Affiliation:
1. Division of Infectious Diseases, Department of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, North Grafton, Massachusetts 01536
Abstract
ABSTRACT
5C12 HuMAb is a human monoclonal antibody against the A subunit of Shiga toxin 2 (Stx2). We have previously shown that 5C12 HuMAb effectively neutralizes the cytotoxic effects of this toxin by redirecting its transport within the cell and also by neutralizing the toxin's ability to inhibit protein synthesis. The 5C12 HuMAb and its recombinant IgG1 version protect mice at a dose of 0.6 μg against a lethal challenge of Stx2. The contribution of the Fc region to this observed neutralization activity of the 5C12 antibody against Stx2 was investigated in this study. Using recombinant DNA technology, 5C12 isotype variants (IgG1, IgG2, IgG3, and IgG4) and antibody fragments [Fab, F(ab′)
2
] were expressed in Chinese hamster ovary cells and evaluated
in vitro
and
in vivo
. All four 5C12 isotype variants showed protection
in vitro
, with the IgG3 and IgG4 variants showing the highest protection
in vivo
. The Fab and F(ab′)
2
fragments also showed protection
in vitro
but no protection in the mouse toxicity model. Similar results were obtained for a second HuMAb (5H8) against the B subunit of Stx2. The data suggest the importance of the Fc region for neutralization activity, but it is not clear if this is related to the stability of the full-length antibody or if the Fc region is required for effective elimination of the toxin from the body.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
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