Figure 1: Malaria transmission biology and the assays to identify compounds to block it MMV’s strategy is to identify compounds able to kill the asexual blood stages and gametocytes, thus curing the patient and blocking transmission. To do so, we have a cascade of tests in place. Blood-stage active compounds are screened against a gametocyte assay, followed by a male and female gamete formation assay followed by the Standard Membrane Feeding Assay (SMFA).
HUMAN BLOOD STAGE
MOSQUITO STAGE
9 DAYS
20 MINS
1H
12–36 H
9–12 DAYS
Oocysts
37-40°C
26°C
98.6-104°F
78.8°F
Ookinete Diploid zygote Micro-gamete Macro-gamete Sporozoites
STAGES OF GAMETOCYTES IMMATURE
1
2
MATURE
3
4
Wall of the midgut
5
Salivary glands Sporozoites
NUMBER OF PARASITES BY LIFECYCLE STAGE: ≈ 5,000 GAMETOCYTES IN A BLOOD MEAL
Ring
≈ 500 GAMETES ≈ 100 OOKINETES ≈ 5–10 OOCYSTS ≈ 103 SPOROZOITES Human blood vessel
Blood
Midgut
IN VITRO STUDY
Blood
DUAL MALE LE & FEM FEMALE GAMETE FORMATION ASSAY
STANDARD MEMBRANE FEEDING ASSAY
Gametocytes are
Late-stage gametocytes
Gametocytes in human
incubated with a
are incubated with a
blood are incubated
compound for
compound for 24–48
with a compound
24–48 hours and their
hours and their viability
for 24–48 hours.
viability assessed.
and fertility assessed.
Mosquitoes are fed on
(Oocyst Formation Assay)
the blood. Ten days
Illustration: Comstone
GAM GAMETOCYTE AM METO ETOCYT CYTE ASSAY ASS AY
later the mosquitoes are dissected to determine if there are oocyts present in their midgut.
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