Mycobacterium tuberculosis Ag85b:hfcγ1 recombinant fusion protein as a selective receptor-dependent delivery system for antigen presentation

Novel tuberculosis vaccines based on TB10.4 and Ag85B: State-of-art and advocacy for good practices

Tuberculosis (TB) has plagued humanity in numerous devastating forms for centuries and remains a significant health challenge. Mycobacterium tuberculosis (Mtb), the bacterium responsible for TB, was the leading cause of death among infectious agents until the COVID-19 pandemic emerged. Immunization with the bacillus Calmette-Guérin (BCG) vaccine is one of the primary strategies to mitigate the risk of TB. Despite its widespread use, the current BCG vaccine has limited efficacy, particularly in adults. This review focuses on the rational design of vaccine candidates targeting the antigens TB10.4 and Ag85B. The review discusses the roles of TB10.4 and Ag85B in the virulence of Mtb and notes challenges in their production. Additionally, various protein conjugation strategies to enhance immunogenicity, including linking these antigens to glycans and adjuvants, are considered, as well as the most appropriate analytical methods for characterizing recombinant antigenic proteins and their conjugates. Finally, the associated challenges in developing a vaccine encompassing specific glycans and protein components were highlighted. We claim that using standardized procedures and detailed reporting in protein production and chemical modification can improve the reproducibility and rationalization of biological results. By adhering to these guidelines, the goal of developing an effective vaccine against TB will be best achieved.

Production and Evaluation of Ag85B:HspX:hFcγ1 Immunogenicity as an Fc Fusion Recombinant Multi-Stage Vaccine Candidate Against Mycobacterium tuberculosis

An urgent need is to introduce an effective vaccine against Mycobacterium tuberculosis (M.tb) infection. In the present study, a multi-stage M.tb immunodominant Fcγ1 fusion protein (Ag85B:HspX:hFcγ1) was designed and produced, and the immunogenicity of purified protein was evaluated. This recombinant fusion protein was produced in the Pichia pastoris expression system. The HiTrap-rPA column affinity chromatography purified and confirmed the fusion protein using ELISA and Western blotting methods. The co-localisation assay was used to confirm its proper folding and function. IFN-γ, IL-12, IL-4, and TGF-β expression in C57BL/6 mice then evaluated the immunogenicity of the construct in the presence and absence of BCG. After expression optimisation, medium-scale production and the Western blotting test confirmed suitable production of Ag85B:HspX:hFcγ1. The co-localisation results on antigen-presenting cells (APCs) showed that Ag85B:HspX:hFcγ1 properly folded and bound to hFcγRI. This strong co-localisation with its receptor can confirm inducing proper Th1 responses. The in vivo immunisation assay showed no difference in the expression of IL-4 but a substantial increase in the expression of IFN-γ and IL-12 (P ≤ 0.02) and a moderate increase in TGF-β (P = 0.05). In vivo immunisation assay revealed that Th1-inducing pathways have been stimulated, as IFN-γ and IL-12 strongly, and TGF-β expression moderately increased in Ag85B:HspX:hFcγ1 group and Ag85B:HspX:hFcγ1+BCG. Furthermore, the production of IFN-γ from splenocytes in the Ag85B:HspX:hFcγ1 group was enormously higher than in other treatments. Therefore, this Fc fusion protein can make a selective multi-stage delivery system for inducing appropriate Th1 responses and is used as a subunit vaccine alone or in combination with others.

Application of Computational Techniques in Antibody Fc-Fused Molecule Design for Therapeutics

Since the advent of hybridoma technology in the year 1975, it took a decade to witness the first approved monoclonal antibody Orthoclone OKT39 (muromonab-CD3) in the year 1986. Since then, continuous strides have been made to engineer antibodies for specific desired effects. The engineering efforts were not confined to only the variable domains of the antibody but also included the fragment crystallizable (Fc) region that influences the immune response and serum half-life. Engineering of the Fc fragment would have a profound effect on the therapeutic dose, antibody-dependent cell-mediated cytotoxicity as well as antibody-dependent cellular phagocytosis. The integration of computational techniques into antibody engineering designs has allowed for the generation of testable hypotheses and guided the rational antibody design framework prior to further experimental evaluations. In this article, we discuss the recent works in the Fc-fused molecule design that involves computational techniques. We also summarize the usefulness of in silico techniques to aid Fc-fused molecule design and analysis for the therapeutics application.

Biosensors; nanomaterial-based methods in diagnosing of Mycobacterium tuberculosis

Diagnosis of Mycobacterium tuberculosis (Mtb) before the progression of pulmonary infection can be very effective in its early treatment. The Mtb grows so slowly that it takes about 6-8 weeks to be diagnosed even using sensitive cell culture methods. The main opponent in tuberculosis (TB) and nontuberculous mycobacterial (NTM) epidemiology, like in all contagious diseases, is to pinpoint the source of infection and reveal its transmission and dispersion ways in the environment. It is crucial to be able to distinguish and monitor specific mycobacterium strains in order to do this. In food analysis, clinical diagnosis, environmental monitoring, and bioprocess, biosensing technologies have been improved to manage and detect Mtb. Biosensors are progressively being considered pioneering tools for point-of-care diagnostics in Mtb discoveries. In this review, we present an epitome of recent developments of biosensing technologies for M. tuberculosis detection, which are categorized on the basis of types of electrochemical, Fluorescent, Photo-thermal, Lateral Flow, Magneto-resistive, Laser, Plasmonic, and Optic biosensors.

Construction and expression of Mycobacterium tuberculosis fusion protein AR2 and its immunogenicity in combination with various adjuvants to form vaccine

Tuberculosis (TB) is recognized as a highly infectious disease worldwide, and Bacille Calmette-Guerin (BCG) remains the only TB vaccine licensed for clinical use. As there is little evidence that BCG is effective in adults, there is an urgent need for a safe and effective vaccine to control TB in adults. In this study, we tested the immunomodulatory efficiency of the fusion protein AR2. whole blood IFN-γ release assay (WBIA) was used to detect antigen specificity. The immunogenicity of the vaccine was tested in C57BL/6 mice, and confirmed by enzyme-linked immunosorbent assay (ELISA), flow cytometry, and qRT-PCR. The fusion protein AR2 was successfully constructed and expressed. The level of IFN-γ in the peripheral blood of subjects stimulated by AR2 was significantly higher than in those induced by all subcomponent proteins. AR2-specific IgG and the Th1 cytokines IFN-γ, TNF-α, and iNOS were significantly increased in the group treated with the fusion protein and compound adjuvant (AR2+DMC). Likewise, the number of IFN-γ⁺ CD4⁺, IFN-γ⁺CD8⁺, and IL-4⁺ CD8⁺ T lymphocytes increased significantly. The combination of the fusion protein and the compound adjuvant (AR2+DMC) may be a suitable candidate for an enhanced TB vaccine. This study provides theoretical and experimental support for future research to enhance the effectiveness of TB vaccines and provides an experimental basis for evaluating the influence of different adjuvants on vaccine efficacy.

Genomic Characteristics Revealed Plasmid-Mediated Pathogenicity and Ubiquitous Rifamycin Resistance of Rhodococcus equi

Rhodococcus equi is a zoonotic pathogen that can cause fatal disease in patients who are immunocompromised. At present, the epidemiology and pathogenic mechanisms of R. equi infection are not clear. This study characterized the genomes of 53 R. equi strains from different sources. Pan-genome analysis showed that all R. equi strains contained 11481 pan genes, including 3690 core genes and 602 ~ 1079 accessory genes. Functional annotation of pan genome focused on the genes related to basic lifestyle, such as the storage and expression of metabolic and genetic information. Phylogenetic analysis based on pan-genome showed that the R. equi strains were clustered into six clades, which was not directly related to the isolation location and host source. Also, a total of 84 virulence genes were predicted in 53 R. equi strains. These virulence factors can be divided into 20 categories related to substance metabolism, secreted protein and immune escape. Meanwhile, six antibiotic resistance genes (RbpA, tetA (33), erm (46), sul1, qacEdelta 1 and aadA9) were detected, and all strains carried RbpA related to rifamycin resistance. In addition, 28 plasmids were found in the 53 R. equi strains, belonging to Type-A (n = 14), Type-B (n = 8) and Type-N (n = 6), respectively. The genetic structures of the same type of plasmid were highly similar. In conclusion, R. equi strains show different genomic characteristics, virulence-related genes, potential drug resistance and virulence plasmid structures, which may be conducive to the evolution of its pathogenesis.

Rapid detection of Mycobacterium tuberculosis based on antigen 85B via real-time recombinase polymerase amplification

Tuberculosis (TB), as a common infectious disease, still remains a severe challenge to public health. Due to the unsatisfied clinical needs of currently available diagnostic vehicles, it is desired to establish a new approach for universally detecting Mycobacterium tuberculosis. Herein, we designed a real-time recombinase polymerase amplification (RPA) technology for identifying M. tuberculosis within 20 min at 39°C via custom-designed oligonucleotide primers and probe, which could specifically target antigen 85B (Ag85B). Particularly, the primers F4-R4 produced the fastest fluorescence signal with the probe among four pairs of designed primers in the RPA assays. The optimal primers/probe combination could effectively identify M. tuberculosis with the detection limit of 4·0 copies per μl, as it could not show a positive signal for the genomic DNA from other mycobacteria or pathogens. The Ag85B-based RPA could determine the genomic DNA extracted from M. tuberculosis with high reliability (100%, 22/22). More importantly, when testing clinical sputum samples, the real-time RPA displayed an admirable sensitivity (90%, 95% CI: 80·0-96·0%) and specificity (98%, 95% CI: 89·0-100·0%) compared to traditional smear microscopy, which was similar to the assay of Xpert MTB/RIF. This real-time RPA based Ag85B provides a promising strategy for the rapid and universal diagnosis of TB.

In Silico Design of Multi-Epitope ESAT-6:Ag85b:Fcγ2a Fusion Protein as a Novel Candidate for Tuberculosis Vaccine

: Mycobacterium tuberculosis (MTB), which is the causative agent of tuberculosis (TB), is among the most important infectious bacteria with high morbidity and mortality rates worldwide. Bacilli Calmette-Guerin (BCG) vaccine has been discovered for about a century, and it is considered as a major vaccine for humans. However, some factors, such as its attenuated nature and its inefficacy against the latent form of the disease, have led to the use of alternative vaccines. Multi-epitope subunit vaccines are new-generation vaccines that are being developed in clinical trial phases. For the production of a subunit vaccine, the selection of immunodominant antigens and targeted delivery systems to antigen presenting cells (APCs) are considered as basic parameters. In the present study, we designed the novel multi-epitope ESAT-6:Ag85B:Fcγ2a, which was evaluated completely by various online tools as an optimum vaccine against TB. The early secreted antigenic target of 6 kDa (ESAT-6) and antigen 85B (Ag85B) are two immunodominant antigens, and Fcγ2a is a targeted delivery system. This vaccine candidate can be used for future preclinical studies.