Ludthawun Kamuthachad,1,2 Pornrith Pisuttimarn,3 Thitinan Kasetthat,1,2 Ploenchan Chetchotisakd,4 Siriluck Anunnatsiri,4 Rasana W. Sermswan,2,5 Hiroshi Watarai,6 Ponpan Matangkasombut,7,8 Surasakdi Wongratanacheewin1,2

1 Department of Microbiology, Faculty of Medicine, Khon Kaen University, Thailand
2 Melioidosis Research Center, Khon Kaen University, Thailand
3 Khon Kaen Hospital, Khon Kaen, Thailand
4 Department of Medicine, Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Thailand
5 Department of Biochemistry, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
6 Department of Immunology and Stem Cell Biology, Faculty of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan
7 Department of Microbiology, Faculty of Science, Mahidol University, Bangkok, Thailand
8 Systems Biology of Diseases Research Unit, Faculty of Science, Mahidol University, Bangkok, Thailand

Abstract

Background: Melioidosis is an infectious disease caused by Burkholderia pseudomallei. In infected mice, IFN-γ can provide protection against B. pseudomallei infection. Invariant Natural Killer T (iNKT) cells are a subpopulation of T lymphocytes, activated by recognition of glycolipid ligands such as α-Galactosylceramide presented by CD1d, produce and secrete several cytokines, including IFN-γ and IL-4. The response of iNKT cells in human melioidosis was then investigated.
Objectives: To determine the iNKT cells response in human melioidosis.
Methods: The number of human iNKT cells and its activation states were investigated in sepsis melioidosis patients compared with healthy controls using flow cytometry. The iNKT cells activation was confirmed in vitro using heat-killed B. pseudomallei with normal peripheral blood mononuclear cells. The components induced iNKT cell were also determined using different concentration of B. pseudomallei lipopolysaccharide (LPS), heat-killed B. pseudomallei treated with or without DNase, RNase, or proteinase.
Results: The number of human iNKT cells was significantly lower while the percentage of activated iNKT cells was higher in sepsis melioidosis when compared to control. In addition, B. pseudomallei can stimulate human iNKT cells in vitro. Heat-killed B. pseudomallei could activate iNKT cells but not relate to nucleic acid, proteins, or LPS.
Conclusions: We found for the first time that the iNKT cells were activated during B. pseudomallei infection in human. However, the roles and the mechanism of iNKT cells during early state of infection needed to be further investigated.
Key words: Burkholderia pseudomallei, melioidosis, iNKT cells, activation, human infection