Antibodies by Non-Febrile, Smear-Negative Individuals from a Malaria Epidemic-Prone Setting in Ethiopia are Strongly Reactive to Plasmodium falciparum Blood-Stage Vaccine Candidate Antigens
- *Corresponding Author:
- Hassen Mamo
Microbial, Department of Molecular Biosciences
The Wenner-Gren Institute
Department of Immunology
Stockholm University, Sweden
E-mail: [email protected]
Received date: July 24, 2013; Accepted date: August 27, 2013; Published date: August 20, 2013
Citation: Mamo H, Iriemenam NC, Berzins K, Petros B (2013) Antibodies by Non-Febrile, Smear-Negative Individuals from a Malaria Epidemic-Prone Setting in Ethiopia are Strongly Reactive to Plasmodium falciparum Blood-Stage Vaccine Candidate Antigens. J Vaccines Vaccin 4:200. doi: 10.4172/2157-7560.1000200
Copyright: © 2013 Mamo H, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Background: Plasmodium falciparum malaria remains a major public health concern globally though there is some decline due to scale-up of control efforts. Evaluation of the anti-malarial immune profile, in populations residing in epidemic-prone areas in the dry season or at the time when vector control largely reduced man-mosquito contact, would help predict malaria burden when future epidemics occur. Methods: A cross-sectional study was designed to investigate antibody responses to four P. falciparum blood stage vaccine candidate antigens in non-febrile individuals from Shewa Robit in north-central Ethiopia where malaria transmission was expected at a minimal level as a result of the sampling season and effective vector control. Blood samples were analyzed microscopically for Plasmodium detection. The enzyme-linked immunosorbent assay (ELISA) was used to measure immunoglobulin (IgG) antibodies to apical membrane antigen 1 (AMA1), glutamaterich protein (GLURP) R2 region and merozoite surface protein 2 (MSP2) allelic variants. Results: Study participants were smear-negative for Plasmodium infection. While 51 (22%) of the participants reported that they had never been exposed to clinical malaria in life, 177 (78%) reported at least one clinical malaria episode with laboratory confirmed P. falciparum infection. The antigens tested were well-recognized by the test sera although significant differences were observed in antibody prevalence and level between the different antigens and there was inter-individual variability. IgG response to the antigens showed age-related pattern but without evidence of relation with status and frequency of reported past exposure to clinical malaria. Conclusion: The data suggests that individuals in an epidemic-prone malaria setting have reactive and stable antibodies that readily recognize P. falciparum blood-stage vaccine candidate antigens in the absence of slidepositivity. Analysis of age-related pattern in antibody level showed positive association with age but unrelated with increasing frequency of reported episode suggesting the role of intrinsic age-related factors in malaria immune maturation.