Calreticulin from the intestinal nematode Heligmosomoides polygyrus is a Th2-skewing protein and interacts with murine scavenger receptor-A

Helminth infections are commonly associated with a Th2 immune response, yet only a few parasite molecules involved in triggering such immune responses have been identified. Here, we describe the Th2-skewing property of calreticulin of Heligmosomoides polygyrus (HpCRT). HpCRT is a secreted protein most abundantly expressed by tissue invasive larvae (L4). Native HpCRT purified from adult worm extract (nHpCRT) stimulated robust IL-4 release from CD4(+) T cells of H. polygyrus infected mice. Interestingly, CD4(+) T cells also produced significant amounts of IL-10 while IFN-gamma was not detectable. Likewise, immunization with recombinant HpCRT (rHpCRT) without extrinsic adjuvant led predominantly to a specific IL-4 production implying the innate ability of HpCRT to drive Th2 responses. The triggering of a Th2-skewed immune response to rHpCRT is corroborated by the induction of HpCRT-specific IgG1 and IgE antibodies. Furthermore, rHpCRT bound to scavenger receptor type A (SR-A) on dendritic cells, and interaction of HpCRT with SR-A led to internalization of HpCRT that could be partially blocked by competition with SR-A ligands as well as with an anti-SR-A monoclonal antibody. Hence, our data imply that nematode calreticulin interacts with a mammalian scavenger receptor and at the same time induces a Th2 response.