A protein called PD-L2 could help stimulate a person's own
immune system to fight malaria (Credit:
J J Harrison/CC SA 3.0)
Of the serious diseases transmitted by the mosquito,
malaria is one of the most common and dangerous, killing
hundreds of thousands of people each year. Now, scientists
have developed a synthetic protein which not only completely
cures malaria in mice, but also prevents the disease from
recurring down the track.
According to the
World Health Organization (WHO), malaria was responsible
for an estimated 438,000 deaths last year. Initially,
symptoms seem flu-like, including nausea, fever, headaches
and sore joints and muscles, but things get worse if left
untreated, and could eventually end in death.
"There are drugs available that treat malaria, but
emerging drug-resistance is becoming an increasing problem,
especially in parts of South-East Asia," said Dr. Michelle
Wykes, head of the Molecular Immunology laboratory at QIMR
Berghofer Medical Research Institute in Australia. "Vaccines
that are being trialed generally only protect against some
species of malaria parasite, and they don't protect people
in the long-term. This means that we urgently need new
treatments."
Research conducted at the Institute may have uncovered a
new solution. A certain protein helps the immune system
fight off infection, but advanced malaria tends to suppress
that protein. Realizing this, the team synthesized their own
version of it.
"Within the immune system, there are dendritic cells,
which are the generals of the immune army, and there are T
cells, which are the soldiers," Wykes explained. "The
dendritic cells tell the T cells when to attack an infection
and when to put down their weapons."
For that job, the dendritic cells use proteins on their
surface, including one that instructs the T cells to switch
off. But another, called PD-L2, is able to override those
instructions, ordering the T cells to keep fighting the good
fight.
"We found that when humans and mice are infected with
severe malaria, levels of PD-L2 decrease and so the T cells
aren't being told to keep fighting the parasites," said
Wykes. "We don't know how malaria manages to block the
production of PD-L2. But once we knew how important this
protein was for fighting the disease, we developed a
synthetic version of it in the laboratory."
To test it out, the researchers infected mice with a
lethal dose of malaria, before administering three doses of
their synthetic protein. All of them were cured. In
addition, when the same mice were reinfected with the
parasites five months later, the infection couldn't take
hold so a further dose of the synthetic protein wasn't
necessary.
"This would be a completely new way of treating malaria
by stimulating a person's own immune system to destroy the
parasites," Wykes said.
The research was published in the journal
Immunity.
Source:
QIMR Berghofer