Published in 'New Scientist' 2008.
Disease-causing bugs could play a valuable role in the treatment of cancer. Deliberately infecting people with the bacteria that cause listeriosis could increase their ability to destroy tumours. The goal is to kick-start the body's immune system by "provoking" it with the bacteria, which are modified to trigger an attack on the cancer.
US vaccine company Advaxis chose Listeria monocytogenes because of its ability to stow away in immune cells called antigen-presenting cells (APCs). These cells prime the rest of the immune system to attack a given strain of microbe, say, by showing fragments of antigen from that microbe to the appropriate cells.
Advaxis modified the bacterium so it was no longer harmful, and so that once inside the APC it would secrete fragments of HPV-E7, a molecule found on the surface of cervical cancer cells. By presenting HPV-E7 to other immune cells, the APCs would then prime them to attack the cancer.
In a preliminary trial on 13 women with advanced cervical cancer, four of those injected with the bacteria responded. One is tumour-free more than two years after the treatment, and tumours in the other three shrank by 20 per cent. Seven of the women have died from the cancer. Advaxis hopes to begin a trial on 180 patients with less advanced cervical cancer.
John Stanford of University College London, whose team has had recent success treating cancer patients with dead Mycobacterium vaccae, says that Advaxis may need to give booster doses to sustain the therapeutic effect.
