Human cytomegalovirus latency alters the cellular secretome, inducing cluster of differentiation (CD)4+ T-cell migration and suppression of effector function

After primary infection, human cytomegalovirus (HCMV) persists as a life-long latent infection, with host immunosuppression often resulting in clinical reactivation. During lytic infection, major changes in the expression of secreted cellular proteins (the secretome) occur that have profound effects on host–cell interactions, particularly at the level of the host immune response. In contrast, little is known about changes in the secretome that accompany latent infection, yet this is likely to be of major importance for the life-long carriage of this persistent human pathogen in the face of constant immunosurveillance. We have analyzed the secretome of cells carrying latent HCMV and have identified changes in several secreted cellular proteins known to be involved in regulation of the immune response and chemoattraction. Here, we show that a latency-associated increase in CC chemokine ligand (CCL)8 results in the recruitment of cluster of differentiation (CD)4⁺ T cells to supernatants from latently infected CD34⁺ cells but that these latent supernatants, also rich in immunosuppressive factors, inhibit cytokine secretion and cytotoxicity of HCMV-specific T-helper (Th)1 CD4⁺ T cells. These results identify a strategy by which sites of latent HCMV can firstly recruit CD4⁺ T cells and then inhibit their antiviral effector functions, thereby aiding the maintenance of latent infection in the face of the host immune response.