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The ABA-1 allergen of Ascaris lumbricoides: sequence polymorphism, stage and tissue-specific expression, lipid binding function, and protein biophysical properties

Published online by Cambridge University Press:  01 February 2000

Y. XIA ,
H. J. SPENCE ,
J. MOORE ,
N. HEANEY ,
L. McDERMOTT ,
A. COOPER ,
D. G. WATSON ,
B. MEI ,
R. KOMUNIECKI  and
M. W. KENNEDY
Y. XIA
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK Present address: Department of Pathology, School of Medicine, University of Louisville, Louisville, KY40292
H. J. SPENCE
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK Present address: Beatson Institute of Cancer Research, University of Glasgow, Glasgow G61 1QH
J. MOORE
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
N. HEANEY
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
L. McDERMOTT
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
A. COOPER
Affiliation:
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
D. G. WATSON
Affiliation:
Department of Pharmaceutical Sciences, University of Strathclyde, Glasgow G1 1XW
B. MEI
Affiliation:
Department of Biology, University of Toledo, Toledo, OH 43606, USA Present address: Department of Nutritional Sciences, University of California, Berkeley, Berkeley, CA 94720, USA.
R. KOMUNIECKI
Affiliation:
Department of Biology, University of Toledo, Toledo, OH 43606, USA
M. W. KENNEDY
Affiliation:
Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK
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Abstract

The ABA-1 protein of Ascaris lumbricoides (of humans) and Ascaris suum (of pigs) is abundant in the pseudocoelomic fluid of the parasites and also appears to be released by the tissue-parasitic larvae and the adult stages. The genes encoding the polyprotein precursor of ABA-1 (aba-1) were found to be arranged similarly in the two taxa, comprising tandemly repeating units encoding a large polyprotein which is cleaved to yield polypeptides of approximately 15 kDa which fall into 2 distinct classes, types A and B. The polyprotein possibly comprises only 10 units. The aba-1 gene of A. lumbricoides is polymorphic, and the majority of substitutions observed occur in or near predicted loop regions in the encoded proteins. mRNA for ABA-1 is present in infective larvae within the egg, and in all parasitic stages, but was not detectable in unembryonated eggs. ABA-1 mRNA was confined to the gut of adult parasites, and not in body wall or reproductive tissues. Recombinant protein representing a single A-type unit for the A. lumbricoides aba-1 gene was produced and found to bind retinol (Vitamin A) and a range of fatty acids, including the pharmacologically active lipids lysophosphatidic acid, lysoplatelet activating factor, and there was also evidence of binding to leukotrienes. It failed to bind to any of the anthelmintics screened. Differential Scanning Calorimetry showed that the recombinant protein was highly stable, and unfolded in a single transition at 90·4 °C. Analysis of the transition indicated that the protein occurs as a dimer and that the dimer dissociates simultaneously with the unfolding of the monomer units.

Keywords

Ascaris lumbricoidesABA-1 allergenpolymorphismnematode polyprotein allergens/antigensfatty acid binding protein
Type
Research Article
Information
Parasitology , Volume 120 , Issue 2 , February 2000 , pp. 211 - 224
Copyright
2000 Cambridge University Press

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