HUMAN HEPATOCYTE AND MACROPHAGE CYTOKINE RESPONSES TO YFV-INFECTION

Sara E. Woodson, B.S., M.R. Holbrook, Ph.D.

Department of Pathology and Institute for Human Infection and Immunity, UTMB

Background: Yellow fever virus (YFV) is a mosquito-borne Flavivirus that causes clinical illness ranging from febrile to fatal hemorrhage fever affecting an estimated 200,000 people a year (15-20% mortality rate) with no available therapeutics. Reported data for patients have indicated that certain pro-inflammatory cytokines (such as IL-6) have increased expression between day 0 and 7. Understanding complete pro-and anti-inflammatory cytokine (PIC, AIC) responses is important for understanding the mechanisms of early pathogenesis. Objective: The aim of this study was to examine PIC and AIC production from Asibi and 17-D infected human hepatocytes and macrophages. Methods: PH5CH8 cells, differentiated U-937 cells and primary macrophages were infected with Asibi and 17-D viruses. Supernatant and cell lysates were collected over time and analyzed for cytokine concentrations and gene expression using multi-plexed bead-based assays (Bio-Rad and Panomics). Growth kinetics of the viruses were analyzed by immuno-focus forming assays. Results: Results of these studies indicate that hepatocytes respond to both Asibi and 17-D infection with strong PIC profiles (IL-6, IL-8, IL-1β and RANTES) and minimal increases in AICs (IL-4 and IL-10). Hepatocytes that were infected with 17-D typically responded before (24-36 hrs. p.i.) Asibi infected cells (48-120hrs. p.i.) showing a time lag of when these responses are occurring. Macrophages infected with Asibi virus exhibit a robust PIC (IL-8, RANTES, TNF-α, etc.) response that would indicate polarization to Th1-type downstream responses. Macrophages infected with 17-D virus also showed increased expression of PICs, however the response was not as strong as those infected with Asibi virus. Conclusions: These data are evidence for a dysregulation between production of PICs and AICs that may lead to the hallmark characteristics of YFV infection in the hepatic system: Councilman bodies and midzonal lesions via hepatocyte apoptosis.