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Summary Leishmania parasites are the causative agents of leishmaniasis, a neglected tropical disease that causes substantial morbidity and considerable mortality in many developing areas of the world. Recent estimates suggest that roughly 10 million people suffer from cutaneous leishmaniasis (CL), and approximately 76 000 are afflicted with visceral leishmaniasis (VL), which is universally fatal without treatment. Efforts to develop therapeutics and vaccines have been greatly hampered by an incomplete understanding of the parasite's biology and a lack of clear protective correlates that must be met in order to achieve immunity. Although parasites grow and divide preferentially in macrophages, a number of other cell types interact with and internalize Leishmania parasites, including monocytes, dendritic cells and neutrophils. Neutrophils appear to be especially important shortly after parasites are introduced into the skin, and may serve a dual protective and permissive role during the establishment of infection. Curiously, neutrophil recruitment to the site of infection appears to continue into the chronic phase of disease, which may persist for many years. The immunological impact of these cells during chronic leishmaniasis is unclear at this time. In this review we discuss the ways in which neutrophils have been observed to prevent and promote the establishment of infection, examine the role of anti-neutrophil antibodies in mouse models of leishmaniasis and consider recent findings that neutrophils may play a previously unrecognized role in influencing chronic parasite persistence.

The low expression of iNOS in hamsters is related to a region of the proximal promoter that lacks an NF-IL6 binding element. IFN-γ/LPS-activated hamster (Mesocricetus auratus) macrophages express significantly less iNOS (NOS2) than activated mouse macrophages, which contributes to the hamsterˈs susceptibility to intracellular pathogens. We determined a mechanism responsible for differences in iNOS promoter activity in hamsters and mice. The HtPP (1.2 kb) showed low basal and inducible promoter activity when compared with the mouse, and sequences within a 100-bp region (−233 to −133) of the mouse and hamster promoters influenced this activity. Moreover, within this 100 bp, we identified a smaller region (44 bp) in the mouse promoter, which recovered basal promoter activity when swapped into the hamster promoter. The mouse homolog (100-bp region) contained a cis-element for NF-IL-6 (−153/−142), which was absent in the hamster counterpart. EMSA and supershift assays revealed that the hamster sequence did not support the binding of NF-IL-6. Introduction of a functional NF-IL-6 binding sequence into the hamster promoter or its alteration in the mouse promoter revealed the critical importance of this transcription factor for full iNOS promoter activity. Furthermore, the binding of NF-IL-6 to the iNOS promoter (−153/−142) in vivo was increased in mouse cells but was reduced in hamster cells after IFN-γ/LPS stimulation. Differences in the activity of the iNOS promoters were evident in mouse and hamster cells, so they were not merely a result of species-specific differences in transcription factors. Thus, we have identified unique DNA sequences and a critical transcription factor, NF-IL-6, which contribute to the overall basal and inducible expression of hamster iNOS.

The maintenance of host defense dur- ing pregnancy may depend on heightened innate immunity. We evaluated the immune response of pregnant hamsters during early infection with Leishmania (Viannia) panamensis, a cause of American cutaneous leishmaniasis. At 7 days post-infection, pregnant animals showed a lower parasite burden compared with nonpregnant controls at the cutaneous infection site (P 0.0098) and draining lymph node (P0.02). Resident peritoneal macrophages and neutro- phils from pregnant animals had enhanced Leish- mania killing capacity compared with nonpreg- nant controls (P0.018 each). This enhanced resistance during pregnancy was associated with increased expression of inducible NO synthase (iNOS) mRNA in lymph node cells (P0.02) and higher NO production by neutrophils (P 0.0001). Macrophages from nonpregnant ham- sters infected with L. panamensis released high amounts of NO upon estrogen exposure (P0.05), and addition of the iNOS inhibitor L-N6-(1-iminoethyl) lysine blocked the induction of NO production (P0.02). Infected, nonpreg- nant females treated with estrogen showed a higher percentage of cells producing NO at the infection site than controls (P0.001), which correlated with lower parasite burdens (P 0.036). Cultured macrophages or neutrophils from estrogen-treated hamsters showed signifi- cantly increased NO production and Leishmania killing compared with untreated controls. iNOS was identified as the likely source of estrogen- induced NO in primed and naive macrophages, as increased transcription was evident by real- time PCR. Thus, the innate defense against Leishmania infection is heightened during preg- nancy, at least in part as a result of estrogen- mediated up-regulation of iNOS expression and NO production. J. Leukoc. Biol. 83: 1413-1422; 2008.

SUMMARYWe have previously demonstrated induction and high level expression of IL-1β, IL-6 and tumour necrosis factor-alpha in the myocardium during the acute stage of experimental Trypanosoma cruzi infection (Chagas' disease). The myocardial depressive effects of these cytokines are mediated in part by the induction of nitric oxide synthase (NOS), production of nitric oxide (NO) and formation of peroxynitrite. In this study we investigated the expression, activity and localization of NOS isoforms, and the levels of NO, malondialdehyde (a measure of oxidative stress), and peroxynitrite in rats at 1·5, 5, 10 and 15 days after infection with T. cruzi trypomastigotes. The myocardial inflammatory infiltrate and number of amastigote nests increased over the course of infection. A significant increase in tissue nitrate + nitrite levels, NOS2 mRNA, and NOS2 enzyme activity was observed at all time points in the infected compared with uninfected animals. The enzyme activity of constitutive NOS, tissue malondialdehyde levels, and NOS3 mRNA levels was only transiently increased after infection. The protein levels of the NOS isoforms paralleled their mRNA expression. While no positive nitrotyrosine immunoreactivity was detected in control myocardium, its levels increased in infected animals over time. Thus, by 1·5 days post-infection, when no parasite or immune cell infiltration could be detected, the myocardium expressed high levels of NOS and NO metabolites. Nevertheless, the early production of NO in the myocardium was not sufficient to clear the parasites.

Localized cutaneous leishmaniasis caused by Leishmania major is polymorphic in its clinical presentation and evolution. Clinical and parasitologic features and disease evolution of 112 Tunisian patients was evaluated. The expression of interleukin (IL)-4, IL-6, IL-10, IL-12 (p40), interferon (IFN)-g, and tumor necrosis factor (TNF)-a mRNA was analyzed by reverse transcription ‐ polymerase chain reaction in 73 biopsies. Cytokine mRNA expression varied individually over a wide range; TNF-a, IL-6, and IFN-g were detectable in u90% of lesions, IL-12 and IL-10 in 40% and 70%, respectively, and IL-4 in only 9%. Statistical analysis demonstrated positive association between the level of IL-12 and IFN-g and the presence of parasites in the lesions. Unfavorable evolution of the lesions was positively associated with high IL-10, IL-12, and IFN-g mRNA expression. These results indicate that an unfavorable clinical outcome was not related to an inadequate Th1 cell response and suggest that the macrophage-activating effect of IFN-g may be inhibited by the concomitant expression of IL-10. Human leishmaniasis includes a spectrum of diseases of [3]. In the murine model of leishmaniasis caused by L. major, variable severity, ranging from cutaneous ulcer to a fatal vis- a clear-cut dichotomy between the two functional T helper ceral disease caused by intracellular protozoan parasites of the subsets, Th1 and Th2, has been observed [4]. Th1 cells, which genus Leishmania. Localized cutaneous leishmaniasis (LCL), produce interferon (IFN)-g and interleukin (IL)-2, mediate procaused by Leishmania major, is an endemic zoonosis in North tection in resistant mouse strains (e.g., C57Bl/6), and Th2 cells, Africa and the Middle East [1]. Although often benign and which produce IL-4 and IL-10, promote disease progression in self-healing, LCL is a major public health problem in rural susceptible strains (e.g., BALB/c) [5 ‐ 7]. These cytokines exert areas, where it may cause considerable morbidity. In Tunisia, a potent cross-regulatory activity on the other Th subset. TNFtransmission of L. major by the Phlebotomine sand fly vector a has also been demonstrated to play a protective role in the occurs during the summer months, and active lesions in humans murine model of L. major infection [8, 9], whereas another tend to emerge during the autumn and winter months [2]. The macrophage product, transforming growth factor (TGF)-b ,i s disease is polymorphic in its clinical presentation and evolu- counterprotective [10]. IL-12, produced by B cells, dendritic tion, which may be due to variability in parasite virulence or cells, and macrophages, has been shown to play a major role in the host genetic background and immune response. in the early establishment of Th1-dependent protective immu

Fifty-nine cases of cutaneous leishmaniasis seen at the National Institutes of Health in Bethesda, Maryland, are reviewed. The group of patients involved was unique in that the majority were American civilians, their disease was acquired in many different endemic areas of the world, and their illnesses represented all points on the clinical spectrum of cutaneous disease. The majority of American patients acquired leishmaniasis while engaging in activities related to their occupations. Cutaneous disease acquired in the New World usually consisted of one or two lesions, while multiple lesions often characterized Old World infections with Leishmania major. Patients with chronic relapsing or diffuse cutaneous leishmaniasis were native to endemic areas and were infected at an early age. Even the localized form of cutaneous leishmaniasis was often extensive and difficult to treat. Diagnosis with culture and identification of the parasite to the subspecies level is instrumental in the selection of optimal therapy. Cutaneous leishmaniasis may be encountered increasingly often in the United States because of the frequent international travel of U.S. residents and the influx of immigrants from endemic areas of the world.