By Suherman Candra Maholtra 
In a significant breakthrough for global infectious disease research, scientists at Johns Hopkins Medicine and the Johns Hopkins Bloomberg School of Public Health have announced the development of an experimental DNA-based vaccine for tuberculosis (TB) designed for intranasal administration. This therapeutic vaccine represents a novel approach to one of the world’s oldest and most resilient pathogens by specifically targeting "persister" bacteria—subpopulations of Mycobacterium tuberculosis that enter a dormant, drug-tolerant state to survive standard antibiotic treatments. By stimulating the immune system to recognize and eliminate these hidden reservoirs, the vaccine aims to shorten treatment durations and prevent the high rates of disease relapse that currently plague TB recovery efforts. The comprehensive findings of this multi-year study were recently published in the Journal of Clinical Investigation.
The Persistent Challenge of Global Tuberculosis
Tuberculosis is an ancient scourge, with evidence of its presence in human populations dating back at least 6,000 years. Despite the advent of modern antibiotics in the mid-20th century, TB remains the leading cause of death from a single infectious pathogen globally, often surpassing the annual mortality rates of HIV/AIDS and malaria. According to the World Health Organization (WHO) 2024 Global Tuberculosis Report, approximately 10.8 million people fell ill with TB in 2023, and the disease claimed 1.25 million lives.
A primary obstacle to the total eradication of TB is the phenomenon of latency and persistence. The WHO estimates that roughly one-quarter of the global population—approximately 2 billion people—carries a latent TB infection. While these individuals do not show symptoms and are not contagious, the bacteria remain viable within their bodies. Even in active cases, current treatment regimens are notoriously difficult, requiring patients to take a combination of potent antibiotics for six to nine months. The length and toxicity of these regimens often lead to poor patient compliance, which in turn fuels the rise of multidrug-resistant TB (MDR-TB) and provides an opportunity for "persister" bacteria to survive and trigger a relapse months or years after treatment concludes.
Innovation in Vaccine Design: The Mip3α/relMtb Fusion
The experimental vaccine developed by the Johns Hopkins team, led by Styliani Karanika, M.D., an assistant professor of medicine at the Johns Hopkins University School of Medicine, utilizes a sophisticated DNA fusion strategy. Unlike traditional vaccines that often focus on preventing initial infection, this therapeutic vaccine is designed to work in tandem with existing drug therapies to bolster the host’s immune response during the recovery phase.
The vaccine architecture involves the fusion of two specific genes: relMtb and Mip3α. The relMtb gene is a critical survival mechanism for the TB bacterium; it produces the RelMtb protein, which allows the microbe to sense and respond to hostile environments, such as those created by antibiotic exposure, low oxygen levels, or nutrient scarcity. By switching to a persistent state, the bacteria become "invisible" to drugs that typically target actively dividing cells.
By incorporating the relMtb gene into the vaccine, the researchers are essentially training the immune system to recognize the very protein the bacteria use to hide. To ensure this signal is received by the right immune "sentinels," the team fused it with Mip3α (Macrophage Inflammatory Protein 3-alpha). This gene produces a signaling protein that acts as a chemical beacon for immature dendritic cells. These cells are the primary "professional" antigen-presenting cells of the immune system; they capture foreign proteins and present them to T cells, thereby initiating a highly specific and aggressive immune attack.
The Strategic Advantage of Intranasal Delivery
A key feature of the Johns Hopkins vaccine is its delivery through the nose. Most vaccines are administered via intramuscular injection, which generates a systemic immune response but may not provide optimal protection at the primary site of infection. Because Mycobacterium tuberculosis is an airborne pathogen that infects the lungs, the researchers chose the intranasal route to target the respiratory mucosa.
"Intranasal delivery focuses vaccination on the respiratory mucosa in the lungs where TB infection occurs," explains Dr. Karanika. "This helps generate long-lasting localized T-cell immunity in the airways and lungs, along with systemic immune responses."
This localized approach creates a "front-line" defense of T cells within the lung tissue itself. By establishing a robust immune presence at the point of entry and the primary site of bacterial persistence, the vaccine can more effectively coordinate the destruction of bacteria as they attempt to reactivate or survive antibiotic stress.
Evidence from Preclinical Trials: Mice and Macaques
The research team conducted extensive testing to validate the efficacy of the DNA fusion vaccine. In the initial phase involving mouse models, the results were highly promising. When administered alongside first-line TB antibiotics, the vaccine significantly accelerated the clearance of bacteria from the lungs. Perhaps most importantly, the mice treated with the combination of drugs and the vaccine showed a dramatic reduction in relapse rates compared to those treated with antibiotics alone.
The study also demonstrated that the vaccine enhanced the effectiveness of the BPaL regimen—a potent combination of bedaquiline, pretomanid, and linezolid used to treat highly drug-resistant forms of TB. This suggests that the vaccine could become a critical tool in the fight against MDR-TB, where treatment options are limited and often involve severe side effects.
Following the success in mice, the team moved to a nonhuman primate model involving rhesus macaques. While this stage of the study did not involve an active TB challenge, it focused on the vaccine’s ability to generate a durable immune response in a biological system closely resembling that of humans. The intranasal vaccine successfully induced measurable TB-specific immune responses in both the bloodstream and the airways of the macaques. These responses remained detectable for at least six months, indicating the potential for long-term protection.
The data from the macaques showed increased recruitment and activation of CD4+ (helper) and CD8+ (killer) T cells, which are the cornerstones of the body’s cellular defense against intracellular pathogens like TB. The organization of these cells within the lung tissue suggested a sophisticated and targeted immune architecture capable of responding to persistent bacterial threats.
Analysis of Implications and Global Health Strategy
The development of the Mip3α/relMtb vaccine aligns with the WHO’s "End TB Strategy," which calls for the development of new tools, including therapeutic vaccines, to reduce TB incidence by 90% and TB deaths by 95% by 2035. The current standard vaccine, BCG (Bacille Calmette-Guérin), was developed over a century ago. While it is effective at preventing severe forms of TB in children, it offers limited and highly variable protection against pulmonary TB in adults, which is the primary driver of the global epidemic.
The Johns Hopkins DNA vaccine offers several potential advantages over traditional platforms:
- Stability and Logistics: DNA vaccines are generally more stable at higher temperatures than mRNA or live-attenuated vaccines. This is a crucial factor for distribution in low- and middle-income countries (LMICs) where cold-chain infrastructure may be unreliable.
- Shorter Treatment Regimens: If human trials mirror the animal results, the vaccine could allow clinicians to shorten the current six-month treatment window, significantly reducing the economic and physical burden on patients.
- Combating Resistance: By empowering the immune system to kill drug-tolerant persisters, the vaccine reduces the likelihood of these bacteria mutating into fully drug-resistant strains.
Future Research and Path to Clinical Trials
Despite the encouraging results, the transition from animal models to human clinical trials requires further validation. The next steps for the Johns Hopkins team involve more rigorous preclinical work to determine the optimal dosage and to further investigate the safety profile of the intranasal DNA delivery system.
"These nonhuman primate data are encouraging because they show that the vaccine can generate durable, antigen-stimulated immune responses in an animal model whose immune system more closely resembles that of humans," Dr. Karanika noted. "That gives us an important translational bridge."
The study received support from several major institutions, including the National Institutes of Health (NIH), the Johns Hopkins University Tuberculosis Research Advancement Center, and the Gilead HIV Research Scholar Award. The researchers have also filed a patent for the Mip3α/relMtb vaccine technology, signaling their intent to move toward commercial development and eventual public health implementation.
As the global medical community continues to grapple with the rising threat of antimicrobial resistance, the shift toward immunotherapy—using the body’s own defenses to finish what antibiotics start—represents a paradigm shift in infectious disease management. For the millions of people affected by tuberculosis every year, this intranasal DNA vaccine offers a glimmer of hope for a future where the disease is not just treated, but truly eradicated.
