Abstract

Polyomavirus-associated nephropathy (PVAN) is a significant
complication after kidney transplantation, often leading to
premature graft loss. In order to identify antiviral responses
of the renal tubular epithelium, we studied activation of the
viral DNA and the double-stranded RNA (dsRNA) sensors
Toll-like receptor 3 (TLR3) and retinoic acid inducible gene-I
(RIG-I) in allograft biopsy samples of patients with PVAN, and
in human collecting duct cells in culture after stimulation
by the dsRNA mimic polyriboinosinic:polyribocytidylic acid
(poly(I:C)), cytokines, or infection with BK virus. Double
staining using immunofluorescence for BK virus and TLR3
showed strong signals in epithelial cells of distal cortical
tubules and the collecting duct. In biopsies microdissected to
isolate tubulointerstitial lesions, TLR3 but not RIG-I mRNA
expression was found to be increased in PVAN. Collecting
duct cells in culture expressed TLR3 intracellularly, and
activation of TLR3 and RIG-I by poly(I:C) enhanced expression
of cytokine, chemokine, and IFN-b mRNA. This inflammatory
response could be specifically blocked by siRNA to TLR3.
Finally, infection of the collecting duct cells with BK virus
enhanced the expression of cytokines and chemokines. This
led to an efficient antiviral immune response with TLR3 and
RIG-I upregulation without activation of IL-1b or components
of the inflammasome pathway. Thus, PVAN activation of
innate immune defense mechanisms through TLR3 is involved
in the antiviral and anti-inflammatory response leading to the
expression of proinflammatory cytokines and chemokines.