Vera Neubauer1 – Gergely Sárközy1,2 – Georg Simbruner1 – Karina Wegleiter1 – Martina Urbanek1 – Matthias Keller1
1Department of Paediatrics, Medical University Innsbruck;
21st and 2nd Department of Paediatrics, Semmelweis University;

Introduction: Prenatal gene therapy has been considered for severe heritable diseases such as Herlitz junctional epidermolysis bullosa (H-JEB), a lethal genodermatosis caused by the absence of any of the three subunits of laminin-5. This disease results from birth in widespread blistering and erosions of the skin and mucous membranes.

Methods: Adenovirus type 5- and adeno-associated virus (AAV) type 2-derived vectors carrying a beta-galactosidase reporter gene or LAMB3 cDNA encoding the β3 chain of laminin-5 were generated, tested for stability in amniotic fluid and evaluated in vitro on murine H-JEB keratinocytes and in vivo by prenatal injection into the amniotic cavities of laminin-5 β3-deficient mice, an established animal model of H-JEB. The different vectors were administered individually or combined at maximum doses on day 14 post coitum.

Results: Adenoviral vectors infected preferentially the fetal epidermis, whereas AAV delivered the transgene mainly to mucosae of the airways and the upper digestive tract. The LAMB3 transgene was expressed in target epithelia of newborn laminin-5- deficient mice, and transgenic β3 protein was shown to assemble with its endogenous partner chains, resulting in detectable amounts of laminin-5 in the basement membranes of skin and mucosae and in a lower extent of tissue separation in the skin. However, only combined delivery of the two vector types led to a minor increase of the life span of H-JEB mice. Failure to rescue diseased animals was, at least in part, due to the abandonment of any conspicuous pup by the heterozygous mother.

Conclusion: Our findings indicate that combined administration of adenoviral and adeno-associated LAMB3 vectors in utero provides some therapeutic benefit to H-JEB mice. Even a relatively low level of transgene expression may suffice to induce immune tolerance of transgenic laminin-5 and allow additional postnatal treatment without the risk of an immune rejection. However, the animal model used here appears unsuitable for long-term investigations of this therapeutic concept.