Researchers have found that a new mixture of AMA1 proteins -- needed by the malaria parasite to invade blood cells - is a cocktail that can actually overcome major limitations of an earlier designed version of AMA1-based vaccines, raising hopes of finding a safe and effective vaccine.
To explore the potential for a more broadly protective vaccine, the researchers tested different cocktails of AMA1 from different parasite strains for their ability to elicit a diverse range of antibodies, according to a study led by Indian-American scientist Sheetij Dutta of the Walter Reed Army Institute of Research (WRAIR) in the US.
The team confirmed that a cocktail of AMA1 proteins from three different parasite strains was better than one or two. And the one that contained AMA1 proteins derived from four different strains -- they call it Quadvax -- led to a broader antibody response, said the study, published in the journal PLOS Pathogens.
In various lab tests, Quadvax-induced antibodies inhibited the growth of 26 different parasite strains, and the scientists suggested that "the combination of four AMA1 variants in Quadvax may be sufficient to overcome global AMA1 diversity".
"We had set out to study broadening of antibody responses achieved by mixing AMA1 proteins and were surprised and delighted to find not only greater variety of strain-specific antibodies but also increased antibodies against conserved epitopes were induced by the Quadvax," the researchers concluded.
"Most importantly, our data strongly supports continued efforts to develop a blood stage vaccine against malaria."
The next steps will be to test human-use formulations of Quadvax in primate models and in a human blood-stage challenge model.
The challenge with the malaria parasite in general and its AMA1 surface protein in particular is that both exist as multiple strains.
Using AMA1 in a vaccine readies the human immune system for subsequent encounters with the parasite. But when such a vaccine was previously tested in humans, it was effective mostly against one particular P. falciparum strain, the study noted.
There is no effective vaccine to counter malaria that claims millions of lives across the globe every year, mainly in the tropical and sub-tropical regions in sub-Saharan Africa, Asia and the Americas.
--IANS (Posted on 27-12-2013)