Induction of interferon-gamma by Taenia crassiceps glycans and Lewis sugars in naive BALB/c spleen and peritoneal exudate cells.

Helminth parasites are known to alter host immune responses and the responsible molecules are a potential source of biological immunoadjuvants. Previously, we have reported strong Th-2 type immunomodulatory properties of Taenia crassiceps glycans. In this study, we report interferon-gamma (IFN-gamma) stimulatory activity of fractionated Taenia glycans and Lewis sugars with comparable glycan composition. Our data show that Taenia glycans and Lewis X pentasaccharide are potent stimulators of the Th-1 type cytokine IFN-gamma. We postulate that the terminal beta-(1-4)-galactose residue in Lewis X is associated with IFN-gamma stimulation from naive BALB/c mouse spleen and peritoneal exudate cells. Antibodies to toll-like receptors (TLRs) inhibited the Lewis X-induced IFN-gamma secretion. Lewis X up-regulated the expression of NF-kappaB p65 from naive spleen cells and IFN-gamma transcription in peritoneal exudate cells. These data demonstrate the ability of Lewis type helminth glycans to modulate host responses in a Th-1 direction via NF-kappaB p65, IFN-gamma and macrophage TLRs.

Adjuvant effect of Taenia crassiceps glycans against leishmanial antigens in mice infected with Leishmania mexicana.

Complex glycans derived from lipid, nucleic acid and protein free extracts of Taenia crassiceps metacestode larvae were found to have adjuvant effect against Leishmania mexicana antigens in BALB/c mice experimentally infected with L. mexicana. A single intraperitoneal or subcutaneous injection of Taenia glycans altered the Th-1/Th-2 balance in experimentally infected mice as determined by Western blot analysis of IgG 1 and IgG 2a antibodies to L. mexicana antigens. Leishmania antigens which were immunogenic in Taenia glycan vaccinated mice were different from those of non-vaccinated mice. Vaccination induced leishmania antigen specific IFN-gamma expression in vitro culture by spleen cells from Taenia glycan vaccinated-leishmania infected mice and not from mock vaccinated-leishmania infected BALB/c mice. We conclude that T. crassiceps glycans have immunoadjuvant effects against leishmania and may be developed as adjuvants in anti-leishmania vaccines.

Taenia crassiceps carbohydrates stimulate IL-6 expression in naïve murine macrophages via Toll-like receptors (TLRs).

In murine infections of Schistosoma mansoni and Taenia crassiceps, a characteristic polarization of the immune response from a Th-1 type to a Th-2 type occurs with progression of infection. In S. mansoni, egg glycoprotein carbohydrates are said to be responsible for this immunomodulatory activity. We have previously shown that in vitro systems, T. crassiceps carbohydrates (TCHO) up-regulate the expression of interleukin 6 (IL-6) in naïve spleen cells, while conventional Th-2 cytokines were not detected. In this report, we show that peritoneal macrophages are the source of this early IL-6 and that these cells recognize T. crassiceps carbohydrates via Toll-like receptors (TLRs). Co-stimulation experiments with synthetic sugars showed that the most likely active moieties in TCHO are Lewis X analogues. To our knowledge, this is the first report on native carbohydrates of a helminth parasite stimulating mammalian innate immune cells to produce a Th-2 polarizing cytokine (IL-6) via a Toll-like receptor. It is hypothesized this is a general mechanism of Th-2 immunodominance in helminth infections in mammalian hosts.

Induction of immunoglobulin G1, interleukin-6 and interleukin-10 by Taenia crassiceps metacestode carbohydrates.

T helper type 2 (Th2) -polarized immune responses are characteristically dominant in helminth infections. Two murine models that show a Th1 to Th2 polarization with infection progression are those of Schistosoma mansoni and Taenia crassiceps. In both, an early Th1 response is replaced by a late Th2 response. We report that the nucleic acid-, protein- and lipid-free carbohydrate fraction of T. crassiceps metacestodes (denoted T-CHO) possesses Th2-like immunomodulatory activity. Immunization of two strains of rats (Dark Agouti and Albino Oxford) and BALB/c mice with chicken albumin in the presence of T-CHO resulted in selective enhancement of immunoglobulin G1 (IgG1) antibodies, considered to be associated with Th2 responses in both rats and mice. Interleukin-6 (IL-6) followed by IL-10 were the dominant cytokines detected in in vitro cultures of mouse spleen cells stimulated with T-CHO. IL-4 and IL-5 were not detected in these culture supernates. Furthermore, Taenia carbohydrates were mitogenic to spleen cells, activated serine phosphorylation of proteins and up-regulated the expression of the anti-apoptotic protein, Bcl-2. When mouse spleen cells were cultured in the presence of Taenia carbohydrates, a concentration-dependent down-regulation of IL-2 and an overlapping up-regulation of IL-6 secretion were seen.

Asymptomatic human carriers of Leishmania chagasi.

In Brazil, programs based on elimination of infected dogs have not curtailed the spread of visceral leishmaniasis (VL), suggesting that other reservoirs of infection exist. Persons with active VL can infect the sand fly vector, but in endemic areas, persons with asymptomatic infections, whose infectivity to sand flies is unknown, are far more numerous. In this study, a polymerase chain reaction-based assay detected kinetoplast DNA of Leishmania chagasi in the blood of eight of 108 asymptomatic persons living with patients with recently diagnosed VL. These eight persons had low or unmeasurable levels of IgG antibodies to Leishmania, demonstrating the insensitivity of serology for subclinical infection. All eight persons had positive leishmanin skin test results, as did 70% of persons living in households of persons with active VL. Even if a small proportion of such asymptomatic persons are infective to sand flies, they represent a formidable reservoir of infection in endemic areas.

Immunomodulation by parasites: high mobility group 2 (HMG-2) protein is a putative intracellular mediator for fucosylated sugars of Schistosoma mansoni.

Fucosylated sugars in Schistosoma mansoni possess immunomodulatory properties. In order to gain insights to the mechanisms involved, attempts were made to identify host immune cell molecules that specifically recognize these sugars. On Western blots, specific binding of synthetic biotinylated fucose sugars to proteins of approximately 25-27kDa was observed. Three proteins were isolated by affinity chromatography and subjected to protein sequencing. The determined N-terminal sequences and that of tryptic peptides of two proteins did not show homology to known sequences in the NCBI database. The third was identified as a member of the high mobility group 2 (HMG-2) proteins. In vitro stimulation of mouse spleen cells with Lewis(x) sugars up-regulated the expression of HMG-2 mRNA. These data suggest that HMG-2 protein may function as a putative intracellular receptor/mediator for fucosylated sugars of parasites.