Wednesday, March 20, 2019

Study advances in design of a more effective vaccine against malaria in children

A scientific study led by the Spanish Institute of Global Health of Barcelona (ISGlobal) identified which antibodies generated the experimental malaria vaccine RTS, S, which until now has a partial efficacy of 31% in babies under 12 weeks and 56% in children between 5 and 17 months.
The work, published today by the magazine "BMC Medicine", was led by the pharmacist and biologist Carlota Dobaño and sheds new information on the protection mechanisms of the RTS, S, which provides a basis for designing more effective future vaccines.
Dobaño explained to Efe that the study wanted to know why this vaccine protects some children and not others, and has concluded that the protection conferred by the RTS, S malaria vaccine depends to a large extent on the level and subclass of antibodies generated by the same, as well as previous exposure to the parasite.
The ISGlobal researcher and her group have been working for several years to understand why this variability takes place and to identify markers of vaccine protection, which, as Dobaño has announced, the World Health Organization (WHO) will test scale in three African countries next year before authorizing their distribution.
In this study, the international team led by Dobaño investigated not only the levels, but also the types of antibodies induced by the vaccine, which it considers the most advanced and the only one that has yet given protection, albeit partial, against malaria, thanks to a quantitative test developed by your group.
In particular, they measured various subtypes of antibodies directed against different fragments of the CSP protein of the parasite and against the surface antigen of the hepatitis B virus (HBsAg), the two proteins that make up the RTS, S vaccine.
They used serum and plasma from almost 200 babies and children from Kintampo (Ghana), an area with high malaria transmission, and from Manhiça (Mozambique), with low malaria transmission, vaccinated in the framework of the phase 3 clinical trial of the RTS, S.
The results have confirmed that the vaccine induces considerable levels of IgG antibodies against both proteins (CSP and HBsAg), and that they are higher in girls and boys than in babies.
The results also indicate that girls and boys with higher levels of anti-CSP antibodies before vaccination were less protected from the disease after the vaccine.
"This indicates that the vaccine will benefit more babies who have not been exposed to the parasite during pregnancy or in the first weeks of life," summarized Dobaño.
"This study, the result of many years of work by many people, identifies new markers of success or failure of the vaccine in African children, and lays the basis for the design of future more effective vaccines," concluded the Spanish researcher.
According to the WHO, in 2016 some 216 million cases of malaria were detected in a total of 91 countries, representing an increase of five million with respect to 2015.

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