3.2 Microbiology/Parasitology
3.2.1 PBC 227: Transgenic worms for the control of possums
| Programme Title: | Transgenic worms for the control of possums. |
| Programme Leader: | Dr Warwick Grant |
| Institution: | AgResearch |
Programme Goal: To develop techniques that allow the production of transgenic Parastrongyloides trichosuri (a nematode parasite of possums) producing a protein(s) that interfere(s) with the growth, reproduction or longevity of its possum host.
Rationale: Sustainable biological control of possums via immunocontraception or a similar means requires an efficient, self-disseminating vector that is safe, specific to possums and will persist in the possum population. A strong candidate for the role of vector for an immunocontraceptive protein (or toxin etc) is Parastrongyloides trichosuri.
P. trichosuri is a nematode parasite of the possum. It is widely distributed in possums on the North Island of New Zealand but is endemic in only one location on the South Island, presumably as the result of a recent introduction. The dynamics of the introduction and spread of the parasite into a naïve population has is being studied and the results one year after a deliberate introduction suggest that P. trichosuri will be a sustainable, self-disseminating vector for biological control. Other favourable features of P. trichosuri are:
- there is strong evidence that it is host specific;
- it does not elicit a strong protective immune response in its host, so the host remains infected for long periods and is susceptible to re-infection i.e. the infection is chronic;
- it does, however, elicit a host antibody response, so a protein produced by the parasite is likely to be exposed to the host immune system;
- it does not cause serious pathology or morbidity in the host; and
- it is capable of completing an apparently indefinite number of free-living generations outside the host. This acts to sustain and amplify its presence in the environment once released.
Previous work in this program has shown that it is possible to transform this parasite with foreign DNA encoding reporter genes. The next steps in the development of P. trichosuri as a biocontrol agent are to refine the transformation technology and to develop suitable DNA vectors for the expression of biologically active proteins (e.g. immunocontraceptives) in the parasite.
Objective 1
Objective Title: Refinement of post-transformation cultures.
Research Leader: Dr Warwick Grant.
Description:
The current method (microinjection of adult parasite females) has produced transgenic worms, based on both reporter gene activity and on the presence of transforming DNA, but the frequency of success is low. The aim of this objective is to explore alternative post injection culture methods that may increase the frequency with which transformants are recovered.
Objective 2
Objective Title: Alternative transformation technologies.
Research Leader: Dr Warwick Grant.
Description
Microinjection is technically demanding and requires adult female parasites, which have to be recovered from infected possums. Transformation of the free-living stages of the nematode is likely to be simpler, faster and cheaper but to date microinjection of the adult free-living worms has been unsuccessful. Alternatives to microinjection that will be explored are electroporation, biolistic particle bombardment and pantropic retrovirus.
Objective 3
Objective Title: DNA vectors for controlled expression.
Research Leader: Dr Warwick Grant.
Description
The delivery of a protein to possums via expression in P. trichosuri requires that the protein be expressed and secreted by the parasitic stages of the nematode. This in turn requires (a) that expression of the transgene is controlled by a promoter with activity in parasitic stages and (b) the transgene encode a secretory signal peptide fused to the protein of interest.
Contact for Enquiries
Farm Monitoring Programme Manager
Monitoring and Evaluation
MAF Policy
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0623
Fax: +64 4 894 0741
Contact this person
