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Virol Res J 2017 Volume 1 Issue 3
International Virology Conference
October 30-31, 2017 | Toronto, Canada
Novel therapeutics for HIV-1: Small molecule modulators of RNA processing
A Cochrane
1
, R Wong
1
, A Balachandran
1
, L Liu
1
, T Cabral
1
, D Shen
1
and
P Stoilov
2
1
University of Toronto, Canada
2
University of Western Virginia, USA
C
urrent therapeutics is highly successful in blocking disease
progression following HIV-1 infection but the development
of resistance due to the high mutation rate of this virus
remains a constant threat. To explore alternative approaches
of controlling HIV-1 replication that would complement
existing drugs, we are examining the impact of altering
various processes regulating host RNA splicing for their ability
to modulate HIV-1 gene expression. Previously, our group
demonstrated that cardiotonic steroids (digoxin) are potent
inhibitors of HIV-1 replication due to alterations in viral RNA
processing associated with the selective modification of the
host RNA processing factors SRSF3 and Tra2ß. In more recent
work, we demonstrate that the anti-HIV-1 effect of digoxin is
the result of MEK/ERK signaling pathway activation. In support
of the importance of this pathway in regulating HIV-1 RNA
processing, parallel studies identified other activators of this
pathway (anisomycin and a benzoxadiazol-4-amine derivative
designated 191) as potent inhibitors of HIV-1 gene expression.
Like digoxin, 191 induced a marked alteration of HIV-1 RNA
processing (reduced accumulation of unspliced and singly
spliced viral RNAs) as well as loss of Tat and Rev Expression
and changes in SRSF3 and Tra2ß phosphorylation. At doses of
191 sufficient to suppress HIV-1 replication, we observe only
minor changes in host RNA alternative splicing (<30 events
showing >20% alteration in exon inclusion of 9800 events
detected) consistent with HIV-1 having a great sensitivity to
modulation of the host RNA splicing apparatus. Subsequent
tests have confirmed 191’s ability to suppress HIV-1 replication
in the context of PBMCs. Furthermore, 191 are able to inhibit
replication of different HIV-1 clades as well as variants resistant
to existing RT, PR, or IN inhibitors. In parallel with the above
studies, we have also examined the effect of modulating the
activity of other host cell signaling cascades (AKT, PI3K, GSK-3)
for their effects on HIV-1 gene expression. Of these pathways,
only inhibition of GSK-3 with CHIR98014 was found to result in
loss of viral protein expression that correlatedwith reducedHIV-
1 RNA accumulation. CHIR98014 is a potent inhibitor of HIV-1
gene expression in all cell lines tested and is currently being
evaluated for its anti-viral potency in the context of PBMCs.
Current tests have not detected changes in host SR protein
phosphorylation/abundance that correlate with CIHR98014’s
anti-HIV effect. However, shRNA depletion of either GSK-3
α
or ß resulted in a loss of HIV-1 Gag expression confirming the
important role of this signaling pathway in regulatingHIV-1 gene
expression. Together, these findings demonstrate the feasibility
of modulating host RNA processing to generate a state within
the cell unable to support HIV-1 replication.
Speaker Biography
A Cochrane completed his PhD in 1988 from Queen’s University and Post-doctoral
studies from Roche Institute of Molecular Biology. He is a Professor at the University
of Toronto. He has published more than 70 papers and serving on the Editorial Board
of Retrovirology. Over the last several years, his research has been focused on the
regulation of viral RNA processing, with particular focus on the identification of small
molecule modulators of RNA splicing and their utility in the suppression of HIV-1 and
adenovirus replication.
e:
alan.cochrane@utoronto.ca