Liriye Kurtovic PhD , Gaoqian Feng PhD , Alessia Hysa MBSc , Ali Haghiri PhD , Katherine O’Flaherty PhD , Bruce D Wines PhD , Rebeca Santano PhD , Laura D’Andrea PhD , Prof Heidi E Drummer PhD , Prof P Mark Hogarth PhD , Prof Jahit Sacarlal PhD , Prof Freya J I Fowkes DPhil , Prof Julie A Simpson PhD , Prof Carlota Dobaño PhD , Prof James G Beeson PhD
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The immunological mechanisms of RTS,S-mediated immunity are poorly understood; therefore, we aimed to identify antibody response types associated with protection against malaria in children vaccinated with RTS,S.</div></div><div><h3>Methods</h3><div>In this post-hoc analysis, we evaluated antibody responses in 737 children aged 1–4 years vaccinated with RTS,S in a phase 2b clinical trial conducted in Mozambique in 2003. We evaluated all available samples collected from children 30 days after the three-dose vaccination schedule at study month 3 (M3; n=737 available of 803 children allocated to receive RTS,S). For comparison, we tested a subset of samples collected before vaccination at study month 0 (M0; n=50) and from children in the control vaccine group (M0 n=25; M3 n=99). We quantified the induction of antibodies to different regions of the vaccine antigen that function by fixing serum complement proteins and binding to Fcγ receptors (FcγRs; FcγRI, FcγRIIa, and FcγRIII) expressed on immune cells as potential mechanisms of immunity.</div></div><div><h3>Findings</h3><div>Functional antibody responses to the C-terminal region of the vaccine antigen, circumsporozoite protein (CSP), were associated with a reduced risk of malaria (C1q p=0·0060, FcγRIIa p=0·014, and FcγRIII p=0·019). These associations remained significant in male participants when the analyses were stratified by sex (C1q p=0·012, FcγRI p=0·023, FcγRIIa p=0·0070, and FcγRIII p=0·0080). IgA to the central repeat (p=0·0010) and C-terminal (p=0·0040) regions of CSP were also associated with protection. We show that IgA can bind FcαRI and mediate opsonic phagocytosis using a serum pool and monoclonal antibodies. 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These findings reveal new avenues that could be used to achieve malaria vaccines with higher efficacy.</div></div><div><h3>Funding</h3><div>National Health and Medical Research Council, Australia, and Thrasher Research Fund.</div></div>","PeriodicalId":46633,"journal":{"name":"Lancet Microbe","volume":null,"pages":null},"PeriodicalIF":20.9000,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Antibody mechanisms of protection against malaria in RTS,S-vaccinated children: a post-hoc serological analysis of phase 2 trial\",\"authors\":\"Liriye Kurtovic PhD , Gaoqian Feng PhD , Alessia Hysa MBSc , Ali Haghiri PhD , Katherine O’Flaherty PhD , Bruce D Wines PhD , Rebeca Santano PhD , Laura D’Andrea PhD , Prof Heidi E Drummer PhD , Prof P Mark Hogarth PhD , Prof Jahit Sacarlal PhD , Prof Freya J I Fowkes DPhil , Prof Julie A Simpson PhD , Prof Carlota Dobaño PhD , Prof James G Beeson PhD\",\"doi\":\"10.1016/S2666-5247(24)00130-7\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><h3>Background</h3><div>The RTS,S malaria vaccine is currently recommended for children aged 5–6 months in regions with moderate-to-high <em>Plasmodium falciparum</em> transmission. 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Antibody mechanisms of protection against malaria in RTS,S-vaccinated children: a post-hoc serological analysis of phase 2 trial
Background
The RTS,S malaria vaccine is currently recommended for children aged 5–6 months in regions with moderate-to-high Plasmodium falciparum transmission. However, vaccination only confers 55% efficacy over 12 months and wanes within 18 months. The immunological mechanisms of RTS,S-mediated immunity are poorly understood; therefore, we aimed to identify antibody response types associated with protection against malaria in children vaccinated with RTS,S.
Methods
In this post-hoc analysis, we evaluated antibody responses in 737 children aged 1–4 years vaccinated with RTS,S in a phase 2b clinical trial conducted in Mozambique in 2003. We evaluated all available samples collected from children 30 days after the three-dose vaccination schedule at study month 3 (M3; n=737 available of 803 children allocated to receive RTS,S). For comparison, we tested a subset of samples collected before vaccination at study month 0 (M0; n=50) and from children in the control vaccine group (M0 n=25; M3 n=99). We quantified the induction of antibodies to different regions of the vaccine antigen that function by fixing serum complement proteins and binding to Fcγ receptors (FcγRs; FcγRI, FcγRIIa, and FcγRIII) expressed on immune cells as potential mechanisms of immunity.
Findings
Functional antibody responses to the C-terminal region of the vaccine antigen, circumsporozoite protein (CSP), were associated with a reduced risk of malaria (C1q p=0·0060, FcγRIIa p=0·014, and FcγRIII p=0·019). These associations remained significant in male participants when the analyses were stratified by sex (C1q p=0·012, FcγRI p=0·023, FcγRIIa p=0·0070, and FcγRIII p=0·0080). IgA to the central repeat (p=0·0010) and C-terminal (p=0·0040) regions of CSP were also associated with protection. We show that IgA can bind FcαRI and mediate opsonic phagocytosis using a serum pool and monoclonal antibodies. Multiparameter analysis using machine-learning methods suggest that IgA, complement fixation, and FcγRI binding were most predictive of protection against malaria (hazard ratio <1) and suggested that associations differed between male and female participants.
Interpretation
We provide evidence that functional antibody responses mediated by IgG and IgA are associated with protection against malaria in young children vaccinated with RTS,S, and suggest potential differences in the correlates of immunity between males and females. These findings reveal new avenues that could be used to achieve malaria vaccines with higher efficacy.
Funding
National Health and Medical Research Council, Australia, and Thrasher Research Fund.
期刊介绍:
The Lancet Microbe is a gold open access journal committed to publishing content relevant to clinical microbiologists worldwide, with a focus on studies that advance clinical understanding, challenge the status quo, and advocate change in health policy.