Aging and the Immune System: the Impact of Immunosenescence on Viral Infection, Immunity and Vaccine Immunogenicity

Abstract

Immunosenescence is characterized by a progressive deterioration of the immune system associated with aging. Multiple components of both innate and adaptive immune systems experience aging-related changes, such as alterations in the number of circulating monocytic and dendritic cells, reduced phagocytic activities of neutrophils, limited diversity in B/T cell repertoire, T cell exhaustion or inflation, and chronic production of inflammatory cytokines known as inflammaging. The elderly are less likely to benefit from vaccinations as preventative measures against infectious diseases due to the inability of the immune system to mount a successful defense. Therefore, aging is thought to decrease the efficacy and effectiveness of vaccines, suggesting aging-associated decline in the immunogenicity induced by vaccination. In this review, we discuss aging-associated changes in the innate and adaptive immunity and the impact of immunosenescence on viral infection and immunity. We further explore recent advances in strategies to enhance the immunogenicity of vaccines in the elderly. Better understanding of the molecular mechanisms underlying immunosenescencerelated immune dysfunction will provide a crucial insight into the development of effective elderly-targeted vaccines and immunotherapies.

Adipose-derived stromal stem cells (ASCs) as a new regenerative immediate therapy combating coronavirus (COVID-19)-induced pneumonia

“…Intravenous infusion of MSCs leads in fact to their accumulation in the narrow capillaries of the lungs [41], where their activities playing a significant role in protecting or rejuvenating alveolar epithelial cells, counteracting fibrosis, and improving lung function. MSC infusion would likely be particularly beneficial to elderly individuals infected with SARS-CoV-2, both with and without co-morbidities, as this population is more susceptible to SARS-CoV-2-induced pneumonia, resulting in severe respiratory distress and death because of immune-senescence [42][43][44][45].…”

Inflamm-Aging: Why Older Men Are the Most Susceptible to SARS-Cov-2 Complicated Outcomes

“…The elderly population is the most vulnerable to infection with influenza virus (IFV) and varicella-zoster virus (VZV), two major pathogens that are responsible for the most common infectious diseases worldwide (Oh et al, 2019). The high mortality from seasonal flu affecting the elderly, which most countries address with extensive vaccine campaigns (World Health Organization, 2019), is a consequence of immune senescence, which seems to be the result of lifelong immunogenic stimulation of the immune system by exogenous subclinical infections and endogenous agents (Fulop et al, 2018a).…”

Allo-priming as a universal anti-viral vaccine: protecting elderly from current COVID-19 and any future unknown viral outbreak

“…This suppressed cellular immunity together with the aging of the respiratory organs makes elderly more susceptible to pathological effects of viral infection, especially effects of respiratory viral infection [74]. The immune defects of the elderly make this population less likely to benefit from vaccinations as preventative measures against infectious diseases [75].…”

“…This chronic stimulation causes these memory cells to become exhausted and no longer able to function, contributing to an increased susceptibility of elderly to infectious pathogens [79,80]. The aging immune system is also characterized by a decline in the numbers of naive T cells, an imbalance in Th1/Th2 cell subsets, and a decrease in T cell receptor (TCR) repertoire [75,81,82].…”