Identification of immunostimulatory adjuvant(s) that will promote a Th17-type of immune response
Date
2017-07-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-2282-9210
Type
Thesis
Degree Level
Masters
Abstract
Immunostimulatory adjuvants are substances added to vaccines to promote and direct a robust Th1, Th2, or Th17 immune response. Murine Th17 cells are produced and differentiated from naïve T cells in the presence of transforming growth factor (TGF)-β and interleukin (IL)-6 and once differentiated, Th17 cells produce cytokines IL-17A, IL-17F, IL-21 and IL-22. We investigated how immunostimulatory molecules such as poly[di(sodium carboxylatoethylphenoxy)-phosphazene (PCEP), Alum, CpG oligodeoxynucleotide (CpG ODN), Curdlan, Leptin and Lipopolysaccharide (LPS), alone or in combination influenced differentiation and/or activation of Th17 type immune cells in mice. In vitro studies showed that murine splenocytes stimulated with CpG showed significantly induced production of IL-12, a cytokine important for induction of Th1 type immune cells and IL-12 is known to be inhibitory for differentiation of Th17-type immune cells. Curdlan + Leptin +/- PCEP and PCEP + Curdlan induced significant expression of TGF-β. No immunostimulant combination induced both IL-6 and TGF-β, which we anticipated would be required for Th17 cell differentiation. When we investigated the cytokines induced by the immunostimulants 48 hours after injection in muscle tissue, we determined that Curdlan + Leptin significantly induced production of IL-17, likely from activation of already differentiated T cells. TGF-β was significantly induced in response to Curdlan and Leptin, alone and in combination but they were poor inducers of IL-6. PCEP+/- CpG or LPS significantly induced expression of IL-6 but not TGF-β. Finally, we immunized mice via intramuscular (i.m.) route with OVA in the presence of the immunostimulatory adjuvants and assessed cytokine production from OVA-restimulated splenocytes 5 weeks later. ELISA results indicated that OVA-specific IL-17 production was significantly induced in splenocytes from mice immunized with PCEP + OVA relative to the mice immunized with Curdlan + OVA, although it was insignificant with respect to the OVA immunization group presumably due to the highly variable responses. Using flow cytometric analysis, we observed that vaccination with PCEP + OVA and Curdlan + Leptin + OVA significantly induced the frequency of OVA-specific splenic CD4+IL-17+ cells. Curdlan + Leptin also significantly induced the frequency of OVA-specific CD4+Foxp3+ cells and CD4+IL-17+Foxp3+ double positive cells. Thus, we conclude that in vitro studies are poorly predictive of the type of adaptive response that may be induced when immunostimulatory adjuvants were used in a vaccine. Furthermore, vaccines formulated with PCEP and Curdlan + Leptin adjuvants promote Th17 cell differentiation and should be investigated as a combinational adjuvant for bacteria or fungal based immunizations.
Description
Keywords
Adjuvant, Th17
Citation
Degree
Master of Science (M.Sc.)
Department
School of Public Health
Program
Vaccinology and Immunotherapeutics