Researchers find potential vehicle for childhood malaria vaccine
Researchers have discovered a protein with the potential to be used as a basis for a vaccine against severe childhood malaria. They compared proteins expressed by two types of the malaria parasite Plasmodium
falciparum, one of which causes severe childhood disease in non-immune sufferers and the other less severe adult infection.
The researchers, from five centres in Europe and Tanzania, identified
an antigen expressed on the surface of red blood cells during severe
childhood malaria but not in adult infections. The protein appears to
confer a selective advantage on parasites in non-immune individuals.
It may prevent infected red blood cells being removed by the spleen by
allowing them to stick inside blood vessels. It may also allow high growth
rates of the parasite in non-immune individuals.
As immunity to this antigen subset — VSASM — is acquired,
the advantages to the parasite diminish and its survival rates decline.
The authors say that this scenario makes it theoretically possible to
protect non-immune children against severe and complicated disease by
accelerating the acquisition of VSASM-specific immunity through vaccination.
The researchers have identified the genes that confer the VSASM phenotype
associated with severe and life-threatening disease. A group of highly
transcribed genes on this phenotype is translated into a protein that
can be detected on the surface of infected red blood cells carrying the
VSASM phenotype.
The study also showed that, unlike similar proteins studied previously,
this protein does not vary between malaria parasites from East and West
Africa, making it an ideal candidate for a universal vaccine to boost
immunity in young children (Journal of Experimental Medicine 2004;199:1179). |
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