Viral and Cell Type Specific Host Factors that Contribute to Paramyxovirus Antiviral Responses

Activation of host cell responses during viral infection can be a critical factor in determining of viral tropism, dissemination, and pathogenesis. The paramyxovirus simian virus 5 (SV5) is able to establish highly productive, persistent infections of cultured epithelial cells with minimal induction of host cell responses. In contrast, two SV5 mutants induce production of proinflammatory cytokines, type I interferon, and cytopathic effects. The SV5 mutant, Le-(U5C,A14G), contains naturally occurring nucleotide substitutions in a highly conserved region of the viral promoter. The Le mutant demonstrated no defect in growth, in fact the rate of viral protein expression was ~2 fold higher than that seen in WT SV5 infection. Despite expression of a functional viral V protein antagonist, the Le mutant induced IL-6 and IFN-β secretion. Mild CPE involving formation of syncytia was also observed during Le mutant infection, which correlates with increased expression of the active form of the viral F protein. A second SV5 mutant, P/V-CPI-, has also been previously demonstrated to overexpress viral genes and potently induce cytokines and CPE following infection. Analysis of host cell pathways by the use of siRNA knockdown demonstrated that cytokine secretion induced by both the Le and P/V mutants was dependent on production of dsRNA and RIG-I, an RNA sensing PRR. Overexpression experiments demonstrated that cytokine induction did not involve TLR3. However, IL-8 secretion was enhanced when mutant virus infected cells were challenged with a TLR3 agonist. We demonstrated that stimulation of TLR3 through addition of exogenous dsRNA caused a drastic increase in the level of RIG-I protein. Through the use of dominant negative versions of RIG-I and TRIF, a model is supported whereby TLR3 stimulation upregulates RIG-I expression, which in turn hypersensitizes cells to RIG-I mediated cytokine induction by SV5 mutants. By contrast to infection in epithelial cells, WT SV5 was found to be a potent inducer of type I IFN secretion in plasmacytoid dendritic cells. IFN-α secretion occurred in a replication-independent manner and was decreased by a TLR7 inhibitor. Taken together this work supports a model in which the induction of host cell responses during viral infection are influenced by three factors, i) the level of viral inducer, ii) the pathways targeted by the viral antagonist, and iii) the type and level of PRR expressed in a given cell type.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2010

Author dc:creator

• Manuse, Mary

• virology

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10339/14847

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/14847