Immunity to tapeworms: vaccination against Hymenolepis diminuta and role of the bursa of Fabricius in rejection of Raillietina cesticillus

Elowni, Elsayed Elsiddig (1980) Immunity to tapeworms: vaccination against Hymenolepis diminuta and role of the bursa of Fabricius in rejection of Raillietina cesticillus. PhD thesis, University of Glasgow.

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Attempts were made to vaccinate mice against infection with
Hymenolepis diminuta, a tapeworm rejected from the se hosts by an
immunologically- mediated mechanism. Various putative antigenic
preparations from the strobilated worm were tested. Marginal
protection, as compared with that induced by an oral infection from
cysticercoids, was obtained when mice were orally vaccinated with
multiple doses of whole worm antigens. Marginal protection was
also obtained when tegument antigens were given by this route.
Results from two other experiments with tegument antigens, however,
did not confirm this finding. No protection was obtained following
vaccination with antigens ,from sonic disruption of somatic cells,
exoantigens, saline extracts or egg antigens.
On the basis of evidence from other experimental models, it is
proposed that this failure to evoke strong protective immunity by
vaccination with killed worm antigens was possibly due to one or
more of the following factor s:
(i) the tapeworm protective antigens were not pre sent initially in
most of the preparations injected or that they were pre sent in
too Iowa quantity to stimulate immunity
(ii) the worm protective antigens were highly labile and they were
destroyed during preparation, probably by enzymes released
by the disintegrating worms themselves, or inactivated by
chemical reactions in the stomach or intestine when the se
preparations were given orally or intraduodenally.
(iii) . -the physicochemical characteristic s of the se protective antigens
had been altered during preparation
(iv) the presence of a wide array of worm antigens, e. g. in a
homogenate, dissipated the host immune response and masked
the presence of the protective antigens possibly as a result of
antigenic competition
(v) the route of antigen administration was the crucial factor that
militated against the induction of functional immunity rather
than the antigens themselves
(vi) the duration of antigenic stimulation was not long enough and a
longer period. analogous to that required for the development of
immunity from an enteric H. diminuta infection, was needed
(vii) the regimes of vaccination described were conducive to the
induction of tolerance.
To elucidate the validity of these assumptions, experiments were
carried out with live worm antigens. The rationale behind each
approach is described separately in the text. Strobilate a-day-old
worms. apparently capable of surviving for appreciable periods of
time when implanted subcutaneously or intraperitoneally, did not
immunize mice against challenge. Implantation of a strobilate 8-day- day old
worm surgically into the duodenum conferred only weak protection.
The in vivo process of excystation, which is by passed when immunization
is performed by implantation of worms directly into the
duodenum, had no influence on the ability of the worm to stimulate
immunity. The se findings suggest that the failure to induce strong
immunity by parenteral implantation of a live a-day-old was possibly due to -the fact that the 8-day- old worm is, in itself, inefficient in
inducing a pronounced protective response against challenge, even
when presented enter ally • The fact that a weak protective response
was induced by the intraduodenal administration of the 8-day-old worm
and not by parenteral implantation of the se worm s suggests that the
enteric route is more efficient in the induction of functional immunity
against the tapeworm than either the subcutaneous or intraperitoneal
routes. In other experiments it was established that the young worm
is more efficient in the stimulation of protective immunity against
challenge than older worms. It is of interest that the older worms,
when implanted surgically into the duodenum, pre sent the host with
significantly larger amounts of strobili antigens per unit time than do
the younger ones. This observation casts doubt on the significance
of the strobila as the major source of H. diminuta protective antigens .
The logical explanation for the failure to immunize mice by vaccination
with the killed worm antigens is that this is possibly because the
antigens used were derived mainly from strobilar tis sue obtained from
worms even older than the 8-day-old parasites whose poor immunizing
potential was demonstrated.
Live excysted worms, which provide only scolex and neck antigens J
were capable of inducing a protective response when administered
intraperitoneally. Irradiated worms, incapable of growing strobilae,
were as immunogenic as worms of the same age which were not
irradiated. Immunization of mice with an irradiated vaccine is advantageous
in the sense that the immunizing infection can be denoted as
self-limiting resulting in the prevention of propagation of the parasite

to the intermediate host, at a time when specific protective immunity
is raised in the definitive host.
Two independent investigations were undertaken to locate the origin
of H. diminuta protective antigens. The technique s of chemical
abbreviation of immunizing infections and irradiation were used for
this purpose. The re suits provided evidence that the induction of
functional immunity against H. diminuta in mice is independent of the
presence of a strobila: is determined by the duration of an antig e nic
stimulus deriving from the scolex and/or neck regions. The degree
of this immunity is also determined by the number of worms in the
immunizing infection. The conclusions drawn from the present
investigation as to the origin of H. diminuta protective antigens and
the immunogenic potential of irradiated worms are at variance with
those reached by other investigators.
In the second part of this thesis the mechanism of the immunologically based
rejection of Raillietina cesticillus from chickens was investigated.
Chickens whose ability to produce antibodies was
abrogated by bur sectomy and irradiation developed protective immunity
against the tapeworm as did the controls with specific anti-worm
antibodies in their sera. It is suggested that antibody is not
the crucial component of the mechanism affecting the growth and
development of R. cesticillus in the immune chicken.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: Q Science > QL Zoology
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Supervisor, not known
Date of Award: 1980
Depositing User: Miss Louise Annan
Unique ID: glathesis:1980-6103
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 13 Feb 2015 15:15
Last Modified: 13 Feb 2015 15:15

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