Human eosinophils modulate peripheral blood mononuclear cell response to Schistosoma mansoni adult worm antigen in vitro.

High numbers of eosinophils are observed in parasitic infections and allergic diseases, where they are proposed to be terminally differentiated effector cells that play beneficial role in host defence, or cause harmful inflammatory response. Eosinophils have been associated with killing of schistosomulae in vitro, but there is growing evidence that eosinophils can play additional immuno-regulatory role. Here, we report results of a study that examines peripheral blood mononuclear cell (PBMC) cytokine responses to Schistosoma mansoni adult worm antigen (SWA) when stimulated alone or enriched with autologous eosinophils. Production of the Th-2 type cytokines interleukin (IL)-4, IL-5 and IL-13 was lower (P = 0·017, 0·018 and <0·001, respectively) in PBMC + eosinophil cultures than in PBMC-only cultures stimulated with SWA. Substantial levels of IL-13, IL-10, interferon gamma and tumour necrosis factor alpha were recorded in cultures of eosinophils, but none of these cytokines showed significant association with the observed eosinophil-induced drop in cytokine responses of PBMC. Transwell experiments suggested that the observed effect is due to soluble mediators that downmodulate production of Th-2 type cytokines. This study shows that eosinophils may down-modulate schistosome-specific Th-2 type cytokine responses in S. mansoni-infected individuals. The mechanism of this immune modulation remains to be elucidated.

A late IL-33 response after exposure to Schistosoma haematobium antigen is associated with an up-regulation of IL-13 in human eosinophils.

IL-33, a proposed alarmin, stimulates innate immune cells and Th2 cells to produce IL-13 and is rapidly upregulated upon antigen exposure in murine helminth infection. The human IL-33 response to helminth antigen was analysed in Malians infected with Schistosoma haematobium by disrupting parasite integrity via chemotherapy. Plasma IL-33 was measured pretreatment, and 24 h and 9 weeks post-treatment. At 24 h post-treatment, IL-33 levels were low. Nine week post-treatment IL-33 levels were elevated and were associated with an increase in intracellular IL-13 in eosinophils. Up-regulation of intracellular IL-13 in eosinophils was also associated with eosinophil expression of ST2L, the IL-33 receptor. IL-33 may play an important downstream role in the human response to schistosome adult worm antigen exposure.

Immunity in human schistosomiasis mansoni. Regulation of protective immune mechanisms by IgM blocking antibodies.

After the demonstration of blocking antibodies during rat experimental schistosomiasis, the existence of such factors was investigated in human schistosomiasis. The depletion, in sera from S. mansoni-infected patients, of a given isotype (IgM) either by protein A-Sepharose (PAS) absorption or by fast protein liquid chromatography (FPLC) induced a significant increase in IgG-mediated killing of S. mansoni schistosomula by human eosinophils. Inhibition experiments showed that IgM-enriched fractions (PAS effluents) were able to inhibit eosinophil-dependent cytotoxicity mediated by IgG fractions (total sera or PAS eluates). Both IgG and IgM antibodies from infected human sera immunoprecipitated antigens of 30,000-40,000 Mr in the labeled detergent extracts of schistosomulum surface. The specificity of IgG and IgM for the 38,000 Mr antigen was suggested by competition experiments using two radiolabeled mAbs (IPLSm1, IPLSm3) directed against this antigen. Moreover, crossinhibition between IgG and IgM antibodies for the Mr 38,000 antigen could be directly demonstrated. The in vivo relevance of such IgM blocking antibodies in the context of human immunity to schistosomiasis was evaluated in two groups of children classified as resistant or susceptible to posttreatment reinfection. IgM antibodies specifically directed against the 38,000 Mr antigen were measured by a capture assay. The mean levels of IgM antibodies were significantly higher in the susceptible than in the resistant group both before and after treatment. These results are consistent with the idea that immunity to schistosomiasis could be attributable not only to the existence of antibodies with defined effector function, but also to the absence of blocking antibodies. The description of the existence in human schistosomiasis of antibody isotypes blocking the effector response against defined surface targets might lead to a new understanding of the mechanisms regulating immunity to reinfection against schistosomes and possibly other parasites.

Evidence that cytokine-mediated immune interactions induced by Schistosoma mansoni alter disease outcome in mice concurrently infected with Trichuris muris.

In murine models of Schistosoma mansoni infection, egg production is associated with a switch from T helper cell (Th)1- to Th2-type responses to both schistosome-specific and unrelated antigens. Polyparasitism is common in human populations within S. mansoni endemic areas. We have, therefore, examined whether coinfection with S. mansoni could affect the outcome of a second parasitic infection, through Th2 cytokine-dependent modifications to the host immune response. We find that when mice susceptible to infection with the gut nematode Trichuris muris are coinfected with S. mansoni, they acquire the capacity to resolve T. muris infection, thus demonstrating a resistant phenotype. This ability to expel T. muris is associated with the production of Th2-associated cytokines, and corresponding antibody isotypes, in response to S. mansoni egg antigens. The Th2 response shows that there is no compartmentalization between spleen and mesenteric lymph nodes, and that the expulsion of T. muris is not caused by any changes in the host intestine associated with excretion of schistosome eggs. This influence of schistosome infections may be important, not only for the outcome of infections with unrelated pathogens in endemic areas, but also for the efficacy of vaccines in such areas.

Hepatosplenomegaly associated with chronic malaria exposure: evidence for a pro-inflammatory mechanism exacerbated by schistosomiasis.

In sub-Saharan Africa, chronic hepatosplenomegaly, with palpable firm/hard organ consistency, is common, particularly among school-aged children. This morbidity can be caused by long-term exposure to malaria, or by Schistosoma mansoni, and it is exacerbated when these two occur together. Although immunological mechanisms probably underlie the pathogenic process, these mechanisms have not been identified, nor is it known whether the two parasites augment the same mechanisms or induce unrelated processes that nonetheless have additive or synergistic effects. Kenyan primary schoolchildren, living in a malaria/schistosomiasis co-transmission area, participated in cross-sectional parasitological and clinical studies in which circulating immune modulator levels were also measured. Plasma IL-12p70, sTNF-RII, IL-10 and IL-13 levels correlated with relative exposure to malaria, and with hepatosplenomegaly. Soluble-TNF-RII and IL-10 were higher in children infected with S. mansoni. Hepatosplenomegaly caused by chronic exposure to malaria was clearly associated with increased circulating levels of pro-inflammatory mediators, with higher levels of regulatory modulators, and with tissue repair cytokines, perhaps being required to control the inflammatory response. The higher levels of regulatory modulators amongst S. mansoni infected children, compared to those without detectable S. mansoni and malarial infections, but exposed to malaria, suggest that S. mansoni infection may augment the underlying inflammatory reaction.

Intestinal polyparasitism in a rural Kenyan community.

BACKGROUND: Polyparasitism seems to be a common feature in human populations in sub-Saharan Africa. However, very little is known about its epidemiological significance, its long term impact on human health or the types of interactions that occur between the different parasite species involved. OBJECTIVES: To determine the prevalence and co-occurrence of intestinal parasites in a rural community in the Kibwezi, Makueni district, Kenya. DESIGN: A cross sectional study. SETTING: Kiteng'ei village, Kibwezi, Makueni district, between May and September 2006. SUBJECTS: One thousand and forty five who comprised of 263 adult males, 271 adult females > 15 years of age and 232 boys, and 279 girls <15 years of age. INTERVENTIONS: All infected members of the community were offered Praziquantel (at dosages of 40 mg/kg body weight) for Schistosomiasis and Albendazole (600 mg) for soil transmitted helminths. RESULTS: A total of ten intestinal parasite species (five protozoan and five helminth parasite species) were present in this community and polyparasitsm was common in individuals 5-24 years of age with no gendar related differences. Most of the infections were mild. The protozoan parasites of public health significance present were Entamoeba histolytica and Giardia lamblia with prevalence of 12.6% and 4.2%, respectively. The helminth parasites of public health significance in the locality were Schistosoma mansoni with a prevalence of 28%, and hookworms prevalence of 10%. About 53% of the study population harboured intestinal parasite infections, with 31% of the infected population carrying single parasite species infections, and 22% harbouring two or more intestinal parasite species per individual. Significant positive associations (p values <0.05) were observed between S. mansoni and hookworms, hookworms and Hymenolepis. nana and Entamoeba histolytica and Entamoeba coli. CONCLUSION: Intestinal polyparasitism was common in the Kiteng'ei community, particularly in individuals aged of 5-24 years old. An integrated control programme of approach would be recommended for the control of S. mansoni, hookworms and Entamoeba histolytica for this community.

Comparative epidemiology of Chlamydia trachomatis infection among men attending sexually transmitted disease clinics with and without indication for testing.

Understanding the epidemiology of Chlamydia trachomatis infection in men without indication for testing (without symptoms, signs, or a report of sexual contact with an infected partner) is of crucial importance to reduce the heavy burden of this infection, particularly because this group of men is not usually offered testing in different clinical settings. Using electronic medical records of two STD clinics in Connecticut, 2000-02, this study identified the risk factors of C. trachomatis infection in men with and without indication for testing. In both groups, men who were younger than 30, African-American, or had a prior history of C. trachomatis infection were significantly more likely to be infected. Since a system for routine reproductive health care of young men does not currently exist, health-care providers need to promote an increased awareness of C. trachomatis infection among their male patients who are at increased risk of infection.

Clone banks of cDNA from the parasite Schistosoma mansoni: isolation of clones containing a potentially immunodiagnostic antigen gene.

We have constructed a small vector specifically for blunt-end cloning of fragments of DNA. Both the PvuII site and the EcoRI site allow the detection of recombinants using a simple and inexpensive colour screen. We have used this vector to construct cDNA clone banks from polyadenylated messenger RNA [poly(A)+mRNA] from several life cycle stages of the human parasite Schistosoma mansoni and have identified clones encoding an immunodiagnostic antigen gene by a combination of Southern blotting and mRNA hybrid-selection and in vitro translation. Antibodies against this antigen are only present in patients infected with S. mansoni.

Group B streptococcal meningitis in adults.

Group B streptococcal (GBS) meningitis is a frequent entity in neonates but an uncommon cause of meningitis in adults. Retrospective analysis at our institution identified 4 adult cases over the last 25 years; an additional 46 cases from the literature were reviewed. A bimodal age distribution paralleling that seen in other severe GBS infections was observed. Clinical presentation was not unlike meningitis due to other pyogenic organisms, although a higher percentage of patients presented with less than 24 hours of symptoms. Forty-three percent of patients had no underlying illnesses. Concomitant bacteremia was present in 83% of patients. The overall mortality was 27% and was limited exclusively to patients with co-morbid illnesses. Meningitis in adults due to GBS should be considered in the immunocompetent as well as the immunocompromised host.

Sequence and expression of a major egg antigen from Schistosoma mansoni. Homologies to heat shock proteins and alpha-crystallins.

One of the major proteins of eggs and miracidia (p40) of Schistosoma mansoni has an apparent molecular weight of 40,000 and elicits a strong immune response in over 90% of patients. The antigen consists of a family of at least four near identical proteins, probably encoded by a multi-gene family, and expression of the p40 polypeptides is differentially regulated around the parasite's life cycle. We have isolated and sequenced cDNA clones encoding two variants of the antigen and expressed one p40 clone in Escherichia coli. The fusion protein elicits antibodies which immunoprecipitate p40 and recognise antigens of identical sizes in S. haematobium and S. bovis. The open reading frame encoding this antigen specifies a protein which shares a block of sequence homology with alpha-crystallins and Drosophila small heat shock proteins.

Characterisation of Sm20, a 20-kilodalton calcium-binding protein of Schistosoma mansoni.

A cDNA clone encoding part of a 20-kDa antigen of Schistosoma mansoni (Sm20) has been isolated. The amino acid sequence of this antigen, as predicted from the sequence of the cDNA, has significant homology to the family of calcium binding proteins which include calmodulin, troponin C and the light chain of myosin. Although we have been unable to show any immunological cross-reactivity between Sm20 and calmodulins from a range of other species, we have verified that Sm20 is a functional calcium binding protein. Sm20 is encoded by a small multigene family and is expressed in schistosomula and adult worms but not in eggs. The 20-kDa nascent polypeptide appears to be post-translationally modified to give a 38-kDa species. Sm20 is present in preparations of tegumental membranes and is easily removed from intact schistosomula by detergent treatment, suggesting that it is associated with the tegument. However, the cloned portion does not appear to be exposed on the surface.

Cloning of the gene encoding a 50 kilodalton potential surface antigen of Schistosoma mansoni.

A cDNA library was constructed from the mRNA of adult worms of Schistosoma mansoni, in the expression vector lambda gt11. This library was screened with a pool of sera raised against either soluble egg antigens or purified schistosomulum tegumental membranes. An antiserum raised against the fusion protein of one clone immunoprecipitated a 45 kDa polypeptide from the in vitro translation products of adult worm mRNA and recognised a 50 kDa antigen in homogenates of adult worms. This serum gave positive fluorescence of the surface of schistosomula in indirect immunofluorescence assays and was able to mediate killing of schistosomula by human eosinophils in vitro, suggesting that this clone contained part of a gene encoding a surface antigen.

Schistosoma mansoni cationic egg antigens (CEF6): immunoserology with oxamniquine-treated patients and involvement of CEF6 in the circumoval precipitin reaction.

The serologic activity of a cationic fraction (denoted CEF6) of Schistosoma mansoni soluble egg antigen was compared in an ELISA with that of the unpurified soluble egg antigen for the ability to detect human infections and for the prediction of chemotherapeutic success in patients followed up to 5 years post-treatment with oxamniquine. The cationic fraction correctly identified 100% of 20 patients as infected with S. mansoni; moreover, 50% (10 of 20) seroconverted to negative by 2 years post-treatment and 100% of 15 patients tested were negative 5 years post-treatment. In general, the cationic fraction was superior to the unpurified soluble egg antigen for the detection of infection and for the prediction of chemotherapeutic success. The cationic fraction also exhibited greater immunologic specificity over the unpurified soluble egg antigen in that the latter exhibited higher titers than the former to antibodies against heterologous parasite antigens (Fasciola hepatica, Clonorchis sinensis, Paragonimus westermani adult worms; Trichinella spiralis larvae). Moreover, rabbit antisera raised against egg antigens isolated from the precipitation formed when fresh S. mansoni eggs are incubated with S. mansoni infection of immunization sera (known as circumoval precipitin reactions or COP) reacted strongly with the cationic fraction in ELISA. In addition, antiserum to the cationic fraction as well as antisera against either of the two antigenic components of this fraction, known as antigens alpha 1 and omega 1, all give positive COP reactions when incubated with fresh S. mansoni eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunity and morbidity in Schistosoma mansoni infection: quantitative aspects.

Immunity to Schistosoma mansoni infection in humans can be studied most easily by monitoring serially the intensity of reinfection that occurs among individuals who have undergone chemotherapeutic cure, and whose levels of exposure to contaminated water is subsequently observed. Parallel studies can then be made of those immune responses that are correlated with an observed resistance to reinfection. This paper describes some of the difficulties associated with this approach, with particular reference to the authors' own studies in Kenya, and highlights a possible role of immunoglobulin E antibodies against adult worm antigens in mediating immunity.

Factors affecting high and low human IgE responses to schistosome worm antigens in an area of Brazil endemic for Schistosoma mansoni and hookworm.

We have previously examined the antibody isotype responses to schistosome worm and egg antigens in human populations living in areas of Kenya and the Philippines endemic for Schistosoma mansoni and S. japonicum, respectively. Here, we have analyzed antibody isotype responses to S. mansoni adult worm (AW) antigen and soluble egg antigen (SEA) in more than 500 Brazilian individuals, and found similar relationships with age and sex as in the Kenyan and Filipino populations. Isotype responses to AW antigen broadly increased with age whereas isotype responses to SEA decreased, and a higher proportion of males than females had detectable IgE against AW antigen. Most isotype responses to AW antigen and SEA correlated positively with intensity of infection with S. mansoni except AW antigen-specific IgG2, which correlated negatively. The overall prevalence of infection with S. mansoni in this area was relatively low at only 39.5%; hookworm prevalence was higher at 57.4%. The majority of those infected with S. mansoni were also infected with hookworm (76%). Those individuals with high IgE responses to AW antigen were matched for sex, age, and total IgG to AW antigen as closely as possible with individuals with low levels of AW antigen-specific IgE. The two groups were compared for factors potentially influential in IgE production. No difference was found between the high and low IgE responders for 1) intensity or prevalence of infection with S. mansoni, 2) relative exposure to S. mansoni, 3) number of previous treatments for schistosomiasis, or 4) prevalence of infection with hookworm, but differences were found in other isotype responses to S. mansoni. The high IgE responders had higher IgA and IgG4 against both AW antigen and SEA but lower IgG3 responses to AW antigen than the low IgE responders. The IgE responses to three S. mansoni antigens (paramyosin, Sm22.6, and a 12-kD AW antigen band) were detected in individuals with IgE against AW antigen only.

The stage-, strain- and species-specificity of a Schistosoma mansoni egg antigen fraction (CEF6) with serodiagnostic potential.

The immunological properties of CEF6, a cationic fraction of Schistosoma mansoni egg homogenate (SEA) containing two antigens, omega 1 and alpha 1, have been further investigated in two assays, immunoelectrophoresis (IEP) and enzyme immunoassay (ELISA). Although precipitating antibodies to antigen omega 1 were amongst the first to appear in mice with patient infections, IgG reactivity against CEF6 in ELISA trailed somewhat behind that of IgG activity against unfractionated SEA. Specificity of the two antigens in CEF6 to the egg stage of the parasite life-cycle was demonstrated by the failure of immunizations with cercarial or worm antigens to induce antibodies which reacted against either alpha 1 or omega 1 in IEP, or against CEF6 in ELISA. Mice infected with S. mansoni strains derived from geographically distinct areas, including the Caribbean, South America and Africa, produced antibodies which were reactive against CEF6 prepared from eggs of a Puerto Rican S. mansoni strain that had been maintained in the laboratory for many years. Of the different precipitating anti-SEA antibody species induced by the various S. mansoni strains in mice, those reactive against antigen omega 1 appeared to be present in highest titre. Sera from mice chronically infected with S. japonicum and S. haematobium failed to precipitate CEF6 in IEP and were less reactive with CEF6 than with S. mansoni SEA in ELISA. However, similar degrees of ELISA reactivity against S. mansoni CEF6 and SEA were given by sera from mice infected with S. bovis. The results support the notion that the antigens in CEF6 may be useful in the serodiagnosis of schistosomiasis mansoni infections.

Serodiagnosis of human Schistosoma mansoni infections: enhanced sensitivity and specificity in ELISA using a fraction containing S. mansoni egg antigens omega 1 and alpha 1.

Six fractions of Schistosoma mansoni egg homogenate obtained by cation exchange chromatography were tested in an enzyme-linked immunosorbent assay (ELISA) for their efficacy in serodiagnosis of human S. mansoni infections. One cationic fraction (CEF6) containing egg antigens omega 1 and alpha 1, was found to be highly reactive with a S. mansoni positive reference serum pool. 94 of 95 sera from individuals infected with S. mansoni gave a positive reaction with CEF6, and no cross reactivity was obtained with this antigenic fraction and sera from donors infected with heterologous non-schistosome parasites and cases of avian cercarial dermatitis. Only 10 of 165 sera from patients with S. haematobium and three of 10 sera from patients with S. japonicum were positive with S. mansoni egg CEF6. In one group of patients from West Africa, examined both serologically and parasitologically at a six-monthly interval, the measurement of antibody to CEF6 provided a more sensitive diagnostic aid than stool examination.

Identification and partial purification of an antigen (omega 1) from Schistosoma mansoni eggs which is putatively hepatotoxic in T-cell deprived mice.

T-cell deprived mice heavily infected with Schistosoma mansoni suffer from severe microvesicular damage to hepatocytes within seven weeks of infection. The damage can be prevented by administration of serum (CIS) obtained from mice chronically infected with S. mansoni or from mice immunized with intact or homogenized S. mansoni eggs. Reaction of serum samples from individual chronically infected mice in immunoelectrophoresis with S. mansoni egg homogenate has enabled the identification of at least 12 distinct immuno precipitation reactions. Precipitating antibody against one S. mansoni egg antigen, omega 1, has been detected in all mice with patent chronic infections, and anti-omega 1 antibody is the most concentrated of the precipitating anti-egg antibody species in pooled CIS. Pooled serum obtained from infected intact mice reacting predominantly against omega 1 was found partially to prevent the hepatotoxicity reaction on transfer to infected deprived mice. Serum samples from mice injected with egg homogenate fractionated either by preparative electrophoresis or by cation exchange chromatography, and containing antibodies reactive with antigen omega 1 in immunoprecipitation, were fully protective against liver cell damage induced by S. mansoni in deprived mice. Sera from mice immunized with other S. mansoni egg fractions, and which did not contain antibodies reactive with omega 1, were not hepatoprotective. Antigen omega 1 is compared and contrasted with other S. mansoni egg antigens that have been described.

Immunity after treatment of human schistosomiasis mansoni. I. Study design, pretreatment observations and the results of treatment.

This paper describes the design of a study on immunity to reinfection after treatment of children with Schistosoma mansoni infections, the initial observations on transmission that led to the selection of the study population, the effects of treatment, and the results of immunological tests carried out before and at five weeks after treatment. Iietune village in Machakos District, Kenya, was selected on the basis of high prevalence and intensities of infection in a small preliminary survey, a stable population living in a small area amenable to detailed study, and a lack of previous intervention in the area. Subsequent observations over a pretreatment period of one year confirmed that prevalence and intensities of infection among children attending the local primary school were high. This was associated with extensive contact of members of the community with water-bodies shown to contain large numbers of infected snails. Analysis of pretreatment intensities of infection and water contact patterns in the schoolchildren allowed the selection of 129 children showing a broad scatter between: (a) high intensity, low water contact, and predicted to be non-immune, and (b) low intensity, high water contact, and predicted to be immune. These children were treated with oxamniquine, 30 mg/kg in divided doses. Five weeks after treatment, 70% of children showed apparent complete cure, and the over-all reduction in geometric mean egg output was 98.9%. Since these children represented only a small proportion of the whole community, there was no obvious reduction in transmission, as reflected by snail infection rates, during the following five-month period. Thus, we are in a position to determine whether successfully treated children do or do not become reinfected in a high transmission environment in which it will be possible to make direct estimates of exposure. Immunological tests carried out immediately before treatment were consistent with a pattern of high exposure leading to the early expression of immune responses in most infected children. Eosinophil levels were elevated in 61% of the children, all of whom showed detectable levels of antibodies against adult worm and egg antigens, as measured by ELISA. In addition, all patients showed antibodies capable of mediating eosinophil-dependent killing of schistosomula. At five weeks after treatment, eosinophil counts and anti-adult worm antibody levels had risen, whereas anti-egg antibodies remained grossly unchanged. The wide variation in the levels of responses shown by different individuals will allow us to test whether such responses are associated with resistance to reinfection during the follow-up period.