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Non-apical membrane antigen 1 (AMA1) IgGs from Malian children interfere with functional activity of AMA1 IgGs as judged by growth inhibition assay.

Miura K, Perera S, Brockley S, Zhou H, Aebig JA, Moretz SE, Miller LH, Doumbo OK, Sagara I, Dicko A, Ellis RD, Long CA - PLoS ONE (2011)

Bottom Line: Interestingly, the interference effect was higher with non-AMA1 IgGs from higher titer pools.The non-AMA1 IgGs did not compete with anti-AMA1 antibody in U.S.-total IgG in the competition ELISA.This study indicates that anti-malaria IgGs induced by natural exposure may interfere with the biological effect of antibody induced by an AMA1-based vaccine in the target population.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America.

ABSTRACT

Background: Apical membrane antigen 1 (AMA1) is one of the best-studied blood-stage malaria vaccine candidates. When an AMA1 vaccine was tested in a malaria naïve population, it induced functionally active antibodies judged by Growth Inhibition Assay (GIA). However, the same vaccine failed to induce higher growth-inhibitory activity in adults living in a malaria endemic area. Vaccination did induce functionally active antibodies in malaria-exposed children with less than 20% inhibition in GIA at baseline, but not in children with more than that level of baseline inhibition.

Methods: Total IgGs were purified from plasmas collected from the pediatric trial before and after immunization and pools of total IgGs were made. Another set of total IgGs was purified from U.S. adults immunized with AMA1 (US-total IgG). From these total IgGs, AMA1-specific and non-AMA1 IgGs were affinity purified and the functional activity of these IgGs was evaluated by GIA. Competition ELISA was performed with the U.S.-total IgG and non-AMA1 IgGs from malaria-exposed children.

Results: AMA1-specific IgGs from malaria-exposed children and U.S. vaccinees showed similar growth-inhibitory activity at the same concentrations. When mixed with U.S.-total IgG, non-AMA1 IgGs from children showed an interference effect in GIA. Interestingly, the interference effect was higher with non-AMA1 IgGs from higher titer pools. The non-AMA1 IgGs did not compete with anti-AMA1 antibody in U.S.-total IgG in the competition ELISA.

Conclusion: Children living in a malaria endemic area have a fraction of IgGs that interferes with the biological activity of anti-AMA1 antibody as judged by GIA. While the mechanism of interference is not resolved in this study, these results suggest it is not caused by direct competition between non-AMA1 IgG and AMA1 protein. This study indicates that anti-malaria IgGs induced by natural exposure may interfere with the biological effect of antibody induced by an AMA1-based vaccine in the target population.

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Strong correlation between anti-AMA1 antibody level and the growth-inhibitory activity in AMA1-specific IgGs.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the GIA well (x-axis) are plotted against % inhibition (y-axis) of P. falciparum 3D7 (A) or FVO (B) parasites. Each AMA1-specific IgG was tested at three (for U.S. IgGs) or two (for Mali IgGs) different concentrations. All responses below the limit of detection in ELISA were assigned a value of 2 µg/ml for the analysis.
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pone-0020947-g001: Strong correlation between anti-AMA1 antibody level and the growth-inhibitory activity in AMA1-specific IgGs.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the GIA well (x-axis) are plotted against % inhibition (y-axis) of P. falciparum 3D7 (A) or FVO (B) parasites. Each AMA1-specific IgG was tested at three (for U.S. IgGs) or two (for Mali IgGs) different concentrations. All responses below the limit of detection in ELISA were assigned a value of 2 µg/ml for the analysis.

Mentions: We then investigated the biological activity of the AMA1-specific IgGs from U.S. vaccinees and Malian children by GIA (Figure 1). As in our previous study [27], the AMA1-specific IgGs from U.S. vaccinees showed a significant correlation between antibody level and percent inhibition when they were tested against the homologous strain of parasites (Spearman rank correlation, p<0.001, ρs  = 0.96, 95% confidence interval (CI) 0.91–0.99 for 3D7; p<0.001, ρs  = 0.83, 95% CI 0.60–0.94, for FVO) and the relationship followed a symmetrical sigmoid curve when the antibody levels were log transformed (r2 = 0.93 for 3D7 and 0.82 for FVO). The AMA1-specific IgGs from Malian children showed almost the same level of growth-inhibitory activity at the same level of antibody in the GIA well, regardless of which pools of total IgG were tested. When the data from all AMA1-specific IgGs from Malian children were combined, there were significant correlations between antibody levels by ELISA and percent inhibition in GIA (for 3D7, p<0.001, ρs  = 0.97, 95% CI 0.92–0.99; for FVO, p<0.001, ρs  = 0.94, 95% CI 0.86–0.98), and each relationship followed a symmetrical sigmoid curve (r2 = 0.99 for 3D7, 0.94 for FVO). These results indicate that there was no obvious difference in biological activity of antibodies among AMA1-specific IgGs induced by an AMA1 vaccination (IgGs from U.S. vaccinees), by natural infection (IgGs from D0-1, 2, 3 & 4 and Hib-1, 2 & 3 pools) and by both natural infection and vaccination (IgGs from AMA1-1, 2 & 3 pools).


Non-apical membrane antigen 1 (AMA1) IgGs from Malian children interfere with functional activity of AMA1 IgGs as judged by growth inhibition assay.

Miura K, Perera S, Brockley S, Zhou H, Aebig JA, Moretz SE, Miller LH, Doumbo OK, Sagara I, Dicko A, Ellis RD, Long CA - PLoS ONE (2011)

Strong correlation between anti-AMA1 antibody level and the growth-inhibitory activity in AMA1-specific IgGs.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the GIA well (x-axis) are plotted against % inhibition (y-axis) of P. falciparum 3D7 (A) or FVO (B) parasites. Each AMA1-specific IgG was tested at three (for U.S. IgGs) or two (for Mali IgGs) different concentrations. All responses below the limit of detection in ELISA were assigned a value of 2 µg/ml for the analysis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3113848&req=5

pone-0020947-g001: Strong correlation between anti-AMA1 antibody level and the growth-inhibitory activity in AMA1-specific IgGs.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the GIA well (x-axis) are plotted against % inhibition (y-axis) of P. falciparum 3D7 (A) or FVO (B) parasites. Each AMA1-specific IgG was tested at three (for U.S. IgGs) or two (for Mali IgGs) different concentrations. All responses below the limit of detection in ELISA were assigned a value of 2 µg/ml for the analysis.
Mentions: We then investigated the biological activity of the AMA1-specific IgGs from U.S. vaccinees and Malian children by GIA (Figure 1). As in our previous study [27], the AMA1-specific IgGs from U.S. vaccinees showed a significant correlation between antibody level and percent inhibition when they were tested against the homologous strain of parasites (Spearman rank correlation, p<0.001, ρs  = 0.96, 95% confidence interval (CI) 0.91–0.99 for 3D7; p<0.001, ρs  = 0.83, 95% CI 0.60–0.94, for FVO) and the relationship followed a symmetrical sigmoid curve when the antibody levels were log transformed (r2 = 0.93 for 3D7 and 0.82 for FVO). The AMA1-specific IgGs from Malian children showed almost the same level of growth-inhibitory activity at the same level of antibody in the GIA well, regardless of which pools of total IgG were tested. When the data from all AMA1-specific IgGs from Malian children were combined, there were significant correlations between antibody levels by ELISA and percent inhibition in GIA (for 3D7, p<0.001, ρs  = 0.97, 95% CI 0.92–0.99; for FVO, p<0.001, ρs  = 0.94, 95% CI 0.86–0.98), and each relationship followed a symmetrical sigmoid curve (r2 = 0.99 for 3D7, 0.94 for FVO). These results indicate that there was no obvious difference in biological activity of antibodies among AMA1-specific IgGs induced by an AMA1 vaccination (IgGs from U.S. vaccinees), by natural infection (IgGs from D0-1, 2, 3 & 4 and Hib-1, 2 & 3 pools) and by both natural infection and vaccination (IgGs from AMA1-1, 2 & 3 pools).

Bottom Line: Interestingly, the interference effect was higher with non-AMA1 IgGs from higher titer pools.The non-AMA1 IgGs did not compete with anti-AMA1 antibody in U.S.-total IgG in the competition ELISA.This study indicates that anti-malaria IgGs induced by natural exposure may interfere with the biological effect of antibody induced by an AMA1-based vaccine in the target population.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America.

ABSTRACT

Background: Apical membrane antigen 1 (AMA1) is one of the best-studied blood-stage malaria vaccine candidates. When an AMA1 vaccine was tested in a malaria naïve population, it induced functionally active antibodies judged by Growth Inhibition Assay (GIA). However, the same vaccine failed to induce higher growth-inhibitory activity in adults living in a malaria endemic area. Vaccination did induce functionally active antibodies in malaria-exposed children with less than 20% inhibition in GIA at baseline, but not in children with more than that level of baseline inhibition.

Methods: Total IgGs were purified from plasmas collected from the pediatric trial before and after immunization and pools of total IgGs were made. Another set of total IgGs was purified from U.S. adults immunized with AMA1 (US-total IgG). From these total IgGs, AMA1-specific and non-AMA1 IgGs were affinity purified and the functional activity of these IgGs was evaluated by GIA. Competition ELISA was performed with the U.S.-total IgG and non-AMA1 IgGs from malaria-exposed children.

Results: AMA1-specific IgGs from malaria-exposed children and U.S. vaccinees showed similar growth-inhibitory activity at the same concentrations. When mixed with U.S.-total IgG, non-AMA1 IgGs from children showed an interference effect in GIA. Interestingly, the interference effect was higher with non-AMA1 IgGs from higher titer pools. The non-AMA1 IgGs did not compete with anti-AMA1 antibody in U.S.-total IgG in the competition ELISA.

Conclusion: Children living in a malaria endemic area have a fraction of IgGs that interferes with the biological activity of anti-AMA1 antibody as judged by GIA. While the mechanism of interference is not resolved in this study, these results suggest it is not caused by direct competition between non-AMA1 IgG and AMA1 protein. This study indicates that anti-malaria IgGs induced by natural exposure may interfere with the biological effect of antibody induced by an AMA1-based vaccine in the target population.

Show MeSH
Related in: MedlinePlus