Cloning and characterization of a novel gene encoding 16 kDa protein (Ac16) from Angiostrongylus cantonensis.

Angiostrongylus cantonensis is the most common infectious cause of eosinophilic meningitis or meningoencephalitis. A novel gene (AC16) was isolated from a cDNA library of A. cantonensis fourth-stage larvae. The putative 16-kDa protein has 149 amino acids and is homologous to an immunodominant hypodermal antigen (IHA16) from Ancylostoma caninum (identities = 57%). In this paper, we cloned the gene and purified the recombinant Ac16 (rAC16) protein. Real-time quantitative PCR revealed that Ac16 was expressed significantly higher in the fourth-stage larvae and adult worms derived from rats than that in the fourth-stage larvae derived from mice. Moreover, sera from rat (permissive host) infected with A. cantonensis detected Ac16 by Western blot, while sera from infected mouse (non-permissive host) could not. The results implied that Ac16 was related to the parasitic adaptation of A. cantonensis in different hosts and non-permissive host mouse had no circulating antibody to the antigen Ac16 from A. cantonensis and thus might contribute to understanding the mechanism of parasite immune evasion. Furthermore, we evaluated the ability of Ac16 antibody diagnosing A. cantonensis infection by an indirect enzyme-linked immunosorbent assay. The results showed that the Ac16 antibody had a 79.17% sensitivity to rAC16 and 83.33% to crude adult worm antigens (CA) (P > 0.05), while the specificity to rAC16 and to CA were 95.89% and 86.30% respectively (P < 0.05), thus implying that rAc16 may constitute a putative serodiagnostic antigen for Angiostrongyliasis cantonensis.