5 th International Workshop on CMV and Immunosenescence ‐ A shadow of cytomegalovirus infection on immunological memory

Human cytomegalovirus (HCMV), a member of the betaherpesvirus family, is an omnipresent pathogen worldwide. Primary HCMV infection elicits robust responses from both the innate and adaptive branches of the immune system. The T-cell response is extraordinary large; on average 10% of the total circulating memory compartment of both the CD4 and CD8 T-cell subsets is specific for HCMV, which makes this virus possibly the most immunogenic microbe for the human immune system. However, despite the extensive immune response, HCMV is not cleared and persists in the host due to its numerous immune evasion mechanisms. Both, primary infection and long-term persistence of HCMV are largely subclinical for the majority of individuals, but HCMV virus is linked to considerable morbidity in immunologically immature and immunocompromised individuals. The role of HCMV infection in immunocompetent hosts has gained considerable interest, and has led to insights that favor a neutral or even beneficial co-existence, but also HCMV-driven detrimental consequences have been reported especially in the elderly. This differential outcome of HCMV infection might be related to the huge variability in the size and phenotype of HCMV-specific T-cell responses among individuals, caused by the differences in infectious dose and the immunocompetence of the host. The interactions between CMV and the immune system were discussed at the 5th International Workshop on CMV and Immunosenescence. Here, we highlight some of the key findings discussed in the meeting, with an emphasis on the particular role of HCMV in memory T-cell formation