In Vitro Evidence of Kaposi's Sarcoma Associated Herpesvirus Reactivation by corticosteroids

摘要

Human Herpesvirus 8 (HHV-8) have been detected in all forms of Kaposi's sarcoma [1]. It is also associated to another two neoplasic diseases: Multicentric Castleman's disease (MCD) and primary effusion lymphoma (PEL). Athough many lymphomas may develop cavity effusions, PEL is the only HHV-8 associated body cavity effusion lymphoma with a unique clinical presentation in having a predilection for arising in body cavities such as the pleural space, pericardium, and peritoneum withouth significant adenophaty [2 3]. Cell lines PEL-derived are a well-characterized model for a cancer caused by the expression of a few HHV-8 latent proteins [4, 5-7]. HHV-8 episomes can turn from latent to lytic after the stimuli with phorbol ester 12- O - tetradenoyl phorbol-13 acetate (TPA) enlarging 16 times the amount of virus [8]. PEL cell lines are the source of HHV-8 antigen for making IFA slides which can contain either induced (lytic-IFA) or non induced cells where latent associated nuclear antigen (LANA) can be observed. The use of corticosteroids in transplanted patients increases the occurrence and severity of KS [9]. In vitro, hydrocortisone induces a viral lytic reactivation in BCBL-1 cell line [10]. GOAL: To examine the HHV-8 lytic cycle triggering in BCBL-1 cells after TPA or DEX inductions to produce slides for serological diagnosis. METHODS: BCBL-1 post-induction viability was determined by trypan blue exclusion for six days and compared with non-induced cells. Slides containing either TPA or Dex-induced cells were prepared at 72 hours after induction. Daily viral antigen expression within the cells was examined by IFA using HHV-8 positive pool antisera [11]. In order to investigate the performance of DEX induction for serological diagnosis, 140 serum samples -86 HHV-8 positive and 54 negative- were tested and titered in TPA and DEX slides [12]. Results were analysed by Fisher exact test. RESULTS: TPA had a double citotoxic effect than DEX on the first day and a dramatic rise at 6th day. Fluorescent patterns and number of fluorescent cells were similar in TPA and DEX induced slides. Results for positive and negative HHV-8 serum samples fully matched both slides. In summary, these data show that DEX induces HHV-8 lytic cycle in BCBL-1 cells and it is less cytotoxic than TPA. Thus, the usage of DEX as an inductor is a better option to prepare slides for HHV-8 serologic assays and for in vitro studies.