'GE Solution' Threatens More Than Just Possums
A project aimed at destroying possums is cause for serious concern and could put other mammals in New Zealand at risk.
The experiments involve an antigen to the zona pellucida that has been created and turned into a contraceptive spray that could save New Zealand millions of dollars a year. But the experiment could also impact the reproduction capacity of other mammal populations.
"These experiments could be much worse than just being a 'dead end", says Claire Bleakley from GE Free NZ in food and environment. “The possum experiments could become a threat to other mammals through horizontal gene transfer(HGT), just as possums have been through transfer of TB."
On 28 January 2001 Genetically modified (GM) carrots and potatoes were imported into NZ. These vegetables contain a transgene made from a zona pellucida (ZP) antigen and a LT-B protein to enhance the absorption of the antigen.
All mammal eggs have a ZP jelly specific and essential to each species, this planned form of possum control- if allowed to become common place- could threaten other species as a result of horizontal gene transfer.
When sprayed into the eyes and nose the antigen crosses into the blood stream and circulates around the body. As it is a foreign protein an auto-immune response produces antibodies to ZP. These antibodies then go on to attack the undeveloped egg in the follicles of the ovary.
ZP could cause long term sterility to other female populations of animals both marsupial, bird, bovine, ovine and human though Horizontal Gene Transfer (HGT).
Research has found that human ZP (hZP) is 85% similar to possum and pig ZP (pZP). Researcher, Koyama (1996) injected pZP into hamsters causing permanent infertility followed by degenerative changes in the ovaries. In monkeys there was also ovarian impairment with pre-cancerous cells.
The zona pellucida (pZP3) is a jelly that every mammalian female egg cell has enclosing it. It is a compound of three glycoproteins that acts in a number of ways; It is an attractant to the sperm, helping binding to the egg and once the egg is fertilised serves as a repellent to other sperm. It also acts to protect the egg from chromosomal damage and to promote fertility.
Could the possum experiments become a risk to other mammals through HGT?
It is widely acknowledged that possums are major carriers of TB. They transfer the toxin to the soil through their fecal waste and dead bodies. Cows dogs and other animals can pick up the disease if they contact the waste.
There is a possibility that possums could transfer the ZP antigen through their faeces into the soil in this manner. Research studies have found that, "Humans and mice fed on potato expressing the sLT-B protein produced antibodies against LT-B in their serum and gut secretions" (Mason et al. 1998; Tacket et al. 1998).
“ ERMA must not allow these experiments into the field. There are safer ways kill possums and create an industry from them” says Ms Bleakley. "The risk to the New Zealand environment and economy through poor science with no insight to the precautionary principle could push our agriculture to the brink of a disaster".
Skinner,SM,:Mills,T.:Kirchick, H.J; Dunbar, B.S.; (1984) Immunisation with zona pellucida proteins results in abnormal ovarian follicular differentiation and inhibition of gonadotrophin-induced steroid secretion. Dept Cell Biol; Baylor Coll. Med., Houston, TX, USA.
Rankin Tracy; Talbot, Prue; Lee, Eric; Dean, Jurrien.(1999) Abnormal zonae pellucidae in mice lacking ZP1 result in early embryonic loss. Laboratory of Cellular and Development Biology, NIDDK, National Institutes of Health, Bethesda, MD, USA.
Cai,L; Li, D; Sun, X; Wang, M. (2000). Mechanism of prmature ovarian failure in murine autoimmune oophoritis immunised by porcine zona pellucida.Institute of Obstetrics and Gynecology, Shanghai Medical University, Shanghai, People Rebublic of China.
Abington Reproductive Medicine.(2000) Association of antizona pellucida antibodies in human premature ovarian failure and infertility. www.abington-repromed.com
Koyama, K.,Hasegawa, A.,& Isojima, S.(1994) Porcine zona pellucida antigen 4(ZP-4) as a candidate for vaccine. Department of Obstetrics and Gynecology, Hyogo Medical College, Hyogo, Japan.Eds.
Talwar, G.P.; Rao, Kanury V.S.; Chauhan V.S. Recomb. Synth. Vaccines.
Application Executive Summary: GMC00020
Landcare Research propose to research the biological control of the possum by evaluating the immunogenicity and effects on fertility of transgenic plant material expressing foreign proteins by; feeding possums with transgenic carrots expressing either (i) sLT-B or (ii) possum zona pellucida protein 3 (ZP3). feeding possums with transgenic potatoes expressing a 27 amino acid peptide from possum zona pellucida protein 3, joined to sLT-B by an 7 amino acid linker at the N terminal end (ZP3 pep-LT-B). measuring serum and mucosal immune responses of possums to ZP3, ZP3-peptide, and LT-B. for promising constructs, measuring the effects of immunisation on the fertility of possums by superovulation and artificial insemination, and/or natural outdoor breeding trials.
Spray doom to possums NZ HERALD 21.10.2004 By SIMON COLLINS.