Project description: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.
Project description:T cell response exert critical roles in the host adaptive immunity against Pneumocystis. However, the dynamics and diversity of T cell immune repertoire in HIV-negative Pneumocystis remains unknown. In this study, single-cell RNA and T cell receptor (TCR) sequencing were applied on cells sorted from lung tissues of mice infected with Pneumocystis from 0 to 4 weeks. Our data demonstrated clonally CD4+ T cells and CD8+ T cells expanded in response to Pneumocystis, which marked by highly expressed genes associated with T cell activation and cytotoxicity. The length distribution of CDR3 AA and gene usage variability were similar between Pneumocystis infected mice and control group. We tracked the transcriptome and TCR immune repertoires profiles of expanded lymphocyte clones during Pneumocystis infection, which demonstrate a reconstitution of the TCR immune repertoire after Pneumocystis infection.
