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Optimization of biological control strategies through disruption of pest immune responses. - PS2123

The overall objective of the work is to devise alternative plant protection technologies which will lead to a reduction in the usage of broad-spectrum, neurotoxic pesticides. We aim to do this by focusing on ways of selectively suppressing the key immune responses in target pest insect(s) which ordinarily protect them from potential pathogens in their environment, and those used in biological control strategies.

Insects, including agricultural and horticultural pests, possess an impressive armoury of both cellular and humoral immune responses which help to protect them against potential pathogens, including fungi, bacteria and protozoa which might be employed in biological control strategies. We have already determined that adult female Pimpla hypochondriaca (an endoparasitic wasp which lays its eggs in the haemocoel of its host), injects a venom into the host prior to ovipostion, in order to suppress host immune responses which would otherwise kill the wasp progeny. A number of the active venom factors have been biochemically identified, and we have isolated a single venom factor with immunosuppressive properties. The gene for this protein, and another immunosuppressive protein have been cloned, and recombinant protein expressed in bacteria. At present, however, only one of these proteins is soluble and thus available for functional studies. Of great importance, using a number of concept-proving bio-assays, we have demonstrated that injection of the soluble recombinant protein into the haemocoel of two lepidopteran pests (Lacanobia oleracea and Mamestra brassica), increases their susceptibility to the widely used bacterial biological control agent, Bacillus thuringiensis. In the current project, we aim to extend this work by isolating and cloning the genes for additional venom immunosuppressive factors in order to determine if they are more effective than the one tested previously, or can act synergistically with it. We then aim to determine if a selected immunosuppressive factor can increase the susceptibility of L. oleracea and M. brassicae to other biological control agents (eg. fungi), and if such a factor can increase the susceptibility of other commercially significant pest insects to B. thuringiensis. In addition, a major aim which is key in progressing this work towards practical application, is the optimisation of a procedure for delivering a selected immunosuppressive factor to pest insects via an oral route.

The approach we have adopted has the potential to lead to the development of novel biological control strategies that are not only effective, but which are also target-specific, environmentally friendly and sustainable. These aims address Defra policy objectives relating to the minimization or eradication of broad spectrum, toxic pesticides (including organophosphates), which in turn responds to professional and public concern about their current and future use. It is anticipated that the results generated from this work will enable us to forge alliances with relevant companies so that they can be further developed into novel, environmentally sensitive and sustainable pest management strategies, which will offer the grower realistic levels of efficacy with negligible chance of adverse impact on the environment.
Previously, utilising laboratory based assays, we proved the concept that suppression of key immune responses in a target pest insect can increase the bio-pesticidal properties (and thus efficacy) of a commercially available biological control agent. The primary aims of the current proposal are as follows. Firstly, to determine if this approach/concept can be applied to other pest insects and to other biological control agents. Secondly, we need to develop a way of delivering the immunosuppressive agent(s) in a practical (field-oriented) manner.

The specific objectives of the work are as follows:

1. To date, we have one soluble and one insoluble recombinant immunosuppressive protein. Thus, the aim of the first scientific objective is to extend the characterization of factors present in Pimpla hypochondriaca venom which manipulate (suppress) immune defences in a chosen pest insect(s). In particular, to clone the genes for such factors, to express them in bacteria to obtain recombinant protein, and to confirm immunosuppressive activity.

2. To enhance the efficacy of a chosen immunosuppressive protein by performing experiments which help us to understand the mode of action of such a protein within a pest insect in conjunction with a biological control agent. Furthermore, to determine if the susceptibility of a chosen pest insect to a biological control agent can be increased following oral delivery (as opposed to injection) of a recombinant immunosuppressive protein.

3. To investigate the market range of our work by determining if the concept that immunosuppression of a pest results in an increase in efficacy of a biological control agent, can be applied to other pest insects in conjunction with other biological control agents. Also, to determine if a chosen immunosuppressive protein has any adverse effects on the viability of selected UK beneficial insect(s).

4. To determine if oral delivery of an immunosuppressive factor can be improved. To achieve this, we will determine if a smaller, biologically active immunosuppressive factor can be produced (utilising a molecular and/or proteomic approach). We will then determine if this modified factor can be delivered more effectively than the ‘native’ factor to the insect haemocoel (its site of action) utilising an oral route (i.e. following ingestion).

Project Documents
• FRP - Final Report : Optimization of biological control strategies through disruption of pest immune responses   (366k)
Time-Scale and Cost
From: 2008

To: 2011

Cost: £503,811
Contractor / Funded Organisations
Central Science Laboratory
Biological Control              
Biological Effects              
Biotech-non GM              
Crop Pests              
Molecular Biology              
Pest Control              
Fields of Study
Pesticide Safety