The epidemiology and virulence factors of pneumocystis
Pneumocystis is a diverse group of fungi found in the lungs of mammals, and can cause a fatal pneumonia in immunosuppressed humans. The project focussed on two main areas of Pneumocystis biology. The first part investigated the transmission of P. jiroveci between humans and comprised three studies. The first study demonstrated direct transmission between a mother and her infant who had Pneumocystis pneumonia, PCP, contemporaneously. The second investigated transmission of P. jiroveci between health care workers and patients with PCP. P. jiroveci was identified in HCW samples but the genotyping data did not demonstrate direct transmission between the HCW and the patients. The third study examined a representative distribution of P. jiroveci genotypes within a whole human lung and identified two foci of infection. The second main area of research investigated PRT1, a multigene family, encoding a protein with homology to KEX-like proteases. The first part of this study attempted to identify the original single-copy PRT1 gene that encodes the progenitor kexin-like protease. Inconclusive sequence data was obtained. The second part of this study examined regulation of PRT1 gene expression, initially using an assay that characterised the length polymorphisms within the proline rich region of the PRT1 gene. In the complex populations of rat-derived Pneumocystis used it was difficult to distinguish reliable differences between the cDNA (expressed) and genomic DNA proline rich region profiles. Subsequent investigations used simple rat-derived Pneumocystis populations that were derived from inocula of 10 Pneumocystis organisms intratracheally injected into nude rats. The catalytic domain of PRT1 was sequenced from cDNA and genomic copies from each of the five low-dose populations. Two majority sequence types were identified, one genomic and the other cDNA. Three of the populations contained a cDNA majority sequence type, implying that some form of regulation of expression was occurring. This hypothesis was further investigated using a second set of simple populations, hybridisation techniques and 5' RACE.