The impact of inflationary cytomegalovirus‐specific memory T cells on anti‐tumour immune responses in patients with cancer

Human cytomegalovirus (CMV) is a ubiquitous, persistent beta herpesvirus. CMV infection contributes to the accumulation of functional antigen‐specific CD8(+) T‐cell pools with an effector‐memory phenotype and enrichment of these immune cells in peripheral organs. We review here this ‘memory T‐cell inflation’ phenomenon and associated factors including age and sex. ‘Collateral damage’ due to CMV‐directed immune reactivity may occur in later stages of life – arising from CMV‐specific immune responses that were beneficial in earlier life. CMV may be considered an age‐dependent immunomodulator and a double‐edged sword in editing anti‐tumour immune responses. Emerging evidence suggests that CMV is highly prevalent in patients with a variety of cancers, particularly glioblastoma. A better understanding of CMV‐associated immune responses and its implications for immune senescence, especially in patients with cancer, may aid in the design of more clinically relevant and tailored, personalized treatment regimens. ‘Memory T‐cell inflation’ could be applied in vaccine development strategies to enrich for immune reactivity where long‐term immunological memory is needed, e.g. in long‐term immune memory formation directed against transformed cells.