Manufacture of aseptic, purified, cryopreserved Plasmodium vivax sporozoites

ABSTRACT Malaria caused by Plasmodium vivax (Pv) parasites is ranked second with respect to the incidence and severity of disease while Plasmodium falciparum (Pf) malaria is ranked first. However unlike Pf, chemo prophylactic measures against Pv do not prevent relapses, unique to Pv, that occur due to re-activation of persistent liver-stage sleeping forms of the parasites called hypnozoites. Primaquine is the only licensed drug that targets Pv hypnozoites, but it causes life threatening acute hemolytic anemia in patients with G6PD deficiency, the most prevalent human genetic disorder, affecting 8% of people in malaria-endemic nations. Efforts to develop better drugs or produce a much needed vaccine are further hampered by the inability to propagate blood stages of Pv parasites in vitro, unlike Pf. Therefore generating infected mosquitoes for controlled human malaria infection (CHMI) as a means to assess anti-Pv drugs and vaccines, is entirely reliant on feeding of mosquitoes on fresh, Pv-infected blood from patients with Pv malaria. Together, these bottlenecks make the task of developing and testing robust interventions against Pv malaria more challenging compared to Pf. We have made significant progress under a phase I grant toward establishing and maintaining a colony of specific pathogen free (SPF) Saimiri boliviensis (Sb). and vialing aseptic, purified Plasmodium vivax (Pv) sporozoites (SPZ) that were generated in aseptic mosquitoes using infected blood from SPF Sb and met asepticity and release criteria in all in process and for release. We now outline phase 2 follow-up plans to manufacture a lot of PvSPZ Challenge in compliance with cGMPs, conduct quality control release and stability studies, prepare a clinical trial protocol, and prepare and submit an Investigational New Drug (IND) application to the FDA along with an infectivity study in humanized FRG KO huHEP mice, and an immunogenicity and protective efficacy study in a mouse model with patent parasitemia as the protection outcome. The product resulting from studies outlined in this proposal will be called Sanaria® PvSPZ Challenge, and similar to PfSPZ Challenge will provide the larger malaria community with a tool to assess the efficacy of drugs and vaccines against Pv malaria with a safer quality-controlled reagent that exhibits minimal variability in potency between different lots, is logistically more feasible to administer, and is not subject to geographical limitations for application, compared to traditional CHMI using mosquito bites. It will represent an unprecedented milestone in the field of vaccinology, and vaccine manufacturing and most importantly it will form the basis of a powerful vaccine approach to preventing Pv malaria when administered with anti-malarial chemoprophylaxis, the PvSPZ chemoprophylaxis vaccine (PvSPZ-CVac).