Project description:Pneumocystis is a pathogen of immunocompromised hosts but can also infect healthy hosts, in whom infection is rapidly controlled and cleared. To better understand the immune mechanisms contributing to clearance of infection, microarray methods were used to examine differential gene expression in the lungs of C57BL/6 and CD40 ligand knock-out (CD40L-KO) mice over time following exposure to Pneumocystis. Immuncompetent C57BL/6 mice, which control and clear infection efficiently, showed a robust response to infection characterized by the upregulation of 349 primarily immune-response associated genes. Temporal changes in the expression of these genes suggested that there was an early (week 2) primarily innate response, that waned without controlling infection; this were followed by primarily adaptive immune responses that peaked at week 5 and successfully cleared the infection. In conjunction with the latter, there was an increased expression of B cell associated (immunoglobulin) genes at week 6 that persisted through 11 weeks. In contrast, CD40L-KO mice, which are highly susceptible to developing severe Pneumocystis pneumonia, showed essentially no upregulation of immune-response associated genes at days 35 to 75. Immunohistochemical staining supported these observations by demonstrating an increase in CD4+, CD68+, and CD19+ cells in C57BL/6 but not CD40L-KO mice. Thus, the healthy host demonstrates a robust biphasic response to infection by Pneumocystis; CD40 ligand is an essential upstream regulator of the adaptive immune responses that efficiently control infection and prevent development of progressive pneumonia. Keywords: Time course response Pneumocystis murina infection wild type versus CD40L-KO mice In experiment 1, C57BL/6 and CD40L-KO mice were co-housed in 2 cages; one cage was exposed to a P. murina-infected seeder, while the second was unexposed. Mice (3 per group) were sacrificed at day 32. Because the initial study demonstrated very little change in gene expression in CD40L-KO mice, only C57BL/6 mice were used for experiments 2 and 3. In Experiment 2, three cages (10 animals/cage) were set up: 2 cages were exposed to P. murina, and one was unexposed. Animals (5 per cage) were sacrificed at days 34 and 41. In Experiment 3, which focused on gene expression early after exposure to P. murina, five cages (9-10 animals/cage) were set up, of which 3 were exposed and 2 were unexposed. Animals (1-3 per cage) were sacrificed at days 7, 14 and 21 of exposure. Experiment 4 was designed to verify the initial results in CD40L-KO mice, and included 5 unexposed controls and 4 mice exposed for 35 days.

Project description:Pneumocystis pneumonia is the most common serious opportunistic infection in patients with HIV/AIDS. Furthermore, Pneumocystis pneumonia is a feared complication of the immunosuppressive drug regimens used to treat autoimmunity, malignancy, and post-transplantation rejection. With an increasing at-risk population, there is a strong need for novel approaches to discover diagnostic and vaccine targets. There are multiple challenges to finding these targets, however. First, Pneumocystis has a largely unannotated genome. To address this, we evaluated each protein encoded within the Pneumocystis genome to that of other fungi using NCBI Blast. Second, Pneumocystis relies on a multiphasic life cycle, as both the transmissible form, the ascus, and the replicative form, the troph, reside within the alveolar space of the host. Towards that end, we purified asci and trophs from Pneumocystis murina and utilized transcriptomics to identify differentially regulated genes. Two such genes, Arp9 and Sp, are differentially regulated in the ascus and the troph, respectively, and can be utilized to characterize the state of the Pneumocystis life cycle in vivo. Gsc1, a β-1,3-glucan synthase with a large extracellular domain previously identified using surface proteomics, was more highly expressed on the ascus form of Pneumocystis. GSC-1 ectodomain immunization generated a strong antibody response capable of recognizing the surface of the Pneumocystis asci. GSC-1 ectodomain immunization was also capable of reducing ascus burden following primary challenge with Pneumocystis murina. Finally, mice immunized with the GSC-1 ectodomain had limited burden following natural transmission of Pneumocystis using a co-housing model. Pneumocystis asci and trophs were separated via flow cytometry and the transcriptome was sequenced, allowing to further understand the differential expression of various RNA transcripts. These data can be mined for life-form specific diagnostics and therapeutic targets.

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