Experimental infection and protection against ... - TI Pharma

Induction of malaria in volunteers by intradermal injection of cryopreserved
Plasmodium falciparum sporozoites
Figure 1. Liver-stage Pf parasite expressing PfMSP-1 after six days in culture. PfSPZ
from the lot of PfSPZ Challenge used in this clinical trial were used to infect a human
hepatocyte line in vitro (see Table S1 for methods). Six days later the parasites were
stained with an antibody to PfMSP-1. PfMSP-1 is the major protein on the surface of
merozoites, and is required for merozoite invasion of erythrocytes. It is only
expressed in mature liver stage parasites and blood stage parasites, and is required
for the survival of blood stage parasites. Potency of lots of PfSPZ Challenge is
assessed by expression of PfMSP-1 in vitro (see Table S1). Image captured with a
Zeiss LSM510 META laser scanning confocal microscope.
Study treatment (PfSPZ Challenge)
PfSPZ Challenge contains aseptic, purified, cryopreserved PfSPZ isolated from
salivary glands of aseptically reared mosquitoes [28]. A. stephensi mosquitoes
were raised under aseptic conditions, then fed on cultured Stage V gametocytes
of the NF54 strain of Pf [38]. Approximately two weeks later, mosquito salivary
glands containing PfSPZ were dissected, and PfSPZ were purified, formulated,
vialed (15,000 PfSPZ per vial) and cryopreserved in liquid nitrogen vapour phase
at -140°C to -196°C [28]. PfSPZ Challenge released for clinical use met quality
control specifications including sterility (USP 71 compendial assay), purity (Fig.
S1), and potency (Table S1). The latter was assessed by quantification of late
liver stage parasites expressing Pf merozoite surface protein 1 (PfMSP-1) [39] in
cultured human hepatocytes (HC-04 cells) six days after addition of PfSPZ (Figure
1, Table S1). Membrane integrity of PfSPZ was used to assess cell viability (Table
155