Skin-derived macrophages from Leishmania major-susceptible mice exhibit interleukin-12- and interferon-gamma-independent nitric oxide production and parasite killing after treatment with immunostimulatory DNA.
Co-administration of CpG-containing immunostimulatory oligodeoxynucleotides and parasite antigen protects susceptible BALB/c mice from otherwise progressive infection with Leishmania major. Although the protective effect of CpG-containing immunostimulatory oligodeoxynucleotides is clearly dependent on endogenous interleukin-12 and interferon-gamma production, the source of these Th1-promoting cytokines in infected mice is unknown. In contrast to macrophages from Leishmania-resistant C57BL/6 mice, macrophages from susceptible BALB/c mice are hyporesponsive to stimulation with lipopolysaccharide and interferon-gamma. While studying interactions of various antigen-presenting cells with Leishmania, we found that BALB/c inflammatory skin macrophages, whether Leishmania-infected or uninfected, produced large amounts of interleukin-12 when treated with CpG-containing immunostimulatory oligodeoxynucleotides. Like lipopolysaccharide, CpG-containing immunostimulatory oligodeoxynucleotides induced production of interferon-gamma and release of nitric oxide by skin macrophages. Studies using skin macrophages from interleukin-12- and interferon-gamma-deficient BALB/c mice demonstrated that nitric oxide release was not dependent on interleukin-12 and interferon-gamma production. Approximately 44% and 27% of intracellular Leishmania major amastigotes were killed by infected skin macrophages within 72 h upon stimulation with CpG-containing immunostimulatory oligodeoxynucleotides and lipopolysaccharide, respectively. Parasite killing by macrophages was independent of endogenous interferon-gamma production, but was strongly enhanced by exogenous interferon-gamma. Parasite elimination was dependent on the induction of nitric oxide, however. In vivo, injection of CpG-containing immunostimulatory oligodeoxynucleotides into lesional skin reduced the parasite burden approximately 50-fold within the first 5 d of infection prior to full generation of a Th response. These results suggest that skin macrophages, constituting the principal reservoir of parasites in infected susceptible mice, produce Th1-promoting cytokines in response to CpG-containing immunostimulatory oligodeoxynucleotides. In addition, CpG-containing immunostimulatory oligodeoxynucleotides may also act locally on skin macrophages to facilitate Leishmania clearance by inducing nitric oxide production.
von Stebut
Esther
E
Department of Dermatology, Johannes Gutenberg-University, Mainz, Germany. vonstebu@mail.uni-mainz.de
Belkaid
Yasmine
Y
Nguyen
Bai
B
Wilson
Mark
M
Sacks
David L
DL
Udey
Mark C
MC
D000818:Animals; D005260:Female; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D018320:Leishmania major / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology* / Q000628:therapy*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D009569:Nitric Oxide / Q000276:immunology / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000276:immunology / Q000494:pharmacology; D012867:Skin / Q000166:cytology / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology / Q000469:parasitology
D008070:Lipopolysaccharides; D009838:Oligodeoxyribonucleotides; D018664:Interleukin-12; D009569:Nitric Oxide; D007371:Interferon-gamma