Duration of Naturally Acquired Antibody Responses to Blood-StagePlasmodium falciparumIs Age Dependent and Antigen Specific

Abstract

Naturally acquired antibody responses provide partial protection from clinical malaria, and blood-stage parasite vaccines under development aim to prime such responses. To investigate the determinants of antibody response longevity, immunoglobulin G (IgG) antibodies to several blood-stage vaccine candidate antigens in the sera of two cohorts of children of up to 6 years of age during the dry seasons of 2003 and 2004 in The Gambia were examined. The first cohort showed that most antibodies were lost within less than 4 months of the first sampling if a persistent infection was not present, so the study of the second-year cohort involved collecting samples from individuals every 2 weeks over a 3-month period. Antibody responses in the second cohort were also influenced by persistent malaria infection, so analysis focused particularly on children in whom parasites were not detected after the first time point. Antibodies to most antigens declined more slowly in children in the oldest age group (>5 years old) and more rapidly in children in the youngest group (<3 years old). However, antibodies to merozoite surface protein 2 were shorter lived than antibodies to other antigens and were not more persistent in older children. The age-specific and antigen-specific differences were not explained by different IgG subclass response profiles, indicating the probable importance of differential longevities of plasma cell populations rather than antibody molecules. It is likely that young children mostly have short-lived plasma cells and thus experience rapid declines in antibody levels but that older children have longer-lasting antibody responses that depend on long-lived plasma cells.

B-Cell Responses to Pregnancy-Restricted and -Unrestricted Plasmodium falciparum Erythrocyte Membrane Protein 1 Antigens in Ghanaian Women Naturally Exposed to Malaria Parasites

“…The particularly high levels in the positive-control women probably reflect the fact that many had recently received the prophylactic TT booster vaccination that is a standard part of antenatal care in Ghana. These data confirm the usefulness of PfEMP1-specific IgG levels as markers of exposure (49), the existence of interclonally conserved antibody epitopes in PfEMP1 proteins from genotypically distinct P. falciparum parasites (50), and the often transient nature of PfEMP1-specific IgG responses (in the absence of regular reexposure) (5)(6)(7)(8)(9).…”

Force of infection is key to understanding the epidemiology ofPlasmodium falciparummalaria in Papua New Guinean children

“…Infections acquired in the late dry or early rainy season were therefore more likely to lead to clinical illness than those acquired later in the rainy or earlier in the dry season, indicating increasing immunity during the high-transmission season and waning immunity during low transmission. Young children with limited immunity therefore seem to acquire a short-lived protective response during the rainy season, which is supported by findings from a study on the longevity of antibody response to surface antigens that indicated that antibodies decline more rapidly in children <3 y than in older children (30). The latter study, conducted in an area with more pronounced seasonality in The Gambia, also reported seasonal changes in immune status and associated risk of developing clinical malaria.…”

Immunoprofiling of the Tryptophan-Rich Antigen Family in Plasmodium vivax

“…These short-lived antibody responses against P. falciparum MSP1 (PfMSP1), P. falciparum AMA1 (PfAMA1), and the P. falciparum erythrocyte membrane protein 1 (PfEMP1) have been observed in previous studies (29,30), especially in young children (31,32). However, several studies have demonstrated stable antibody responses to PfMSP1-19, P. falciparum merozoite surface protein 2 (PfMSP2), and PfAMA1 antigens (31,33,34).…”