A dissertation submitted to the Faculty of Science University of the Witwatersrand Johannesburg, in fulfilment of the requirements of the degree of Master of Science 14 February 2017. / Spirooxindoles are an important class of spirocycles in organic and medicinal chemistry. They are characterised by a spiro-ring fused with the oxindole scaffold and have a wide range of biological activity. We are particularly interested in spirooxindoles because of their antimalarial activity. Malaria is a major health problem in many parts of the world and the burden caused by the disease is still of great concern. In 2015 alone, an estimated 438 000 deaths due to malaria were reported across the world, with 90% of the deaths occurring in Africa. The increase in drug resistance to currently used antimalarial agents has rendered most of them ineffective, thereby contributing to the high mortality rates. As a result, there is a need for the development of new effective antimalarial agents. In the search for a new class of antimalarial chemotypes, cipargamin, introduced as NITD609 by norvatis in 2010 was synthesised. This compound is a novel synthetic antimalarial candidate, with an IC50 of ~1 nM against P. falciparum strains, including multi drug-resistant strains. Previously in our laboratory, several spirooxindole derivatives were synthesised using an imino Diels-Alder reaction, also known as the Povarov reaction. Of all the compounds synthesised, only those derived from a para-substituted aniline displayed activity in the low micromolar range (~5μM) against P. falciparum in vitro. In this project, we aimed to further explore the antimalarial activity of these compounds by designing and synthesising ring-opened analogues. The analogues were successfully synthesised by a Grignard addition reaction using N-Boc protected arylimines as electrophiles. Despite several attempts, we were unable to remove the Boc-protecting group in the final step. The second series of compounds we aimed to synthesise were ring closed analogues lacking one aromatic ring. The compounds were synthesised starting from an imine condensation reaction between benzyl protected isatin with para-substituted 2-allyanilines. The 2-allylanilines were prepared by subjecting N-allylanilines to an aza-Cope rearrangement. The arylimines prepared were then subjected to a nucleophilic Grignard addition reaction with commercially available vinylmagnesium bromide to yield the intermediate necessary for the ring closure step. Unfortunately, the nucleophilic addition reaction was unsuccessful. The ring-closure step is very crucial during the synthetic route as it gives rise to the desired ring closed analogues via ring-closing metathesis. Although we were unable to reach the final step in the synthesis of ring-closed analogues, some progress was made in developing methodology for the synthesis of these analogues. The synthesised ring-opened analogues were screened for antimalarial activity against P. falciparum in vitro. Six hit compounds were identified from the series of compounds tested with tert-butyl 3-(2,4-dichlorophenethyl)-2-oxo-3-(p-tolylamino)indoline-1-carboxylate 60 being the most active compound in the series with an IC50 value of 0.60 nM against the FCR 3 Strain. In general, compounds derived from p-toluidine displayed the most potent activity. / MT2017

In this thesis, mechanisms of immunoregulation by CD4$ sp+$ T cells during blood-stage P. chabaudi AS infection in C57BL/6 mice were studied. The kinetics of in vitro production of the Th1-derived cytokine, IFN-$ gamma$, versus the Th2-derived cyokines, IL-4, IL-5 and IL-10, by spleen cells as well as of polyclonal and malaria-specific antibodies in the sera were examined during infection using enzyme-linked immunosorbent assays. Upon antigenic stimulation, spleen cells were found to produce high levels of IFN-$ gamma$ several days prior to peak parasitemia, while high levels of IL-10 production occurred at the time of peak parasitemia followed by IL-4 and IL-5 later in infection. The levels of polyclonal IgG2a isotype were found to be increased during both the acute and chronic phases of infection, whereas the levels of polyclonal IgM, IgG1 and IgG2b isotypes were found to be increased only during the chronic phase of infection. High titers of malaria-specific IgG2a and IgG1 were detected during the primary as well as secondary infections. Investigation of in vitro proliferation of spleen cells to mitogens and malaria specific antigen revealed that the responses of splenic lymphocytes from infected mice to Con A, PHA and LPS were suppressed, with the most severe suppression occurring during the first 14 days post infection. Evidence is provided demonstrating that nitric oxide (NO) and prostaglandins (PG), products of activated macrophages, mediated suppression of lymphocyte proliferation in response to Con A and PHA, whereas only PG were found to suppress LPS-stimulated proliferation. In addition, NO was found to mediate suppression of proliferation of spleen cells from infected mice in response to parasite antigen. Taken together, results from these studies suggest that immune activation and immunosuppression occur simultaneously during blood-stage malaria with P. chabaudi AS infection in C57BL/6 mice. (Abstract shortened by UMI.)

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No description available.

Malaria is one of the most serious human infectious diseases. To date, the collection of studies suggest that the disease is determined by transmission dynamics and host age altogether with host genetics and immunological responses. The precise and direct contribution of parasite components to the activation of such immunological responses has not been fully unravelled. In addition to a role proposed for plasmodial GPI, different lines of evidence suggest that hemozoin (HZ) could also be a potential inflammatory agent. The role of HZ in the modulation of immune responses has remained a polemic subject, making it difficult to describe the contribution of this molecule in pathogenesis of malaria. However, our previous laboratory studies, suggest that HZ has a pro-inflammatory role. For this reason, our study was designed to further define the contribution of HZ to the pro-inflammatory events related to malaria immunopathology, and to identify the intracellular signals underlying the up-regulatory effects of HZ in the macrophage, one of the major sources of inflammatory mediators in malaria. In order to do that, we used a chemically characterized synthetic version of the native PfHZ, rcHZ; and evaluated its effects on macrophage nitric oxide (NO) production. Our first approach was to compare the effects of rcHZ with other morphologically different versions of this molecule (aHZ and scHZ) alone or in combination with IFN-gamma on macrophage NO production. In a second approach, we evaluated if the presence of serum proteins plays a role in the increased IFN-gamma induced-NO production by rcHZ. In the third part of our study, we explored if rcHZ is able to increase NO production by macrophages when incubated in combination with a molecule from another pathogen, such as gram-negative bacteria lipopolysaccaride (LPS). The present study is a functional study that uses a synthetic and morphologically identical version of the native PfHZ. Our results suggests that intrinsic physical characteristics, such as shape and size; presence of host serum proteins, and presence of other pathogenic molecules, are important determinants for the macrophage response to HZ in the context of NO production. Besides, it describes part of the signaling pathways that are involved, which may contribute in the future, not only to understand mechanisms of regulation; but also, to find new therapeutic targets against malaria.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 122-133) / Microfiche. / xvi, 133 leaves, bound ill. 29 cm

Abstract not available

No description available.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 134-152) / Microfiche. / xvi, 152 leaves, bound ill. 29 cm

No description available.