Morphogenesis of HHV8 in primary human dermal microvascular endothelium and primary effusion lymphomas

This study elucidates the morphology of HHV8 replication in human dermal en dothelial cells and primary effusion lymphomas (PEL) and compares it to tha t seen in Kaposi sarcoma. Primary human dermal microvascular endothelial ce lls (DMVEC) exposed to the cell-filtered supernatant of the PEL JSC1 and PE L cell lines (KS-1, BCBL-1, BC-1, BC-3) were cultured in the presence or ab sence of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or butyrate. Cells wer e fixed in neutral-buffered glutaraldehyde, gelled in cooled agar, and proc essed for TEM. There was a quantitative, but not a qualitative difference i n Viral expression associated with no treatment or exposure to TPA or butyr ate of HHV8 in DMVEC and PEL. Two types of viral-induced intranuclear inclu sions (INI) were visible at the light and ultrastructural levels. The more common INI had lighter staining material filling the nucleus, except for a rim of dense chromatin, and could be seen even before viral nucleocapsids ( NC) were visible. The second type of INI resembled a target formed by conde nsation of electron-dense material surrounded by a lighter halo and margina ted heterochromatin and containing NC. Collections of coalescing electron-d ense granules resembling starbursts were often present in nuclei containing either type of INI. Next to appear in productively infected cells were mat ure enveloped particles that formed mostly by the budding of NC into cytopl asmic vacuoles. Mature particles were also seen free on the plasma membrane . Tufts of electron-dense intermediate filaments were associated with matur ing particles. Mature virions lacked an electron-dense tegument. Viral prod uction was ultimately associated with cell lysis. It appears that HHV8 prop agate in DMVEC. with and without stimulation, and have a similar morphogene sis to that seen in PEL cell lines and Kaposi sarcoma lesions. Several uniq ue features characterize cells productively infected by HHV8.