SUNY at Albany
June 19-23, 2001
Structure-Based Design Of A Bi-Specific Receptor Mimic That Inhibits T Cell Responses to a Superantigen
Key surface proteins of pathogens and their secreted toxins bind to host immune cell receptors in a manner that is quite different from the binding of natural ligands during pathogenesis and activation of cellular responses. Here, we describe a novel strategy for "non-antibody based" pathogen countermeasure by targeting the very same "alternative mode of host receptor binding" that the pathogen proteins exploit to cause infection and disease. We have chosen bacterial superantigens, such as Staphylococcus enterotoxins (SEA, SEB, etc.) and toxic shock syndrome toxin (TSST-1), as model pathogen proteins to illustrate the principle and application of our strategy. These superantigens are causative agents for the majority of food poisoning and toxic shock syndrome cases in the USA. The mechanism of their pathogenesis involves bypassing of the normal route of antigen processing through superantigen binding to the complex formed by the MHC class II receptor on the antigen presenting cell and the T cell receptor. This alternative mode of binding causes massive cytokine release and T cell proliferation. In contrast to processed antigens requiring all the domains of the receptor complex, superantigens require only the a1 subunit (DRa) of the MHC class II receptor and the variable b subunit (TCRVb) of the T cell receptor. This prompted us to design a bi-specific chimera, DRa-linker-TCRVb, that acts as a receptor mimic and prevents the interaction of a superantigen with its host cell receptors. The linker sequence (GSTAPPA)2 between the receptor domains supports synergistic binding of DRa and TCRVb to the superantigen and thereby makes DRa-(GSTAPPA)2-TCRVb as effective a superantigen-binder as the native (MHC class II-T cell receptor) complex. Finally, we show that DRa-(GSTAPPA)2-TCRVb inhibits superantigen-induced cytokine release and T cell proliferation at nanomolar concentrations.
This work is supported by the DARPA project RK78 and the DOE-LDRD project X1AC.
Elizabeth Hong-Geller(1), Nancy M. Lehnert(1), David L. Allen(1), Beth L. Allen(1), Patrick Shiflett(1), Michael Chen(2), Bruce E. Lehnert(1), & Goutam Gupta(1)*
Bioscience Division(1), Mail Stop M888,Los Alamos National Laboratory,Los Alamos, New Mexico 87545. Texas BioGene, Inc. (2) 1303 Columbia Drive, Suite 201,Richardson, Texas 75081.