Production of Chimeric HTLV-I with the Envelope of Moloney Murine Leukemia Virus

Abstract

P027 Because of the lack of a good animal model, the pathogeny of the diseases associated with HTLV-I is still poorly understood. With the aim to produce a mouse model for HTLV-I infection, we have constructed an infectious chimeric clone of HTLV-I in which the envelope precursor sequence (gp46 and gp21) has been replaced by the ecotropic envelope precursor sequence of Moloney Murine Leukemia Virus (Mo-MuLV), except for the signal peptide. The propagation of this chimera will result from the ability of MuLV ecotropic envelope to infect murine cells, and will depend on the replicative characteristics of HTLV-I genome. Such a chimera with a murine tropism will help to study the pathogeny of this infection in mice with its typical features which are low viral expression in CD4 T cells, and the presence of the viral Tax oncogene. The construction has been achieved using a previously described infectious molecular clone of HTLV-I. Transfection of this chimeric plasmid in human fibroblastic cell line 293 produced all HTLV-I proteins except for the envelope. As shown by confocal immunoflurorescence, the murine envelope was expressed at the cell surface of transfected cells. Chimeric viral particles were observed by electron microscopy. In order to compare the infectivity of this chimeric virus on primate and murine cells, we produced human fibroblasts (293 cells) and rhesus monkey lung-derived fibroblasts (B5 cells) stably expressing the murine receptor for MuLV (the cationic amino-acid transporter mCAT-1). These cells and murine fibroblasts (3T3) or primary splenocytes were infected either by cell free chimeric particles or by cocultivation with transfected cells. The infectivity of this chimeric HTLV-I/Mo-MuLV in vitro on different cells, as well as some preliminary in vivo infections of mice will be discussed.