The immune response to human cytomegalovirus: impact of age, co-morbidities and the significance of anti-viral activity assessment.

Understanding how all the components of the immune system respond to human cytomegalovirus (HCMV) primary infection and subsequent reactivation events is necessary to be able to successfully treat patients suffering from HCMV-mediated disease. In the first part of this review, we overview the humoral response to HCMV, followed by sections on the response of NK cells, CD8+ T cells, CD4+ T cells and the growing field of unconventional T cell subsets to HCMV infection. We then discuss how our knowledge of the CMV-specific immune response can help to inform studies on the effects of HCMV infection in ageing and immunocompromised populations. We discuss how current clinical diagnostic tests relate to the findings from the research field into the functionality of the immune response in different patient cohorts and how the use of direct anti-viral activity in autologous settings could be used to inform intervention strategies with a view to improving patient treatment and outcomes.This article is part of the discussion meeting issue 'The indirect effects of cytomegalovirus infection: mechanisms and consequences'.