The long-range goals of this proposal are to create nucleic acid specific delivery systems for the successful treatment of lung resident mycobacterium infections. Mycobacterium tuberculosis (TB) infections are one of most common causes of bacterial related death worldwide. This disease is a major concern for both clinicians and research scientists. A limitation of current treatment regimens is that TB is not treated as a specialty. In general the barriers to successful antimycobacterial therapy include: (1) antibiotic toxicity to host cells; (2) the transport barrier of the mycobacterium cell wall; (3) the membrane barriers of the host cell; and (4) methods to selectively delivery drugs to only infected cells. This proposal will examine possible solutions to each of the limitations with the production of a novel nucleic acid delivery system specialized for lung delivery. Mycobacteria often harbor within human cell macrophages, in doing so they ellude the hosts natural systems as well as exogenously administered antibiotics. Particulate delivery systems (e.g., liposomes) can be used to deliver drugs directly to the macrophage, limiting the body's exposure to potentially toxic drugs and also reducing the cost of therapy. Unfortunately only a fraction of liposomes are endocytosed within alveolar macrophages. The investigators shall develop a dendrimer-integrin mediated targeting system to increase alveolar concentration of drugs. One drug category which has the potential to treat several diseases is oligonucleotides. Oligonucleotides can selectively bind and eliminate mRNA from the translation process. In this manner they can remove various key enzymes or proteins from the cell leading to specific cell voiding deleterious effects on the host. Due to the high specificity of oligonucleotides they have very high therapeutic indexes. Delivery of antisense oligonucleotides to the target's cell cytoplasm, a necessary condition for their activity has been one of the most challenging tasks in their development. The successful delivery systems must consider several variables. It is proposed to use dendrimers as oligonucleotide carriers. Along with the oligonucleotide, the dendrimer will be conjugated with peptides that bind to integrins. Several integrins have been shown to be up regulated on chronically infected macrophages. The system will also use a fusogenic peptide to facilitate oligonucleotide transfer to the sites of action. To overcome the mycobacterium cell wall, a palmitic acid oligonucleotide conjugate will be evaluated in a model in vitro test system.
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