A Humanized Form of a CD4-Specific Monoclonal Antibody Exhibits Decreased Antigenicity and Prolonged Plasma Half-Life in Rhesus Monkeys While Retaining Its Unique Biological and Antiviral Properties

Abstract

Certain monoclonal antibodies (MAbs) directed against CD4 can efficiently block HIV-1 replication in vitro. To explore CD4-directed passive immunotherapy for prevention or treatment of AIDS virus infection, we previously examined the biological activity of a nondepleting CD4-specific murine MAb, mu5A8. This MAb, specific for domain 2 of CD4, blocks HIV-1 replication at a post-gp120-CD4 binding step. When administered to normal rhesus monkeys, all CD4+ target cells were coated with antibody, yet no cell clearance or measurable immunosuppression occurred. However, strong anti-mouse Ig responses rapidly developed in all monkeys. In the present study, we report a successfully humanized form of mu5A8 (hu5A8) that retains binding to both human and monkey CD4 and anti-AIDS virus activity. When administered intravenously to normal rhesus monkeys, hu5A8 bound to all target CD4+ cells without depletion and showed a significantly longer plasma half-life than mu5A8. Nevertheless, an anti-hu5A8 response directed predominantly against V region determinants did eventually appear within 2 to 4 weeks in most animals. However, when hu5A8 was administered to rhesus monkeys chronically infected with the simian immunodeficiency virus of macaques, anti-hu5A8 antibodies were not detected. Repeated administration of hu5A8 in these animals resulted in sustained plasma levels and CD4+ cell coating with humanized antibody for 6 weeks. These studies demonstrate the feasibility of chronic administration of CD4-specific MAb as a potential means of treating or preventing HIV-1 infection.

CD4-anchoring HIV-1 Fusion Inhibitor with Enhanced Potency and in Vivo Stability

“…Expression Plasmids-For the construction of the bifunctional human CD4 antibody-based fusion inhibitors, the variable domains (V L and V H ) of the humanized human CD4-specific mAb (hu5A8, also called TNX-355) (15) were cloned and expressed as the human IgG1 isotype, which carries L234A and L235A double mutations (IgG1-LALA). This reconstructed anti-CD4 mAb was named 6314.…”

Depletion of CD4+ T cells abrogates post-peak decline of viremia in SIV-infected rhesus macaques

“…Similarly, we reasoned that this treatment would not influence the antiviral effect of SIV-specific neutralizing Abs, as they do no become detectable until after the acute stage of SIV mac infection (23)(24)(25). Finally, we proposed that by inoculating RMs with SIV after a 6-week washout period from the last infusion of Cdr-OKT4A-huIgG1, we would avoid the potential confounding factor of direct antiviral activity of this anti-CD4 Ab (26).…”

A fully human anti-Ep-CAM scFv-beta-glucuronidase fusion protein for selective chemotherapy with a glucuronide prodrug

“…The use of a humanised antibody fragment in a fusion protein is not ideal. Although humanised antibodies are less immunogenic than murine antibodies, anti-idiotypic antibodies can develop as was shown in patients as well as in Rhesus monkeys (Reimann et al, 1997;Richards et al, 1999). This may be due to the variable regions of humanised antibodies being still of murine origin.…”