Screening and in silico evaluation of candidate late-stage antigens for incorporation into multi-stage and post-exposure vaccines against tuberculosis

Why this matters for everyday health

Tuberculosis (TB) is often thought of as a disease of the past, yet a quarter of the world’s population silently carries its cause, the bacterium Mycobacterium tuberculosis, in a dormant state. Most of these people feel perfectly well, but if their defences weaken, the infection can flare up and become contagious. Current vaccines do a reasonable job of protecting young children from severe TB, but they do little to stop this hidden reservoir from reawakening. This article explores a new strategy: designing vaccines that specifically target bacterial proteins active during the quiet, late stages of infection, with the goal of preventing reactivation and cutting transmission at its source.

How TB hides and returns

After TB bacteria are inhaled into the lungs, the immune system often walls them off in compact clusters of cells called granulomas. In many people this leads to “latent” infection: the bacteria are alive but slowed down, causing no symptoms and spreading to no one. Years later, if the immune system is weakened by aging, HIV, malnutrition, diabetes, or certain medicines, these granulomas can break down and the bacteria resume active growth, causing full-blown TB disease. During this journey from early infection through dormancy to reactivation, the bacteria switch on different sets of genes and proteins. The review calls the proteins associated with latency, resuscitation, and reactivation “late-stage antigens,” and argues they are prime targets for next‑generation vaccines.

Limits of the current TB vaccine

The only licensed TB vaccine, BCG, is based on a weakened relative of TB bacteria. It protects young children from severe forms of disease for several years, but its protection against adult lung TB is highly variable and it does not reliably prevent latent infection or reactivation later in life. BCG’s genome lacks several important TB proteins and, crucially, it does not persist long enough in healthy people to strongly express late-stage antigens. Studies show that people vaccinated with BCG rarely develop strong immune responses to latency- and resuscitation-related proteins, whereas individuals naturally exposed to TB often do. This mismatch helps explain why BCG cannot by itself solve the problem of the vast latent TB reservoir.

Finding the most promising bacterial targets

To build better vaccines, researchers have systematically screened TB proteins that are turned on during latency and reactivation. They compare immune responses in people with latent infection, patients with active TB, and uninfected volunteers. Late-stage antigens that trigger stronger responses in latently infected but healthy people than in those with active disease are seen as promising, because they may be linked to natural control of infection. Animal studies then test whether these proteins can stimulate protective T cells and antibodies and reduce bacterial counts after challenge. The review distils many such studies into a short list of latency antigens and resuscitation-promoting factors that are frequently recognized across different human populations, perform well in animal models, and look favourable in computer analyses that predict how broadly they will be recognized by diverse immune systems.

Designing safe and effective new vaccines

Turning these proteins into real-world vaccines is not straightforward. Because candidates are meant for people who are already infected or previously treated, safety is critical: boosting the wrong type of immune response could inflame old lesions or even help dormant bacteria to wake up. The article recommends a stepwise path: first verify that candidate antigens are recognized in blood from latently infected people, then test their ability to induce protective, balanced T helper 1 and T helper 17 responses in animals, followed by challenge experiments that probe whether they prevent reactivation without worsening disease. Computer tools help rank antigens by predicted strength and breadth of immune recognition, and flag those that might be allergenic or closely resemble proteins from harmless environmental mycobacteria, which could blunt vaccine effects.

Real-world vaccine examples and remaining hurdles

The review highlights several experimental vaccines that already include late-stage antigens, such as H56:IC31 and ID93 + GLA-SE, which fuse early TB proteins with latency-associated ones and pair them with powerful immune-boosting adjuvants. These have shown encouraging immune responses and partial protection in animals and early human trials, though one candidate unexpectedly failed to prevent TB relapse in cured patients, underscoring the complexity of post-exposure vaccination. Another vaccine, M72/AS01_E, which uses only early-stage proteins, has nonetheless achieved about 50% protection against disease in adults with latent infection, proving that post-exposure vaccination is possible but not yet optimized. Large, long-term clinical trials, strict safety monitoring, and practical issues such as heat-stable formulations and cost will all shape whether such vaccines can be widely deployed.

What this means for the future of TB control

The central message of the article is that targeting late-stage TB antigens could transform how we control a disease that still kills more than a million people each year. By focusing on the proteins the bacterium uses to endure dormancy and restart growth, scientists hope to craft vaccines that not only prevent initial infection but also lock down existing latent bacteria and stop them from reigniting disease. Although many scientific, clinical, and regulatory challenges remain, the careful screening, computer-assisted ranking, and early clinical testing of these antigens are laying the groundwork for multi-stage and post-exposure vaccines that could finally shrink the global reservoir of silent TB infection.

Citation: Ashayeripanah, M. Screening and in silico evaluation of candidate late-stage antigens for incorporation into multi-stage and post-exposure vaccines against tuberculosis. npj Vaccines 11, 72 (2026). https://doi.org/10.1038/s41541-026-01394-z

Keywords: tuberculosis vaccines, latent tuberculosis, late-stage antigens, post-exposure vaccination, BCG limitations