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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.

The recommended control option against onchocerciasis is repeated ivermectin treatment, which will need to be implemented for decades, and it remains unknown how repeated ivermectin therapy might affect immunity against Onchocerca volvulus in the long term. O. volvulus-specific antibody reactivity and cellular cytokine production were investigated in onchocerciasis patients receiving ivermectin (150 microg/kg) annually for 16 years. In treated patients, the T helper type 2 (Th2) cytokine interleukin (IL)-5 and T regulatory IL-10 in response to O. volvulus antigen (OvAg) and bacteria-derived Streptolysin O (SL-O) diminished to levels found in infection-free endemic controls; also, cellular release of Th1-type interferon (IFN)-gamma at 16 years post initial ivermectin treatment (p.i.t.) approached control levels. In ivermectin-treated onchocerciasis patients, IL-5 production in responses to the mitogen phytohaemagglutinin (PHA) decreased, but IL-10 in response PHA increased, and neither attained the cytokine production levels of endemic controls. At 16 years p.i.t., O. volvulus-specific IgG1 and IgG4 subclass reactivity still persisted at higher levels in onchocerciasis patients than in O. volvulus exposed but microfilariae-free endemic controls. In addition, cytokine responses remained depressed in onchocerciasis patients infected concurrently with Mansonella perstans and Necator americanus or Entamoeba histolytica/dispar. Thus, long-term ivermectin therapy of onchocerciasis may not suffice to re-establish fully a balanced Th1 and Th2 immune responsiveness in O. volvulus microfilariae-negative individuals. Such deficient reconstitution of immune competence may be due to an as yet continuing and uncontrolled reinfection with O. volvulus, but parasite co-infections can also bias and may prevent the development of such immunity.

Infection with the cestode Echinococcus multilocularis causes human alveolar echinococcosis (AE), a life-threatening disease affecting primarily the liver. Despite the severity of AE, clinical symptoms often develop only many years after infection, which suggests that E. multilocularis has developed mechanisms which depress anti-parasite immune response, thus favouring immune evasion. In this study we examined the production of cytokines, chemokines and the expression of CD molecules on peripheral blood mononuclear cells (PBMC) from AE patients and healthy controls in response to E. multilocularis metacestode culture supernatant, viable E. multilocularis vesicles and E. multilocularis vesicle fluid antigen in vitro. After 48 h of co-culture, E. multilocularis metacestode culture supernatant and E. multilocularis vesicles depressed the release of the proinflammatory cytokine interleukin (IL)-12 by PBMC. This effect was dose-dependent and a suppression of tumour necrosis factor (TNF)-alpha and IL-12 was observed even when PBMC were activated with lipopolysaccharide (LPS). Comparing proinflammatory cytokine release by AE patients and controls showed that the release of IL-12 and TNF-alpha was reduced in AE patients, which was accompanied by an increased number of CD4+ CD25+ cells and a reduced release of the Th2 type chemokine CCL17 (thymus and activation regulated chemokine, TARC), suggesting an anti-inflammatory response to E. multilocularis metacestode in AE patients. Instead the production of interferon (IFN)-gamma and the expression of CD28 on CD4+ T cells were increased in PBMC from AE patients when compared to controls. This was accompanied by a higher release of the Th2-type chemokine CCL22 (macrophage derived chemokine, MDC) supporting that E. multilocularis also generates proinflammatory immune responses. These results indicate that E. multilocularis antigens modulated both regulatory and inflammatory Th1 and Th2 cytokines and chemokines. Such a mixed profile might be required for limiting parasite growth but also for reducing periparasitic tissue and organ damage in the host.

Ivermectin treatment will effectively diminish microfilariae (Mf) of Onchocerca volvulus in the skin of patients, but therapy is associated with adverse host inflammatory responses. To investigate the association of proinflammatory chemokines with the intensity of infection and clinical adverse reactions, chemokine serum levels were measured in patients following ivermectin treatment (100 microg/kg, 150 microg/kg or 200 microg/kg) or placebo. The density of O. volvulus Mf per mg skin decreased by 85%, 97%, 97% and 90% at day 3, at month 3, month 6 and at 1 year post-ivermectin. The cutaneous T cell-attracting chemokine (CTACK/CCL27) was found highly elevated in onchocerciasis patients compared to infection-free European controls (P = 0.0004) and it did not change following ivermectin or placebo to 1 year post-therapy. The chemokine RANTES/CCL5 (regulated on activated and normally T cell-expressed) was similarly high in onchocerciasis patients and infection-free European controls; the RANTES/CCL5 levels did not change following treatment until 6 months post-therapy but were slightly elevated at 1 year post-therapy (P < 0.02). In contrast, the Th2-type chemoattractants, thymus and activation regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22), were activated at 3 days post-ivermectin (P < 0.0001) to return to pretreatment or lower levels thereafter. The Th1-type chemoattractants, macrophage inflammatory protein (MIP)-1alpha/CCL3 and MIP-1beta/CCL4 were low before ivermectin treatment, but following clearance of microfilariae of O. volvulus their levels increased from 6 months post-therapy onwards (for both at 12 months post-therapy, P < 0.0001). The adverse reaction scores (RS) in treated patients increased significantly on day 3 (P < 0.02) while it remained unchanged in those who received placebo (P = 0.22); RS interacted with the microfilarial density (P = 0.01), but not with the dose of ivermectin or with the serum levels of MIP-1alpha/CCL3, MIP-1beta/CCL4, TARC/CCL17, MDC/CCL22 and CTACK/CCL27. Our observations suggest that following ivermectin, macrophages as well as memory Th2-type lymphocytes and B cells, attracted and activated by MDC/CCL22, TARC/CCL17 and CTACK/CCL27, may contribute to dermal immune responses and O. volvulus Mf killing and clearance. The transient changes of TARC/CCL17 and MDC/CCL22 were not associated with clinical adverse responses, and the later rise of MIP-1alpha/CCL3 and MIP-1beta/CCL4 showed a reactivation of Type 1 immune responses associated with persistent low levels of O. volvulus microfilariae and an expiring O. volvulus infection.

The modulation of human immune response by filarial parasites has yielded contradictory experimental findings and attracted much controversy. We address the unresolved question of acquisition, establishment and accumulation of Onchocerca volvulus by using a modelling approach that relates computer simulations to cross-sectional data concerning parasite burdens in 913 West African onchocerciasis patients. It is shown that the acquisition of O. volvulus is not constant with host age; instead, the analysis of age profiles of parasite burdens strongly indicate the operation of immunosuppressive processes within the human host, associated with the presence of adult parasites or microfilariae. It is suggested that these processes suppress immunity against incoming infective larvae (L3), which themselves act as an immune modulating component once they have successfully overcome the barrier of concomitant immunity. Suppression of parasite-specific immunity leads to parasite establishment rates which increase along with the parasite burden, but which hardly depend on hyperendemic annual transmission potentials. Children, still immunocompetent due to low parasite burdens, acquire 0.1-0.5 adult female parasites per year, whereas older people, immunosuppressed due to high burdens, acquire 2-4 adult female parasites per year. Differences in parasite establishment between the forest and the savannah strains of O. volvulus are quantified and dynamic aspects of density-dependent parasite establishment discussed.

This study investigated the effect of maternal Onchocerca volvulus infection on humoral and cellular responsiveness in newborn children and their mothers. Onchocerca volvulus-specific IgG isotypes and IgE were significantly elevated in infected mothers and their infants. One year post partum, O. volvulus-specific IgG4 was strongly reduced in children of infected mothers, while IgG1 responses weakened only slightly. Umbilical cord mononuclear blood cells (UCBC) and peripheral blood cells (PBMC) from mothers proliferated in response to phytohaemagglutinin (PHA), concanavalin A (Con A), and the bacterial antigens streptolysin-O (SL-O) or purified protein derivative (PPD). UCBC from neonates born to O. volvulus-infected mothers responded lower (P < 0.01) to Con A (at 5 micrograms/ml), PPD (at 10 and 50 micrograms/ml) and O. volvulus-derived antigens (OvAg) (at 35 micrograms/ml), and in parallel, a diminished cellular reactivity (P < 0.01) by PBMC was observed to OvAg in mothers positive for O. volvulus. Several Th1-type (IL-2, IL-12, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha)) and Th2-type (IL-4, IL-5, IL-10, IL-13) cytokines were secreted by UCBC and PBMC in response to OvAg, bacterial SL-O and PHA. OvAg did not stimulate IL-2 and none of the mitogens or antigens induced production of IL-4 in neonates. In response to OvAg, substantially elevated (P < 0.01) amounts of IFN-gamma were produced by UCBC from newborns of O. volvulus-infected mothers. UCBC secreted low levels of IL-5 and IL-13, while higher amounts of IL-10 were found (P < 0. 01) in newborns from onchocerciasis-free mothers. In conclusion, maternal O. volvulus-infection will sensitize in utero parasite-specific cellular immune responsiveness in neonates and activate OvAg-specific production of several Th1- and Th2-type cytokines.

Chronic and generalized onchocerciasis is associated with suppression of the parasite-specific cellular responsiveness, while exposed individuals without parasitological and clinical evidence of infection (endemic normals) display prominent cellular reactivity to Onchocerca volvulus antigens (OvAg). In order to identify those parasite antigens which may account for this differential cellular responsiveness, total adult worm-derived OvAg were fractionated by means of preparative SDS-PAGE and blot-elution into 22 antigen fractions of continuously decreasing molecular weight. Peripheral blood mononuclear cells (PBMC) from microfilariae (mf)-positive onchocerciasis patients (n = 18) proliferated weakly in response to all OvAg fractions. In contrast, in vitro reactivity of PBMC from endemic normals (n = 9) was depressed in response to OvAg of mol. wt 200-30 kD only, while antigens of mol. wt < 30 kD induced vigorous proliferation in these individuals compared with the microfilaridermic patients (P < 0.05). Highest proliferative reactivity of cells from endemic normals was observed in response to OvAg of mol. wt 15-11 kD. Furthermore, these low mol. wt antigen fractions induced substantial production of IL-2 and interferon-gamma (IFN-gamma) in PBMC from endemic normals, but not in those from onchocerciasis patients. Cells from individuals of both groups secreted similar amounts of IL-5 in response to all OvAg fractions, with highest production again being induced by low mol. wt OvAg. In contrast, PBMC from onchocerciasis patients clearly produced more IL-10 than did cells from endemic normals. This augmented IL-10 production by PBMC from mf-positive individuals was not only observed after stimulation with OvAg fractions, but was measured in unstimulated control cultures as well. IFN-gamma-specific mRNA in antigen-stimulated PBMC from endemic normals appeared to be more prominent than in cells from onchocerciasis patients. However, mRNA transcripts of IL-10 and IL-13 were clearly present in patients, but were absent or inconsistently observed in endemic normals. Our results suggest that vigorous Th1-type cellular responsiveness encountered in endemic normals is restricted to low mol. wt antigens of O. volvulus, while such reactivity will not be present in mf-positive individuals. Furthermore, spontaneous production of high levels of IL-10 in onchocerciasis patients is likely to suppress Th1-type immunity, and thus may favour manifestation of chronic onchocerciasis. These traits of cellular immunity may contribute to the differential outcome of O. volvulus infection, the manifestation of clinical disease, and may also regulate the build up of acquired immunity in humans.

Peripheral blood mononuclear cells (PBMC) from 8 onchocerciasis patients, treated or not with ivermectin, were analyzed for phenotypic cell surface markers. A significant increase (P < .05) in gamma/delta T cells expressing the V delta 1 chain compared with normal and endemic controls was detected in all patients. PBMC populations from onchocerciasis patients were not expanded after restimulation with Onchocerca volvulus antigens in vitro, but both V delta 1 and V delta 2 T cells from normal donors were increased significantly in response to O. volvulus and Mycobacterium tuberculosis (P < .05), respectively. Frozen sections of all 5 onchocerca nodules tested demonstrated an increased number of CD3+ cells in the vicinity of the adult worm, in all cases expressing the alpha/beta T cell receptor and in 2 patients also expressing the gamma/delta T cell receptor; 60% of T cells expressed the activation marker Ki67. These data suggest that O. volvulus provides ligands to V delta 1 T cells.

As part of an ivermectin dose-ranging study of onchocerciasis patients in Togo, 55 onchocerciasis patients with concomitant mansonelliasis received single oral doses either of ivermectin (100 to 200 micrograms/kg body weight) or placebo. As expected, Onchocerca volvulus microfilariae in the skin were greatly reduced in number soon after drug treatment, but microfilariae of Mansonella perstans reacted differently. Microfilarial densities of M. perstans were assessed with a filtration technique both before, and 4 times after, treatment. In untreated patients microfilarial densities were stable until the end of the study at 6 months. In patients receiving ivermectin, microfilarial densities dropped on average to less than 60% of the pre-treatment level and remained there until the final post-treatment examination. This partial reduction was probably not caused by a microfilaricidal effect of ivermectin, but rather by an altered distribution of microfilariae in the peripheral blood and in a suspected microfilarial reservoir.

A longitudinal investigation has been conducted into the cell-mediated immune responses of onchocerciasis patients after a single-dose treatment with ivermectin. Untreated patients tested for delayed cutaneous hypersensitivity (DCH) to seven recall antigens showed lower responses than infection-free control individuals (P less than 0.01), but 6 and 14 months after treatment DCH reactions increased to similar levels to those seen in the controls. The in vitro cellular reactivity to Onchocerca volvulus-derived antigen (OvAg) was reduced in untreated patients as compared with controls, and the lymphocyte blastogenic responses to OvAg and streptolysin-O clearly improved up to 14 months after treatment. Peripheral blood mononuclear cells (PBMC) from untreated patients produced IL-1 beta, tumour necrosis factor-alpha (TNF-alpha) and IL-6 in response to mitogenic stimulation with phytohaemagglutinin (PHA), only low levels of IL-1 beta, IL-2 and TNF-alpha in response to OvAg, but higher amounts of IL-4 and interferon-gamma (IFN-gamma) in response to OvAg than control individuals. After ivermectin treatment, the OvAg-induced production of IL-1 beta and TNF-alpha increased significantly 1 and 14 months after treatment. The PHA-induced production of IL-2 and IL-4 increased 1 month after treatment and remained significantly elevated until 14 months after treatment, whereas the OvAg-specific secretion of IL-2, IL-4 and IFN-gamma did not change after ivermectin treatment. Flow cytometric analysis of lymphocyte-subsets in the peripheral blood of untreated patients revealed a relative and absolute (P less than 0.01) diminution of CD4+ cells and a significantly smaller CD4+/CD8+ cell ratio as compared with controls. By 4 weeks after treatment and thereafter, CD4+ T cells increased relatively and absolutely (P less than 0.01); likewise there was an absolute increase in T-helper-inducer cells (CD4+CD45RO+) and a temporarily improved CD4+/CD8+ cell ratio (P = 0.001). The expression of the low-affinity receptor for IgE (CD23) on total lymphocytes decreased from 14% to 7% by 14 months after treatment. The CD8+ cells and CD3+TCR gamma delta + cells were higher in patients than in controls and both remained elevated until 14 months after treatment. These results suggest a distinctly improved cellular immunity in human onchocerciasis that was facilitated by ivermectin therapy.

Ethanol-fixed Onchocerca nodules and skin snips were successfully digested with collagenase to assess the parasite load. The importance of this technique for investigations in the field is discussed.

Ivermectin (MK-933) has been compared with diethylcarbamazine (DEC) and placebo in a double-blind study in 30 adult male Senegalese patients with Onchocerca volvulus infection. 10 patients were randomly assigned to each treatment group. Ivermectin was administered as a single oral dose of 12 mg and DEC as 50 mg daily for two days and 100 mg twice daily for the following six days, total 1.3 g in eight days. Skin O. volvulus microfilaria densities remained near pre-study values in the placebo patients, but decreased rapidly with both active drugs to mean values about 2% of pretreatment (Day 8) and then increased slowly, reaching in 12 months about 4% of pre-treatment (ivermectin) and 18% (DEC). This difference is statistically significant. Clinical adverse reactions were recorded in four ivermectin, ten DEC and three placebo patients. One ivermectin and six DEC patients received steroid treatment for relief of these reactions. Serious adverse ocular changes were not seen in any patients, possibly because of the steroid therapy in the DEC patients. Adult O. volvulus from onchocercal nodules one and six months after treatment showed no effect of either drug on viability. Intra-uterine developing forms of the microfilariae appeared normal in all three treatment groups at the one month examination but deformed and degenerated forms were evident at six months in the ivermectin group but not in the DEC and placebo patients. Ivermectin as a single oral dose appears to be a safer and more effective microfilaricidal drug in human onchocerciasis than DEC in the standard multi-dose regimen.

Adult Onchocerca volvulus were enzymatically isolated with collagenase from excised nodules and kept in TC medium 199 with Hank's salts supplemented with various sera. Male and female worms survived in the culture medium and 10% human serum on average for about 11 days (maximum 28 days) and 14.5 days (maximum 42 days). Up to 4,000 microfilariae were expelled by each female per day, but the production of new oocytes or development of embryos could not be observed in vitro.