Soil transmitted nematodes, including Strongyloides, cause one of the most prevalent Neglected Tropical Diseases. Here we compare the genomes of four Strongyloides spp., including the human pathogen S. stercoralis, and their close relatives that are facultatively parasitic (Parastrongyloides trichosuri) and free-living (Rhabditophanes sp). A significant paralogous expansion of key gene families – astacin-like and SCP/TAPS coding gene families – is associated with the evolution of parasitism in this clade. Exploiting the unique Strongyloides life cycle we compare the transcriptome of its parasitic and free-living stages and find that these same genes are upregulated in the parasitic stages, underscoring their role in nematode parasitism.

The human pathogen Leishmania synthesizes phosphoglycans (PGs) formed by variably modified phosphodisaccharide [6-Gal␤1-4Man␣1-PO 4 ] repeats and mannooligosaccharide phosphate [(Man␣1-2) 0 -5 Man␣1-PO 4 ] caps that occur lipid-bound on lipophosphoglycan, protein-bound on proteophosphoglycans, and as an unlinked form. PG repeat synthesis has been described as essential for survival and development of Leishmania throughout their life cycle, including for virulence to the mammalian host. In this study, this proposal was investigated in Leishmania mexicana using a spontaneous mutant that was fortuitously isolated from an infected mouse, and by generating a lmexlpg2 gene deletion mutant (⌬lmexlpg2), that lacks a Golgi GDP-Man transporter. The spontaneous mutant lacks PG repeats but synthesizes normal levels of mannooligosaccharide phosphate caps, whereas the ⌬lmexlpg2 mutant is deficient in PG repeat synthesis and down-regulates cap expression. In contrast to expectations, both L. mexicana mutants not only retain their ability to bind to macrophages, but are also indistinguishable from wild type parasites with respect to colonization of and multiplication within host cells. Moreover, in mouse infection studies, the spontaneous L. mexicana repeat-deficient mutant and the ⌬lmexlpg2 mutant showed no significant difference to a wild type strain with respect to the severity of disease caused by these parasites. Therefore, at least in Leishmania mexicana, PG repeat synthesis is not an absolute requirement for virulence.

Leishmania promastigotes, the stage of the parasite characteristic for the sandfly vector, express an abundant glycoconjugate, called lipophosphoglycan, at their surface. Lipophosphoglycan consists of lysoalkyl-sn-glycerophosphoinositol linked to a phosphosaccharide core conserved in all species, which is connected to PO,-6Galpl ,4Manal repeats with species-specific substitutions at the Gal residue; the repeats are capped by conserved and species-specific oligosaccharides. Most Leishmania species also secrete an acid phosphatase, which, in Leishmania mexicana, is a filamentous complex composed of a phosphorylated glycoprotein and non-covalently associated proteo-(highmolecular-mass)phosphoglycan.The secreted acid phosphatase complex was used as an antigen to derive a panel of monoclonal antibodies (mAbs). A total of 25 mAbs (17 novel and 8 previously described) were tested by different techniques for their specificity against lipophosphoglycan and secreted acid phosphatase from several Leishmunia species. This comparison and the modification of the antigens by chemical or enzymic treatments allowed a classification of the mAbs into several groups. First, from 25 mAbs examined, 22 recognize lipophosphoglycan and the enzyme complex of L. mexicana; only three are specific for secreted acid phosphatase. Two of the latter group are also directed against carbohydrate structures, whereas the third mAb recognizes the 100-kDa polypeptide of the complex. The secreted acid-phosphatase-specific class detects antigen in the flagellar pocket of promastigotes while all anti-lipophosphoglycan mAbs bind to the cell surface.Second, all 15 anti-lipophosphoglycan mAbs investigated in detail appear to be directed against the phosphosaccharide repeats or the cap structure rather than the phosphosaccharide core. Two mAbs recognize terminal cap-structures containing Manal,2Man residues. Four antibodies are specific for L. mexicana and are probably directed against PO,-6[Glc/?l ,3]GaI/31,4Manal repeats while six inAbs react with the unmodified repeats. Two antibodies specific for Leishmania major recognize Galj?l,3-substituted repeats unique for lipophosphoglycan from this species.Analysis by immunoblotting indicates that the high-molecular-mass proteo-phosphoglycan of L. mexicana secreted acid phosphatase carries epitopes for all anti-lipophosphoglycan mAbs suggesting the presence of capped phosphosaccharide repeats while the enzymically active glycoprotein subunit is modified by caps but probably not by repeats. In the case of Leishmania donovani secreted acid phosphatase, the enzymically active polypeptide may be directly modified by repeats.The mAbs are used to characterize changes in lipophosphoglycan structure, which occur in culture during the transition of promastigotes from the logarithmic to the stationary growth phase. Furthermore, testing the mAbs against seven species demonstrates their potential for serotyping Leishmania.Protozoan parasites of the genus Leishmania cause a spectrum of diseases ranging from the localized, re...

Dendritic cells (DC) can induce Th1 cell differentiation by producing IL-12. In experimental infection with Leishmania major, DC could differently respond to infection and induce Th1 cells in C57BL/6 but not BALB/c mice, and thus determine the resistance or susceptibility of these mice. We characterized L. major antigen-containing DC in vivo in draining lymph nodes of both strains. Conventional experimental infection is shown to result in two waves of these DC and our data argue against a relevant genetic difference in the DC initiating the anti-parasite Th cell response in these mice. In both strains the first wave of DC presented L. major antigens but was not infected, produced IL-12 but induced disease-mediating Th2 cells upon adoptive transfer. In contrast to current belief, this response was therefore not initiated by infected DC, which were only detected in the second wave. The kinetics of the two waves suggests that DC turnover has an important impact on antigen presentation during infections with complex pathogens.

Healing of leishmaniases is dependent on activation of parasitized macrophages (Mphi) by IFN-gamma, which is secreted by Leishmania-specific Th1 cells. IL-12 enhances IFN-gamma production by Th1 cells and is crucial for cure. The host cells of Leishmania sp., Mphi, are a main source of IL-12 in vivo. We report that infection of quiescent murine Mphi with L. mexicana or L. major amastigotes does not induce IL-12 production. Moreover, infection suppresses IL-12 secretion by Mphi activated by LPS, by CD40 cross-linking or cognate interaction with Th1 cells. IL-12 secretion is also suppressed in Mphi activated after phagocytosis of latex beads. Suppression is independent of engagement of CR3 or FcgammaR during phagocytosis, is not mediated by IL-10 and does not alter steady state IL-12p40 mRNA levels. In addition, suppression of IL-12 secretion does not depend on Mphi activation concurrent to infection. In contrast, NO production was not inhibited. Thus, Mphi effector functions are differentially affected and this may be a general effect of phagocytosis of non-activating particles. The possible implications of this effect on the infection are discussed.