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RISK ASSESSMENT: FIELD RELEASE OF GENETICALLY MANIPULATED BACULOVIRUSES

Objective

BACULOVIRUSES (BVS) REPRESENT A GROUP OF DNA VIRUSES WHICH ARE EXCLUSIVE TO INSECTS AND CERTAIN CRUSTACEANS AND ARE NON-INFECTIVE IN VERTEBRATES. THEY ARE THEREFORE REGARDED AS SUITABLE FOR DEVELOPMENT AND DEPLOYMENT AS AGENTS OF PEST CONTROL. THE POSSIBILITY TO USE GENETIC ENGINEERING TO DEVELOP CUSTOM DESIGNED BVS THAT WILL ELUDE THE ACQUISITION OF RESISTANCE BY THE TARGET HOST IS ONE REASON FOR THE PROPOSED RISK ASSESSMENT RESEARCH. TO THIS END A BACULOVIRUS OF THE SUBGROUP A (INFECTING LEPIDOPTERA : NOCTUIDAE) HAS BEEN MODIFIED, INSERTING A NON-CODING LONG SYNTHETIC OLIGONUCLEOTIDE IN THE GENOME WHICH IS NOT ALTERING GENETIC INFORMATION AND CAN BE USER AS A MARKER. THE MARKER VIRUS WILL BE TESTED ON SUSCEPTIBLE CATERPILLARS IN LABORATORY STUDIES AND RELEASED IN THE ENVIRONMENT TO INFECT LARVAE AND ASSESS THE TIME-SPACE DISTRIBUTION, INFECTION POTENTIAL AND EVOLUTION OF THE AGENT. THE EVENTUAL AIM OF THE STUDY IS TO ENGINEER INTO A BACULOVIRUS THE B. THURINGENSIS TOXIN OR OTHER GENES SO THAT IT WILL INHIBIT LARVAL DEVELOPMENT OF SPECIFIC LEPIDOPTERAN, NAMELY M. BRASSICAE, INFECTING CABBAGE PLANTS. THE LABORATORY HAS EXTENSIVE EXPERIENCE ON THE BIOLOGY AND CONTROL OF CODDING MOTH BACULOVIRUSES AND THE COLLABORATING UK GROUP HAS WIDE EXPERIENCE IN CLONING AND GENETIC ENGINEERING TECHNIQUES. THE JOINT EFFORT WILL BE VERY USEFUL IN STANDARDIZING THE PROCEDURES OF IDENTIFICATION OF THE AGENT IN THE CONTEXT OF ITS ENVIRONMENT.
A contained model ecosystem has been developed in which the atmospheric conditions (wind, rain and sunlight) in a 0.6 x 1.2 m part of a cultivated field can be imitated. The ecosystem was used for simulated field release of insect viruses to investigate their behaviour in the environment.

Assessing the risk of release of a genetically engineered baculovirus depends on a sound knowledge of the ecology of the wild type from which, through cloning, it was derived. Ecological deviations in the recombinant virus can thus be identified. To give wide ecological coverage, 2 baculoviruses, each infective, one a pest of pine forest (pine beauty moth) and the other a pest of agricultural crops (cabbage moth), and a wild type (AcNPV) and its recombinant clone (AcNPV/plOZ) were studied. Extensive field observations were made to permit identification of ecological aspects suitable for study in severely contained microcosms specially developed for the purpose. The behaviour of wild type viruses and the recombinant were studied in microcosms.

The host ranges of cabbage moth and pine beauty moth NPVs covered 4 of 14 families of Lepidoptera. 4 clones of each NPV had different infectivity levels, up to 4.5 x the wild types. In the field, virus persisted in soils for at least 3 years. The main agents of local dispersal were opilionids, excreting active virus for 100 h postingestion. Birds spread virus widely; 40% of individuals and 9 of 15 species excreted active virus. Cabbage moth virus was recovered 20 km from a point of introduction. In microcosms containing field crops, simulated rain dispersed viruses. In general 1 to 10% remained on plants but the soil contained 90 to 99%; there was none in percolation water. Air flow, rain splash, parasites and aphids dispersed viruses. Despite similar levels of infectivity of wild and recombinant viruses, less recombinant virus was produced in microcosms. Recombinant virus was less persistent than the wild type.
THE PROJECT CONCERNS RISK ASSESSMENT ANALYSES OF THE RELEASE INTO THE ENVIRONMENT OF A GENETICALLY ALTERED INSECT THAT IS USED IN THE CONTROL OF AGRICULTURAL AND FOREST PESTS. THE VIRUS IS THE OCCLUDED BACULOVIRUS MBNPV, NATURAL HOST OF THE LEPIDOPTERAN MAMESTRA BRASSICAE WHICH IS A PEST OF CABBAGE AND OTHER FIELD CROPS IN THE WESTERN PALAEARTIC. MBNPV IS CROSS-INFECTIVE TO THE MOTH P. FLAMMEA, A PEST OF PINE FORESTS IN THE SAME GEOGRAPHIC AREAS. THE RISK ASSESSMENT WILL MEASURE THE PENETRATION OF THE SPATIAL, TEMPORAL AND BIOLOGICAL WORLDS FROM A SINGLE RELEASE POINT IN AN AGRICULTURAL SYSTEM. THE VIRUS THAT WILL BE EMPLOYED WILL CONTAIN A NON-CODING OLIGONUCLEOTIDE MARKER, PERMITTING VIRUS IDENTIFICATION. THE MOVEMENT OF THE MARKER VIRUS WILL BE FOLLOWED FIRST IN SIMULATED AND RESTRICTED AGRICULTURAL ECOSYSTEMS, CONTAINING CABBAGE PLANTS, WEED SPECIES ANND SOIL AS SUBSTRATE. FIELD ASSESSMENT WILL BE STUDIED BY RELEASING THE MARKER VIRUS IN AN OPEN AGRICULTURAL SYSTEMS, STARTING FROM A VERY SMALL PLOT OF A CABBAGE FIELD. THIS PROJECT IS CONDUCTED IN COLLABORATION WITH THE OXFORD GROUP WHO WILL STUDY PENETRATION OF THE MARKER BACULOVIRUS IN A FOREST SYSTEM.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Biologische Bundesanstalt für Land- und Forstwirtschaft
Address
Messeweg 11-12
38104 Braunschweig
Germany

Participants (1)

NATURAL ENVIRONMENT RESEARCH COUNCIL
United Kingdom
Address
North Star Avenue, Polaris House
SN2 1EU Swindon