Oesophagostomum dentatum extract modulates T cell-dependent immune responses to bystander antigens and prevents the development of allergy in mice

One third of the human population is currently infected by one or more species of parasitic helminths. Certain helminths establish long-term chronic infections resulting in a modulation of the host’s immune system with attenuated responsiveness to “bystander” antigens such as allergens or vaccines. In this study we investigated whether parasite-derived products suppress the development of allergic inflammation in a mouse model. We show that extract derived from adult male Oesophagostomum dentatum (eMOD) induced Th2 and regulatory responses in BALB/c mice. Stimulation of bone marrow-derived dendritic cells induced production of regulatory cytokines IL-10 and TGF-beta. In a mouse model of birch pollen allergy, co-administration of eMOD with sensitizing allergen Bet v 1 markedly reduced the production of allergen-specific antibodies in serum as well as IgE-dependent basophil degranulation. Furthermore, eMOD prevented the development of airway inflammation, as demonstrated by attenuation of bronchoalveolar lavages eosinophil influx, peribronchial inflammatory infiltrate, and mucus secretion in lungs and IL-4 and IL-5 levels in lung cell cultures. Reduced secretion of Th2-related cytokines by birch pollen-re-stimulated splenocytes and mesenteric lymph node cells was observed in eMOD-treated/sensitized and challenged mice in comparison to sensitized and challenged controls. The suppressive effects of eMOD were heat-stable. Immunization with model antigens in the presence of eMOD reduced production of antibodies to thymus-dependent but not to thymus-independent antigen, suggesting that suppression of the immune responses by eMOD was mediated by interference with antigen presenting cell or T helper cell function but did not directly suppress B cell function. In conclusion, we have shown that eMOD possesses immunomodulatory properties and that heat-stable factors in eMOD are responsible for the dramatic suppression of allergic responses in a mouse model of type I allergy. The identification and characterization of parasite-derived immune-modulating molecules might have potential for designing novel prophylactic/therapeutic strategies for immune-mediated diseases.

Definition of genetic markers in nuclear ribosomal DNA for a neglected parasite of primates, Ternidens deminutus (Nematoda: Strongylida) – diagnostic and epidemiological implications

Ternidens deminutus (Strongylida) is a parasitic nematode infecting non-human and human primates in parts of Africa, Asia and the Pacific islands. The present study genetically characterized T. deminutus and defined genetic markers in nuclear ribosomal DNA (rDNA) as a basis for developing molecular-diagnostic tools. The sequences of the second internal transcribed spacer (ITS-2) of rDNA were determined for adult specimens of T. deminutus (Nematoda: Strongylida: Oesophagostominae) from the Olive baboon and the Mona monkey. The length and G+C content of the ITS-2 sequences was 216 bp and approximately 43%, respectively. While there was no sequence variation among individual T. deminutus specimens from the baboon, 6 (2.8%) nucleotide differences were detected in the ITS-2 between the parasite from baboon and that of the Mona monkey, which is similar to the difference (3.2%) between 2 other species of Oesophagostominae (Oesophagostomum bifurcum and O. stephanostomum) from non-human primates, suggesting significant population variation or the existence of cryptic (i.e. hidden) species within T. deminutus . Pairwise comparisons of the ITS-2 sequences of the 2 operational taxonomic units of T. deminutus with previously published ITS-2 sequences for selected members of the subfamilies Oesophagostominae and Chabertiinae indicated that species from primates (including those representing the subgenera Conoweberia and Ihleia) are closely related, in accordance with previous morphological studies. The sequence differences (27-48.3%) in the ITS-2 between the 2 taxonomic units of T. deminutus and hookworms (superfamily Ancylostomatoidea) enabled their identification and delineation by polymerase chain reaction (PCR)-based mutation scanning. The genetic markers in the ITS-2 provide a foundation for improved, PCR-based diagnosis of T. deminutus infections and for investigating the life-cycle, transmission patterns and ecology of this parasite.

A male-specific (cysteine-rich) protein of Oesophagostomum dentatum (Strongylida) with structural characteristics of a serine protease inhibitor containing two trypsin inhibitor-like domains

A cDNA was isolated from an adult male Oesophagostomum dentatum gene library by screening with a male-specific, partial expressed sequence tag (EST) probe identified previously using a differential display technique. The full-length cDNA of 642 bp included 5' and 3' untranslated regions of 44 and 121 nucleotides, respectively, and encoded a predicted protein with a putative 18 amino acid signal sequence and a mature polypeptide of 14.7 kDa comprising approximately 15% cysteine residues. The amino acid sequence showed similarity with a number of proteins from Caenorhabditis elegans, parasitic nematodes, insects and amphibia, all of which contain a trypsin inhibitor-like cysteine-rich domain. A 3-dimensional structure model constructed for the O. dentatum protein (designated OdmCRP) inferred that it is composed of 2 domains, each with 5 disulfide bonds, which are indicative of the Ascaris family of serine protease inhibitors. These findings indicate that OdmCRP, with 2 structural domains relating to functionally active sites, is a new member of this inhibitor family.

Characterisation of stage-specific proteins of Oesophagostomum dentatum by preparative isoelectric focusing and lectin blotting

The nodular worm of pigs, Oesophagostomum dentatum, has previously been shown to undergo distinct biochemical changes during its life cycle. This phenomenon was studied in more detail for the early parasitic stages. Differences between infective third-stage larvae (L3), parasitic fourth-stage larvae cultivated in vitro (L4c), and pre-adult larvae recovered from the intestinal contents of pigs (L4p) were compared with respect to their protein and glycoprotein patterns by solubility-based protein fractionation and preparative isoelectric focusing followed by SDS-PAGE or by Western blotting with various lectins. While differences between the L4 were only minor (only three bands were specific for either L4c or L4p), L3 displayed distinctly different protein patterns with four L3-specific and nine L4-specific bands. Concanavalin A bound to a variety of glycoproteins, partly in a stage-specific manner, while Ricinus communis Agglutinin 120, Wheat Germ Agglutinin, Peanut Agglutinin and Soybean Agglutinin bound to fewer, partly stage-specific, molecules.

Fatty acid patterns of different stages of Oesophagostomum dentatum and Oesophagostomum quadrispinulatum as revealed by gas chromatography

Total methylated fatty acid patterns of various developmental stages (third-stage larvae (L3), L3 and fourth-stage larvae (L4) cultured in vitro, L4 and female and male adults derived from intestinal contents) of the porcine nodular worms Oesophagostomum dentatum and Oesophagostomum quadrispinulatum and their cultivation medium were analysed by gas chromatography using Microbial Identification computer software. Fatty acids ranging from C-12 to C-20 could be separated. For each stage and species, characteristic patterns were found. The most prevalent fatty acids were C-18. The freshly exsheathed larvae contained the greatest variety of fatty acids (including short-chain fatty acids C-12 to C-15) with approximately equal amounts of fatty acids with odd and even chain lengths, whereas more advanced stages consisted of a lower number of fatty acids with mostly even chain lengths >/=C-16. Intestinal stages contained less odd-numbered fatty acids and less branched fatty acids than others. In contrast to intestinal L4, cultivated L4 had high amounts of C-15:0 and C-17:0. Sheathed L3 contained more C-18 than freshly exsheathed ones, and medium incubated for 7 days in the presence of parasites contained C-13 to C-15 and monounsaturated C-16, but less C-18 and C-20:4 than fresh medium or medium incubated without worms. Based on the evaluation of stage- and species-specific fatty acid patterns random samples could be assigned to the correct stage and species. In a dendrogram based on fatty acid patterns the same stages of the two species formed the closest relationships, and the intestinal stages formed a clade distinct from the cultivated larvae and L3. All stages contained considerable relative amounts of arachidonic acid, the main precursor of eicosanoids. The fixed differences between species and stages indicate genetic regulation of fatty acid patterns, while environmental influences are mirrored by differences between cultivated and intestinal stages. Regulation of fatty acid patterns probably plays a role in worm physiology and host-parasite interaction.