| dc.description.abstract |
<p>Herein we detail the progress made at understanding the overall process of CD8<super>+</super>
T-lymphocyte noncytolytic antiviral response (CNAR). This response is comprised of
3 key components, the virus, the effector cell and the target cell, each of which
contribute to noncytolytic suppression. During the course of CNAR, the effector cells
express antiviral factors that induce intracellular events in the target cell resulting
in host-pathogen interactions that inhibit HIV-1 gene expression. The goal of this
work was to clarify each step of the process of noncytolytic suppression. </p><p>The
effector cell was examined to understand the regulation of antiviral factors and to
construct a profile of the factors expressed during CNAR. CD8<super>+</super> T-lymphocytes
from HIV-1 infected individuals express unidentified factors that suppress viral replication
by inhibiting HIV-1 gene expression. Understanding the regulation of these antiviral
CD8<super>+</super> T cell-derived factors can provide important insights into how
to elicit these factors with therapeutic regimens. For a small subset of human genes,
histone deacetylases (HDACs) are epigenetic regulators that condense chromatin to
repress transcription. We examined the role of epigenetics in modulating the HIV-1
suppressive factors expressed by primary CD8<super>+</super> T cells from subjects
naturally controlling virus replication. HIV-1 suppression by CD8<super>+</super>
T-lymphocytes from virus controllers was reversed up to 40% by the addition of an
HDAC inhibitor. Therefore, histone deacetylation within CD8<super>+</super> T-lymphocytes
was necessary for potent suppression of HIV-1 infection.</p><p>Blocking HDACs impairs
the ability of CD8<super>+</super> T-lymphocytes to repress HIV-1 transcription, demonstrating
the expression of the suppressive factors is regulated by epigenetics. We used this
tool to identify the potential antiviral factors that result in decreased noncytolytic
suppression. Through real-time PCR analysis of 164 genes we identified 4 genes in
primary CD8<super>+</super> T-lymphocytes from a virus controller, and 12 genes in
a CD8<super>+</super> T-cell line that were greatly downregulated in response to a
HDAC inhibitor. Additionally, we analyzed the chemokine and cytokine profile of these
two cell types to characterize what molecules these cells secrete during CNAR. MIP-1
Beta, MIP-1 Alpha, IP-10, and MIG correlated most strongly with the magnitude of CNAR
(<italic>p</italic> < 0.0001). </p><p>The response of the target cell to the antiviral
factors was analyzed to better understand how CD8<super>+</super> T cell antiviral
factors exert suppressive activity on the HIV-1 genome in an infected cell. Noncytolytic
suppression was not dependent on epigenetic changes within the target cells, as HDAC1
within the target cell was dispensable, and histone acetylation at the HIV-1 LTR remained
unchanged in the presence of CD8+ T-lymphocytes. </p><p>The genetic elements within
HIV-1 and the viral protein Tat were investigated to provide insight into resistance
to CNAR. Two virus isolates from the same individual with contrasting sensitivities
to CNAR were investigated to identify the genetic elements that confer these phenotypes.
Sequence analysis of the two isolates identified mutations in the exon splicing silencers
(ESS) 2 and 3 in these viruses. ESS2 and 3 are thought to control splicing of HIV-1
Tat, however levels of spliced Tat RNA levels did not differ between the two isolates.
The introduction of the ESS2 mutation into a heterologous HIV-1 isolate moderately
boosted resistance to CNAR, suggesting a function for the mutation apart from spliced
Tat RNA levels. </p><p>In total, a comprehensive analysis of each component of CNAR
is discussed here to enhance the overall understanding of the mechanisms of CNAR.</p>
|
|
