The immune response to malaria develops with repeated exposure. Susceptibility to symptomatic malaria decreases with age and is associated with the acquisition of antimalarial antibodies, and adults in endemic areas generally possess immunity to symptomatic malaria. Pregnant women are the exception and experience higher rates of malaria infection, which impacts upon maternal and newborn health. This increased susceptibility to malaria is thought to be partially due to the expression of chondroitin sulphate A (CSA) and other pregnancy-specific ligands on the placenta, enabling interactions with P. falciparum-infected erythrocytes expressing the adhesion protein VAR2CSA, a variant of the P. falciparum erythrocyte membrane protein 1 (PfEMP1). These interactions facilitate sequestration of parasites in the placenta.
Antibodies to VAR2CSA are thought to protect pregnant women from malaria, but the generation and maintenance of immunity to malaria in pregnant women is poorly understood. Previous studies have suggested that the antibody response to recombinant VAR2CSA in pregnant women may be extremely long-lived compared to the antibody response against merozoite antigens. It is unclear whether the longevity of this response is specific to VAR2CSA, or whether antibodies to antigens on the surface of parasitized red blood cells (pRBCs) are better maintained than antibodies to merozoite antigens. This study therefore aimed to measure antibody levels against and determine the longevity of the antibody response to different variants of PfEMP1 during pregnancy.
This study examined a cohort of women from the Thai-Burma border. In order to assess the longevity of antibody responses, serum samples have been taken from each individual at repeated timepoints from enrolment to delivery. Serum samples were tested for antibodies to pRBC surface antigens using placental- and CD36-binding parasite isolates. Preliminary results suggest that antibody levels against pRBC antigens do not decline rapidly and are maintained throughout pregnancy. The findings of this study may help to generate a better understanding of the generation and maintenance of antimalarial immunity in pregnant women.