• EVI

Blood-stage malaria vaccine candidate BK-SE36 shown to be safe and immunogenic in children

05 September 2022

Malaria is a major public health concern, particularly among children in Sub-Saharan Africa, which accounts for 95% of the predicted 241 million malaria infections in 2020. A vaccine would be a significant tool for controlling morbidity and potentially limiting the future stages of human-to-mosquito transmission. The world’s most advanced malaria vaccine, RTS,S/AS01, was recently recommended by World Health Organization (WHO) for widespread use among children in sub-Saharan Africa. However, RTS,S/AS01 only confers partial protection waning over some months as antibody levels rapidly decline after vaccination. Therefore, more efforts are needed for the development of a second-generation malaria vaccine with greater efficacy and longevity in target populations.

The Plasmodium falciparum (malaria parasite) serine repeat antigen 5 (SERA5) is an abundant essential blood-stage antigen, which is suggested to be involved in parasite egress and in parasite immune evasion. SERA5 may overcome two major challenges for malaria vaccine antigens as it shows limited polymorphism and has immunodominant IgG epitopes, not requiring strict tertiary structures to elicit protective immunity.

In the study published by EVI-led consortium, SEmalvac, a recombinant version of the SERA5 N-terminal domain (SE36) formulated with aluminum hydroxyl gel (BK-SE36) was selected and produced for clinical testing.

The study was conducted at the Banfora trial centre of the Centre National de Recherche et de Formation sur le Paludisme (CNRFP) in Burkina Faso. This double-blind, randomised, controlled, age de-escalating, phase Ib clinical trial enrolled 108 healthy, malaria-exposed African children. Three doses of BK-SE36 vaccine were administered to healthy Burkinabe children aged 12 to 60 months, either by intramuscular (IM) or subcutaneous (SC) route on Day 0, Week 4, and 26. In the control arm, children received the commercially available pneumococcal polysaccharide conjugate vaccine, Synflorix®, via IM route on Day 0, Week 26 (and physiological saline on Week 4).

The primary objective of the study was to assess the safety and reactogenicity of 3 full doses of BK-SE36. There were no serious adverse events, unexpected reactions, or safety concerns during the course of the trial. BK-SE36 induced a clear humoral immune response.

Overall, the safety profile was comparable to that of the Synflorix®. In BK-SE36 vaccinees, a booster vaccination (Dose 3) resulted in higher immune responses. Antibody levels dropped to near pre-vaccination values 5 months after dose 2, but 28 days post Dose 3 antibodies were boosted, sometimes to levels higher than those induced after two vaccinations.

In sum, BK-SE36 was well tolerated and immunogenic using either intramuscular or subcutaneous routes, with higher immune response in the younger cohort. These promising results support the further development of improved BK-SE36 vaccine and future phase II trial.

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This work was supported by the Global Health Innovative Technology Fund (G2014-109)


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