The Long Shadow of Early HCMV–HIV Coinfection: Epidemiology, Pathogenesis, and Immune Consequences

Human cytomegalovirus (HCMV) and Human Immunodeficiency Virus (HIV) are two pathogens known to have dramatic consequences when contracted early in life. In addition to having a significant impact when acquired individually, these two viruses are known to frequently cause coinfections. Indeed, also in the modern era, HCMV remains one of the most prevalent coinfections in newborns of mothers living with HIV, including both HIV-positive children regardless of their immune status, and those exposed to HIV but uninfected (HEU). In children with HIV infection, HCMV coinfection has historically been associated with AIDS-defining disease, high mortality, and prolonged, elevated HCMV viral load. Although timely administration of antiretroviral therapy prevents immunodeficiency in people living with HIV and thus reduces the incidence of full-blown HCMV disease in cases of coinfection, emerging data suggest that HCMV-induced immune activation and aging persist, potentially contributing to long-term, non-AIDS-related comorbidities. Growing evidence indicates that also HCMV amplifies HIV susceptibility, disease progression, and immune dysregulation through multiple synergistic mechanisms. Moreover, congenital and early postnatal HCMV infections occur at significantly higher rates in HEU newborns than in HIV-unexposed children and are associated with worse clinical outcomes, particularly when HCMV viral loads are high. This review summarizes current knowledge on the epidemiology, clinical impact, and immunopathogenetic interactions of early HCMV–HIV coinfection in pediatric populations. By integrating recent findings with historical evidence, it highlights critical mechanistic and epidemiological gaps that warrant further investigation.