New vaccines for tuberculosis

BCG infection dose guides dendritic cell migration and T cell priming in the draining lymph node

In contrast to delayed-type hypersensitivity (DTH) and other hallmark reactions of cell-mediated immunity that correlate with vaccine-mediated protection against Mycobacterium tuberculosis, the contribution of vaccine dose on responses that emerge early after infection in the skin with Bacille Calmette-Guérin (BCG) is not well understood. We used a mouse model of BCG skin infection to study the effect of BCG dose on the relocation of skin Dendritic cells (DCs) to draining lymph node (DLN). Mycobacterium antigen 85B-specific CD4+ P25 T cell-receptor transgenic (P25 TCRTg) cells were used to probe priming to BCG in DLN. DC migration and T cell priming were studied across BCG inocula that varied up to 100-fold (104 to 106 Colony-forming units-CFUs). In line with earlier results in guinea pigs, DTH reaction in our model correlated with BCG dose. Importantly, priming of P25 TCRTg cells in DLN also escalated in a dose-dependent manner, peaking at day 6 after infection. Similar dose-escalation effects were seen for DC migration from infected skin and the accompanying transport of BCG to the DLN. BCG-triggered upregulation of co-stimulatory molecules on migratory DCs was restricted to the first 24 hour after infection and was independent of BCG dose over a 10-fold range (105 to 106 CFUs). The dose seemed to be a determinant of the number of total skin DCs that move to the DLN. In summary, our results support the use of higher BCG doses to detect robust DC migration and T cell priming.

Tuberculosis vaccine developments and efficient delivery systems: A comprehensive appraisal

Despite the widespread use of the Bacillus Calmette-Guérin (BCG) vaccine, Mycobacterium tuberculosis (MTB) continues to be a global burden. Vaccination has been proposed to prevent and treat tuberculosis (TB) infection, and several of them are in different phases of clinical trials. Though vaccine production is in progress but requires more attention. There are several TB vaccines in the trial phase, most of which are based on a combination of proteins/adjuvants or recombinant viral vectors used for selected MTB antigens. In this review, we attempted to discuss different types of TB vaccines based on the vaccine composition, the immune responses generated, and their clinical trial phases. Furthermore, we have briefly overviewed the effective delivery systems used for the TB vaccine and their effectiveness in different vaccines.

Clinical manifestations and immune response to tuberculosis

Tuberculosis is a far-reaching, high-impact disease. It is among the top ten causes of death worldwide caused by a single infectious agent; 1.6 million tuberculosis-related deaths were reported in 2021 and it has been estimated that a third of the world's population are carriers of the tuberculosis bacillus but do not develop active disease. Several authors have attributed this to hosts' differential immune response in which cellular and humoral components are involved, along with cytokines and chemokines. Ascertaining the relationship between TB development's clinical manifestations and an immune response should increase understanding of tuberculosis pathophysiological and immunological mechanisms and correlating such material with protection against Mycobacterium tuberculosis. Tuberculosis continues to be a major public health problem globally. Mortality rates have not decreased significantly; rather, they are increasing. This review has thus been aimed at deepening knowledge regarding tuberculosis by examining published material related to an immune response against Mycobacterium tuberculosis, mycobacterial evasion mechanisms regarding such response and the relationship between pulmonary and extrapulmonary clinical manifestations induced by this bacterium which are related to inflammation associated with tuberculosis dissemination through different routes.

6-C-Linked trehalose glycolipids signal through Mincle and exhibit potent adjuvant activity

Many studies have investigated the Mincle-mediated agonist activity of α,α'-trehalose-6,6́-glycolipids, however, none have considered how the position, or absence, of the ester moiety influences Mincle-mediated agonist activity. We prepared a variety of 6-C-linked α,α'-trehalose glycolipids containing inverted esters, ketone, carboxy or no carbonyl moieties. Modelling studies indicated that these derivatives bind to the CRD of Mincle in a manner similar to that of the prototypical Mincle agonist, trehalose dibehenate (TDB), with NFAT-GFP reporter cell assays confirming that all compounds, apart from derivatives with short alkyl chains, led to robust Mincle signalling. It was also observed that a carbonyl moiety was needed for good Mincle-mediated signalling. The ability of the compounds to induce mIL-1 β and mIL-6 production by bone marrow-derived macrophages (BMDMs) further demonstrated the agonist activity of the compounds, with the presence of a carbonyl moiety and longer lipid chains augmenting cytokine production. Notably, a C20 inverted ester led to levels of mIL-1β that were significantly greater than those induced by TDB. The same C20 inverted ester also led to a significant increase in hIL-1β and hIL-6 by human monocytes, and exhibited no toxicity, as demonstrated using BMDMs in an in vitro Sytox Green assay. The ability of the inverted ester to enhance antigen-mediated immune responses was then determined. In these studies, the inverted ester was found to augment the OVA-specific Th1/Th7 immune response in vitro, and exhibit adjuvanticity that was better than that of TDB in vivo, as evidenced by a significant increase in IgG antibodies for the inverted ester but not TDB when using OVA as a model antigen.

Water-soluble trehalose glycolipids show superior Mincle binding and signaling but impaired phagocytosis and IL-1β production

The tremendous potential of trehalose glycolipids as vaccine adjuvants has incentivized the study of how the structures of these ligands relate to their Mincle-mediated agonist activities. Despite this, structure-activity work in the field has been largely empirical, and less is known about how Mincle-independent pathways might be affected by different trehalose glycolipids, and whether Mincle binding by itself can serve as a proxy for adjuvanticity. There is also much demand for more water-soluble Mincle ligands. To address this need, we prepared polyethylene glycol modified trehalose glycolipids (PEG-TGLs) with enhanced water solubility and strong murine Mincle (mMincle) binding and signaling. However, only modest cytokine and chemokine responses were observed upon the treatment of GM-CSF treated bone-marrow cells with the PEG-TGLs. Notability, no IL-1β was observed. Using RNA-Seq analysis and a representative PEG-TGL, we determined that the more water-soluble adducts were less able to activate phagocytic pathways, and hence, failed to induce IL-1β production. Taken together, our data suggests that in addition to strong Mincle binding, which is a pre-requisite for Mincle-mediated cellular responses, the physical presentation of trehalose glycolipids in colloidal form is required for inflammasome activation, and hence, a strong inflammatory immune response.

Recombinant BCG-LTAK63 Vaccine Candidate for Tuberculosis Induces an Inflammatory Profile in Human Macrophages

Tuberculosis (TB) is one of the top 10 leading causes of death worldwide. The recombinant BCG strain expressing the genetically detoxified A subunit of the thermolabile toxin from Escherichia coli (LTAK63) adjuvant (rBCG-LTAK63) has previously been shown to confer superior protection and immunogenicity compared to BCG in a murine TB infection model. To further investigate the immunological mechanisms induced by rBCG-LTAK63, we evaluated the immune responses induced by rBCG-LTAK63, BCG, and Mycobacterium tuberculosis (Mtb) H37Rv strains in experimental infections of primary human M1 and M2 macrophages at the transcriptomic and cytokine secretion levels. The rBCG-LTAK63-infected M1 macrophages more profoundly upregulated interferon-inducible genes such as IFIT3, OAS3, and antimicrobial gene CXCL9 compared to BCG, and induced higher levels of inflammatory cytokines such as IL-12(p70), TNF-β, and IL-15. The rBCG-LTAK63-infected M2 macrophages more extensively upregulated transcripts of inflammation-related genes, TAP1, GBP1, SLAMF7, TNIP1, and IL6, and induced higher levels of cytokines related to inflammation and tissue repair, MCP-3 and EGF, as compared to BCG. Thus, our data revealed an important signature of immune responses induced in human macrophages by rBCG-LTAK63 associated with increased inflammation, activation, and tissue repair, which may be correlated with a protective immune response against TB.

Therapeutic Effect of Subunit Vaccine AEC/BC02 on Mycobacterium tuberculosis Post-Chemotherapy Relapse Using a Latent Infection Murine Model

Tuberculosis (TB), caused by the human pathogen Mycobacterium tuberculosis (Mtb), is an infectious disease that presents a major threat to human health. Bacillus Calmette-Guérin (BCG), the only licensed TB vaccine, is ineffective against latent TB infection, necessitating the development of further TB drugs or therapeutic vaccines. Herein, we evaluated the therapeutic effect of a novel subunit vaccine AEC/BC02 after chemotherapy in a spontaneous Mtb relapse model. Immunotherapy followed 4 weeks of treatment with isoniazid and rifapentine, and bacterial loads in organs, pathological changes, and adaptive immune characteristics were investigated. The results showed slowly increased bacterial loads in the spleen and lungs of mice inoculated with AEC/BC02 with significantly lower loads than those of the control groups. Pathological scores for the liver, spleen, and lungs decreased accordingly. Moreover, AEC/BC02 induced antigen-specific IFN-γ-secreting or IL-2-secreting cellular immune responses, which decreased with the number of immunizations and times. Obvious Ag85b- and EC-specific IgG were observed in mice following the treatment with AEC/BC02, indicating a significant Th1-biased response. Taken together, these data suggest that AEC/BC02 immunotherapy post-chemotherapy may shorten future TB treatment.

Mycobacterium bovis Wild-Type BCG or Recombinant BCG Secreting Murine IL-18 (rBCG/IL-18) Strains in Driving Immune Responses in Immunocompetent or Immunosuppressed Mice

Mycobacterium tuberculosis infections remain a global health problem in immunosuppressed patients. The effectiveness of BCG (Bacillus Calmette−Guérin), an anti-tuberculosis vaccine, is unsatisfactory. Finding a new vaccine candidate is a priority. We compared numerous immune markers in BCG-susceptible C57BL/6 and BCG-resistant C3H mice who had been injected with 0.9% NaCl (control) or with wild-type BCG or recombinant BCG secreting interleukin (IL)-18 (rBCG/IL-18) and in immunized mice who were immunocompromised with cyclophosphamide (CTX). The inoculation of rBCG/IL-18 in immunocompetent mice increased the percentage of bone marrow myeloblasts and promyelocytes, which were further elevated in the rBCG/IL-18/CTX-treated mice: C57BL/6 mice—3.0% and 11.4% (control) vs. 18.6% and 42.4%, respectively; C3H mice—1.1% and 7.7% (control) vs. 18.4% and 44.9%, respectively, p < 0.05. The bone marrow cells showed an increased mean fluorescence index (MFI) in the CD34 adhesion molecules: C57BL/6 mice—4.0 × 103 (control) vs. 6.2 × 103; C3H mice—4.0 × 103 (control) vs. 8.0 × 103, p < 0.05. Even in the CTX-treated mice, the rBCG/IL-18 mobilized macrophages for phagocytosis, C57BL/6 mice—4% (control) vs. 8%; C3H mice—2% (control) vs. 6%, and in immunocompetent mice, C57BL/6 induced the spleen homing of effector memory CD4+ and CD8+ T cells (TEM), 15% (control) vs. 28% and 8% (control) vs. 22%, respectively, p < 0.05. In conclusion, rBCG/IL-18 effectively induced selected immune determinants that were maintained even in immunocompromised mice.

Immunogenic profiling of Mycobacterium tuberculosis DosR protein Rv0569 reveals its ability to switch on Th1 based immunity

Mycobacterium tuberculosis (M.tb) is a multifaceted bacterial pathogen known to infect more than 2 billion people globally. However, a majority of the individuals (>90%) show no overt clinical symptoms of active Tuberculosis (TB) and, it is reported that M.tb in these individuals resides in the latent form. Therefore, huge burden of latently infected population poses serious threat to human health. Inconsistent efficacy of BCG vaccine and poor understanding of latency-associated determinants contribute to the failure of combating M.tb. The discovery of DosR as the master regulator of dormancy, opened new avenues to understand the pathophysiology of the bacterium. Though the specific functions of various DosR genes are yet to be discovered, they have been reported as potent T-cell activators and could elicit strong protective immune responses. Rv0569 is a DosR-encoded conserved hypothetical protein overexpressed during dormancy. However, it is not clearly understood how this protein modulates the host immune response. In the present study, we have demonstrated that Rv0569 has a high antigenic index and induces enhanced secretion of Th1 cytokines IL-12p40 and TNF-α as compared to Th2 cytokine IL-10 in macrophages. Mechanistically, Rv0569 induced the transcription of these pro-inflammatory signatures through the activation of NF-κB pathway. Further, immunization of mice with DosR protein Rv0569 switched the immune response towards Th1-biased cytokine pattern, characterized by the enhanced production of IFN-γ, IL-12p40, and TNF-α. Rv0569 augmented the expansion of antigen-specific IFN-γ and IL-2 producing effector CD4⁺ and CD8⁺ T-cells which are hallmarks of Th1 biased protective immunity. Additionally, IgG2a/IgG1 and IgG2b/IgG1 ratio in the serum of immunized mice further confirmed the ability of Rv0569 to skew Th1 biased immune response. In conclusion, we emphasize that Rv0569 has the ability to generate signals to switch on Th1-dominated responses and further suggest that it could be a potential vaccine candidate against latent M.tb infection.

Amide-linked brartemicin glycolipids exhibit Mincle-mediated agonist activity in vitro

Lipidated derivatives of the natural product brartemicin show much promise as vaccine adjuvants due to their ability to signal through the Macrophage Inducible C-type Lectin (Mincle). We synthesised three lipophilic amide-linked brartemicin derivatives and compared their agonist activity to that of their ester-linked counterparts in vitro. We demonstrate that the brartemicin amide derivatives activate bone-marrow-derived macrophages (BMDMs) in a Mincle-dependent manner, as evidenced by the production of the pro-inflammatory cytokine IL-1β in wildtype but not Mincle^-/- cells. The amide derivatives showed activity that was as good as, if not better than, their ester counterparts. Two of the amide derivatives, but none of the ester-derivatives, also led to the production of IL-1β by human-derived monocytes. As the production of IL-1β is a good indicator of vaccine adjuvanticity potential, these findings suggest that amide-linked brartemicin derivatives show particular promise as vaccine adjuvants.

COVID-19 and Beyond: Exploring Public Health Benefits from Non-Specific Effects of BCG Vaccination

Bacille Calmette–Guérin (BCG) vaccination, widely used throughout the world to protect against infant tuberculous meningitis and miliary tuberculosis (TB), can provide broad non-specific protection against infectious respiratory diseases in certain groups. Interest in BCG has seen a resurgence within the scientific community as the mechanisms for non-specific protection have begun to be elucidated. The impact of the COVID-19 pandemic on nearly every aspect of society has profoundly illustrated the pressure that respiratory infections can place on a national healthcare system, further renewing interest in BCG vaccination as a public health policy to reduce the burden of those illnesses. However, the United States does not recommend BCG vaccination due to its variable effectiveness against adult TB, the relatively low risk of Mycobacterium tuberculosis infection in most of the United States, and the vaccine’s interference with tuberculin skin test reactivity that complicates TB screening. In this review, we explore the broad immune training effects of BCG vaccination and literature on the effects of BCG vaccination on COVID-19 spread, disease severity, and mortality. We further discuss barriers to scheduled BCG vaccination in the United States and how those barriers could potentially be overcome.

Antigen-Specific Tissue-Resident Memory T Cells in the Respiratory System Were Generated following Intranasal Vaccination of Mice with BCG

Tissue-resident memory T cells (T_RM) are different from effector memory T cells (T_EM) and central memory T cells (T_CM) and contribute to the protective immunity against local challenges. Currently, we found that CD4⁺ and CD8⁺ T_RM cells in the nasal mucosa, trachea, lungs, and lavage fluids were heterogeneous on the expression of CD69 and CD103 as well as the production of cytokines including IFN-γ, IL-2, and TNF-α. After intranasal vaccination of mice with BCG, respiratory tissues expressed higher levels of the chemokine CXCL16 and T_RM cells expressed CXCR6 to CXCL16. In addition, antigen-specific CD4⁺ and CD8⁺ T_RM cells expressed cytokines following the stimulation with BCG and persisted in the nasal mucosa, trachea, and lungs for more than a hundred days. At the same time, mice were infected intranasally with live BCG and the results showed that vaccinated mice cleared up live BCG faster than nonvaccinated mice in the respiratory system. Taken together, our data demonstrated that intranasal vaccination of mice with BCG could induce antigen-specific CD4⁺ and CD8⁺ T_RM cells in the respiratory system and have the ability to provide protection against pulmonary reinfection.

MiR-21 Is Remotely Governed by the Commensal Bacteria and Impairs Anti-TB Immunity by Down-Regulating IFN-γ

Tuberculosis (TB), which is a frequent and important infectious disease caused by Mycobacterium tuberculosis, has resulted in an extremely high burden of morbidity and mortality. The importance of intestinal dysbacteriosis in regulating host immunity has been implicated in TB, and accumulating evidence suggests that microRNAs (miRNAs) might act as a key mediator in maintaining intestinal homeostasis through signaling networks. However, the involvement of miRNA in gut microbiota, TB and the host immune system remains unknown. Here we showed that intestinal dysbacteriosis increases the susceptibility to TB and remotely increased the expression of miR-21 in lung. Systemic antagonism of miR-21 enhanced IFN-γ production and further conferred immune protection against TB. Molecular experiments further indicated that miR-21a-3p could specifically target IFN-γ mRNA. These findings revealed regulatory pathways implicating intestinal dysbacteriosis induced-susceptibility to TB: intestinal dysbiosis→lung miRNA→targeting IFN-γ→impaired anti-TB immunity. This study also suggested that deregulated miRNAs by commensal bacteria could become promising targets as TB therapeutics.

BCG immunomodulation: From the 'hygiene hypothesis' to COVID-19

The century-old tuberculosis vaccine BCG has been the focus of renewed interest due to its well-documented ability to protect against various non-TB pathogens. Much of these broad spectrum protective effects are attributed to trained immunity, the epigenetic and metabolic reprogramming of innate immune cells. As BCG vaccine is safe, cheap, widely available, amendable to use as a recombinant vector, and immunogenic, it has immense potential for use as an immunotherapeutic agent for various conditions including autoimmune, allergic, neurodegenerative, and neoplastic diseases as well as a preventive measure against infectious agents. Of particular interest is the use of BCG vaccination to counteract the increasing prevalence of autoimmune and allergic conditions in industrialized countries attributable to reduced infectious burden as described by the ‘hygiene hypothesis.’ Furthermore, BCG vaccination has been proposed as a potential therapy to mitigate spread and disease burden of COVID-19 as a bridge to development of a specific vaccine and recombinant BCG expression vectors may prove useful for the introduction of SARS-CoV-2 antigens (rBCG-SARS-CoV-2) to induce long-term immunity. Understanding the immunomodulatory effects of BCG vaccine in these disease contexts is therefore critical. To that end, we review here BCG-induced immunomodulation focusing specifically on BCG-induced trained immunity and how it relates to the ‘hygiene hypothesis’ and COVID-19.

Recent progress in the design of DNA vaccines against tuberculosis

Current tuberculosis (TB) vaccines have some disadvantages and many efforts have been undertaken to produce effective TB vaccines. As a result of their advantages, DNA vaccines are promising future vaccine candidates. This review focuses on the design and delivery of novel DNA-based vaccines against TB.

Analysis of Putative Epitope Candidates of Mycobacterium tuberculosis Against Pakistani Human Leukocyte Antigen Background: An Immunoinformatic Study for the Development of Future Vaccine

Tuberculosis (TB), a chronic disease caused by Mycobacterium tuberculosis (Mtb), is a global health issue across the world. Pakistan ranks fifth among the countries, which are facing, a significantly great number of mortalities and morbidities due to TB. Unfortunately, all previously reported treatments are not successful for the eradication of TB. Here in this study, we report an emerging treatment option for this disease. We have applied immunoinformatics to predict highly conserved B and T-cell epitopes from Mtb, showing significant binding affinities to the frequent HLA alleles in the Pakistani population. A total of ten highly referenced and experimentally validated epitopes were selected from the Immune Epitope Database (IEDB), followed by their conservancy analysis using weblogos. The consensus sequences and variants derived from these sequences were examined, for their binding affinities, with prevalent HLA alleles of Pakistan. Moreover, the antigenic and allergenic natures of these peptides were also evaluated via Vaxijen and AllerTOP, respectively. Consequently, all potentially allergenic and non-antigenic, peptide fragments, were excluded from the analysis. Among all putative epitopes, three CD8 + T-cell epitopes were selected, as ideal vaccine candidates and, population coverage analysis revealed that the combination of these three peptides was covering, 67.28% Pakistani Asian and 57.15% mixed Pakistani populations. Likewise, eleven linear and six conformational or discontinuous B-cell epitopes were also marked as potential vaccine candidates based on their prediction score, non-allergenic nature, and antigenic properties. These epitopes, however, need the final validation via wet-lab studies. After their approval, these epitopes would be effective candidates for the future designing of epitope-based vaccines against Mtb infections in Pakistan.

Heterologous Boosting With Listeria-Based Recombinant Strains in BCG-Primed Mice Improved Protection Against Pulmonary Mycobacterial Infection

While Baccillus Calmette-Guerin (BCG) is used worldwide, tuberculosis (TB) is still a global concern due to the poor efficacy of BCG. Novel vaccine candidates are therefore urgently required. In this study, two attenuated recombinant Listeria strains, LMΔ-msv and LIΔ-msv were constructed by deletion of actA and plcB and expression of a fusion protein consisting of T cell epitopes from four Mycobacterium tuberculosis (Mtb) antigens (Rv2460c, Rv2660c, Rv3875, and Rv3804c). The safety and immunogenicity of the two recombinant strains were evaluated in C57BL/6J mice. After intravenous immunization individually, both recombinant strains entered liver and spleen but eventually were eliminated from these organs after several days. Simultaneously, they induced antigen-specific cell-mediated immunity, indicating that the recombinant Listeria strains were immunogenic and safe in vivo. LMΔ-msv immunization induced stronger cellular immune responses than LIΔ-msv immunization, and when boosted with LIΔ-msv, antigen-specific IFN-γ CD8⁺ T cell responses were notably magnified. Furthermore, we evaluated the protection conferred by the vaccine candidates against mycobacterial infection via challenging the mice with 1 × 10⁷ CFU of BCG. Especially, we tested the feasibility of application of them as heterologous BCG supplement vaccine by immunization of mice with BCG firstly, and boosted with LMΔ-msv and LIΔ-msv sequentially before challenging. Combination immune strategy (LMΔ-msv prime-LIΔ-msv boost) conferred comparable protection efficacy as BCG alone. More importantly, BCG-vaccinated mice acquired stronger resistance to Mycobacterial challenge when boosted with LMΔ-msv and LIΔ-msv sequentially. Our results inferred that heterologous immunization with Listeria-based recombinant strains boosted BCG-primed protection against pulmonary mycobacterial infection.

A new DNA vaccine expressing HspX-PPE44-EsxV fusion antigens of Mycobacterium tuberculosis induced strong immune responses

OBJECTIVES

Infection with tuberculosis (TB) is regarded as a major health issue. Due to the emergence of antibiotic resistance during TB treatment, prevention via vaccination is one of the most effective ways of controlling the infection. DNA vaccines are developed at a greater pace due to their ability in generating a long-lasting immune response, higher safety compared to the live vaccines, and relatively lower cost of production. In the present study, we evaluated a new DNA vaccine encoding the fusion HspX-PPE44-EsxV antigens, separately, and in combination with Bacillus Calmette-Guérin (BCG) administration, in a prime-boost method in mice.

MATERIALS AND METHODS

A novel DNA vaccine encoding HspX-PPE44-EsxV fusion antigen of Mycobacterium tuberculosis was constructed, and RT-PCR and Western blot analysis were performed to verify the expression of the antigen. Female BALB/c mice were divided into five groups (PBS, BCG, pcDNA3.1 (+) vector, pDNA/HspX-PPE44-EsxV vaccine, and the BCG-prime boost groups). In order to evaluate the immunogenicity of the recombinant vector, BALB/c mice were injected with 100 μg of pDNA at 2-week intervals. Then, cytokine assay was conducted using eBioscience ELISA kits (Ebioscience, AUT) according to manufacturers' instructions to evaluate the concentrations of IL-4, IL-12, TGF-β, and IFN-γ.

RESULTS

The concentrations of INF-γ, IL-12, and TGF-beta were significantly increased compared to the control groups (P<0.001). INF-γ and IL-12 production were increased significantly in pDNA/HspX-PPE44-EsxV+BCG group compared to pDNA/HspX-PPE44-EsxV group (P<0.001).

CONCLUSION

This study showed that the present DNA vaccine could induce a high level of specific cytokines in mice. It was also shown that using this DNA vaccine in a BCG prime-boost protocol can produce significant amounts of IFN-γ, IL-12, and TGF-β.

Proposing BCG Vaccination for Mycobacterium avium ss. paratuberculosis (MAP) Associated Autoimmune Diseases

Bacille Calmette-Guerin (BCG) vaccination is widely practiced around the world to protect against the mycobacterial infection tuberculosis. BCG is also effective against the pathogenic mycobacteria that cause leprosy and Buruli's ulcer. BCG is part of the standard of care for bladder cancer where, when given as an intravesicular irrigant, BCG acts as an immunomodulating agent and lessens the risk of recurrence. Mycobacterium avium ss. paratuberculosis (MAP) causes a fatal enteritis of ruminant animals and is the putative cause of Crohn's disease of humans. MAP has been associated with an increasingly long list of inflammatory/autoimmune diseases: Crohn's, sarcoidosis, Blau syndrome, Hashimoto's thyroiditis, autoimmune diabetes (T1D), multiple sclerosis (MS), rheumatoid arthritis, lupus and Parkinson's disease. Epidemiologic evidence points to BCG providing a "heterologous" protective effect on assorted autoimmune diseases; studies using BCG vaccination for T1D and MS have shown benefit in these diseases. This article proposes that the positive response to BCG in T1D and MS is due to a mitigating action of BCG upon MAP. Other autoimmune diseases, having a concomitant genetic risk for mycobacterial infection as well as cross-reacting antibodies against mycobacterial heat shock protein 65 (HSP65), could reasonably be considered to respond to BCG vaccination. The rare autoimmune disease, relapsing polychondritis, is one such disease and is offered as an example. Recent studies suggesting a protective role for BCG in Alzheimer's disease are also explored. BCG-induced energy shift from oxidative phosphorylation to aerobic glycolysis provides the immunomodulating boost to the immune response and also mitigates mycobacterial infection-this cellular mechanism unifies the impact of BCG on the disparate diseases of this article.

Recombinant BCG expressing the LTAK63 adjuvant induces increased early and long-term immune responses against Mycobacteria

The development of more effective vaccines against Mycobacterium tuberculosis has become a world priority. Previously, we have shown that a recombinant BCG expressing the LTAK63 adjuvant (rBCG-LTAK63) displayed higher protection than BCG against tuberculosis challenge in mice. In order to elucidate the immune effector mechanisms induced by rBCG-LTAK63, we evaluated the immune response before and after challenge. The potential to induce an innate immune response was investigated by intraperitoneal immunization with BCG or rBCG-LTAK63: both displayed increased cellular infiltration in the peritoneum with high numbers of neutrophils at 24 h and macrophages at 7 d. The rBCG-LTAK63-immunized mice displayed increased production of Nitric Oxide at 24 h and Hydrogen Peroxide at 7 d. The number of lymphocytes was higher in the rBCG-LTAK63 group when compared to BCG. Immunophenotyping of lymphocytes showed that rBCG-LTAK63 immunization increased CD4⁺ and CD8⁺ T cells. An increased long-term Th1/Th17 cytokine profile was observed 90 d after subcutaneous immunization with rBCG-LTAK63. The evaluation of immune responses at 15 d after challenge showed that rBCG-LTAK63-immunized mice displayed increased TNF-α-secreting CD4⁺ T cells and multifunctional IL-2⁺ TNF-α⁺ CD4⁺ T cells as compared to BCG-immunized mice. Our results suggest that immunization with rBCG-LTAK63 induces enhanced innate and long-term immune responses as compared to BCG. These results can be correlated with the superior protection induced against TB.

Evaluation of the immunogenicity and efficacy of BCG and MTBVAC vaccines using a natural transmission model of tuberculosis

Effective vaccines against tuberculosis (TB) are needed in order to prevent TB transmission in human and animal populations. Evaluation of TB vaccines may be facilitated by using reliable animal models that mimic host pathophysiology and natural transmission of the disease as closely as possible. In this study, we evaluated the immunogenicity and efficacy of two attenuated vaccines, BCG and MTBVAC, after each was given to 17 goats (2 months old) and then exposed for 9 months to goats infected with M. caprae. In general, MTBVAC-vaccinated goats showed higher interferon-gamma release than BCG vaccinated goats in response to bovine protein purified derivative and ESAT-6/CFP-10 antigens and the response was significantly higher than that observed in the control group until challenge. All animals showed lesions consistent with TB at the end of the study. Goats that received either vaccine showed significantly lower scores for pulmonary lymph nodes and total lesions than unvaccinated controls. Both MTBVAC and BCG vaccines proved to be immunogenic and effective in reducing severity of TB pathology caused by M. caprae. Our model system of natural TB transmission may be useful for evaluating and optimizing vaccines.

Mucosal Vaccination with a Self-Adjuvanted Lipopeptide Is Immunogenic and Protective against Mycobacterium tuberculosis

Tuberculosis (TB) remains a staggering burden on global public health. Novel preventative tools are desperately needed to reach the targets of the WHO post-2015 End-TB Strategy. Peptide or protein-based subunit vaccines offer potential as safe and effective generators of protection, and enhancement of local pulmonary immunity may be achieved by mucosal delivery. We describe the synthesis of a novel subunit vaccine via native chemical ligation. Two immunogenic epitopes, ESAT6_1-20 and TB10.4_3-11 from Mycobacterium tuberculosis (Mtb), were covalently conjugated to the TLR2-ligand Pam₂Cys to generate a self-adjuvanting lipopeptide vaccine. When administered mucosally to mice, the vaccine enhanced pulmonary immunogenicity, inducing strong Th17 responses in the lungs and multifunctional peripheral T-lymphocytes. Mucosal, but not peripheral vaccination, provided substantial protection against Mtb infection, emphasizing the importance of delivery route for optimal efficacy.

Ag85b/ESAT6-CFP10 adjuvanted with aluminum/poly-IC effectively protects guinea pigs from latent mycobacterium tuberculosis infection

The high global burden of tuberculosis (TB) underscores the urgent need for an effective TB vaccine since the only licensed Bacillus Calmette-Guérin (BCG) vaccine is ineffective in preventing adult pulmonary TB and affords no protection against latent TB infection (LTBI). Herein we investigated the potential of Mycobacterium tuberculosis (Mtb) antigen proteins AEC comprised of Ag85b and ESAT6-CFP10 proteins in conjunction with aluminum (Al) and polyriboinosinic-polyribocytidylic acid (poly-IC) as a novel subunit vaccine against TB. The immunogenicity and protection induced by the adjuvanted vaccine were evaluated in two animal models. Mice vaccinated with AEC/Al/poly-IC exhibited significant antigen-specific humoral immune responses and cell-mediated immunity as determined by immunoassay and multicolor flow cytometric assay, and the protective effect of the vaccine was demonstrated in a guinea pig model of latent Mtb infection. Compared to the control group, the mean pathological scores and bacterial loads in lungs and spleens of AEC/Al/poly-IC-immunized guinea pigs were significantly reduced. These data indicate that the AEC/Al/poly-IC is highly immunogenic in mice and can effectively protect guinea pigs against latent Mtb infection; it may represent a promising candidate vaccine for the control of latent TB.

Cloning, Expression, and Refolding of PPE17 Protein of Mycobacterium Tuberculosis as a Promising Vaccine Candidate

BACKGROUND

Tuberculosis as a global health problem requires special attention in the contexts of prevention and control. Subunit vaccines are promising strategies to protect burdens of tuberculosis via increasing the BCG protection. The present study aimed to design a vaccine study by means of high-throughput expression and correct refolding of recombinant protein PPE17.

METHODS

We aimed to clone, express, and refold PPE17 protein of Mycobacterium tuberculosis in bacterial systems as a promising vaccine candidate. The PPE17 (Rv1168c) gene was PCR amplified and inserted into pET-21b(+) vector, cloned in E. coli TOP10, and finally expressed in E. coli BL21(DE3).

RESULTS

The expressed recombinant protein was entirely found in insoluble form (inclusion bodies). The insoluble protein was denatured in 6M guanidine-HCl and refolded by descending denaturant concentration dialysis. Moreover, the recombinant protein was purified by Ni-NTA column chromatography. The changing temperature had no effects on solubilizing protein and the maximum expression was achieved at 0.5 mM concentration of isopropyl-D-thiogalactopyranoside (IPTG) induction.

CONCLUSION

Bacterial expression system is a timesaving tool and refolding by descending denaturant concentration dialysis is a rapid and reliable method.

Intranasal immunization with Mycobacterium tuberculosis Rv3615c induces sustained adaptive CD4+ T-cell and antibody responses in the respiratory tract

Sustained adaptive immunity to pathogens provides effective protection against infections, and effector cells located at the site of infection ensure rapid response to the challenge. Both are essential for the success of vaccine development. To explore new vaccination approach against Mycobacterium tuberculosis (M.tb) infection, we have shown that Rv3615c, identified as ESX-1 substrate protein C of M.tb but not expressed in BCG, induced a dominant Th1-type response of CD4⁺ T cells from patients with tuberculosis pleurisy, which suggests a potential candidate for vaccine development. But subcutaneous immunization with Rv3615c induced modest T-cell responses systemically, and showed suboptimal protection against virulent M.tb challenge at the site of infection. Here, we use a mouse model to demonstrate that intranasal immunization with Rv3615c induces sustained capability of adaptive CD4⁺ T- and B-cell responses in lung parenchyma and airway. Rv3615c contains a dominant epitope of mouse CD4⁺ T cells, Rv3615c_41-50 , and elicits CD4⁺ T-cell response with an effector-memory phenotype and multi-Th1-type cytokine coexpressions. Since T cells resident at mucosal tissue are potent at control of infection at early stage, our data show that intranasal immunization with Rv3615c promotes a sustained regional immunity to M.tb, and suggests a potency in control of M.tb infection. Our study warranties a further investigation of Rv3615c as a candidate for development of effective vaccination against M.tb infection.

Classification and reporting of severity experienced by animals used in scientific procedures: FELASA/ECLAM/ESLAV Working Group report

Directive 2010/63/EU introduced requirements for the classification of the severity of procedures to be applied during the project authorisation process to use animals in scientific procedures and also to report actual severity experienced by each animal used in such procedures. These requirements offer opportunities during the design, conduct and reporting of procedures to consider the adverse effects of procedures and how these can be reduced to minimize the welfare consequences for the animals. Better recording and reporting of adverse effects should also help in highlighting priorities for refinement of future similar procedures and benchmarking good practice. Reporting of actual severity should help inform the public of the relative severity of different areas of scientific research and, over time, may show trends regarding refinement. Consistency of assignment of severity categories across Member States is a key requirement, particularly if re-use is considered, or the safeguard clause is to be invoked. The examples of severity classification given in Annex VIII are limited in number, and have little descriptive power to aid assignment. Additionally, the examples given often relate to the procedure and do not attempt to assess the outcome, such as adverse effects that may occur. The aim of this report is to deliver guidance on the assignment of severity, both prospectively and at the end of a procedure. A number of animal models, in current use, have been used to illustrate the severity assessment process from inception of the project, through monitoring during the course of the procedure to the final assessment of actual severity at the end of the procedure (Appendix 1).

Evolution and Strain Variation in BCG

BCG vaccines were derived by in vitro passage, during the years 1908-1921, at the Pasteur Institute of Lille. Following the distribution of stocks of BCG to vaccine production laboratories around the world, it was only a few decades before different BCG producers recognized that there were variants of BCG, likely due to different passaging conditions in the different laboratories. This ultimately led to the lyophilization of stable BCG products in the 1950s and 1960s, but not before considerable evolution of the different BCG strains had taken place. The application of contemporary research methodologies has now revealed genomic, transcriptomic and proteomic differences between BCG strains. These molecular differences in part account for phenotypic differences in vitro between BCG strains, such as their variable secretion of antigenic proteins. Yet, the relevance of BCG variability for immunization policy remains elusive. In this chapter we present an overview of what is known about BCG evolution and its resulting strain variability, and provide some speculation as to the potential relevance for a vaccine given to over 100 million newborns each year.

CLONING AND EXPRESSION OF MCE1A GENE FROM MYCOBACTERIUM TUBERCULOSIS BEIJING AND H37RV STRAIN FOR VACCINE CANDIDATE DEVELOPMENT

BACKGROUND

Tuberculosis remains the leading cause of death in the world, especially wherever poverty, malnutrition and poor housing prevail. Mycobacterium tuberculosis Beijing strain is the most common strain that causes tuberculosis in Indonesia. The wide spread of tuberculosis has been further aggravated by HIV-AIDS and drug resistance. Unfortunately, Bacille Calmette-Guerin (BCG) as the current vaccine has different protection function and efficacy. According to function analysis, mce1A gene was predicted to have a role in host invasion and survival of Mycobacterium tuberculosis in human macrophages.

MATERIALS AND METHODS

We performed cloning and protein expression of Mce1A gene of Mycobacterium tuberculosis Beijing strain as local isolate and standard strain H37Rv as a comparison on the expression system Escherichia coli BL21(DE3). Mce1A gene from the strains were amplified by PCR and inserted into the vector pET28a. Each resulting recombinant plasmid was subsequently transformed into E. coli BL21(DE3) and Mce1A protein was expressed with IPTG induction.

RESULTS

E. coli BL21(DE3) was succesfully transformed with a recombinant plasmid that contains the Mce1A gene insert with correct orientation and reading frame. There was no mutation found in the amino acids sequence for B and T cell epitope. Mce1A expression in E. coli BL21(DE3) showed a protein band that was higher than expected. The protein was confirmed with Western blotting using anti-His detector.

CONCLUSION

We assumed that Mce1A recombinant protein that has been expressed in E. coli BL21(DE3) is in their dimeric form or alternatively formed aggregates of different sizes.

Evaluation of Aggregated Ag85B Antigen for Its Biophysical Properties, Immunogenicity, and Vaccination Potential in a Murine Model of Tuberculosis Infection

Protein aggregates have been reported to act as a reservoir that can release biologically active, native form of precursor protein. Keeping this fact into consideration, it is tempting to exploit protein aggregate-based antigen delivery system as a functional vaccine to expand desirable immunological response in the host. Herein, we explored the capacity of aggregated Ag85B of Mycobacterium tuberculosis (Mtb) to act as a prophylactic vaccine system that releases the precursor antigen in slow and sustained manner. Being particulate system with exposed hydrophobic residues, aggregated Ag85B is likely to be avidly taken up by both phagocytosis as well as fusion with plasma membrane of antigen presenting cells, leading to its direct delivery to their cytosol. Its unique ability to access cytosol of target cells is further evident from the fact that immunization with aggregated Ag85B led to the induction of Th1-dominant immune response along with upregulated expression of qualitatively superior polyfunctional T cells in the mice. Antibodies generated following immunization with aggregated antigen recognized both native and monomeric Ag85B released from protein aggregate. The implicated immunization strategy offers protection at par to that of established BCG vaccine with desirable central and effector memory responses against subsequent Mtb aerosol challenge. The study highlights the potential of aggregated Ag85B as promising antigen delivery system and paves the way to design better prophylactic regimes against various intracellular pathogens including Mtb.

Flow cytometry: An efficient method for antigenicity measurement and particle characterization on an adjuvanted vaccine candidate H4-IC31 for tuberculosis

We have developed an accurate, precise and stability-indicating flow cytometry (FC) based assay to directly measure antigenicity of H4 protein (also known as HyVac4) in a vaccine formulation of H4-IC31, without desorbing the H4 protein from the IC31 adjuvant. This method involves immuno-staining of H4-IC31 complex with anti-H4 monoclonal antibodies (mAbs) followed by FC analysis. The assay is not only able to consistently measure H4 antigenicity levels in H4-IC31 stored under normal condition at 2-8°C, but also able to detect changes in H4 antigenicity after H4-IC31 undergoes heat stress or freeze-thawing. In addition, the FC method is able to characterize particle morphology while measuring antigenicity. The biological relevance of the changes in H4 antigenicity detected by the FC assay was supported by an in vitro cell based functional assay using human PBMCs to measure IFN-gamma (IFN-γ) secretion upon re-stimulation with H4-IC31. Our results show that the FC based antigenicity assay can efficiently monitor the biological and physicochemical properties of H4-IC31 and is an indicator for adjuvanted vaccine product stability.

Host transcriptional responses following ex vivo re-challenge with Mycobacterium tuberculosis vary with disease status

The identification of immune correlates that are predictive of disease outcome for tuberculosis remains an ongoing challenge. To address this issue, we evaluated gene expression profiles from peripheral blood mononuclear cells following ex vivo challenge with Mycobacterium tuberculosis, among participants with active TB disease (ATBD, n = 10), latent TB infection (LTBI, n = 10), and previous active TB disease (after successful treatment; PTBD, n = 10), relative to controls (n = 10). Differential gene expression profiles were assessed by suppression-subtractive hybridization, dot blot, real-time polymerase chain reaction, and the comparative cycle threshold methods. Comparing ATBD to control samples, greater fold-increases of gene expression were observed for a number of chemotactic factors (CXCL1, CXCL3, IL8, MCP1, MIP1α). ATBD was also associated with higher IL1B gene expression, relative to controls. Among LTBI samples, gene expression of several chemotactic factors (CXCL2, CXCL3, IL8) was similarly elevated, compared to individuals with PTBD. Our results demonstrated that samples from participants with ATBD and LTBI have distinct gene expression profiles in response to ex vivo M. tuberculosis infection. These findings indicate the value in further characterizing the peripheral responses to M. tuberculosis challenge as a route to defining immune correlates of disease status or outcome.

Vaccine research and development: tuberculosis as a global health threat

One of the aims of the World Health Organisation (WHO) Millennium Development Goals (MDG) is to reduce the number of cases of tuberculosis (TB) infection by the year 2015. However, 9 million new cases were reported in 2013, with an estimated 480,000 new cases of multi-drug resistant tuberculosis (MDR-TB) globally. Bacille Calmette-Guérin (BCG) is the most available and currently used candidate vaccine against tuberculosis; it prevents childhood TB, but its effectiveness against pulmonary TB in adults and adolescents is disputed. To achieve the goal of the WHO MDG, the need for a new improved vaccine is of primary importance. This review highlights several articles that have reported vaccine development. There are about 16 TB vaccines in different phases of clinical trials at the time of writing, which include recombinant peptide/protein, live-attenuated and recombinant live-attenuated, protein/adjuvant, viral-vectored, and immunotherapeutic vaccine. Further studies in reverse vaccinology and massive campaigns on vaccination are needed in order to achieve the target for TB eradication by 2050.

BCG - old workhorse, new skills

Bacille Calmette-Guérin (BCG), the only tuberculosis (TB) vaccine in clinical practice, has limitations in efficacy, immunogenicity and safety. Much current TB vaccine research focuses on engineering live mycobacteria to interfere with phagosome biology and host intracellular pathways including apoptosis and autophagy, with candidates such as BCG Δzmp1, BCG ΔureC::hly, BCG::ESX-1^Mmar, Mtb ΔphoP ΔfadD26, Mtb ΔRD1 ΔpanCD and M. smegmatis Δesx-3::esx-3(Mtb) in the development pipeline. Correlates of protection in preclinical studies include increased central memory CD4⁺ T cells and recruitment of antigen-specific T cells to the lungs, with mucosal vaccination found to be superior to parenteral vaccination. Finally, recent studies suggest beneficial non-specific effects of BCG on immunity, which should be taken into account when considering these vaccines for BCG replacement.

Tuberculosis-a World Health Organization Perspective

Tuberculosis (TB) is an important cause of morbidity and mortality worldwide. The World Health Organization (WHO) has implemented and scaled-up three important global public health strategies (i.e., DOTS, Stop TB, and End TB) to improve the international scenario. Their epidemiological impact was relevant, as they decreased the number of potential new cases of disease and death. However, the emergence and spread of TB/HIV coinfection and multidrug-resistant TB have hindered the progress towards the elimination of TB by 2050. More efforts are required to increase the global annual decline of the TB incidence rate. Political commitment is necessary, with global and national strategies oriented to the adoption and adaptation of the international, evidence-based recommendations on diagnosis, treatment, and prevention. Research and development activities should be planned to improve the current tools adopted to fight the disease. New rapid diagnostics, an updated and effective therapeutic armamentarium, and an effective preventive vaccine could represent the solution to address the current epidemiological threats.

Melioidosis: Clinical impact and public health threat in the tropics

This review briefly summarizes the geographical distribution and clinical impact of melioidosis, especially in the tropics. Burkholderia pseudomallei (a gram-negative bacterium) is the major causative agent for melioidosis, which is prevalent in Singapore, Malaysia, Thailand, Vietnam, and Northern Australia. Melioidosis patients are increasingly being recognized in other parts of the world. The bacteria are intrinsically resistant to many antimicrobial agents, but prolonged treatment, especially with combinations of antibiotics, may be effective. Despite therapy, the overall case fatality rate of septicemia in melioidosis remains significantly high. Intracellular survival of the bacteria within macrophages may progress to chronic infections, and about 10% of patients suffer relapses. In the coming decades, melioidosis will increasingly afflict travelers throughout many global regions. Clinicians managing travelers returning from the subtropics or tropics with severe pneumonia or septicemia should consider acute melioidosis as a differential diagnosis. Patients with open skin wounds, diabetes, or chronic renal disease are at higher risk for melioidosis and should avoid direct contact with soil and standing water in endemic regions. Furthermore, there are fears that B. pseudomallei may be used as a biological weapon. Technological advancements in molecular diagnostics and antibiotic therapy are improving the disease outcomes in endemic areas throughout Asia. Research and development efforts on vaccine candidates against melioidosis are ongoing.

BCG-loaded chitosan microparticles: interaction with macrophages and preliminary in vivo studies

The aim of this study was to develop a novel BCG-loaded chitosan vaccine with high association efficiency which can afford efficient interaction with APC and elicit local and Th1-type-specific immune response after intranasal administration. Chitosan-suspended BCG and BCG-loaded chitosan-alginate microparticles were prepared by ionotropic gelation. Interaction with APC was evaluated by fluorescence microscopy using rBCG-GFP. Specific immune responses were evaluated following intranasal immunisation of mice. Cellular uptake was approximately two-fold higher for chitosan-suspended BCG. A single dose of BCG-loaded microparticles or chitosan-suspended BCG by intranasal route improved Th1-type response compared with subcutaneous BCG. Chitosan-suspended BCG originated the highest mucosal response in the lungs by intranasal route. These positive results indicate that the proposed approach of whole live BCG microencapsulation in chitosan-alginate for intranasal immunisation was successful in allowing efficient interaction with APC, while improving the cellular immune response, which is of interest for local immunisation against tuberculosis.

Reasons for optimism in the search for new vaccines for tuberculosis

In the development of vaccines for tuberculosis (TB), the combination of the will, funding, scientific rigor, new tools, refined animal models and improved clinical trial designs are all converging at an opportune moment. The lack of optimism that has surrounded the likelihood for finding novel TB vaccines has resulted from a lack of correlates of vaccine-induced protection, a lack of tool candidate vaccines to probe the immunologic space, which may be needed, and the negative result of one recent trial. A vaccine for TB that can be delivered at a reasonable cost to the marketplace will have greater impact on the incidence of new cases of TB than any intervention in world history. Now is the time to increase resources, both financial and human intellectual capacity, for a global tuberculosis vaccine effort.

Immune Responses to Bacillus Calmette-Guérin Vaccination: Why Do They Fail to Protect against Mycobacterium tuberculosis?

Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis (TB), is the current leading cause of death due to a single infectious organism. Although curable, the broad emergence of multi-, extensive-, extreme-, and total-drug resistant strains of M.tb has hindered eradication efforts of this pathogen. Furthermore, computational models predict a quarter of the world’s population is infected with M.tb in a latent state, effectively serving as the largest reservoir for any human pathogen with the ability to cause significant morbidity and mortality. The World Health Organization has prioritized new strategies for improved vaccination programs; however, the lack of understanding of mycobacterial immunity has made it difficult to develop new successful vaccines. Currently, Mycobacterium bovis bacillus Calmette–Guérin (BCG) is the only vaccine approved for use to prevent TB. BCG is highly efficacious at preventing meningeal and miliary TB, but is at best 60% effective against the development of pulmonary TB in adults and wanes as we age. In this review, we provide a detailed summary on the innate immune response of macrophages, dendritic cells, and neutrophils in response to BCG vaccination. Additionally, we discuss adaptive immune responses generated by BCG vaccination, emphasizing their specific contributions to mycobacterial immunity. The success of future vaccines against TB will directly depend on our understanding of mycobacterial immunity.

Computational Identification and Characterization of a Promiscuous T-Cell Epitope on the Extracellular Protein 85B of Mycobacterium spp. for Peptide-Based Subunit Vaccine Design

Tuberculosis (TB) is a reemerging disease that remains as a leading cause of morbidity and mortality in humans. To identify and characterize a T-cell epitope suitable for vaccine design, we have utilized the Vaxign server to assess all antigenic proteins of Mycobacterium spp. recorded to date in the Protegen database. We found that the extracellular protein 85B displayed the most robust antigenicity among the proteins identified. Computational tools for identifying T-cell epitopes predicted an epitope, 181-QQFIYAGSLSALLDP-195, that could bind to at least 13 major histocompatibility complexes, revealing the promiscuous nature of the epitope. Molecular docking simulation demonstrated that the epitope could bind to the binding groove of MHC II and MHC I molecules by several hydrogen bonds. Molecular docking analysis further revealed that the epitope had a distinctive binding pattern to all DRB1 and A and B series of MHC molecules and presented almost no polymorphism in its binding site. Moreover, using "Allele Frequency Database," we checked the frequency of HLA alleles in the worldwide population and found a higher frequency of both class I and II HLA alleles in individuals living in TB-endemic regions. Our results indicate that the identified peptide might be a universal candidate to produce an efficient epitope-based vaccine for TB.

PPE38 Protein of Mycobacterium tuberculosis Inhibits Macrophage MHC Class I Expression and Dampens CD8+ T Cell Responses

Suppression of CD8⁺ T cell activation is a critical mechanism used by Mycobacterium tuberculosis (MTB) to escape protective host immune responses. PPE38 belongs to the unique PPE family of MTB and in our previous study, PPE38 protein was speculated to participate in manipulating macrophage MHC class I pathway. To test this hypothesis, the function of mycobacterial PPE38 protein was assessed here using macrophage and mouse infection models. Decreased amount of MHC class I was observed on the surface of macrophages infected with PPE38-expressing mycobacteria. The transcript of genes encoding MHC class I was also inhibited by PPE38. After infection of C57BL/6 mice with Mycobacterium smegmatis expressing PPE38 (Msmeg-PPE38), decreased number of CD8⁺ T cells was found in spleen, liver, and lungs through immunohistochemical analysis, comparing to the control strain harboring empty vector (Msmeg-V). Consistently, flow cytometry assay showed that fewer effector/memory CD8⁺ T cells (CD44^highCD62L^low) were activated in spleen from Msmeg-PPE38 infected mice. Moreover, Msmeg-PPE38 confers a growth advantage over Msmeg-V in C57BL/6 mice, indicating an effect of PPE38 to favor mycobacterial persistence in vivo. Overall, this study shows a unique biological function of PPE38 protein to facilitate mycobacteria to escape host immunity, and provides hints for TB vaccine development.

Recent advances in the production of recombinant subunit vaccines in Pichia pastoris

Recombinant protein subunit vaccines are formulated using defined protein antigens that can be produced in heterologous expression systems. The methylotrophic yeast Pichia pastoris has become an important host system for the production of recombinant subunit vaccines. Although many basic elements of P. pastoris expression system are now well developed, there is still room for further optimization of protein production. Codon bias, gene dosage, endoplasmic reticulum protein folding and culture condition are important considerations for improved production of recombinant vaccine antigens. Here we comment on current advances in the application of P. pastoris for the synthesis of recombinant subunit vaccines.

R&D in Vaccines Targeting Neglected Diseases: An Exploratory Case Study Considering Funding for Preventive Tuberculosis Vaccine Development from 2007 to 2014

Based on an exploratory case study regarding the types of institutions funding the research and development to obtain new tuberculosis vaccines, this article intends to provoke discussion regarding the provision of new vaccines targeting neglected disease. Although our findings and discussion are mainly relevant to the case presented here, some aspects are more generally applicable, especially regarding the dynamics of development in vaccines to prevent neglected diseases. Taking into account the dynamics of innovation currently seen at work in the vaccine sector, a highly concentrated market dominated by few multinational pharmaceutical companies, we feel that global PDP models can play an important role throughout the vaccine development cycle. In addition, the authors call attention to issues surrounding the coordination of actors and resources in the research, development, manufacturing, and distribution processes of vaccine products arising from PDP involvement.