rAAV-based gene therapy for molybdenum cofactor deficiency type B

by Joanna Jakubiczka-Smorag
Doctoral thesis
Date of Examination:2015-06-03
Date of issue:2015-06-29
Advisor:Prof. Dr. Peter Burfeind
Referee:Prof. Dr. Peter Schu
Referee:Prof. Dr. Wolfgang Brück
Persistent Address: http://dx.doi.org/10.53846/goediss-5161

 

 

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Abstract

English

Molybdenum cofactor (MoCo) deficiency type A is thus far only one curable type of MoCo deficiency. In the present study, a mouse model for MoCo deficiency type B (Mocs2-/-) was generated, characterised and used for preclinical trials. To create pure knockouts of each Mocs2 isoform (Mocs2a-/- and Mocs2b-/-), Mocs2-/- animals were crossed with generated transgenic mice expressing either the human MOCS2A or human MOCS2B isoform. In turn, the Mocs2a-/- animals were established. Due to several problems with MOCS2A transgenic mice, we could not establish a Mocs2b-/- line. The type of therapy relevant for MoCo deficiency is strictly dependent upon the type of the disease. The substitution therapy sufficient for rescuing MoCo deficiency type A is not effective in type B or C. In contrast to cyclic pyranopterin monophosphate (cPMP), other intermediate products of MoCo biosynthesis such as molybdopterin (MPT) and active MoCo, are unstable due to incorporated sulphur atoms. For this reason, we designed and developed a gene therapy approach using recombinant adeno-associated virus (rAAV). A single injection using relatively low doses of rAAV was able to drive expression of the MOCS2B therapeutic protein for at least two years. Additionally, a potential tumour formation risk caused by random integration of rAAV DNA into the host genome was analysed. Although the rAAV treatment increased the risk of tumour formation, it was highly dependent upon the genetic background of treated animals. Moreover, rAAV induced tumours did not occur earlier in treated animals compared with the onset of spontaneous tumours presented in untreated control animals. Finally, the rAAV encoding human MOCS2B protein was generated and its infection ability was evaluated in mice. Thus far, we have been unable to test therapeutic values of generated rAAV.
Keywords: MOCS2; MoCo deficiency type B; rAAV-based gene therapy
 
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