Methods for noninvasive monitoring of muscle fiber survival with an AAV vector encoding the mSEAP reporter gene

A Versatile Vector for In Vivo Monitoring of Type I Interferon Induction and Signaling

Development of reporter systems for in vivo examination of IFN-β induction or signaling of type I interferon (IFN-I) pathways is of great interest in order to characterize biological responses to different inducers such as viral infections. Several reporter mice have been developed to monitor the induction of both pathways in response to different agonists. However, alternative strategies that do not require transgenic mice breeding have to date not been reported. In addition, detection of these pathways in vivo in animal species other than mice has not yet been addressed. Herein we describe a simple method based on the use of an adeno-associated viral vector (AAV8-3xIRF-ISRE-Luc) containing an IFN-β induction and signaling-sensitive promoter sequence controlling the expression of the reporter gene luciferase. This vector is valid for monitoring IFN-I responses in vivo elicited by diverse stimuli in different organs. Intravenous administration of the vector in C57BL/6 mice and Syrian hamsters was able to detect activation of the IFN pathway in the liver upon systemic treatment with different pro-inflammatory agents and infection with Newcastle disease virus (NDV). In addition, intranasal instillation of AAV8-3xIRF-ISRE-Luc showed a rapid and transient IFN-I response in the respiratory tract of mice infected with the influenza A/PR8/34 virus lacking the NS1 protein. In comparison, this response was delayed and exacerbated in mice infected with influenza A/PR/8 wild type virus. In conclusion, the AAV8-3xIRF-ISRE-Luc vector offers the possibility of detecting IFN-I activation in response to different stimuli and in different animal models with no need for reporter transgenic animals.

Restriction of calpain3 expression to the skeletal muscle prevents cardiac toxicity and corrects pathology in a murine model of limb-girdle muscular dystrophy

BACKGROUND

Genetic defects in calpain3 (CAPN3) lead to limb-girdle muscular dystrophy type 2A, a disease of the skeletal muscle that affects predominantly the proximal limb muscles. We previously demonstrated the potential of adeno-associated virus-mediated transfer of the CAPN3 gene to correct the pathological signs in a murine model for limb-girdle muscular dystrophy type 2A after intramuscular and locoregional administrations.

METHODS AND RESULTS

Here, we showed that intravenous injection of calpain3-expressing vector in mice can induce mortality in a dose-dependent manner. An anatomopathological investigation revealed large areas of fibrosis in the heart that we related to unregulated proteolytic activity of calpain3. To circumvent this toxicity, we developed new adeno-associated virus vectors with skeletal muscle-restricted expression by using new muscle-specific promoters that include the CAPN3 promoter itself and by introducing a target sequence of the cardiac-specific microRNA-208a in the cassette. Our results show that CAPN3 transgene expression can be successfully suppressed in the cardiac tissue, preventing the cardiac toxicity, whereas expression of the transgene in skeletal muscle reverts the pathological signs of calpain3 deficiency.

CONCLUSIONS

The molecular strategies used in this study may be useful for any gene transfer strategy with potential toxicity in the heart.