Therapeutic vaccines for tuberculosis—A systematic review

Evaluation of the cross-immunity between Mycobacterium tuberculosis and Mycobacterium abscessus in vitro

Mycobacterium tuberculosis (M. tuberculosis) and Mycobacterium abscessus (M. abscessus) are important pathogens that can cause lung diseases. Given the abundance of shared antigens between these two pathogens, evaluating the cross-immunization between Mycobacterium tuberculosis and Mycobacterium abscessus has implications for the assessment of tuberculosis vaccines based on nontuberculous mycobacteria (NTM). The whole-cell proteins of Mycobacterium abscessus were lysed via ultrasonication and then were subcutaneously injected into BALB/c mice either alone or mixed with adjuvant for three times at a 10-day interval. After the final immunization, cross-immune antigens were analysed via genomic comparison and Mycobacterium tuberculosis proteome microarrays. BALB/c mice splenic lymphocytes were stimulated with TB-PPD to assess the cross-immunity of the cellular immune response. The effect of cross-immunity on the growth of Mycobacterium tuberculosis was evaluated using a Mycobacterium tuberculosis growth inhibition assay. Despite the presence of 1,953 homologous gene clusters between Mycobacterium tuberculosis and Mycobacterium abscessus, only 302 Mycobacterium tuberculosis antigens exhibited cross-immunoreactivity after three immunizations. Compared with the PBS group, TB-PPD stimulation significantly increased the secretion of TNF-α, IL-4, and IL-6 by sensitized mouse splenic lymphocytes, and significantly affected the proliferation of IL-2+CD4 T and TNF-α+CD4 T cells in the immunized group (P < 0.05), but had no impact on IFN-γ and IFN-γ+ CD4 T cells. Furthermore, there was no significant difference in the proliferation of Mycobacterium tuberculosis between the immunized group and the PBS group in spleen cells. These data indicate that proteins from Mycobacterium abscessus are highly immunogenic in mice. However, the cross-immune response between Mycobacterium abscessus and Mycobacterium tuberculosis was inadequate to effectively inhibit the proliferation of Mycobacterium tuberculosis.

Safety and efficacy of tuberculosis vaccine candidates in low- and middle-income countries: a systematic review of randomised controlled clinical trials

BACKGROUND

Tuberculosis (TB) remains a leading cause of death worldwide, with 98% of cases occurring in low- and middle-income countries (LMICs). The only vaccine licenced for the prevention of TB has limited protection for adolescents, adults and vulnerable populations. A safe and effective vaccine for all populations at risk is imperative to achieve global elimination of TB. We aimed to systematically review the efficacy and safety of TB vaccine candidates in late-phase clinical trials conducted in LMICs.

METHODS

Medline, Embase, CENTRAL, PubMed, Clinicaltrials.gov and Greylit.org were searched in June 2021 to identify phase 2 or later clinical randomised controlled trials that report the efficacy or safety (adverse events) of TB vaccine candidates with participants of any age living in an LMIC. TB vaccine candidates listed in the 2020 WHO Global TB Report were eligible for inclusion aside from BCG revaccination. Trials were excluded if all participants had active TB at baseline. Two reviewers independently assessed papers for eligibility, and for bias and quality using the Risk of Bias 2 tool and GRADE guidelines, respectively. We report efficacy rates and frequencies of adverse events from each included trial where available and qualitatively synthesise the findings.

RESULTS

Thirteen papers representing eleven trials met our inclusion criteria. Seven vaccine candidates were reviewed across seven countries: M72/AS01, RUTI, VPM1002, H56:IC31, MTBVAC, DAR-901 and ID93 + GLA-SE. Two trials reported on efficacy: an efficacy rate of 54% (95% CI 11.5, 76.2) was reported for M72/AS01 in adults with latent TB and 3% (95% CI -13.9, 17.7) for DAR-901 in healthy adolescents. However, the latter trial was underpowered. All vaccine candidates had comparable occurrences of adverse events between treatment arms and demonstrated acceptable safety profiles; though, RUTI resulted in one serious complication in a person living with HIV. M72/AS01 was the only vaccine considered safe across a diverse group of people including people living with HIV or latent TB and healthy infants and adolescents.

CONCLUSION

Further efficacy trials for M72/AS01 are warranted to include additional populations at risk where safety has been demonstrated. Further safety trials are needed for the remaining vaccine candidates to confirm safety in vulnerable populations.

A century of attempts to develop an effective tuberculosis vaccine: Why they failed?

Tuberculosis (TB) remains a major global health problem despite widespread use of the Bacillus BCG vaccine. This situation is worsened by co-infection with HIV, and the development of multidrug-resistant Mycobacterium tuberculosis (Mtb) strains. Thus, novel vaccine candidates and improved vaccination strategies are urgently needed in order to reduce the incidence of TB and even to eradicate TB by 2050. Over the last few decades, 23 novel TB vaccines have entered into clinical trials, more than 13 new vaccines have reached various stages of preclinical development, and more than 50 potential candidates are in the discovery stage as next-generation vaccines. Nevertheless, why has a century of attempts to introduce an effective TB vaccine failed? Who should be blamed -scientists, human response, or Mtb strategies? Literature review reveals that the elimination of latent or active Mtb infections in a given population seems to be an epigenetic process. With a better understanding of the connections between bacterial infections and gene expression conditions in epigenetic events, opportunities arise in designing protective vaccines or therapeutic agents, particularly as epigenetic processes can be reversed. Therefore, this review provides a brief overview of different approaches towards novel vaccination strategies and the mechanisms underlying these approaches.

The Research Progress in Immunotherapy of Tuberculosis

Tuberculosis (TB) is a serious public health problem worldwide. The combination of various anti-TB drugs is mainly used to treat TB in clinical practice. Despite the availability of effective antibiotics, effective treatment regimens still require long-term use of multiple drugs, leading to toxicity, low patient compliance, and the development of drug resistance. It has been confirmed that immune recognition, immune response, and immune regulation of Mycobacterium tuberculosis (Mtb) determine the occurrence, development, and outcome of diseases after Mtb infection. The research and development of TB-specific immunotherapy agents can effectively regulate the anti-TB immune response and provide a new approach toward the combined treatment of TB, thereby preventing and intervening in populations at high risk of TB infection. These immunotherapy agents will promote satisfactory progress in anti-TB treatment, achieving the goal of "ultra-short course chemotherapy." This review highlights the research progress in immunotherapy of TB, including immunoreactive substances, tuberculosis therapeutic vaccines, chemical agents, and cellular therapy.

Colliding and interacting microbiomes and microbial communities - consequences for human health

Living 'things' coexist with microorganisms, known as the microbiota/microbiome that provides essential physiological functions to its host. Despite this reliance, the microbiome is malleable and can be altered by several factors including birth-mode, age, antibiotics, nutrition, and disease. In this minireview, we consider how other microbiomes and microbial communities impact the host microbiome and the host through the concept of microbiome collisions (initial exposures) and interactions. Interactions include changes in host microbiome composition and functionality and/or host responses. Understanding the impact of other microbiomes and microbial communities on the microbiome and host are important considering the decline in human microbiota diversity in the developed world - paralleled by the surge of non-communicable, inflammatory-based diseases. Thus, surrounding ourselves with rich and diverse beneficial microbiomes and microbial communities to collide and interact with should help to diminish the loss in microbial diversity and protect from certain diseases. In the same vein, our microbiomes not only influence our health but potentially the health of those close to us. We also consider strategies for enhanced host microbiome collisions and interactions through the surrounding environment that ensure increased microbiome diversity and functionality contributing to enhanced symbiotic return to the host in terms of health benefit.

Vaccination Strategies Against Mycobacterium tuberculosis: BCG and Beyond

Tuberculosis (TB) is a highly contagious disease caused by Mycobacterium tuberculosis (Mtb) and is the major cause of morbidity and mortality across the globe. The clinical outcome of TB infection and susceptibility varies among individuals and even among different populations, contributed by host genetic factors such as polymorphism in the human leukocyte antigen (HLA) alleles as well as in cytokine genes, nutritional differences between populations, immunometabolism, and other environmental factors. Till now, BCG is the only vaccine available to prevent TB but the protection rendered by BCG against pulmonary TB is not uniform. To deliver a vaccine which can give consistent protection against TB is a great challenge with rising burden of drug-resistant TB. Thus, expectations are quite high with new generation vaccines that will improve the efficiency of BCG without showing any discordance for all forms of TB, effective for individual of all ages in all parts of the world. In order to enhance or improve the efficacy of BCG, different strategies are being implemented by considering the immunogenicity of various Mtb virulence factors as well as of the recombinant strains, co-administration with adjuvants and use of appropriate vehicle for delivery. This chapter discusses several such pre-clinical attempts to boost BCG with subunit vaccines tested in murine models and also highlights various recombinant TB vaccines undergoing clinical trials. Promising candidates include new generation of live recombinant BCG (rBCG) vaccines, VPM1002, which are deleted in one or two virulence genes. They encode for the mycobacteria-infected macrophage-inhibitor proteins of host macrophage apoptosis and autophagy, key events in killing and eradication of Mtb. These vaccines are rBCG- ΔureC::hly HM^R, and rBCG-ΔureC::hly ΔnuoG. The former vaccine has passed phase IIb in clinical trials involving South African infants and adults. Thus, with an aim of elimination of TB by 2050, all these cumulative efforts to develop a better TB vaccine possibly is new hope for positive outcomes.

Heme oxygenase-1 inhibition promotes IFNγ- and NOS2-mediated control of Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) infection induces pulmonary expression of the heme-degrading enzyme heme oxygenase-1 (HO-1). We have previously shown that pharmacological inhibition of HO-1 activity in experimental tuberculosis results in decreased bacterial loads and unexpectedly that this outcome depends on the presence of T lymphocytes. Here, we extend these findings by demonstrating that IFNγ production by T lymphocytes and NOS2 expression underlie this T-cell requirement and that HO-1 inhibition potentiates IFNγ-induced NOS2-dependent control of Mtb by macrophages in vitro. Among the products of heme degradation by HO-1 (biliverdin, carbon monoxide, and iron), only iron supplementation reverted the HO-1 inhibition-induced enhancement of bacterial control and this reversal was associated with decreased NOS2 expression and NO production. In addition, we found that HO-1 inhibition results in decreased labile iron levels in Mtb-infected macrophages in vitro and diminished iron accumulation in Mtb-infected lungs in vivo. Together these results suggest that the T-lymphocyte dependence of the therapeutic outcome of HO-1 inhibition on Mtb infection reflects the role of the enzyme in generating iron that suppresses T-cell-mediated IFNγ/NOS2-dependent bacterial control. In broader terms, our findings highlight the importance of the crosstalk between iron metabolism and adaptive immunity in determining the outcome of infection.

Koala retrovirus epidemiology, transmission mode, pathogenesis, and host immune response in koalas (Phascolarctos cinereus): a review

Koala retrovirus (KoRV) is a major threat to koala health and conservation. It also represents a series of challenges across the fields of virology, immunology, and epidemiology that are of great potential interest to any researcher in the field of retroviral diseases. KoRV is a gammaretrovirus that is present in both endogenous and exogenous forms in koala populations, with a still-active endogenization process. KoRV may induce immunosuppression and neoplastic conditions such as lymphoma and leukemia and play a role in chlamydiosis and other diseases in koalas. KoRV transmission modes, pathogenesis, and host immune response still remain unclear, and a clear understanding of these areas is critical for devising effective preventative and therapeutic strategies. Research on KoRV is clearly critical for koala conservation. In this review, we provide an overview of the current understanding and future challenges related to KoRV epidemiology, transmission mode, pathogenesis, and host immune response and discuss prospects for therapeutic and preventive vaccines.

Tuberculosis vaccine development: from classic to clinical candidates

Bacillus Calmette-Guérin (BCG) has been in use for nearly 100 years and is the only licensed TB vaccine. While BCG provides protection against disseminated TB in infants, its protection against adult pulmonary tuberculosis (PTB) is variable. To achieve the ambitious goal of eradicating TB worldwide by 2050, there is an urgent need to develop novel TB vaccines. Currently, there are more than a dozen novel TB vaccines including prophylactic and therapeutic at different stages of clinical research. This literature review provides an overview of the clinical status of candidate TB vaccines and discusses the challenges and future development trends of novel TB vaccine research in combination with the efficacy of evaluation of TB vaccines, provides insight for the development of safer and more efficient vaccines, and may inspire new ideas for the prevention of TB.

Effects of immunization with heat-killed Mycobacterium vaccae on autism spectrum disorder-like behavior and epileptogenesis in a rat model of comorbid autism and epilepsy

Autism spectrum disorders (ASDs) and epilepsy are often comorbid. The basis for this co-occurrence remains unknown; however, inflammatory stressors during development are a shared risk factor. To explore this association, we tested the effect of repeated immunizations using a heat-killed preparation of the stress-protective immunoregulatory microbe Mycobacterium vaccae NCTC 11,659 (M. vaccae) on the behavioral and epileptogenic consequences of the combined stress-terbutaline (ST) rat model of ASD-like behavior/epilepsy. Repeated immunization of the dam with M. vaccae during pregnancy, followed by immunization of the pups after terbutaline injections, prevented the expression of ASD-like behavior but did not appear to protect against, and may have even enhanced, the spontaneous epileptogenic effects of ST. Maternal M. vaccae injections transferred an anti-inflammatory immunophenotype to offspring, and repeated injections across development prevented ST-induced increases in microglial density at early developmental time points in a region-specific manner. Despite epidemiological comorbidity between ASD/epileptic conditions and shared environmental risk factors, our results suggest that the expression of ASD-like behaviors, but perhaps not epileptogenesis, is sensitive to early anti-inflammatory intervention. These data provide support for the exploration of immunoregulatory strategies to prevent the negative neurodevelopmental behavioral effects of stressors during early critical periods.

Modulation of immune responses using adjuvants to facilitate therapeutic vaccination

Therapeutic vaccination offers great promise as an intervention for a diversity of infectious and non-infectious conditions. Given that most chronic health conditions are thought to have an immune component, vaccination can at least in principle be proposed as a therapeutic strategy. Understanding the nature of protective immunity is of vital importance, and the progress made in recent years in defining the nature of pathological and protective immunity for a range of diseases has provided an impetus to devise strategies to promote such responses in a targeted manner. However, in many cases, limited progress has been made in clinical adoption of such approaches. This in part results from a lack of safe and effective vaccine adjuvants that can be used to promote protective immunity and/or reduce deleterious immune responses. Although somewhat simplistic, it is possible to divide therapeutic vaccine approaches into those targeting conditions where antibody responses can mediate protection and those where the principal focus is the promotion of effector and memory cellular immunity or the reduction of damaging cellular immune responses as in the case of autoimmune diseases. Clearly, in all cases of antigen-specific immunotherapy, the identification of protective antigens is a vital first step. There are many challenges to developing therapeutic vaccines beyond those associated with prophylactic diseases including the ongoing immune responses in patients, patient heterogeneity, and diversity in the type and stage of disease. If reproducible biomarkers can be defined, these could allow earlier diagnosis and intervention and likely increase therapeutic vaccine efficacy. Current immunomodulatory approaches related to adoptive cell transfers or passive antibody therapy are showing great promise, but these are outside the scope of this review which will focus on the potential for adjuvanted therapeutic active vaccination strategies.

Effects of Mycobacterium vaccae vaccine in a mouse model of tuberculosis: protective action and differentially expressed genes

BACKGROUND

Tuberculosis is a leading cause of death worldwide. BCG is an effective vaccine, but not widely used in many parts of the world due to a variety of issues. Mycobacterium vaccae (M. vaccae) is another vaccine used in human subjects to prevent tuberculosis. In the current study, we investigated the potential mechanisms of M. vaccae vaccination by determining differentially expressed genes in mice infected with M. tuberculosis before and after M. vaccae vaccination.

METHODS

Three days after exposure to M. tuberculosis H37Rv strain (5 × 10⁵ CFU), adult BALB/c mice randomly received either M. vaccae vaccine (22.5 μg) or vehicle via intramuscular injection (n = 8). Booster immunization was conducted 14 and 28 days after the primary immunization. Differentially expressed genes were identified by microarray followed by standard bioinformatics analysis.

RESULTS

M. vaccae vaccination provided protection against M. tuberculosis infection (most prominent in the lungs). We identified 2326 upregulated and 2221 downregulated genes in vaccinated mice. These changes could be mapped to a total of 123 signaling pathways (68 upregulated and 55 downregulated). Further analysis pinpointed to the MyD88-dependent TLR signaling pathway and PI3K-Akt signaling pathway as most likely to be functional.

CONCLUSIONS

M. vaccae vaccine provided good protection in mice against M. tuberculosis infection, via a highly complex set of molecular changes. Our findings may provide clue to guide development of more effective vaccine against tuberculosis.

Vaccination Against Tuberculosis: Revamping BCG by Molecular Genetics Guided by Immunology

Tuberculosis (TB) remains a major health threat. Although a vaccine has been available for almost 100 years termed Bacille Calmette-Guérin (BCG), it is insufficient and better vaccines are urgently needed. This treatise describes first the basic immunology and pathology of TB with an emphasis on the role of T lymphocytes. Better understanding of the immune response to Mycobacterium tuberculosis (Mtb) serves as blueprint for rational design of TB vaccines. Then, disease epidemiology and the benefits and failures of BCG vaccination will be presented. Next, types of novel vaccine candidates are being discussed. These include: (i) antigen/adjuvant subunit vaccines; (ii) viral vectored vaccines; and (III) whole cell mycobacterial vaccines which come as live recombinant vaccines or as dead whole cell or multi-component vaccines. Subsequently, the major endpoints of clinical trials as well as administration schemes are being described. Major endpoints for clinical trials are prevention of infection (PoI), prevention of disease (PoD), and prevention of recurrence (PoR). Vaccines can be administered either pre-exposure or post-exposure with Mtb. A central part of this treatise is the description of the viable BCG-based vaccine, VPM1002, currently undergoing phase III clinical trial assessment. Finally, new approaches which could facilitate design of refined next generation TB vaccines will be discussed.

Phase III, placebo-controlled, randomized, double-blind trial of tableted, therapeutic TB vaccine (V7) containing heat-killed M. vaccae administered daily for one month

Objective

Immunotherapy of tuberculosis (TB) to shorten treatment duration represents an unmet medical need. Orally delivered, tableted TB vaccine (V7) containing heat-killed Mycobacterium vaccae (NCTC 11659) has been demonstrated in prior clinical studies to be safe and fast-acting immune adjunct.

Methods

The outcome of Phase III trial of V7 containing 10 µg of hydrolyzed M. vaccae was evaluated in 152 patients randomized at 2:1 ratio: V7 (N = 100), placebo (N = 52). Both arms received conventional 1st or 2nd line TB drugs co-administered with daily pill of V7 or placebo.

Results

After one month mycobacterial clearance was observed in 68% (P < 0.0001) and 23.1% (P = 0.04) of patients on V7 and placebo. Stratified conversion rates in V7 recipients with drug-sensitive and multidrug-resistant TB were 86.7% and 55.6% vs 27.2% and 15% in placebo. Patients on V7 gained on average 2.4 kg (P < 0.0001) vs 0.3 kg (P = 0.18) in placebo. Improvements in hemoglobin levels, erythrocyte sedimentation rate and leukocyte counts were significantly better than in controls. Liver function tests revealed that V7 can prevent chemotherapy-induced hepatic damage.

Conclusion

Oral M. vaccae is safe, can overcome TB-associated weight loss and inflammation, reduce hepatotoxicity of TB drugs, improve sputum conversion three-fold OR 3.15; 95%CI (2.3,4.6), and cut treatment length by at least six-fold. Longer follow-up studies might be needed to further substantiate our findings (Clinicaltrials.gov: NCT01977768).

Tuberculosis Vaccine Development: Progress in Clinical Evaluation

Tuberculosis (TB) is the leading killer among all infectious diseases worldwide despite extensive use of the Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine. A safer and more effective vaccine than BCG is urgently required. More than a dozen TB vaccine candidates are under active evaluation in clinical trials aimed to prevent infection, disease, and recurrence. After decades of extensive research, renewed promise of an effective vaccine against this ancient airborne disease has recently emerged. In two innovative phase 2b vaccine clinical trials, one for the prevention of Mycobacterium tuberculosis infection in healthy adolescents and another for the prevention of TB disease in M. tuberculosis-infected adults, efficacy signals were observed. These breakthroughs, based on the greatly expanded knowledge of the M. tuberculosis infection spectrum, immunology of TB, and vaccine platforms, have reinvigorated the TB vaccine field. Here, we review our current understanding of natural immunity to TB, limitations in BCG immunity that are guiding vaccinologists to design novel TB vaccine candidates and concepts, and the desired attributes of a modern TB vaccine. We provide an overview of the progress of TB vaccine candidates in clinical evaluation, perspectives on the challenges faced by current vaccine concepts, and potential avenues to build on recent successes and accelerate the TB vaccine research-and-development trajectory.

Prospects for a vaccine to prevent HIV-related tuberculosis

PURPOSE OF REVIEW

To outline the need for a new tuberculosis (TB) vaccine; challenges for induction of vaccine-mediated protection in HIV-infected persons; and recent advances in clinical development.

RECENT FINDINGS

HIV has a detrimental effect on T-cell function, polarization and differentiation of Mycobacterium tuberculosis (Mtb)-specific T cells, Mtb antigen presentation by dendritic cells, and leads to B-cell and antibody-response deficiencies. Previous observations of protection against TB disease in HIV-infected persons by Mycobacterium obuense suggest that an effective vaccine against HIV-related TB is feasible. Studies of inactivated mycobacterial, viral-vectored and protein subunit vaccines reported lower immune responses in HIV-infected relative to HIV-uninfected individuals, which were only partially restored with antiretroviral therapy. Bacille Calmette Guerin (BCG) revaccination of HIV-uninfected adolescents recently showed moderate efficacy against sustained Mtb infection, but live mycobacterial vaccines have an unfavorable risk profile for HIV-infected persons. Ongoing trials of inactivated mycobacterial and protein-subunit vaccines in HIV-uninfected, Mtb-infected adults may be more relevant for protection of HIV-infected populations in TB endemic countries.

SUMMARY

New TB vaccine candidates have potential to protect against HIV-related TB, through vaccination prior to or after HIV acquisition, but this potential may only be realized after efficacy is demonstrated in HIV-uninfected populations, with or without Mtb infection.

RUTI Vaccination Enhances Inhibition of Mycobacterial Growth ex vivo and Induces a Shift of Monocyte Phenotype in Mice

Tuberculosis (TB) is a major global health problem and there is a dire need for an improved treatment. A strategy to combine vaccination with drug treatment, termed therapeutic vaccination, is expected to provide benefit in shortening treatment duration and augmenting treatment success rate. RUTI candidate vaccine has been specifically developed as a therapeutic vaccine for TB. The vaccine is shown to reduce bacillary load when administered after chemotherapy in murine and guinea pig models, and is also immunogenic when given to healthy adults and individuals with latent TB. In the absence of a validated correlate of vaccine-induced protection for TB vaccine testing, mycobacterial growth inhibition assay (MGIA) has been developed as a comprehensive tool to evaluate vaccine potency ex vivo. In this study, we investigated the potential of RUTI vaccine to control mycobacterial growth ex vivo and demonstrated the capacity of MGIA to aid the identification of essential immune mechanism. We found an association between the peak response of vaccine-induced growth inhibition and a shift in monocyte phenotype following RUTI vaccination in healthy mice. The vaccination significantly increased the frequency of non-classical Ly6C⁻ monocytes in the spleen after two doses of RUTI. Furthermore, mRNA expressions of Ly6C⁻-related transcripts (Nr4a1, Itgax, Pparg, Bcl2) were upregulated at the peak vaccine response. This is the first time the impact of RUTI has been assessed on monocyte phenotype. Given that non-classical Ly6C⁻ monocytes are considered to play an anti-inflammatory role, our findings in conjunction with previous studies have demonstrated that RUTI could induce a balanced immune response, promoting an effective cell-mediated response whilst at the same time limiting excessive inflammation. On the other hand, the impact of RUTI on non-classical monocytes could also reflect its impact on trained innate immunity which warrants further investigation. In summary, we have demonstrated a novel mechanism of action of the RUTI vaccine, which suggests the importance of a balanced M1/M2 monocyte function in controlling mycobacterial infection. The MGIA could be used as a screening tool for therapeutic TB vaccine candidates and may aid the development of therapeutic vaccination regimens for TB in the near future.

Historical BCG vaccination combined with drug treatment enhances inhibition of mycobacterial growth ex vivo in human peripheral blood cells

Tuberculosis (TB) is a leading infectious cause of death globally. Drug treatment and vaccination, in particular with Bacillus Calmette-Guérin (BCG), remain the main strategies to control TB. With the emergence of drug resistance, it has been proposed that a combination of TB vaccination with pharmacological treatment may provide a greater therapeutic value. We implemented an ex vivo mycobacterial growth inhibition assay (MGIA) to discriminate vaccine responses in historically BCG-vaccinated human volunteers and to assess the contribution of vaccine-mediated immune response towards the killing effect of mycobacteria in the presence of the antibiotics isoniazid (INH) and rifampicin (RIF), in an attempt to develop the assay as a screening tool for therapeutic TB vaccines. BCG vaccination significantly enhanced the ability of INH to control mycobacterial growth ex vivo. The BCG-vaccinated group displayed a higher production of IFN-γ and IP-10 when peripheral blood mononuclear cells (PBMC) were co-cultured with INH, with a similar trend during co-culture with RIF. A higher frequency of IFN-γ+ and TNF-α+ CD3- CD4- CD8- cells was observed, suggesting the contribution of Natural Killer (NK) cells in the combined effect between BCG vaccination and INH. Taken together, our data indicate the efficacy of INH can be augmented following historical BCG vaccination, which support findings from previous observational and animal studies.

How Far Are we Away From an Improved Vaccine For Tuberculosis? Current Efforts and Future Prospects

Tuberculosis still is a major public health problem worldwide, and vaccines may play a major role in its eradication. However, despite 20 years of intensive research, we still do not have a better vaccine than the Bacille Calmette-Guérin vaccine, which has been used since 1921 but exhibits only limited efficacy in the field. This effort has not, however, been entirely in vain as our understanding of TB vaccinology has been substantially expanded and there are currently 17 vaccine candidates in clinical development and several more in preclinical trials. This manuscript reviews the most important recent advances, concerns raised and future prospects in the TB vaccinology field.

Mycobacterium vaccae immunization protects aged rats from surgery-elicited neuroinflammation and cognitive dysfunction

Aging is a major risk factor for developing postoperative cognitive dysfunction. Neuroinflammatory processes, which can play a causal role in the etiology of postoperative cognitive dysfunction, are potentiated or primed as a function of aging. Here we explored whether exposure to a microorganism with immunoregulatory and anti-inflammatory properties, Mycobacterium vaccae NCTC 11659 (M. vaccae), could ameliorate age-associated neuroinflammatory priming. Aged (24 months) and adult (3 months) male F344XBN rats were immunized with heat-killed M. vaccae (3 injections, once per week) before undergoing a laparotomy or anesthesia control procedure. Aged, but not young rats, showed postoperative learning/memory deficits in a fear-conditioning paradigm. Importantly, M. vaccae immunization protected aged rats from these surgery-induced cognitive impairments. M. vaccae immunization also shifted the aged proinflammatory hippocampal microenvironment toward an anti-inflammatory phenotype. Furthermore, M. vaccae immunization reduced age-related hyperinflammatory responses in isolated hippocampal microglia. Overall, our novel data suggest that M. vaccae can induce an anti-inflammatory milieu in the aged brain and thus mitigate the neuroinflammatory and cognitive impairments induced by surgery.

Induction of neutralizing antibody response against koala retrovirus (KoRV) and reduction in viral load in koalas following vaccination with recombinant KoRV envelope protein

Koala retrovirus (KoRV) infects the majority of Australia’s koalas (Phascolarctos cinereus) and has been linked to several life-threatening diseases such as lymphoma and leukemia, as well as Chlamydia and thus poses a threat to the continued survival of this species. While quarantine and antiretroviral drug treatment are possible control measures, they are impractical, leaving vaccination as the only realistic option. In this study, we examined the effect of a recombinant envelope protein-based anti-KoRV vaccine in two groups of South Australian koalas: KoRV infected or KoRV free. We report a successful vaccination response in the koalas with no vaccine-associated side effects. The vaccine induced a significant humoral immune response as well as the production of neutralizing antibodies in both groups of koalas. We also identified B-cell epitopes that were differentially recognized in KoRV-infected versus KoRV-free koalas following vaccination. Importantly, we also showed that vaccination had a therapeutic effect on koalas infected exogenously with KoRV by reducing their circulating viral load. Together, this study highlights the possibility of successfully developing a vaccine against KoRV infection in koalas.

A vaccine candidate for Koala retrovirus elicits a protective antibody response and reduces the viral load in already-infected koalas. Koala retrovirus (KoRV), first identified in the last 20 years, is a life-threatening, endemic pathogen affecting Australian koalas. In pursuit of an effective KoRV vaccine, the University of the Sunshine Coast’s Peter Timms led a group of Australian scientists to develop a candidate based on the transmembrane section of the virus’ envelope protein. The six koalas vaccinated in the study all generated a strong antibody response to the envelope protein, and a strong neutralizing antibody response was reported during in vitro tests. Vaccinated koalas with pre-existing KoRV infection benefited from an average 79% reduction in viral load when measured 12 weeks after vaccination. Further research should be prioritized to provide much-needed protection to Australia’s koalas.

Efficacy of Mycobacterium vaccae immunotherapy for patients with tuberculosis: A systematic review and meta-analysis

Tuberculosis (TB) is a significant cause of illness and death worldwide. Immunotherapy has been investigated in the treatment of TB. The purpose of this study was to perform a meta-analysis investigating the effectiveness of the M. vaccae vaccine. Medline, Cochrane, EMBASE, and Google Scholar were searched until November 5, 2015 using the keywords: tuberculosis, pulmonary TB, therapeutic vaccines, immunotherapy, M. vaccae, sputum smear. Randomized controlled trials (RCTs) or 2-arm prospective studies were included. The primary outcome was the sputum smear clearance rate at 1 or 2 months and 6 months after treatment. Secondary outcomes were improvement of chest X-ray findings, sputum culture negative rate at 1 or 2 months and 6 months, erythrocyte sedimentation rate (ESR), hemoglobin, and leukocyte count, weight gain, and mortality. Of 89 records identified, 13 RCTs were included in the meta-analysis. The number of patients ranged from 22 to 1337, and the mean age ranged from 26.4 to 44.3 y. Patients treated with M. vaccae were more likely to have negative sputum smear results at 1-2 months (pooled OR = 2.642, 95% CI: 1.623-4.301, P < .001) and at 6 months (pooled OR = 2.111, 95% CI: 1.141-3.908, P = .017), and have a negative sputum culture at 1 or 2 months (pooled OR = 2.660, 95% CI: 1.978-3.578, P < .001). The results of this meta-analysis suggest that M. vaccae immunotherapy may be effective in the treatment of pulmonary TB.

Safety and Immunogenicity of the Recombinant Mycobacterium bovis BCG Vaccine VPM1002 in HIV-Unexposed Newborn Infants in South Africa

Tuberculosis is a global threat to which infants are especially vulnerable. Effective vaccines are required to protect infants from this devastating disease. VPM1002, a novel recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine previously shown to be safe and immunogenic in adults, was evaluated for safety in its intended target population, namely, newborn infants in a region with high prevalence of tuberculosis. A total of 48 newborns were vaccinated intradermally with VPM1002 (n = 36) or BCG Danish strain (n = 12) in a phase II open-labeled, randomized trial with a 6-month follow-up period. Clinical and laboratory measures of safety were evaluated during this time. In addition, vaccine-induced immune responses to mycobacteria were analyzed in whole-blood stimulation and proliferation assays. The safety parameters and immunogenicity were comparable in the two groups. Both vaccines induced interleukin-17 (IL-17) responses; however, VPM1002 vaccination led to an increase of CD8+ IL-17+ T cells at the week 16 and month 6 time points. The incidence of abscess formation was lower for VPM1002 than for BCG. We conclude that VPM1002 is a safe, well-tolerated, and immunogenic vaccine in newborn infants, confirming results from previous trials in adults. These results strongly support further evaluation of the safety and efficacy of this vaccination in larger studies. (This study has been registered at ClinicalTrials.gov under registration no. NCT01479972.).

Listening to each other: Infectious disease and cancer immunology

The immune system provides defense against tumors and pathogens. Here, we propose that by elucidating the shared principles of immunity that underlie cancer and infectious disease, oncologists and microbiologists can learn from each other and achieve the deeper mechanistic understanding critical the development of therapeutic approaches.

Novel vaccination approaches to prevent tuberculosis in children

Pediatric tuberculosis (TB) is an underappreciated problem and accounts for 10 % of all TB deaths worldwide. Children are highly susceptible to infection with Mycobacterium tuberculosis and interrupting TB spread would require the development of effective strategies to control TB transmission in pediatric populations. The current vaccine for TB, M. bovis Bacille Calmette-Guérin (BCG), can afford some level of protection against TB meningitis and severe forms of disseminated TB in children; however, its efficacy against pulmonary TB is variable and the vaccine does not afford life-long protective immunity. For these reasons there is considerable interest in the development of new vaccines to control TB in children. Multiple vaccine strategies are being assessed and include recombinant forms of the existing BCG vaccine, protein or viral candidates designed to boost BCG-induced immunity, or live attenuated forms of M. tuberculosis. A number of these candidates have entered clinical trials; however, no vaccine has shown improved protective efficacy compared to BCG in humans. The current challenge is to identify the most suitable candidates to progress from early to late stage clinical trials, in order to deliver a vaccine that can control and hopefully eliminate the global threat of TB.

Individualizing management of extensively drug-resistant tuberculosis: diagnostics, treatment, and biomarkers

INTRODUCTION

Success rates for treatment of extensively drug resistant tuberculosis (XDR-TB) are low due to limited treatment options, delayed diagnosis and inadequate health care infrastructure. Areas covered: This review analyses existing programmes of prevention, diagnosis and treatment of XDR-TB. Improved diagnostic procedures and rapid molecular tests help to select appropriate drugs and dosages. Drugs dosages can be further tailored to the specific conditions of the patient based on quantitative susceptibility testing of the M. tuberculosis isolate and use of therapeutic drug monitoring. Pharmacovigilance is important for preserving activity of the novel drugs bedaquiline and delamanid. Furthermore, biomarkers of treatment response must be developed and validated to guide therapeutic decisions. Expert commentary: Given the currently poor treatment outcomes and the association of XDR-TB with HIV in endemic regions, a more patient oriented approach regarding diagnostics, drug selection and tailoring and treatment evaluation will improve treatment outcome. The different areas of expertise should be covered by a multidisciplinary team and may involve the transition of patients from hospitalized to home or community-based treatment.

The Progress of Therapeutic Vaccination with Regard to Tuberculosis

A major problem with tuberculosis (TB) control is the long duration of drug therapy-both for latent and for active TB. Therapeutic vaccination has been postulated to improve this situation, and to this end there are several candidates already in clinical phases of development. These candidates follow two main designs, namely bacilli-directed therapy based on inactivated -whole or -fragmented bacillus (Mycobacterium w and RUTI) or fusion proteins that integrate non-replicating bacilli -related antigens (H56 vaccine), and host-directed therapy to reduce the tissue destruction. The administration of inactivated Mycobacterium vaccae prevents the "Koch phenomenon" response, and oral administration of heat-killed Mycobacterium manresensis prevents excessive neutrophilic infiltration of the lesions. This review also tries to explain the success of Mycobacterium tuberculosis by reviewing its evolution from infection to disease, and highlights the lack of a definitive understanding of the natural history of TB pathology and the need to improve our knowledge on TB immunology and pathogenesis.

Vaccination sequence effects on immunological response and tissue bacterial burden in paratuberculosis infection in a rabbit model

Paratuberculosis (PTB), a chronic granulomatous enteritis produced by Mycobacterium avium subspecies paratuberculosis (MAP), is considered as one of the diseases with the highest economic impact in the ruminant industry. Vaccination against MAP is recommended during the first months after birth on the basis that protection would be conferred before the first contact with mycobacteria. However, little is known about the therapeutic effect of MAP vaccination in controlled experimental conditions. The current study was designed to evaluate the efficacy of vaccination before and after challenge with MAP in a rabbit infection model. The rabbits were divided into four groups: non-infected control (NIC, n = 4), infected control challenged with MAP (IC, n = 5), vaccinated and challenged 1 month after with MAP (VSI, n = 5) and challenged with MAP and vaccinated 2 months later (IVS, n = 5). The results from this study show a quick increase in IFN-γ release upon stimulation with bovine, avian and johnin PPD in animals vaccinated before MAP challenge. All vaccinated animals show an increased humoral response as seen by western blot and ELISA. The final bacteriology index (considering tissue culture and qPCR) shows that the IC group was the most affected. Vaccination after infection (IVS) produced the lowest bacteriology index showing significant differences with the IC group (p = 0.034). In conclusion, vaccination against MAP shows positive effects in a rabbit model. However, vaccination after infection shows a slightly stronger protective effect compared to vaccination before infection, suggesting a therapeutic effect. This feature could be applied to previously infected adult animals under field conditions.

Current status of new tuberculosis vaccine in children

Pediatric tuberculosis contributes significantly to the burden of TB disease worldwide. In order to achieve the goal of eliminating TB by 2050, an effective TB vaccine is urgently needed to prevent TB transmission in children. BCG vaccination can protect children from the severe types of TB such as TB meningitis and miliary TB, while its efficacy against pediatric pulmonary TB ranged from no protection to very high protection. In recent decades, multiple new vaccine candidates have been developed, and shown encouraging safety and immunogenicity in the preclinical experiments. However, the limited data on protective efficacy in infants evaluated by clinical trials has been disappointing, an example being MVA85A. To date, no vaccine has been shown to be clinically safer and more effective than the presently licensed BCG vaccine. Hence, before a new vaccine is developed with more promising efficacy, we must reconsider how to better use the current BCG vaccine to maximize its effectiveness in children.

Mycobacterium tuberculosis infection and vaccine development

Following HIV/AIDS, tuberculosis (TB) continues to be the second most deadly infectious disease in humans. The global TB prevalence has become worse in recent years due to the emergence of multi-drug resistant (MDR) and extensively-drug resistant (XDR) strains, as well as co-infection with HIV. Although Bacillus Calmette-Guérin (BCG) vaccine has nearly been used for a century in many countries, it does not protect adult pulmonary tuberculosis and even causes disseminated BCG disease in HIV-positive population. It is impossible to use BCG to eliminate the Mycobacterium tuberculosis (M. tb) infection or to prevent TB onset and reactivation. Consequently, novel vaccines are urgently needed for TB prevention and immunotherapy. In this review, we discuss the TB prevalence, interaction between M. tb and host immune system, as well as recent progress of TB vaccine research and development.

A review of clinical models for the evaluation of human TB vaccines

While much progress has been made in the fight against the scourge of tuberculosis (TB), we are still some way from reaching the ambitious targets of eliminating it as a global public health problem by the mid twenty-first century. A new and effective vaccine that protects against pulmonary TB disease will be an essential element of any control strategy. Over a dozen vaccines are currently in development, but recent efficacy trial data from one of the most advanced candidates have been disappointing. Limitations of current preclinical animal models exist, together with a lack of a complete understanding of host immunity to TB or robust correlates of disease risk and protection. Therefore, in the context of such obstacles, we discuss the lessons identified from recent efficacy trials, current concepts of biomarkers and correlates of protection, the potential of innovative clinical models such as human challenge and conducting trials in high-incidence settings to evaluate TB vaccines in humans, and the use of systems vaccinology and novel technologies including transcriptomics and metabolomics, that may facilitate their utility.

Oral Administration of Heat-Killed Mycobacterium manresensis Delays Progression toward Active Tuberculosis in C3HeB/FeJ Mice

Low-dose tolerance using heat-killed mycobacteria has been tested as a means of stopping progression toward active tuberculosis (TB) lesions in a human-like murine model using C3HeB/FeJ mice. In the present study, we studied the effect of different treatment schedules with heat-killed non-tuberculous-mycobacteria (NTM) species when given orally, based on the hypothesis of generating oral tolerance. This study included M. manresensis, a new species belonging to the fortuitum group, present in drinking water. Oral treatment with M. manresensis for 2 weeks was able to induce a PPD-specific Tregs population, which has been related to a decrease in the neutrophilic infiltration found in TB lesions. Further mechanistic analysis using PPD-stimulated splenocytes links this 2-week treatment with heat-killed M. manresensis to IL-10 production and memory PPD-specific Tregs, and also to a weak PPD-specific global immune response stimulation, increasing IL-6, TNF, and IFN-γ production. In lungs, this treatment decreased the bacillary load, granulomatous infiltration and pro-inflammatory cytokines (TNF, IFN-γ, IL-6, and IL-17). Oral administration of M. manresensis during standard treatment for TB also significantly reduced the relapse of active TB after ending the treatment. Overall the data suggest that the use of heat-killed M. manresensis could be a new and promising tool for avoiding active TB induction and as adjunctive to TB treatment. This supports the usefulness of generating a new kind of protection based on a complex balanced immune response focused on both destroying the bacilli and including control of an excessive inflammatory response.

Molecular analysis of clinical isolates previously diagnosed as Mycobacterium intracellulare reveals incidental findings of "Mycobacterium indicus pranii" genotypes in human lung infection

Background

Mycobacterium intracellulare is a major cause of Mycobacterium avium complex lung disease in many countries. Molecular studies have revealed several new Mycobacteria species that are closely related to M. intracellulare. The aim of this study was to re-identify and characterize clinical isolates from patients previously diagnosed with M. intracellulare lung disease at the molecular level.

Methods

Mycobacterial isolates from 77 patients, initially diagnosed with M. intracellulare lung disease were re-analyzed by multi-locus sequencing and pattern of insertion sequences.

Results

Among the 77 isolates, 74 (96 %) isolates were designated as M. intracellulare based on multigene sequence-based analysis. Interestingly, the three remaining strains (4 %) were re-identified as “Mycobacterium indicus pranii” according to distinct molecular phylogenetic positions in rpoB and hsp65 sequence-based typing. In hsp65 sequevar analysis, code 13 was found in the majority of cases and three unreported codes were identified. In 16S–23S rRNA internal transcribed spacer (ITS) sequevar analysis, all isolates of both species were classified within the Min-A ITS sequevar. Interestingly, four of the M. intracellulare isolates harbored IS1311, a M. avium-specific element. Two of three patients infected with “M. indicus pranii” had persistent positive sputum cultures after antibiotic therapy, indicating the clinical relevance of this study.

Conclusions

This analysis highlights the importance of precise identification of clinical isolates genetically close to Mycobacterium species, and suggests that greater attention should be paid to nontuberculous mycobacteria lung disease caused by “M. indicus pranii”.

Evaluation of the immunogenicity and diagnostic interference caused by M. tuberculosis SO2 vaccination against tuberculosis in goats

The immunogenicity and diagnostic interference caused by M. tuberculosis SO2, a prototype vaccine first time tested in goats was evaluated. Tuberculosis-free goats were distributed in four groups: [1], non-vaccinated; [2], subcutaneously (SC) BCG vaccinated; [3], intranasally (IN) SO2 vaccinated and [4], SC SO2 vaccinated. Intradermal tuberculin and IFN-γ tests using PPDs and alternative antigenic cocktails containing mainly ESAT-6 and CFP-10 (E/C) were applied at different times post-vaccination. Results showed a significant (p<0.05) increase in the number of reactors detected using both PPD-based intradermal and IFN-γ tests at different times in all the vaccinated groups. No intradermal reactivity was detected in the vaccinated goats using a cocktail containing E/C, Rv3615c and Rv3020c. A higher overall reactivity was observed in the group [4] in comparison with the other vaccinated groups. Results showed that antigens used to differentiate BCG vaccinated animals could be potentially used to differentiate SO2 vaccinated ones.

Prospects in Mycobacterium bovis Bacille Calmette et Guérin (BCG) vaccine diversity and delivery: why does BCG fail to protect against tuberculosis?

Mycobacterium tuberculosis (M.tb) infection leads to active tuberculosis (TB), a disease that kills one human every 18s. Current therapies available to combat TB include chemotherapy and the preventative vaccine Mycobacterium bovis Bacille Calmette et Guérin (BCG). Increased reporting of drug resistant M.tb strains worldwide indicates that drug development cannot be the primary mechanism for eradication. BCG vaccination has been used globally for protection against childhood and disseminated TB, however, its efficacy at protecting against pulmonary TB in adult and aging populations is highly variable. In this regard, the immune response generated by BCG vaccination is incapable of sterilizing the lung post M.tb infection as indicated by the large proportion of individuals with latent TB infection that have received BCG. Although many new TB vaccine candidates have entered the development pipeline, only a few have moved to human clinical trials; where they showed no efficacy and/or were withdrawn due to safety regulations. These trials highlight our limited understanding of protective immunity against the development of active TB. Here, we discuss current vaccination strategies and their impact on the generation and sustainability of protective immunity against TB.

Recent advances in the development of vaccines for tuberculosis

Tuberculosis (Tb) continues to be a dreadful infection worldwide with nearly 1.5 million deaths in 2013. Furthermore multi/extensively drug-resistant Tb (MDR/XDR-Tb) worsens the condition. Recently approved anti-Tb drugs (bedaquiline and delamanid) have the potential to induce arrhythmia and are recommended in patients with MDR-Tb when other alternatives fail. The goal of elimination of Tb by 2050 will not be achieved without an effective new vaccine. The recent advancement in the development of Tb vaccines is the keen focus of this review. To date, Bacille Calmette Guerin (BCG) is the only licensed Tb vaccine in use, however its efficacy in pulmonary Tb is variable in adolescents and adults. There are nearly 15 vaccine candidates in various phases of clinical trials, includes five protein or adjuvant vaccines, four viral-vectored vaccines, three mycobacterial whole cell or extract vaccines, and one each of the recombinant live and the attenuated Mycobacterium tuberculosis (Mtb) vaccine.

Mycobacterium tuberculosis virulence: insights and impact on vaccine development

The existing TB vaccine, the attenuated Mycobacterium bovis strain BCG, is effective in protecting infants from severe forms of the disease, while its efficacy in protecting adults from pulmonary TB is poor. In the last two decades, a renewed interest in TB resulted in the development of several candidate vaccines that are now entering clinical trials. However, most of these vaccines are based on a common rationale and aim to induce a strong T-cell response against Mycobacterium tuberculosis. Recent advancements in the understanding of M. tuberculosis virulence determinants and associated pathogenic strategies are opening a new and broader view of the complex interaction between this remarkable pathogen and the human host, providing insights at molecular level that could lead to a new rationale for the design of novel antitubercular vaccines. A vaccination strategy that simultaneously targets different steps in TB pathogenesis may result in improved protection and reduced TB transmission.

Vaccines for TB: Lessons from the Past Translating into Future Potentials

Development of vaccines for infectious diseases has come a long way with recent advancements in adjuvant developments and discovery of new antigens that are capable of eliciting strong immunological responses for sterile eradication of disease. Tuberculosis (TB) that kills nearly 2 million of the population every year is also one of the highlights of the recent developments. The availability or not of diagnostic methods for infection has implications for the control of the disease by the health systems but is not related to the immune surveillance, a phenomenon derived from the interaction between the bacteria and their host. Here, we will review the immunology of TB and current vaccine candidates for TB. Current strategies of developing new vaccines against TB will also be reviewed in order to further discuss new insights into immunotherapeutic approaches involving adjuvant and antigens combinations that might be of potential for the control of TB.

Immunogenicity without Efficacy of an Adenoviral Tuberculosis Vaccine in a Stringent Mouse Model for Immunotherapy during Treatment

To investigate if bacterial persistence during TB drug treatment could be overcome by modulation of host immunity, we adapted a clinically-relevant model developed for the evaluation of new drugs and examined if immunotherapy with two adenoviral vaccines, Ad35-TBS (AERAS-402) and Ad26-TBS, could shorten therapy in mice. Even though immunotherapy resulted in strong splenic IFN-γ responses, no effect on bacterial replication in the lungs was seen. Multiplex assay analysis of lung samples revealed the absence of cytokine augmentation such as IFN-γ, TNF-α and IL-2, suggesting that immunization failed to induce immunity in the lungs. In this model, we show that IFN-γ levels were not associated with protection against disease relapse. The results obtained from our study raise questions regarding the traits of protective TB immunity that are relevant for the development of future immunotherapeutic and post-exposure vaccination strategies.

Synergy of chemotherapy and immunotherapy revealed by a genome-scale analysis of murine tuberculosis

OBJECTIVES

Although TB immunotherapy improves the results of conventional drug treatment, the effects of combining chemotherapy and immunotherapy have never been systematically evaluated. We used a comprehensive lung transcriptome analysis to directly compare the activity of combined chemotherapy and immunotherapy with that of single treatments in a mouse model of TB.

METHODS

Mycobacterium tuberculosis-infected mice in the chronic phase of the disease (day 30) received: (i) isoniazid and rifampicin (drugs) daily for 30 days; (ii) DNA immunotherapy (DNA), consisting of four 100 μg injections at 10 day intervals; (iii) both therapies (DNA + drugs); or (iv) saline. The effects were evaluated 10 days after the end of treatment (day 70 post-infection).

RESULTS

In all groups a systemic reduction in the load of bacilli was observed, bacilli became undetectable in the drugs and DNA + drugs groups, but the whole lung transcriptome analysis showed 867 genes exclusively modulated by the DNA + drugs combination. Gene enrichment analysis indicated that DNA + drugs treatment provided synergistic effects, including the down-regulation of proinflammatory cytokines and mediators of fibrosis, as confirmed by real-time PCR, ELISA, histopathology and hydroxyproline assay.

CONCLUSIONS

Our results provide a molecular basis for the advantages of TB treatment using combined chemotherapy and DNA immunotherapy and demonstrate the synergistic effects obtained with this strategy.

An overview of tuberculosis plant-derived vaccines

Tuberculosis (TB) is a leading fatal infectious disease to which the current BCG vaccine has a questionable efficacy in adults. Thus, the development of improved vaccines against TB is needed. In addition, decreasing the cost of vaccine formulations is required for broader vaccination coverage through global vaccination programs. In this regard, the use of plants as biofactories and delivery vehicles of TB vaccines has been researched over the last decade. These studies are systematically analyzed in the present review and placed in perspective. It is considered that substantial preclinical trials are still required to address improvements in expression levels as well as immunological data. Approaches for testing additional antigenic configurations with higher yields and improved immunogenic properties are also discussed.

Purification, crystallization and preliminary X-ray crystallographic studies of Rv3899c from Mycobacterium tuberculosis

Rv3899c, a hypothetical protein from Mycobacterium tuberculosis that is conserved within the mycobacteria, is predicted to be secreted and has been found in culture filtrates. Here, Rv3899c has been cloned, expressed in Escherichia coli and purified using standard chromatographic techniques. The hanging-drop vapour-diffusion method with PEG 3350 as a precipitant was used to crystallize the protein. N-terminal sequencing results showed that the amino-acid sequence of the crystallized protein began with GATAG, indicating that it is a fragment containing residues 184-410 of Rv3899c. Rv3899c184-410 crystals exhibited the symmetry of space group P2(1)2(1)2(1), with unit-cell parameters a=49.88, b=54.72, c=75.52 Å, α=β=γ=90°, and diffracted to a resolution of 1.90 Å.

Cutaneous tuberculosis overview and current treatment regimens

Tuberculosis is one of the oldest diseases known to humankind and it is currently a worldwide threat with 8-9 million new active disease being reported every year. Among patients with co-infection of the human immunodeficiency virus (HIV), tuberculosis is ultimately responsible for the most deaths. Cutaneous tuberculosis (CTB) is uncommon, comprising 1-1.5% of all extra-pulmonary tuberculosis manifestations, which manifests only in 8.4-13.7% of all tuberculosis cases. A more accurate classification of CTB includes inoculation tuberculosis, tuberculosis from an endogenous source and haematogenous tuberculosis. There is furthermore a definite distinction between true CTB caused by Mycobacterium tuberculosis and CTB caused by atypical mycobacterium species. The lesions caused by mycobacterium species vary from small papules (e.g. primary inoculation tuberculosis) and warty lesions (e.g. tuberculosis verrucosa cutis) to massive ulcers (e.g. Buruli ulcer) and plaques (e.g. lupus vulgaris) that can be highly deformative. Treatment options for CTB are currently limited to conventional oral therapy and occasional surgical intervention in cases that require it. True CTB is treated with a combination of rifampicin, ethambutol, pyrazinamide, isoniazid and streptomycin that is tailored to individual needs. Atypical mycobacterium infections are mostly resistant to anti-tuberculous drugs and only respond to certain antibiotics. As in the case of pulmonary TB, various and relatively wide-ranging treatment regimens are available, although patient compliance is poor. The development of multi-drug and extremely drug-resistant strains has also threatened treatment outcomes. To date, no topical therapy for CTB has been identified and although conventional therapy has mostly shown positive results, there is a lack of other treatment regimens.

The present and future of tuberculosis vaccinations

The clinical, social, and economic burden of tuberculosis (TB) remains high worldwide, thereby highlighting the importance of TB prevention. The bacilli Calmette-Guérin (BCG) vaccine that is currently available can protect younger children but is less effective in adults, the major source of TB transmission. In addition, the emergence of drug-resistant Mycobacterium tuberculosis (Mtb) strains and the high prevalence of HIV infection have significantly complicated TB prognosis and treatment. Together, these data highlight the need for new and more effective vaccines. Recently, several vaccines containing multiple antigens, including some of those specific for dormant Mtb strains, have been developed. These vaccines appear to be the best approach for satisfactory Mtb prevention. However, until a new vaccine is proven more effective and safe than BCG, BCG should remain part of the immunization schedules for neonates and children at risk for TB as a fundamental prophylactic measure.