Fully human anti-macrophage migration inhibitory factor antibodies as potential therapeutics for sepsis and septic shock

Background

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine and counter-regulator of glucocorticoids. Since the 1990s, MIF has been known to be a critical mediator of sepsis and septic shock. Circulating concentrations of MIF are elevated in patients with sepsis, and MIF levels are associated with disease severity and fatal outcome. Mouse monoclonal antibodies and rabbit polyclonal antibodies against MIF were shown to be protective in various animal models of sepsis. MIF therefore emerged as an attractive new target for treatment of patients with severe sepsis and septic shock.

Methods

A diverse panel of human MIF-specific antibodies was generated by selection from a phage display library. This panel was subjected to extensive in vitro testing to identify antibodies that neutralize MIF activity. The antibody showing the highest potential was improved by affinity maturation; that is, by generating modified versions of this antibody by CDR1-2 shuffling and selecting high-affinity variants by phage display. The lead candidate antibody and its affinity maturated variant were tested in experimental mouse models of endotoxic shock and Escherichia coli peritonitis sepsis.

Results

In vitro testing of human anti-MIF antibodies enabled the identification of antibodies that neutralize the activity of MIF in a glucocorticoid overriding activity assay and in a proliferation assay. Antibody Bax94 was designated as lead candidate, and affinity maturation of this antibody led to the generation of BaxA10, a variant with a 10-fold higher affinity for MIF. In an endotoxic shock model, pretreatment of mice with Bax94 and BaxA10 reduced circulating concentrations of TNF (control antibody: 4.9 ± 10.3 ng/ml; Bax94: 0.4 ± 0.4 ng/ml, P < 0.01; BaxA10: 0.2 ± 0.5 ng/ml, P < 0.0001) and of IL-6 (control antibody: 3.1 ± 1.6 ng/ml; Bax94: 2.1 ± 0.78 ng/ml, P = 0.0003, Bax10: 1.5 ± 0.7 ng/ml, P < 0.0001), and increased survival from 21% (control antibody) to 52% (Bax94; P < 0.05) and 58% (BaxA10; P < 0.05). The protective effect of the two anti-MIF antibodies was also demonstrated in a live E. coli peritonitis sepsis model in which survival rates increased from 10% (control antibody) to 34% (Bax94; P < 0.05) and to 56% (BaxA10; P < 0.01).

Conclusion

We have generated fully human anti-MIF antibodies that neutralized the proinflammatory effects of MIF in vitro and that showed significant protective effects in experimental sepsis. In vivo protection tended to correlate with the affinity of the antibody for MIF.