Cloning and characterization of a mannose binding C-type lectin gene from salivary gland of Aedes albopictus

Background: the studies on sialomes have shown that hematophagous mosquito saliva consists of a lot of pharmacologically active proteins,in which c-type lectins have been identified and regarded as an important component of saliva. the previous studies showed that c-type lectins play crucial roles not only in innate immunity but also in promoting disease transmission in mammals. however,the function and mechanism of c-type lectins from the mosquito sialome is still elusive. methods. a putative c-type lectin gene (aalb-ctl1) was cloned and expressed from aedes albopictus by rt-pcr. the deduced amino acid sequence was analyzed by bioinformatic methods. the gene expression profiles in different tissues and various blood-fed stages of ae. albopictus were examined by real-time qrt-pcr and the biological functions of the recombined mature aalb-ctl1 were tested by hemagglutination and sugar inhibitory agglutination assays. moreover,the capabilities of raalb-ctl1 against microorganisms were measured by microbial-agglutination assay. results: the full-length open reading frame (orf) of aalb-ctl1 consisted of 462 bp,encoding 153 amino acid residues. the deduced amino acid sequence contained a putative signal peptide of 19 amino acids. it also contained a crd domain with a wnd (trp137-asn 138-asp-139) motif that needed calcium for the hemagglutinating activity and an imperfect eps (glu128-pro 129-ser130) motif that had a predicted ligand binding specificity for mannose. the mrna level of aalb-ctl1 was much higher in female mosquito salivary gland than those in fat body and midgut which was down-regulated in salivary gland after blood feeding. the raalb-ctl1 contained not only hemagglutinating activity and a high affinity with mannose but also agglutinating activity against yeast c. albicans and gram-positive bacteria s. aureus in ca2+ dependent manner. conclusion: aalb-ctl1 was a mannose-binding c-type lectin and constituted one of the important components in saliva of ae. albopictus,which could be involved in the defense against yeast and gram-positive bacteria infection. © 2014 cheng et al.; licensee biomed central ltd.