Incomplete growth of varicella-zoster virus in human monocytes.

Infection of human peripheral blood monocytes by varicella-zoster virus (VZV) was investigated. When freshly isolated monocytes of young adult volunteers were infected with cell-free VZV and examined by indirect immunofluorescence, specific antigens appeared at 8 hr and the number of antigen-positive cells reached the maximum between 24 and 48 hr postinfection. The proportion of antigen-positive cells to total cells was similar to that of the permissive control (HeLa cells), while very few infectious centers (IC) of monocytes were formed in comparison with the infected control cells. Monocytes isolated from infants and old persons formed a larger number of IC than those of young adults. Electron microscopic study of VZV-infected monocytes from three young adult volunteers demonstrated that the proportion of VZV particle-positive cells to total cells was similar to that of antigen-positive cells, and most of the particles seen in the nuclei were low in density and lacked a central core. These results suggest that the growth of VZV in human adult monocytes is incomplete. This restriction of VZV growth by monocytes may play an important role in defense against VZV infection.