The role of saliva of Anopheles stephensi in inflammatory response: identification of a high molecular weight neutrophil chemotactic factor

Mosquito bites can elicit dermal hypersensitivity reactions, but little is known about the chemotactic factors for host leukocytes in mosquito saliva. In this study, we determined that saliva from a malarial vector mosquito, Anopheles stephensi, possesses intense neutrophil chemotactic activity. In contrast, the midgut extract had only marginal neutrophil chemotactic activ ity. Eosinophil chemotactic activity was detected in the midgut but not in the saliva. According to the results of size-exclusion HPLC on a G3000SW co lumn and Western blot analysis, the apparent molecular weight (MW) of the m ain neutrophil chemotactic factor (NCF) was estimated to be 200 kDa. NCF co uld bind with IgG from the pooled serum of Solomon islanders, whereas not w ith that of healthy Japanese. NCF activity was increased upon heating to 56 degreesC for 30 min or protease digestion, whereas it was affected by peri odate treatment. Protease-digested NCF and naive NCF bound to lentil lectin -Sepharose, and both were eluted with a competitive sugar, methyl-alpha -D- glucoside. These results indicate that A. stephensi saliva-derived NCF is a high MW glycoprotein, and its protein moiety is important for neutrophil c hemotactic activity. This NCF is thought to contribute to the inflammatory reactions through the accumulation of neutrophils at the site of the mosqui to bite.