Phase 1 Study of the Safety and Immunogenicity of a Malaria Transmission-blocking Pfs25-Pfs25 Conjugate Vaccine

Background:

• Malaria, a disease transmitted by mosquitoes, affects millions of people with the highest frequency, morbidity, and mortality in infants and young children. Plasmodium falciparum and Plasmodium vivax, the most common and severe forms of malaria, have host- and stage-specific proteins that can induce immunity to the disease.
• Vaccines against stages that infect mosquitoes will prevent the spread of malaria. Researchers have developed a vaccine composed of a single protein, Pfs25, to induce antibodies in the human host that will be ingested by the mosquito and prevent the malaria parasite from reproducing and stop transmission of the disease. Because Pfs25 is present only in the mosquito, humans do not develop antibodies to this antigen even in endemic areas. Repeated injections of this vaccine may be necessary. Objectives: \- To establish the safety and optimal dosage of a malaria vaccine developed with the Pfs25 protein. Eligibility: \- Healthy adults between 18 and 49 years of age who have never had malaria or received a malaria vaccine. Design:
• Two doses of Pfs25 conjugate (10 micrograms and 25 micrograms) will be evaluated in this study. Participants will receive only one of these doses in order to provide the best scientific data for evaluation.
• To determine eligibility, participants will provide a medical history and have a physical examination, and will provide blood and urine samples to test for HIV/AIDS, hepatitis, and other conditions that would prevent them from participating.
• Eligible participants will receive one injection of the vaccine. The injection will be followed 30 minutes later with a temperature reading and an inspection of the vaccine site.
• Upon leaving the clinic, participants will receive diary forms, a digital thermometer, a ruler, and instructions about how to take their temperature and to measure redness and swelling (if any) at the injection site. About 6 hours later, and daily for 3 days, participants will take their temperature at home and examine the injection site. Participants will be examined at the clinic at 48 to 72 hours and on day 7 after an injection. A blood sample will be taken 1 week after immunization. - Participants will receive a second and third injection of the same vaccine at 6-week intervals, and will follow the same recording procedure given above. Further blood samples will be taken at regular intervals for up to 12 months after the vaccination, as directed by the study researchers.