PDBsum entry 1olv

Toxin

PDB id: 1olv

Contents

Protein chain

233 a.a.

Theoretical model

PDB id:

1olv

Name:

Toxin

Title:

Identification of the antigenic epitopes in staphylococcal enterotoxins a and e and design of a superantigen for human cancer therapy

Structure:

Enterotoxin type e. Synonym: ente, staphylococcal enterotoxin e, see. Chain: a. Engineered: yes. Mutation: yes. Other_details: see and sea chimeric molecule sea/e-18

Source:

Staphylococcus aureus

Authors:

B.Walse

Key ref:

E.Erlandsson et al. (2003). Identification of the antigenic epitopes in staphylococcal enterotoxins A and E and design of a superantigen for human cancer therapy. J Mol Biol, 333, 893-905. PubMed id: 14583188 DOI: 10.1016/j.jmb.2003.09.009

Date:

18-Aug-03 Release date: 24-Oct-03

Protein chain

P12993  (ETXE_STAAU) -  Enterotoxin type E from Staphylococcus aureus

Seq: 257 a.a.

Struc: 233 a.a.*

* PDB and UniProt seqs differ at 5 residue positions (black crosses)

DOI no: 10.1016/j.jmb.2003.09.009

J Mol Biol 333:893-905 (2003)

PubMed id: 14583188

Identification of the antigenic epitopes in staphylococcal enterotoxins A and E and design of a superantigen for human cancer therapy.

E.Erlandsson, K.Andersson, A.Cavallin, A.Nilsson, U.Larsson-Lorek, U.Niss, A.Sjöberg, M.Wallén-Ohman, P.Antonsson, B.Walse, G.Forsberg.

ABSTRACT

Monoclonal antibodies have a potential for cancer therapy that may be further improved by linking them to effector molecules such as superantigens. Tumor targeting of a superantigen leads to a powerful T cell attack against the tumour tissue. Encouraging results have been observed preclinically and in patients using the superantigen staphylococcal enterotoxin A, SEA. To further improve the concept, we have reduced the reactivity to antibodies against superantigens, which is found in all individuals. Using epitope mapping, antibody binding sites in SEA and SEE were found around their MHC class II binding sites. These epitopes were removed genetically and a large number of synthetic superantigens were produced in an iterative engineering procedure. Properties such as decreased binding to anti-SEA as well as higher selectivity to induce killing of tumour cells compared to MHC class II expressing cells, were sequentially improved. The lysine residues 79, 81, 83 and 84 are all part of major antigenic epitopes, Gln204, Lys74, Asp75 and Asn78 are important for optimal killing of tumour cells while Asp45 affects binding to MHC class II. The production properties were optimised by further engineering and a novel synthetic superantigen, SEA/E-120, was designed. It is recognised by approximately 15% of human anti-SEA antibodies and have more potent tumour cell killing properties than SEA. SEA/E-120 is likely to have a low toxicity due to its reduced capacity to mediate killing of MHC class II expressing cells. It is produced as a Fab fusion protein at approximately 35 mg/l in Escherichia coli.

Selected figure(s)

Figure 2.
Figure 2. (a) Multiple sequence alignment of SEA, SEE, SEA/E-18 and SEA/E-120. The five different regions A-E, which contain all the substitutions in SEA/E-120 are indicated as coloured boxes. The seven different peptides identified (see Figure 1) are displayed as lines above the amino acid sequence for SEA/E-120. Characters in bold indicate the residues that were modified in SEA/E-120 compared to SEE. (b) Ribbon diagram of SEA/E-120 model. The side-chains of residues G20, T21, G24 and K27 are marked in orange, side-chains of residues S34, S39, S40, E41, K42, A44, T49 in red, side-chains of T74, A75, S78, E79, E81, S83 and S84 are marked in green and side-chains of residues T217, S220, T222, S223, S225 and S227 are marked in purple. The coloured parts of the ribbon corresponds to regions A-E with the same colours as in (a).

Figure 3.
Figure 3. Characterisation of selected superantigen variants. (a) Binding analysis of human anti-SEA to selected superantigen variants using a scintillation proximity assay. In more detail, human anti-SEA was labelled with 125I and the direct binding of these antibodies to increasing concentrations of C215FabSEA, C215FabSEA/E-18, -65, -97, -109, -110, -113 or -120 on biotin conjugated anti-mouseF(ab)[2] on streptavidin PVT beads was measured. (b) The ability to mediate T cell dependant cytotoxicity on tumour cells by increasing concentrations of the selected fusion proteins measured in a cytotoxicity assay against Colo205 cells. (c) The ability of the constructs to mediate T cell dependent killing of MHC class II expressing Raji cells. The calculations are described in Materials and Methods. In a clinical situation, the assay in (b) has been designed to imitate the killing of tumor cells while the assay in (c) reflects induction of systemic toxicity.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2003, 333, 893-905) copyright 2003.

Figures were selected by the author.