Chronic infection of human umbilical vein endothelial cells by human herpesvirus-6

Human herpesvirus-6 (HHV-6) exhibits a predominant tropism for CD4+ T-lymphocytes, but can infect other components of the blood as well as surrounding tissue and organs. To understand the role of the endothelium in the transmission and haematogenous spread of this virus, human umbilical vein endothelial cells (HUVEC) were infected with HHV-6 and monitored for viral gene expression. The presence of both early and late viral antigens was demonstrated by indirect immunofluorescence in 37.6 and 6.5%, respectively, of HUVEC. However, attempts to detect the release of infectious virus were not successful, indicating infection is semipermissive in nature. Upon continued passage of infected HUVEC monolayers, HHV-6 antigen-positive cells persisted up to 27 days post-infection. Furthermore, the virus could be recovered from HUVEC monolayers that contained fewer than 1% antigen-positive cells by co-cultivation with peripheral blood mononuclear cells. Together, these findings suggest that endothelial cells may serve as a reservoir for harbouring HHV-6.