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PubMed1991

Ultrastructure of the digestive tract of Echinostoma revolutum cercaria.

The digestive tract of a fully formed free-swimming cercaria of Echinostoma revolutum (Froelich, 1802) Dietz, 1909 was studied by electron microscopy. The oral sucker and pharynx are covered by a tegument. The oesophagus and the caeca are not luminized. They are packed with giant epithelial cells with electron-dense granules of irregular shape, rough endoplasmic reticulum and its cisterns, and Golgi apparatus. The tegument of the oral sucker cavity contains numerous uniciliate receptors.

Animals↗
PubMed1990

The role of antibody affinity and titre in immunity to Schistosoma mansoni following vaccination with highly irradiated cercariae.

Sera from rabbits and rats vaccinated with highly irradiated cercariae of Schistosoma mansoni (VRabS, VRatS) were found to be of substantially higher affinity than sera from CBA mice vaccinated four times (4 X CVMS), single sex sera (SSS) or chronic infection sera (CIS). In contrast, VRabS and SSS appeared to possess the highest titres of antibody, followed by CIS and VRatS, with 4 X CVMS displaying the lowest titre. Two mouse strains selectively bred for high-affinity (HA) or low-affinity (LA) antibody following vaccination were tested for their ability to resist a challenge infection. LA mice, which produce high titres of low-affinity antibody, manifested significantly more resistance than HA mice, which produce low titres of high-affinity antibody. Immunoprecipitation studies demonstrated that sera from vaccinated LA mice (LVMS) recognized 125I-labelled schistosomular surface antigens more intensely than sera from vaccinated HA mice (HVMS). However, peritoneal macrophages from HA and LA mice in the presence of HVMS, LVMS or 4 X CVMS, and naive macrophages activated in vitro with interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS) mediated comparable levels of schistosomula killing in vitro. The experiments described here provide evidence that the titre of antibody rather than its affinity may be a more critical factor in the development of optimal immunity to S. mansoni.

Animals↗
PubMed1990

[Studies on the dynamic changes in specific antibodies in sera from animals infected with unisexual and bisexual cercariae of Schistosoma japonicum].

The IEST using both liver tissue-egg frozen section of mice infected with Schistosoma japonicum and adult worm frozen section of Schistosoma japonicum (TEFS-IEST and AWFS-IEST) were performed to study the dynamics of specific antibodies in sera from rabbits infected with unisexual and bisexual cercariae of Schistosoma japonicum. Both peaks of specific antibodies appeared at the 10th week after infection. The levels of specific antibodies were much higher in bisexual infection than in unisexual infection and closely related to the intensity and duration of infection. The levels of anti-egg antibodies were higher than those of anti-adult worm antibodies. The serological reactivity of egg antigen is higher than that of adult worm antigen. TEFS-IEST shows higher sensitivity and specificity than AWFS-IEST and DGS-COPT for the diagnosis of schistosomiasis.

Animals↗
PubMed1989

The ability of fractionated sera from animals vaccinated with irradiated cercariae of Schistosoma mansoni to transfer immunity to mice.

To study the role of IgG and IgM isotypes found in sera of mice or rabbits immunized with irradiated cercariae in schistosome immunity, the respective sera were fractionated by protein A chromatography. Both the protein A-bound and unbound fractions of vaccinated mouse serum (VMS) showed reactivities in ELISA assay using NP-40 membrane extracts of 3-hr schistosomula as antigens and in indirect immunofluorescence assay (IIF) using live 3-hr schistosomula. Both the protein A-bound and unbound fractions possessed high levels (84% and 76%, respectively) of complement-mediated cytotoxicity against schistosomula in vitro. The IgG- and IgM-containing fractions each conferred passive protection (30% and 20%) against challenge infection, although at a lower level when compared to unfractionated VMS (42%). These data demonstrate that in the mouse model both IgG and IgM can recognize epitopes on the surface of schistosomula, mediate cytotoxicity in vitro, and provide passive protection in vivo. Similarly, the protein A-bound and unbound fractions of vaccinated rabbit serum (VRS) were also shown to be positive in ELISA and IIF. The IgG- and IgM-containing fractions each possessed high levels (95% and 85%, respectively) of complement-dependent cytotoxicity against schistosomula in vitro. In contrast to VMS fractions, the IgG fraction of VRS conferred a similar level (28%) of in vivo protection as unfractionated VRS when injected into mice no later than 6 days after challenge. Moreover, the IgG fraction of VRS was still able to provide passive protection to mice when given as late as 15 days postinfection, but failed to confer protection when injected at 24 or 35 days postinfection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Dermal responses of various hosts to infection with Schistosoma japonicum cercariae].

The present investigation concerns with the dermal reactions produced in various host species by the invading schistosomula in primary infection. Eight animal species including mouse, rat, hamster, jird, guinea pig, rabbit, rhesus monkey and pigeon were used. A small area of abdominal skin exposed to 300 Schistosoma japonicum cercariae was taken at different time intervals from each animal species.

Animals↗
PubMed1989

Ultrastructure of the tail of Echinostoma revolutum cercaria.

The ultrastructure of the tail fins and muscles of Echinostoma revolutum cercaria is described. The longitudinal muscles consist of a primitive type of transversely striated muscle fibres with a well-developed sarcoplasmic reticulum in the Z-band. The fins are formed by a longitudinal tegument fold containing the same components as the remaining part of the tail tegument. The difference between the body and tail tegument is discussed.

Animals↗
PubMed1989

The effects of host distributional patterns on parasite transmission: Aedes aegypti larvae and Plagiorchis noblei Cercariae.

The effects of distributional patterns of the host on the acquisition of Plagiorchis noblei cercariae by Aedes aegypti larvae were determined. Mosquito larvae that were allowed to disperse were more susceptible to infection than confined larvae. Because these mosquito larvae are known to aggregate in light and disperse in darkness, they are more likely to acquire P. noblei infections at night. The timing of cercarial emergence in relation to the distributional patterns of the mosquito host is discussed.

Aedes↗
PubMed1988

Immunity to Schistosoma mansoni in guinea-pigs vaccinated with radiation-attenuated cercariae. T-cell activation of macrophages for larval killing.

This study addresses macrophage activation in guinea-pigs vaccinated with radiation-attenuated cercariae of Schistosoma mansoni. Peritoneal exudate macrophages elicited in vaccinated animals by mineral oil injection were activated to kill larval schistosomes in vitro. Killing efficiency is dependent upon the cell: target ratio employed and is enhanced by, but is not strictly dependent on, the presence of specific antibodies. Macrophages co-cultured with parasites release superoxide radicals and hydrogen peroxide, but the use of inhibitors has shown that neither of these reactive oxygen intermediates are the causal agents of cellular cytotoxicity in this system. Oil-elicited macrophages from naive guinea-pigs do not show comparable activation; they can, however, be activated in vitro by incubation with culture supernatant fluids from schistosome antigen-stimulated spleen, or lymph node cells harvested from vaccinated guinea-pigs. Naive macrophages activated in this way kill schistosomula in vitro and release the activation markers IL-1 and superoxide anion. The macrophage-activating factor (MAF) present in spleen cell culture supernatant fluids has a MW of 35,000-55,000, but does not have the chemical characteristics of gamma-interferon. In this study MAF is shown to be released by a population of lymph node cells that does not adhere to nylon-wool columns, that responds well in proliferation assays to schistosome antigens and to the T-cell mitogen concanavalin A, but does not respond to the B-cell mitogen lipopolysaccharide. These cells have been identified as small lymphocytes.

Animals↗
PubMed1977

Immune responses during human schistosomiasis mansoni. I. In vitro lymphocyte blastogenic responses to heterogeneous antigenic preparations from schistosome eggs, worms and cercariae.

In vitro lymphocyte blastogenesis assays were performed using peripheral blood lymphocytes obtained from patients with schistosomiasis mansoni. Their infection was well characterized both clinically and in regard to the duration and intensity of Schistosoma mansoni infection. Subjects who were either not infected with any helminths or who were negative for S. mansoni but infected with other helminths provided two control groups. Cultures were exposed to various concentrations of heterogeneous soluble antigens prepared either from S. mansoni eggs, worms, or cercariae. In this series there was no statistical correlation between the intensity of infection (as determined by eggs/ml of feces) and the degree of cell-mediated reactivity observed by lymphocyte blastogenesis to any of the antigenic preparations. Individual patient lymphocyte responsiveness varied considerably. However, analysis of the data by groups, based upon the longevity of their S. mansoni infection, demonstrated different patterns of reactivity in regard to the antigen preparations. Responses to the egg antigens were only present early in infection. In contrast, reactivities stimulated by either the worm or cercarial preparations increased in a direct relationship to the duration of S. mansoni infection.

Antigens, Heterophile↗
PubMed1986

Passive transfer with serum and IgG antibodies of irradiated cercaria-induced resistance against Schistosoma mansoni in mice.

The role of humoral immunity to Schistosoma mansoni infection in C57BL/6J mice was examined by employing a passive transfer system. Sera from highly resistant mice that had been exposed to two or three immunizations with 50-kilorad-gamma-irradiated cercariae were tested for their ability to transfer protection against S. mansoni challenge. All five batches of serum tested were observed to have protective activity. Immune serum recipients exhibited statistically significant reductions in challenge worm burdens of 20 to 50% compared with recipients of normal serum or no serum. The most consistent level of resistance was obtained when immune serum was administered several days post-challenge, i.e., at a time coincident with schistosomulum residence in the lungs. Furthermore, it was shown that the protective activity in immune serum was associated with factors that bind to staphylococcal protein A and that are precipitated by 50% ammonium sulfate; thus it appears that the protective factors in immune serum are IgG antibodies.

Animals↗
PubMed1986

Laboratory transmission of Schistosoma mansoni in brackish waters; survival and infectivity of cercariae.

Schistosoma mansoni cercariae were exposed to various dilutions of sea water, both in the absence and in the presence of mice. It was found that whereas 100% and 75% sea water were lethal to the parasites, the parasites survived in lower concentrations of sea water. The lower the concentration the longer was the survival time. Similarly, the rate of infection of mice decreased as the concentration of the sea water increased.

Animals↗
PubMed1987

Immunity to schistosomiasis mansoni in guinea-pigs vaccinated with radiation-attenuated cercariae: I. Humoral responses against skin-stage schistosomula.

The anti-schistosomular humoral responses of guinea-pigs vaccinated with radiation-attenuated cercariae of Schistosoma mansoni have been investigated in vitro. The sera of vaccinated animals contain schistosomulicidal complement-fixing antibodies which peak in titre at week 5 after vaccination and predominantly consist of IgG2 and IgM antibodies. The ability of the serum to arm macrophages from normal animals to bind to schistosomula, also peaks in titre at week 5 and is associated with IgG2 antibodies. Basophils from normal animals can be sensitized in vitro by vaccine serum to degranulate in the presence of schistosomular antigens. This anaphylactic antibody activity is associated with IgG1 but not IgE antibodies, and peaks in titre at week 10. Three antigens (14 kD, 20 kD and 43 kD) are specifically and transiently detected by vaccine serum on Western blots of schistosomular proteins; these antigens are first discernible at week 4, but were virtually undetectable at week 12.

Animals↗
PubMed1987

Schistosoma mansoni polypeptides immunogenic in mice vaccinated with radiation-attenuated cercariae.

We compared the humoral immune response of mice protected against Schistosoma mansoni by vaccination with radiation-attenuated cercariae to that of patently infected mice, and we identified antigens that elicit a greater, or unique, immune response in the vaccinated mice. These comparisons were based upon radioimmunoprecipitations and immunodepletion of [35S]methionine-labeled schistosomular and adult worm polypeptides, followed by one- and two-dimensional polyacrylamide gel analyses. The humoral responses of patently infected mice and of mice vaccinated once were remarkably similar and were directed against schistosome glycoproteins ranging in molecular size from greater than 300 to less than 10 kDa. Exposing mice to a second vaccination resulted in a marked change in the immune response, to one predominantly directed toward high molecular size glycoproteins. Sequential immunodepletion techniques identified five schistosomular and seven adult worm antigens that showed a greater or unique immunogenicity in vaccinated mice as compared with patently infected mice. These adult worm antigens were purified by preparative sequential immunoaffinity chromatography and used to prepare a polyclonal antiserum, anti-irradiated vaccine. This antiserum bound to the surface of live newly transformed and lung-stage schistosomula, as assessed by immunofluorescence assays, and was reactive with a number of 125I-labeled schistosomular surface polypeptides, including a doublet of 150 kDa that was also recognized by sera of vaccinated mice but not by sera of patently infected mice.

Animals↗
PubMed1987

Ultrastructure of a new type of sensory ending in Echinostoma revolutum cercaria (Trematoda: Echinostomatidae).

Two pairs of hitherto unknown multiciliate sensory endings have been demonstrated in free-swimming cercariae of Echinostoma revolutum using transmission and scanning electron microscopy. This type of receptor consists of a bundle of 36--40 short, conically projecting cilia ensheathed by a collar formed by a circular evagination of tegument in shape of a cup. The cilia projecting from the centre of a widened nerve fibre, filled with electron-lucid vesicles, possess a well developed basal body and do not contain a ciliary rootlet. The function of this receptor is discussed.

Animals↗
PubMed1987

[Comparative analysis of the rhythm of cercariae emergence in three strains of Schistosoma bovis (trematoda: Schistosomatidae)].

A comparative experimental study of the rhythmic shedding of three geographic strains of Schistosoma bovis cercariae (Sardinian, Sudanese and Spanish) by Bulinus truncatus showed a significant difference in the emergence patterns. The results support the existence of a genetic variability of the emergence rhythms. The origin of the variability is discussed and could be found in the pastoral practice and the ecological characteristics of the different transmission foci.

Animals↗
PubMed1986

Histochemistry of the cercaria of Orientobilharzia turkestanica (Skrjabin, 1913).

Four types of gland cells--escape, head, praeacetabular and postacetabular--were demonstrated by histochemical methods in the cercaria of Orientobilharzia turkestanica. The secretion of the head gland contains proteins with cystine and phospholipids. It exhibits the acid phosphatase activity. The secretion of the escape glands contains proteins with cystine and cysteine and the secretion of the postacetabular gland cells proteins with cystine, cysteine and tyrosine, and neutral and acid mucosubstances.

Animals↗
PubMed1977

[Differences in the sensilla of African and American cercaria of Schistosoma mansoni, the agent of human intestinal bilharziasis].

Schistosoma mansoni parasite of the human intestinal bilharziasis is frequently transmitted in Africa by the Snail Biomphalaria pfeifferi and in America by Biomphalaria glabrata. The comparison between four African strains of cercariae obtained from Biomphalaria pfeifferi and five American strains from Biomphalaria glabrata points out variations in the number and arrangement of the sensory receptors.

Animals↗