Correction of bleeding diathesis without liver toxicity using arenaviral-pseudotyped HIV-1-based vectors in hemophilia A mice.

Hemophilia A is an inheritable X-linked bleeding disorder most frequently occurring as a consequence of genetic alterations within the factor VIII (FVIII) gene. In the present study, pseudotyped human immunodeficiency virus type 1 (HIV-1)-derived lentivectors expressing hFVIII were assessed for the ability to correct the hemophilia A phenotype in FVIII knockout mice. Therapeutic levels of plasma hFVIII (1-7 ng/mL) were detected in C57B1/6 mice (4-5 weeks old) after portal vein administration of hFVIII-expressing lentivectors pseudotyped with the rhabdoviral vesicular stomatitis viral G protein (VSV-G). More importantly, transduction of hemophilia A mice with FVIII expressing lentivectors resulted in transient correction of the bleeding diathesis phenotype. Moreover, the use of alternate viral pseudotypes based on the lymphocytic choriomeningitis virus (LCMV) resulted in similar circulating levels of FVIII. Interestingly, similar doses of LCMV-pseudotyped lentiviral vectors resulted in minimal systemic or hepatic injury as measured by plasma alanine transferase (ALT), aspartate transferase (AST), and tumor necrosis factor (TNF)-alpha compared to the more commonly used envelope, VSV-G. In summary, these studies demonstrated both the potential merit of lentivectors in terms of correcting monogenic inherited disorders, and also the importance of using alternate pseudotypes, such as LCMV, to safely transfer therapeutic genes in vivo without producing adverse effects.