Lentiviral vectors with high surface content of CD47 improved gene transfer efficiency to hepatocytes in nonhuman primates.

Lentiviral vectors (LV) are powerful and versatile vehicles for gene therapy. However, their complex biological composition challenges large‐scale manufacturing and raises concerns for in vivo applications, because particle components and contaminants may trigger immune responses. Here, we show that producer cell‐derived polymorphic class‐I major histocompatibility complexes (MHC‐I) are incorporated into the LV surface and trigger allogeneic T‐cell responses. By disrupting the beta‐2 microglobulin gene in producer cells, we obtained MHC‐free LV with substantially reduced immunogenicity. We introduce this targeted editing into a novel stable LV packaging cell line, carrying single‐copy inducible vector components, which can be reproducibly converted into high‐yield LV producers upon site‐specific integration of the LV genome of interest. These LV efficiently transfer genes into relevant targets and are more resistant to complement‐mediated inactivation, because of reduced content of the vesicular stomatitis virus envelope glycoprotein G compared to vectors produced by transient transfection. Altogether, these advances support scalable manufacturing of alloantigen‐free LV with higher purity and increased complement resistance that are better suited for in vivo gene therapy. Synopsis Lentiviral vectors (LV) lacking major histocompatibility complexes (MHC) and with low vesicular stomatitis virus glycoprotein G (VSV.G) content escape immune recognition by human T cells and complement. Cell line‐packaged LV offer scalable and consistent LV production for in vivo gene therapy. Site‐specific integration of the LV genome into an inducible packaging cell line allows consistent generation of high‐yield producers of the LV of interest. Cell line‐produced LV achieve equivalent gene transfer in the mouse liver as LV produced by conventional transfection but are more stable in human sera, due to a lower VSV.G content. Genetic inactivation of beta‐2 microglobulin (B2M) in LV producer cells allows production of MHC‐free LV with preserved infectivity, devoid of immunogenic alloantigens in human recipients.

Liver gene therapy with adeno-associated viral (AAV) vectors delivering clotting factor transgenes into hepatocytes has shown multiyear therapeutic benefit in adults with hemophilia. However, the mostly episomal nature of AAV vectors challenges their application to young pediatric patients. We developed lentiviral vectors, which integrate in the host cell genome, that achieve efficient liver gene transfer in mice, dogs and non-human primates, by intravenous delivery. Here we first compare engineered coagulation factor VIII transgenes and show that codon-usage optimization improved expression 10-20-fold in hemophilia A mice and that inclusion of an unstructured XTEN peptide, known to increase the half-life of the payload protein, provided an additional >10-fold increase in overall factor VIII output in mice and non-human primates. Stable nearly life-long normal and above-normal factor VIII activity was achieved in hemophilia A mouse models. Overall, we show long-term factor VIII activity and restoration of hemostasis, by lentiviral gene therapy to hemophilia A mice and normal-range factor VIII activity in non-human primate, paving the way for potential clinical application.

Prions are infectious proteins that are responsible for transmissible spongiform encephalopathies (TSEs) and consist primarily of scrapie prion protein (PrPSc), a pathogenic isoform of the host-encoded cellular prion protein (PrPC). The absence of nucleic acids as essential components of the infectious prions is the most striking feature associated to these diseases. Additionally, different prion strains have been isolated from animal diseases despite the lack of DNA or RNA molecules. Mounting evidence suggests that prion-strain-specific features segregate with different PrPSc conformational and aggregation states. Strains are of practical relevance in prion diseases as they can drastically differ in many aspects, such as incubation period, PrPSc biochemical profile (e.g., electrophoretic mobility and glycoform ratio) and distribution of brain lesions. Importantly, such different features are maintained after inoculation of a prion strain into genetically identical hosts and are relatively stable across s...

Lentiviral vector (LV)-mediated ex vivo gene therapy for haematopoietic stem and progenitor cells (HSPCs) has delivered on the promise of a ‘one-and-done’ treatment for several genetic diseases¹. However, ex vivo manipulation and patient conditioning before transplantation are major hurdles that could be overcome by an in vivo approach. Here we demonstrate that in vivo gene delivery to HSPCs after systemic LV administration is enabled by the substantial trafficking of these cells from the liver to the bone marrow in newborn mice. We improved gene-transfer efficiency using a phagocytosis-shielded LV, successfully reaching bona fide HSPCs capable of long-term multilineage output and engraftment after serial transplantation, as confirmed by clonal tracking. HSPC mobilization further increased gene transfer, extending the window of intervention, although permissiveness to LV transduction declined with age. We successfully tested this in vivo strategy in mouse models of adenosine deaminase deficiency, autosomal recessive osteopetrosis and Fanconi anaemia. Interestingly, in vivo gene transfer provided a selective advantage to corrected HSPCs in Fanconi anaemia, leading to near-complete haematopoietic reconstitution and prevention of bone marrow failure. Given that circulating HSPCs in humans are also most abundant shortly after birth, in vivo HSPC gene transfer holds strong translational potential across multiple diseases.

Lentiviral vectors (LV) are efficient vehicles for in vivo gene delivery to the liver. LV integration into the chromatin of target cells ensures their transmission upon proliferation, thus allowing potentially life-long gene therapy following a single administration, even to young individuals. The glycoprotein of the vesicular stomatitis virus (VSV.G) is widely used to pseudotype LV, as it confers broad tropism and high stability. The baculovirus-derived GP64 envelope protein has been proposed as an alternative for in vivo liver-directed gene therapy. Here, we perform a detailed comparison of VSV.G- and GP64-pseudotyped LV in vitro and in vivo. We report that VSV.G-LV transduced hepatocytes better than GP64-LV, however the latter showed improved transduction of liver sinusoidal endothelial cells (LSEC). Combining GP64-pseudotyping with the high surface content of the phagocytosis inhibitor CD47 further enhanced LSEC transduction. Coagulation factor VIII (FVIII), the gene mutated in hemophilia A, is naturally expressed by LSEC, thus we exploited GP64-LV to deliver a FVIII transgene under the control of the endogenous FVIII promoter and achieved therapeutic amounts of FVIII and correction of hemophilia A mice.