Vesatolimod (GS-9620) is a Toll Like Receptor 7 (TLR7) agonist that directly activates human pDCs, B lymphocytes, and induces the production of cytokines such as type I interferon. GS-9620 is currently being evaluated in HIV-1 infected participants as part of an HIV remission strategy. Here we investigated the potential of GS-9620 to trigger indirect activation of HIV-specific CD8 T cells, using immune cell cultures derived from HIV+ donors.
Peripheral blood mononuclear cell (PBMC) cultures derived from HIV+ donors virologically suppressed on stable antiretroviral therapy (n=39) were profiled. PBMCs were collected by leukapheresis, separated by Ficoll centrifugation, and treated with GS-9620 (20 and 1000 nM) or vehicle alone for 24 hours. HIV pentamers (Proimmune) composed of five MHC Class I peptide-complexes were used to detect CD8 T cell HIV specificity. Pentamers were selected according to donors’ HLA type(s). Cells were incubated with HIV specific pentamers, surface stained with anti-CD3, CD4, CD8, CD69 fluorescent conjugated antibodies, stained intracellularly with anti-CD107a, TNF-α, and IFN-γ fluorescent conjugated antibodies, and analyzed by flow cytometry (FACS). Donors with GS-9620 activated HIV-specific CD8 T cells were scored as positive using a cut-off of 0.5% Pentamer binding.
In vitro treatment of PBMCs with GS-9620 resulted in all 39 donor cultures demonstrating an increase in CD8+ T cell activation of up to 80% as measured by CD69 expression compared to no treatment. Of these, 17/39 donors showed HIV-specific CD8+ T cell activation with 5/17 donors positive at 20 nM, and 17/17 donors positive at 1000 nM GS-9620. Intracellular staining was done in a subset of donors (n=13), resulting in 4 donors showing HIV-specificity, 2 of which were positive for degranulation (CD107a), 3 positive for TNF-α, and none positive for IFN-γ.
Vesatolimod treatment of HIV+ donor derived PBMCs resulted in robust activation of CD8+ T cells as demonstrated by expression of the activation marker CD69. Furthermore, HIV-specific CD8+ T cell activation was observed in approximately half of the donors tested, with 3 of the donors’ CD8 T cells also up-regulating expression of CD107a and/or TNF- α. These data support the in vivo potential of Vesatolimod to induce HIV-specific CD8 mediated killing of latently infected cells as part of an HIV remission strategy.