Malaria
Conditions
Brief summary
The proposed trial design has been developed to assess the consistency and reproducibility of two consecutive direct skin feeding assays (DSFA) at 24-hour interval.
Detailed description
The proposed trial design has been developed to assess the consistency and reproducibility of two consecutive direct skin feeding assays (DSFA) at 24-hour interval. The results will determine the type of pivotal trial design for a follow-on Phase 2b trial whose objective is to bridge the standard membrane feeding assay (SMFA) to the direct skin feeding assay (DSFA) and direct membrane feeding assay (DMFA) using a monoclonal antibody intervention, TB31F monoclonal antibody (mAb), which interrupts transmission from human to mosquito. The results from this experimental medicine study will inform whether the preferred Before-After trial design in which each human volunteer serves as their own internal control can be utilized for a follow-on Phase 2b trial.
Interventions
OTHERDirect Skin Feeding Assay (DSFA)
In the direct feeding assay a cup with 60 unfed, sterile insectary-reared Anopheles gambiae mosquitoes will be allowed to feed on a participant's calf or arm for 15 minutes.
DRUGPrimaquine
Participants will receive one dose of primaquine 26.3 mg tablet on Day 2 after completion of the direct feeding assay.
Participants will receive artemether (80 mg) and lumefantrine (480 mg) combination tablets twice a day for 3 days, starting after completion of the direct feeding assay on Day 2.
Sponsors
Walter Reed Army Institute of Research (WRAIR)
Kenya Medical Research Institute
PATH
Study design
Observational model
OTHER
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to 55 Years
Inclusion criteria
* Provision of signed or thumb printed and dated informed consent form * Stated willingness to comply with all study procedures and availability for the duration of the study * Male or female aged between 18 years and 55 years inclusive. * Resident within the study area * In good general health as evidenced by medical history and clinical examination before entering the study Ability to take oral Coartem and low-dose primaquine anti-malarials upon conclusion of day 2 (2nd direct skin feed) and be willing to adhere to the medication regimen * For females, she must be of non-childbearing potential or use appropriate measures to prevent pregnancy for 30 days after receiving Coartem and primaquine. Non-childbearing potential means she is surgically sterilized or at least one year post-menopausal. Appropriate measures to prevent pregnancy include abstinence or adequate contraceptive precautions (i.e. intrauterine contraceptive device; oral contraceptives; diaphragm or condom in combination with contraceptive jelly, cream or foam; Norplant or Depo-Provera). * For males, he must be willing to ensure that he does not get his partner(s) pregnant for at least 3 months after treatment with primaquine. Appropriate measures to prevent pregnancy include abstinence or adequate contraceptive precautions in either the participant or the partner. * Positive for P. falciparum gametocytes as measured by polymerase chain reaction (PCR) with cycle threshold (cT) value \< 31.
Exclusion criteria
Presence of any signs or symptoms of malaria * Presence of contraindications to administration of Coartem and primaquine as indicated in the respective drug package inserts * History of severe allergic reactions to mosquito bites (other than pruritus and local swelling) * Pregnant (i.e. a positive pregnancy test) * Current or recent (within the preceding 2 weeks) use of antimalarial treatment * Current participation in a malaria vaccine study * Any other findings that the investigator feels would increase the risk of having an adverse outcome from participation in the trial.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Oocyst Prevalence | Feeding assays were performed on Day 1 and Day 2; Oocyst prevalence in surviving mosquitoes was assessed 9 days after feeding (Days 9 and 10). | Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst prevalence is defined as the percentage of mosquitoes in a cup with at least one oocyst detected in the mid-gut among the surviving mosquitoes (in the same cup) that underwent the feeding assays. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Oocyst Density | Feeding assays were performed on Day 1 and Day 2; Oocyst density in surviving mosquitos was assessed 9 days after feeding (Days 9 and 10). | Participants underwent feeding assays on two days, 24 hours apart (Day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst density is defined as the mean number of oocysts detected in infected mosquitoes that underwent feeding assays on the same participant. |
| Sporozoite Prevalence | Feeding assays were performed on Day 1 and Day 2; Sporozoite prevalence in surviving mosquitoes was assessed 14 days after feeding (Days 14 and 15). | Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 14 days to allow sporozoite development. Sporozoites are the forms of the plasmodium that are liberated from the oocysts in the mosquito, accumulate in the salivary glands of the mosquito, and are transferred to humans when the mosquito feeds. Fourteen days after feeding, salivary glands were dissected from live mosquitoes submerged in phosphate-buffered saline (PBS) in order to visualize motile sporozoites by microscopy. Sporozoite prevalence was recorded. Sporozoite prevalence is defined as the percentage of mosquitoes in a cup with at least one sporozoite detected in the salivary glands among the mosquitoes (in the same cup) that underwent feeding assays. |
| Sporozoite Density | Day 1 and Day 2 | Sporozoite density is defined as the mean number of sporozoites detected in infected mosquitoes that underwent feeding assays. Due to limitation on the state of the art, it was not possible to estimate the sporozoite density using the Optical Microscopy technique. |
Countries
Kenya
Participant flow
Recruitment details
Healthy adults with no malaria symptoms were recruited from the villages in the Kombewa Health and Demographics Surveillance System (HDSS) consisting of half of Kisumu West and all of Seme Sub-Counties of Kisumu County in Kenya.
Pre-assignment details
Four hundred participants consented and underwent screening. After informed consent was obtained participants were tested for the presence of mature stage malarial parasites (called gametocytes) in their blood. Forty-two participants met the inclusion criteria and were gametocyte positive and agreed to participate in the mosquito feeding assays.
Participants by arm
| Arm | Count |
|---|---|
| Study Volunteers Participants provided a blood sample on Day 1 for Direct Membrane Feeding Assay (DMFA) testing prior to participating in the Direct Skin Feeding Assay (DSFA). On Day 2 participants underwent the second DMFA and DSFA assay (within 24 hours of the first assays).
Upon completion of Day 2 DSFA participants received one dose of primaquine and Coartem for 3 days. | 42 |
| Total | 42 |
Baseline characteristics
| Characteristic | Study Volunteers | — |
|---|---|---|
| Age, Continuous | 33.4 years STANDARD_DEVIATION 9.3 | — |
| Ever had malaria? No | 0 Participants | — |
| Ever had malaria? Yes | 42 Participants | — |
| Race and Ethnicity Not Collected | — | — Participants |
| Region of Enrollment Kenya | 42 participants | — |
| Sex: Female, Male Female | 22 Participants | — |
| Sex: Female, Male Male | 20 Participants | — |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | 0 / 42 |
| other Total, other adverse events | 32 / 42 |
| serious Total, serious adverse events | 0 / 42 |
Outcome results
Primary
Oocyst Prevalence
Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst prevalence is defined as the percentage of mosquitoes in a cup with at least one oocyst detected in the mid-gut among the surviving mosquitoes (in the same cup) that underwent the feeding assays.
Time frame: Feeding assays were performed on Day 1 and Day 2; Oocyst prevalence in surviving mosquitoes was assessed 9 days after feeding (Days 9 and 10).
Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis.~The number of mosquitoes analyzed reflects the number of surviving mosquitoes after 9 days for each feeding assay and time point.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Direct Skin Feeding Assay | Oocyst Prevalence | Day 2 Feeding Assay | 2.3 percentage of mosquitoes | Standard Deviation 4.9 |
| Direct Skin Feeding Assay | Oocyst Prevalence | Day 1 Feeding Assay | 5.2 percentage of mosquitoes | Standard Deviation 7.8 |
| Direct Membrane Feeding Assay | Oocyst Prevalence | Day 2 Feeding Assay | 2.2 percentage of mosquitoes | Standard Deviation 4.4 |
| Direct Membrane Feeding Assay | Oocyst Prevalence | Day 1 Feeding Assay | 6.3 percentage of mosquitoes | Standard Deviation 16.2 |
Comparison: Comparison of DSFA Day 2 versus Day 1. For each participant, the difference in oocyte prevalence using DSFA on Day 1 versus Day 2 was estimated. To evaluate the hypothesis that the average mean difference in the prevalence between two assays within the same subject is zero, combined estimates (weighted mean and variance) were obtained using as weight the inverse of the variance of each paired difference obtained from the Agresti and Caffo method.p-value: 0.71195% CI: [-0.16, 0.109]Other
Comparison: Comparison of DMFA Day 2 versus Day 1. For each participant, the difference in oocyte prevalence using DMFA on Day 1 versus Day 2 was estimated. To evaluate the hypothesis that the average mean difference in the prevalence between two assays within the same subject is zero, combined estimates (weighted mean and variance) were obtained using as weight the inverse of the variance of each paired difference obtained from the Agresti and Caffo method.p-value: 0.79595% CI: [-0.139, 0.107]Other
Secondary
Oocyst Density
Participants underwent feeding assays on two days, 24 hours apart (Day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst density is defined as the mean number of oocysts detected in infected mosquitoes that underwent feeding assays on the same participant.
Time frame: Feeding assays were performed on Day 1 and Day 2; Oocyst density in surviving mosquitos was assessed 9 days after feeding (Days 9 and 10).
Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis.~The number of mosquitoes analyzed reflects the number of surviving mosquitos after 9 days for each feeding assay and time point.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Direct Skin Feeding Assay | Oocyst Density | Day 1 Feeding Assay | 1.1 oocysts / mosquito | Standard Deviation 1.8 |
| Direct Skin Feeding Assay | Oocyst Density | Day 2 Feeding Assay | 0.4 oocysts / mosquito | Standard Deviation 0.8 |
| Direct Membrane Feeding Assay | Oocyst Density | Day 1 Feeding Assay | 1.6 oocysts / mosquito | Standard Deviation 4.1 |
| Direct Membrane Feeding Assay | Oocyst Density | Day 2 Feeding Assay | 0.4 oocysts / mosquito | Standard Deviation 0.8 |
Comparison: Comparison of DSFA Day 2 versus Day 1.p-value: 0.01995% CI: [0.21, 0.7]Poisson Regression
Comparison: Comparison of DMFA Day 2 versus Day 1.p-value: 0.00395% CI: [0.11, 0.45]Poisson Regression
Secondary
Sporozoite Density
Sporozoite density is defined as the mean number of sporozoites detected in infected mosquitoes that underwent feeding assays. Due to limitation on the state of the art, it was not possible to estimate the sporozoite density using the Optical Microscopy technique.
Time frame: Day 1 and Day 2
Population: The analysis of sporozoite density could not be conducted due to technical limitations.
Secondary
Sporozoite Prevalence
Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 14 days to allow sporozoite development. Sporozoites are the forms of the plasmodium that are liberated from the oocysts in the mosquito, accumulate in the salivary glands of the mosquito, and are transferred to humans when the mosquito feeds. Fourteen days after feeding, salivary glands were dissected from live mosquitoes submerged in phosphate-buffered saline (PBS) in order to visualize motile sporozoites by microscopy. Sporozoite prevalence was recorded. Sporozoite prevalence is defined as the percentage of mosquitoes in a cup with at least one sporozoite detected in the salivary glands among the mosquitoes (in the same cup) that underwent feeding assays.
Time frame: Feeding assays were performed on Day 1 and Day 2; Sporozoite prevalence in surviving mosquitoes was assessed 14 days after feeding (Days 14 and 15).
Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis.~The number of mosquitoes analyzed reflects the number of surviving mosquitos after 14 days for each feeding assay and time point.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Direct Skin Feeding Assay | Sporozoite Prevalence | Day 1 Feeding Assay | 5.1 percentage of mosquitoes | Standard Deviation 8.4 |
| Direct Skin Feeding Assay | Sporozoite Prevalence | Day 2 Feeding Assay | 1.8 percentage of mosquitoes | Standard Deviation 4.8 |
| Direct Membrane Feeding Assay | Sporozoite Prevalence | Day 1 Feeding Assay | 4.5 percentage of mosquitoes | Standard Deviation 8 |
| Direct Membrane Feeding Assay | Sporozoite Prevalence | Day 2 Feeding Assay | 2.0 percentage of mosquitoes | Standard Deviation 5.7 |
Comparison: Comparison of DSFA Day 2 versus Day 1. For each participant, the difference in sporozoite prevalence using DSFA on Day 1 versus Day 2 was estimated. To evaluate the hypothesis that the average mean difference in the prevalence between two assays within the same subject is zero, combined estimates (weighted mean and variance) were obtained using as weight the inverse of the variance of each paired difference obtained from the Agresti and Caffo method.p-value: 0.7595% CI: [-0.164, 0.118]Other
Comparison: Comparison of DMFA Day 2 versus Day 1. For each participant, the difference in sporozoite prevalence using DMFA on Day 1 versus Day 2 was estimated. To evaluate the hypothesis that the average mean difference in the prevalence between two assays within the same subject is zero, combined estimates (weighted mean and variance) were obtained using as weight the inverse of the variance of each paired difference obtained from the Agresti and Caffo method.p-value: 0.68195% CI: [-0.178, 0.117]Other