2246 Abstracts / Molecular Immunology 47 (2010) 2198–2294 recent progress made in our laboratory in defining the unique inter- action between FH and Td and the contribution of this interaction in serum resistance and (b) to present and discuss the highly unique structure of FhbB determined through X-ray crystallography. doi:10.1016/j.molimm.2010.05.147 224 Specific antibodies against SmTOR in S. mansoni infected and normal humans Corinne Lochmatter a,∗ , Claudia List b , Jürg A. Schifferli a a Immunonephrology, Department of Biomedicine, University Hospital Basel, Hebelstrasse 20, CH-4031 Basel, Switzerland b Molecular Diagnostics, Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel, Switzerland E-mail address: c.lochmatter@unibas.ch (C. Lochmatter). We have recently characterised SmTOR (CRIT), a protein expressed at the surface of Schistosoma mansoni. The highest expression of SmTOR was found in cercariae, the larval stage, which penetrates the skin of the human host (Lochmatter et al., 2009). This protein known to bind C2 and block C1 cleavage of C2 might pro- tect the worm from complement attack when it penetrates through the skin. The surface localisation of SmTOR makes it an interesting target for vaccination. Specific antibodies might not only attack the cercariae but also inhibit the function of SmTOR. In the present first step we investigated the specific antibody response against its first extracellular domain (ed1), which contains the C2 binding site. Recombinant SmTORed1 produced in E. coli that bound purified C2 in a concentration dependent manner was immobilised on an ELISA plate in order to measure IgG antibody levels in human sera. The sera were diluted 1/500 for the measurements, a concentration at which no more C2 binding was detectable. In addition, to evaluate the specificity of antibody binding, we established a competition experiment using recombinant Halo TM -tagged ed1 (including the respective control, HaloTag TM alone) covalently immobilised on beads and pre-incubated the sera with the construct. Peptides presented in this way in solution display a conformation that best approximates the native conformation of the whole molecule embedded in the membrane. In the first series of sera tested we found that 5 out of 20 patients from endemic region (25%, archived anonymised sera), but also 3 out of 19 normal individuals liv- ing in Switzerland (16%) show an IgG antibody response against SmTORed1. The binding could be inhibited in the competition assay in 3 individuals tested, 2 out of 3 infected and 1 out of 3 normal human sera. These initial data indicate a specific immune response in some humans against the SmTOR surface protein. The most likely explanation for the controls to have such antibodies as well is that they have been exposed to cercaria of bird schistosomes after swim- ming in fresh water lakes of Europe known to be infested with Trichobilharzia (cercarial dermatitis = swimmers’ itch). doi:10.1016/j.molimm.2010.05.148 225 Factor H facilitates adherence of Neisseria gonorrhoeae to com- plement receptor 3 on eukaryotic cells Sarika Agarwal a , Sanjay Ram a , Jutamas Ngampasutadol a , Sunita Gulati a , Peter F. Zipfel b,c , Peter A. Rice a a Division of Infectious Diseases and Immunology, University of Mas- sachusetts Medical School, Worcester, MA 01605, USA b Department of Infection Biology, Leibniz Institute for Natural Prod- ucts Research and Infection Biology, Beutenbergstr 11a, D-07743 Jena, Germany c Freidrich-Schiller University, Jena, Germany Neisseria gonorrhoeae can engage human complement recep- tor 3 (CR3) directly or through iC3b deposited on its surface. Gonococcal-bound factor H (fH) facilitates conversion of C3b to iC3b. fH itself binds to specific receptors on different cell types including CR3 on professional phagocytes. Certain non- professional phagocytes such as primary cervical epithelial cells also express CR3. We hypothesized that fH could bridge bacte- ria to CR3 and facilitate association of gonococci with host cells. Specificity of the fH–CR3 interaction was confirmed using human CR3-transfected CHO (CHO/CR3) cells. Using recombinant fusion proteins that comprised contiguous fH domains fused to murine Fc, we identified two regions in fH (comprises 20 short consen- sus repeat (SCR) domains) that bound to CR3; SCRs 18–20, bound strongly while weaker binding occurred through SCRs 6–10. Both regions also bound to an unsialylated porin (Por) B.1A strain of N. gonorrhoeae. Accordingly, fH-related protein 1 (CFHR1) (comprises fH SCRs 18–20 plus two dissimilar N-terminal SCRs) and fH-like molecule-1 (FHL-1) (contains fH SCRs 1–7) also bound to CHO-CR3 and to unsialylated N. gonorrhoeae. An SCR 6–20 protein construct enhanced binding of unsialylated PorB.1A gonococci to CHO-CR3. However, a construct that contained only the apparently relevant SCRs (6–7 and 18–20) bound to CHO-CR3 and to gonococci sepa- rately, but did not enhance bacteria-CR3 interactions, suggesting that the intervening SCRs (8–17) may have imparted a configura- tional and spatial requirement for fH to bridge gonococci to CR3 on eukaryotic cells. These results indicate adherence between fH- coated gonococci and CR3 and may provide a means for gonococci to gain sanctuary into non-professional phagocytes. doi:10.1016/j.molimm.2010.05.149 226 Trypanosoma cruzi calreticulin, a virulence factor that binds C1/C1q on the parasite surface G. Ramírez a , C. Valck a , M.C. Molina a , C.H. Ribeiro a , N. López a , G. Sánchez a , I. Maldonado a , V.P. Ferreira b , W. Schwaeble c , A. Ferreira a a Faculty of Medicine, ICBM, University of Chile, Santiago, Chile b Department of Medical Microbiology and Immunology, University of Toledo Health Science Campus, OH, USA c Department of Infection, Immunity and Inflammation, University of Leicester, UK Trypanosoma cruzi is the agent of Chagas’ disease an acute and chronic illness affecting 20 million people in Latin America, causing 50,000 deaths per year and considered the sixth most impor- tant neglected tropical disease worldwide. Trypomastigotes, the T. cruzi infective form, are highly resistant to complement activity, while epimastigotes, the non-infective form, are not. Several other molecules expressed by tripomastigotes contribute to explain this resistance (CRP, T-DAF, sialic acid and specific lipases, among oth-