Dept. of Molecular Microbiology and Immunology
Oregon Health & Science University
Kaposiâs Sarcoma-associated herpesvirus (KSHV) and rhesus macaque rhadinovirus (RRV), two closely related Î³-herpesviruses, are unique in their acquisition and expression of a cluster of genes with significant homology to cellular interferon (IFN) regulatory factors (IRFs). Initial studies of KSHV vIRFs demonstrated their varied function in immune evasion and tumorigenesis. However, inadequate models for studying de novo KSHV infection, as well as KSHV-associated diseases, makes RRV the most acceptable alternative for evaluating the role(s) of vIRFs during de novo infection, and in the development of disease. We have generated and characterized a vIRF deletion virus, vIRF-ko RRV, with all eight vIRFs deleted (ORFs R6-R13), using the bacterial artificial chromosome (BAC) clone of RRV17577. In vitro analyses demonstrated that vIRF-ko RRV infection resulted in increased induction of type I and type II IFN during de novo RRV infection, which correlated with a significant increase in the nuclear accumulation of cellular IRF-3, necessary for driving transcription of type I IFN. Furthermore, vIRFko RRV infection of rhesus macaques results in undetectable viral loads, increased Th1 cytokine production and earlier T cell responses, as well as diminished B cell hyperplasia, a defining characteristic of RRV infection. Further in vitro analyses of individual RRV vIRF clones demonstrated that expression of R6 vIRF significantly inhibited transcription mediated by cellular IRF-3, as well as type I IFN. Moreover, R6 vIRF specifically binds to cellular IRF-3, which may explain the IRF-3 dysregulation and inhibition of type I IFN observed during RRV infection. Additionally, three other vIRFs (ORFs R7, R8, and R9) demonstrated transforming capacity in vitro, suggesting each vIRF has a potentially unique and varied role in immune evasion and pathogenesis. Overall, our findings demonstrate the significant inhibitory role vIRFs have on the IFN response, as well as their wide-ranging impact during RRV infection in the rhesus macaque. If these data can be extrapolated to KSHV-associated disease, our findings would suggest that targeting vIRFs could be a potential therapeutic option to enhance immune responses and inhibit B cell proliferation before malignancies develop.
School of Medicine
Robinson, Bridget A., "Viral interferon regulatory factors inhibit the immune response following rhesus rhadinovirus infection" (2011). Scholar Archive. 670.