Effect of RTS,S/AS01_E vaccine booster dose on cellular immune responses in African infants and children

Area of Science:

• Immunology
• Vaccinology
• Infectious Diseases

Background:

• The RTS,S/AS01E malaria vaccine showed moderate efficacy in Phase 3 trials.
• Previous studies assessed cell-mediated immune (CMI) responses after primary immunization.
• Understanding responses to booster doses is crucial for long-term vaccine effectiveness.

Purpose of the Study:

• To evaluate CMI responses following an 18-month-delayed booster dose of the RTS,S/AS01E malaria vaccine.
• To assess the association of these CMI responses with malaria risk and antibody levels post-booster.

Main Methods:

• Peripheral blood mononuclear cells from 709 children and infants were stimulated with RTS,S/AS01E antigen.
• Thirty CMI markers were quantified using Luminex assays.
• Associations with malaria incidence and anti-circumsporozoite protein (CSP) IgG levels were analyzed.

Main Results:

• RTS,S/AS01E booster vaccination was associated with increased levels of IL-2, IFN-γ, IL-17, IL-5, and IL-13.
• IL-2 responses to CSP remained elevated one year post-booster.
• Higher IL-2 levels correlated with reduced malaria risk at one site, while IL-10 was linked to increased risk in infants.

Conclusions:

• The RTS,S/AS01E booster dose induces a moderate CMI response.
• Sustained IL-2 responses and their association with reduced malaria risk suggest a role in maintaining vaccine-induced protection.
• These findings align with the partial recovery of RTS,S/AS01E vaccine efficacy observed previously.