Fusion partners can increase the expression of recombinant interleukins via transient transfection in 2936E cells.

The expression levels of five secreted target interleukins (IL-11, 15, 17B, 32, and IL23 p19 subunit) were tested with three different fusion partners in 2936E cells. When fused to the N-terminus, human serum albumin (HSA) was found to enhance the expression of both IL-17B and IL-15, cytokines which did not express at measurable levels on their own. Although the crystallizable fragment of an antibody (Fc) was also an effective fusion partner for IL-17B, Fc did not increase expression of IL-15. Fc was superior to HSA for the expression of the p19 subunit of IL-23, but no partner led to measurable levels of IL-32 gamma secretion. Glutathione S-transferase (GST) did not enhance the expression of any target and suppressed the production of IL-11, a cytokine which expressed robustly both on its own and when fused to HSA or Fc. Cleavage of the fusion partner was not always possible. The use of HSA or Fc as N-terminal fusions can be an effective technique to express difficult proteins, especially for applications in which the fusion partner need not be removed.