Mike's Opinions

The Lancet GM food debate

nga.gif - 12Kb
A structure of the snowdrop lectin 'NGA'

In The Lancet, Dissecting Room, Websites in brief vol 354 page 1395 (1999) my web site receives a mention and to quote a small section

But what distinguishes Mike Clark's site and what saves it from having a "textbook" feel, is his ability to mingle his personal information, interests, opinions and creativity with the highly detailed molecular material.

So here are some opinions on the GM food debate prompted by two papers and an editorial in the very same issue of The Lancet.

Firstly I must say that I obviously am not against Genetic Modification as a technology. My own work on developing therapeutic applications of recombinant antibodies relies heavily on this technology. However neither am I advocating that all uses of genetic modification should be approved or introduced without careful consideration. Regarding GM foods I think that there are good reasons to be cautious concerning issues such as effects on ecosystems and agricultural economics in addition to any concerns over human health consequences. However these are issues to be considered for each individual case and not as a blanket pronouncement on the whole technology.

Dr Richard Horton, Editor of The Lancet has chosen to enter the debate by publishing two articles on the potential toxic effects of the snowdrop lectin or Galanthus nivalis agglutinin (GNA) to rats and to humans. Below is a copy of a message which I sent to The Lancet in response to the published articles.

Comments relayed to The Lancet in November 1999

I have followed the debate over the Lancet's publication of the paper by Stanley W. B. Ewen and Arpad Pusztai with some interest. I am to some extent prepared to accept Richard Horton's arguments that putting the paper into the public domain alongside a critical editorial does allow the debate to continue in a more informed manner even though many journalists and commentators seem to ignore the presence of the editorial.

However what I find most extraordinary is the inclusion of a second paper in the same issue entitled 'Differential binding of the insecticidal lectin GNA to human blood cells by Fenton et al Vol 354 1354-1355 (1999). This paper seems to be totally out of character with the usual style of paper published in the Lancet and I wonder what kind of peer review process and editorial selection this paper went through? The paper shows a single western blot in which commercially purchased snowdrop lectin (GNA) was used to stain glycoproteins derived from human lymphocytes. There is no indication of what these stained bands might be and also no other evidence provided as to possible biological consequences of the binding of the lectin to intact lymphocytes. The paper concludes with the statement 'This work highlights the need for a much greater understanding of the interactions between plant lectins and human glycoproteins before they can be safely incorporated into the food chain'.

I would question whether there is any detail of merit in this paper to justify it's inclusion in a major journal such as The Lancet. I wonder if in reviewing this paper The Lancet Editors took account of previously published work on snowdrop lectin and whether the referees chosen were experienced either in the biochemical applications of lectins or more particularly in the use of snowdrop lectin? I did a Medline search on the subject of 'snowdrop lectin' and came up with several interesting and substantial publications on this lectin in peer-reviewed journals. Selecting from some of these I found that it was known that this lectin binds to human alpha 2-macroglobulin [1] and more interestingly that it recognises envelope glycoproteins of retroviruses such as HIV and SIV [2]. Indeed it has even been investigated whether the Lectin can have beneficial effects in reducing viral infectivity [3]. Another paper suggested that the use of GNA in the diets of rats could protect them from the harmful effects of kidney bean lectin induced pathology [4]. Interestingly two of the coauthors on this paper showing the beneficial effects of GNA in diets of rats are Pusztai and Ewen!

Returning to my main point, there is a substantial scientific literature on snowdrop lectin, which includes far more useful data than is revealed in The Lancet paper by Fenton et al (1999), so why did The Lancet editors and their referees choose to accept this paper rather than simply pointing to the better scientific information already in the literature? I am led to believe that the editors allowed their better judgement in this case to be overruled by the controversy surrounding the accompanying paper by Ewen and Pusztai and to thus accept a paper with a scientific content well below what they would normally require.

Finally on another issue referring again to the closing paragraph of the paper by Fenton et al (1999). When I started out as a PhD student in 1978 it was commonplace for scientists to go down to the local shop and to purchase common foodstuffs such as kidney beans, peas and lentils. The purpose was to extract the lectins from these foods for use in laboratory experiments. Perhaps now that many scientists purchase these purified reagents direct from chemical companies we have forgotten where they originate from? May I suggest, tongue firmly in cheek, that The Lancet calls for a halt in the use of kidney beans and lentils in human diets until we can more fully investigate the interactions of their lectins with human glycoproteins?

Mike Clark, PhD, Lecturer in Therapeutic and Molecular Immunology, Cambridge University

Snowdrop lectin structure 1NIV.pdb

The image above shows the structure of the mannose-specific agglutinin (or lectin) [two chains shown in blue and in green] from snowdrop ( galanthus nivalis) in a complex with mannose-alpha 1,3-methyl-D-mannose [in red] prepared from the PDB file 1NIV.PDB available in the Protein Data Bank

This page is from   Mike Clark
"An antibody engineer who also enjoys the mountains."
mrc7@cam.ac.uk
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© Mike Clark, PhD., Cambridge University, UK
Last updated on 6th November 1999