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Evaluation of the immune responses induced by four targeted DNA vaccines encoding the juvenile liver fluke antigen, cathepsin B in a mouse model

Jayaraj, Ramamoorthi, Piedrafita, David, Spithill, Terry W. and Smooker, Peter M. (2012). Evaluation of the immune responses induced by four targeted DNA vaccines encoding the juvenile liver fluke antigen, cathepsin B in a mouse model. Genetic Vaccines and Therapy,10:Article 7.

Document type: Journal Article
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IRMA ID 82794376xPUB12
Title Evaluation of the immune responses induced by four targeted DNA vaccines encoding the juvenile liver fluke antigen, cathepsin B in a mouse model
Author Jayaraj, Ramamoorthi
Piedrafita, David
Spithill, Terry W.
Smooker, Peter M.
Journal Name Genetic Vaccines and Therapy
Publication Date 2012
Volume Number 10
ISSN 1479-0556   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84865570986
Start Page Article 7
Total Pages 9
Place of Publication United Kingdom
Publisher BioMed Central Ltd.
HERDC Category C1 - Journal Article (DIISR)
Abstract Background
Liver fluke can infect cattle and sheep, and is also emerging as a human pathogen in developing countries. Cathepsin B (Cat B2) is a major cysteine protease secreted by the juvenile flukes. To enhance the immune responses of Cat B2, the cDNA sequence was fused with four different DNA vaccine vectors. The induced cellular and antibody responses were compared in vaccinated mice.


The following recombinant DNA vaccine constructs were constructed: empty vector VR1012 as negative control, cytoplasmic construct pVR1012 Cat B2, secretory construct pVR1020 Cat B2, chemokine-fused construct pMCP3 Cat B2 and lymph node targeting construct pCTLA-4 Cat B2. Plasmids were constructed using standard procedures, and positive constructs screened and selected using restriction digestion analysis followed by sequence analysis. The constructs were then tested in Cos-7 cells for in vitro expression, which was analysed using immunoblotting. Subsequently, female BALB/c mice were immunised with DNA constructs as vaccines. Elicited antibody responses were measured using ELISA. The ratio between IgG1 and IgG2a antibody responses was estimated among different vaccine groups. IgG antibody avidity assay was performed and the relative avidity index was calculated. The induced cytokine production from splenocytes of vaccinated animals was estimated using ELISPOT.


DNA vaccine constructs carrying Cat B2 were expressed in Cos-7 cell lines and encoded protein was recognised using western blotting using rat anti- cathepsin B antibody. DNA vaccines elicited high Cat B2- specific IgG, IgG1, IgE and also modest IgG2a antibody responses. Cat B2 specific IL-4 T cell responses were also observed in Cat B2 vaccinated mice. The comparison of immunogenic potential in each of these constructs was demonstrated as enhanced antibody responses on the lymph-node targeting vector pCTLA-4 Cat B2, the high antibody avidity of chemo-attractant pMCP3 Cat B2 and stronger T cellular responses of non-secretory DNA vaccine pVR1012 Cat B2 in vaccinated animals.


This study showed that the targeting DNA vaccine strategies enhanced specific immune responses to juvenile fluke Cat B2. The results of our current study have demonstrated that a gene-based vaccine as an immunotherapeutic approach to combat Fasciola infection may be feasible.
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Additional Notes © Jayaraj et al.; licensee BioMed Central Ltd. 2012 This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://​creativecommons.​org/​licenses/​by/​2.​0 ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

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