Characterization of blood dendritic and regulatory T cells in asymptomatic adults with sub-microscopic Plasmodium falciparum or Plasmodium vivax infection.
Plasmodium falciparum and Plasmodium vivax infections compromise dendritic cell (DC) function and expand regulatory T (Treg) cells in both clinical disease (malaria) and experimental human sub-microscopic infection. Conversely, in asymptomatic microscopy-positive (patent) P. falciparum or P. vivax infection in endemic areas, blood DC increase or retain HLA-DR expression and Treg cells exhibit reduced activation, suggesting that DC and Treg cells contribute to the control of patent asymptomatic infection. The effect of sub-microscopic (sub-patent) asymptomatic Plasmodium infection on DC and Treg cells in malaria-endemic area residents remains unclear.



In a cross-sectional household survey conducted in Papua, Indonesia, 162 asymptomatic adults were prospectively evaluated for DC and Treg cells using field-based flow cytometry. Of these, 161 individuals (99 %) were assessed retrospectively by polymerase chain reaction (PCR), 19 of whom had sub-microscopic infection with P. falciparum and 15 with sub-microscopic P. vivax infection. Flow cytometric data were re-analysed after re-grouping asymptomatic individuals according to PCR results into negative controls, sub-microscopic and microscopic parasitaemia to examine DC and Treg cell phenotype in sub-microscopic infection.



Asymptomatic adults with sub-microscopic P. falciparum or P. vivax infection had DC HLA-DR expression and Treg cell activation comparable to PCR-negative controls. Sub-microscopic P. falciparum infection was associated with lower peripheral CD4(+) T cells and lymphocytes, however sub-microscopic Plasmodium infection had no apparent effect on DC sub-set number or Treg cell frequency.



In contrast to the impairment of DC maturation/function and the activation of Treg cells seen with sub-microscopic parasitaemia in primary experimental human Plasmodium infection, no phenotypic evidence of dysregulation of DC and Treg cells was observed in asymptomatic sub-microscopic Plasmodium infection in Indonesian adults. This is consistent with DC and Treg cells retaining their functional capacity in sub-microscopic asymptomatic infection with P. falciparum or P. vivax in malaria-endemic areas.
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia. steven.kho@menzies.edu.au.
Steven
S
Kho
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Jutta
J
Marfurt
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Irene
I
Handayuni
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Zuleima
Z
Pava
Eijkman Institute for Molecular Biology, Jakarta, Indonesia.
Rintis
R
Noviyanti
Eijkman Institute for Molecular Biology, Jakarta, Indonesia.
Andreas
A
Kusuma
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Kim A
KA
Piera
Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia.
Faustina H
FH
Burdam
Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia.|Rumah Sakit Umum Daerah Kabupaten Mimika, Timika, Papua, Indonesia.
Enny
E
Kenangalem
Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia.
Daniel A
DA
Lampah
QIMR Berghofer Medical Research Institute, Brisbane, Australia.
Christian R
CR
Engwerda
Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia.|Rumah Sakit Umum Daerah Kabupaten Mimika, Timika, Papua, Indonesia.|Department of Paediatrics, University of Gadjah Mada, Yogyakarta, Indonesia.
Jeanne R
JR
Poespoprodjo
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.|Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK.
Ric N
RN
Price
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Nicholas M
NM
Anstey
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Gabriela
G
Minigo
Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia.
Tonia
T
Woodberry
D000328:Adult; D058345:Asymptomatic Infections; D003430:Cross-Sectional Studies; D003713:Dendritic Cells / Q000276:immunology*; D005191:Family Characteristics; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007214:Indonesia; D016778:Malaria, Falciparum / Q000276:immunology*; D016780:Malaria, Vivax / Q000276:immunology*; D008297:Male; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D012189:Retrospective Studies; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D055815:Young Adult
Adults; Asymptomatic; Clinical immunity; Dendritic cell; Falciparum; Human; Malaria; Regulatory T cell; Sub-microscopic; Vivax