Applied field research for comprehensive helminth infection control.

The Institute for Tropical Medicine at University of Tübingen has established 30 years ago in Togo a Research Centre and Onchocerciasis Reference Laboratory (ORL). Onchocerca volvulus infection control and of other neglected tropical diseases has been the focus of activities, and those were performed together with the National Institute of Hygiene in Togo, the Medical Faculty at University of Lomé, national disease control programs and district and regional hospitals. The ORL contributed significantly to the assessment of ivermectin as the prime choice for onchocerciasis treatment, and 24 years of repeated annual treatment with ivermectin has progressively reduced disease prevalence and notably the level of ocular and dermal manifestations of onchocerciasis in the endemic population. The ORL has shown that large parts of the rural population in Togo is concurrently infected with intestinal and intravascular protozoan and helminth parasites, notably school children. The application of repeated treatments with albendazole and praziquantel against Schistosoma spp. and instestinal helminthes for several years has reduced infection intensities by more than 80%. Longitudinal investigations of the cellular immune responses in adults and children have found that parasite co-infections will generate prominent pro-inflammatory responses, and a single or few interventions will not suffice to eliminate co-infections and not establish an appropriately balanced immunity.

Cytokine and chemokine responses in adults, newborns and children exposed to Entamoeba histolytica/dispar, Onchocerca volvulus and Plasmodium falciparum.

Cytokine and chemokine response profiles were studied in newborns, 10-yr-old children and post partum mothers. All study groups were repeatedly exposed to Entamoeba histolytica, Onchocerca volvulus and Plasmodium falciparum infections as indicated by their Immunoglobulin (IgG) responses to parasite-specific antigens. As key indicators for regulatory and pro-inflammatory cytokine and chemokine responses, Interferon (IFN)gamma and regulatory IL-10 were investigated, along with the chemokines MIP-1 alpha/CCL3, MIP-1 beta/CCL4, MDC/CCL22 and TARC/CCL17. Entamoeba histolytica antigens (EhAg) strongly activated pro-inflammatory MIP-1 alpha/CCL3 and MIP-1 beta/CCL4 responses of similar magnitude in mothers, children and neonates alike. Plasmodium falciparum antigens (PfAg) enhanced MIP-1 alpha/CCL3, MIP-1 beta/CCL4 and MDC/CCL22 production in neonates, but did not trigger these chemokines in mothers or 10-yr-old children. Onchocerca volvulus antigens (OvAg) activated IFN-gamma and TARC/CCL17 production in mothers but not in neonates and children. Crude IL-10 production [i.e., without subtracting spontaneous cellular release (baseline)] was highest in mothers and somewhat lower in neonates, while the lowest IL-10 amounts of all were released by peripheral blood mononuclear cells from 10-yr-old children. In summary, strong inflammatory chemokine responses to plasmodia and ameba antigens in newborns and 10-yr-old children suggest that adequately balanced immune regulatory mechanisms may not have developed yet in these age groups and that repeated exposure to parasite infections and immune maturation during childhood is required to generate similar cytokine and chemokine profiles as in adults.

Coinfections with Schistosoma haematobium, Necator americanus, and Entamoeba histolytica/Entamoeba dispar in children: chemokine and cytokine responses and changes after antiparasite treatment.

The effect of polyparasite infections on cytokine and chemokine responses as well as the effect of antiparasite treatment was studied in children without parasite infection (the G0 group), in children singly infected with Schistosoma haematobium (the G1 group), and in children multiply infected with S. haematobium/Schistosoma mansoni, Entamoeba histolytica/Entamoeba dispar, and Necator americanus (the G3+ group). Linear regression analysis disclosed a significant risk for coinfection with hookworm and Schistosoma species. Polyparasite infections detected in 23% of children before treatment were present in 5% at 15 months after treatment. Chemokine responses to S. mansoni adult worm antigen (SmAg) diminished after treatment for macrophage inflammatory chemokine (MIP)-1alpha/chemokine (C-C motif) ligand (CCL)-3 (among G3+ children, by a factor of 200 [95% confidence interval {CI}, 33-1111]) and for MIP-1beta/CCL-4 (among G3+ children, by a factor of 26 [95% CI, 6-117]) but were enhanced for thymus- and activation-regulated chemokine/CCL-17 (among G3+ children, by a factor of 10 [95% CI, 3-32]) (P < .001 for all). In response to E. histolytica antigen, interleukin (IL)-13 levels increased after treatment among G1 children by a factor of 138 (95% CI, 12-1569) and among G3+ children by a factor of 21 (95% CI, 7-64) (P < .001 for both). Cellular production of interferon (IFN)-gamma in response to SmAg decreased 4 weeks after treatment among G3+ children, whereas T helper cell type 2 (Th2) IL-13 production was enhanced among G1 and G3+ children. In summary, polyparasite infections with S. haematobium/S. mansoni, E. histolytica/E. dispar, and N. americanus generated prominent proinflammatory cytokine and chemokine responses, and, after antihelminth treatment, the inflammatory chemokine response lessened as the Th2 responsiveness in coinfected children increased.

Echinococcus multilocularis: inflammatory and regulatory chemokine responses in patients with progressive, stable and cured alveolar echinococcosis.

The progressive growth of Echinococcus multilocularis metacestodes and their tissue infiltration will cause organ malfunction and finally failure. In few patients, E. multilocularis metacestode proliferation will spontaneously regress, but little is known about the determinants which may restrain metacestode survival and growth. In this study, chemokine responses were investigated in E. multilocularis patients at different states of infection, i.e. with progressive, stable and cured alveolar echinococcosis (AE). Characteristic chemokine profiles and changes in their production were observed in AE patients and infection-free controls when their peripheral blood cells were cultured with E. multilocularis antigens. The production of CC and CXC chemokines which associate with inflammation (MIP-1 alpha/CCL3, MIP-1 beta/CCL4, RANTES/CCL5 and GRO-alpha/CXCL1) was constitutively larger in AE patients than in controls; and the elevated chemokine releases were equal in patients with progressive, stable or cured AE. Cluster analyses identified three distinct chemokine response profiles; chemokines were enhanced, depressed or produced in similar quantities in AE patients and controls. A disparate cellular responsiveness was observed in AE patients to viable E. multilocularis vesicles; cluster 1 (GRO-alpha/CXCL1, MCP-3/CCL7, MCP-4/CCL13, TARC/CCL17, LARC/CCL20) and cluster 2 chemokines (PARC/CCL18, MDC/CCL22, MIG/CXCL9) were clearly diminished, while cluster 3 chemokines (MIP-1 alpha/CCL3, MIP-1 beta/CCL4, RANTES/CCL5) augmented. The increased production of inflammatory chemokines in patients even with cured AE could be induced by residual E. multilocularis metacestode lesions which continuously stimulate production of inflammatory chemokines. E. multilocularis metacestodes also suppressed cellular chemokine production in AE patients, and this may constitute an immune escape mechanism which reduces inflammatory host responses, prevents tissue destruction and organ damage, but may also facilitate parasite persistence.

Antibody and cytokine responses in Dracunculus medinensis patients at distinct states of infection.

Dracunculiasis is a promising candidate for eradication, but transmission of Dracunculus medinensis and recrudescence of the disease have been observed repeatedly. In the present investigation, the D. medinensis-specific cellular cytokine response profiles and the parasite-specific antibody subclass reactivity were evaluated in dracunculiasis patients at distinct states of infection. Analysis of the cellular cytokine response in dracunculiasis patients disclosed a D. medinensis antigen-specific depression of IFN-gamma production with patent D. medinensis infection, while the T helper type 2 cytokine IL-10 was similar in patent, post-patent and control individuals, and IL-5 production was always the highest in controls. In parallel, diminished IFN-gamma and IL-12 responses to antigens from Ascaris lumbricoides, Entamoeba histolytica and mycobacteria were observed in patent and post-patent dracunculiasis cases. The parasite-specific IgG(1) and IgG(4) subclass reactivity profiles corresponded with the D. medinensis infection state, and a clear distinction between patent and post-patent patients and controls was found. Overall a depressed cytokine release was observed with patent D. medinensis, which extended beyond the parasite-specific immune responsiveness. The detection of D. medinensis-specific IgG(1) and IgG(4) isotypes may help to distinguish newly exposed, patent and post-patent D. medinensis infections.

Cytokine and chemokine responses in patients co-infected with Entamoeba histolytica/dispar, Necator americanus and Mansonella perstans and changes after anti-parasite treatment.

This study examined the impact of concurrent parasite infections (amoebiasis, filariasis, necatoriasis) and the effect of anti-parasite treatment on cytokine and chemokine responses in singly and poly-parasitized patients. Cellular reactivity and parasite-specific Th1- and Th2-type cytokine and chemokine profiles were investigated before and six weeks after treatment. In those patients infected with three parasite species, cellular secretion of interleukin 5 (IL-5) and IL-12p40 by PBMC was strongly diminished (p<0.005) but IL-10 was elevated in parasite-infected patients (p<0.0001) in response to protozoa- and helminth-specific as well as bacteria-specific antigens. Macrophage inflammatory chemokines (MIP-1alpha/CCL3 and MIP-1beta/CCL4), macrophage-derived chemokine (MDC/CCL22) and neutrophil activating chemokine (IL-8/CXCL8) were produced by PBMC in similar amounts in endemic controls and singly and poly-parasitized patients, but thymus and activation-regulated chemokine (TARC/CCL17) was produced the highest by PBMC from patients with triple parasite infections (p<0.0001). Following anti-parasite therapy, secretion of IL-12p40 and IL-5 augmented significantly in treated patients while IL-10, MDC, MIP-1alpha, TARC and IL-8 substantially diminished (all p<10(-5)) when their PBMC were activated with parasite- and bacteria-specific antigens. In summary, PBMC from poly-parasitized patients responded to protozoa- and helminth-specific antigens with a compromised IL-5 and IL-12p40 but high IL-10 and a substantial chemokine release. Chemokines may attract and activate effector cells in peri-parasitic tissues to limit parasite proliferation and dissemination, while depressed IL-5 and IL-12p40 but prominent IL-10 may prevent eosinophil and cytotoxic cell-mediated inflammatory processes and pathogenesis to the host. The changes in this profile following anti-parasite therapy disclosed the dynamics of an immune adaptation associated with parasite accumulation and also with clearance of parasite infections.