emphasize that peptide immunization remains a viable approach to induce long-term CD8+ T cell function, providing steps are taken to assure appropriate stimulation of Th cell responses.