Boosting vaccine effectiveness: The groundbreaking role of probiotics

Probiotics, the health -promoting members of the gut microbiota, have been shown to enhance mucosal and systemic immunity, stimulate cytokines, chemokines, and antibodies, and regulate T -cell activity. On the other hand, traditional adjuvants like alum have limitations, and researchers are exploring probiotics as a new generation of vaccine adjuvants to treat immune disorders and enhance vaccine effectiveness. For instance, studies show that probiotic strains like Lactobacillus rhamnosus GG (LGG) can improve the immune response to vaccines against rotavirus, SARS-CoV-2, and influenza. Besides, probiotic adjuvants delivered through various mucosal routes (oral and ocular) could offer broader protection against a wider range of infections. On the other hand, probiotics can not only boost the immune system but also trigger the production of anti-inflammatory cytokines and regulatory immune cells, as they have shown potential in cancer immunotherapy. Studies demonstrate that probiotics like LGG and Bifidobacterium longum can increase the efficacy of cancer vaccines by promoting T cell infiltration, thereby inhibiting tumor growth. Additionally, studies suggest specific probiotic strains like L. rhamnosus SL42 and L. casei might be beneficial for cow's milk allergies. In line with this, research on the use of probiotics for peanut allergies shows promise. However, there is a need for more research to understand mechanisms, identify optimal strains, and determine the timing and duration of administration for clinical outcomes. This review aimed to shed light on the impact of probiotics as immunomodulatory and immunogenic agents in vaccine immunizations, as well as their use as adjuvants for infectious diseases, allergies, and cancer suppression.