429. Antibody Delivery by Genetically Engineered Human Hematopoietic Stem Cells to Fight HIV
Authors: Anne-Sophie Kuhlmann, Kevin Haworth, Morgan Giese, Hans-Peter Kiem
Journal: Molecular Therapy (2016)

The fight against HIV (Human Immunodeficiency Virus) has made considerable progress following antiretroviral therapy development. However, a cure has not been achieved yet due to the existence of replication-competent latent viral reservoirs in sanctuaries such as the Gut-Associated Lymphoid Tissue, lymph nodes or central nervous system. The elimination of these reservoirs appears as a key to eradicate HIV, and developing innovative delivery methods will be critical to reach this goal. Hematopoietic stem cells (HSCs) and derived lineages have been shown to migrate to these sanctuaries and represent a powerful way of delivering therapeutic molecules to target HIV. The recent identification of potent broadly neutralizing antibodies (bNAbs) directed against the Envelope of HIV holds new prospects. In addition to neutralizing various strains of HIV, a few reports have shown the ability of these antibodies to target HIV originating from the latent reservoirs. Recent efforts have focused on bNAbs delivery, but their in vivo half-life remains limited. Delivery by HSCs would provide a durable alternative. Based on these observations, we are genetically modifying CD34+ hematopoietic stem and progenitor cells (HSPCs) to give them the ability to express and secrete potent bNAbs targeting both circulating viral particles and latent viral reservoirs. To this end, cell lines or human HSPCs were transduced by lentiviral constructs encoding selected bNAbs and assessed for their ability to secrete functional antibodies. In vitro, 293T cells were able to release the bNAbs of interest in the supernatants at 4 and 7 days post-transduction. The secreted antibodies were also detected in modified human HSPCs supernatants starting at 9 days and for up to 21 days post-transduction. To assess the antibodies protective effect against HIV in vivo, we have utilized the NOD-SCID-gamma (NSG) mouse model. A single infusion of genetically modified HSPCs in this model allows for immune cell development and subsequent HIV challenge. Circulating human cells are detected in the peripheral blood as early as 8 weeks post-engraftment. Mice have now been challenged with HIV at 12 weeks and the infection is being tracked using quantitative PCR. This model will allow us to determine the ability of genetically modified HSPCs to secrete these bNAbs in vivo and prevent HIV infection as well as to track antibodies delivery to isolated sanctuaries such as the brain. The long-term secretion potency of these modified HSPCs and derived lineages will also be investigated. Here we show the development of an alternative delivery method for antibodies by genetically modified HSPCs. The ability of HSPCs to differentiate into multiple hematopoietic lineages and thus to cross physiological and anatomical barriers represents a valuable asset to target HIV latent viral reservoirs. Another advantage provided by the use of HSPCs is their long-term persistence that should support a long-term secretion and thus treatment. Future development will focus on controlling antibody expression. Importantly, this strategy could be applied to a broad variety of diseases for which antibodies have been shown to be efficient in patients, but require multiple injections for sustainable efficiency.