BACKGROUND: Autologous cell transplant approaches for HIV cure typically involve re-infusion of a person’s own gene-modified hematopoietic stem and/or T cells. However, poor post-infusion engraftment of the gene-modified cells remains a major hurdle for achieving successful control of HIV-1 viral loads and ART-free remission. In vivo gene therapy, which does not involve ex-vivo cell manipulations, may address this issue. That said, effective transgene delivery to human hematopoietic cells in vivo is a formidable challenge in the gene therapy field.
METHODS: We exploited the dominant surface expression of CD7 on human T cells and monocytes to allow targeted and effective transduction of these cell types with virus-like particles (VLPs) surface-decorated with a humanized antibody to human CD7. Importantly, as a key step toward clinical application, we adapted this platform for the delivery of genome-integrating ORFs encoding short-hairpin RNA (long-term expression) and/or ‘scarless’ delivery of packaged CRISPR ribonucleoprotein complexes (RNPs, transient expression). The platform was tested for abrogating expression of HIV-1 host dependency factors in human T cells in humanized mouse models of HIV-1 infection after systemic (intravenous) administration.
RESULTS: Simple intravenous injection of CD7 antibody-guided VLPs into humanized mice resulted in selective transduction of primary human T cells (and monocytes) with negligible off-targeting and hepatotoxicity. We obtained impressive in vivo gene marking frequencies of > 50% of human T cells. Gene-marked CD4 T cells selectively expanded in HIV-1_JRCSF-infected humanized mice after withdrawal of antiretroviral therapy (ART) resulting in control of plasma viral loads and stabilization of CD4 T cell levels. Importantly, treated mice were resistant to repeated challenge with HIV-1. ART-free control of viral loads was also achieved humanized mice transplanted with CD4 T cells from people living with HIV (PLWH) demonstrating potential applicability as a cure strategy for HIV-1.
CONCLUSIONS: The approach we report here represents an important advance to the field of gene therapy-based cure for HIV in that it obviates the need for cell transplant protocols with ex-vivo transduced hematopoietic cells. We expect our work to be a significant advance towards achieving ART-free remission and of compelling interest to the fields of clinical gene-therapy for HIV-1 and other diseases.