Biodegradable Cationic Polycarbonates as Vaccine Adjuvants

Potentiating humoral and cellular immunity using a novel hybrid polymer-lipid nanoparticle adjuvant for HBsAg-VLP vaccine

Aluminium adjuvants are commonly used in vaccines to stimulate the immune system, but they have limited ability to promote cellular immunity which is necessary for clearing viral infections like hepatitis B. Current adjuvants that do promote cellular immunity often have undesired side effects due to the immunostimulants they contain. In this study, a hybrid polymer lipid nanoparticle (HPLNP) was developed as an efficient adjuvant for the hepatitis B surface antigen (HBsAg) virus-like particle (VLP) vaccine to potentiate both humoral and cellular immunity. The HPLNP is composed of FDA approved polyethylene glycol-b-poly (L-lactic acid) (PEG-PLLA) polymer and cationic lipid 1, 2-dioleoyl-3-trimethylammonium-propane (DOTAP), and can be easily prepared by a one-step method. The cationic optimised vaccine formulation HBsAg/HPLNP (w/w = 1/600) can maximise the cell uptake of the antigen due to the electrostatic adsorption between the vaccine nanoparticle and the cell membrane of antigen-presenting cells. The HPLNP prolonged the retention of the antigen at the injection site and enhanced the lymph node drainage of antigen, resulting in a higher concentration of serum anti-HBsAg IgG compared to the HBsAg group or the HBsAg/Al group after the boost immunisation in mice. The HPLNP also promoted a strong Th1-driven immune response, as demonstrated by the significantly improved IgG2a/IgG1 ratio, increased production of IFN-γ, and activation of CD4 + and CD8 + T cells in the spleen and lymph nodes. Importantly, the HPLNP demonstrated no systemic toxicity during immunisation. The advantages of the HPLNP, including good biocompatibility, easy preparation, low cost, and its ability to enhance both humoral and cellular immune responses, suggest its suitability as an efficient adjuvant for protein-based vaccines such as HBsAg-VLP. These findings highlight the promising potential of the HPLNP as an HBV vaccine adjuvant, offering an alternative to aluminium adjuvants currently used in vaccines.

Potentiating the Immune Responses of HBsAg-VLP Vaccine Using a Polyphosphoester-Based Cationic Polymer Adjuvant

Virus-like particle (VLP)-based vaccines are required to be associated with a suitable adjuvant to potentiate their immune responses. Herein, we report a novel, biodegradable, and biocompatible polyphosphoester-based amphiphilic cationic polymer, poly(ethylene glycol)-b-poly(aminoethyl ethylene phosphate) (PEG-PAEEP), as a Hepatitis B surface antigen (HBsAg)-VLP vaccine adjuvant. The polymer adjuvant effectively bound with HBsAg-VLP through electrostatic interactions to form a stable vaccine nanoformulation with a net positive surface charge. The nanoformulations exhibited enhanced cellular uptake by macrophages. HBsAg-VLP/PEG-PAEEP induced a significantly higher HBsAg-specific IgG titer in mice than HBsAg-VLP alone after second immunization, indicative of the antigen-dose sparing advantage of PEG-PAEEP. Furthermore, the nanoformulations exhibited a favorable biocompatibility and in vivo tolerability. This work presents the PEG-PAEEP copolymer as a promising vaccine adjuvant and as a potentially effective alternative to aluminum adjuvants.

Recent progress in nanocomposites of carbon dioxide fixation derived reproducible biomedical polymers

In recent years, the environmental problems accompanying the extensive application of biomedical polymer materials produced from fossil fuels have attracted more and more attentions. As many biomedical polymer products are disposable, their life cycle is relatively short. Most of the used or overdue biomedical polymer products need to be burned after destruction, which increases the emission of carbon dioxide (CO₂). Developing biomedical products based on CO₂ fixation derived polymers with reproducible sources, and gradually replacing their unsustainable fossil-based counterparts, will promote the recycling of CO₂ in this field and do good to control the greenhouse effect. Unfortunately, most of the existing polymer materials from renewable raw materials have some property shortages, which make them unable to meet the gradually improved quality and property requirements of biomedical products. In order to overcome these shortages, much time and effort has been dedicated to applying nanotechnology in this field. The present paper reviews recent advances in nanocomposites of CO₂ fixation derived reproducible polymers for biomedical applications, and several promising strategies for further research directions in this field are highlighted.

A New Nano Adjuvant of PF3 Used for an Enhanced Hepatitis B Vaccine

Recombinant protein vaccines, with highly pure ingredients and good safety, are gradually replacing some attenuated and inactivated vaccines in clinical practice. However, since their low immunogenicity of the recombinant proteins, adjuvants are often needed to enhance immune response after vaccination. Aluminum adjuvant has been widely used in some vaccines for decades, it can induce strong humoral immunity, but the deficiency of cellular immunity limits its application for some vaccines. Therefore, it is urgently needed to develop novel adjuvant to increase not only humoral but also cellular immune response. To address this, we designed and prepared a new nano adjuvant (PF3) through microfluidization by the combination of saponin (Ginsenoside Rg1) and oil-in-water nano emulsion (NE) in the present study. As compared to aluminum adjuvant, PF3 had stronger humoral and cellular immune induction effect because of high cellular uptake and activization of immune response pathways. Furthermore, PF3 showed better immune enhancement and acceptable biosafety equivalent to that of aluminum adjuvant. In addition, no obvious changes of PF3 were observed in size and zeta potential after 12 weeks storage at 4 and 37°C, demonstrating its high stability in vitro. This study provided an adjuvant platform to replace traditional aluminum adjuvant in design of recombinant vaccines.

Chitosan, alginate, hyaluronic acid, gums, and β-glucan as potent adjuvants and vaccine delivery systems for viral threats including SARS-CoV-2: A review

Pathogen transmission is a widespread threat to global human health. Vaccines are very important during the outbreak of a pandemic. Destructive fractures caused by a sudden outbreak of COVID-19 have spurred vaccine production at an unprecedented rate. The strategy of an effective vaccine delivery system is opening up novel probabilities to make more immunization. Indeed, vaccination is the most successful way to prevent deaths from infectious diseases. In order to optimal immune response production or improvement in the effectiveness of vaccines, delivery systems or adjuvants are required. Natural polymers such as chitosan, alginate, hyaluronic acid, gums, and β-glucan with antiviral activity have good potential as adjuvant or delivery systems for vaccine formulation development and design vaccine delivery devices. According to the antiviral performance and immunomodulation of these biopolymers, they will play significant characters in the anti-COVID-19 field. In this mini-review, the recent progress in vaccine development by using biopolymers is presented which, provides a reference for their research on anti-COVID-19 drugs and vaccines.