Experimental infection and protection against ... - TI Pharma

Protection against a Malaria Challenge by Sporozoite Inoculation 177
the Radboud University Nijmegen Medical Centre (CMO 2006/207).
Clinicaltrials.gov identifier: NCT00442377.
Protocol
Volunteers were randomized double blind into two groups (Figure 1), 10 vera
and 5 controls. Chloroquine(CQ) was provided to all volunteers in a standard
prophylactic regimen of 300mg base weekly, starting with 600mg in two days,
for a total duration of 13 weeks. Whilst under CQ prophylaxis, vera were
exposed on three occasions, at four-weekly intervals, to bites of 12-15 P.
falciparum-infected mosquitoes per session, for a total exposure of 36-45
infected mosquitoes per volunteer. Controls received bites from an equal
number of uninfected mosquitoes on the same occasions. Anopheles stephensi
mosquitoes were reared according to standard procedures at our insectary.
Infected mosquitoes were obtained by feeding on gametocytes of NF54, a
chloroquine sensitive strain of P. falciparum, as described previously [13]. NF54
is genetically homogeneous, but has not been formally cloned. Only the
insectary technicians preparing the mosquitoes were aware of the infectivity
status of the mosquitoes allocated to the volunteers. Blood-engorged
mosquitoes were dissected to confirm the presence of sporozoites. If necessary,
feeding sessions were repeated until precisely the predefined number of
infected mosquitoes had fed. However, a single feeding session was sufficient in
49/60 of all instances of immunization or challenge, whereas a second session
was required in just 10 instances and a third session in only 1 instance.
From day 6-10 after each mosquito exposure, all volunteers were followed on an
outpatient basis and blood was drawn for standard whole blood counts and daily
thick smears. Any signs and symptoms were recorded by the attending physician
as follows: mild (easily tolerated), moderate (interferes with normal activity), or
severe (prevents normal activity).
Eight weeks after the last immunization dose and 4 weeks after discontinuation
of CQ prophylaxis, all 15 volunteers were challenged by exposure to the bites of
five homologous NF54 strain P. falciparum-infected mosquitoes. This period was
considered to be sufficient for CQ levels to drop below levels which might be
inhibitory to parasite multiplication [14]. Volunteers were checked daily on an
outpatient basis from day 5 to day 21 for symptoms and signs of malaria,
haematological parameters and thick smears.
As soon as thick smear positive, volunteers were treated with a standard
curative regimen of artemether/lumefantrine (starting dose of 80/480 mg,