The Immune Memory Response of In Vitro-Polarised Th1, Th2, and Th17 Cells in the Face of Ovalbumin-Transgenic Leishmania major in a Mouse Model

Th1 and Th2 cytokines determine the outcome of <i>Leishmania major</i> infection and immune protection depends mainly on memory T cells induced during vaccination. This largely hinges on the nature and type of memory T cells produced. In this study, transgenic <i>Leishmania major</i> strains expressing membrane-associated ovalbumin (mOVA) and soluble ovalbumin (sOVA) were used as a model to study whether fully differentiated Th1/Th2 and Th17 cells can recall immune memory and tolerate pathogen manipulation. Naïve OT-II T cells were polarised in vitro into Th1/Th2 cells, and these cells were transferred adoptively into recipient mice. Following the transferral of the memory cells, the recipient mice were challenged with OVA transgenic <i>Leishmania major</i> and a wild-type parasite was used a control. The in vitro-polarised T helper cells continued to produce the same cytokine signatures after being challenged by both forms of OVA-expressing <i>Leishmania major</i> parasites in vivo. This suggests that antigen-experienced cells remain the same or unaltered in the face of OVA-transgenic <i>Leishmania major.</i> Such ability of these antigen-experienced cells to remain resilient to manipulation by the parasite signifies that vaccines might be able to produce immune memory responses and defend against parasitic immune manipulation in order to protect the host from infection.