Abstract

Recombinant Listeriolysin O (rLLO), a cholesterol-dependent cytolysin come from Listeria monocytogenes, has gained increasing attention as a novel immunological adjuvant for next-generation vaccine development. rLLO enhances both innate and adaptive immune responses by facilitating controlled endosomal membrane permeabilization, promoting cytosolic antigen delivery, and enabling efficient antigen cross-presentation, leading to robust CD8⁺ T-cell activation. These immunological properties are particularly advantageous for vaccines targeting intracellular pathogens and malignancies. This narrative review synthesizes current experimental, preclinical, and translational evidence on the application of rLLO across diverse vaccine platforms in human and veterinary medicine, including DNA-, protein-, nanoparticle-, and vector-based formulations. Studies addressing infectious diseases such as tuberculosis, HIV, dengue, and listeriosis, as well as cancer immunotherapy models, are critically examined. Emerging strategies involving fusion proteins, detoxified rLLO mutants, and recombinant delivery systems are highlighted to illustrate advances in formulation design and immunogenic optimization. Despite promising preclinical outcomes, several challenges remain, including the need for comprehensive safety evaluation, optimization of dosing and delivery strategies, and clarification of regulatory pathways. Addressing these limitations through standardized toxicological assessment and large-scale clinical and veterinary trials will be essential for the successful translation of rLLO-based vaccine components. Overall, rLLO represents a versatile and potent immunological tool with significant potential to advance vaccine design in both human and veterinary applications.

Key words: Listeria monocytogenes; Vaccine development; Immune response; CD8+ T cells.