It is blamed as a prime cause of cancer and has been responsible for millions of deaths across the globe. But now scientists have discovered how to use tobacco to save lives.

The transformation has been carried out by the Californian biotechnology company, Large Scale Biology Corporation, whose scientists have created tobacco plants that churn out chemicals that protect against leukaemias and lymphomas. 'It is a neat concept,' said project scientist, Dr Ronald Levy, of Stanford University Medical Centre. 'It is the medical equivalent of beating swords into ploughshares, a very satisfactory experience for a doctor.' The corporation says its technique is particularly useful for dealing with leukaemias and lymphomas - which occur when a single white blood cell, a key part of our immune defences, proliferates uncontrollably, and eventually swamps the body. We have millions of different varieties of white cell, each designed to defend the body against a different invading virus or bacteria. There are millions of subtly different forms of leukaemia and lymphoma, each based on the spread of a slightly different type of white blood cell. 'That makes it very difficult to combat such illnesses,' said Levy. 'You cannot use a general approach in fighting them. You need to devise a line of attack designed specifically for each sufferer.' Scientists have had to try to find a way to tackle one form of lymphoma and no other when dealing with an individual patient. And that is where the tobacco plant has provided crucial help. First, scientists have pinpointed the part of a lymphoma-causing white blood cell that distinguishes it from all other white blood cells. Then they have isolated the gene that makes that key component, put it in a tobacco mosaic virus and used the modified virus to infect a tobacco plant. As the virus replicates, it spews out white cell particles, and as the virus takes over the tobacco plant, it becomes coated with these protein pieces. 'Essentially, you create a little bio-factory,' said Levy. 'You have specific pieces of white cell protein on the stalk and leaves. You just scrape them off and collect them.' Scientists have created patches of tobacco plants, each making proteins tailor-made to match a lymphoma from one of 16 different people. For their first trials, they used only sufferers of non-Hodgkin's lymphoma, a relatively common, and potentially deadly condition. 'The crucial point is the speed with which the tobacco plant becomes infected and starts making bits of lymphoma protein,' added Levy. 'You can make a tailor-made, individual bit protein from a person in a few weeks this way. Other methods would take months, or even years - far too long to be effective.' Once the protein fragment from each person is scraped from their individual tobacco plant, it is injected back into that patient. 'Essentially, we use them as a vaccine. Our immune systems often do not recognise a cancer or lymphoma as being foreign and dangerous. But by re-administering pieces of a cancer as a vaccine, it makes the body realise something is amiss. Suddenly, it starts to attack the tumour. We have opened its eyes to the danger within.' Levy and his colleagues have carried out Phase I safety trials on his group of 16 patients and have observed that their bodies mount immune attacks on their lymphomas even having previously ignored the cancer. 'We have a couple of years of trials still to carry out to be sure,' he added. 'Nevertheless, I am hopeful this technique is going to work. You couldn't find a better use for tobacco if you tried.'

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