Several plant viruses were identified as being regularly used as vectors for protein expression and gene silencing studies.
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The use of the latest version of the software is recommended which is available at the Adobe website via the link on this page. Skip to content Skip to navigation. Health and Safety Executive. Home News. RR - Containment of GM plant viruses being developed as gene technology vectors This project was carried out with a view to providing recommendations for good practice to ensure that genetically modified GM plant viruses engineered to produce novel proteins, such as vaccines, in plants remain contained within authorised research facilities and do not pose a risk of causing harm through accidental release escape into the wider environment.
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The considerations that we present here are specifically designed to prevent the accidental premature release of a transgene before it has been evaluated for potential effects on the target organism's ecological relationships and the environment and the release has been approved by authorities who are responsible for public and environmental safety. Case-by-case assessments should address the intended use and design of the IGF, potential risks of the IGF strategy, appropriate containment, and utility for population replacement or suppression.
Some IGFs are predicted by models to have a low population frequency threshold that must be exceeded to invade, hence releases of only a few individuals such as might occur as a result of containment failure could theoretically result in invasion Marshall Arthropods containing these potentially low-threshold IGFs may warrant higher containment stringency and management procedures than those applied to arthropods containing high-threshold IGFs or noninvasive genetic modifications. Under neutral fitness conditions and without containment measures, models predict that these systems could persist even for release sizes as small as five individuals Marshall An increase in the prevalence of a transgene in a population can result in broadening spatial distribution of the IGF.
Increasing prevalence and distribution of driving transgenes, however, is not certain and depends upon many factors, including the fitness conferred on individuals carrying the IGF, the biological permissiveness of the season when release occurs, and the drive strength Eckhoff Other systems such as Medea Hay et al.
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Small numbers of escapees carrying these systems are likely to be lost through genetic drift Marshall ; however, larger accidental releases may result in spread, and local population structure may assist this. Underdominance-based approaches are unlikely to spread subsequent to small accidental releases Marshall and are likely confinable to isolated populations and could be eliminated through releases of wild-type individuals Marshall and Hay These systems display threshold properties such that a superthreshold release is required for spread, and this is unlikely to be achieved through migration to neighboring populations.
We anticipate that containment and management requirements for these strains will not need to be as stringent as for IGFs without such high thresholds. When present at low frequencies in populations, alleles and noninvasive i. In contrast, the increase in frequency of driving transgenes and other IGFs in populations without conferring any specific selection advantage means that they—as a class of transgenes—can potentially increase in frequency over time and spread spatially through preferential inheritance and population dispersal and migration.
This presents a novel situation that those who are responsible for conducting research with arthropods safely may be unfamiliar with. To illustrate how an accidental release resulting in establishment of the transgene in wild populations in the vicinity might occur, we describe two scenarios:. Briefly, ACL-2 recommends sealed ventilation and plumbing penetrations, vestibules, isolated spaces for work with transgenic organisms, devitalization before disposal, restricted access, and shares features of other guidance listed in Table 1.
The ACGs have no legal authority, but are often used, particularly in the United States, in describing appropriate measures for containment of arthropods not covered elsewhere see below regarding U. Containment failure due to facility shortcomings, human error, or other reasons allows a fertile individual to escape into a wild population near the facility, resulting in predominance of the IGF in the wild population. In the context of this discussion, we stress that the probability of a driving transgene becoming established in wild populations is much greater than that of a non-IGF.
Table 1. In a second scenario, a wild-type nontransgenic strain is being handled in a laboratory that also handles the same species or a species that mates compatibly, but containing an IGF, both strains being under ACL-2 containment. This situation is common because many laboratories that create transgenic insects maintain nontransgenic strains as phenotypic references in the form of wild-type comparators or as the host strain. According to most guidance described further below , both should be maintained at the highest containment level that applies to either.
Unbeknownst to the insectary manager, contamination of the wild-type strain has recently occurred due to accidental transfer of individuals from the IGF-containing strain. The wild-type strain is presumed to be free of any IGF and is shipped to a collaborating laboratory where it is handled under ACL-1 containment measures that are appropriate for wild-type strains in locations where the same species occurs naturally. Due to the lower level of containment measures in the receiving laboratory compared with the shipping laboratory, an accidental escape from the laboratory results.
Similarly to the first case, release of the IGF results in invasion of the wild population. It follows that not only must laboratories working with low-threshold IGFs act appropriately to prevent escapes and introduction into non-IGF strains within the laboratory but also that the strains handled within the insectary must be carefully managed before shipment to other laboratories to ensure that an IGF is not distributed.
These two scenarios illustrate the questions investigators and those charged with ensuring safe handling of arthropods with IGFs can be expected to answer. Can one be certain that a strain being held in a laboratory does not contain an IGF? Can one be certain that those that are known to contain an IGF do not contain more than one type? If non-IGF strains that are being maintained in laboratories that handle IGFs will be distributed or exchanged among other laboratories, can assurance be provided to recipients that the strains do not contain IGFs?
Should the recipient be able to verify this? How stringent does detection need to be? Arthropod containment guidance for compliance with specific standards differs among countries according to institutional, funder, or national regulation and guidance. These are typically shaped by various considerations, including risk assessments, historical experiences, and political and cultural influences.
Some countries have no national guidance and refer to procedures of other countries or nongovernmental organizations such as the ACGs of ACME. To make the considerations presented here applicable broadly, we surveyed several standards for arthropod containment to determine the specific measures they share and those that distinguish them Supplementary Table S1 ; Supplementary Data are available online at www. We also considered whether specific measures that are recommended are needed primarily to contain a pathogen or the arthropod. A survey of several relevant English language containment guidance documents shows that these recommendations are remarkably similar Supplementary Table S1.
There is a remarkable parallel even in the nomenclature across standards presented in each document. Level 2 is not stringent for airborne pathogen containment, whereas level 3 adds measures, including more closely controlled air pressures, sewage disinfection or sterilization, access restriction, air management and filtration including HEPA , and activity isolation. Therefore, we will refer to level 2 and level 3 containment as a reflection of this broad consensus among standards that distinguish those levels. There are, in fact, a limited number of ways to contain arthropods Table 1 , and approaches for doing so are found in most of the guidance documents reviewed.
There are essentially three ways that accidental escape can occur: 1 any living stage, including immatures in solid and liquid waste; 2 transport on equipment or staff; and 3 penetrations of the containment zones, including doors, windows, and ventilation. Escapes by all of these means are avoidable, and preventive measures are the goal of the various standards.
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The same principles apply whether the arthropod is exotic, a potential biocontrol agent, a vector of plant and human diseases, or transgenic. These measures are effective for confining arthropods. As containment stringency increases above level 2, the added layers are generally those measures needed to contain a pathogen in addition to those for the arthropod.
This often results in escalating measures specifically needed to effectively contain a higher risk of particularly airborne pathogens, but which have no clear benefit for containing the arthropod. Figure 1 illustrates the overlap that exists between arthropod and microbiological containment measures as manifested in containment standards. The overlapping measures to contain arthropods and microbes in facilities handling arthropods.
Measures that will contain a microbe will not necessarily contain an arthropod, and vice versa. The arthropod containment measures left overlap with those specific for microbes right. The stringency of measures in the overlapping area depends on whether the facility is level 2 or level 3. In the case of IGFs, the goal is to contain arthropods containing the factor and the use of stringent microbiological methods adds no effect.
IGF, invasive genetic factor. We recommend that in the case of arthropods containing low-threshold IGFs in the absence of any pathogen, any increasingly stringent measures should include those that effectively contain arthropods rather than those that are designed to contain pathogens.
We describe several possibilities for doing so in the next section. All levels of the arthropod containment measures reviewed require good primary containment caging , sealed walls, openings, and doors, usually vestibules or airlocks, surfaces that can be disinfected or disinfested , appropriate personal protection equipment, and controlled access Table 1. Only one of these allows windows that can be opened PC2. All require devitalization of arthropods before disposal although the means differ and some require liquid effluent to be sterilized.
Air curtains were rarely recommended and negative air pressure was consistently emphasized at higher containment levels, although often still recommended as a gradient without specification of the value of the pressures at level 2. While most standards do not explicitly require segregated working spaces, they specify measures such as vestibules and restricted access that would be difficult to achieve unless activities were confined to segregated spaces. Overall, containment guidance documents surveyed described similar requirements with one interesting exception: PC3 requires that provision must be made for viewing of work areas from outside the facility.
The commonalities across these standards demonstrate that methods for containing arthropods are consistent and feasible. The issue of segregation of materials that require different levels of containment is specifically addressed in many standards for level 3 facilities. These specify that lower-level materials in the same facilities must be handled as higher-level materials.
This is an important issue that we will return to below. Of note, IBC approval is required irrespective of whether the modified strain is made locally or made at another institution and imported.bbmpay.veritrans.co.id/funes-dating-gay.php
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BL-1 is a standard established for containment of certain microorganisms. ACL-2 was deliberately specified to be consistent with BL-2 containment. In practice, it is not clear whether the bite of a recombinant DNA-containing arthropod presents the same threat to laboratory workers as infection with a recombinant DNA-containing microorganism. The NIH Guidelines also specify physical containment conditions that represent best practices for laboratory containment Appendix G of the NIH Guidelines , although these practices are written in terms of protecting laboratory workers and the environment from pathogenic microorganisms, and do not make any specific recommendations in terms of requirements for the effective physical containment of arthropods.
However, some useful arthropod containment suggestions can be gleaned from descriptions of physical containment for plants in a greenhouse setting that may supersede the conditions described in Appendix G Appendix P of the NIH Guidelines. Good record keeping of shipments received and made to any facility handling transgenic arthropods is essential.
Ultimately, the NIH guidelines Appendix Q-III-D defer on specific recommendations for nonlaboratory animals such as arthropods, settling for any combination of containment conditions that meets the satisfaction and approval of the local IBC. The features are similar to those prescribed by other guidance documents and are not specifically itemized here. In part, to fill gaps in the practical measures of the NIH Guidelines in the United States, the Arthropod Containment Guidelines were created to recommend containment levels specifically for arthropods Arthropod Containment Levels 1—4.
Institute of Agrobiological Sciences, NARO
These recommend ACL-2 for the containment of transgenic arthropods. Although these guidelines have been used widely in the United States and have been incorporated into several national containment standards, they did not anticipate the unique hazards posed by IGFs. Containment and testing measures for driving transgenes in field cages have been discussed previously Benedict et al. It is important when assessing risks, particularly from hypothetical or speculative hazards generated by what-if scenarios, to keep in perspective the risks presented by the unmodified wild-type comparator.
For vector control strategies, the risks associated with the IGF-containing arthropod need to be balanced against the disease burden that the unmodified arthropod poses even with optimal use of the existing conventional control methods, including insecticides.