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Background Immunity that reduces worm fecundity and, in turn, reduces morbidity is proposed for Schistosoma haematobium, a parasite of major public health importance. Mathematical models of epidemiological trends suggest that antifecundity immunity is dependent on antibody responses to adult-worm-derived antigen. Methods For a Malian cohort (age, 5–29 years) residing in high-transmission fishing villages or a moderate-transmission village, worm fecundity was assessed using the ratio of urinary egg excretion to levels of circulating anodic antigen, a Schistosoma-specific antigen that is steadily secreted by adult worms. Fecundity was modeled against host age, infection transmission intensity, and antibody responses specific to soluble worm antigen (SWA), tegument allergen-like 1, and 28-kDa glutathione-S-transferase. Results Worm fecundity declined steadily until a host age of 11 years. Among children, host age and transmission were negatively associated with worm fecundity. A significant interaction term between host age and transmission indicates that antifecundity immunity develops earlier in high-transmission areas. SWA immunoglobulin G1 (IgG1) levels explained the effect of transmission on antifecundity immunity. Conclusion Antifecundity immunity, which is likely to be protective against severe morbidity, develops rapidly during childhood. Antifecundity immunity is associated with SWA-IgG1, with higher infection transmission increasing this response at an earlier age, leading to earlier development of antifecundity immunity. [ABSTRACT FROM AUTHOR]

Background. There is evidence from experimental models that the praziquantel-induced clearance of schistosomiasis is dependent on the host's immune response. Consequently, human immunodeficiency virus (HIV)-related immunodeficiency may impair the effect of praziquantel treatment. Methods. In a prospective cohort study, schistosome-infected subjects who were or were not coinfected with HIV were treated with praziquantel and followed up 3, 6, and 12 months after treatment. Quantitative measures of intensity of schistosomiasis (egg counts and levels of circulating anodic antigen in serum) and immunodeficiency (CD4+ cell counts and viral loads) were collected. Results. Cure rates based on egg counts 3 months after treatment were satisfactory and were similar for HIV-positive individuals (cure rate, 86%) and HIV-negative individuals (cure rate, 85%); the magnitude of decrease in egg count was equal. Cure rates based on circulating anodic antigen levels were much lower than cure rates based on egg counts, with HIV-positive individuals experiencing significantly less clearance of schistosomiasis (cure rate, 31%) than HIV-negative individuals (cure rate, 52%), whereas the magnitude of decrease in circulating anodic antigen was also lower among HIV-positive individuals (P<.01). Conclusion. The effect of praziquantel may be limited to affecting the fecundity of adult schistosomes in the immunocompromised host, thus reducing egg excretion while leaving schistosomes metabolically active, as shown by the fact that levels of antigen production are maintained. Special guidelines for treatment of schistosomiasis in HIV-coinfected individuals may need to be developed. [ABSTRACT FROM AUTHOR]

Background. Schistosoma haematobium infection causes severe urinary disease and considerable mortality. The factors that determine disease progression from mild to severe stages are not fully understood. Methods. Here we describe a cross-sectional epidemiological study of kidney and bladder diseases in 2 Dogon populations with different exposure to S. haematobium infection. Results. Early and high exposure resulted in more-severe disease, especially among young subjects, without clear evidence of a more-rapid development of immunity. Nevertheless, 50%-60% of subjects of all age classes in both villages showed no evidence of disease. Kidney and bladder disease peaked biphasically among young subjects and adults >25 years old. The first peak corresponded with infections of maximum intensity, whereas the second peak occurred among adults with infections of very low intensity. Kidney disease was correlated with circulating anodic antigen concentration in serum, whereas bladder disease was correlated with egg count and eosinophil cationic protein concentration in urine. Kidney and bladder disease did not correlate. Severe kidney disease was more frequent in certain families. Conclusions. The frequency of urinary disease is increased by infections acquired early during life, is regulated by strong clinical immunity in certain subjects, and may be dependent on hereditary factors. Kidney and bladder disease may involve different mechanisms of pathogenesis, which may differ between children and adults. [ABSTRACT FROM AUTHOR]

To determine whether treatment of schistosomiasis has an effect on the course of human immunodeficiency virus type 1 (HIV-1) infection, individuals with schistosomiasis and with or without HIV-1 infection were randomized to receive paraziquantel treatment at inclusion or after a delay of 3 months; 287 participants were included in the study, and 227 (79%) were followed up. Among the 130 participants who were coinfected, those who received early treatment (n = 64) had a significantly lower increase in plasma HIV-1 RNA load than did those who received delayed treatment (n = 66) (P < .05); this difference was associated with no change in plasma HIV- 1 RNA load in the early intervention group (P = .99) and an increase in plasma HIV-1 RNA load in the delayed intervention group (P < .01). Among the 227 participants who were followed up, those who received early treatment (n = 105) had an increase in CD4 cell count, whereas those who received delayed treatment (n = 122) did not (P < .05); this effect did not differ between participants when stratified by HIV-1 infection status (P = .17). The present study suggests that treatment of schistosomiasis can reduce the rate of viral replication and increase CD4 cell count in the coinfected host. [ABSTRACT FROM AUTHOR]

Background. Stunted development and reduced fecundity of Schistosoma parasites in immunodeficient mice and the impaired ability of human immunodeficiency virus 1 (HIV-1)-infected humans to excrete schistosome eggs have been described. This study explores the effect that HIV-1-associated immunodeficiency has on the excretion of schistosome eggs in a large cohort of coinfected individuals. Methods. In a cross-sectional survey, urine and stool samples were obtained from and HIV-1 status was determined for 1545 individuals. More extensive data, including quantitative measures of intensity of infection in schistosomiasis and immunodeficiency, were collected in the Mupfure schistosomiasis and HIV longitudinal cohort, composed of 379 participants of whom 154 were coinfected with HIV-1 and Schistosoma parasites. Results. In the cross-sectional survey, the overall prevalence of schistosomiasis was 43.4%, and 26.3% of the participants were infected with HIV-1. Schistosome infections were due to Schistosoma haematobium in 63.6% of cases, S. mansoni in 18.1% of cases, and dual infections in 18.4% of cases. Intensities of Schistosoma infections, measured by the number of eggs excreted and by the level of circulating anodic antigens, did not differ between HIV-1-negative and HIV-1-positive participants coinfected with S. haematobium, S. mansoni, or both. CD4 cell counts were significantly lower in HIV-1-positive participants and in S. mansoni-infected HIV-1-negative participants than in other participants. Conclusion. The present study suggests that adult HIV-1-related immunodeficiency does not impair the ability to excrete eggs in low-intensity infection with S. haematobium, S. mansoni, or both and that infection with HIV- 1 may not have major implications for diagnosis and surveillance of schistosomiasis. [ABSTRACT FROM AUTHOR]

Specific IgG4 and IgE responses and polyclonal cytokine profiles were studied in 110 Schistosoma haematobium-infected persons before and 5 weeks after chemotherapy. Pretreatment IgG4 responses to soluble egg antigen (SEA) correlated with intensity of infection. After chemotherapy, a significant decrease in egg output and circulating anodic antigen was associated with a substantial drop in the IgG4 response to SEA (IgG4-SEA) in adults and in children, suggesting that egg laying is a major stimulus for IgG4-SEA. After chemotherapy, IgG4 and IgE to adult worm antigen and IgE to SEA increased in children but remained unchanged in adults. This indicates that the immunoregulatory mechanisms operative in S. haematobium-infected adults differ from those in infected children. The effect of treatment on cytokine profiles was determined following stimulation of whole blood with anti-CD3 antibodies. A significant decrease in interleukin-4 production after treatment indicated that reduction in helminth load may lead to a reduced number of Th2-type cells. [ABSTRACT FROM PUBLISHER]

Acquired immune resistance is believed to be largely responsible for age-dependent infection and reinfection patterns in schistosomiasis. In a recently established but intense focus of Schistosoma mansoni in Senegal, the humoral immune response was studied in a random population sample of 289. Antibody levels of various isotypes to schistosome worm and egg antigens were determined by ELISA and related to egg counts (eggs per gram of feces [EPG]), age, and sex. Both IgG1 and IgG4 followed age-related patterns similar to egg counts and strongly correlated with EPG, even after allowing for age. Specific IgE levels increased slowly with age. The humoral immune response patterns in this recently infected population appeared to be largely similar to those in chronically infected communities. Thus far, the observations do not support the current hypothesis that agerelated resistance to Schistosoma is determined by IgE-mediated protective immunity acquired during many years of exposure. [ABSTRACT FROM PUBLISHER]

Levels of IgE, IgM, and IgG subclasses against Schistosoma haematobium adult worm antigen (AWA) and soluble egg antigen (SEA) in a cohort of 148 S. haematobium-infected schoolchildren were determined before and up to 12 months after chemotherapy. Infection intensities were determined as concentrations of circulating anodic antigen (CAA) in serum. One month posttreatment, the antibody levels of all isotypes against AWA were increased, but 1 year after treatment they returned to pretreatment levels. CAA concentrations were positively associated with levels of IgG4 against AWAand SEA but not with levels of IgE. Age correlated negatively with CAA concentrations and positively with levels of IgE to AWA. The balance of anti-AWA IgG4 and IgE was significantly correlated to the CAA concentration, in particular in the older age group (11–13 years). This may suggest that protective immune mechanisms in S. haematobium infections become effective around the age of 12 years. [ABSTRACT FROM PUBLISHER]