3D6 and 4B3: Recombinant expression of two anti-gp41 antibodies as dimeric and secretory IgA

Background Sexually transmitted diseases are predominantly acquired via mucosal membranes of the rectal or genital tract during sexual intercourse. This major port of virus entry is naturally defended by the humoral immune response, with immunoglobulin A (IgA) as the primary antibody class to elicit mucosal immunity. Dimeric IgA (dIgA) reaches the luminal side of mucosal tissues by transcytosis through epithelial cells lining the mucosa. In a first step, dIgAs specifically bind to the basolaterally expressed polymeric immunoglobulin receptor (pIgR) on epithelial cells. For release of IgAs on the luminal side the extracellular portion, termed secretory component (SC), remains attached to the antibody to form secretory IgA (sIgA) [1,2]. One example of a sexually transmitted disease is the human immunodeficiency virus (HIV) which annually infects several million individuals on a global scale and potentially leads to the acquired immunodeficiency syndrome (AIDS). Although current therapies can reduce disease progression in infected individuals, no cure is yet available or within reach in near future. As a consequence increased attention is now being paid to develop drugs that could prevent virus acquisition. 3D6 and 4B3 are two monoclonal antibodies (mAb) which have originally been isolated as IgG1 isotype from seroconverted HIV-1 patients and bind to the principal immunodominant domain of gp41. In the course of this project both mAbs were isotype switched to IgA1. Recombinant CHO cell lines were established for the production of 3D6 and 4B3 as dimeric as well as secretory IgA. While dIgA were expressed by a single cell line, sIgA are produced by a biochemical association of dIgA with SC. Both dIgA and sIgA variants were characterized and the contribution of the heavily glycosylated SC on IgA stability will be investigated.