Potential role for oral tolerance in gene therapy

Abstract

Oral immunotherapies are being developed for various autoimmune diseases and allergies to suppress immune responses in an antigen-specific manner. Previous studies have shown that anti-drug antibody (inhibitor) formation in protein replacement therapy for the inherited bleeding disorder hemophilia can be prevented by repeated oral delivery of coagulation factor antigens bioencapsulated in transplastomic lettuce cells. Here, we find that this approach substantially reduces antibody development against factor VIII in hemophilia A mice treated with adeno-associated viral gene transfer. We propose that the concept of oral tolerance can be applied to prevent immune responses against therapeutic transgene products expressed in gene therapy.

Keywords: Gene therapy; Hemophilia; Oral tolerance.

Fig. 1.

Oral tolerance induction in hemophilia A mice (male BALB/c F8e16^−/−, 6 weeks of age). Lyophilized lettuce leaf cells were administered by oral gavage twice per week after suspension in sterile PBS. The chloroplast transgenic cells expressed cholera toxin B subunit (CTB) fused to heavy chain, light chain, or C2 domain of B-domain deleted hFVIII. HC/LC or HC/C2 antigen combinations were given at doses of 1.5 μg/antigen. A. Experimental outline: Oral delivery was performed for 8 weeks, and AAV8-hFVIII vector was administered after 4 weeks at a dose of 1x10¹¹ vg/mouse. B. Inhibitor titers against FVIII as a function of time after gene transfer. C. IgG1 anti-hFVIII titers 16 weeks after gene transfer. Group sizes: AAV only (control group, no oral gavage): n=5, HC+LC: n=6, HC+LC: n=8. Statistical comparisons were performed using separate one-way ANOVA at each time point corrected with Tukey post hoc test. * P<0.05. ** P<0.01. *** P<0.001. **** P<0.0001.