Manufacture of Necator americanus as an infectious challenge agent: Accelerating human hookworm vaccine development

Hookworms infect 450 million people globally and account for the loss of 5 million disability-adjusted life years annually. Over the last decade, the Human Hookworm Vaccine (HHV) candidate N. americanus Glutathione-S-Transferase-1 (Na-GST-1) has advanced to efficacy testing. This manuscript describes the manufacture of third-stage N. americanus larvae (NaL3) as an infectious challenge agent to provide "proof-of-concept" for the efficacy of Na-GST-1 prior to more extensive and more resource-intensive vaccine field trials in hookworm endemic areas. NaL3 were produced from fecal samples of three hookworm-infected human donors by a modified Harada and Mori method that complied with current Good Manufacturing Practices (cGMP). A series of lot release tests assessed the purity (bioburden), viability (potency), and identity (speciation) of NaL3 before administration to participants in a hookworm vaccine challenge model (HVCM) in Washington, DC. Twenty-four production runs yielded an average of 947 NaL3 per lot, which were approved for clinical to inoculate of 39 participants in a Hookworm Vaccine Challenge Model. This manuscript describes the unique manufacture and testing for NaL3 in compliance with cGMP.