In - Silico Engineering to Decrease the Affinity towards FcyR1 & FcyR3 and in Vitro Immune - Stimulatory Activity of Chimeric IL - 15

Abstract

Our immune system has an inherent function to locate and eliminate tumors; however, tumors have evolved mechanisms to evade immune surveillance with the help of several immunomodulatory pathways rendering immune cells deactivated. One of the most promising approaches in tackling cancer is by augmenting immune responses with the help of cytokines which facilitate reactivation of immune cells and help regaining the ability to eliminate malignancies.IL-15 is one such immunotherapeutic cytokine which is first in the list of 12 immunotherapeutic drugs released by the National Cancer institute, NIH, USA. However, native IL-15 has limitations like short half-life, poor bioavailability and toxicity. To overcome such limitations, we have developed a fusion protein having specific mutations incorporated in IL-15 that fused with Fc region of IgG/2a immunoglobulin presumably making it an ideal molecule for cytokine therapy with the purpose of preferentially activating the CD8+ T cells. An Indian patent has been filed and published for this invention (Indian Patent Application No. 201721010096A). Chimeric fusion proteins have been reported to exhibit anti-tumor activity in several tumor models. In this study, we searched for different mutations that could decrease the affinity of chimeric IL-15 with various Fc receptors except FcγR2. We also examined in-vitro the ability of the chimeric product in induction of T cell responses in dose dependent manner.Our results show that 5µg per ml of chimeric IL-15 induces proliferation of CD4+ as well as CD8+ T cells and production of IFN-g in a decent population of both types of T cells. Our in-silico predicted mutations in chimeric IL-15 do not seem to have any significant impact on the affinity towards FcγR1, FcγR3.