Probiotics as Adjuvants in Vaccine Strategy: Is There More Room for Improvement?

Abstract

Background. It has been recognized that microbiota plays a key role in shaping immune system maturation and activity. Since probiotic administration influences the microbiota composition and acts as a biological response modifier, the efficacy of an adjuvant for boosting vaccine-specific immunity is investigated. Methods. A review of the literature was performed, starting from the mechanisms to laboratory and clinical evidence. Results. The mechanisms, and in vitro and animal models provide biological plausibility for microbiota use. Probiotics have been investigated as adjuvants in farm conditions and as models to understand their potential in human vaccinations with promising results. In human studies, although probiotics were effective in ameliorating seroconversion to vaccines for influenza, rotavirus and other micro-organisms, the results for clinical use are still controversial, especially in particular settings, such as during the last trimester of pregnancy. Conclusion. Although this topic remains controversial, the use of probiotics as adjuvant factors in vaccination represents a strategic key for different applications. The available data are deeply influenced by heterogeneity among studies in terms of strains, timing and duration of administration, and patients. Although these do not allow us to draw definitive conclusions, probiotics as adjuvants in vaccination should be considered in future studies, especially in the elderly and in children, where vaccine effectiveness and duration of immunization really matter.

Effects of Loigolactobacillus coryniformis K8 CECT 5711 on the Immune Response of Elderly Subjects to COVID-19 Vaccination: A Randomized Controlled Trial

“…These data support the approach of using probiotic supplementation as adjuvants for boosting immunity and enhancing vaccine-specific responses in the elderly population [ 24 , 25 ] and corroborate the capability of the probiotic strain L. coryniformis K8 to enhance the immune response [ 22 , 23 ]. Herein, we report the findings of a randomized, placebo-controlled, double-blind trial to assess the effect of the consumption of the probiotic strain L. coryniformis K8 CECT 5711 on the immune response generated by the COVID-19 vaccine in an elderly population.…”

“…Vaccination has been proven essential for the reduction in the severity and mortality of older subjects [ 30 , 31 ], but it is known that age-related immune response defects provoke a lower level of protection after vaccination compared to younger subjects [ 11 , 12 , 13 ]. In this sense, several authors have highlighted the importance of using probiotic supplementation as adjuvants for boosting immunity and enhancing vaccine-specific responses in the elderly population [ 24 , 25 ]. However, to our knowledge, this is the first randomized clinical trial evidencing the usefulness of the administration of a probiotic strain in the context of the COVID-19 pandemic in elderly people by enhancing the specific immune response after COVID-19 infection and by helping vaccine-specific responses in the oldest population.…”

Fighting the SARS-CoV-2 pandemic requires a global approach to understanding the heterogeneity of vaccine responses

“…to these inconsistent findings 154,155 . Although such interventions could not realistically be implemented globally in the context of a pandemic, they could be used to help improve vaccine responsiveness to specific populations, including the elderly, those that are immunocompromised and those that have previously demonstrated a suboptimal vaccine response.…”

Irradiated Non-replicative Lactic Acid Bacteria Preserve Metabolic Activity While Exhibiting Diverse Immune Modulation

“…This is achieved by the activation of different pathways leading to a broad and diverse expression of T helper cell subsets, such as Th1, Th2, Th17, and T-regulatory (Treg), inducing the production of different sets of cytokines ( 14 ). A broad and diverse immune stimulation is a common characteristic of vaccine adjuvants ( 15 ), and some LAB strains have displayed a notable potential for their application in several vaccine formulations ( 16 – 18 ).…”