The major allergen of the Parietaria pollen contains an LPS-binding region with immuno-modulatory activity

Background: The major allergens in Parietaria pollen, Par j 1 and Par j 2, have
been identified as lipid transfer proteins. The family of the Par j 1 allergens is
composed of two isoforms, which differ by the presence of a 37 amino acid peptide
(Par37) exclusive to the Par j 1.0101 isoform. The goal of this study was to
elucidate the biological properties of the Par37 peptide.
Methods: In silico analysis, spectrofluorimetric experiments and in vitro cell culture
assays were used to identify the biological properties of Par37. In addition, a
mouse model of sensitization was used to study the influence of Par37 in the murine
immune response.
Results: In silico analysis predicted that Par37 displays characteristics of a host
defence peptide. Spectrofluorimetric analysis, real-time PCR and ELISA assays
demonstrated that Par37 possesses an LPS-binding activity influencing cell signalling
in vitro. In RAW264.7 cells, LPS-induced IL-6 and TNF-a transcription and
translation were inhibited after preincubation with Par37. Consistent with these
data, inhibition of IFN-c secretion was observed in murine spleen cells and in
human PBMC. Finally, mice immunized with the two Par j 1 isoforms differing
in the presence or absence of the Par37 peptide showed different immunological
behaviours in vivo.
Conclusions: This study demonstrates that the Par j 1.0101 allergen displays LPSbinding
activity due to the presence of a 37 amino acid COOH-terminal region
and that this region is capable of influencing cytokine and antibody responses
in vitro and in vivo.