Voie d'immunisation et séquence d'administration de l ... - TEL

tel-00827710, version 1 - 29 May 2013
rapid cross-presentation; although delayed slightly, the i.d. immunization induced more
robust, polyfunctional T cells (Figures 24B and 25). Overall, however, the magnitude of the
T cell response was the same for the two routes of immunization, as demonstrated by
tetramer-based enrichment of antigen-specific T cells (Figure 24A). Strikingly, the
differences in T cell responses between i.d. or i.v. immunization were not obtained after
transferring TCR-transgenic T cells. These opposing data highlight the importance of
examining the successful priming of the endogenous repertoire when performing in-depth
studies of vaccine candidates for the most accurate estimation of what may occur in patients.
The increased limit of detection using tetramer-based enrichment strategy allowed us to
distinguish successful priming of the endogenous repertoire after i.v. immunization, and an
enhanced priming effect after i.d. immunization.
In this model we chose to administer a relatively low dose of cell-associated antigen. As
shown in Figure 21, we obtained only between 20-50,000 tetramer-positive T cells at the
peak of the response, which may appear to be low. However, this reflects antigen delivered
alone, without the addition of any adjuvant. If we compare these results with those obtained
following injection with the recombinant Ovalbumin protein, which represents the same
antigen in another form, the recombinant protein cannot elicit effective T cell priming unless
formulated with an adjuvant such as poly I:C or CpG (Durand et al., 2004). Correspondingly,
the addition of poly I:C enhanced the absolute numbers of tetramer-positive cells generated
upon immunization in our model as well (Figure 37). Although the frequency of tetramer-
positive cells is low following immunization, this response is sufficient to induce efficient
priming as demonstrated in the data generated by cytotoxicity assay (Figure 23) and the
reduction of the bacterial load after Listeria challenge (Figure 50). This tetramer-based
enrichment strategy allowed us to carefully study a T cell response that is too low to be
dissected with previously established techniques, but that is sufficient to induce a substantial
response against the specific antigen. Similar approaches with alternate antigens may help to
optimize the doses of antigen used in experimental mouse models, that may be easier to
translate into human therapies.
2) Applications for human immunology
Experimental models that more accurately reflect physiologic conditions are required to test
potential vaccine candidates. Moreover, it is also necessary to develop efficient, novel
technical assays to more completely study the endogenous T cell response in humans as well
as compare the efficacy of different treatments. It is now well accepted that analysis of only
one cytokine, such as IFNγ, in order to assess the efficiency of a T cell response is not
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