Limits...
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.

Show MeSH

Related in: MedlinePlus

The correlation between anti-AMA1 antibody levels in the original total IgG pool and the interference effect of the corresponding non-AMA1 IgG.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the original total IgG pools (x-axis) are plotted against delta % inhibition of non-AMA1 IgGs (y-axis) tested with P. falciparum 3D7 (A) or FVO (B) parasites. Delta % inhibition of each non-AMA1 IgG was calculated using the data presented in Figure 3 as follows: delta % inhibition  =  (% inhibition of the US-total IgG alone (black bar in Figure 3)) - (% inhibition of a mixture of the non-AMA1 IgG and US-total IgG).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3113848&req=5

pone-0020947-g004: The correlation between anti-AMA1 antibody levels in the original total IgG pool and the interference effect of the corresponding non-AMA1 IgG.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the original total IgG pools (x-axis) are plotted against delta % inhibition of non-AMA1 IgGs (y-axis) tested with P. falciparum 3D7 (A) or FVO (B) parasites. Delta % inhibition of each non-AMA1 IgG was calculated using the data presented in Figure 3 as follows: delta % inhibition  =  (% inhibition of the US-total IgG alone (black bar in Figure 3)) - (% inhibition of a mixture of the non-AMA1 IgG and US-total IgG).

Mentions: To assess interference effect in the non-AMA1 IgGs, non-AMA1 IgGs were tested by GIA either by themselves or in the presence of total IgG from a U.S. vaccinee (US-total IgG) against homologous strain of parasites (i.e., non-AMA1(3D7) IgGs were tested with or without US-total IgG using 3D7 strain of parasites in GIA, and non-AMA1(FVO) IgGs were similarly tested using FVO parasites). The US-total IgG was also tested alone as a positive control (black bar in Figure 3). The non-AMA1 IgGs showed less than 20 % inhibition at 4 mg/ml (Figure 3). The mixtures of non-AMA1 IgGs and US-total IgG displayed lower inhibition for both 3D7 and FVO parasites compared to the US-total IgG alone. To evaluate the strength of the interference effect of each non-AMA1 IgG, the difference between US-total IgG alone and the mixture was calculated (delta % inhibition). As shown in Figure 4, the non-AMA1 IgGs purified from total IgG pools with higher AMA1 antibody levels showed greater interference (larger delta % inhibition) than those from total IgG pools with lower titer. When all of the data were combined, there was a significant correlation between the AMA1 antibody level in the original total IgG pool and the interference effect of non-AMA1 IgG (Spearman rank correlation, p = 0.021, ρs  = 0.80 for 3D7; p = 0.003, ρs  = 0.82 for FVO).


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)

The correlation between anti-AMA1 antibody levels in the original total IgG pool and the interference effect of the corresponding non-AMA1 IgG.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the original total IgG pools (x-axis) are plotted against delta % inhibition of non-AMA1 IgGs (y-axis) tested with P. falciparum 3D7 (A) or FVO (B) parasites. Delta % inhibition of each non-AMA1 IgG was calculated using the data presented in Figure 3 as follows: delta % inhibition  =  (% inhibition of the US-total IgG alone (black bar in Figure 3)) - (% inhibition of a mixture of the non-AMA1 IgG and US-total IgG).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020947-g004: The correlation between anti-AMA1 antibody levels in the original total IgG pool and the interference effect of the corresponding non-AMA1 IgG.Anti-AMA1(3D7) (A) or anti-AMA1(FVO) (B) antibody levels (µg/ml) in the original total IgG pools (x-axis) are plotted against delta % inhibition of non-AMA1 IgGs (y-axis) tested with P. falciparum 3D7 (A) or FVO (B) parasites. Delta % inhibition of each non-AMA1 IgG was calculated using the data presented in Figure 3 as follows: delta % inhibition  =  (% inhibition of the US-total IgG alone (black bar in Figure 3)) - (% inhibition of a mixture of the non-AMA1 IgG and US-total IgG).
Mentions: To assess interference effect in the non-AMA1 IgGs, non-AMA1 IgGs were tested by GIA either by themselves or in the presence of total IgG from a U.S. vaccinee (US-total IgG) against homologous strain of parasites (i.e., non-AMA1(3D7) IgGs were tested with or without US-total IgG using 3D7 strain of parasites in GIA, and non-AMA1(FVO) IgGs were similarly tested using FVO parasites). The US-total IgG was also tested alone as a positive control (black bar in Figure 3). The non-AMA1 IgGs showed less than 20 % inhibition at 4 mg/ml (Figure 3). The mixtures of non-AMA1 IgGs and US-total IgG displayed lower inhibition for both 3D7 and FVO parasites compared to the US-total IgG alone. To evaluate the strength of the interference effect of each non-AMA1 IgG, the difference between US-total IgG alone and the mixture was calculated (delta % inhibition). As shown in Figure 4, the non-AMA1 IgGs purified from total IgG pools with higher AMA1 antibody levels showed greater interference (larger delta % inhibition) than those from total IgG pools with lower titer. When all of the data were combined, there was a significant correlation between the AMA1 antibody level in the original total IgG pool and the interference effect of non-AMA1 IgG (Spearman rank correlation, p = 0.021, ρs  = 0.80 for 3D7; p = 0.003, ρs  = 0.82 for FVO).

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