Measuring naturally acquired immune responses to candidate malaria vaccine antigens in Ghanaian adults

Malaria Journal

Research

Sanjai Kumar¹  Michael R Hollingdale²  Kwadwo A Koram³  Daniel Dodoo³  Dorothy Anum³  Susan Adu-Amankwah³  Ben Gyan³  Josephine Ocran³  William O Rogers⁴  Bartholomew D Akanmori⁵  Denise L Doolan⁶  Donald Brambilla⁷  Glenna Banania⁸  Martha Sedegah⁸  Renato Sayo⁸  Thomas L Richie⁸  Esteban Abot⁸  Jennylyn Legano⁸  Judith Epstein⁸  Harini Geneshan⁸ 

[1] Center for Biologics Review and Research, Food and Drug Administration, 20892, Rockville, MD, USA;Consultant to the US Military Malaria Vaccine Program, Naval Medical Research Center, 20910, Silver Spring, MD, USA;Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana;Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana;Naval Medical Research Unit #3, Cairo, Egypt;Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana;WHO Regional Office for Africa, Brazzaville, Congo Republic;Queensland Institute for Medical Research, Brisbane, QLD, Australia;RTI Rockville, 20852, Rockville, MD, USA;US Military Malaria Vaccine Program, Naval Medical Research Center, 20910, Silver Spring, MD, USA;

关键词: Malaria;    ELISpot Assay;    Malaria Vaccine;    Peptide Pool;    Stringent Method;   

DOI  :  10.1186/1475-2875-10-168

 received in 2011-04-12, accepted in 2011-06-20,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundTo prepare field sites for malaria vaccine trials, it is important to determine baseline antibody and T cell responses to candidate malaria vaccine antigens. Assessing T cell responses is especially challenging, given genetic restriction, low responses observed in endemic areas, their variability over time, potential suppression by parasitaemia and the intrinsic variability of the assays.MethodsIn Part A of this study, antibody titres were measured in adults from urban and rural communities in Ghana to recombinant Plasmodium falciparum CSP, SSP2/TRAP, LSA1, EXP1, MSP1, MSP3 and EBA175 by ELISA, and to sporozoites and infected erythrocytes by IFA. Positive ELISA responses were determined using two methods. T cell responses to defined CD8 or CD4 T cell epitopes from CSP, SSP2/TRAP, LSA1 and EXP1 were measured by ex vivo IFN-γ ELISpot assays using HLA-matched Class I- and DR-restricted synthetic peptides. In Part B, the reproducibility of the ELISpot assay to CSP and AMA1 was measured by repeating assays of individual samples using peptide pools and low, medium or high stringency criteria for defining positive responses, and by comparing samples collected two weeks apart.ResultsIn Part A, positive antibody responses varied widely from 17%-100%, according to the antigen and statistical method, with blood stage antigens showing more frequent and higher magnitude responses. ELISA titres were higher in rural subjects, while IFA titres and the frequencies and magnitudes of ex vivo ELISpot activities were similar in both communities. DR-restricted peptides showed stronger responses than Class I-restricted peptides. In Part B, the most stringent statistical criteria gave the fewest, and the least stringent the most positive responses, with reproducibility slightly higher using the least stringent method when assays were repeated. Results varied significantly between the two-week time-points for many participants.ConclusionsAll participants were positive for at least one malaria protein by ELISA, with results dependent on the criteria for positivity. Likewise, ELISpot responses varied among participants, but were relatively reproducible by the three methods tested, especially the least stringent, when assays were repeated. However, results often differed between samples taken two weeks apart, indicating significant biological variability over short intervals.

【 授权许可】

Unknown   
© Dodoo et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.