Oral DNA chitosan nanoparticles to abrogate existing antibodies to FVIII

ORAU Grant

Hemophilia A is a bleeding disorder. Patients suffer from a deficiency in coagulation factor VIII (FVIII) and require regular life-long infusions of FVIII. Such treatment comes at a great cost, in excess of $100,000 per patient annually in Canada (1). However, the biggest challenge to effective hemophilia management is that 20-30% of severe hemophiliacs develop neutralizing antibodies (inhibitors) to FVIII that renders FVIII infusions ineffective and puts patients at risk of spontaneous bleeds (2). Standard treatment in Canada is immune tolerance induction (ITI), based on large and repeated infusions of FVIII that exhaust the immune response to FVIII (2). However, it is highly expensive (at times >$1,000,000) and further, not always effective. Indeed, FVIII inhibitors is arguably the greatest challenge to hemophilia management today, and alternative efforts for modulating antigenicity to FVIII in a cost-effective manner are highly desirable. Here I propose oral gene therapy as a non-invasive and potentially safer immunomodulatory strategy. Although intriguing, DNA is rapidly degraded in the stomach, preventing an efficient oral DNA delivery protocol (3). If plasmid DNA can be effectively protected from degradation in the stomach, the ingested DNA could reach the intestine where DNA can be taken up by cells, which will express any DNA-encoded proteins. Nanoparticles made out of the common natural polysaccharide chitosan protect plasmid DNA from degradation in the stomach to enhance its uptake by the small intestine. Using chitosan nanoparticles we have achieved low but therapeutic levels of coagulation human factor VIII (FVIII) in hemophilia A mice. Further, and unlike viral vectors, re-administration of nanoparticles is possible. Interestingly, there was no detectable FVIII-specific IgG in the treated mice, even following a FVIII challenge. Of note, transplantation of lymphocytes from the spleen (adoptive transfer) is able to confer reduced immunogenicity in a recipient mouse, suggesting tolerance. The general hypothesis to be tested is that antigen presentation following oral delivery of formulated DNA can induce immune tolerance. The purpose of the proposed experiments is to generate enough data to evaluate the efficacy of various oral formulations of DNA chitosan nanoparticles as a potential novel strategy to reduce or eliminate unwanted immune responses to therapeutic products. In particular, this proposal specifically will attempt to reduce or prevent immune responses to recombinant coagulation factor FVIII in hemophilic mice. While oral tolerance has been widely studied, oral delivery of DNA is a novel approach that might open new therapeutic possibilities, and hence worth pursuing, particularly considering that FVIII antibodies –the socalled inhibitors- cost the health care system in the vicinity of $1M per patient and year. If successful, the proposed strategy may also be applicable in the reduction or prevention of immune responses in other medical conditions.