Unbalanced inflammatory reaction could increase tissue destruction and worsen skin infectious diseases - a comparative study of leishmaniasis and sporotrichosis

Human interleukin-36γ plays a crucial role in cytokine induction during Sporothrix brasiliensis and S. schenckii infection in keratinocytes and PBMCs

Cytokines of the interleukin (IL)-1 superfamily including the different IL-36 isoforms, have been reported as mediators of acute and chronic inflammation in human skin diseases, such as psoriasis. Here, we demonstrated for the first time that Sporothrix schenckii and S. brasiliensis, the fungi that cause subcutaneous infection sporotrichosis, can induce the expression of IL-36α, IL-36γ and IL-36Ra in human keratinocytes and primary peripheral blood mononuclear cells (PBMCs). Specifically, IL-36γ was differentially expressed by keratinocytes stimulated with Sporothrix yeasts when compared to the commensal microorganism Staphylococcus epidermidis. The exposure of keratinocytes to 24 h or 7-days culture supernatant of PBMCs stimulated with Sporothrix induced higher IL-36γ production compared to direct stimulation of keratinocytes with the live fungus. We identified that IL-36γ mRNA expression in keratinocytes is increased in the presence of IL-17, TNF, IL-1β and IL-1α and these cytokines may act synergistically to maintain IL-36γ production. Lastly, using a cohort of 164 healthy individuals, we showed that individuals carrying variants of the IL36G gene (rs11690399 and rs11683399) exhibit increased IL-36γ production as well as increased innate cytokine production after Sporothrix exposure. Importantly, stimulation of PBMCs with recombinant IL-36γ increased the production of IL-1β and IL-6, while IL-36Ra were able to decrease the concentration of these cytokines. Our findings contribute to the understanding of the pathogenesis of sporotrichosis and suggest that IL-36γ may be involved in maintaining the cytokine loop that leads to tissue destruction by exacerbating the immune response in sporotrichosis. Of high interest, we present the IL-36 signalling pathway as a potential new therapeutic target.

An Immune-Based Therapeutical Approach in an Elderly Patient With Fixed Cutaneous Sporotrichosis

Sporotrichosis is a subcutaneous fungal infection caused by thermally dimorphic fungi from the Sporothrix genus, primarily prevalent in tropical regions of Latin America, Africa, and Asia. Mexico's Jalisco state is an endemic hotspot with a remarkable prevalence rate of 54.4%. Clinical presentation varies based on immune status and virulence. The most common form is cutaneous-lymphangitic (67%), with fixed cutaneous cases accounting for 28%. This case study explores a traditional therapeutic approach for fixed cutaneous sporotrichosis but introduces a distinct immunological perspective.

cFLIPS regulates alternative NLRP3 inflammasome activation in human monocytes

The innate immune responses, including inflammasome activation, are paramount for host defense against pathogen infection. In contrast to canonical and noncanonical inflammasome activation, in this study, heat-killed gram-negative bacteria (HK bacteria) were identified as single-step stimulators of the NLRP3 inflammasome in human monocytes, and they caused a moderate amount of IL-1β to be released from cells. Time course experiments showed that this alternative inflammasome response was finished within a few hours. Further analysis showed that the intrinsically limited NLRP3 inflammasome activation response was due to the negative regulation of caspase-8 by the short isoform of cFLIP (cFLIPs), which was activated by NF-κB. In contrast, overexpressed cFLIPS, but not overexpressed cFLIPL, inhibited the activation of caspase-8 and the release of IL-1β in response to HK bacteria infection in human monocytes. Furthermore, we demonstrated that TAK1 activity mediated the expression of cFLIPs and was upstream and essential for the caspase-8 cleavage induced by HK bacteria in human monocytes. The functional specificity of cFLIPs and TAK1 revealed unique responses of human monocytes to a noninvasive pathogen, providing novel insights into an alternative regulatory pathway of NLRP3 inflammasome activation.

Murine Susceptibility to Leishmania amazonensis Infection Is Influenced by Arginase-1 and Macrophages at the Lesion Site

Cutaneous leishmaniasis is a zoonotic infectious disease broadly distributed worldwide, causing a range of diseases with clinical outcomes ranging from self-healing infections to chronic disfiguring disease. The effective immune response to this infection is yet to be more comprehensively understood and is fundamental for developing drugs and vaccines. Thus, we used experimental models of susceptibility (BALB/c) and partial resistance (C57BL/6) to Leishmania amazonensis infection to investigate the local profile of mediators involved in the development of cutaneous leishmaniasis. We found worse disease outcome in BALB/c mice than in C57BL/6 mice, with almost 15 times higher parasitic load, ulcerated lesion formation, and higher levels of IL-6 in infected paws. In contrast, C57BL/6 presented higher levels of IFN-γ and superoxide anion (•O2−) after 11 weeks of infection and no lesion ulcerations. A peak of local macrophages appeared after 24 h of infection in both of the studied mice strains, followed by another increase after 240 h, detected only in C57BL/6 mice. Regarding M1 and M2 macrophage phenotype markers [iNOS, MHC-II, CD206, and arginase-1 (Arg-1)], we found a pronounced increase in Arg-1 levels in BALB/c after 11 weeks of infection, whereas C57BL/6 showed an initial predomination of markers from both profiles, followed by an M2 predominance, coinciding with the second peak of macrophage infiltration, 240 h after the infection. Greater deposition of type III collagen and lesion resolution was also observed in C57BL/6 mice. The adoptive transfer of macrophages from C57BL/6 to infected BALB/c at the 11th week showed a reduction in both edema and the number of parasites at the lesion site, in addition to lower levels of Arg-1. Thus, C57BL/6 mice have a more effective response against L. amazonensis, based on a balance between inflammation and tissue repair, while BALB/c mice have an excessive Arg-1 production at late infection. The worst evolution seems to be influenced by recruitment of Arg-1 related macrophages, since the adoptive transfer of macrophages from C57BL/6 mice to BALB/c resulted in better outcomes, with lower levels of Arg-1.

The Role of Macrophages in the Host's Defense against Sporothrix schenckii

The role of immune cells associated with sporotrichosis caused by Sporothrix schenckii is not yet fully clarified. Macrophages through pattern recognition receptors (PRRs) can recognize pathogen-associated molecular patterns (PAMPs) of Sporothrix, engulf it, activate respiratory burst, and secrete pro-inflammatory or anti-inflammatory biological mediators to control infection. It is important to consider that the characteristics associated with S. schenckii and/or the host may influence macrophage polarization (M1/M2), cell recruitment, and the type of immune response (1, 2, and 17). Currently, with the use of new monocyte-macrophage cell lines, it is possible to evaluate different host-pathogen interaction processes, which allows for the proposal of new mechanisms in human sporotrichosis. Therefore, in order to contribute to the understanding of these host-pathogen interactions, the aim of this review is to summarize and discuss the immune responses induced by macrophage-S. schenckii interactions, as well as the PRRs and PAMPs involved during the recognition of S. schenckii that favor the immune evasion by the fungus.

A Cytokine Network Balance Influences the Fate of Leishmania (Viannia) braziliensis Infection in a Cutaneous Leishmaniasis Hamster Model

The golden hamster is a suitable model for studying cutaneous leishmaniasis (CL) due to Leishmania (Viannia) braziliensis. Immunopathological mechanisms are well established in the L. (L.) major-mouse model, in which IL-4 instructs a Th2 response towards progressive infection. In the present study, we evaluated the natural history of L. braziliensis infection from its first stages up to lesion establishment, with the aim of identifying immunological parameters associated with the disease outcome and parasitism fate. To this end, hamsters infected with 10⁴, 10⁵, or 10⁶ promastigotes were monitored during the first hours (4h, 24h), early (15 days, 30 days) and late (50 days) post-infection (pi) phases. Cytokines, iNOS and arginase gene expression were quantified in the established lesions by reverse transcription-quantitative PCR. Compared to the 10⁵ or 10⁶ groups, 10⁴ animals presented lower lesions sizes, less tissue damage, and lower IgG levels. Basal gene expression in normal skin was high for TGF-β, and intermediary for TNF, IL-6, and IL-4. At 4hpi, no cytokine induction was observed in the 10⁴ group, while an upregulation of IL-6, IL-10, and IL-4 was observed in the 10⁶ group. At 15dpi, lesion appearance was accompanied by an increased expression of all assessed cytokines, markedly in the 10⁵ and 10⁶ groups. Upregulation of all investigated cytokines was observed in the late phase, although less expressive in the 10⁴ group. IFN-γ was the depending variable influencing tissue damage, while IL-6 was associated to parasite load. The network correlating gene expression and clinical and laboratorial parameters indicated inoculum-independent associations at 15 and 30dpi. A strong positive network correlation was observed in the 10⁴ group, but not in the 10⁵ or 10⁶ groups. In conclusion, IL-4, IL-6, IL-10, and TGF-β are linked o L. braziliensis progression. However, a balanced cytokine network is the key for an immune response able to reduce the ongoing infection and reduce pathological damage.

NOx-, IL-1β-, TNF-α-, and IL-6-Inhibiting Effects and Trypanocidal Activity of Banana (Musa acuminata) Bracts and Flowers: UPLC-HRESI-MS Detection of Phenylpropanoid Sucrose Esters

Banana inflorescences are a byproduct of banana cultivation consumed in various regions of Brazil as a non-conventional food. This byproduct represents an alternative food supply that can contribute to the resolution of nutritional problems and hunger. This product is also used in Asia as a traditional remedy for the treatment of various illnesses such as bronchitis and dysentery. However, there is a lack of chemical and pharmacological data to support its consumption as a functional food. Therefore, this work aimed to study the anti-inflammatory action of Musa acuminata blossom by quantifying the cytokine levels (NO_x, IL-1β, TNF-α, and IL-6) in peritoneal neutrophils, and to study its antiparasitic activities using the intracellular forms of T. cruzi, L. amazonensis, and L. infantum. This work also aimed to establish the chemical profile of the inflorescence using UPLC-ESI-MS analysis. Flowers and the crude bract extracts were partitioned in dichloromethane and n-butanol to afford four fractions (FDCM, FNBU, BDCM, and BNBU). FDCM showed moderate trypanocidal activity and promising anti-inflammatory properties by inhibiting IL-1β, TNF-α, and IL-6. BDCM significantly inhibited the secretion of TNF-α, while BNBU was active against IL-6 and NO_x. LCMS data of these fractions revealed an unprecedented presence of arylpropanoid sucroses alongside flavonoids, triterpenes, benzofurans, stilbenes, and iridoids. The obtained results revealed that banana inflorescences could be used as an anti-inflammatory food ingredient to control inflammatory diseases.

In-situ immune profile of polymorphic vs. macular Indian Post Kala-azar dermal leishmaniasis

Post Kala-azar Dermal Leishmaniasis (PKDL), a sequel of apparently cured Visceral Leishmaniasis presents in South Asia with papulonodular (polymorphic) or hypomelanotic lesions (macular). Till date, the polymorphic variant was considered predominant, constituting 85–90%. However, following active-case surveillance, the proportion of macular PKDL has increased substantially to nearly 50%, necessitating an in-depth analysis of this variant. Accordingly, this study aimed to delineate the cellular infiltrate in macular vis-à-vis polymorphic PKDL. To study the overall histopathology, hematoxylin and eosin staining was performed on lesional sections and phenotyping by immunohistochemistry done in terms of dendritic cells (CD1a), macrophages (CD68), HLA-DR, T-cells (CD8, CD4), B-cells (CD20) and Ki67 along with assessment of the status of circulating homing markers CCL2, CCL7 and CXCL13. In polymorphic cases (n = 20), the cellular infiltration was substantial, whereas in macular lesions (n = 20) it was mild and patchy with relative sparing of the reticular dermis. Although parasite DNA was identified in both variants by ITS-1 PCR, the parasite load was significantly higher in the polymorphic variant and Leishman-Donovan bodies were notably minimally present in macular cases. Both variants demonstrated a decrease in CD1a⁺ dendritic cells, HLA-DR expression and CD4⁺ T-cells. In macular cases, the proportion of CD68⁺ macrophages, CD8⁺ T-cells and CD20⁺ B-cells was 4.6 fold, 17.0 fold and 1.6 fold lower than polymorphic cases. The absence of Ki67 positivity and increased levels of chemoattractants suggested dermal homing of these cellular subsets. Taken together, as compared to the polymorphic variant, patients with macular PKDL demonstrated a lower parasite load along with a lesser degree of cellular infiltration, suggesting differences in host-pathogen interactions, which in turn can impact on their disease transmitting potential and responses to chemotherapy.

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Comparative analysis of immunopathology of polymorphic vs. macular PKDL.

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Dense lymphohistiocytic infiltrate in polymorphic PKDL.

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Mild and patchy cellular infiltration in macular PKDL with minimal Leishman Donovan bodies.

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Decreased presence of CD1a, HLA-DR and CD4⁺ T-cells in both variants.

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The presence of CD8⁺, CD68⁺and CD20⁺ cells in polymorphic>>>macular PKDL.

Sporotrichosis In Immunocompromised Hosts

Sporotrichosis is a global implantation or subcutaneous mycosis caused by several members of the genus Sporothrix, a thermo-dimorphic fungus. This disease may also depict an endemic profile, especially in tropical to subtropical zones around the world. Interestingly, sporotrichosis is an anthropozoonotic disease that may be transmitted to humans by plants or by animals, especially cats. It may be associated with rather isolated or clustered cases but also with outbreaks in different periods and geographic regions. Usually, sporotrichosis affects immunocompetent hosts, presenting a chronic to subacute evolution course. Less frequently, sporotrichosis may be acquired by inhalation, leading to disseminated clinical forms. Both modes of infection may occur in immunocompromised patients, especially associated with human immunodeficiency virus (HIV) infection, but also diabetes mellitus, chronic alcoholism, steroids, anti-TNF treatment, hematologic cancer and transplanted patients. Similar to other endemic mycoses caused by dimorphic fungi, sporotrichosis in immunocompromised hosts may be associated with rather more severe clinical courses, larger fungal burden and longer periods of systemic antifungal therapy. A prolonged outbreak of cat-transmitted sporotrichosis is in progress in Brazil and potentially crossing the border to neighboring countries. This huge outbreak involves thousands of human and cats, including immunocompromised subjects affected by HIV and FIV (feline immunodeficiency virus), respectively. We reviewed the main epidemiologic, clinical, diagnostic and therapeutic aspects of sporotrichosis in immunocompromised hosts.

Immunopathogenesis of Human Sporotrichosis: What We Already Know

Sporotrichosis is a subacute/chronic mycosis caused by dimorphic fungus of the genus Sporothrix. This mycosis may affect both human and domestic animals and in the last few years, the geographic dispersion and increase of sporotrichosis worldwide has been observed. The occurrence of cases related to scratching/bites of domestic felines have increased, characterizing the disease as predominantly a zoonosis. In humans, sporotrichosis mainly involves the cutaneous tegument of infected patients, but other tissues may also present the infection. The main forms of clinical presentation are lymphocutanous sporotrichosis (LC) and fixed sporotrichosis (F). Although less common, mucosal, cutaneous disseminated, and extracutaneous forms have also been described. Multiple factors from the fungus and host can play a role in driving the clinical evolution of sporotrichosis to benign or severe disease. In this review, we discuss the immunopathological aspects involved in human sporotrichosis. Putting together the two branches of knowledge—host immune response and fungal evading mechanisms—we may perceive new possibilities in understanding the fungus–host interaction in order to be in a position to go further in the control of sporotrichosis.