231 Biological Therapy of HIV/AIDS Using HIV-based Vectors Containing Anti-HIV Genetic Payloads B. Dropulic*1,2, L. Humeau1, X. Lu1, V. Slepushkin1, B. Levine3, Q. Yu1, Y. Ni1, B. Davis1, R. Carroll3, Y. Chang1, C. June3 1VIRxSYS Corp, Gaithersburg, MD; 2Kimmel Cancer Ctr at Johns Hopkins, Johns Hopkins Univ Sch of Med, Baltimore, MD; and 3Abramson Family Cancer Res Inst, Univ of Pennsylvania, Philadelphia
Background: Due to the adverse side-effects associated with the current class of HIV-1 antiretroviral drugs, the great propensity of HIV-1 to mutate and the lack of an effective vaccine, the search for new modalities for AIDS therapy has been of the highest priority. An attractive alternative to drug therapy is biological therapy for HIV using HIV-based vectors that interfere with wt-HIV replication and spread. The goal for this biological therapy in vivo would be to deliver the vector to sufficient numbers of T-cells that would decrease patient (pt) viral loads to levels that are not conducive to the development of AIDS.
Methods: An optimized candidate HIV vector containing a 937 n.t. anti-HIV envelope antisense payload was identified. Primary human CD4 T-cells were transduced at greater than 90% efficiency.
Results: Transduced CD4 T-cells were highly resistant to productive HIV replication when challenged with wt-HIV. The optimized candidate vector inhibited the replication of various wt-HIV strains by 3 logarithmic units, as measured by the p24 ELISA assay. Transduced cells were found to be selectively resistant to productive HIV replication and had a survival advantage. Pt scale transduction and ex vivo expansion of T-cells from normal human donors revealed no toxic effects to the cells and an average vector copy number of 6 copies per cell, as assayed by TaqMan PCR. Cell doubling, viability, cell size, and surface marker profile were comparable to control cells that were not treated with vector. No replication competent lentivirus (RCL) was detected using a sensitive assay. Transduction of CD4 T-cells from HIV-infected donors demonstrated similar transduction efficiencies, potent inhibition of HIV replication, and selective resistance to productive HIV infection. Selection of breakthrough virus on sub-optimally transduced Sup T1-cells revealed a HIV mutant envelope with a 12% mutation frequency. Inserting the mutant envelope back into HIV resulted in a severely attenuated virus. Inhibition of HIV replication with long antisense sequences may be an attractive mode for reducing HIV resistance since it would require many mutations and would result in HIV genomes that are severely attenuated for replication.
Conclusions: HIV vectors potently inhibit HIV replication and preclinical studies show no adverse effects due to the vector. The first phase I clinical trial using HIV vectors for the treatment of HIV infection is planned for 2003.
