Objectives:

Primary:

• To characterize the infectivity of the new lot of Plasmodium falciparum strain 3D7 within the standard WRAIR CHMI model as compared to the current lot (historical data)

Secondary:

• To assess safety of the new lot of P falciparum parasites
• To assess the kinetics of detecting parasitemia and parasite clearance by quantitative polymerase chain reaction (qPCR) as compared to blood smear
• To obtain plasma samples to restore the testing control pool for malaria serology testing and for future malaria research

This is a single center, open label CHMI study. CHMI will consist of exposure to Plasmodium falciparum sporozoites through the bites of infected mosquitoes. After the challenge, subjects will be evaluated daily for the development of malaria infection using a blood smear. Unless previously diagnosed and fully treated, subjects will be required to stay in a hotel for a maximum of 12 nights starting on or around the evening of Day 7 post challenge.

All subjects diagnosed with malaria infection based on smears will be prescribed a standard malaria treatment regimen to begin on the day that parasitemia is detected. Subjects who do not become parasitemic (via smear) by Day 19 will be empirically treated for malaria.

After the hotel phase, all challenged subjects will have a final scheduled follow-up visit on Day 28 (±7 days).

Inclusion Criteria:

• To be eligible for this study, you must meet ALL of the following conditions:

  • You are between the ages of 18 and 50 years old.
  • You are willing and able to participate in all planned study visits for the duration of the study.
  • You are in good general health based on your medical history, physical examination, EKG, and screening laboratories.
  • You are able to understand and sign this informed consent.
  • You pass the written test called the 'Assessment of Understanding' with a score of at least 80% (8 out of 10 questions correct).
  • You agree not to donate blood during the study and for 3 years after the malaria challenge.
  • You agree not to travel to place(s) where there is malaria during the time of the study.
  • If you are a female, you must agree to consistently use effective birth control (e.g., oral or implanted contraceptives, intrauterine device (IUD), diaphragm with spermicide, abstinence, cervical cap) during the period from the day of screening (today) through 3 months after the malaria challenge.
  • You must be willing to take anti-malarial treatment after CHMI, if indicated.
  • You must agree to stay in a pre-determined hotel near the NMRC CTC during the designated post-CHMI follow-up period from approximately 7 days after malaria challenge until antimalarial treatment is completed, if indicated.
  • If you are an active duty military or federal employee, you must have approval from your supervisory chain to participate. The appropriate approval form will be provided to you.

Exclusion Criteria:

• You must not have any of the following:

  • Any history of malaria infection or having been given a malaria vaccine
  • Any history travel to a country with falciparum malaria in the past 6 months, or planned travel to such an area during the course of the study
  • Any history of having lived in an area with falciparum malaria for more than 5 years.
  • Any use of medications that prevent or treat malaria during the 1 month prior to challenge or planned use during the study (outside of the drugs provided by the study team).
  • Any serious medical illness or condition involving the heart, liver, lungs, or kidneys
  • Any significant risk for developing heart disease in the next 5 years. The risk for developing heart disease in the next 5 years will be determined by a combination of the following factors: high blood pressure, smoking, weight, family history of heart disease and the presence of diabetes
  • Any medical illness or condition involving your blood or immune system (to include sickle cell trait or thalassemia trait)
  • Any abnormal (as determined by a physician) screening laboratory test results
  • Any history of neurologic disease (including migraines or seizures)
  • Any history of psoriasis (itchy skin rash) or porphyria (rare disturbance of metabolism), since these conditions could get worse after treatment with chloroquine (a medication for treating malaria).
  • You have had your spleen removed
  • Any past or current infection with HIV, Hepatitis C, or Hepatitis B
  • Any use of investigational drugs or vaccines within 1 month before starting the study
  • Any allergy to or inability to take the anti-malaria medications used in this study
  • Any history of allergic reaction to mosquito bites that required hospitalization
  • You must not be pregnant or nursing, or have any plans to become pregnant or breastfeed during the period from now through 3 months after malaria challenge
  • Any chronic use of steroids or other medications that affect the immune system in the 6 months before malaria challenge. Inhaled and topical (used on the skin) steroids are allowed.
  • You plan to have surgery between enrollment and 3 months after malaria challenge.
  • Any active alcohol or drug abuse
  • You have any other physical or psychologic condition or laboratory abnormality that the study doctor thinks may increase your risk of having side effects or compromise the results of the study.

Healthy, malaria-naïve adults (males and non-pregnant, non-lactating females), aged 18 to 50 years old (inclusive) were recruited from the Washington/ Baltimore DC metropolitan area to participate in this Controlled Human Malaria Infection (CHMI) study. Up to 12 subjects were enrolled (defined as having undergone malaria challenge) into this trial. All 12 subjects were challenged with the new lot of female Anopheles mosquitoes infected with Plasmodium falciparum strain NF54 (clone 3D7), lot 1887

Day 1 through Day 35

Subjects were seen and evaluated daily and adverse event reporting collected