Hydrocortisone activation of human herpesvirus 8 viral DNA replication and gene expression in vitro.

Background, Patients undergoing chronic steroid therapy for organ transplantation are at increased risk for development of human herpes virus 8(HHV-8)associated Kaposi's sarcoma (KS), It has also keen reported that following steroid withdrawal, KS lesions often undergo partial or complete regression. Methods. We have examined the effect of corticosteroid treatment on HHV-8 replication, gene expression, and lytic protein expression in BCBL-1 cells in vitro. BCBL-1 cells were collected after culture for 24-72 hr with hydrocortisone (HC) 1-5 mu M, phorbol ester 20 ng/ml (positive control), and culture medium only (negative control). HHV-8 genomic conformation was examined by Gardella gel analysis. mRNA expression of viral cyclin (v-Cyc), viral Bcl-2 (v-Bcl-2), viral macrophage inflammatory protein-I (v-MIP-I), viral interferon regulatory factor-1 (v-IRF-1), and viral tegument protein (TP) was examined by RT-PCR Southern blot, Viral protein expression within the cells was examined by indirect immunofluorescence using 5 different HHV-8 positive antisera from 4 renal transplant recipients and 1 patient with classic KS. Results. Gardella gel analysis revealed that HC induced an accumulation of the linear replicative genomic form of the virus in a time-dependent fashion. Southern blot analysis of the RT-PCR products revealed that HC induced increased expression of v-IRF-1, v-Bcl-2, and TP mRNA, with little discernible effect on v-Cyc, and V-MIP-I, Immunofluorescence revealed that HC induced increased numbers of cells expressing lytic antigens, Conclusions. These data indicate that hydrocortisone acts directly on BCBL-1 cells to activate the lytic cycle of HHV-8 and provide further support for the hypothesis that HHV-8 is activated in corticosteroid-treated immunocompromised patients.