Vaccination has proven a cost-effective method of managing infectious diseases, but attempts to develop an effective fetal vaccine have proven difficult due to the immaturity of the immune system and the propensity of the developing immune system to induce tolerance to immunizing antigens. This thesis is concerned with the induction of specific immunity in the second trimester ovine fetus using the oral DNA immunization method. In utero oral delivery of naked DNA plasmid was selected as the method of immunization due to previous successes in the third trimester ovine fetus and the immunostimulatory properties of the bacterial DNA backbone, which may help overcome developmental tolerance. Transfection and expression studies in the third trimester ovine fetus revealed the oral mucosal epithelium as the primary site of transgene expression and functionally active antigen was also localized to lymph nodes draining the oral cavity. Efficient transfection and expression of plasmid following oral delivery was specific to the fetus and correlated with a lesser degree of epithelial differentiation. Oral DNA delivery in the second trimester resulted in detection of transgene activity in 100% of treated fetuses and the level of transgene activity was greater than in fetuses treated in the mid-third trimester. Using a plasmid encoding the gene for bovine herpesvirus-1 truncated glycoprotein D (tgD), immunization studies were then conducted in the second trimester fetus. A new lower age limit for fetal immunization was established at 55-60 days gestation (gestation period is 148 days), which coincides with the appearance of lymphocytes in peripheral tissues. Antigen-specific antibody, interferon-× responses and/or neonatal anamnestic responses were detected in 66% of fetuses immunized between 55 and 84 days gestation. The duration of fetal primary immune responses was equivalent to that achieved in young lambs following optimized DNA vaccination, but the magnitude of fetal immune responses was limited. The persistence of immune memory from the second trimester to birth was consistent with experimental data which showed that the duration of immune memory had a stronger correlation to the duration, as compared to the magnitude, of the primary antibody response. Overall, the experiments within showed that oral DNA immunization of the early second trimester fetus is feasible and not associated with the induction of tolerance. These findings suggest that it may be possible to protect against mother-to-child transmission of infectious pathogens by targeting protection at the level of the fetus.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-01212008-142035 |
| Date | 25 January 2008 |
| Creators | Tsang, Cemaine Happy |
| Contributors | Misra, Vikram, Middleton, Dorothy M., Guilbert, Larry, Griebel, Philip J., Babiuk, Lorne A., Polley, Lydden, Qualtiere, Louis |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-01212008-142035/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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