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|Title: ||Immune response to cholera toxin and ovalbumin in the Australian brushtail possum|
|Author: ||Khalil, A. M.|
|Degree: ||Postgraduate Diploma in Applied Science|
|Institution: ||Lincoln University|
|Date: ||1997 |
|Item Type: ||Dissertation|
|Abstract: ||The objective of this study was to measure the immune response of female possums to ovalbumin coadministered either with cholera toxin orally and intraileally or with Incomplete Freund's Adjuvant into the Peyer's patches. This study was also carried out to determine whether the reproductive tract of the female possum is a part of the common mucosal immune system; an important factor if an oral contraceptive vaccine was to be developed. Inducing specific antibodies in the mucosa and secretions of the reproductive tract could interfere with the process of fertilization or implantation according to the type of the protein antigen inserted in the vaccine. Cholera toxin is an effective mucosal antigen and acts as an adjuvant when given orally with various antigens. However, no previous studies have determined its efficacy as an oral adjuvant when given with ovalbumin in possums.
In the first experiment fifteen mature female possums were immunised orally with 3mg ovalbumin plus either 0 µg (n=5), 250 µg (n=3), 500µg (n=3), 750µg (n=2) or 1000µg (n=2) of CT adjuvant. Animals were boostered with a second dose two weeks later. In a second experiment 4 possums received 3 mg ovalbumin injected with 250µg cholera toxin directly into the lumen of the small intestine (intra-ileum), followed by a second dose given orally two weeks later. In a third experiment 4 possums were immunised with ovalbumin and IFA injected into Peyer's patches, followed by a second dose injected intra-peritoneally two weeks later. The levels of cholera toxin and ovalbumin IgG antibodies secreted in serum and ileal and reproductive tract secretions were determined by ELISA. Nine of ten possums that received different doses of oral cholera toxin produced antibodies to cholera toxin in serum. However, only one animal produced ovalbumin antibodies in serum. Mean cholera toxin antibody titre was significantly affected by CT dose and time (p<0.01). Mean cholera toxin antibody levels in week 6 were significantly greater in all groups (p<0.05) as compared to animals receiving no cholera toxin.
Ovalbumin antibody levels in serum were not significantly affected by oral cholera toxin (p>0.05). Cholera toxin and ovalbumin antibodies were significantly increased in vaginal secretions at week 7 as compared to pre-immunisation levels. Also, cholera toxin and ovalbumin antibody levels in vaginal secretions were significantly higher than ileal and other reproductive tract secretions. The direct immunisation of cholera toxin and ovalbumin into ileal lumen, significantly increased cholera toxin antibody levels in serum and reproductive tract secretions but it did not reliably increase ovalbumin antibodies in serum or mucosal secretions which suggests that cholera toxin was not an effective adjuvant to potentiate the serum immune response to ovalbumin in this experiment.
Ovalbumin binding in serum, 6 weeks after immunisation via Peyer's patches was higher than binding detected following oral or intra-ileal immunisation. In addition, ovalbumin binding of oviduct and ileal secretions in animals immunised via Peyer's patches was higher than the binding in animals immunised directly into the ileum. The relative importance of IgG and IgA in the possum reproductive tract is yet to be established. In general, production of specific antibodies to ovalbumin and cholera toxin in the reproductive tract secretion and serum following immunisation into the gut indicates that the possum possesses a common mucosal immune system.|
|Supervisor: ||McFarlane, Robin|
|Persistent URL (URI): ||http://hdl.handle.net/10182/4883|
|Access Rights: ||This digital dissertation can only be viewed by current staff and students of Lincoln University.|
|Appears in Collections:||Theses and Dissertations with Restricted Access|
Department of Wine, Food and Molecular Biosciences
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