CRISPR-mediated detection of Pneumocystis transcripts in bronchoalveolar, oropharyngeal, and serum specimens for Pneumocystis pneumonia diagnosis
Ontology highlight
ABSTRACT: CRISPR-mediated detection of Pneumocystis transcripts in bronchoalveolar, oropharyngeal, and serum specimens for Pneumocystis pneumonia diagnosis
Project description:Background. Pneumocystis jirovecii pneumonia (PCP) is a leading cause of fungal pneumonia, but its diagnosis primarily relies on invasive bronchoalveolar lavage (BAL) specimens that are difficult to obtain. Oropharyngeal swabs and serum could improve the PCP diagnostic workflow, and we hypothesized that CRISPR could enhance assay sensitivity to allow robust P. jirovecii diagnosis using swabs and serum. Herein we describe the development of an ultrasensitive RT-PCR-coupled CRISPR assay with high active-infection specificity in infant swabs and adult BAL and serum. Methods. Mouse analyses employed an RT-PCR CRISPR assay to analyze P. murina transcripts in wild-type and Rag2-/- mouse lung RNA, BAL, and serum at 2-, 4-, and 6-weeks post-infection. Human studies used an optimized RT-PCR CRISPR assay to detect P. jirovecii transcripts in infant oropharyngeal swab samples, adult serum, and adult BAL specimens from P. jirovecii-infected and P. jirovecii-non-infected patients. Results. The P. murina assays sensitively detected Pneumocystis RNA in the serum of infected mice throughout infection. Oropharyngeal swab CRISPR assay results identified infants infected with P. jirovecii with greater sensitivity (96.3% vs. 66.7%) and specificity (100% vs. 90.6%) than RT-qPCR compared to mtLSU standard marker, and CRISPR results achieved higher sensitivity than RT-qPCR results (93.3% vs. 26.7%) in adult serum specimens. Conclusion. Since swabs are routinely collected in pediatric pneumonia patients, serum is easier to obtain than BAL, and RT-PCR CRISPR results may not detect P. jirovecii colonization, this assay approach could improve pediatric Pneumocystis diagnosis by achieving specificity for active infection and avoiding the requirement for BAL specimens.
Project description:β-glucans, which can activate innate immune responses, are a major component in the cell wall of the cyst form of Pneumocystis. In the current study we examined whether β-1,3 glucans are masked by surface proteins in Pneumocystis, and what role β-glucans play in Pneumocystis-associated inflammation. For 3 species, including P. jirovecii, which causes Pneumocystis pneumonia (PCP) in humans, P. carinii, and P. murina, β-1,3 glucans were masked in most organisms, as demonstrated by increased exposure following trypsin treatment. Using Q-PCR and microarray techniques, we demonstrated in a mouse model of PCP that treatment with caspofungin, an inhibitor of β-1,3 glucan synthesis, for 21 days, decreased expression of a broad panel of inflammatory markers, including IFN-γ, TNF-α, IL-1β, IL-6, and multiple chemokines/chemokine ligands. Thus, β-glucans in Pneumocystis cysts are largely masked, which likely decreases innate immune activation; this mechanism presumably was developed for interactions with immunocompetent hosts, in whom organism loads are substantially lower. In immunosuppressed hosts with a high organism burden, organism death and release of glucans appears to be an important contributor to deleterious host inflammatory responses.
Project description:Humanized NOG-EXL (huNOG-EXL) mice control P. murina infection significantly better than control NOG-EXL mice, as evidenced by markedly decrased lung fungal burdens at both 3 and 6 weeks post-infection. Human cytokine-generating CD4+ and CD8+ T cells in the lung and serum IgM antibody, which were specifically in responses to pneumocystis antigen, were detected in huNOG-EXL mice only. For humanized NOG-EXL mouse group at 6 weeks post-infection, the whole lung RNAseq analyses were performed and the data indicated that the lower lung fungal burden is associated with higher CD209 gene expression.
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.