Phase I/IIa double-blind randomized (adjuvant)-controlled trial. 16 volunteers are randomized to receive two doses of either 30 µg of PfCS102 formulated in Montanide ISA 720 (verum) or ISA 720 alone (control), 60 days apart. Two weeks after the 2nd immunization, 14 volunteers are challenged with bites of 5 infected mosquitoes using the NF54 strain of P. falciparum. The main outcome will be the length of time between artificial challenge and development of blood stage parasitaemia detected by microscopy performed twice a day.

Inclusion Criteria:

• resident in or near Lausanne;
• age >18 and <45 years;
• written informed consent;
• >10/12 correct responses to the questionnaire of understanding.

Exclusion Criteria:

• history of malaria; possible exposure to malaria within the previous 6 months;
• positive serology for PfCS102by ELISA;
• history of severe reactions or allergy to mosquito bites, artemether/lumefantrine (Riamet®) or vaccines;
• pregnant or lactating female;
• any confirmed or suspected immunodeficient condition;
• seropostivity for HIV;
• chronic or active neurological, gastrointestinal, cardio-vascular or respiratory disease;
• hemoglobinopathies;
• history of >2 hospitalisations for invasive bacterial infections;
• requirement of any chronic medication;
• suspected or known current alcohol or illegal drug abuse (excluding cannabis);
• any other significant finding which, in the opinion of the investigator, would significantly increase the risk of having an adverse outcome from participating in this protocol or of dropping out of the study;
• a body mass index < 18kg/m2 or > 32 kg/m2;
• evidence of past or present psychiatric condition;
• seropositivity for HIV, hepatitis C or B (other than HBs Ab);
• 10-year risk of coronary heart disease <10%;
• any clinically significant deviation from the normal range in biochemistry or haematology blood tests or in urine analysis.