title: Pretreatment with recombinant Flt3 ligand partially protects against progressive cutaneous leishmaniasis in susceptible BALB/c mice.
abstract: Dendritic cells are potent antigen-presenting cells that also produce interleukin-12 (IL-12) during innate and adaptive cellular immune responses and that thereby promote the differentiation of gamma interferon (IFN-gamma)-producing Th1-type CD4(+) T lymphocytes. We hypothesized that expanded dendritic-cell populations in mice pretreated with the hematopoietic cytokine Flt3L would protect against cutaneous Leishmania major infection. Pretreatment of disease-susceptible BALB/c mice with 10 microg of recombinant Flt3L (rFlt3L) for 9 to 10 days before infection increased lymph node IL-12 p40 productive capacity 20-fold compared to that of saline-injected controls. Furthermore, 9 of 22 (40.9%) rFlt3L-pretreated BALB/c mice resolved their cutaneous infections, whereas none of the 22 control BALB/c mice healed. Healed, rFlt3L-pretreated mice did not develop disease following reinfection. Flt3L pretreatment also reduced parasite numbers 1,000-fold in the cutaneous lesions at 2 weeks after infection relative to numbers in lesions of untreated controls. However, Flt3L pretreatment did not significantly alter L. major-induced IFN-gamma and IL-4 production in lymph node culture at 1, 2, and 4 weeks after infection. Despite the lack of Th immune deviation, Flt3L ligand-pretreated lymph nodes expressed up to 10-fold higher levels of IL-12 p40 and inducible (type 2) nitric oxide synthase mRNA at 7 days after infection. In contrast, treatment with rFlt3L after infection failed to protect against disease despite comparable expansions of dendritic cells and IL-12 p40 productive capacity in both infected and uninfected BALB/c mice treated with rFlt3L. We conclude that rFlt3L pretreatment before infection with L. major reduces parasite load and promotes healing of cutaneous lesions without stable cytokine deviation towards a dominant Th1 cytokine phenotype.
authors.affiliation: Department of Dermatology, University Hospitals of Cleveland, Cleveland, Ohio 44106, USA.
authors.forename: I B
authors.initials: IB
authors.lastname: Kremer
authors.forename: M P
authors.initials: MP
authors.lastname: Gould
authors.forename: K D
authors.initials: KD
authors.lastname: Cooper
authors.forename: F P
authors.initials: FP
authors.lastname: Heinzel
mesh_terms: D000818:Animals; D019013:CD40 Antigens / Q000502:physiology; D004198:Disease Susceptibility; D005260:Female; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000096:biosynthesis; D016773:Leishmaniasis, Cutaneous / Q000469:parasitology / Q000517:prevention & control*; D008198:Lymph Nodes / Q000276:immunology; D008565:Membrane Proteins / Q000627:therapeutic use*; D051379:Mice; D008807:Mice, Inbred BALB C; D019001:Nitric Oxide Synthase / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000627:therapeutic use
chemical_list: D019013:CD40 Antigens; D008565:Membrane Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; C084881:flt3 ligand protein; D018664:Interleukin-12; D015847:Interleukin-4; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse