This study will assess the durability of protection of a single immunisation with the Genetically Attenuated Parasite 2 (GA2) against controlled human malaria infection by rechallenging previously immunised and protected participants from the CoGA study (NCT05468606)
This will be a non-randomised, open-label, controlled human malaria infection study that will consist of two study arms: the rechallenge group and infection controls. The rechallenge group consists of study participants from the CoGA study (phase I) who received single immunisation with GA2 and were protected during subsequent CHMI, while infection controls are newly recruited, malaria-naïve study participants. All participants will undergo CHMI through the bites of 5 mosquitos infected with wild-type 3D7 sporozoites. From day 6 to 21 after CHMI, participants will be followed daily on an out-patient basis to determine parasite loads detected by a quantitative polymerase chain reaction (qPCR). As soon as parasitaemia is detected (cut-off \>100p/mL), or at the latest 28 days after CHMI, participants will be treated with a curative regimen of antimalarials.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
14
Controlled human malaria infection with 3D7 malaria through mosquito bites
Protective efficacy
Proportion of participants that do not develop parasitaemia (qPCR \>100p/mL) (sterile protection) after CHMI (re)challenge in participants with prior, single GA2 immunisation compared to infection controls.
Time frame: Moment of CHMI to antimalarial treatment (28 days post CHMI)
Time to parasitaemia
The time to parasitaemia (qPCR \>100 p/mL) (prepatent period) after CHMI (re)challenge between participants with prior, single GA2 immunisation and infection controls.
Time frame: Moment of CHMI to antimalarial treatment (28 days post CHMI)
Humoral immune responses after homologous CHMI rechallenge
Difference in concentration of anti-CSP antibodies between groups as assessed by ELISA.
Time frame: Moment of CHMI up to182 days post CHMI
Cellular immune responses after homologous CHMI rechallenge
Difference in percentage of CD4+ and CD8+ T-cells producing IFN-γ between groups as assessed by flow cytometry
Time frame: Moment of CHMI up to182 days post CHMI
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