Combined Poly(Lactide-Co-Glycolide) Microspheres Containing Diphtheria Toxoid for a Single-shot Immunization

Evaluation of Biodegradable Microparticles for Mucosal Vaccination Against Diphtheria Toxoid: Nasal Efficacy Studies in Guinea Pigs

Objectives

In this study, poly-(ɛ-caprolactone) (PCL) and poly-(lactic-co-glycolic acid) (PLGA) microparticles encapsulating diphtheria toxoid (DT) were investigated for their potential as a mucosal vaccine delivery system.

Materials and Methods

Antigen-containing microparticles were prepared using the double emulsion (w/o/w) solvent evaporation method.

Results

The average geometric diameter of the particles was found to be between 7 and 24 µm, which is suitable for uptake by the antigen-presenting cells in the nasal mucosa. Although the differences were insignificant, the PLGA polymer-containing formulations exhibited the highest encapsulation efficiency. Microparticle formulations, prepared with both PLGA and PCL polymers, were successfully produced at high production yields. The in vitro release profile was presented as a biexponential process with an initial burst effect due to the release of the protein adsorbed on the microsphere surface, and the subsequent sustained release profile is the result of protein diffusion through the channels or pores formed in the polymer matrix. DT-loaded microparticles, DT solution in phosphate-buffered saline (PBS), and empty microparticles (control) were administered via nasal route and subcutaneously to guinea pigs. The antibody content of each serum sample was determined using an enzyme-linked immunosorbent assay (ELISA).

Conclusion

Absorbance values of the ELISA test showed that PLGA- and PCL-bearing microparticles could stimulate an adequate systemic immune response with intranasal vaccination. In addition, PLGA and PCL microparticles resulted in significantly increased IgG titers with intranasal administration as a booster dose following subcutaneous administration. PCL polymer elicited a high immune response compared with PLGA polymer (p <0.05).

Recent advancements in single dose slow-release devices for prophylactic vaccines

Single dose slow-release vaccines herald a new era in vaccine administration. An ideal device for slow-release vaccine delivery would be minimally invasive and self-administered, making these approaches an attractive alternative for mass vaccination programs, particularly during the time of a pandemic. In this review article, we discuss the latest advances in this field, specifically for prophylactic vaccines able to prevent infectious diseases. Recent studies have found that slow-release vaccines elicit better immune responses and often do not require cold chain transportation and storage, thus drastically reducing the cost, streamlining distribution, and improving efficacy. This promise has attracted significant attention, especially when poor patient compliance of the standard multidose vaccine regimes is considered. Single dose slow-release vaccines are the next generation of vaccine tools that could overcome most of the shortcomings of present vaccination programs and be the next platform technology to combat future pandemics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

The sixth revolution in pediatric vaccinology: immunoengineering and delivery systems

Infection is the predominant cause of mortality in early life, and immunization is the most promising biomedical intervention to reduce this burden. However, very young infants fail to respond optimally to most vaccines currently in use, especially neonates. In 2005, Stanley Plotkin proposed that new delivery systems would spur a new revolution in pediatric vaccinology, just as attenuation, inactivation, cell culture of viruses, genetic engineering, and adjuvantation had done in preceding decades. Recent advances in the field of immunoengineering, which is evolving alongside vaccinology, have begun to increasingly influence vaccine formulation design. Historically, the particulate nature of materials used in many vaccine formulations was empiric, often because of the need to stabilize antigens or reduce endotoxin levels. However, present vaccine delivery systems are rationally engineered to mimic the size, shape, and surface chemistry of pathogens, and are therefore often referred to as "pathogen-like particles". More than a decade from his original assessment, we re-assess Plotkin's prediction. In addition, we highlight how immunoengineering and advanced delivery systems may be uniquely capable of enhancing vaccine responses in vulnerable populations, such as infants. IMPACT: Immunoengineering and advanced delivery systems are leading to new developments in pediatric vaccinology. Summarizes delivery systems currently in use and development, and prospects for the future. Broad overview of immunoengineering's impact on vaccinology, catering to Pediatric Clinicians and Immunologists.