The role of immune reconstitution in cytomegalovirus infection

Cytomegalovirus (CMV) causes high morbidity and mortality in immunocompromised patients. The host immune response to CMV comprises specific and nonspecific cellular and humoral responses, but current knowledge supports a protective role only for cell-mediated immune responses. Although complete CMV eradication is unusual even in immunocompetent hosts, its morbidity can be limited by CMV-specific CD8+ cytotoxic lymphocytes supported by CD4+-mediated T lymphocyte helper activity. In patients with congenital or acquired deficiencies of cell-mediated immunity, recovery of CD4+ lymphocyte numbers and/or function coincides with cessation of CMV-associated morbidity. However, an immunological test that can predict protection against CMV disease across different types of high-risk patients is not yet available. In recent years, the introduction of antivirals active against CMV has improved the outcome of CMV disease. In addition, there is a continuous effort to develop CMV-specific immune-based therapies including vaccines and immune modulators such as cytokines, which may be of supplemental benefit in the control of CMV disease.