The Virus Hazard
by Jaan Suurküla, MD
Summary
Viruses are packages of hereditary material, DNA or RNA. They can get into the cells and take over the command over the cells activities and make it produce new copies of viruses. This commonly kills the infected cells. Dangerous viruses have a great ability to penetrate into cells and to spread and multiply so that extensive damage is caused. While many viruses are species-specific, some viruses may cross species borders.
Practically all genetically engineered crops contain genetic material from viruses. Research has shown that these virus genes may combine with genes from infecting viruses. The serious thing is that experimental evidence indicates the new viruses created in this way may be more infectious, may cause more serious diseases, and may have a tendency to cross species borders.
There is not enough knowledge to assess the risk for the emergence of new virus diseases from genetically engineered crops.
There is no scientific basis for excluding the possiblility that the risk for creation of dangerous viruses in GE crops (and related weeds) is large enough to represent a significant threat when large numbers of crop plants are cultivated.
Introduction
A virus can be described as a package of hereditary material, DNA of RNA encapsulated by a protein coating. This coating has special properties that makes it stick on to cell walls. When attached, the virus DNA or RNA is transferred into the cell. Viral DNA and RNA has an ability to force the invaded cell to switch over from normal activity to producing large numbers of copies of the whole virus. The infected cell is commonly killed due to the infection, and if the number of infected cells is large enough, the whole organism will die. Some viruses may insert its DNA or RNA into a chromosome and remain silent for a long time (it is this kind of virus that are used in genetic engineering)
Virus genes are used very widely in genetic engineering. Experiments have shown that the artificial insertion of virus genes through genetic engineering make them prone to combine with genes from infecting viruses (so called recombination)
It is notable that even the largest biotech company does not deny the possibility that new viruses may be generated. For example, Roy Fuchs, Monsanto's director of regulatory science acknowledged that "some of the virus can recombine" in an article by Stan Grossfeld in The Boston Globe (09/23/98), published on line , Roy Fuchs, Monsanto's director of regulatory science acknowledged that "some of the virus can recombine."
Cauliflower Mosaic Virus (CaMV)
The most common virus DNA used in genetic engineering is the promoter of the Cauliflower Mosaic Virus (CaMV) used in plant genetic engineering. It is used in almost every case, including the presently most culitvated GE crops, the RoundupReady (RR) Soy of Monsanto, the Bt-Maize of Novartis, GE cotton and various varieties of GE Canola, a rapeseed variety widely cultivated today especially in Canada. Experiments have shown that the CaMV promoter may recombine with infecting genes yielding new viruses that may be more infectious than the natural viruses. For more details, see also "The Cauliflower Mosaic Virus promoter - a hazard in GE plants")
Recent research confirms these findings and indicates that the risks for combination with unrelated viruses is even greater than formerly understood. Studies have demonstrated that CAMV has a so called "recombination hotspot" which makes it prone to break up other DNA chains and join them at that point.
Mae-Wan Ho, biologist, Angela Ryan molecular biologist and Joseph Cummins, geneticist, have recently published a paper warning for the use of CaMV in crops.
This virus gene, they write, has the potential to reactivate dormant viruses or create new viruses in all species to which it is transferred. The development of cancer is another potential consequence.
The scientists "strongly recommend that all transgenic crops containing CaMV 35S or similar promoters should be immediately withdrawn from commercial production or open field trials. All products derived from such crops containing transgenic DNA should also be immediately withdrawn from sale and from use for human consumption or animal feed". Full text press release here. [ML] Full text here. [AL]
Also the US Department of Agriculture has expressed concern about such high-risk sequences that may trigger the process of viral replication"
Concerns at USDA about viral high-risk sequences
"..... At a meeting in Washington DC last week [Aug 1997], the US Department of Agriculture outlined possible restrictions aimed at reducing the risk of creating harmful new plant viruses .....These include a possible limit on the length of genetic sequences introduced into crop plants and the banning of genes that make functional proteins. The department is also worried about particularly high-risk sequences, such as those that trigger the process of viral replication.
[The CaMV DNA in GE crops is such a high risk sequence. It is still widely used in GE crops covering a large part of American fields. /The editor.]
[The suggested restrictions have not since been implemented to the best of our knowledge. /The editor]
Source: New Scientist magazine, 16 August 1997: "Field of genes: They have the biotechnology, but it may be running out of control, and the US is starting to worry"
Virus genes used for increasing disease resistance
Another possibly dangerous practice is the use of virus parts to make plants resistant to infecting viruses. Certain virus genes, coding for the virus protein capsule , are used for this purpose. These so called "capside genes" are combined with the CaMV promoter to ensure that they will be active in the host. Also the capsied genes have a propensity to recombine with invading viruses to create new pathogens that tend to be more aggressive than the original virus.
New viral pathogens could have an enormous impact on economically important crops, requiring considerable control costs. Source: Rissler, J. and M. Mellon. 1996. The Ecological Risks of Engineered Crops. Cambridge, MA: MIT Press.
Sattelite RNA's
Another method to achieve increased virus resistance has been to insert so called viral "satellite RNA's". These genes are known to reduce the damage from a virus infection. But recent research found that such genes, when inserted into cucumbers, very often mutated into harmful variants (ref. Paulikaits P. And Rossinck MJ (1996). "Spontaneus change of a benign satellite RNA of cucumber mosaic virus to a pathogenic variant. Nature Biotechnology 14: 1264-1268).
Epidemics of new viruses might appear
Dr Joe Cummins, Professor Emeritus of Genetics at University of Western Ontario, Canada fears that the insertion of viruses may give rise to new plant disorders that may wipe out whole harvests. One plant only contains hundreds of millions of cells, each containing a CaMV virus gene. Anyone of these genes may combine with an infecting virus, generating a new virus.
It is not possible to estimate the size of the risk for the appearance of new virus diseases from genetically engineered virus parts in crops beacuse there is not enough research data available. Some researchers believe the risk is very small and others believe it is large enough to justify a prohibition of the use of virus parts in genetic engineering. But in the absence of sufficient research data, this is nothing but guesses. Considering the experimental evidence we can only say today that there is definitely a risk but of unknown size.
The serious thing is that it has been repeatedly shown experimentally that the new viruses may be more contagious and damaging and may also cross species borders. So viruses specialized on just one plant species might become infectious to other species. It is enough that one very malignant virus appears in only one cell for a new dangerous virus epidemic to appear.
Risk for harmful "GE viruses" spreading in USA and Canada?
About 30 percent (27 million acres) of the crop in USA of 1998 is calculated to be RR Soy. Also a large crop of GE Maize has been planted (19,6 million acres). In Canada, large crops of Canola are cultivated (about 7 million acres). Every cell in the present GE crops in USA and Canada contains virus genes. One plant only contains hundreds of millions of cells. The number of plants in the GE crops in North America is altogether thousands of billions.
Even if the scientists would be right who guess that the statistical risk is very small, the appearance of new hazardous viruses might be more likely than they may have realized. This is because they may have forgotten to consider the enormous large numbers of possible recombination events in one annual crop in USA + Canada. A corn plant, for example, contains about 1 billion cells and there is one CaMV promoter in each cell. There are about 50.000 plants in an average field, which means 50.000 billion recombination prone promoters per field. The gigantic acreage of of US GE crops therefore can be seen as a huge "experimental ground" for generation of new viruses with unpredictable and potentially hazardous outcomes. Even if the probability of a new dangerous virus to be generated would be extremely small, such an event may still occur due to the very large number of recombination opportunities present. Here is an analogy for you who are not so used to thinking in these terms:
Suppose there is a lottery with a million tickets. Then the chance of winning with one ticket is one on a million. But if you buy all the tickets, your chance will transform to 100% probability of winning. Every cell in the huge GE crop in North America is a "ticket" in the virus lottery. And there are zillions of cell "tickets" in the crop. Therefore, even if the chance for "winning" - for a new virus to turn up - would be extremely small, it may be likely to occur. Scientific laboratory experiments indicate that this probability may not be very small.
Even a single new very contagious virus strain might cause important damage, as it would rapidly multiply and might spread to a significant part of the crop. As it has been shown that GE-genes can readily be transferred to related weeds, these will become an uncontrollable reservoir of such virus genes even when cultivation of GE crops would cease. A highly contagious virus with low species specificity could in the worst case cause extensive damage to the crops and the ecology.
Conclusion
It has been scientifically established that new viruses may result from recombination with virus parts existing in GE organisms. Some studies indicate that these new viruses may become more harmful and less species specific that "natural" viruses. The size of this risk is unknown. Even if the statistical risk for the emergence of dangerous new viruses would be very small, they may still appear in North America as the number of GE virus genes in the crops is now extremely large.
One single new and highly contagious virus generated in this way might spread to a signficant part of the crops and cause extensive damage. There is presently no scientific basis for denying this possibility or even for saying that it is very unlikely as the size of the risk has not been investigated.
This is one of the reasons why we find it necessary to have a moratorium on the release of genetically engineered organisms. In addition, all presently cultivated GE crops should be withdrawn from the market.
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