杏吧原创

CELLS infected with scrapie have been 鈥渃ured鈥� using antibodies. Although the
treatment has so far only been tried on cells grown in the lab, it provides a
glimmer of hope that there may one day be a way to treat people with vCJD, the
human equivalent of scrapie and mad cow disease. So far, 100 people have died of
vCJD, and epidemiologists have warned that thousands more could yet succumb.

Charles Weissmann and his colleagues in the British Medical Research
Council鈥檚 Prion Unit at St Mary鈥檚 Hospital, London, grew mouse cells in the lab
then infected them with a form of mouse scrapie that mimics vCJD in humans.

The infected cells started to produce prions, malformed versions of a normal
surface protein. It is this prion, called PrP^Sc, that clogs up and destroys the
brains of people with vCJD, as it does in sheep with scrapie and cows with
BSE.

But when Weissmann exposed the infected mouse cells to an antibody that
blocks the normal protein, PrP^C, they stopped producing the prions and remained
healthy for the rest of the six-week experiment. What鈥檚 more, all the prions
that had accumulated disappeared. This was unexpected, and suggests that
abnormal proteins can be cleared from the infected brains.

鈥淭he interesting point is that PrP^Sc infection is reversible,鈥� says
Weissmann. 鈥淵ou not only abolish production of the prion, you also diminish the
level.鈥� He says that contrary to what people thought, the prion is not
particularly stable. 鈥淚t turns out that it is destructible,鈥� he says.

By using an antibody that blocks the normal PrP^C protein from which prions
are derived, the team confirmed that PrP^C is crucial to the infection of cells
and producing rogue prions. And when they exposed the cells to an enzyme that
stripped them of all their surface proteins, including PrP^C, they didn鈥檛
produce any prions either. 鈥淭he level of PrP^Sc is determined by the rates of
its formation from PrP^C,鈥� say the researchers.

Weissmann warns that a treatment remains a distant prospect. 鈥淭he next step
is to try it in mice,鈥� he says. And to treat humans you鈥檇 need an antibody that
binds to human PrP^C. You鈥檇 also need a way of getting antibodies into the
brain, which would not be easy. 鈥淭hat鈥檚 why you must be cautious,鈥� he says.