A multiple T cell epitope comprising DNA vaccine boosts the protective efficacy of Bacillus Calmette-Guérin (BCG) against Mycobacterium tuberculosis

Protective RNA nanovaccines against Mycobacterium avium subspecies hominissuis

The induction of an effective immune response is critical for the success of mRNA-based therapeutics. Here, we developed a nanoadjuvant system compromised of Quil-A and DOTAP (dioleoyl 3 trimethylammonium propane), hence named QTAP, for the efficient delivery of mRNA vaccine constructs into cells. Electron microscopy indicated that the complexation of mRNA with QTAP forms nanoparticles with an average size of 75 nm and which have ~90% encapsulation efficiency. The incorporation of pseudouridine-modified mRNA resulted in higher transfection efficiency and protein translation with low cytotoxicity than unmodified mRNA. When QTAP-mRNA or QTAP alone transfected macrophages, pro-inflammatory pathways (e.g., NLRP3, NF-kb, and MyD88) were upregulated, an indication of macrophage activation. In C57Bl/6 mice, QTAP nanovaccines encoding Ag85B and Hsp70 transcripts (QTAP-85B+H70) were able to elicit robust IgG antibody and IFN- ɣ, TNF-α, IL-2, and IL-17 cytokines responses. Following aerosol challenge with a clinical isolate of M. avium ss. hominissuis (M.ah), a significant reduction of mycobacterial counts was observed in lungs and spleens of only immunized animals at both 4- and 8-weeks post-challenge. As expected, reduced levels of M. ah were associated with diminished histological lesions and robust cell-mediated immunity. Interestingly, polyfunctional T-cells expressing IFN- ɣ, IL-2, and TNF- α were detected at 8 but not 4 weeks post-challenge. Overall, our analysis indicated that QTAP is a highly efficient transfection agent and could improve the immunogenicity of mRNA vaccines against pulmonary M. ah, an infection of significant public health importance, especially to the elderly and to those who are immune compromised.

Synergistic antibacterial effects of ultrasound combined nanoparticles encapsulated with cellulase and levofloxacin on Bacillus Calmette-Guérin biofilms

Tuberculosis is a chronic infectious disease, the treatment of which is challenging due to the formation of cellulose-containing biofilms by Mycobacterium tuberculosis (MTB). Herein, a composite nanoparticle loaded with cellulase (CL) and levofloxacin (LEV) (CL@LEV-NPs) was fabricated and then combined with ultrasound (US) irradiation to promote chemotherapy and sonodynamic antimicrobial effects on Bacillus Calmette-Guérin bacteria (BCG, a mode of MTB) biofilms. The CL@LEV-NPs containing polylactic acid-glycolic acid (PLGA) as the shell and CL and LEV as the core were encapsulated via double ultrasonic emulsification. The synthesized CL@LEV-NPs were uniformly round with an average diameter of 196.2 ± 2.89 nm, and the zeta potential of -14.96 ± 5.35 mV, displaying high biosafety and sonodynamic properties. Then, BCG biofilms were treated with ultrasound and CL@LEV-NPs separately or synergistically in vivo and in vitro. We found that ultrasound significantly promoted biofilms permeability and activated CL@LEV-NPs to generate large amounts of reactive oxygen species (ROS) in biofilms. The combined treatment of CL@LEV-NPs and US exhibited excellent anti-biofilm effects, as shown by significant reduction of biofilm biomass value and viability, destruction of biofilm architecture in vitro, elimination of biofilms from subcutaneous implant, and remission of local inflammation in vivo. Our study suggested that US combined with composite drug-loaded nanoparticles would be a novel non-invasive, safe, and effective treatment modality for the elimination of biofilm-associated infections caused by MTB.

Wnt5a regulates autophagy in Bacille Calmette-Guérin (BCG)-Infected pulmonary epithelial cells

Autophagy functions as a critical process that can suppress the proliferation of Mycobacterium tuberculosis (Mtb) within infected host cells. Wnt5a is a secreted protein that plays a range of physiological functions, activating several signaling pathways and thereby controlling cellular responses to particular stimuli. The importance of Wnt5a as a regulator of protection against Mtb infection, however, has yet to be fully characterized. Here, changes in murine pulmonary epithelial-like TC-1 cell morphology, autophagy, the Wnt/Ca²⁺ signaling pathway, and the mTOR autophagy pathway were analyzed following infection with the Mtb model pathogen Bacille Calmette-Guerin (BCG) in order to understand the regulatory role of Wnt5a in this context. These experiments revealed that Wnt5a was upregulated and autophagy was enhanced in TC-1 cells infected with BCG, and Wnt5a overexpression was found to drive BCG-induced autophagy in these cells upon infection, whereas the inhibition or knockdown of Wnt5a yielded the opposite effect. At the mechanistic level, Wnt5a was found to mediate non-canonical Wnt/Ca²⁺ signaling and thereby inhibit mTOR-dependent pathway activation, promoting autophagic induction within BCG-infected TC-1 cells. These data offer new insight regarding how Wnt5a influences Mtb-induced autophagy within pulmonary epithelial cells, providing a foundation for further research exploring the immunological control of this infection through the modulation of autophagy.

Advance in strategies to build efficient vaccines against tuberculosis

Tuberculosis is a chronic consumptive infectious disease, which can cause great damage to human and animal health all over the world. The emergence of multi-drug resistant strains, the unstable protective effect of Bacillus Calmette-Guérin (BCG) vaccine on adults, and the mixed infection with HIV all warn people to exploit new approaches for conquering tuberculosis. At present, there has been significant progress in developing tuberculosis vaccines, such as improved BCG vaccine, subunit vaccine, DNA vaccine, live attenuated vaccine and inactivated vaccine. Among these candidate vaccines, there are some promising vaccines to improve or replace BCG vaccine effect. Meanwhile, the application of adjuvants, prime-boost strategy, immunoinformatic tools and targeting components have been studied concentratedly, and verified as valid means of raising the efficiency of tuberculosis vaccines as well. In this paper, the latest advance in tuberculosis vaccines in recent years is reviewed to provide reliable information for future tuberculosis prevention and treatment.

Mycobacterium tuberculosis dormancy regulon proteins Rv2627c and Rv2628 as Toll like receptor agonist and as potential adjuvant

During latency, DosR proteins of Mycobacterium tuberculosis (M.tb) get activated and help the bacterium to remain dormant. We have shown earlier that 2 such proteins Rv2627c and Rv2628 are immunogenic and induce a TH1 kind of immune response. In this study, through in-vitro experiments we have confirmed that Rv2627c and Rv2628 proteins act as protein Toll-Like Receptor (TLR) agonist-adjuvant. Rv2627c and Rv2628 stimulated THP-1 macrophages showed an increased expression of TLR2, TLR4 and co-stimulatory molecules CD40, CD80, CD86 and antigen presenting molecule HLA-DR. Further studies also found enhanced expression of downstream signaling molecules of TLR activation like MyD88, NF-κB-p65 and pro-inflammatory cytokines. Inhibition studies using TLR blocking antibodies decreased the expression of co-stimulatory molecules, MyD88, NF-κB-p65, and pro-inflammatory cytokines. Rv2627c and Rv2628 stimulation of HEK-TLR2 reporter cell line confirmed the interaction of these proteins with TLR2. Moreover, molecular docking and simulations of Rv2627c and Rv2628 proteins with TLR2 and TLR4 showed stable interactions. The adjuvant activity of Rv2628 was further validated by a protein adjuvanted with pre-clinically validated peptides as multi-epitope vaccine construct which showed good binding with TLR2 and TLR4 and activate dendritic cells and induce sustained pro-inflammatory cytokine response by C-ImmSim analysis. We propose that our vaccine construct will produce a better immune response than BCG and can be taken up as a post-exposure therapeutic subunit vaccine along with standard TB therapy. We also anticipate that our construct can be taken up as a protein adjuvant with other vaccine candidates as these can activate macrophages through TLR signaling.

Chitosan nanoparticles containing fusion protein (Hspx–PPE44–EsxV) and resiquimod adjuvant (HPERC) as a novel booster vaccine for Mycobacterium tuberculosis

This study attempted to explore the immunogenicity of chitosan nanoparticles containing fusion protein (Hspx–PPE44–EsxV; HPE) and resiquimod adjuvant (HPERC) in BALB/c mice. HPE was initially expressed in E. coli BL21 cells. HPE and resiquimod adjuvant were then encapsulated in chitosan nanoparticles (HPERC). One group of mice were subcutaneously vaccinated on days 0, 14, and 28 with HPERC, and the other group was primed with bacilli Calmette-Guérin (BCG) on day 0 and then boosted with HPERC on days 14 and 28. Two weeks after the last injection, IFN-γ, IL-4, and IL-17 in spleen cell culture supernatants, and IgG2a and IgG1 titers in sera were measured. HPERC size was 130.84 ± 12.08 nm ( n = 5). Zeta potential of HPERC was 29 ± 4 mv. The highest IFN-γ concentration was detected in BCG-primed mice that were boosted with HPERC. In addition, IL-17 production was significantly increased in all groups compared with that of control, except in those that received nanoparticle (NP), adjuvant (ADJ), NP/ADJ, and fusion protein (Hspx–PPE44–EsxV) (HPE). Comparison of IFN-γ and IL-4 concentration determined that Th1 was activated in BCG-primed and HPERC-boosted group in comparison to the other groups. No significant difference in concentration of IL-4 was observed between groups receiving HPERC and BCG-primed and HPERC-boosted group in comparison to group BCG. Concentrations of IgG2a and IgG1 also increased compared to the control group and the rate of IgG2a was higher compared to IgG1. Chitosan containing HPERC vaccine could induce a high level of specific cytokines in mice. The group of mice which first received BCG and then HPERC as booster vaccine could produce significant amounts of IFN-γ, IL-17, and IgG2a.

Enhanced immunogenicity of the tuberculosis subunit Rv0572c vaccine delivered in DMT liposome adjuvant as a BCG-booster

COVID-19 has affected the progress made in the prevention and treatment of tuberculosis (TB); hence, the mortality of tuberculosis has risen. Different strategies-based novel TB vaccine candidates have been developed. This study identifies strategies to overcome the limitations of Bacille Calmette-Guérin (BCG) in preventing latent infection and reactivation of TB. The latency antigen Rv0572c was selected based on the mechanism of interaction between Mycobacterium tuberculosis and its host. The rRv0572c protein was used to stimulate whole blood samples derived from patients with clinically diagnosed active TB (ATBs) or latent TB infections (LTBIs) and healthy control (HCs) donors, confirming that this protein can be recognized by T cells in patients with TB, especially LTBIs. C57BL/6 mice were used to investigate the immunogenicity of the rRv0572c protein emulsified in the liposome adjuvant dimethyldioctadecylammonium [DDA], monophosphoryl lipid A [MPLA], trehalose-6, 6′-dibehenate [TDB] (DMT). The results demonstrated that rRv0572c/DMT could boost BCG-primed mice to induce antigen-specific CD4⁺ T cell production and generate functional T cells dominated by antigen-specific CD8⁺ T cells. The rRv0572c/DMT vaccine could also trigger limited Th2 humoral immune responses. These findings suggest that rRv0572c/DMT is a potential subunit vaccine candidate that can be used as a booster vaccine for BCG.

Peptide-Based Vaccines for Tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. As a result of the coronavirus disease 2019 (COVID-19) pandemic, the global TB mortality rate in 2020 is rising, making TB prevention and control more challenging. Vaccination has been considered the best approach to reduce the TB burden. Unfortunately, BCG, the only TB vaccine currently approved for use, offers some protection against childhood TB but is less effective in adults. Therefore, it is urgent to develop new TB vaccines that are more effective than BCG. Accumulating data indicated that peptides or epitopes play essential roles in bridging innate and adaptive immunity and triggering adaptive immunity. Furthermore, innovations in bioinformatics, immunoinformatics, synthetic technologies, new materials, and transgenic animal models have put wings on the research of peptide-based vaccines for TB. Hence, this review seeks to give an overview of current tools that can be used to design a peptide-based vaccine, the research status of peptide-based vaccines for TB, protein-based bacterial vaccine delivery systems, and animal models for the peptide-based vaccines. These explorations will provide approaches and strategies for developing safer and more effective peptide-based vaccines and contribute to achieving the WHO’s End TB Strategy.

Early Lesion of Post-Primary Tuberculosis: Subclinical Driver of Disease and Target for Vaccines and Host-Directed Therapies

The characteristic lesion of primary tuberculosis is the granuloma as is widely studied in human tissues and animal models. Post-primary tuberculosis is different. It develops only in human lungs and begins as a prolonged subclinical obstructive lobular pneumonia that slowly accumulates mycobacterial antigens and host lipids in alveolar macrophages with nearby highly sensitized T cells. After several months, the lesions undergo necrosis to produce a mass of caseous pneumonia large enough to fragment and be coughed out to produce a cavity or be retained as the focus of a post-primary granuloma. Bacteria grow massively on the cavity wall where they can be coughed out to infect new people. Here we extend these findings with the demonstration of secreted mycobacterial antigens, but not acid fast bacilli (AFB) of M. tuberculosis in the cytoplasm of ciliated bronchiolar epithelium and alveolar pneumocytes in association with elements of the programmed death ligand 1 (PD-L1), cyclo-oxygenase (COX)-2, and fatty acid synthase (FAS) pathways in the early lesion. This suggests that M. tuberculosis uses its secreted antigens to coordinate prolonged subclinical development of the early lesions in preparation for a necrotizing reaction sufficient to produce a cavity, post-primary granulomas, and fibrocaseous disease.

Immunotherapeutic Role of NOD-2 and TLR-4 Signaling as an Adjunct to Antituberculosis Chemotherapy

Tuberculosis (TB) treatment is lengthy and inflicted with severe side-effects. Here, we attempted a novel strategy to reinforce host immunity through NOD-like receptor (NOD-2) and Toll-like receptor (TLR-4) signaling in the murine model of TB. Intriguingly, we noticed that it not only bolstered the immunity but also reduced the dose and duration of rifampicin and isoniazid therapy. Further, we observed expansion in the pool of effector (CD44^hi, CD62L^lo, CD127^hi) and central (CD44^hi, CD62L^hi, CD127^hi) memory CD4 T cells and CD8 T cells and increased the intracellular killing of Mycobacterium tuberculosis (Mtb) by activated dendritic cells [CD86^hi, CD40^hi, IL-6^hi, IL-12^hi, TNF-α^hi, nitric oxide (NO)^hi] with significant reduction in Mtb load in the lungs and spleen of infected animals. We infer that the signaling through NOD-2 and TLR-4 may be an important approach to reduce the dose and duration of the drugs to treat TB.