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Indiana University-Purdue University Indianapolis (IUPUI) / Pneumocystis pneumonia (PCP) is the leading opportunistic disease in immunocompromised individuals, particularly in AIDS patients. The alveolar macrophage (AM) is the major type of cell responsible for the clearance of Pneumocystis organisms; however, they undergo a high rate of apoptosis during PCP due to increased intracellular polyamine levels. This study examined the mechanism of this polyamine mediated apoptosis and investigated an alternative therapy for PCP by targeting this mechanism. The elevated polyamine levels were determined to be caused by increased polyamine synthesis and uptake. Increased polyamine uptake was found to be AM-specific, and recruited inflammatory cells including monocytes, B cells, and CD8+ T cells were found to be a potential source of polyamines. The expression of the antizyme inhibitor (AZI), which regulates both polyamine synthesis and uptake, was found to be greatly up-regulated in AMs during PCP. AZI overexpression was confirmed to be the cause of increased polyamine synthesis and uptake and apoptosis of AMs during PCP by gene knockdown assays. Pneumocystis organisms and zymosan were found to induce AZI overexpression in AMs, suggesting that the β-glucan of the Pneumocystis cell wall is responsible for this AZI up-regulation. In addition, levels of mRNA, protein, and activity of polyamine oxidase (PAO) were also found to be increased in AMs during PCP, and its substrates N1-acetylspermidine and N1-acetylspermine were found to induce its up-regulation. These results indicate that the H2O2 generated during PAO-mediated polyamine catabolism caused AMs to undergo apoptosis. Since increased polyamine uptake was demonstrated to be a pathogenic mechanism of PCP in this study, the potential therapeutic activity of five putative polyamine transport inhibitors against PCP was tested. Results showed that compound 44-Ant-44 significantly decreased pulmonary inflammation, organism burden, and macrophage apoptosis, and prolonged the survival of rats with PCP. In summary, this study demonstrated that Pneumocystis organisms induce AZI overexpression, leading to increased polyamine synthesis, uptake, and apoptosis rate in AMs and that targeting polyamine transport is a viable therapeutic approach against PCP.

Philosophiae Doctor - PhD / In the decade since first identified, the Acquired Immunodeficiency syndrome (AIDS) has become a serious global disease. The nature of the Human Immunodeficiency Virus (HIV) that causes AIDS, whereby a carrier may be asymptomatic yet remain infectious, has enabled its dramatic spread. The number of AIDS cases is increasing exponentially, averaging a doubling time of between 8-15 months in different countries. Of the millions of HIV carriers, it is now estimated that all will eventually go on to develop full-blown AIDS and probably die within 15 years. Unlike other infectiqus diseases, there is currently no known vaccine or cure. Further, HIV is now virtually completely dependent on volitional sexual behaviours for transmission to occur. It is therefore an entirely preventable disease. However, since the behaviours that contribute to HIV-transmission are influenced by biological, psychological, and social factors, their alteration in line with safer sexual practices has been shown to be considerably complex and difficult. Intervention strategies that have relied on imparting knowledge about the disease have achieved limited success in influencing behaviour change. Unsafe sexual practices, and the risk of HIV-infection, often continue even when knowledge regarding prevention is adequate. It has therefore become apparent that other variables intrude which may mediate between knowledge acquisition, attitude formation, and consequent sexual behaviours. There appear to be no models which adequately explain the complexities in this area, and which enable adequate intervention strategies to be developed. The present study was undertaken to redress this problem, and to explore those variables that mediate in the area. Various psychological and social factors appear to be implicated in influencing sexual attitudes and behaviours. In order to adequately test the impact of psychosocial variables that were found to have significant associations in an exploratory study, a measuring instrument was developed. The AIDS Psychosocial Scale was statistically validated using content, frequency, factor, and reliability analyses and included psychological factors of self concept, defenses of denial, repression, and rationalisation, perceived empowerment in the form of locus of control and selfefficacy, and the social factor of peer pressure susceptibility. The impact of these psychosocial variables on indices of knowledge, condom attitude, and sexual practices, and on other epidemiological variables was tested using a sample of students at the University of the Western Cape (n=308). Results indicated a number of correlational and causal links between variables, confirming the mediational role psychosocial factors have in influencing knowledge acquisition, attitude formation, and behaviour outcome. A profile of lower self concept, higher defenses, lower self-efficacy, more external locus of control, and higher peer pressure susceptibility emerged which was associated with poorer knowledge, more negative attitudes, and higher unsafe sex. Based on this study, a model of psychosocial mediation is developed and its implications for intervention strategies discussed.