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Molecular cloning of Taenia taeniaeformis oncosphere antigen genes
W G Cougle1, M W Lightowlers, H O Bogh
1University of Melbourne, Veterinary Clinical Centre, Werribee, Victoria, Australia.
Abstract:
Infection of mice with the cestode Taenia taeniaeformis exhibits several important features common to other cestode infections, including the ability to vaccinate with crude antigen mixtures. Partial purification of the protective oncosphere antigens has been reported with a cutout from deoxycholate (DOC) acrylamide gels; this cutout was called fraction II (FII), and comprises approximately 10% of total DOC-soluble oncosphere antigen. Western blots of DOC gels probed with anti-FII antisera revealed a series of 3-5 discrete bands within the FII region. Further fractionation of the FII antigens on DOC gels was impractical due to limitations in supply of oncospheres, so a cDNA library was constructed from 150 ng of oncosphere mRNA and screened with alpha-FII antisera. Two distinct clone families were identified, oncA and oncB. Antibodies affinity-purified on either of two representative members, oncA1 and oncB1, recognised all the FII bands. Individual FII bands excised from a DOC gel resolved into an overlapping series of molecules when re-run on SDS-PAGE, indicating that each FII band consisted of several polypeptides of differing molecular weight. Immunoprecipitates resolved on SDS-PAGE revealed that alpha-FII recognised 3 major oncosphere antigens, of 62, 34 and 25 kDa; antisera against oncB precipitated both the 34- and 25-kDa antigens, whereas alpha-oncA antisera precipitated the 62-kDa antigen. We conclude that oncA and oncB encode the major antigens in the FII complex. The 62-kDa antigen encoded by oncA1 was the only common antigen precipitated by anti-FII and two other antisera raised against different protective extracts, suggesting that it may be a protective component in all three. Southern blot results indicate that oncA and oncB are distinct genes present at low copy number in the genome. Evidence is also presented suggesting that some cestode mRNAs, including oncA, may use variant polyadenylation signals.
Insights
Researchers identified key antigens from the parasite Taenia taeniaeformis, crucial for developing vaccines against cestode infections. Two gene families, oncA and oncB, encode these protective antigens, with a 62-kDa antigen showing promise for broad vaccine applications.
Area of Science:
- Parasitology
- Immunology
- Molecular Biology
Background:
- Taenia taeniaeformis infections in mice share characteristics with other cestode infections.
- Vaccination with crude antigen mixtures shows protective potential.
- Fraction II (FII) represents partially purified protective oncosphere antigens from deoxycholate (DOC) acrylamide gels.
Purpose of the Study:
- To identify and characterize the specific antigens within the FII fraction responsible for protective immunity.
- To determine the genetic basis of these protective antigens.
- To investigate potential common protective components across different cestode extracts.
Main Methods:
- Construction and screening of a cDNA library from oncosphere mRNA using anti-FII antisera.
- Antibody affinity purification and Western blot analysis to identify antigen-antibody interactions.
- Immunoprecipitation and SDS-PAGE to resolve and characterize antigen molecular weights.
- Southern blot analysis to assess gene copy number and distinctness.
Main Results:
- Two distinct clone families, oncA and oncB, were identified, encoding antigens recognized by anti-FII antisera.
- Antibodies against oncA and oncB recognized all FII bands, indicating they represent the major FII antigens.
- Three major oncosphere antigens (62, 34, and 25 kDa) were identified; oncA encodes the 62-kDa antigen, while oncB encodes the 34- and 25-kDa antigens.
- The 62-kDa antigen (encoded by oncA1) was the only antigen recognized by anti-FII and two other protective antisera.
Conclusions:
- The gene families oncA and oncB encode the primary antigens within the FII complex of Taenia taeniaeformis.
- The 62-kDa antigen is a potential cross-protective component effective against multiple cestode extracts.
- oncA and oncB are distinct, low-copy-number genes, and cestode mRNAs may utilize variant polyadenylation signals.