Parental transfer of the antimicrobial protein LBP/BPI protects Biomphalaria glabrata eggs against oomycete infections

Copyright: © 2013 Baron et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was funded by ANR (ANR-07-BLAN-0214 and ANR-12-EMMA-00O7-01), CNRS and INRA. PvW was financially supported by the BBSRC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Human IgG1 Responses to Surface Localised Schistosoma mansoni Ly6 Family Members Drop following Praziquantel Treatment

The heptalaminate-covered, syncytial tegument is an important anatomical adaptation that enables schistosome parasites to maintain long-term, intravascular residence in definitive hosts. Investigation of the proteins present in this surface layer and the immune responses elicited by them during infection is crucial to our understanding of host/parasite interactions. Recent studies have revealed a number of novel tegumental surface proteins including three (SmCD59a, SmCD59b and Sm29) containing uPAR/Ly6 domains (renamed SmLy6A SmLy6B and SmLy6D in this study). While vaccination with SmLy6A (SmCD59a) and SmLy6D (Sm29) induces protective immunity in experimental models, human immunoglobulin responses to representative SmLy6 family members have yet to be thoroughly explored.Using a PSI-BLAST-based search, we present a comprehensive reanalysis of the Schistosoma mansoni Ly6 family (SmLy6A-K). Our examination extends the number of members to eleven (including three novel proteins) and provides strong evidence that the previously identified vaccine candidate Sm29 (renamed SmLy6D) is a unique double uPAR/Ly6 domain-containing representative. Presence of canonical cysteine residues, signal peptides and GPI-anchor sites strongly suggest that all SmLy6 proteins are cell surface-bound. To provide evidence that SmLy6 members are immunogenic in human populations, we report IgG1 (as well as IgG4 and IgE) responses against two surface-bound representatives (SmLy6A and SmLy6B) within a cohort of S. mansoni-infected Ugandan males before and after praziquantel treatment. While pre-treatment IgG1 prevalence for SmLy6A and SmLy6B differs amongst the studied population (7.4% and 25.3% of the cohort, respectively), these values are both higher than IgG1 prevalence (2.7%) for a sub-surface tegumental antigen, SmTAL1. Further, post-treatment IgG1 levels against surface-associated SmLy6A and SmLy6B significantly drop (p = 0.020 and p < 0.001, respectively) when compared to rising IgG1 levels against sub-surface SmTAL1.Collectively, these results expand the number of SmLy6 proteins found within S. mansoni and specifically demonstrate that surface-associated SmLy6A and SmLy6B elicit immunological responses during infection in endemic communities

Does chemical cross-linking with NHS esters reflect the chemical equilibrium of protein-protein noncovalent interactions in solution?

Chemical cross-linking in combination with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has emerged as a powerful tool to study non-covalent protein complexes. Nevertheless, there are still many questions to answer: Does the amount of detected cross-linked complex correlate with the amount of protein complex in solution? In which concentration and affinity range is specific cross-linking possible? In order to answer these questions, we performed systematic cross-linking studies with two complexes using the N8 hydroxysuccinimidyl ester disuccinimidyl suberate (DSS): i) NCoA-1 and mutants of the interacting peptide STAT6Y, covering a KD range of 30 nM to > 25 μM and ii) α-thrombin and basic pancreatic trypsin inhibitor (BPTI), which shows a buffer dependent KD value between 100 and 320 μM. Samples were analyzed by MALDI-MS. For NCoA-1•STAT6Y, a good correlation of the amount of cross-linked species with the calculated fraction of complex present in solution was observed. Thus, chemical cross-linking in combination with MALDI-MS can be used to rank binding affinities. The specificity of complex formation for the mid-affinity range up to about KD ≈ 25 μM could be proven by comparing against a non-binding peptide and by studying the concentration dependence. In order to study in which affinity range specific cross-linking can be applied, the weak α-thrombin•BPTI complex was investigated. Although variations of the sodium concentration can change the dissociation constant up to 3-fold for this interaction, no significant effect on the amount of detected complex was observed at different peptide concentrations. Our interpretation of this result is that the detected complex is not specific, but a nonspecifically cross-linked species. Consequently, chemical cross-linking is not applicable to low-affinity complexes with KD >> 25 μM with the experimental approach used in this study

Plasmodium ookinetes coopt mammalian plasminogen to invade the mosquito midgut

Ookinete invasion of the mosquito midgut is an essential step for the development of the malaria parasite in the mosquito. Invasion involves recognition between a presumed mosquito midgut receptor and an ookinete ligand. Here, we show that enolase lines the ookinete surface. An antienolase antibody inhibits oocyst development of both Plasmodium berghei and Plasmodium falciparum, suggesting that enolase may act as an invasion ligand. Importantly, we demonstrate that surface enolase captures plasminogen from the mammalian blood meal via its lysine motif (DKSLVK) and that this interaction is essential for midgut invasion, because plasminogen depletion leads to a strong inhibition of oocyst formation. Although addition of recombinant WT plasminogen to depleted serum rescues oocyst formation, recombinant inactive plasminogen does not, thus emphasizing the importance of plasmin proteolytic activity for ookinete invasion. The results support the hypothesis that enolase on the surface of Plasmodium ookinetes plays a dual role in midgut invasion: by acting as a ligand that interacts with the midgut epithelium and, further, by capturing plasminogen, whose conversion to active plasmin promotes the invasion process