This is a single-center, open label study. The primary aim of this project is to develop a controlled human malaria infection transmission model ("CHMI-trans") or "challenge model" to evaluate the capacity of vaccines, biologics (monoclonal antibodies, or mAbs), and drugs to block malaria parasite transmission by assessing infectiousness of Plasmodium falciparum (Pf) gametocyte carriers for Anopheles mosquitoes.
A total of 24 volunteers, in two cohorts (n=12), will be randomly assigned to two groups per cohort (n=6). Cohort A will be subjected to a standard controlled human malaria infection (CHMI) delivered by five Pf-infected mosquitoes (groups 1 and 2). Cohort B will be subjected to a standard blood stage challenge with \~2,800 Pf-infected erythrocytes by intravenous injection (groups 3 and 4). Treatment is subsequently initiated to induce gametocytemia (treatment 1, T1) and to clear pathogenic asexual parasites whilst leaving gametocytes unaffected (treatment 2 and 3, T2 and T3). At the end of the study, treatment of all parasite stages is provided following national treatment guidelines (end treatment, ET). Once malaria infections are detected by 18S qPCR positive (sporozoite challenge) or on day 8 (blood stage challenge), all volunteers will be treated with a single oral subcurative low-dose of piperaquine (LD-PIP, 480 mg, T1). Using blood samples taken twice daily, the initial clearance of parasitemia will be carefully monitored. After T1, volunteers will receive a second treatment (T2, LD-PIP2, 480mg) if a recrudescence of asexual parasitemia occurs before day 21 post challenge infection. On day 21 or when a recrudescence occurs after T2, volunteers in group 1 and 3 (LD-PIP/LD-PIP2/PIP) will be curatively treated with piperaquine (960mg) and group 2 and 4 (LD-PIP/LD-PIP2/SP) with sulfadoxine-pyrimethamine (1000mg/50mg). These treatment regimens cure asexual parasitemia while leaving immature and mature gametocytes unaffected. To ensure the radical clearance of all parasite stages, all volunteers will receive a final treatment (ET) according to national guidelines with atovaquone/proguanil (Malarone®) on day 36. Daily blood samples will allow detailed quantification of gametocytes, gametocyte sex ratio and ex vivo assessments of gametocyte fitness. Additionally, blood samples will be obtained for Direct Membrane Feeding Assay (DMFA) and volunteers will be subjected to Direct Skin Feeding Assays (DFA). These assays will provide evidence on the infectivity of volunteers.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
24
subcurative regimen (480 mg)
Curative regimen (960mg)
Curative regimen (1000mg/50mg)
Curative regimen (1000/400 mg, for 3 days)
malaria challenge infection by P. falciparum 3D7-infected mosquito bites
P. falciparum 3D7-infected human erythrocytes administered intravenously for the purpose controlled human malaria infection.
Radboud university medical center
Nijmegen, Gelderland, Netherlands
Frequency of Adverse Events in the CHMI-trans Model
Frequency of adverse events in the CHMI-trans model.
Time frame: up to day 51 after challenge infection
Gametocyte Prevalence
Number of individuals in each study arm that show prevalence of gametocytes as defined by quantitative reverse-transcriptase PCR (qRT-PCR) for CCp4 (female) and PfMGET (male) mRNA with a threshold of 5 gametocytes/mL for positivity.
Time frame: up to day 51 after challenge infection
Magnitude of Adverse Events in the CHMI-trans Model
symptoms will be ranked as (1) mild, (2) moderate, or (3) severe, depending on their intensity according to the following scale: * Mild (grade 1): awareness of symptoms that are easily tolerated and do not interfere with usual daily activity * Moderate (grade 2): discomfort that interferes with or limits usual daily activity * Severe (grade 3): disabling, with subsequent inability to perform usual daily activity, resulting in absence or required bed rest
Time frame: up to day 51 after challenge infection
Peak Density Gametocytes
Peak density of gametocytes by qRT-PCR.
Time frame: up to day 51 after challenge infection
AUC Gametocytes
The area under the curve of gametocyte density versus time. The median AUC was calculated for both cohorts. Since onset of gametocytaemia differs depending on method of infection a window of 15 days was used to calculate AUC, from the time-point where a minimum of 50% of participants within a cohort had detectable gametocytemia.
Time frame: up to day 51 after challenge infection
Gametocyte Commitment
The gametocyte commitment rate is estimated by dividing the peak gametocyte by the peak of asexual parasites.
Time frame: up to day 51 after challenge infection
Gametocyte Sex-ratio
Proportion of male gametocytes
Time frame: up to day 51 after challenge infection
Number of Participants Infectious for Mosquitoes Through DFA
Prevalence of gametocyte infectiousness for Anopheles mosquitoes through Direct Feeding Assays (Direct Skin Feeding Assay, DFA).
Time frame: up to day 51 after challenge infection
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