Seven-year kinetics of RTS, S/AS01-induced anti-CSP antibodies in young Kenyan children

• Published in: Malaria journal 2021-12, Vol.20 (1), p.452-452, Article 452
• Main Authors: Mugo, Robert M, Mwai, Kennedy, Mwacharo, Jedidah, Shee, Faiz M, Musyoki, Jennifer N, Wambua, Juliana, Otieno, Edward, Bejon, Philip, Ndungu, Francis M
• Format: Article
• Language: English
• Subjects: Antibodies; Antibodies, Protozoan - immunology; Antigens; Binding sites; Children; Circumsporozoite protein; Clinical trials; Disease control; ELISA; Enzyme-linked immunosorbent assay; Evaluation; Health aspects; Human diseases; Humans; Immunization; Immunoglobulin G; Immunoglobulin M; Infant; Insecticides; Kenya; Kinetics; Malaria; Malaria vaccine; Malaria Vaccines - immunology; Medicin och hälsovetenskap; Pediatric research; Plasma; Plasmodium falciparum; Plasmodium falciparum - immunology; Prevention; Protozoan Proteins - immunology; Rabies; Retrospective Studies; RTS,S/AS01; Tetanus; Tropical diseases; Vaccination; Vaccine efficacy; Vaccine Efficacy - statistics & numerical data; Vaccines; Vector-borne diseases
• ISSN: 1475-2875; 1475-2875
• DOI: 10.1186/s12936-021-03961-2

RTS,S/AS01, the leading malaria vaccine has been recommended by the WHO for widespread immunization of children at risk. RTS,S/AS01-induced anti-CSP IgG antibodies are associated with the vaccine efficacy. Here, the long-term kinetics of RTS,S/AS01-induced antibodies was investigated. 150 participants were randomly selected from the 447 children who participated in the RTS,S/AS01 phase IIb clinical trial in 2007 from Kilifi-Kenya. Cumulatively, the retrospective follow-up period was 93 months with annual plasma samples collection. The levels of anti-CSP IgM, total IgG, IgG1, IgG2, IgG3, and IgG4 antibodies were then determined using an enzyme-linked immunosorbent assay. RTS,S/AS01 induced high levels of anti-CSP IgG antibodies which exhibited a rapid waning over 6.5 months post-vaccination, followed by a slower decay over the subsequent years. RTS,S/AS01-induced anti-CSP IgG antibodies remained elevated above the control group levels throughout the 7 years follow-up period. The anti-CSP IgG antibodies were mostly IgG1, IgG3, IgG2, and to a lesser extent IgG4. IgG2 predominated in later timepoints. RTS,S/AS01 also induced high levels of anti-CSP IgM antibodies which increased above the control group levels by month 3. The controls exhibited increasing levels of the anti-CSP IgM antibodies which caught up with the RTS,S/AS01 vaccinees levels by month 21. In contrast, there were no measurable anti-CSP IgG antibodies among the controls. RTS,S/AS01-induced anti-CSP IgG antibodies kinetics are consistent with long-lived but waning vaccine efficacy. Natural exposure induces anti-CSP IgM antibodies in children, which increases with age, but does not induce substantial levels of anti-CSP IgG antibodies.