Is the production of reactive oxygen and nitrogen species by macrophages associated with better infectious control in female mice with experimentally disseminated and pulmonary mucormycosis?

Different levels of resistance against Rhizopus oryzae infection have been observed between inbred (BALB/c) and outbred (Swiss) mice and are associated with the genetic background of each mouse strain. Considering that macrophages play an important role in host resistance to Rhizopus species, we used different infectious outcomes observed in experimental mucormycosis to identify the most efficient macrophage response pattern against R. oryzae in vitro and in vivo. For this, we compared BALB/c and Swiss macrophage activity before and after intravenous or intratracheal R. oryzae infections. The production of hydrogen peroxide (H2O2) and nitric oxide (NO) was determined in cultures of peritoneal (PMΦ) or alveolar macrophages (AMΦ) challenged with heat-killed spores of R. oryzae. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) were measured to confirm our findings. Naïve PMΦ from female BALB/c mice showed increased production of H2O2, TNF-α, and IL-10 in the presence of heat-killed spores of R. oryzae. Naïve PMΦ from female Swiss mice were less responsive. Naïve AMΦ from the two strains of female mice were less reactive to heat-killed spores of R. oryzae than PMΦ. After 30 days of R. oryzae intravenous infection, lower fungal load in spleen from BALB/c mice was accompanied by higher production of H2O2 by PMΦ compared with Swiss mice. In contrast, AMΦ from BALB/c mice showed higher production of NO, TNF-α, and IL-10 after 7 days of intratracheal infection. The collective findings reveal that, independent of the female mouse strain, PMΦ is more reactive against R. oryzae upon first contact than AMΦ. In addition, increased PMΦ production of H2O2 at the end of disseminated infection is accompanied by better fungal clearance in resistant (BALB/c) mice. Our findings further the understanding of the parasite-host relationship in mucormycosis.

TLR2-/- Mice Display Increased Clearance of Dermatophyte Trichophyton mentagrophytes in the Setting of Hyperglycemia.

Dermatophytosis is one of the most common human infections affecting both immunocompetent individuals and immunocompromised patients, in whom the disease is more aggressive and can reach deep tissues. Over the last decades, cases of deep dermatophytosis have increased and the dermatophyte-host interplay remains poorly investigated. Pattern recognition molecules, such as Toll-like receptors (TLR), play a crucial role against infectious diseases. However, there has been very little research reported on dermatophytosis. In the present study, we investigated the role of TLR2 during the development of experimental deep dermatophytosis in normal mice and mice with alloxan-induced diabetes mellitus, an experimental model of diabetes that exhibits a delay in the clearance of the dermatophyte, Trichophyton mentagrophytes (Tm). Our results demonstrated that inoculation of Tm into the footpads of normal mice increases the expression of TLR2 in CD115+Ly6Chigh blood monocytes and, in hypoinsulinemic-hyperglycemic (HH) mice infected with Tm, the increased expression of TLR2 was exacerbated. To understand the role of TLR2 during the development of murine experimental deep dermatophytosis, we employed TLR2 knockout mice. Tm-infected TLR2-/- and TLR2+/+ wild-type mice exhibited similar control of deep dermatophytic infection and macrophage activity; however, TLR2-/- mice showed a noteworthy increase in production of IFN-γ, IL-10, and IL-17, and an increased percentage of splenic CD25+Foxp3+ Treg cells. Interestingly, TLR2-/- HH-Tm mice exhibited a lower fungal load and superior organization of tissue inflammatory responses, with high levels of production of hydrogen peroxide by macrophages, alongside low TNF-α and IL-10; high production of IL-10 by spleen cells; and increased expansion of Tregs. In conclusion, we demonstrate that TLR2 diminishes the development of adaptive immune responses during experimental deep dermatophytosis and, in a diabetic scenario, acts to intensify a non-protective inflammatory response.

Imbalanced Macrophage and Dendritic Cell Activations in Response to Candida albicans in a Murine Model of Diabetes Mellitus.

Bloodstream infections caused by Candida species are responsible for high morbidity and mortality, and diabetes mellitus (DM) is an important underlying disease in candidemia episodes. Although DM patients show an enhanced proinflammatory profile, they are highly susceptible to mycobacterial and mycotic infections. Attempting to understand this paradox, we investigated if imbalanced macrophage and dendritic cell (DC) activations could be associated to high incidence and/or severity of Candida albicans infection in the hypoinsulinemia-hyperglycemia (HH) milieu. HH alloxan-induced mice were infected with C. albicans and peritoneal aderent phagocytes were co-cultured with or without lipopolyssaccharide or heat-killed C. albicans, and the production of cytotoxic metabolites, cytokines, and chemokines was evaluated. We also evaluated the surface expression of MHC-II and CD86 in splenic DCs. Our findings showed that both uninfected and C. albicans-infected HH mice showed less production of CCL2 and reduced expression of CD86 by peritoneal phagocytes and splenic DCs, respectively.

Relationship among Short and Long Term of Hypoinsulinemia-Hyperglycemia, Dermatophytosis, and Immunobiology of Mononuclear Phagocytes.

Dermatophytes are fungi responsible for causing superficial infections. In patients with diabetes mellitus (DM), dermatophytosis is usually more severe and recurrent. In the present study, we aimed to investigate the influence of short and long term hypoinsulinemia-hyperglycemia (HH) during experimental infection by Trichophyton mentagrophytes as well as alterations in the mononuclear phagocytes. Our results showed two distinct profiles of fungal outcome and immune response. Short term HH induced a discrete impaired proinflammatory response by peritoneal adherent cells (PAC) and a delayed fungal clearance. Moreover, long term HH mice showed low and persistent fungal load and a marked reduction in the production of TNF-α by PAC. Furthermore, while the inoculation of TM in non-HH mice triggered high influx of Gr1(+) monocytes into the peripheral blood, long term HH mice showed low percentage of these cells. Thus, our results demonstrate that the time of exposure of HH interferes with the TM infection outcome as well as the immunobiology of mononuclear phagocytes, including fresh monocyte recruitment from bone marrow and PAC activity.

Experimental autoimmune encephalomyelitis development is aggravated by Candida albicans infection.

Multiple sclerosis (MS) is an inflammatory/autoimmune disease of the central nervous system (CNS) mainly mediated by myelin specific T cells. It is widely believed that environmental factors, including fungal infections, contribute to disease induction or evolution. Even though Candida infection among MS patients has been described, the participation of this fungus in this pathology is not clear. The purpose of this work was to evaluate the effect of a Candida albicans infection on experimental autoimmune encephalomyelitis (EAE) that is a widely accepted model to study MS. Female C57BL/6 mice were infected with C. albicans and 3 days later, animals were submitted to EAE induction by immunization with myelin oligodendrocyte glycoprotein. Previous infection increased the clinical score and also the body weight loss. EAE aggravation was associated with expansion of peripheral CD4(+) T cells and production of high levels of TNF-α, IFN-γ IL-6, and IL-17 by spleen and CNS cells. In addition to yeast and hyphae, fungus specific T cells were found in the CNS. These findings suggest that C. albicans infection before EAE induction aggravates EAE, and possibly MS, mainly by CNS dissemination and local induction of encephalitogenic cytokines. Peripheral production of encephalitogenic cytokines could also contribute to disease aggravation.

Phenotypic and functional evaluations of peripheral blood monocytes from chronic-form paracoccidioidomycosis patients before and after treatment.

BACKGROUND: Paracoccidioidomycosis (PCM) is systemic mycosis caused by the thermal dimorphic fungus of genus Paracoccidioides, leading to either acute/subacute (AF) or chronic (CF) clinical forms. Numerous CF patients after treatment exhibit sequels, such as pulmonary and adrenal fibrosis. Monocytes are cells that are involved in the inflammatory response during active infection as well as in the fibrogenesis. These cells comprise a heterogeneous population with distinct phenotypic and functional activities. The scope of this study was to identify changes regarding functional and phenotypical aspects in monocytes comparing CF PCM patients on antifungal treatment versus non-treated patients (PMC-p). METHODS: Twenty-three CF PCM composed of 11 non-treated patients (NTG) and 12 patients in apparent cure (ACG) were studied. Sixteen healthy individuals were used as control group (CG). Monocyte subsets were determined by immunophenotyping based on CD14 and CD16 expression. Cellular function was measured in vitro with and without stimulation with lipopolysaccharide (LPS) and P. brasiliensis exoantigen (PbAg) for 24 hours. Independent samples were compared using unpaired t tests, dependent samples were analyzed by paired t-test. Groups of more than two independent samples were analyzed using an ANOVA, with Tukey's post-test. Significance was set up at p <0.05. RESULTS: Our results showed high counts of peripheral blood CD14+CD16+ and CD14+CD16++ monocytes in untreated PCM-p accompanied by intense production of pro-inflammatory cytokines (IL-1ß and TNF-α) and profibrotic growth factors (TGF-ß1 and bFGF) by monocytes challenged with P. brasiliensis antigens. After the introduction of antifungal therapy, the counts of CD14+CD16+ cells returned to baseline while CD14+CD16++ counts remained high. Interestingly, counts of CD14+CD16++ monocytes remained elevated even 52 ± 7 months after successful antifungal treatment. Furthermore, the ACG-patients showed preserved pro-inflammatory activity in the presence of specific antigen stimuli and high spontaneous production of TNF-α by monocytes. CONCLUSIONS: Infection with Paracoccidioides leads to initiation of a specific proinflammatory response by monocytes of PCM-p during active disease and in the apparent cure. A profibrotic profile by monocytes was observed only at admission. Furthermore, PCM-p with apparent cure showed high spontaneous production of TNF-α and high counts of CD14+CD16++ monocytes, probably induced by hypoxia duo to fibrotic sequelae.

Dermatophyte-host relationship of a murine model of experimental invasive dermatophytosis.

Recognizing the invasive potential of the dermatophytes and understanding the mechanisms involved in this process will help with disease diagnosis and with developing an appropriate treatment plan. In this report, we present the histopathological, microbiological and immunological features of a model of invasive dermatophytosis that is induced by subcutaneous infection of Trichophyton mentagrophytes in healthy adult Swiss mice. Using this model, we observed that the fungus rapidly spreads to the popliteal lymph nodes, spleen, liver and kidneys. Similar to the human disease, the lymph nodes were the most severely affected sites. The fungal infection evoked acute inflammation followed by a granulomatous reaction in the mice, which is similar to what is observed in patients. The mice were able to mount a Th1-polarized immune response and displayed IL-10-mediated immune regulation. We believe that the model described here will provide valuable information regarding the dermatophyte-host relationship and will yield new perspective for a better understanding of the immunological and pathological aspects of invasive dermatophytosis.