A group of 24 healthy volunteers are challenged one or three times with 20 male Schistosoma mansoni cercariae to investigate whether this leads to protection and to identify potential correlates of protection
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
TRIPLE
Enrollment
24
20 viable male Schistosoma mansoni cercariae of the Puerto Rican strain
Placebo mock infection with water
Leiden University Medical Center
Leiden, Netherlands
Protective efficacy
The protective efficacy of repeated exposure to male Sm cercariae measured by the difference in frequency of serum circulating aniodic antigen (CAA) positivity (≥1.0 pg/mL) between the reinfection group and the infection control group at any timepoint after the final infection at week 18 and before week 30
Time frame: From week 18 until week 30
Safety of (repeated) exposure to male Sm cercariae based on self-reported adverse events
Frequency and severity of adverse events after (repeated) human Sm infection with male cercariae
Time frame: 38 weeks
Time to CAA positivity
Comparison of time to positive serum and urine CAA test between the reinfection and infection control groups after the final infection at week 18 and before week 30
Time frame: From week 18 until week 30
Peak serum CAA levels
Comparison of peak serum CAA concentration between the reinfection and infection control group after the final infection at week 18 and before week 30
Time frame: From week 18 until week 30
Eosinophils
Comparison of eosinophil counts between the reinfection and infection control groups after challenge after the final infection at week 18 and before week 30
Time frame: From week 18 until week 30
Antibody responses
Comparison of (glycan) antibody responses directed against Sm antigens between the reinfection and infection control participants as well as between protected and non-protected participants after the final infection at week 18 and before week 30 using protein and glycan arrays
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Time frame: From week 18 until week 30
Cellular responses
Comparison of cellular responses directed against Sm antigens between the reinfection and infection control participants as well as between protected and non-protected participants after the final infection at week 18 and before week 30 using flow cytometry
Time frame: From week 18 until week 30
Attack rate
The pooled attack rate after initial exposure to 20 male cercariae, i.e. proportion CAA positivity between week 0-8 for the reinfection participants and between week 18-26 for infection control participants
Time frame: 26 weeks