A novel C-type lectin secreted by a tissue-dwelling parasitic nematode.
Many parasitic nematodes live for surprisingly long periods in the tissues of their hosts, implying sophisticated mechanisms for evading the host immune system. The nematode Toxocara canis survives for years in mammalian tissues, and when cultivated in vitro, secretes antigens such as TES-32. From the peptide sequence, we cloned TES-32 cDNA, which encodes a 219 amino-acid protein that has a domain characteristic of host calcium-dependent (C-type) lectins, a family of proteins associated with immune defence. Homology modelling predicted that TES-32 bears remarkable structural similarity to mammalian immune-system lectins. Native TES-32 acted as a functional lectin in affinity chromatography. Unusually, it bound both mannose- and galactose-type monosaccharides, a pattern precluded in mammalian lectins by a constraining loop adjacent to the carbohydrate-binding site. In TES-32, this loop appeared to be less obtrusive, permitting a broader range of ligand binding. The similarity of TES-32 to host immune cell receptors suggests a hitherto unsuspected strategy for parasite immune evasion.
Loukas
A
A
Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh, EH9 3JT, UK.
Mullin
N P
NP
Tetteh
K K
KK
Moens
L
L
Maizels
R M
RM
D000595:Amino Acid Sequence; D000818:Animals; D000947:Antigens, Helminth / Q000737:chemistry / Q000145:classification / Q000235:genetics; D001665:Binding Sites; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D018509:DNA, Helminth / Q000235:genetics; D017238:Genes, Helminth; D015801:Helminth Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008322:Mammals; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D017166:Toxocara canis / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity
D000947:Antigens, Helminth; D018076:DNA, Complementary; D018509:DNA, Helminth; D015801:Helminth Proteins; D037102:Lectins