Immunogenicity of HspX/EsxS fusion protein of Mycobacterium tuberculosis along with ISCOMATRIX and PLUSCOM nano-adjuvants after subcutaneous administration in animal model

Advanced nanoscale delivery systems for mRNA-based vaccines

The effectiveness of messenger RNA (mRNA) vaccines, especially those designed for COVID-19, relies heavily on sophisticated delivery systems that ensure efficient delivery of mRNA to target cells. A variety of nanoscale vaccine delivery systems (VDSs) have been explored for this purpose, including lipid nanoparticles (LNPs), liposomes, and polymeric nanoparticles made from biocompatible polymers such as poly(lactic-co-glycolic acid), as well as viral vectors and lipid-polymer hybrid complexes. Among these, LNPs are particularly notable for their efficiency in encapsulating and protecting mRNA. These nanoscale VDSs can be engineered to enhance stability and facilitate uptake by cells. The choice of delivery system depends on factors like the specific mRNA vaccine, target cell types, stability requirements, and desired immune response. In this review, we shed light on recent advances in delivery mechanisms for self-amplifying RNA (saRNA) vaccines, emphasizing groundbreaking studies on nanoscale delivery systems aimed at improving the efficacy and safety of mRNA/saRNA vaccines.

Advances in protein subunit vaccines against tuberculosis

Tuberculosis (TB), also known as the "White Plague", is caused by Mycobacterium tuberculosis (Mtb). Before the COVID-19 epidemic, TB had the highest mortality rate of any single infectious disease. Vaccination is considered one of the most effective strategies for controlling TB. Despite the limitations of the Bacille Calmette-Guérin (BCG) vaccine in terms of protection against TB among adults, it is currently the only licensed TB vaccine. Recently, with the evolution of bioinformatics and structural biology techniques to screen and optimize protective antigens of Mtb, the tremendous potential of protein subunit vaccines is being exploited. Multistage subunit vaccines obtained by fusing immunodominant antigens from different stages of TB infection are being used both to prevent and to treat TB. Additionally, the development of novel adjuvants is compensating for weaknesses of immunogenicity, which is conducive to the flourishing of subunit vaccines. With advances in the development of animal models, preclinical vaccine protection assessments are becoming increasingly accurate. This review summarizes progress in the research of protein subunit TB vaccines during the past decades to facilitate the further optimization of protein subunit vaccines that may eradicate TB.

Fighting Tuberculosis: In Search of a BCG Replacement

Tuberculosis is one of the most threatening infectious diseases and represents an important and significant reason for mortality in high-burden regions. The only licensed vaccine, BCG, is hardly capable of establishing long-term tuberculosis protection and is highly variable in its effectiveness. Even after 100 years of BCG use and research, we still cannot unequivocally answer the question of which immune correlates of protection are crucial to prevent Mycobacterium tuberculosis (Mtb) infection or the progression of the disease. The development of a new vaccine against tuberculosis arises a nontrivial scientific challenge caused by several specific features of the intracellular lifestyle of Mtb and the ability of the pathogen to manipulate host immunity. The purpose of this review is to discuss promising strategies and the possibilities of creating a new vaccine that could replace BCG and provide greater protection. The considered approaches include supplementing mycobacterial strains with immunodominant antigens and genetic engineering aimed at altering the interaction between the bacterium and the host cell, such as the exit from the phagosome. Improved new vaccine strains based on BCG and Mtb undergoing clinical evaluation are also overviewed.

A genetically engineered, stem-cell-derived cellular vaccine

Despite rapid clinical translation of COVID-19 vaccines in response to the global pandemic, an opportunity remains for vaccine technology innovation to address current limitations and meet challenges of inevitable future pandemics. We describe a universal vaccine cell (UVC) genetically engineered to mimic natural physiological immunity induced upon viral infection of host cells. Cells engineered to express the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike as a representative viral antigen induce robust neutralizing antibodies in immunized non-human primates. Similar titers generated in this established non-human primate (NHP) model have translated into protective human neutralizing antibody levels in SARS-CoV-2-vaccinated individuals. Animals vaccinated with ancestral spike antigens and subsequently challenged with SARS-CoV-2 Delta variant in a heterologous challenge have an approximately 3 log decrease in viral subgenomic RNA in the lungs. This cellular vaccine is designed as a scalable cell line with a modular poly-antigenic payload, allowing for rapid, large-scale clinical manufacturing and use in an evolving viral variant environment.

A new poly(I:C)-decorated PLGA-PEG nanoparticle promotes Mycobacterium tuberculosis fusion protein to induce comprehensive immune responses in mice intranasally

Protein-based subunit vaccine against tuberculosis (TB) is regarded as safer but with lower immunogenicity. To investigate effective adjuvant to improve the immunogenicity of TB subunit vaccine, we modified ploy(I:C) onto PLGA-PEG copolymer nanoparticle with polydopamine to produce a new nanoparticle adjuvant named "PLGA-PEG-poly(I:C)" (NP). M. tuberculosis fusion proteins Mtb10.4-HspX and ESAT-6-Rv2626c (M4) were encapsulated in the nanoparticles to produce the NP/M4 subunit vaccine. The PLGA-PEG/M4 nanoparticle was 200.21 ± 1.07 nm in diameter, and the polydispersity index (PDI) was 0.127 ± 0.02. Following modification with poly(I:C) by polydopamine, the NP/M4 was administered to C57BL/6 female mice intranasally and the immune responses were evaluated. The NP/M4 significantly induced antigen-specific CD4⁺ T cells proliferation, IL-2 and IFN-γ production. In addition, the NP/M4 could promote the production of antigen-specific IgG, IgG1, IgG2c in serum, and sIgA in lung washings. Overall, our results indicated that the NP would be a potential TB subunit vaccine adjuvant with the ability to induce strong Th1-type cell-mediated immunity and humoral immune responses.