16 Indeed, we found that IA had a longer half-life than IFNα and exhibited hepatic tropism. Liver targeting was ascertained by pharmacokinetic and biodistribution studies and also by the more intense activation of hepatic ISGs when using pIA for liver transduction than when employing pIFN or pALF, despite the fact that albumin-IFNα has a longer half-life than IA. Unexpectedly, fusion of IFNα to

ApoA-I markedly changed check details the biological properties of IFNα. Thus, experiments in murine fibroblasts showed that the cytotoxic effects of either HDL-IA or rIA were significantly lower than those of IFNα. Moreover, although IFNα induces activation-dependent cell death in T lymphocytes,19, 20 this effect is much lower SB431542 mouse with IA. Thus, IA facilitates lymphocyte proliferation in response to mitogens. These in vitro results are in accordance with data from in vivo killing assays where we found that the adjuvant efficacy of IA was far superior to that of IFNα. These findings indicate that the immunostimulatory properties of IA are not merely related to its persistence in circulation but rather to the fact that IA does not induce cell death in activated lymphocytes as does IFNα. In order to explore whether the interaction of IA with SR-BI

(the main ApoA-I receptor11) is required for its enhanced adjuvant activity, we performed in vivo killing assays after LacZ vaccination using as adjuvants pIA or pIFN in SR-BI+/−, SR-BI−/−, and wildtype mice. Our data showing that the adjuvant effect of IA was superior in wildtype animals but not in SR-BI−/− animals indicates that ligation of IA to SR-BI is needed for the fusion protein to display its potent immunostimulatory properties. The lower cytotoxic activity of IA compared to IFNα is also reflected by their different influence on hematopoiesis. One of the side effects of IFNα treatment is the development of leukopenia and thrombocytopenia, which limits its use in patients who already have diminished blood counts.8 In contrast to 上海皓元医药股份有限公司 IFNα, the administration of IA did not significantly reduce the number of platelets and only

caused a transient drop in leukocytes, which rapidly recovered. Moreover, the bone marrow progenitor compartment was induced to proliferate in the absence of significant modifications in the number of circulating leukocytes and platelets, suggesting that IA might stimulate myelo and thrombopoiesis. The safety of IA was also demonstrated in mice whose liver was transduced with an AAV vector encoding IA. No hematological or biochemical toxicity was found in these animals at day 30 after vector administration. The improvement of the pharmacological profile of IFNα resulting from its linkage to ApoA-I was not reproduced by fusion to other apolipoproteins present in HDLs. Anchoring IFNα to ApoF generated an unstable molecule which was not expressed.