Expression of biologically active bovine interleukin 7 and evaluating the activity in vitro

Interleukin 7 (IL-7) is a ϒc family cytokine involved in the homeostatic proliferation and maintenance of immune cells. In the present study, we report the expression of bovine IL-7 (bIL-7) in Escherichia coli and evaluated for its biological activity.

The sequence coding for bIL-7 (mature protein) was amplified from primary bovine kidney cell culture and cloned into pET28-a vector and expressed in E. coli (BL 21 DE3). The expressed protein was purified by nickel-nitrilotriacetatechromatography, and the reactivity of the protein was confirmed by western blotting using monoclonal antibodies raised against human IL-7. The biological activity of expressed bIL-7 was evaluated by analyzing its effect on the expression of anuclear factor for activated T-cells c1 (NFATc1), B-cell lymphoma 2 (Bcl2), suppressor of cytokine signaling 3 (SOCS3) molecules in bovine peripheral blood mononuclear cells (PBMCs) by quantitative polymerase chain reaction. Ability of the expressed protein was also analyzed by its effect on phosphorylating signal transducer and activator 3 (STAT3) molecule by immunostaining in human embryonic kidney cells 293 (HEK293) cells.

The bIL-7 was able to induce the expression of Bcl2 and NFATc1expression in bovine PBMCs by 7 and 5-folds, respectively, whereas a 2-fold decrease was observed in the case of SOCS3 expression. Immunostaining studies in HEK293 cells using antihuman phospho-STAT3 showed activation and nuclear translocation of STAT3 molecule on bIL-7 treatment.

bIL-7 gene was successfully amplified, cloned, and expressed in a prokaryotic expression system. The biological activity study showed that the E. coli expressed bIL-7 protein is biologically active. Considering the role of IL-7 in T-cell homeostasis and memory cell generation, this molecule can be used for enhancing the vaccine response and that has to be proved by further experiments.