Keywords: HIV/AIDS; vaccine; gene therapy
HIV infection in humans induces chronic changes in the phenotype and function of CD4, CD8 and dendritic cells, which are only partly restored after the initiation of highly active anti-retroviral therapy (HAART). In order to alleviate the permanent dependency on HAART, alternative therapies, whose goal is to restore normal immune function, must be developed. Attenuated pox-viruses are currently under evaluation as prophylactic or therapeutic vaccines against AIDS. Development of a successful pox-virus vaccine is still a significant challenge due to the nature of HIV-1 infection, despite the fact that pox-virus vector vaccines can induce potent humoral and cellular immune responses, and have been developed for large-scale vaccine production under GMP conditions. This project will exploit this knowledge and employ state of the art bioengineering to create a pox-virus vector that encodes, in addition to specific HIV-1 proteins, a fully functional lentiviral vector genome delivering heterologous genes with HIV inhibitory capacity. Cells infected with modified vaccinia virus ankara (MVA) will simultaneously be converted into packaging cells capable of releasing transducing particles and cells expressing HIV-1 proteins for the stimulation of antigen specific cells. Consequently, the pox-gene vector will serve a dual role as a therapeutic vaccine and as in vivo gene therapy. The transducing particles released in vivo will protect naïve, memory and activated T-cells (including HIV antigen-specific T-cells) from HIV infection. During the course of this project, the pox-gene efficiency for transduction of T-cells in vitro and in vivo using marker genes will be demonstrated. Finally, after proof of concept has been achieved in mice, a small pilot study in SHIV infected macaques will be performed. This approach should elicit significant improvement in the management of HIV infection and reduce the costs involved by limiting dependency on HAART. Most importantly, the pox-gene vector has the potential for worldwide application, including use in developing countries.
HIV-1 infection in humans severely perturbs T-helper responses, leading to immune deficiency, the onset of opportunistic infections and acquired immunodeficiency syndrome (AIDS). While the advent of highly active anti-retroviral therapy (HAART) has greatly improved the immune status of HIV-1 infected patients by increasing their CD4 T-cell counts and restoring specific responses to opportunistic infections, several problems still remain. The first is that despite effective inhibition of virus production, CD4 T-cell and dendritic cell numbers do not reach their normal pre-infection values. Secondly, immune responses directed against HIV-1 remain largely ineffective in controlling virus load. Thirdly, serious side effects and long-term toxicity, as well as emergence of resistant viruses, limit the long-term effectiveness of HAART. Lastly, the expense of these drugs, the constant need to monitor for the emergence of drug resistance, the required compliance to a very strict drug regime and the vast population affected make HAART unsuitable and unaffordable for developing countries.
Studies in animal models and humans undergoing different types of chronic viral infections, including CMV, EBV etc., have shown that infection can be effectively controlled by specific memory CD4 and CD8 T-cell subpopulations, which are impaired in patients chronically infected with HIV-1. In contrast, these responses are partially maintained in long-term non-progressors (LTNP) who control virus replication better in the absence of HAART. In this project, it is proposed to develop a treatment that will reinforce the patient’s immune response to HIV and render their T-cells resistant to infection. This goal shall be achieved by in vivo transduction of anti-HIV specific memory cells, as well as other naïve and activated T-cells with a lentiviral construct carrying an effective combination of anti-HIV constructs.
The goal of this project is to develop a combined vaccination/gene therapy protocol as a new and promising candidate intervention for the treatment of HIV infection. Currently available technology for genetically modifying MVA pox-viruses to create a vector that expresses both HIV-1 proteins and an HIV inhibitory lentiviral construct will be exploited. Target cells infected with MVA will therefore not only express HIV-1 proteins capable of stimulating antigen specific T-cells, thereby boosting anti-HIV-1 immune responses, but will also release lentiviral particles capable of transducing antigen stimulated T-cells with an anti-viral gene that protects them from HIV-1 infection. Significantly, genes that inhibit virus entry will be employed and will, therefore, not only protect the transduced cell but also exert a bystander protective effect.
The following exploitable therapeutic products are expected to emerge from this project.
It is the strategic objective of this research project to develop an effective new disease intervention for one of the major communicable diseases, i.e. HIV infection of humans. Worldwide, over 40 million people are infected with HIV and AIDS is a major cause of mortality, particularly in developing countries. Currently, the only effective treatment available is highly active anti-retroviral therapy (HAART). Despite its success, it is clear that HAART cannot eradicate the virus and that sustained treatment is required. However, lifetime treatment is not always practicable, particularly in developing countries. Therefore, additional therapies are urgently required. This project’s goal is to combine therapeutic vaccination with direct in vivo gene transfer using a genetically modified vaccinia vector. This pox-gene strategy should provide effective disease intervention, which can then be used in developed, as well as developing, countries. Once established, this therapeutic approach should also be applicable for the treatment of other systemic diseases affecting the immune system, including chronic viral infections such as Hepatitis C.
Biomedical Primate Research Centre: Department of Virology
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