• Vaccine Name: Pfs25-EPA/Alhydrogel
• Target Pathogen: Plasmodium spp.
• Target Disease: Malaria
• Manufacturer: Walter Reed Army Institute of Research Bioproduction Facility
• Type: Subunit vaccine
• Status: Licensed
• Host Species for Licensed Use: None
• Antigen: Pfs25H is a Pichia pastoris-expressed hexa-His tagged recombinant Pfs25, a post-fertilization surface antigen of ookinetes in the mosquito stage of P. falciparum. (Talaat et al., 2016)
• Pfs25 from P. falciparum 3D7 gene engineering:
  • Type: Recombinant protein preparation
  • Description: Pfs25H is a Pichia pastoris-expressed hexa-His tagged recombinant Pfs25 used as the vaccine antigen.
  • Detailed Gene Information: Click Here.
• Preparation: The Pfs25-EPA conjugate was produced by reaction between thiolated Pfs25H and maleimide-activated rEPA, followed by purification using size-exclusion chromatography. Pfs25-EPA was subsequently formulated with Alhydrogel®. 78 μg/mL Pfs25H and 93 μg/mL rEPA, bound to 1600 μg/mL Alhydrogel® in a volume of 0.8 mL. (Talaat et al., 2016)
• Immunization Route: Intramuscular injection (i.m.)
• Description: The Pfs25-EPA/ Alhydrogel uses a recombinant Pfs25 antigen with a recombinant EPA (rEPA) formulated with an Alhydrogel adjuvant.

Human Response

• Host Strain: Healthy adults age 18–50 were recruited from the Baltimore, MD region without significant medical conditions.
• Vaccination Protocol: Participants were divided into three groups: Group 1a received two injections of a low vaccine dose (8 μg Pfs25H), Group 1b received two injections of a medium dose (16 μg Pfs25H) at 0 and 2 months, and Group 2 received four injections of a high dose (47 μg Pfs25H) at 0, 2, 4, and 10 months. Additionally, one high responder in Group 1a received a third injection of the low vaccine dose (8 μg Pfs25H) at 10 months. (Talaat et al., 2016)
• Immune Response: Proportion of antibody levels in responders increased after second, third vaccinations, and the final booster, demonstrating immunogenicity. However, antibody levels declined rapidly weeks after the final dose.