Researchers have successfully engineered Lactiplantibacillus plantarum, commonly known as L. plantarum, to produce and surface-display neoantigens for potential cancer immunotherapy. This innovative study reveals how the bacterial host can be utilized to effectively deliver targeted immune responses against cancer cells.
The production and display of neoantigens—specific immune targets derived from tumor cells—are becoming increasingly important in personalized cancer treatments. With the ability to produce these antigens embedded on the surface of non-pathogenic bacteria, scientists hope to develop effective therapies to stimulate the body’s immune system to attack cancer more efficiently.
Conducted by researchers, including K. Wiull, E. Holmgren, and S. Svensson, the study investigates the production of two murine-derived neoantigens: NAG1 and ETV6. The findings, published on March 5, 2025, indicate these antigens can be displayed on the bacterial surface using the inducible pSIP expression system.
The study addresses the challenge of delivering therapeutic proteins to immune cells. Traditional soluble antigen delivery often encounters rapid degradation by proteolytic enzymes. By anchoring antigens to the bacterial cell wall or membrane, the researchers found this could potentially protect the antigens and improve immune response rates.
The researchers crafted various expression vectors utilizing four different anchoring methods—N-terminal transmembrane (NTTM), lipoprotein (Lipo), LysM, and LPxTG. Preliminary analyses indicate the best results came from antigens anchored to the cell wall. These methods allow for versatile targeting, enhancing the presentation of neoantigens directly to immune cells, thereby boosting immune detection.
Experiments confirmed successful protein production and surface display of both neoantigens. Researchers noted significant differences based on anchoring methods used. Specifically, NAG1-producing strains with LysM anchors exhibited the strongest surface exposure compared to membrane-anchored proteins.
Aside from assessing the spatial exposure of these antigens, the team also conducted growth analysis on the engineered strains. The results highlighted marked variations, particularly noting significantly slower growth rates for strains with NTTM and LPxTG anchors. These observations elucidate the trade-offs inherent with different anchoring strategies. While offering enhanced immune exposure, some anchoring methods may cause cellular stress, impacting overall bacterial growth.
To evaluate the immunogenicity of the neoantigens, western blot analyses demonstrated the effective production of both NAG1 and ETV6 across the engineered expression strains. Flow cytometry was employed to gauge the surface display of these antigens, which showed markedly stronger signals for NAG1 when compared to ETV6.
Interestingly, the study also delved to see whether UV-inactivated L. plantarum retained its immunogenic properties. Remarkably, even when rendered non-viable, the bacteria still effectively presented the antigens at the surface, indicating potential for these strains to be used as safe delivery mechanisms without posing infection risks.
Since lactobacilli are widely recognized as probiotics with promising immune-modulatory capabilities, this approach not only enhances the protective strategies of these engineered bacterial strains but also potentially expands their application scope for vaccines targeting various pathogens.
The findings of this study open avenues for more personalized cancer treatments. By engineering L. plantarum to produce specific neoantigens, the authors indicate their potential utility for developing effective therapeutic cancer vaccines. "It is conceivable these recombinant LAB strains can be developed as tools for efficient personalized cancer therapy," the authors of the article wrote.
Looking forward, the researchers acknowledge the importance of evaluating the immunogenicity of their engineered strains through rigorous testing. This is to assess the effectiveness of neoantigen presentation and their potential for clinical applications. Such studies could potentially transform the way immunotherapies are approached, using the body’s own defenses to combat cancer based on unique tumor antigens.
This research exemplifies the potential for L. plantarum as not just nutritional probiotics but also as innovative platforms for targeted therapeutics, offering hope for future generations facing cancer treatments.