Innovative strategies will be needed to suppress the persistent HIV replication within sequestered reservoirs. This task is especially difficult due to the inaccessibility of reservoirs to pharmacological agents. Therefore, we propose that an optimized `cell-based gene-therapy' approach can be utilized to deliver potent anti-HIV genes. The efficacy of adipose-derived mesenchymal stem cells (ASC) in delivering anti-cancer genes to metastatic tumor sites has been established. However, the utility of ASCs in delivering anti-HIV genes to viral reservoirs has not been previously tested. Since active HIV reservoirs secrete inflammatory cytokines and chemokines, we aim to exploit the intrinsic ability of ASCs to localize to sites of inflammation and deliver a secreted form of HIV fusion inhibitor. Indeed, our preliminary in vitro studies have documented that a subpopulation of ASCs can rapidly migrate towards factors secreted from HIV-infected cells. Therefore, in a humanized mouse model of HIV infection, i.e. HIV-infected huHSC-NSG mice, we first propose to test whether ASCs can seek-out and engraft within HIV reservoirs in vivo. Our preliminary studies also demonstrated that the expression of the secretable HIV fusion inhibitory peptide, i.e. C-46 peptide (SAVE), causes a potent `bystander' anti-HIV effect in vitro. Therefore, we propose test whether ASCs transduced with this SAVE gene can similarly suppress HIV infectivity within HIV reservoirs in our in vivo mouse model. We hypothesize that the use of reservoir-tropic ASCs engineered to express an inducible SAVE peptide will enable sustained suppression of HIV infectivity in sequestered viral reservoirs.
Three Specific Aims will be addressed in this proposal.
In Aim -1, we will determine whether ASCs home to inflammatory microenvironments of the HIV reservoirs in vivo. Furthermore, we aim to investigate whether ASCs, enriched for their reservoir-tropism and migratory phenotype, can be used as optimal gene-delivery vehicles in vivo.
In Aim -2, we aim to first demonstrate that ASCs internalize functional HIV transactivator (Tat) protein. We will construct a Tat-inducible SAVE expression cassette (i-SAVE) and monitor the in vitro anti-HIV efficacy of these i-SAVE transduced ASCs.
Under Aim -3, we propose to demonstrate the reservoir-homing ability of i-SAVE transduced ASCs in vivo and demonstrate their efficacy in sustained suppression of HIV infectivity within reservoirs. An effective strategy to deliver anti-HIV genes to viral reservoirs and an innovative approach to regulate transgene expression only in reservoir-recruited ASCs will overcome the limitations with the current systemic regimen.
Even with highly active antiretroviral therapy (HAART), the persistent HIV replication within reservoirs can facilitate the resurgence of drug resistant virus. Therefore, novel strategies that can suppress productive infection within reservoirs would be of critical importance. We will investigate whether adipose stem cells (ASCs) genetically modified to secrete a HIV entry inhibitor peptide (SAVE) can home to HIV reservoirs in vivo and show sustained suppression of virus propagation in reservoirs. An optimization protocol for this `cell- based gene-therapy' approach will be first tested in vitro and then validated in a HIV-infected humanized mouse model (huHSC-NSG mice). We will determine whether ASCs home to HIV reservoirs in vivo. We will then construct an inducible SAVE expression cassette (i-SAVE) and monitor the reservoir-homing and localized suppression of HIV infectivity in the humanized mouse model. This strategy to target persistent viral reservoirs will overcome the limitations associated with systemic HAART regimen. Ultimately, autologous (patient-derived) ASCs may be used as a `Trojan horse' to deliver multiple potent anti-HIV genes to persistent viral reservoirs, which will be of significant future benefit in patients.
