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Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains one of the world's deadliest infectious diseases. According to the World Health Organization, approximately 10.6 million people developed TB in 2021, and 1.6 million died from the disease. An estimated one-quarter of the global population has latent TB infection (LTBI), with a 5–10% lifetime risk of progressing to active disease. The spread of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains further complicates control efforts, as treatment regimens are prolonged, toxic, and costly.
The Bacille Calmette-Guérin (BCG) vaccine, derived from M. bovis and first administered in 1921, remains the only licensed TB vaccine. Over 90% of newborns worldwide receive BCG, which provides robust protection against severe childhood forms of TB, including miliary and meningeal disease. However, BCG's efficacy against adult pulmonary TB—the most common and transmissible form—is variable and incomplete, with protection waning over time. This limitation, combined with the global TB burden and drug resistance crisis, underscores the urgent need for improved TB vaccines. Furthermore, TB is the leading cause of death among people living with HIV, and co-infection synergistically accelerates disease progression, making the development of effective vaccines an even more critical global health priority.
Fig. 1 Schematic structure of Mycobacterium tuberculosis
M. tuberculosis is an acid-fast, slow-growing bacillus characterized by a complex, lipid-rich cell wall containing mycolic acids, lipoarabinomannan (LAM), and other glycolipids that contribute to its virulence and intrinsic drug resistance. Transmission occurs via inhalation of aerosolized bacilli, which reach the alveolar spaces and are phagocytosed by alveolar macrophages—the primary host cells for M. tuberculosis replication.
Following uptake, M. tuberculosis employs multiple strategies to survive within macrophages, including inhibition of phagosome-lysosome fusion, modulation of phagosomal pH, and resistance to reactive oxygen and nitrogen intermediates. Dendritic cells migrate to draining lymph nodes to prime T cells, leading to the recruitment of CD4+ Th1 cells, CD8+ T cells, and other immune cells to the site of infection.
This cellular response drives the formation of granulomas—organized immune structures that contain bacterial replication but rarely eradicate the infection completely. Protective immunity relies heavily on Th1-type cytokines, particularly interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), which activate macrophages to kill intracellular bacilli.
Fig. 2 M. tuberculosis infection and granuloma formation
The outcome of infection depends on the balance between bacterial virulence and host immunity. In most immunocompetent individuals, the infection is controlled, resulting in latent TB infection with no clinical symptoms. However, if immune surveillance wanes—due to HIV co-infection, immunosuppressive therapy, malnutrition, or aging—the bacilli can reactivate, causing active pulmonary TB with cough, fever, weight loss, and transmissibility.
Lack of Defined Immune Correlates of Protection: Unlike many viral vaccines where neutralizing antibody titers serve as established correlates, TB protection is mediated primarily by cellular immunity, and no single immunological parameter reliably predicts vaccine efficacy.
Antigen Selection Complexity: The M. tuberculosis genome encodes approximately 4,000 proteins, and the bacterium alters its antigen expression profile across different stages of infection—acute replication, persistence, and reactivation. A vaccine targeting only acute-phase antigens may fail to protect against latent or reactivated disease.
BCG Pre-immunization and Evaluation Challenges: Since most of the global population has received BCG at birth, new vaccines must demonstrate efficacy in BCG-primed individuals, and pre-existing immune memory may either enhance or interfere with vaccine responses.
Animal Model Limitations: Mouse models do not fully recapitulate human granuloma formation and latent infection, while guinea pigs and non-human primates are expensive and low-throughput. The absence of a validated animal model that precisely mirrors human TB pathogenesis further hampers candidate selection and dose optimization.
TB vaccine candidates in clinical development can be categorized by their intended use: pre-exposure vaccines to replace or improve BCG, booster vaccines to enhance BCG-induced immunity, and therapeutic vaccines to treat latent or active infection.
Fig. 3 TB vaccine candidates in clinical development, categorized by platform type and current clinical trial phase.
These candidates aim to provide broader and more durable protection than BCG when administered before exposure. Recombinant BCG strains have been engineered to express additional M. tuberculosis antigens or to improve safety and immunogenicity. VPM1002 (BCGΔureC::hly), which expresses listeriolysin O to facilitate phagosomal escape, has completed Phase II trials. MTBVAC, a live attenuated M. tuberculosis strain with deletions in phoP and fadD26, is also in Phase II evaluation. Whole-cell inactivated or fractionated mycobacterial vaccines, such as MIP (Mycobacterium indicus pranii) and DAR-901, are being evaluated for broad immune stimulation.
Booster vaccines are designed to be administered after BCG priming to enhance and prolong protective immunity.
Adjuvanted protein subunit vaccines contain defined M. tuberculosis antigens formulated with potent adjuvants. M72/AS01E, consisting of the Mtb32A and Mtb39A antigens with the AS01E adjuvant, reported approximately 50% vaccine efficacy against confirmed pulmonary TB in a Phase IIb trial—an important milestone as the first subunit vaccine to demonstrate significant protection. Other candidates include ID93+GLA-SE, H56/IC31 (Ag85B-ESAT-6-Rv2660c fusion), and GamTBvac. These subunit vaccines offer favorable safety profiles and can be rationally designed to target specific antigens, but their efficacy depends heavily on adjuvant selection and antigen combination.
Viral-vectored vaccines use replication-deficient viral vectors to deliver M. tuberculosis antigens, inducing strong CD8+ T cell responses without exogenous adjuvants. ChAdOx1.85A and Ad5Ag85A have been evaluated in clinical trials, often in heterologous prime-boost regimens to circumvent anti-vector immunity.
Therapeutic vaccines aim to treat established infection by boosting immune responses to eliminate or contain persistent bacilli. RUTI, a fragmented whole-cell vaccine, is being developed for treatment of latent TB infection. H56/IC31 is also being evaluated as a therapeutic vaccine to shorten chemotherapy duration. Inactivated mycobacterial preparations such as Vaccae™ and MIP have been explored as adjunctive immunotherapy for active TB.
The selection of appropriate antigens is central to TB vaccine development.
The early secreted antigenic target ESAT-6 (Rv3875) and culture filtrate protein CFP-10 (Rv3874), secreted via the ESX-1 type VII secretion system during early infection, are highly immunogenic T cell targets and components of several vaccine candidates.
The antigen 85 (Ag85) complex—comprising Ag85A, Ag85B, and Ag85C—consists of mycolyltransferases involved in cell wall biogenesis. These abundant secreted proteins are highly immunogenic and serve as core antigens in multiple vaccine candidates, including M72 and ChAdOx1.85A. MPT64 (Rv1980c), another secreted protein, is highly specific to the M. tuberculosis complex and is used in vaccine research and diagnostic development.
Under hypoxic conditions within granulomas, M. tuberculosis upregulates the DosR regulon, encoding latency-associated proteins. HspX (Rv2031c, 16 kDa alpha-crystallin) is a well-characterized latency antigen explored in therapeutic vaccine designs, while Rv2660c is a component of the H56 vaccine candidate.
The 38 kDa protein (PstS1, Rv0934), a phosphate transport lipoprotein, is a strong inducer of humoral and cellular immunity and is widely used in TB diagnostics and vaccine research. Lipoarabinomannan (LAM), a major cell wall glycolipid, is recognized by innate immune receptors and serves as a target for antigen detection assays.
The growing recognition that no single antigen provides comprehensive protection has driven the development of multi-antigen vaccines combining antigens expressed across different stages of the M. tuberculosis life cycle.
Tuberculosis remains a global health emergency, and the development of more effective vaccines is critical for achieving elimination goals. While BCG has saved millions of lives, its limitations against adult pulmonary TB and the growing threat of drug-resistant strains demand innovative vaccine approaches. Advances in understanding M. tuberculosis pathogenesis, host immunity, and antigen biology have led to a diverse pipeline of vaccine candidates, with adjuvanted subunit vaccines showing promising clinical efficacy. Continued investment in basic research, clinical trial infrastructure, and global collaboration is essential to deliver a new generation of TB vaccines.
| Cat. No. | Product Name | Species Reactivity | Sample | |
| DEIA1926 | M. tuberculosis IgG ELISA Kit | Human | Serum, plasma or cerebrospinal fluid (CSF) | Inquiry |
| DEIA381 | M. tuberculosis IgG ELISA Kit | Human | Serum, plasma and cerebrospinal fluid | Inquiry |
| DEIA384 | M. tuberculosis IgG ELISA Kit, Sensitive | Human | Serum, plasma | Inquiry |
| DEIA083 | M. tuberculosis IgG ELISA Kit | Human | Serum, plasma | Inquiry |
| DEIA1023 | M. tuberculosis IgG ELISA Kit | Human | Serum, plasma | Inquiry |
| DEIA1924 | M. tuberculosis IgA ELISA Kit | Human | Serum, plasma | Inquiry |
| DEIA382 | M. tuberculosis IgA ELISA Kit | Human | Serum, plasma | Inquiry |
| DEIA385 | M. tuberculosis IgA ELISA Kit, Sensitive | Human | Serum, plasma | Inquiry |
| DEIA383 | M. tuberculosis IgM ELISA Kit | Human | Serum, plasma | Inquiry |
| DEIA386 | M. tuberculosis IgM ELISA Kit | Human | Serum | Inquiry |
| DEIA561 | M. avium (MAP) Antibody ELISA Kit | Cattle, Sheep, Goat | Serum, plasma, milk | Inquiry |
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