Cytomegalovirus and the immune system in old age

A wide range of age-related alterations in immune system function have been reported and are referred to as immunosenescence. Much of the decline in immunoresponsiveness seen in elderly persons is due to changes within the T cell compartment because of the involution of the thymus. For this reason, infectious diseases are more frequent and severe in elderly persons, and the efficacy of vaccinations is low. Recently, scientific evidence has accumulated that chronic cytomegalovirus (CMV) infection may accelerate the aging of the immune system and may lead to a high chronic-inflammatory background in elderly persons. This may exacerbate the functional pathology and disease course of age-related disorders, such as atherosclerosis, rheumatoid arthritis, and Alzheimer's disease. Therefore, the present article will summarize the changes that occur in the immune system of elderly persons with and without chronic CMV infection and will highlight the impact of CMV infection on the immune response and efficacy of vaccinations in old age. It will also elucidate the mechanisms CMV uses to escape immune surveillance, the basis for life-long persistence in the host. Finally, current and future immunotherapeutic strategies to fight or prevent CMV infection will be reviewed.