Isolation of A Human GM-CSF Antibody with Potent Neutralizing Activity from a Subject with Idiopathic Pulmonary Alveolar Proteinosis (96.24)

Abstract

Abstract Background. GM-CSF has been implicated in the development of autoimmune disorders. The efficacy of neutralizing anti-GM-CSF has been demonstrated in several animal disease models rheumatoid arthritis, asthma and lung inflammation. While humanization of murine antibodies (Abs) and phage-display technology have generated potential therapeutic leads currently in development, these engineered leads face potential challenge of serum stability and immunoreactivity. We have isolated a fully human anti-GM-CSF from a patient of idiopathic pulmonary alveolar proteinosis (iPAP) who produces anti-GM-CSF as autoantibody. Method. To isolate natural human Abs, we used a short term memory B cell culture system to generate Ab-containing supernatants and screened for anti-GM-CSF that inhibited the proliferation of TF-1 cells in response to human GM-CSF. The specificity for GM-CSF was then confirmed via secondary binding screening in Alphascreen assays. Recombinant human Abs were isolated from the corresponding memory B cells using RT-PCR and subcloning. Results. By analyzing the serum from several iPAP patients for the neutralizing activity against TF-1 proliferation, we selected one peripheral blood sample for Ab isolation. TCN-350 was isolated with IC50 of 27 pM for TF-1 inhibition. It binds human GM-CSF with an affinity of 39 pM and cross-reacts with rabbit GM-CSF with an affinity of 1 nM. The high neutralization potency of TCN-350 warrants further evaluation as a therapeutic lead.