download report - Istituto Pasteur
download report - Istituto Pasteur
download report - Istituto Pasteur
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
P a r t i c i p a n t s :<br />
Maria Teresa Fiorillo, researcher; Fabiana Paladini, post-doc<br />
fellow; Francesca Belfiore, Elisa Cocco, Adriana<br />
Magnacca, Elisa Nurzia, PhD students.<br />
C o l l a b o r a t i o n s :<br />
<strong>Istituto</strong> di Biologia Cellulare, CNR, Roma (Dr. Isabella Cascino);<br />
Department for Crystallography, FU Berlin, Germany (Prof.<br />
Wolfang Saenger); Institut für Immungenetik,<br />
Universitätsklinikum Charité Humboldt-Universität zu Berlin,<br />
Berlin, Germany (Prof. Andreas Ziegler, Dr Barbara<br />
Uchanska-Ziegler); Dipartimento di Scienze Mediche, Università<br />
di Cagliari (Prof. Alessandro Mathieu).<br />
Report of activity<br />
The project plan was subdivided in three different<br />
parts:<br />
Analysis of T cell responses specific for<br />
peptides sharing homology with the viral<br />
peptide pLMP2 in patients with AS versus<br />
healthy controls<br />
The viral pLMP2 (RRRWRRLTV) and the self<br />
pVIPR (RRKWRRWHL) peptides are unusually<br />
rich in arginines. This amino acid can undergo<br />
post-translational modifications consisting in citrullination.<br />
These modifications could confer some<br />
new antigenic properties to these peptides making<br />
the immune system able to recognize them as<br />
novel antigens and mount a cytotoxic T cell<br />
response (Beltrami et al., J Biol Chem. 2008,<br />
283:27189-99).<br />
We therefore have synthesized new peptides possessing<br />
citrulline instead of arginine, either in single<br />
(p1; p5 and p6) or in multiple positions (p1 and<br />
p5; p1 and p6; p5 and p6). One of these peptides,<br />
pVIPR-U5 (RRKWURWHL; U = citrulline), has<br />
already been analysed both at functional and crystallographic<br />
levels to verify whether the exchange of<br />
Principal investigator: Rosa Sorrentino<br />
Professor of Pathology<br />
Dipartimento di Biologia Cellulare e dello Sviluppo<br />
Tel: (+39) 06 49917706; Fax: (+39) 06 49917594<br />
rosa.sorrentino@uniroma1.it<br />
105<br />
Cellular and molecular immunology - AREA 5<br />
The role of HLA-B27 in autoimmunity: from the genetics to the<br />
function<br />
arginine to citrulline affects the display of this peptide<br />
by two human major histocompatibility antigen<br />
class I subtypes, HLA-B*2705 and HLA-B*2709.<br />
The crystal structures show that a modified selfpeptide,<br />
pVIPR-U5 (RRKWURWHL; U = citrulline)<br />
is presented by the two HLA-B27 molecules<br />
in distinct conformations. These binding modes differ<br />
not only drastically from each other but also<br />
from the conformations exhibited by the non-citrullinated<br />
peptide in a given subtype. The differential<br />
reactivity of HLA-B27-restricted cytotoxic T cells<br />
with modified or unmodified pVIPR supports the<br />
structural findings and shows that the presentation<br />
of citrullinated peptides has the potential to influence<br />
immune responses. Furthermore, citrullinated<br />
peptides such as pVIPR-U5 and pVIPR-U5+U6<br />
have been tested for their ability to induce self-reactivity<br />
in B*2705 patients with AS. So far, we have<br />
observed CD8+ T cell responses in 2 out of 5<br />
patients and the responsive CTL lines have shown<br />
either specificity for the citrullinated forms of<br />
pVIPR or cross-reactivity with the native peptide.<br />
This result supports the possibility that some circustances<br />
such as chronic inflammatory conditions<br />
that occur in AS could favor the activity of PAD<br />
(peptidylarginine deiminases), the enzyme involved<br />
in the arginine to citrulline conversion. T cells from<br />
B*2709 positive individuals have also been stimulated<br />
with citrullinated forms of pVIPR and so far no<br />
reactivity has been detected. In progress is a large<br />
screening in which CTL lines primarily driven by<br />
pLMP2, pVIPR and pVIPR-U5 or pVIPR-U5+U6<br />
are assayed against the complete panel of citrullinated<br />
pVIPR and pLMP2 analogs (the arginine at<br />
each position substituted by citrullines). These<br />
immunological results will be combined with structural<br />
data assessing the ability of the citrullinated<br />
peptides to form a stable complex with either<br />
B*2705 and B*2709 molecules and with spettroscopic<br />
measurements,i.e. circular dichroism (CD)<br />
and differential scanning calorimetric (DSC).