Antibody Responses to Several Malaria Pre-Erythrocytic Antigens as a Marker of Malaria Exposure Among Travelers

Abstract

Protective devices against vectors are used by travelers in malaria-endemic areas but their efficacy for protection against mosquitoes has rarely been evaluated. The level of exposure to malaria transmission of 205 soldiers deployed in Africa and the efficacy of their anti-vector prophylaxis was evaluated by comparison of their IgM and IgG responses against five pre-erythrocytic Plasmodium falciparum antigens (circumsporozoite protein, sporozoite threonine- and asparagine-rich protein, sporozoite- and liver-stage antigen, liver stage antigen 1, and SR11.1) before and at the end of their deployment, and three months after returning to France for 106 of these soldiers. The immune responses increased significantly during the mission in 35% (95% confidence interval = 28-42%) of the individuals. The permanent use of insecticide-treated bed nets and long-sleeve battle dress at night were associated with protective efficacy. The analysis of these antibody responses was sensitive enough to evaluate exposure to malaria transmission and the efficacy of anti-vector devices in travelers using antimalarial chemoprophylaxis.

High Levels of Antibodies to Plasmodium falciparum Liver Stage Antigen-1 in Naturally Infected Individuals in Myanmar

“…In the present study, high levels (70.7%) of antibody responses against PfLSA-1 were evoked in naturally infected individuals in Myanmar. This finding was consistent with the results of previous studies showing that a significant level of antibodies against PfLSA-1 can be detected in exposed or infected individuals with P. falciparum [10,13]. We also determined that IgG responses to PfLSA-1 were principally composed with responses of IgG1 and IgG3 subclasses.…”

“…High levels of antibody responses against a variety of exoerythrocytic stage proteins, including circumsporozoite protein (CSP), liver stage antigens (LSA-1 and LSA-3), and thrombospondin-related adhesive protein (TRAP) of P. falciparum in infected individuals have been identified and characterized [9][10][11]. Careful analysis of the antibody responses in malaria-infected individuals is crucial not only for our understanding of immune responses against the infection but also for the design of a vaccine or serodiagnostic method for malaria.…”

A Peptide-BasedPlasmodium falciparumCircumsporozoite Assay To Test for Serum Antibody Responses to Pre-Erythrocyte Malaria Vaccines

“…Indeed, we have shown highly reproducible results between two different laboratories. Since the first report of using NANP repeat peptides as CS antigen (23), various versions ranging from 3 to 40 repeats have been used, mainly as a diagnostic antibody ELISA for epidemiological studies (2,(9)(10)(11)15). A thorough comparison of the peptide antigen with protein antigens and whole parasite as antigen (immunofluorescence assay) has been performed by Del Giudice et al (4).…”

Malaria

“…The test antigens were circumsporozoite protein, sporozoite threonine-and asparagine-rich protein, sporozoite and liver stage antigen, liver stage antigen 1 and SR11.1. The immune response was measured in 106 individuals 3 months after exposure and seemed plausible [35]. If leucin-rich protein is used, cross-reactions occur between Schistosoma mansoni and P. falciparum [36].…”