Inhibition of CRAC with a human anti-ORAI1 monoclonal antibody inhibits T-cell-derived cytokine production but fails to inhibit a T-cell-dependent antibody response in the cynomolgus monkey

Abstract

ORAI1 is the pore-forming component of calcium release-activated calcium (CRAC) channels. CRAC channels are the primary route for calcium ion (Ca²⁺) entry into T-cells following antigen stimulation. This Ca²⁺ entry induces proliferation and cytokine production through activation of calcineurin and the nuclear factor of activated T-cells (NFAT) transcription factor along with subsequent cytokine-related genes. It was hypothesized that the in vivo inhibition of T-cell function by blocking ORAI1 or calcineurin would lead to similar functional consequences. To test this hypothesis the activity of 2C1.1, a fully human anti-ORAI1 monoclonal antibody, and cyclosporin A (CsA) were tested in vivo for their suppressive effect on T-cell-derived cytokine production and a T-cell-dependent antibody response (TDAR) using sheep red blood cells (SRBC) in cynomolgus monkeys. Despite showing similar inhibition of ex vivo interleukin (IL)-2 production by stimulated T-cells, both molecules exhibited different pharmacologic effects on the SRBC antibody response. CsA blocked the development of SRBC-specific antibodies, while 2C1.1 failed to inhibit the antigen-specific antibody response. These surprising observations suggest that full inhibition of the CRAC channel is required to inhibit a functional immune response, consistent with findings from human patients with loss of function mutations in ORAI1.

• CRAC
• CsA
• cynomolgus monkey
• ORAI1
• SRBC
• TDAR

Acknowledgements

This work was supported by Jim Meyer, Department of PKDM, Amgen Inc., Thousand Oaks, CA. The authors wish to thank Herve Lebrec for critical review and helpful suggestions with the study design and manuscript.

Supplementary material available online

Supplementary Table 1 and Figure 1