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Of the four Plasmodium species which cause malaria in humans, P. falciparum is responsible for the majority of the morbidity and mortality associated with this disease. The surface expression of parasite-derived proteins in the middle of the asexual cycle coincides with two important modifications of the host erythrocyte. First, a protective immune response is directed against a family of variant antigens, known as P. falciparum Erythrocyte Membrane Protein-1 (PfEMPl). Second, ligands are detected at the surface which mediate the specific cytoadherence of infected erythrocytes to vascular endothelium, such that infected cells are sequestered away from the peripheral circulation in deep vascular beds. The potentially fatal syndrome known as cerebral malaria can ensue when infected cells sequester at high density in the brain. Indirect studies have shown that the antigenic and adhesive phenotypes at the surface are linked to the expression of PfEMPl. However, there is a paucity of biochemical data which relate to PfEMPl, and this problem is addressed in this thesis. This study has confirmed, at the biochemical level, inferences from serology that clonal antigenic variation occurred rapidly. Variation produced a number of novel antigenic and adhesive phenotypes which were associated with unique forms of PfEMPl. Further insights into the mechanism of sequestration were possible because of the finding that single infected erythrocytes had the capacity to bind to at least three putative endothelial cell receptors; CD36, Intercellular Adhesion Molecule-1 (ICAM1), and Thrombospondin (TSP). It was demonstrated for the first time that PfEMPl was responsible for cytoadherence to CD36 and ICAM1, but was probably not involved in adhesion to TSP. Extensive analysis with sequence-specific proteases proved that adhesive interactions with each receptor were separable properties of the surface, and facilitated the proposal of a domain model for PfEMPl. Detailed analysis of the antigenic and adhesive phenotypes of a series of clonally-derived parasites demonstrated that infected cells expressing all variant antigenic types could adhere to CD36 whereas adhesion to ICAM1 was seen in a restricted subset. This may be clinically relevant if, as current data suggests, adhesion of infected cells to ICAM1 is important in the development of cerebral malaria. Identification of all ICAM1 binding phenotypes could lead to the design of novel therapeutic strategies for this life-threatening condition.

Abstract: Pneumonia is a primary complication and a leading cause of death for burn patients. Conventional antimicrobial strategies to combat pneumonia in burn patients and others have become less effective due to the emergence of multi-resistant organisms. At the inception of these studies, we aimed to develop a mouse model of post thermal injury pneumonia, to interrogate perturbations of pulmonary immune function and to test alternative therapeutic strategies. We found that burn injury induced a surprising paradoxical resistance to pulmonary infection that developed with time after injury. Instead of abandoning the model, we postulated that an understanding of the mechanisms of induced resistance could be exploited for improving strategies for the treatment of pneumonia. Our studies revealed that the protection from infection following thermal injury was dependent on a systemic increase in functionally enhanced neutrophils, which followed a surge in circulating G-CSF. G-CSF stimulation of the marrow resulted in highly specific activation of STAT3 in mature myeloid and myeloid precursors in the bone marrow, and a reprioritization of hematopoiesis, in which myeloid cell production increased at the expense of other lineages. The myeloid shift in the bone marrow and the systemic increase in neutrophils were temporally related to the acquisition of resistance to infection. Finally, we determined that exogenous administration of G-CSF was sufficient to recapitulate the hematopoietic changes and protection from infection. From this study we concluded that the G-CSF STAT3 axis protects the host from post injury pulmonary infection. In parallel experiments, we also explored the hypothesis that keratinocyte growth factor (KGF), which is known to be induced following injury of the skin, plays an important role in burn induced protection. The concept that KGF might be `arming’ cells and enhancing resistance to infection was based in part on prior work from our laboratory demonstrating that KGF augments pulmonary innate immune function. We have found that the absence of KGF in genetically engineered mice blocks post burn resistance to pulmonary infection, and impairs bacterial clearance from the lung. KGF was also found to regulate soluble antimicrobial activity in the lung lining fluid, due in part to enhanced production of antimicrobial collectins, surfactant proteins A and D. We have not yet determined how these collectins are influenced by burn injury. Thermally injured KGF deficient mice develop an excessive increase in circulating neutrophils compared to their wild type counterparts, yet more readily succumb to post burn infection. These data suggest that inflammatory responses are altered in these mice and that protection from infection induced by burn injury is not simply a function of increased neutrophil numbers. Finally, our data, together with in silico evidence of a remarkable degree of identity between the transcriptional programs activated by G-CSF administration and trauma, suggest to us that G-CSF may be the `Eye of the Genomic Storm’ driving the transition towards innate and away from adaptive immune priorities in the injured host.

Contemporary aesthetics includes a project directed at understanding the nature of pictorial representation. Three types of theories enjoy recent favor. One explains pictorial representation by way of resemblance or experienced resemblance between the picture and what it represents. A second employs interpretation: the spectator looks at a picture and interprets conventionally determined symbols found therein to mean what it represents. The third describes pictorial representation as a matter of experience. On this approach, when the spectator looks at a picture she has a visual experience of the thing represented. Key components of representation include the representation bearing artifact and the human activity that produces it. An adequate account of pictorial representation must neglect neither. Theories focusing on resemblance fail to account for the human role in representation so that a picture may represent only what it can resemble. Theories making interpretation of conventional symbols the key fail to account for the role visible properties play in grounding representation. Wollheim's experience based theory, however, unifies the visible properties of the artifact and the intentions of the artist in a single experience, called seeing-in, whereby a spectator sees in a picture what an artist intends to represent. Wollheim fails to specify just how visible properties of the artifact ground seeing-in. His account of seeing-in raises other curiosities as well. These issues can be dealt with if we apply phenomenological concepts developed by Merleau-Ponty in his Phenomenology of Perception to our experience of pictures as a method of enriching Wollheim's account of seeing-in.