Haemonchus contortus calreticulin binds to C-reactive protein of its host, a novel survival strategy of the parasite

Calreticulin (CalR), a Ca2+ binding multifunctional protein, is secreted by the parasitic nematode Haemonchus contortus. We have earlier observed binding of this protein to a 24-kDa polypeptide (p24) present in an enriched preparation of prothrombin. In the present study, the identity of p24 was established as a C-reactive protein (CRP) by several criteria. CalR binding to CRP is an elegant strategy devised by the parasite to survive in the host. The secreted CalR may achieve this either by limiting the free concentration of CRP, which has antiparasite activity or inhibit the activation of the classical complement pathway triggered on binding of CRP to C1q protein. CalR binding to CRP would also ensure a check on the procoagulant activity of the CRP enabling parasite to feed on the host blood. Thus, targeting CalR could be a novel strategy to tackle this parasite, which has developed resistance to many anthelmintics.