Haruhiko Maruyama

IL-18 with IL-2 protects against Strongyloides venezuelensis infection by activating mucosal mast cell–dependent type 2 innate immunity

C57BL/6 (B6) and B6 background STAT6−/− mice pretreated with IL-18 plus IL-2 showed prominent intestinal mastocytosis and rapidly expelled implanted adult worms of the gastrointestinal nematode Strongyloides venezuelensis. In contrast, identically pretreated mast cell–deficient W/Wv mice failed to do so. Thus, activated mucosal mast cells (MMC) are crucial for parasite expulsion. B6 mice infected with S. venezuelensis third-stage larvae (L3) completed parasite expulsion by day 12 after infection, whereas IL-18−/− or IL-18Rα −/− B6 mice exhibited marked impairment in parasite expulsion, suggesting a substantial contribution of IL-18–dependent MMC activation to parasite expulsion. Compared with IL-18−/− or IL-18Rα −/− mice, S. venezuelensis L3–infected STAT6−/− mice have poorly activated MMC and sustained infection; although their IL-18 production is normal. Neutralization of IL-18 and IL-2 further reduces expulsion in infected STAT6−/− mice. These results suggest that collaboration between IL-18–dependent and Th2 cell–dependent mastocytosis is important for prompt parasite expulsion.

A Secreted Protein from the Human Hookworm Necator americanus Binds Selectively to NK Cells and Induces IFN-γ Production

Parasitic helminths induce chronic infections in their hosts although, with most human helminthiases, protective immunity gradually develops with age or exposure of the host. One exception is infection with the human hookworm, Necator americanus, where virtually no protection ensues over time. Such observations suggest these parasites have developed unique mechanisms to evade host immunity, leading us to investigate the role of the excretory/secretory (ES) products of adult N. americanus in manipulating host immune responses. Specifically, we found that a protein(s) from ES products of adult N. americanus bound selectively to mouse and human NK cells. Moreover, incubation of purified NK cells with N. americanus ES products stimulated the production of augmented (4- to 30-fold) levels of IFN-γ. This augmentation was dependent on the presence of both IL-2 and IL-12 and was endotoxin-independent. This is the first report of a pathogen protein that binds exclusively to NK cells and the first report of a nematode-derived product that induces abundant levels of cytokines from NK cells. Such an interaction could provide a means of cross-regulating deleterious Th2 immune responses in the host, thereby contributing to the long-term survival of N. americanus.

Protective Effect of Vaccination with Toxoplasma Lysate Antigen and CpG as an Adjuvant against Toxoplasma gondii in Susceptible C57BL/6 Mice

Infection with the intracellular protozoan parasite Toxoplasma gondii causes serious public health problems to both humans and livestock and of great economic impact worldwide. Oligodeoxynucleotides (ODN) which contain immunostimulatory CG motifs (CpG ODN) can promote Th1 responses, an adjuvant activity that is desirable for vaccination against intracellular pathogens. We investigated the feasibility of using CpG as an adjuvant combined with Toxoplasma lysate antigen (TLA) as a vaccine against toxoplasmosis. Genetically susceptible C57BL/6 mice were vaccinated with TLA with or without CpG ODN as an adjuvant and then challenged with 85 cysts of the moderately virulent RRA (Beverley) strain of T gondii. Prior to challenge infection, immunization with TLA plus CpG ODN directed cellular and humoral immunity toward a Th1 pattern, characterized by enhanced INF7 production by splenic cells in response to TLA, and enhanced production of toxoplasma‐specific IgG and IgG2a antibodies. Consequently, CpG/TLA‐treated mice showed prolonged survival and 64% reduction in brain parasite burden compared to non‐CpG/TLA treated group. Our results suggest that CpG ODN would provide a stable and effective adjuvant for use in vaccination against toxoplasmosis.

Intraepithelial infiltration of eosinophils and their contribution to the elimination of adult intestinal nematode, Strongyloides venezuelensis in mice

Eosinophils were examined for the capacity of attacking Strongyloides venezuelensis adult worms in the intestinal mucosa by using interleukin (IL)-5 transgenic mice. In IL-5 transgenic mice, most of the subcutaneously inoculated infective larvae were killed during migration, and only a few worms could reach the small intestine. When the same number of adult worms were surgically implanted in the small intestine of IL-5 transgenic and control mice, fecal egg output as well as the number of adult worms recovered from the intestine was significantly lower in IL-5 transgenic mice. In the intestinal mucosa of IL-5 transgenic mice, large number of eosinophils was present in the lamina propria even before adult worm implantation. The number of eosinophils increased significantly as early as 24 h after implantation and tripled by day 3, whereas mucosal eosinophilia remained low in wild-type mice. Most notably, eosinophils infiltrated into the intestinal epithelium and surrounded adult worms in IL-5 transgenic mice, which was never seen in wild-type control mice. However, IL-5 transgenic mice required the same period as normal mice to completely expel implanted adult worms. The amount of specific IgA as well as total IgA in the stool was high in IL-5 transgenic mice before adult worm implantation, and dropped rapidly after adult worm implantation. The present study suggests that eosinophils are capable of attacking adult nematodes in the intestinal epithelia, probably in conjunction with secretory IgA, although they are not enough for the complete worm expulsion.

p53 gene mutations in rectal cancer associated with schistosomiasis japonica in Chinese patients.

Mutations in p53 tumor suppressor gene were examined in 44 Chinese patients with rectal cancer, including 22 cases with advanced schistosomiasis japonica and 22 cases without schistosomiasis. In schistosomal rectal cancer (SRC), 13 mutations were found in 10 cases, which included 11 base-pair substitutions and two deletions. Of 11 base substitutions, nine were transitions and two were transversions and seven of them were located at CpG dinucleotides. In non-schistosomal rectal cancer (NSRC), 13 mutations were found in nine cases, all of which were base-pair substitutions. Of 13 substitutions, 10 were transitions and three were transversions and three of them were located at CpG dinucleotides. The proportion of base-pair substitutions at CpG dinucleotides was higher in SRC patients than in NSRC patients, although this was not statistically significant (P = 0.054). Point mutation was frequent at codon 248 in SRC. A higher frequency of arginine missense mutations was observed in SRC than in NSRC. These observations suggest that the mutations in SRC are the result of genotoxic agents produced endogenously through the course of schistosomiasis japonica.

Strongyloides venezuelensis: longitudinal distribution of adult worms in the host intestine is influenced by mucosal sulfated carbohydrates

Mechanisms for the longitudinal distribution of parasitic females of Strongyloides venezuelensis in the host intestine were investigated in mice. Adult worms were mostly recovered from the anterior-most one-third of the small intestine throughout the infection after infective larvae inoculation. Surgically implanted adult worms established well in the small intestinal mucosa, either in the duodenum or in the ileum, whereas a few worms could establish in the large intestine. Implanted worms in the small intestine remained where they were implanted until expelled. Mucosal mast cells were induced in the whole small intestine after the worm implantation. In the large intestine, a considerable number of adult worms settled in the mucosa of mutant mice, whose goblet cell mucins were undersulfated because of a mutation in sulfate-activating enzymes. In these mice, the degree of sulfation of goblet cell mucins in the large intestine was significantly reduced to the level of normal small intestine goblet cell mucins. Our results suggest that sulfated glycoconjugates, either from mucosal mast cells or goblet cells, have important effects on the longitudinal distribution of parasitic females of S. venezuelensis.

A case report of pleural sparganosis

Abstract A rare form of sparganosis is reported. A 47-year-old man admitted with chest pain and pleural effusion was diagnosed immunologically as having sparganosis. He was successfully treated with praziquantel.

Successive changes in tissue migration capacity of developing larvae of an intestinal nematode, Strongyloides venezuelensis

Infective larvae of an intestinal nematode, Strongyloides venezuelensis, enter rodent hosts percutaneously, and migrate through connective tissues and lungs. Then they arrive at the small intestine, where they reach maturity. It is not known how S. venezuelensis larvae develop during tissue migration. Here we demonstrate that tissue invasion ability of S. venezuelensis larvae changes drastically during tissue migration, and that the changes are associated with stage-specific protein expression. Infective larvae, connective tissue larvae, lung larvae, and mucosal larvae were used to infect mice by various infection methods, including percutaneous, subcutaneous, oral, and intraduodenal inoculation. Among different migration stages, only infective larvae penetrated mouse skin. Larvae, once inside the host, quickly lost skin penetration ability, which was associated with the disappearance of an infective larva-specific metalloprotease. Migrating larvae had connective tissue migration ability until in the lungs, where larvae became able to settle down in the intestinal mucosa. Lung larvae and mucosal larvae were capable of producing and secreting adhesion molecules.

Secreted adhesion molecules of Strongyloides venezuelensis are produced by oesophageal glands and are components of the wall of tunnels constructed by adult worms in the host intestinal mucosa

The parasitic female of Strongyloides venezuelensis keeps invading the epithelial layer of the host intestinal mucosa. Upon invasion, it adheres to the surface of the intestinal epithelial cells with adhesion molecules secreted from the mouth. It has been demonstrated that S. venezuelensis are expelled from the intestine because mucosal mast cells inhibit the attachment of adult worms to the mucosal surface. In the present study, we generated specific antibodies against secreted adhesion molecules to investigate their function in vivo, because these molecules have been demonstrated only in vitro in spite of the importance in the infection processes. A mouse monoclonal antibody specific to S. venezuelensis adhesion molecules inhibited the attachment of adult worms to plastic dishes and the binding of adhesion molecules to rat intestinal epithelial cells. Immunohistochemical study revealed that adhesion molecules were produced by oesophageal glands and were continuously secreted in vivo to line the wall of the tunnels formed by adult worms in the intestinal mucosa. Our findings indicate that adhesion molecules play essential roles in the infection processes of S. venezuelensis in the host intestine.

Enhanced UV♀1 tumor growth in CBF1 mice infected with Schistosoma mansoni due to modulation of Th1-like responses

Effects of Schistosoma mansoni infection on anti-tumor immunity were examined in CBF1 mice with ultraviolet-induced UVfemale1 fibrosarcoma cells. Although many laboratory established tumor cells had rejection mechanisms independent of CD4(+) T cells, we confirmed that CD4(+) cells had significant roles in rejection of UVfemale1 cells in the syngeneic CBF1 mice. When we prepared two CBF1 mouse groups, S. mansoni-infected and schistosome-free, the former group showed up-regulation of Th2-like response to UVfemale1 cells, whereas the latter group mice showed rather type 1-dominant patterns. Cytotoxic activity against UVfemale1 cells tested in vitro, which was attributed to CD8(+) cells, was significantly weaker in S. mansoni-infected mice compared with infection-free mice. In tumor challenge experiments in vivo, we observed that rapid and complete rejection of UVfemale1 cells required the presence of CD8(+) T cells. Under only CD4-depleted situation, survival of tumor cells in schistosome-free mice was prolonged up to 1 month or more. Under the presence of both CD4(+) and CD8(+) cells, S. mansoni infected mice rejected the challenged UVfemale1 cells as was seen in normal mice. However, when CD8(+) cells were depleted from S. mansoni-infected mice, inoculated UVfemale1 cells grew more rapidly than in infection-free mice. Our results suggest that functionally polarized cytokine patterns in schistosome-infected hosts promote rapid tumor growth.