Lectins as Adjuvants and Vaccine Delivery Systems: A Mini-Review

Lectins are carbohydrate-binding proteins that have emerged as promising candidates for vaccine development due to their dual roles as immunomodulatory agents and antigen delivery systems. Through specific interactions with glycans expressed on immune and epithelial cells, lectins can enhance antigen uptake, processing, and presentation, modulating innate and adaptive immune responses. Several lectins have been shown to activate antigen-presenting cells, stimulate cytokine production, and promote Th1- or Th2-biased immune responses by recognizing glycosylated receptors, including Toll-like receptors. These properties make lectins attractive alternatives or complements to conventional vaccine adjuvants. This mini-review summarizes recent advances in the application of lectins as vaccine adjuvants and delivery platforms. We discuss their mechanisms of action, their contribution to innate and mucosal immunity, and their ability to target antigens to specialized cells, such as dendritic cells and intestinal M cells. Special emphasis is placed on mucosal vaccination strategies, where lectins exhibit unique advantages due to their resistance to gastrointestinal degradation, mucoadhesive properties, and ability to facilitate transepithelial transport of antigens. We also highlight potential uses of lectin-functionalized Poly(lactic-co-glycolic acid) (PLGA) nanoparticles, which combine antigenic protection, targeted delivery, and immunostimulatory activity. In addition, emerging approaches employing lectin-based surface display systems in microorganisms are discussed as innovative platforms for antigen presentation and vaccine development. Although several challenges remain regarding safety, standardization, and clinical translation, the accumulating evidence indicates that lectins represent versatile tools for increasing vaccine efficacy. A deeper understanding of lectinglycan interactions may support the development of next-generation vaccines capable of inducing robust, targeted, and long-lasting protective immune responses.