An ideal strategy for viral purging
would induce HIV-1 expression without
inducing a global T-cell activation. Therefore, small molecules that can directly
gain access to DNA and facilitate viral
gene expression can circumvent the limitations of cell surface receptor activation.
Clearly, HDAC inhibitors meet these criteria. In general, HDAC inhibitors are safe,
orally active and used widely in medicine. In HIV-1 latency, maintaining histones in their deacetylated form by
HDACs results in densely packed chromatin in the nucleosome with gene expression quiescent. On the other hand,
hyperacetylation of specific lysine
residues within nucleosomal histones disrupts chromatin binding and allows transcriptional activation of genes. Thus,
adding HDAC inhibitors to cell lines with
integrated HIV-1 resulted in expression of
HIV-1 without any costimulation of cytokines. Table 1 lists some of the reports
on HDAC inhibition in vitro from cell
lines with integrated HIV-1. The human
macrophage cell line U1, which is derived
from the U937 line, served as the model
for a latent virus in macrophages,
whereas Ach2 cells were used as the
model for integrated HIV-1 in T cells.