Exploring the Effect of Probiotics, Prebiotics, and Postbiotics in Strengthening Immune Activity in the Elderly

Abstract

Vaccination is the easiest way to stimulate the immune system to confer protection from disease. However, the inefficacy of vaccination in the elderly, especially those under nutritional control such as individuals receiving artificial nutrition after cerebral infarction or during dementia, has led to the search for an adjuvant to augment the acquired immune response in this population. The cross-talk between the gut microbiota and the host immune system is gaining attention as a potential adjuvant for vaccines. Probiotics, prebiotics, and postbiotics, which are commonly used to modulate gut health, may enhance the immune response and the effectiveness of vaccination in the elderly. This review summarizes the use of these gut modulators as adjuvants to boost both the innate and acquired immune responses in the elderly under nutritional control. Although the clinical evidence on this topic is limited and the initial findings await clarification through future studies with large sample sizes and proper study designs, they highlight the necessity for additional research in this field, especially in light of the ongoing COVID-19 pandemic, which is disproportionately affecting the elderly.

Keywords: elderly; gut microbiota (GM); immunity; influenza; postbiotic; prebiotic; probiotic; vaccination.

Figure 1

(a) Predicted global population trend by age group from 1990 to 2050 *. (b) Estimated number of annual influenza-associated deaths with underlying respiratory or circulation failure by age group, in the United States from 1976–2007 [12]. United Nations Department of Economic and Social Affairs, Population Division (2019) [2].

Figure 2

Modulation of the gut environment with probiotics, postbiotics, or prebiotics enhances the innate and acquired immunity of the elderly. Specifically, the ingestion of probiotics increases the population of Bifidobacterium in the elderly, augments the innate immune response by increasing the activities of natural killer (NK) cells, and increases the serum antibody titers against influenza antigen through cell interactions and the secretion of bioactive metabolites, such as short-chain fatty acid (SCFA), by immune cells. In contrast, postbiotics augment a vaccine’s effect by promoting the activation and secretion of serum antibodies against influenza antigens in the elderly. Prebiotics act as stimulants that promote the growth of the gut’s beneficial microbes (Bifidobacterium, Lactobacillus, and Bacteroides), thereby activating the host immune response via cellular interactions and bioactive metabolites from the beneficial microbes, thus increasing antibody production and innate immune responses to influenza. These points highlight the potential of an adjuvant effect but await confirmation by future research.