Includes bibliographical references (leaves 117-133). / v, 133 leaves, 5 leaves of photographic plates : ill. (some col.); 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Concerned with the family of genes that encode variant-specific surface proteins in the parasitic protzoon, Giardia. Specific goals were to identify and compare closely related genes, which may form subsets within the larger VSP gene family. / Thesis (Ph.D.)--Adelaide University, Dept. of Molecular Biosciences, 2001

Bibliography: leaves 183-228

Gerbils, experimentally infected with Giardia lamblia trophozoites, had trophozoites and encysting trophozoites in all 3 equal sections of the small intestine and in the colon at necropsy. Cysts were found in the second and third sections of the small intestine and in the colon. WB strain derived trophozoites (WB, D1, WB-C6, and V1) differed in levels of encystation in vitro but not in gerbils. Passage in gerbils increased the in vitro encystation levels of WB and D1 but decreased that of WB-C6 and V1. No differences were found in the total protein profiles or isoenzyme patterns of these G. lamblia populations. Immunization of mice with in vitro cysts produced monoclonal antibodies (mAbs) recognizing cyst protein antigens. In Immunofluorescence (IFA), mAb 5A4.G6 recognized cyst walls. This mAb reacted with a 38 kD band on Western blots. IFA results showed that mAb 8C5.C11 reacts with vesicles in encysting trophozoites and with cyst walls. It recognized 26, 28, 42 and 46 kD bands in Western blots. When mAb 8C5.C11 and Guinea pig complement were added to 0-9 hour encysting cultures, the numbers of cysts produced were significantly reduced compared to control. MAb 5A4.G6 did not affect in vitro encystation.

In this study, we determined the immunogenicity of CWP2 and its potential as a vaccine candidate against giardiasis. CWP2 was expressed as a recombinant protein with an hexa-histidine affinity tag and was isolated from inclusion bodies. When BALB/c mice were immunized with CWP2, a specific IgA was detected in the feces. When mice were immunized with CWP2 + cholera toxin, as an adjuvant, IgA in the feces, and IgA, IgG1, and IgG2a in the serum, all specific to CWP2, were detected. Also, CD-1 mice were infected with G. muris and presence of specific IgA antibodies to CWP2 were detected in the feces. This result indicated that CWP2 was recognized by the immune system in a natural infection. IL-4 and IL-5 were released from Peyer's patches (PP) and mesenteric lymph nodes (MLN) cells when stimulated with concanavalin A. In spleen cells, IFN-gamma, IL-4, and IL-5 were released when stimulated with concanavalin A. However, in PP, MLN and spleen cells, the levels of cytokines were barely detectable when stimulated with CWP2. The presence of IgG2a (Th1), IgA and IgG1 (Th2) as the production of IFN-gamma (Th1), IL-4 and IL-5 (Th2) confirmed that CWP2, when presented orally to mice, stimulates both a Th1 and Th2 type immune response, locally and systemically.

No description available.

Biological and immunological aspects of the host-parasite relationship were examined in mice which are susceptible (A/J) and resistant (B10.A) to Giardia muris. B10.A exhibited a shorter latent period, lower cyst output during the acute phase of the infection and shorter period of cyst release compared to A/J. Characteristics of the infection transmitted from mouse-to-mouse and those induced by oral inoculation with cysts or trophozoites were similar. The infection was longer in male A/J and B10.A mice compared to females. Susceptibility and resistance during both the acute and elimination phases of the infection were under non-H-2-linked multigenic control. A/J and B10.A differed in non-specific serum IgG and IgA, but not in the specific IgG and IgA to G. muris. Specific antibodies participated in complement-mediated killing of trophozoites. Spleen, mesenteric lymph node and peritoneal cells from A/J and B10.A mice had a similar ability to kill trophozoites. The capacity of B10.A to mount inflammatory responses was greater than that of A/J. A/J were more immunosuppressed than B10.A during the infection, particularly at mucosal sites. Macrophage-like suppressor cells were shown to be the mediators of this suppression.

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