title: Leishmania donovani: impairment of the cellular immune response against recombinant ornithine decarboxylase protein as a possible evasion strategy of Leishmania in visceral leishmaniasis.
abstract: Ornithine decarboxylase, the rate limiting enzyme of the polyamine biosynthesis pathway, is significant in the synthesis of trypanothione, T(SH)2, the major reduced thiol which is responsible for the modulation of the immune response and pathogenesis in visceral leishmaniasis. Data on the relationship between ornithine decarboxylase and the cellular immune response in VL patients are limited. Therefore, we purified a recombinant ornithine decarboxylase from Leishmania donovani (r-LdODC) of approximately 77kDa and examined its effects on the immunological responses in peripheral blood mononuclear cells of human visceral leishmaniasis cases. For these studies, α-difluoromethylornithine was tested as an inhibitor and was used in parallel in all experiments. The r-LdODC was identified as having a direct correlation with parasite growth and significantly increased the number of promastigotes as well as axenic amastigotes after 96h of culture. The stimulation of peripheral blood mononuclear cells with r-LdODC up-regulated IL-10 production but not IFN-γ production from CD4(+) T cells in active as well as cured visceral leishmaniasis cases, indicating a pivotal role for r-LdODC in causing strong immune suppression in a susceptible host. In addition, severe hindrance of the immune response and anti-leishmanial macrophage function due to r-LdODC, as revealed by decreased IL-12 and nitric oxide production, and down-regulation in mean fluorescence intensities of reactive oxygen species, occurred in visceral leishmaniasis patients. There was little impact of r-LdODC in the killing of L. donovani amastigotes in macrophages of visceral leishmaniasis patients. In contrast, when cultures of promastigotes and amastigotes, and patients' blood samples, were directed against α-difluoromethylornithine, parasite numbers significantly reduced in culture, whereas the levels of IFN-γ and IL-12, and the production of reactive oxygen species and nitric oxide, were significantly elevated. Therefore, we demonstrated cross-talk with the use of α-difluoromethylornithine which can reduce the activity of ornithine decarboxylase of L. donovani, eliminating the parasite-induced immune suppression and inducing collateral host protective responses in visceral leishmaniasis.
authors.affiliation: Division of Immunology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Anupam
authors.initials: A
authors.lastname: Yadav
authors.affiliation: Division of Immunology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Ajay
authors.initials: A
authors.lastname: Amit
authors.affiliation: Division of Immunology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Chaudhary
authors.affiliation: Dept. of Biotechnology, National Institute of Pharmaceutical Education and Research, Hajipur 844102, India.
authors.forename: Arvind Singh
authors.initials: AS
authors.lastname: Chandel
authors.affiliation: Dept. of Biotechnology, National Institute of Pharmaceutical Education and Research, Hajipur 844102, India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Mahantesh
authors.affiliation: Laboratory of Molecular Biochemistry and Cell Biology, Department of Biochemistry, Rajendra Memorial Research Institute of Medical Sciences, Agamkuan, Patna 800007, India.
authors.forename: Shashi Shekhar
authors.initials: SS
authors.lastname: Suman
authors.affiliation: Division of Microbiology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Subhankar Kumar
authors.initials: SK
authors.lastname: Singh
authors.affiliation: Division of Immunology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India; Dept. of Biomedical Informatics, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Manas Ranjan
authors.initials: MR
authors.lastname: Dikhit
authors.affiliation: Laboratory of Molecular Biochemistry and Cell Biology, Department of Biochemistry, Rajendra Memorial Research Institute of Medical Sciences, Agamkuan, Patna 800007, India.
authors.forename: Vahab
authors.initials: V
authors.lastname: Ali
authors.affiliation: Dept. of Clinical Medicine, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Vidyanand
authors.initials: V
authors.lastname: Rabidas
authors.affiliation: Dept. of Clinical Medicine, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Krishna
authors.initials: K
authors.lastname: Pandey
authors.affiliation: Animal House, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Dept. of Molecular Biology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Das
authors.affiliation: Division of Immunology, Rajendra Memorial Research Institute of Medical Sciences, Patna 800007, India. Electronic address: drsbimal24@yahoo.com.
authors.forename: Sanjiva
authors.initials: S
authors.lastname: Bimal
mesh_terms: D000293:Adolescent; D000328:Adult; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006801:Humans; D057131:Immune Evasion; D007108:Immune Tolerance; D007111:Immunity, Cellular; D007893:Leishmania donovani / Q000276:immunology* / Q000502:physiology*; D007898:Leishmaniasis, Visceral / Q000276:immunology* / Q000469:parasitology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D009955:Ornithine Decarboxylase / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D055815:Young Adult
chemical_list: D016207:Cytokines; D011994:Recombinant Proteins; D037521:Virulence Factors; D009569:Nitric Oxide; D009955:Ornithine Decarboxylase
keywords: IFN-γ; IL-10; Leishmania donovani; ODC; ROS; Visceral leishmaniasis