Replication of Plasmodium in reticulocytes can occur without hemozoin formation, resulting in chloroquine resistance.
Most studies on malaria-parasite digestion of hemoglobin (Hb) have been performed using P. falciparum maintained in mature erythrocytes, in vitro. In this study, we examine Plasmodium Hb degradation in vivo in mice, using the parasite P. berghei, and show that it is possible to create mutant parasites lacking enzymes involved in the initial steps of Hb proteolysis. These mutants only complete development in reticulocytes and mature into both schizonts and gametocytes. Hb degradation is severely impaired and large amounts of undigested Hb remains in the reticulocyte cytoplasm and in vesicles in the parasite. The mutants produce little or no hemozoin (Hz), the detoxification by-product of Hb degradation. Further, they are resistant to chloroquine, an antimalarial drug that interferes with Hz formation, but their sensitivity to artesunate, also thought to be dependent on Hb degradation, is retained. Survival in reticulocytes with reduced or absent Hb digestion may imply a novel mechanism of drug resistance. These findings have implications for drug development against human-malaria parasites, such as P. vivax and P. ovale, which develop inside reticulocytes.
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK.
Jing-Wen
JW
Lin
Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy.
Roberta
R
Spaccapelo
Department of Oncology, University of Torino, 10124 Torino, Italy.
Evelin
E
Schwarzer
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Mohammed
M
Sajid
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Takeshi
T
Annoura
Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000 Leuven, Belgium.
Katrien
K
Deroost
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Raimond B G
RB
Ravelli
Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy.
Elena
E
Aime
Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK.
Barbara
B
Capuccini
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Anna M
AM
Mommaas-Kienhuis
Department of Molecular Cell Biology and Immunology, Vrije University Medical Center, 1007 MB Amsterdam, Netherlands.
Tom
T
O'Toole
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Frans
F
Prins
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Blandine M D
BM
Franke-Fayard
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Jai
J
Ramesar
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Séverine
S
Chevalley-Maurel
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Hans
H
Kroeze
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Abraham J
AJ
Koster
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Hans J
HJ
Tanke
Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy Department of Biological Sciences, Imperial College London, South Kensington Campus, SAF, London SW7 2AZ, England, UK.
Andrea
A
Crisanti
Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK.
Jean
J
Langhorne
Department of Oncology, University of Torino, 10124 Torino, Italy.
Paolo
P
Arese
Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000 Leuven, Belgium.
Philippe E
PE
Van den Steen
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands.
Chris J
CJ
Janse
Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands s.m.khan@lumc.nl.
Shahid M
SM
Khan
D000818:Animals; D000962:Antimalarials / Q000737:chemistry*; D037621:Artemisinins / Q000737:chemistry; D000077332:Artesunate; D002738:Chloroquine / Q000737:chemistry*; D003593:Cytoplasm / Q000378:metabolism; D004351:Drug Resistance; D004912:Erythrocytes / Q000469:parasitology*; D005260:Female; D017353:Gene Deletion; D017930:Genes, Reporter; D006420:Hemeproteins / Q000737:chemistry*; D006454:Hemoglobins / Q000378:metabolism*; D008288:Malaria / Q000469:parasitology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D010962:Plasmodium berghei / Q000166:cytology*; D012156:Reticulocytes / Q000378:metabolism / Q000469:parasitology*
D000962:Antimalarials; D037621:Artemisinins; D006420:Hemeproteins; D006454:Hemoglobins; C020753:hemozoin; D000077332:Artesunate; D002738:Chloroquine