Toxoplasma gondii p35 antigen modelling and epitope prediction

COSTA, J. G.; LAGIER, C. M.; MARCIPAR, I. S.

Quilmes

Congreso; 1er Congreso Argentino de bioinformática y biología computacional; 2010

Asociación Argentina de Bioinformática y Biología Computacional

Toxoplasma gondii p35 antigen modelling and epitope prediction Juan Gabriel Costa1, Claudia Marina Lagier2, Iván Sergio Marcipar1 1Labortorio de Tecnología Inmunológica, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Santa Fe, Argentina 2Departamente de Química Analítica, Facultad de Cs. Bioquímicas y Farmac., Universidad Nacional de Rosario, Rosario, Argentina The Toxoplasma gondii protein P35 is involved in the host cells invasión. Moreover, it is the main useful antigen to diagnose the infection at the acute phase. To determine linear and structural B Linphocythe  Epitopes (BLE) of the molecule, we have obtained a conformational model based in bionformatic prediction and published experimental data [1].  Modeller software was used to obtain a threading approche using B19 parvovirus capside protein and c-Myc1 oncoprotein as templates. The optimized scored models where verified by free online softwears Verify 3D (http://nihserver.mbi.ucla.edu/Verify_3D/)  and ANOLEA (http://protein.bio.puc.cl/cardex/servers/anolea/index.html). The best models where considered when  Verify 3D minimum values weresuperior to 0,1 internal score for most of aminoacids and when ANOLEA maximum value was of 5 E/kT for most of the aminoacids. Using these analysis and the previously described presence of a transmembrane domain,[1] a unique model was selected. The refined model (Figure 1) was obtained using UCSF Chimera software, Swiss-PDBViewer and LOBO (http://protein.cribi.unipd.it/lobo/). Afterwards, structural epitopes were predicted using the online Discotope softwear (http://www.cbs.dtu.dk/services/DiscoTope/). The antigenic regions were predicted in 34-38, 41, 50, 57, 61, 62, 68 -71, 73- 79, 81- 83 , 88 - 98, 104-132, 135, 142 -144, 150, 157 -158, 191-195  and 197 - 200 aminoacids regions. Linear BLE were predicted with the online ADBpred software (http://www.imtech.res.in/raghava/abcpred/) being estimated as located within 65- 84, 113- 131 and 151- 170 aminoacids regions. Conclusion: The identification of antigenic determinant regions of pathogenic microorganism proteins would allow the rational design of vaccines and antigens to be used in immunochemical assays. Experimental approches are time consumming, expensive and they may lead to not reliable results. The bioinformatics approach can provide a valuable source of information which complements the experimental results. Using free softwares we have predicted the tridimentional structure of T. gondii acute phase protein P35 and the putatives epitopes of this protein being the main antigenic region in the N-terminal region of the protein.  Referencies 1. Kimberly L, Carolyn G, Gary E: Identification and molecular characterization of GRA8, a novel, proline-rich, dense granule protein of Toxoplasma gondii. Mol. and Bioch. Parasit 2000, 105:25-37