Resistance to reinfection with Schistosoma haematobium in Gambian children: analysis of their immune responses

Abstract

The relationship between reinfection with Schistosoma haematobium and immunological parameters was studied in a group of Gambian children aged from 8 to 13 years. Each individual's exposure to infection was assessed from observations of water contact, cercarial densities and infected snail densities at water contact sites. Eosinophil counts were made and responses to egg antigen (SEA) and adult worm antigen (WWH) measured by ELISA. Low levels of reinfection were associated with a high eosinophil count, high levels of antibodies against WWH and SEA, increased age and low exposure. In a multiple regression analysis of the association of reinfection with eosinophil count, antibody levels, exposure, age and sex, the effects of eosinophil count and exposure were still very significant after allowing for all the other variables. The effects of the antibody levels were close to significance after allowance for exposure and eosinophil count (for WWH: P = 0.09; for SEA: P = 0.07), although the evidence was less clear after additional allowance was made for age and sex. The ability of sera from the children to recognize different parasite antigens was also examined by immunoprecipitation of labelled schistosomulum surface, WWH, SEA and S. haematobium adult worm mRNA in vitro translation products. Schistosomulum surface antigens were recognized by all the sera and there was little variation in this response. There was more variation in their responses to SEA and WWH and a marked heterogeneity in the response to in vitro translation products. However, the pattern of antigen recognition appeared unrelated to susceptibility to reinfection.

Correlation between Eosinophils and Protection against Reinfection withSchistosoma mansoniand the Effect of Human Immunodeficiency Virus Type 1 Coinfection in Humans

“…associated with a resistant phenotype in HIV-1-seronegative individuals, which corroborates findings from several previous studies (2,18,45). Eosinophil activation generally occurs in inflamed tissues (52), but circulating eosinophils from helminth-infected individuals exhibit an activated phenotype, suggesting that parasite infection may up regulate eosinophil function (32,47).…”

“…However, whether IgE is directly involved in protective mechanisms in vivo has not been elucidated, as IgE exerts its effector function through Fc⑀RI-expressing cells. Several studies have demonstrated an association between eosinophilia and host protection against schistosomes (2,18,45), although whether eosinophils express the high-affinity IgE receptor remains under debate (1,3,4,17,21,23,26,40,42,43). Purified human eosinophils are cytotoxic to schistosomula in vitro in the presence of parasite-specific IgE, with eosinophils from helminthinfected individuals having greater potency (11,16,23,50).…”

Full results of the genome-wide scan which localises a locus controlling the intensity of infection by Schistosoma mansoni on chromosome 5q31–q33

“…These observations suggested that human susceptibility/resistance to infection by S. mansoni was genetically determined. [2][3][4][5] To investigate whether a major gene controls human levels of infection by S. mansoni, segregation analysis of infection intensities, adjusted for water contact, age and sex was performed on 20 Brazilian pedigrees comprising 269 individuals, 6 and led to the detection of a co-dominant major gene controlling the infection by S. mansoni. The frequency of the allele predisposing to high infection levels was 0.20-0.…”

CD23-Bound IgE Augments and Dominates Recall Responses through Human Naive B Cells

“…H igh levels of serum parasite-specific IgE are associated with resistance to human schistosomiasis, but the functional significance is undefined (1)(2)(3)(4). Indeed, the bona fide roles of IgE in the human immune system remain elusive.…”