Collaborative Project #3: Modeling HIV rebound role of SIVMAC251 functional reservoirs and biomarkers of reactivation
Collaborating Investigator: Robert Siliciano
Affiliation: Professor of Medicine Investigator, HHMI Member NAS Johns Hopkins SOM
Funding source: NIH
Project period: 06/23/17-05/31/22
Certain HIV-infected individuals, known as “elite suppressors,” are able to maintain undetectable viral loads without antiretroviral therapy. In effect, their immune responses to the virus induce a functional cure. Current efforts in HIV research seek to develop vaccines that can achieve this same kind of functional cure in all patients. One promising strategy recently reported in macaques has been to induce an effector memory CD8+ T cell response against SIV by using a Rhesus CMV (RhCMV) vector to deliver SIV proteins. To attempt to bypass the need to infect patients with CMV in order to achieve the effects of the RhCMV-SIV vaccine, we plan to expand non-canonically-restricted CD8+ T cells from the blood of healthy donors using artificial APCs (aAPCs). We will then test whether the HLA-E and Class II-restricted CD8+ Tcells are protective against HIV and if they can kill virally-infected targets.
The central hypothesis of this CP is that most individuals harbor small populations of naïve CD8+ T cells that recognize particular SIV peptide epitopes presented by MHC-E or MHC Class II molecules.If this is true, then we should be able to recover these non-canonically-restricted CD8+ T cells in healthy donors using a strategy designed to enrich and expand rare populations of naïve T cells.
Aim 1: Enrich and expand CD8+ T cells specific for known peptides presented by (1.1) human HLA-E and(1.2) MHC II that have been shown to elicit protective responses in macaques after immunization with the RhCMV-SIV vaccine.
Aim 2: Test the ability of non-canonically-restricted CD8+ T cells retrieved from Aim 1 to kill target CD4+ Tcells infected with laboratory strains of replication-competent HIV. Approach: Aim 1 will use the nano a APC enrichment and expansion (E&E) platform to detect non-canonical CD8+T cells. First, TR&D1 will generate HLA E-Ig dimers to develop HLA-E-based nano aAPCs which will be conjugated to particular “cognate”pMHCs of these non-canonical T cells (Hansen et. al, Science2016). Since this peptide can be presented by human HLA-E, we will look in healthy human blood for evidence of CD8+ T cells specific for this pMHC sequence using aAPCs as described above. After enrichment, we will expand the enriched population for 1-2weeks with magnetic beads conjugated to both the cognate tetramer (signal 1) and CD28 (signal 2). In Aim2, we will test the ability of these cells to kill target CD4+ T cells infected with replication-competent HIV using CD4+/ CD8+ T cell co-culture experiments. Our preliminary data shows that ~90% CD4+ T cells express HLA-E and that therefore non-canonically restricted CD8+ T cells may kill target cells presenting these molecules. If these data are seen with RMYNPTNIL-specific CD8+ T cells, we will apply this strategy to other Gag peptides. The end goal is to develop a combinatorial panel of non-canonically-restricted CD8+ T cells to mimic the breadth of the response elicited by the RhCMV-SIV vaccine, without the safety concern of using CMV as a vaccine vector.
While the Schneck lab has extensively used their approach for expansion of classic Class I-restricted CD8+ T cells, they have not targeted novel HIV-specific T cell populations. We expect that this will be a very dynamic push-pull collaborative relationship helping us understand how to best use nano-aAPC and E+E for expansion of unique HIV-specific T cells. The push-pull relationship may also entail using the different Signal 2 complexes and different ligand densities as discussed in TR&D1 and comparing them to standard anti-CD28 based nano-APC