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The Major Surface Glycoprotein of Pneumocystis murina Does not Activate Dendritic Cells

ABSTRACT: The major surface glycoprotein (Msg) is the most abundant surface protein of Pneumocystis species. Given that Msg is present on both the cyst and trophic form of Pneumocystis, and dendritic cells play a critical role in initiating host immune responses, we undertook studies to examine activation of bone marrow-derived myeloid dendritic cells by Msg purified from P. murina. Incubation of dendritic cells with Msg did not lead to increased expression of CD40, CD80, CD86, or MHCII, or increased secretion of any of 10 cytokines. Microarray analysis identified very few differentially expressed genes. In contrast, LPS activated dendritic cells by all of these assays. However, Msg did bind to mouse mannose macrophage receptor and human DC-SIGN, two C-type lectins expressed by dendritic cells that are important in recognition of pathogen-associated high mannose glycoproteins. Deglycosylation of Msg demonstrated that this binding was dependent on glycosylation. These studies suggest that Pneumocystis has developed a mechanism to avoid activation of dendritic cells, potentially by the previously identified loss of genes that are responsible for the high level of protein mannosylation found in other fungi.

ORGANISM(S): Mus musculus

PROVIDER: GSE112229 | GEO | 2018/12/26

REPOSITORIES: GEO

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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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The Major Surface Glycoprotein of Pneumocystis murina Does not Activate Dendritic Cells

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