Detection and site localization of phosphorylcholine-modified peptides by NanoLC-ESI-MS/MS using precursor ion scanning and multiple reaction monitoring experiments

Tracking Spatial Distribution Alterations of Multiple Endogenous Molecules during Lentil Germination by MALDI Mass Spectrometry Imaging

Exploring the spatial distribution alterations of metabolites during lentil germination is essential to reveal the nutritional value, physiological function, and metabolic pathway in lentils. Hence, an effective matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) method was established for the first time to visualize the spatial localization changes of 53 metabolites in lentils during germination for 12-72 h. The results of MALDI-MSI analysis showed that phosphatidylinositols, phosphatidylethanolamines, phosphatidylglycerols, and phosphatidic acids were mainly located in the cotyledons of lentils throughout the germination process, while triacylglycerols, phosphatidylcholines, diacylglycerols, amino acids, choline, and spermine spread throughout the lentil tissue at the initial stage of germination and gradually presented obvious distribution characteristics in the radicle with increasing germination time. Heat map analysis was used to visualize the correlations between lipid content changes and germination time, which supported the use of germinated lentils as nutraceutical or functional food.

Mass spectrometric and glycan microarray-based characterization of the filarial nematode Brugia malayi glycome reveals anionic and zwitterionic glycan antigens

Millions of people worldwide are infected with filarial nematodes, responsible for lymphatic filariasis (LF) and other diseases causing chronic disablement. Elimination programs have resulted in a substantial reduction of the rate of infection in certain areas creating a need for improved diagnostic tools to establish robust population surveillance and avoid LF resurgence. Glycans from parasitic helminths are emerging as potential antigens for use in diagnostic assays. However, despite its crucial role in host–parasite interactions, filarial glycosylation is still largely, structurally, and functionally uncharacterized. Therefore, we investigated the glycan repertoire of the filarial nematode Brugia malayi. Glycosphingolipid and N-linked glycans were extracted from several life-stages using enzymatic release and characterized using a combination of MALDI-TOF-MS and glycan sequencing techniques. Next, glycans were purified by HPLC and printed onto microarrays to assess the host anti-glycan antibody response. Comprehensive glycomic analysis of B. malayi revealed the presence of several putative antigenic motifs such as phosphorylcholine and terminal glucuronic acid. Glycan microarray screening showed a recognition of most B. malayi glycans by immunoglobulins from rhesus macaques at different time points after infection, which permitted the characterization of the dynamics of anti-glycan immunoglobulin G and M during the establishment of brugian filariasis. A significant level of IgG binding to the parasite glycans was also detected in infected human plasma, while IgG binding to glycans decreased after anthelmintic treatment. Altogether, our work identifies B. malayi glycan antigens and reveals antibody responses from the host that could be exploited as potential markers for LF.

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Antigenic B. malayi N-linked and GSL glycans were structurally defined.

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IgG/IgM is induced to a subset of B. malayi glycans upon infection of rhesus macaques.

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Preferential IgG response to B. malayi glycans observed in chronically infected humans.

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Marked drop of anti-glycan IgG following treatment of individuals with anthelminthic.

Site-specific glycoproteomic characterization of ES-62: The major secreted product of the parasitic worm Acanthocheilonema viteae

ES-62 is the major secreted product of the parasitic filarial nematode Acanthocheilonema viteae and has potent anti-inflammatory activities as a consequence of posttranslational decoration by phosphorylcholine (PC). Previously, we showed that ES-62’s PC was attached to N-linked glycans, and using fast atom bombardment mass spectrometry, we characterized the structure of the glycans. However, it was unknown at this time which of ES-62’s four potential N-glycosylation sites carries the PC-modified glycans. In the present study, we now employ more advanced analytical tools—nano-flow liquid chromatography with high-definition electrospray mass spectrometry—to show that PC-modified glycans are found at all four potential N-glycosylation sites. Also, our earlier studies showed that up to two PC groups were detected per glycan, and we are now able to characterize N-glycans with up to five PC groups. The number per glycan varies in three of the four glycosylation sites, and in addition, for the first time, we have detected PC on the N-glycan chitobiose core in addition to terminal GlcNAc. Nevertheless, the majority of PC is detected on terminal GlcNAc, enabling it to interact with the cells and molecules of the immune system. Such expression may explain the potent immunomodulatory effects of a molecule that is considered to have significant therapeutic potential in the treatment of certain human allergic and autoimmune conditions.

Proteomic profiling of HIV-infected T-cells by SWATH mass spectrometry

Viral pathogenesis results from changes in host cells due to virus usurpation of the host cell and the innate cellular responses to thwart infection. We measured global changes in protein expression and localization in HIV-1 infected T-cells using subcellular fractionation and the Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH-MS) proteomic platform. Eight biological replicates were performed in two independent experimental series. In silico merging of both experiments identified 287 proteins with altered expression (p < .05) between control and infected cells- 172 in the cytoplasm, 84 in the membrane, and 31 in nuclei. 170 of the proteins are components of the NIH HIV interaction database. Multiple Reaction Monitoring and traditional immunoblotting validated the altered expression of several factors during infection. Numerous factors were found to affect HIV infection in gain- and loss-of-expression infection assays, including the intermediate filament vimentin which was found to be required for efficient infection.

Sensing parasites: Proteomic and advanced bio-detection alternatives

Parasitic diseases have a great impact in human and animal health. The gold standard for the diagnosis of the majority of parasitic infections is still conventional microscopy, which presents important limitations in terms of sensitivity and specificity and commonly requires highly trained technicians. More accurate molecular-based diagnostic tools are needed for the implementation of early detection, effective treatments and massive screenings with high-throughput capacities. In this respect, sensitive and affordable devices could greatly impact on sustainable control programmes which exist against parasitic diseases, especially in low income settings. Proteomics and nanotechnology approaches are valuable tools for sensing pathogens and host alteration signatures within microfluidic detection platforms. These new devices might provide novel solutions to fight parasitic diseases. Newly described specific parasite derived products with immune-modulatory properties have been postulated as the best candidates for the early and accurate detection of parasitic infections as well as for the blockage of parasite development. This review provides the most recent methodological and technological advances with great potential for bio-sensing parasites in their hosts, showing the newest opportunities offered by modern "-omics" and platforms for parasite detection and control.

The PCome of Ascaris suum as a model system for intestinal nematodes: identification of phosphorylcholine-substituted proteins and first characterization of the PC-epitope structures

In multicellular parasites (e.g., nematodes and protozoa), proteins and glycolipids have been found to be decorated with phosphorylcholine (PC). PC can provoke various effects on immune cells leading to an immunomodulation of the host's immune system. This immunomodulation allows long-term persistence but also prevents severe pathology due to downregulation of cellular immune responses. PC-containing antigens have been found to interfere with key proliferative signaling pathways in B and T cells, development of dendritic cells and macrophages, and mast cell degranulation. These effects contribute to the observed modulated cytokine levels and impairment of lymphocyte proliferation. In contrast to glycosphingolipids, little is known about the PC-epitopes of proteins. So far, only a limited number of PC-modified proteins from nematodes have been identified. In this project, PC-substituted proteins and glycolipids in Ascaris suum have been localized by immunohistochemistry in specific tissues of the body wall, intestine, and reproductive tract. Subsequently, we investigated the PCome of A. suum by 2D gel-based proteomics and detection by Western blotting using the PC-specific antibody TEPC-15. By peptide-mass-fingerprint matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), we could identify 59 PC-substituted proteins, which are in involved multiple cellular processes. In addition to membrane proteins like vitellogenin-6, we found proteins with structural (e.g., tubulins) and metabolic (e.g., pyruvate dehydrogenase) functions or which can act in the defense against the host's immune response (e.g., serpins). Initial characterization of the PC-epitopes revealed a predominant linkage of PC to the proteins via N-glycans. Our data form the basis for more detailed investigations of the PC-epitope structures as a prerequisite for comprehensive understanding of the molecular mechanisms of immunomodulation.