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

Background, Patients undergoing chronic steroid therapy for organ transplan tation 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 r eplication, gene expression, and lytic protein expression in BCBL-1 cells i n vitro. BCBL-1 cells were collected after culture for 24-72 hr with hydroc ortisone (HC) 1-5 mu M, phorbol ester 20 ng/ml (positive control), and cult ure medium only (negative control). HHV-8 genomic conformation was examined by Gardella gel analysis. mRNA expression of viral cyclin (v-Cyc), viral B cl-2 (v-Bcl-2), viral macrophage inflammatory protein-I (v-MIP-I), viral in terferon regulatory factor-1 (v-IRF-1), and viral tegument protein (TP) was examined by RT-PCR Southern blot, Viral protein expression within the cell s was examined by indirect immunofluorescence using 5 different HHV-8 posit ive 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 fashio n. Southern blot analysis of the RT-PCR products revealed that HC induced i ncreased expression of v-IRF-1, v-Bcl-2, and TP mRNA, with little discernib le effect on v-Cyc, and V-MIP-I, Immunofluorescence revealed that HC induce d 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 fo r the hypothesis that HHV-8 is activated in corticosteroid-treated immunoco mpromised patients.