Current antiretroviral therapies (ART) are unable to eradicate HIV-1, mainly because the virus persists in latently infected cells that can fuel viral rebound after treatment interruption. Pharmacological reactivation of viral transcription may sensitize viral reservoir cells to immune-mediated killing and reduce the long-term persistence of virus-infected CD4+ T cells. The ACTIVATE study is a prospective, randomized clinical trial in which the histone deacetylase inhibitor panobinostat is administered as a latency-reversing agent in combination with pegylated IFN-?2a as an innate immune modulator to reduce the viral reservoir.
To assess the impact of panobinostat and IFN-a2a on HIV reservoirs, ART-treated participants were randomized to receive panobinostat alone (n=4), the combination of panobinostat and pegIFN-a2a (n=9) or pegIFN-a2a alone (n=4). Proviral HIV-1 DNA was analyzed using the intact proviral DNA assay (IPDA); CD4 T cell-associated HIV-1 RNA was quantified by RT-ddPCR assay. H3 acetylation and innate and adaptive cellular immune responses were analyzed by flow cytometry.
After 4 days of treatment with panobinostat alone or in combination, the proportion of acetylated histone H3-expressing CD4T cells increased by 6.3-fold (MFI increase of 2.6, p<0.0005). In parallel, a significant increase of long-LTR transcripts was observed (fold increase 2.26, p=0.0078) which reflects an increase in viral transcription. However, no significant increases were noted for more elongated HIV-1 RNA transcripts. Proportions of CD4+ and CD8+ T cells expressing granzyme A, granzyme B and perforin as well as the Th1 transcription factor Tbet increased during combined treatment. The expression of co-stimulatory molecules (CD40, CD86, CD83) increased in conventional DC2 and pDCs in participants receiving pegIFN-?2a. Similarly, the frequency of activated CD38+ and NKp30+ cytotoxic NK cells (CD16+ CD56+) increased significantly at day 4 in these participants. Despite reactivation of viral transcription and activation of the immune system after treatment, no changes in HIV-1 DNA levels, determined by IPDA, were observed.
Results from ACTIVATE study indicate that the study medication induces HIV-1 transcription and augments innate and adaptive immune effector cells, without appreciably affecting HIV-1 DNA levels in our current analysis. Further studies will be conducted to evaluate possible changes in proviral positioning relative to activating epigenetic chromatin features.