快猫短视频

A VACCINE against the sexually transmitted virus that triggers cervical
cancer has come closer after successful clinical trials.

The human papillomavirus (HPV) contributes to the development of nearly all
cervical cancer. Infections have soared since the sexual revolution of the
1960s. The introduction of smear tests to detect cancers at an early stage has
prevented an epidemic of the disease in rich countries
(快猫短视频, 17 June 2000, p 18),
but effective treatment isn鈥檛 widely available in the rest
of the world. Worldwide, 400,000 women develop cervical cancer each year and
200,000 die.

While factors such as genetics and the environment also play a role in
cervical cancer, researchers believe that changes in cells caused by the virus
trigger over 90 per cent of cases. So doctors are eager to develop an effective
vaccine against the cancer-causing forms of HPV.

Now Douglas Lowy and John Schiller of the National Cancer Institute near
Washington DC and their colleagues have reported the results of the first
clinical trial of such a vaccine. Their vaccine is based on a strain known as
HPV16, whose variants are associated with 50 per cent of cervical tumours and a
700-fold increase in the risk of cervical cancer.

The vaccine consists of a single protein from HPV called L1. 鈥淟1
spontaneously assembles into a hollow 鈥榮occer ball鈥� which looks just like the
real virus,鈥� says Lowy. 鈥淏ut it is completely incapable of causing disease.鈥�

The researchers inoculated 60 volunteers with the vaccine. They found that it
caused few side effects and triggered an antibody response 40 times greater than
that produced by a natural infection. Encouraged by the results, the team has
already launched a larger trial that will follow the volunteers鈥� immune response
for longer. They will also look for antibodies in the vaginal tract, thought to
be important for protecting against viral transmission during sex.

Before the vaccine hits the clinics, however, Lowy and his team want to add
L1 from three other HPV variants that, together with HPV16, are associated with
80 per cent of all cervical cancers. It could be five years before researchers
know whether the vaccine-induced immune response is enough to fight off a
future attack by wild virus.

But Harald zur Hausen, an HPV researcher at the German Cancer Research Center
in Heidelberg, Germany, points out that previous vaccine experiments with dogs,
cattle and rabbits suggest this level of response will be protective in humans.
鈥淭he prospects for this vaccination are remarkably promising,鈥� he says.