The differential short- and long-term effects of HIV-1 latency-reversing agents on T cell function.

Despite the extraordinary success of HIV-1 antiretroviral therapy in prolonging life, infected individuals face lifelong therapy because of a reservoir of latently-infected cells that harbor replication competent virus. Recently, compounds have been identified that can reverse HIV-1 latency in vivo. These latency- reversing agents (LRAs) could make latently-infected cells vulnerable to clearance by immune cells, including cytolytic CD8+ T cells. We investigated the effects of two leading LRA classes on CD8+ T cell phenotype and function: the histone deacetylase inhibitors (HDACis) and protein kinase C modulators (PKCms). We observed that relative to HDACis, the PKCms induced much stronger T cell activation coupled with non-specific cytokine production and T cell proliferation. When examining antigen-specific CD8+ T cell function, all the LRAs except the HDACi Vorinostat reduced, but did not abolish, one or more measurements of CD8+ T cell function. Importantly, the extent and timing of these effects differed between LRAs. Panobinostat had detrimental effects within 10 hours of drug treatment, whereas the effects of the other LRAs were observed between 48 hours and 5 days. These observations suggest that scheduling of LRA and CD8+ T cell immunotherapy regimens may be critical for optimal clearance of the HIV-1 reservoir.

Pharmacodynamic analysis of a serine protease inhibitor, MK-4519, against hepatitis C virus using a novel in vitro pharmacodynamic system.

The development of new antiviral compounds active against hepatitis C virus (HCV) has surged in recent years. In order for these new compounds to be efficacious in humans, optimal dosage regimens for each compound must be elucidated. We have developed a novel in vitro pharmacokinetic/pharmacodynamic system, the BelloCell system, to identify optimal dosage regimens for anti-HCV compounds. In these experiments, genotype 1b HCV replicon-bearing cells (2209-23 cells) were inoculated onto carrier flakes in BelloCell bottles and treated with MK-4519, a serine protease inhibitor. Our dose-ranging studies illustrated that MK-4519 inhibited replicon replication in a dose-dependent manner, yielding a 50% effective concentration (EC(50)) of 1.8 nM. Dose-fractionation studies showed that shorter dosing intervals resulted in greater replicon suppression, indicating that the time that the concentration is greater than the EC(50) is the pharmacodynamic parameter for MK-4519 linked with inhibition of replicon replication. Mutations associated with resistance to serine protease inhibitors were detected in replicons harvested from all treatment arms. These data suggest that MK-4519 is highly active against genotype 1b HCV, but monotherapy is not sufficient to prevent the amplification of resistant replicons. In summary, our findings show that the BelloCell system is a useful and clinically relevant tool for predicting optimal dosage regimens for anti-HCV compounds.