Human cytomegalovirus cell tropism and pathogenesis

The human cytomegalovirus (HCMV) can cause lifelong infection with episodes of endogenous reactivation. Intrauterine fetal infection and infection of immunocompromised patients are well known to result in significant morbidity. Studies on HCMV cell tropism in vivo revealed three characteristics: (1) ubiquitously distributed cell types such as epithelial cells, endothelial cells and fibroblasts are the major targets of HCMV infection; (2) leukocytes circulating in the peripheral blood are susceptible to the virus, and (3) specialized parenchymal cells such as smooth muscle cells in the gastrointestinal tract and hepatocytes can also be infected. Questions to be resolved are, how the virus spreads throughout the organism, how it can impair the function of infected organs, and how it evades the host's immune response to establish lifelong infection. This chapter is focused on the role of HCMV-infected target cells for the pathogenesis of HCMV-associated disease in the acutely infected immunocompromised host.