Transcriptional profiling defines dynamics of parasite tissue sequestration during malaria infection.
BACKGROUND
During intra-erythrocytic development, late asexually replicating Plasmodium falciparum parasites sequester from peripheral circulation. This facilitates chronic infection and is linked to severe disease and organ-specific pathology including cerebral and placental malaria. Immature gametocytes - sexual stage precursor cells - likewise disappear from circulation. Recent work has demonstrated that these sexual stage parasites are located in the hematopoietic system of the bone marrow before mature gametocytes are released into the bloodstream to facilitate mosquito transmission. However, as sequestration occurs only in vivo and not during in vitro culture, the mechanisms by which it is regulated and enacted (particularly by the gametocyte stage) remain poorly understood.


RESULTS
We generated the most comprehensive P. falciparum functional gene network to date by integrating global transcriptional data from a large set of asexual and sexual in vitro samples, patient-derived in vivo samples, and a new set of in vitro samples profiling sexual commitment. We defined more than 250 functional modules (clusters) of genes that are co-expressed primarily during the intra-erythrocytic parasite cycle, including 35 during sexual commitment and gametocyte development. Comparing the in vivo and in vitro datasets allowed us, for the first time, to map the time point of asexual parasite sequestration in patients to 22 hours post-invasion, confirming previous in vitro observations on the dynamics of host cell modification and cytoadherence. Moreover, we were able to define the properties of gametocyte sequestration, demonstrating the presence of two circulating gametocyte populations: gametocyte rings between 0 and approximately 30 hours post-invasion and mature gametocytes after around 7 days post-invasion.


CONCLUSIONS
This study provides a bioinformatics resource for the functional elucidation of parasite life cycle dynamics and specifically demonstrates the presence of the gametocyte ring stages in circulation, adding significantly to our understanding of the dynamics of gametocyte sequestration in vivo.
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA.
Karell G
KG
Pelle
Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115 USA.
Keunyoung
K
Oh
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA.
Kathrin
K
Buchholz
Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115 USA.
Vagheesh
V
Narasimhan
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA.
Regina
R
Joice
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA ; Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115 USA.
Danny A
DA
Milner
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA ; Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland.
Nicolas Mb
NM
Brancucci
Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115 USA.
Siyuan
S
Ma
Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland.
Till S
TS
Voss
Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115 USA.
Ken
K
Ketman
College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48825 USA ; Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, 3 Malawi.
Karl B
KB
Seydel
College of Osteopathic Medicine, Michigan State University, East Lansing, MI 48825 USA ; Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, 3 Malawi.
Terrie E
TE
Taylor
Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA 02115 USA ; Department of Pediatrics, Harvard Medical School, Boston, MA 02115 USA.
Natasha S
NS
Barteneva
Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115 USA ; The Broad Institute of Harvard and MIT, Cambridge, MA 02142 USA.
Curtis
C
Huttenhower
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115 USA.
Matthias
M
Marti