1. Malaria Research in the Real World
Sarah Kaslow

2. Malaria: A Brief Introduction
Life-threatening disease caused by a parasite, transmitted by bites of infected mosquitoes
In 2010, malaria caused an estimated 655,000 deaths (mostly among Sub-Saharan African children).
Several species infect humans:
Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, Plasmodium knowlesi
Malaria is preventable and curable.
Complex life cycle complicates eradication/control efforts.

3. The Malaria Life Cycle is Complicated
Haploid
Blood
stream
Meiosis
Midgut
Salivary
Glands
Dormant liver stage (hypnozoites) causes disease relapses
Liver C
JHSPH

4. vivax and falciparum Are Different
Relapses of disease - hypnozoites
Highest morbidity
70 – 300 million people annually (most under age of 5)
No in vitro culture method
1st line Treatment: Chloroquine/Artemisinin Combination + Primaquine
Baird K, 2009
Broad range of clinical outcome despite relatively low parasitemia

5. Chloroquine
4-aminoquinoline drug used in the treatment/prevention of malaria
The antimalarial treatment of choice since 1950s.
Inexpensive, widely available
Low toxicity
Standard pediatric dose is 25 mg/kg over three days.
Half-life of ~42 days.

6. Mutations in pfcrt and CQR in P. falciparum
Resistance first reported in the 1950s; since spread through Asia and into Africa
K76T mutation of PfCRT connected to chloroquine resistance
Ortholog gene in P. vivax is pvcrt-o; no mutations associated to CQR
Marker has enabled typing of parasites from endemic areas
Distribution of PfCRT K76T Mutation
K: CQS
T: CQR
Adapted from Sá et al, 2011
PfCRT is a transmembrane protein found in the digestive vacuole of the parasite
A genetic marker has enabled typing of the pfcrt gene. With a genetic marker we can map the distribution of resistance, come up with resistance containment strategies, and alter treatment policies.
Genetic mapping is a public health tool.

7. Molecular Mechanism of CQR in P. vivax is Unknown
CQ Resistance (CQR) in P. vivax was first reported in 1989 and has spread from the South Pacific Islands.
Molecular mechanism and genetic basis of CQR in P. vivax remains unknown.
Baird K, 2009

8. Hypotheses and Experimental Approach
CQR is an inheritable trait
Generate a genetic cross between a CQ-R and a CQ-S parasite
CQ selects mutations in genes involved in its transport or mode of action
Search for a common genetic marker in CQ-R progeny

9. Approach: Genetic Cross
Drug Sensitive
Drug Resistant
Chimpanzee
CQ-S x CQ-R
Recombinant Oocysts
Cryopreserved Recombinant Sporozoites
Drug pressure
CQ-R Progeny
Mosquitoes
Multiple Aotus
Cure
Aotus
Recombinant Progeny
Map Genetic Determinants:
Linkage Group Selection
(LGS)

10. Approach: Linkage Group Selection
Sensitive Parasite
Resistant Parasite
Recombinant Progeny
Selection Pressure
Two haploid parasites that differ in their sensitivity to a particular selection pressure are genetically crossed. In this example, resistance to the selection pressure is conferred by a gene at the brown square.
The resulting recombinant progeny population will consist of thousands of parasites.
This uncloned population is then subjected to selection pressure, and the resulting selected population will consist solely of parasites that possess the resistant allele of the gene that controls the phenotype of interest.
We look for markers of the sensitive parent that are removed or reduced by the selection pressure; the greater the reduction in the intensity of a sensitive marker, the closer it is linked to the allele removed by the selection pressure.
Culleton et al. 2005

11. My Path Claremont McKenna College Philosophy, Politics, and Economics
University of Maryland
School of Medicine
Johns Hopkins University
Post-Baccalaureate Pre-Medical
Johns Hopkins Bloomberg School of Public Health
Masters in Public Health
Laboratory of Malaria and Vector Research
#ILookLikeASurgeon