[Structure and assembly of human beta herpesviruses].

This review is concerned with the structure and assembly of HCMV, HHV6 and HHV7. A characteristic ultrastructural feature common to all these viruses is a distinct tegumentary coating of intracytoplasmic capsids. The tegument structure is also distinctly seen in the virions of HHV6 and HHV7. Morphologically, acquisition of the tegument was observed to have taken place in the cytoplasm. Immunoelectron microscopic studies of HCMV infected cells, however, have demonstrated the existence of a tegument protein, pp150, on the surface of intranuclear capsids as well as on capsids in the cytoplasm and in extracellular virions. In addition, another tegument protein, pp65 has been detected within the matrix of cytoplasmic and extracellular dense bodies but not in virions. The molecular mechanism of the assembly of beta herpesviruses was also discussed.