Abstract
The work reported in this thesis fell into three main
sections. The first was a study of the immunochemistry
of a saline extract of T. saginata proglottids (SE) with
particular reference to the antigens involved in the
serological response of cattle to infection with T. saginata.
It was hoped that this information would facilitate the
production of relatively pure and specific T. saginata
antigens for use in serodiagnostic tests for this
infection.
The second section was concerned with an investigation
of the potential of certain serological techniques, not
previously used with T. saginata infections in cattle,
for use in serological investigations of experimental and
field infections. In the third and final section these
serological techniques were used to measure the serum
antibody levels in cattle both experimentally and naturally
infected with T. saginata. Where possible, partially
purified saline extracts of T. saginata were used as
antigens in these techniques.
The immunochemistry of SE was studied by gel filtration
on Sephadex G200, Sepharose 6B and Sepharose 4B, by ion
exchange chromatography and by immunoadsorption techniques.
It was found that SE consisted of two main groups of
antigenic molecules. The first group were of a molecular
weight equivalent to that of the macroglobulin component
of bovine serum and contained most of the haemagglutinin
activity. The second group were of a molecular weight
equivalent to that of the globulin component of bovine serum
and contained mainly gel precipitin activity. The immunoadsorption studies on this extract showed the method to be
potentially valuable for the purification of these helminth
antigens but much work still remains to be done on this
relatively new approach.
The micro immuno- precipitation (MGP) and the indirect
haemagglutination (IDH) techniques had already been used in
bovine cysticercosis research prior to the commencement of
this work and only minor modifications have been made to
these procedures. However, the haemagglutination inhibition
(HI), enzyme -linked immunosorbent assay (ELISA) and the
soluble antigen fluorescent antibody (SAFA) techniques have
each been adapted to the study of the T. saginata system in
cattle for the first time. A comparison of SAFA and ELISA
showed that ELISA was the preferable of the two techniques
for experimental work. The technique also has potential as
a versatile and sensitive tool for studies on naturally
infected cattle. The HI technique proved effective in
detecting haemagglutinin activity in fractions of SE
produced by column chromatography.
Studies on cattle experimentally infected with
T. saginata showed that the ELISA technique compared favourably with the IDH and MGP techniques. ELISA could in fact
be used to detect an antibody response to both haemagglutinin
and gel precipitin antigens. In contrast the IDH technique
mainly detected an antibody response to haemagglutinins
and the MGP technique an antibody response to gel precipitin
antigens.
A limited study on cattle naturally infected with
T. saginata showed, however, that ELISA is not presently
a reliable test for T. saginata infection in the field.
In particular, further work requires to be done on the
antigens used in serological techniques, although there was
an indication that some, but not all, cross reacting antigens
could be removed by gel filtration and immunoadsorption.
