Enolase of Angiostrongylus cantonensis: more likely a structural component?

The cloned enolase gene of Angiostrongylus cantonensis (AcEno) comprised 1,667 bp and encoded a peptide with 434 amino acid residues which lacked of a signal peptide but contained a transmembrane region, indicating that AcEno tends to be a structural component (intracellular or membrane protein). The real-time PCR revealed a meaningful difference in the expression level of AcEno in varied development stages. By immunolocalization, native AcEno was detected mainly in the cytoplasm in most tissues, such as parietal muscle, genital tracts, nerve ring, and alimentary canal where the energy consumption is high, but not as expected on the cuticle and hypodermis layer of the nematode. This suggests that the AcEno may be involved in a host of other biological functions, rather than a receptor of plasminogen or a component of excretory-secretory antigen. In addition, AcEno expressed alike in the nucleus, indicating that AcEno also involved in regulating the continuous growth and development of A. cantonensis in hosts. Despite of living in the vasculature at a certain stage of life cycle, AcEno was not localized in the outer surface of L3 and adults, indicating that A. cantonensis may have other virulence and immune evasion mechanisms.

Immunolocalization and developmental expression patterns of two cathepsin B proteases (AC-cathB-1, -2) of Angiostrongylus cantonensis.

In this study we have investigated the anatomic sites of expression and developmental expression patterns of two cathepsin B-like cysteine proteases (AC-cathB-1, -2) of Angiostrongylus cantonensis. The immunolocalization results revealed that native AC-cathBs were found present in the L1 and L3 larvae, female and male adults, and the AC-cathBs were localized mainly on the digestive tract of A. cantonensis and expressed at varied levels and in different patterns in the internal tissues according to their developmental stage. Consistent with the infective stage of L3 is a much more intense staining of AC-cathBs in the esophagus compared with the intestine. In contrast to L3, more abundant signals were located to the intestine of adults, suggesting that nutrition digestion likely to be the main function of the protease at this point. AC-cathBs fluorescent signals were present in excretory pore, excretory tube in lateral cords, and muscular esophagus of larvae, further supported the AC-cathB-1, -2 likely to be released by A. cantonensis as excretory/secretory products. Additionally, only the protein AC-cathB-2 was detected in the reproductive system, especially in the wall of vas deferens, uterus, and oviduct of the parasites, whether the AC-cathB-2 has some function in germ cells development and maturation need to be further characterized. Although the anatomic sites and expression patterns were different in larvae and adults and the corresponding function might not the same, AC-cathB-1 and -2 involved in the host-parasite interaction in addition to digestive function.