According to the study malaria vaccine could enhance; the production of protective antibodies upon subsequent parasite infection. By identifying the antigens (or protein fragments); that could be including in the future, more effective multivalent vaccines. Immunity to a pathogen can be acquiring by natural exposure to the microorganism or through vaccination.
The 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. The study investigating the immune response induced by the RTS,S, the most advanced malaria vaccine that will be tested at large scale in sub-Saharan Africa this year.
In this study, the authors investigated how vaccination affects 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; explaining Gemma Moncunill; last author of the study. The RTS,S vaccine contains one single parasitic antigen, a fragment of the CSP protein.
Production of protective antibodies
Malaria is a life-threatening disease. It is typically transmitting through the bite of an infecting Anopheles mosquito. Infecting mosquitoes carry the Plasmodium parasite. When this mosquito bites you, the parasite is releasing into your bloodstream. Once the parasites are inside your body, they travel to the liver, where they mature.
The research team analysed 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. They studying the levels and type of antibodies recognising a total of 38 P. falciparum antigens, including the CSP protein, before and after vaccination.
Patterns of antibody responses
They study finding that the three patterns of antibody responses to these antigens; those that decrease after vaccination, those that are unchanging, and those that increase. Many antibodies in the first group are considering markers of parasite exposure and were associating with a higher malaria risk. Those in the third group were associating with protection they reducing by half the risk of developing the disease.
However, these protective antibodies mostly recognised antigens expressed by parasite stages that circulate in the blood and that infect red blood cells. the partial efficacy of the vaccine allows low infection levels upon subsequent parasite exposure which in turn leads to the production of protective antibodies; This effect would be observed especially in regions with low to moderate transmission levels; she adds. But importantly, these results identify antigens that could be included; in future and more effective multivalent vaccines.