Development of transgenic mouse models to study HIV -1 replication

Abstract

Efficient HIV-1 replication in mice is limited by their lack of human-restricted HIV-1 receptors and co-factors required for HIV-1 replication. The goal of this thesis was to use a transgenic approach to delineate the contribution of different human factors on in vivo production of HIV-1 in mice. The demonstration that seven-transmembrane chemokine receptors function with CD4 as co-receptors for HIV-1 entry allowed us to investigate whether the introduction of both co-receptors into the mouse genome would overcome the inability of HIV-1 to infect mice. The directed-expression of the human CD4 and CCR5 co-receptors in mouse T cells permitted mouse lymphocytes to be infected in vitro with primary HIV-1 isolates. After inoculation of human CD4/CCR-5 transgenic mice with either intrasplenic or intraperitoneal injections of HIV-1, we were able to detect integration of HIV-1 in lymphoid tissues, but evidence of productive in vivo replication was absent. To investigate the post-integration phase of HIV-1 replication, we created a second transgenic model for HIV-1 infection by introducing the proviral genome of a primary M-tropic HIV-1 isolate under the transcriptional control of its LTR. These mice produce infectious HIV-1 viral particles capable of infecting activated human PBMCs in vitro. Two transgenic lines were shown to have high levels of plasma viremia comparable to that seen in HIV-1 infected individuals. Moreover, it was possible to increase plasma viremia levels by stimulation of the mouse immune system either with injection of the superantigen Staphylococcus enterotoxin B or infection with M. tuberculosis.;In order to increase the usefulness of our transgenic mouse models, we tried to increase HIV-1 replication in our mice using two approaches. First of all, we looked at the ability of a human-specific factor, Cyclin T, to increase HIV-1 replication in our mice. Expression of human Cyclin T protein in the T cells of mice transgenic for HIV-1 JRCSF resulted in increased plasma viremia, demonstrating that increased replication of HIV-1 in vivo is possible by the addition of HIV-1 cofactors. A second approach for increasing HIV-1 replication was to increase the susceptibility of mice to HIV-1 infection by breeding our human CD4/CCR5 transgenic mice with our HIV-1 JRCSF transgenic mice to create mice that can both express infectious HIV-1 and have co-receptor expression for spread of infection. These mice display elevated plasma viremia, but no evidence of increased pathology. These two mouse models represent a productive first step in the development of a new in vivo system to evaluate the effectiveness of candidate HIV-1 vaccines and to study the pathobiology of HIV-1 infection.