Abstract P3059: Recombinant Adeno-associated Viral Vector 2/8 Model Of Interleukin 6 Mediated Chronic Inflammation

Abstract

Background: Interleukin 6 (IL6) is a pleiotropic cytokine mostly known as a proinflammatory cytokine. There is a need for a reliable in vivo model to study IL6 mediated chronic inflammation. Hypothesis: The aim of our study was to create a mouse model mimicking the chronic inflammatory state as observed in cancer and inflammatory diseases. We opted for a recombinant adeno-associated viral vector (rAAV) to mimic the acute initiation of chronic inflammation later in life. Methods: We opted for a rAAV2/8 subtype, human EF1a short (EFS) promoter and firefly luciferase led by an internal ribosome entry site (IL6-IRES-fLuc) DNA cassette to create a stable low-grade expression of IL6 in liver and serum, with minimal expression in other organs, particularly the heart. rAAV2/8_EFS-IL6-IRES-fLuc and the control vector rAAV2/8_EFS-MCS-IRES-fLuc were generated and different dosages were tested. Results: All mice treated with high dose AAV2/8-IL6 vector (8.8* 10 10 genome copies (GC)/animal) showed severe weight loss and hepatosplenomegaly, starting between week 4-6 post injection. Histological examination of the liver showed features of chronic hepatitis. Infiltrating cells were found in both the liver and the heart. In the spleen, the histological structure of red and white pulp was disturbed and more giant cells could be detected. Cardiac function remained normal at 6 weeks post injection. Assuming that the previous results were due to an overexpression of IL6 due to too high amounts of rAAV2/8_EFS-IL6-IRES-fLuc, we subsequently challenged mice with a rAAV2/8_EFS-IL6-IRES-fLuc dilution series to test which vector dose could be used for reliable long-term low grade IL6 overexpression. After extensive testing, the ideal dose for a 12 weeks IL6 overexpression model was between 2.2 and 2.93* 10 10 GC. Using this dose range, we saw stable overexpression of IL6 without weight loss. Hepatosplenomegaly, disturbed anatomy of the spleen and infiltrating cells in the liver were still present yet less pronounced. Conclusion: We successfully generated and characterized a mouse model of IL6 overexpression to mimic chronic IL6 mediated inflammation. To the best of our knowledge this is the first model employing IL6 overexpression using a rAAV viral vector.