الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
Cercarial antigens, including Gx, represent the first contact between
potentially immunogenic material and the host. These antigens elicit a host
immune response whose outcome is currently not completely defmed. The
glycocalyx (Gx) of the cercarial stage is one of the prominent proteoglycans of
schistosomes. It is a dense 1-2 urn outer coating consisting mainly of high
molecular weight carbohydrates. The Gx is rapidly shed from the surface of
transforming schistosomules and does not reappear for the remainder of the lifecycle.
The Gx is antigenic and activates complement. Also, the Gx is recognized
by monoclonal antibodies that are protective in passive transfer experiments, by
antibodies found during natural infection, and by antibodies raised against egg
antigens. However, the medium in which cercariae have been transformed to
schistosomules in vitro was found to suppress in vii ro proliferation of peripheral
blood lymphocytes in response to mitogens. Further, immunization with a crude
preparation ofGx resulted in an increase in adult parasites recovered
In this study we tried to spotlight some aspects of the immune response
against the Gx, by separation of the Gx, studying its protective value in mice,
preparation of polyclonal and monoclonal antiglycocalyx antibodies, and
studying the effect on schistosome larvae in vitro.
The approach and work plan which was used to achieve the goal of our
study could be summarized as follows:
1- Separation of intact glycocalyx:
a) Parasite: cercariae are obtained by exposing the infected snails to light.
b) labeling of glycocalyx by periodate - NaB-’H4reduction.
c) Phenol-water extraction of labeled glycocalyx.
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d) Purification of the extracted glycocalyx by chromatography column.
Two types of column were used: i) Lotus-lectin affinity column. ii) Gel
filtration chromatography.
2. Monitoring the antigenicity of the purified glycocalyx:
a) Injection a group of mice with the purified glycocalyx.
b) Detection of the antigenicity by .ndirect microplate ELISA.
c) Detection of surface binding antibodies using indirect immunofluorescence
assay.
3. Studying the protective value of glycocalyx:
a) Immunization of a group of mice with glycocalyx.
b) Challenging the immunized mice and another non-immunized control
group with Scmansoni cercariae.
c) Recovery of adult worm by hepatic perfusion.
4. Studying antiglycocalyx antibody-mediated cytotoxicity on schistosomules in
vitro.
5. Antiglycocalyx eosinophil-mediated cytotoxicity assay in vitro was done to
study the effect of antiglycocalyx antibodies on the eosinophils activity.
6. Production and characterization of antiglycocalyx monoclonal antibodies:
7. Studying antiglycocalyx monoclonal antibodies-mediated cytotoxicity in
vitro.
8. Studying antiglycocalyx monoclonal antibodies- eosinophil-mediated
cytotoxicity in vitro.
9. studying crossinhibition between different antiglycocalyx isotypes.
The glycocalyx described in this study is immunologically active. It stimulates
the humoral immune response in the immunized nuce. Although antiglycocalyx
antibodies were found to be cytotoxic to the schistosomules in vitro, no
protective effect was demonstrated in vivo. Eosinophil-mediated cytotoxicity,
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which is known to be a corner stone in human immunity against schistosomes,
was found to have no effector function in mice defensive immune response
against schistosomes. Moreover, monoclonal antiglycocalyx IgM was found to
have an inhibitory activity affecting the cytotoxic effect of other isotypes present
in glycocaIyx immune sera.
Depending on the above discussed data, it could be postulated that:
- Shedding of the glycocalyx during penetration of the skin of the host
may account for increasing resistance of developing schistosomules to immune
attack. This, in tum, may provide a mechanism which allows the parasite to
evade the host’s immune response.
- The contradiction between the results of antiglycocalyx antibodymediated
cytotoxicity obtained in vivo and that obtained in vitro is in itself
revealing and suggesting that its effect is crucially dependent upon factors as yet
poorly understood. This emphasize the need for more detailed research of the
immunity of schistosomiasis and the interactions between immune responses
elicited against different congregation of antigens either included in vaccine or
produced by the infecting parasites during the course of infection, for progress
to be made in this central area of schistosome immunology.
- Eosinophils have no effector function in mice immune protective response
against schistosome infection.
- The in vitro blocking effect produced by 1D6/A12 supports the theory
suggesting that susceptibility to infection is controlled by the development of
blocking antibody response, and thus it might be more important to characterize
markers of susceptibility than putative indicators of protection.
- More detailed studies are needed to defme the determinants that guide the
susceptibility of, only, some individuals to infection