Vaccine adjuvant applications of cpg ODN nanorings and development of Leishmania extracellular vesicle based cutaneous leishmaniasis vaccine

Thesis Type: Doctorate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Arts and Sciences, Department of Biology, Turkey

Approval Date: 2017


Consultant: MAYDA GÜRSEL


In our previous studies we converted a conventional K-type CpG ODN with no interferon-alpha stimulating activity into a potent type I interferon inducer by complexing it with the cationic peptide Tat (47-57). These complexes formed well-defined nanorings with potent vaccine adjuvant activity. Herein, we examined the immunostimulatory and vaccine adjuvant activity of K/Tat nanorings in two different mouse tumor models. Results showed that K/Tat nanorings suppressed tumor progression by inducing antigen specific CTL-mediated IFNγ production and CTL-specific EG.7 thymoma killing. However, the nanorings had no beneficial effect in the B16 F10 melanoma model when used as stand-alone immune stimulatory agents. Since the nanorings proved to be of interest when used together with an antigen, in further experiments we explored the optimal vaccination route of nanorings and the model antigen ovalbumin. Results indicated that K/Tat nanorings triggered the highest antigen specific IgG2c titers and OVA-specific IFNγ production when administered via the intranasal route. The success of K/Tat nanorings in intra nasal administration suggested us the potential use of nanorings as mucosal adjuvants for future trails. The second half of this thesis analyzed the vaccine potential of extracellular vesicles isolated from Leishmania. Leishmaniasis is an infectious disease caused by Leishmania protozoa transmitted to mammalian hosts by infected sand flies. The absence of an available licensed vaccine and the cost, toxicity and drug resistance associated with the pentavalent antimonials used for treatment, prompted us to explore a novel strategy of vaccine development based on use of Leishmania extracellular vesicles (EVs). For this, antigen-rich EVs secreted from Leishmania parasites were purified, characterized and their immune protective vaccine potentials were tested in mice as such or in combination with Th1 type vaccine adjuvants (K-ODN, D-ODN, Nanorings, cGAMP and cGAMP/K-ODN). Herein we show that Leishmania extracellular vesicles (EVs) decreased the lesion size when adjuvanted with K/cGAMP and stimulated a Th1 type immune response in L.tropica induced cutaneous leishmaniasis model.