CD4 and disease arising from reactivation of latent virus: Following our previous discovery of CMV-specific CD4 + T cells secreting IL-10 in response to two proteins associated with latent infection, UL138 and LUNA [22], and the evidence that there are suppressive and T regulatory cells present in CMV infection, we hypothesised that lifelong carriage of HCMV infection could create an environment where IL-10 secretion was increased by skewing the CD4 + T cell viral response towards a more suppressive phenotype.