Instead of direct sterilization, awaken host immunity: Latest trends in antibiotic immunotherapy to overcome multidrug-resistant bacteria
Background
Conventional antibiotics treat infectious diseases by directly killing bacteria or inhibiting their growth. However, as pathogens adapt, humanity faces the crisis of antimicrobial resistance (AMR). In particular, the emergence of multidrug-resistant (MDR) pathogens, which exhibit resistance to multiple drugs, poses a significant challenge to modern medicine. These pathogens employ survival strategies such as secreting drug-degrading enzymes or modifying their targets. They also overexpress efflux pumps to expel drugs and form physical barriers in the form of biofilms. Furthermore, they can even temporarily halt their metabolism to withstand drug attacks, forming persistent cells that make treatment difficult. This leads to chronic and recurrent infections, increasing the patient's hospital stay and healthcare costs. Therefore, establishing a new paradigm that deviates from conventional sterilization methods has become an urgent issue.
Currently, drug repurposing, bacteriophage therapy, and CRISPR-Cas gene editing technology are being explored as alternatives. However, these alternatives also have significant limitations. Existing drugs struggle to overcome resistance, and bacteriophages are easily cleared by the host's immune response. Gene editing also presents challenges in terms of delivery vector development and safety. To overcome these barriers, attention has been focused on the interaction between pathogens and the host immune system, leading to the emergence of antibiotic immunotherapy as an alternative, which aims to enhance the patient's immune function instead of directly killing bacteria.
Key Findings
A research team from Shenzhen University, China, systematically analyzed the types and mechanisms of antibiotic immunotherapy in a paper published in the international journal 'Infection and Drug Resistance (IDR)'. The research team focuses on the potential of immunomodulatory agents for therapeutic purposes, beyond prophylactic vaccines. A representative example is the use of monoclonal antibodies (mAbs) to neutralize bacterial toxins. Bezlotoxumab, which has been approved by the U.S. Food and Drug Administration (FDA), targets Clostridioides difficile toxin and effectively inhibits recurrent infections, demonstrating this approach.
The research team summarized clinical data on mAbs, probiotics that regulate the gut microbiome, cell-based therapies that directly administer patient immune cells, and aptamers that bind to specific molecules of bacteria. Antimicrobial peptides (AMPs), which directly destroy bacterial membranes and stimulate immunity, are also promising candidates. Among these, host-directed therapy (HDT) is considered an alternative with no risk of resistance, as it regulates human metabolic pathways and inflammatory signaling systems to inhibit the bacterial survival environment. Nanoplatforms, which incorporate nanotechnology to precisely deliver immune substances, are also recognized as technologies that enhance efficiency.
Significance and Prospects
Antibiotic immunotherapy does not directly attack bacteria but activates the body's natural defense system, significantly reducing the probability of resistance acquisition. This provides a foundation for breaking the vicious cycle of resistance that occurs with the use of single agents. When used in combination with existing antibiotics, it is expected to have a synergistic effect, shortening the treatment period and reducing the dosage, thereby minimizing side effects. However, there are several barriers that must be overcome before it can reach the clinical and commercialization stages. HDT has the characteristic that the response varies depending on the individual patient's immune status, making it difficult to evaluate standardized efficacy. In particular, in urgent situations such as acute sepsis, excessive immune activation may pose a risk of organ damage.
Production costs and regulatory easing also need to be addressed. mAbs and cell-based therapies have complex manufacturing processes and high unit costs, making global distribution challenging. Regulatory authorities, including the FDA, also find it difficult to apply existing antibiotic efficacy evaluation criteria directly to immunomodulatory agents, so new clinical trial design standards need to be established. Nevertheless, this analysis is significant in that it establishes an integrated design standard that considers the dynamic relationship between pathogens and the host. If safety verification and large-scale production technology development are carried out in parallel, it is expected to become a powerful stockpile against MDR bacteria.
Antimicrobial resistance (AMR) continues to compromise the effectiveness of conventional antibacterial therapy, driving the development of therapeutic strategies that extend beyond direct antibiotic-mediated bacterial killing. Multidrug-resistant (MDR) pathogens evade treatment through diverse mechanisms, including enzymatic drug inactivation, target modification, efflux pump overexpression, biofilm formation, and persisters development. AMR results in chronic and recurrent infections, prolonged hospitalization, increased healthcare costs, and elevated morbidity and mortality, underscoring the need for innovative therapeutic approaches that target both the pathogen and the host. To bridge the dynamic interplay between bacterial pathogens and the host immune system with emerging therapeutic innovations, this narrative review first examines the biological mechanisms underlying bacterial resistance. It then explores therapeutic strategies beyond conventional antibiotics, providing an overview of current approaches and their limitations, including drug repurposing, bacteriophage therapy, and CRISPR-Cas technology. The review subsequently focuses on antibacterial immunotherapy, discussing a broad range of emerging approaches, including probiotics, monoclonal antibodies, cell-based therapies, host-directed therapies, aptamers, nanotechnology-based platforms, cytokine-based therapies, and antimicrobial peptides. An integrated overview of preclinical evidence, clinical studies, and FDA-approved therapies is presented to assess the translational potential of immunotherapy strategies in combating AMR. Scientific, regulatory, manufacturing, and implementation challenges that influence their successful translation into clinical practice are discussed throughout. By integrating the biological basis of host-pathogen interactions with emerging antibacterial therapeutics and their translational development, this review provides a comprehensive framework for evaluating innovative st
This study demonstrates a new direction for treating intractable infections in patients with chronic diseases or impaired immunity. For example, a representative approach is the co-administration of nanoparticles loaded with mAbs and AMPs to patients with urinary tract infections in which biofilm formation in the hospital makes antibiotic penetration difficult. This mechanism results in the direct destruction of bacterial outer membranes and the activation of phagocytic cells in the patient's body, leading to the complete clearance of resistant bacteria. In addition, it normalizes the immune system as quickly as possible by administering customized probiotics and cytokines to patients with disrupted gut microbial ecosystems due to antibiotic misuse. If this scenario is established in clinical practice, it is expected to reduce unnecessary antibiotic prescriptions and significantly shorten the patient's hospital stay.