Study examines malaria natural immunity possibilities

Barcelona Institute for Global Health (ISGlobal) study findings revealed the RTS,S malaria vaccine could bolster protective antibodies production upon subsequent parasite infection.

The work involved the authors investigating how vaccination impacts natural immunity to the parasite upon subsequent exposure.

“To date, most studies had focused on evaluating vaccine-specific responses but not responses towards other parasite antigens,” Gemma Moncunill, the study’s last author, said, noting the RTS,S vaccine contains one single parasitic antigen: a fragment of the CSP protein.

Researchers explained pathogen immunity can be acquired by natural exposure to the microorganism or through vaccination, adding mechanisms underlying both types of immunity are not always the same, particularly in the case of parasites with complex life cycles, such as Plasmodium falciparum, that causes malaria.

“We think that the partial efficacy of the vaccine allows low infection levels upon subsequent parasite exposure which in turn leads to the production of protective antibodies,” Carlota Dobaño, ISGlobal researcher, said. “This effect would be observed especially in regions with low to moderate transmission levels.”

The results identify antigens that could be included in future and more effective multivalent vaccines.

The work determined three patterns of antibody responses to the antigens: those that decrease after vaccination, those that are unchanged and those that increase.

Researchers analyzed serum samples obtained from 195 children, vaccinated or not, who made part of the phase III RTS,S clinical trial and were followed up during 12 months while 78 were from Kintampo, Ghana, a region with high malaria transmission, and 115 were from Manhiça, Mozambique, where transmission is low to moderate.