Granulomatous reaction induced by lipids isolated from Paracoccidioides brasiliensis

Lipidomic analysis of extracellular vesicles from the pathogenic phase of Paracoccidioides brasiliensis

BACKGROUND

Fungal extracellular vesicles are able to cross the cell wall and transport molecules that help in nutrient acquisition, cell defense, and modulation of the host defense machinery.

METHODOLOGY/PRINCIPAL FINDINGS

Here we present a detailed lipidomic analysis of extracellular vesicles released by Paracoccidioides brasiliensis at the yeast pathogenic phase. We compared data of two representative isolates, Pb3 and Pb18, which have distinct virulence profiles and phylogenetic background. Vesicle lipids were fractionated into different classes and analyzed by either electrospray ionization- or gas chromatography-mass spectrometry. We found two species of monohexosylceramide and 33 phospholipid species, including phosphatidylcholine, phosphatidylethanolamine, phosphatidic acid, phosphatidylserine, phosphatidylinositol, and phosphatidylglycerol. Among the phospholipid-bound fatty acids in extracellular vesicles, C181 predominated in Pb3, whereas C18:2 prevailed in Pb18. The prevalent sterol in Pb3 and Pb18 vesicles was brassicasterol, followed by ergosterol and lanosterol. Inter-isolate differences in sterol composition were observed, and also between extracellular vesicles and whole cells.

CONCLUSIONS/SIGNIFICANCE

The extensive lipidomic analysis of extracellular vesicles from two P. brasiliensis isolates will help to understand the composition of these fungal components/organelles and will hopefully be useful to study their biogenesis and role in host-pathogen interactions.

In vitro granuloma formation, NO production and cytokines profile from human mononuclear cells induced by fractionated antigens of Paracoccidioides brasiliensis

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis prevalent in South America, and cell-mediated immunity represents the main mode of protection against this fungal infection. We investigated in vitro the response of peripheral blood mononuclear cells (PBMC) from paracoccidioidomycosis (PCM) patients presenting different clinical forms to antigenic fractions from P. brasiliensis yeast cell lysate (PbAg). These fractions designated F0 to FV were obtained using anion-exchange chromatography on a FPLC system. Our studies showed variation in the cellular responses induced by different antigenic fractions. The fraction F0 caused significant decrease in cellular proliferation, granuloma formation, accompanied by significant elevation in the production of IL-10. The fractions FII and FIII increased in vitro granuloma formation associated with high production of TNF-alpha. Besides that, FII and FIII evoked decrease in NO production but not F0 that induced very high levels, among patients with PCM from acute form. The findings suggest that P. brasiliensis antigenic components participate in the modulation or activation of PBMC response in PCM, and IL-10 and NO could be important in the regulation of in vitro granuloma formation.

Fibrotic sequelae in pulmonary paracoccidioidomycosis: histopathological aspects in BALB/c mice infected with viable and non-viable paracoccidioides brasiliensis propagules

Patients with paracoccidioidomycosis often present pulmonary fibrosis and exhibit important respiratory limitations. Based on an already established animal model, the contribution of viable and non-viable P. brasiliensis propagules to the development of fibrosis was investigated. BALB/c male mice, 4-6 weeks old were inoculated intranasally either with 4x10(6) viable conidia (Group I), or 6. 5x10(6) fragmented yeast cells (Group II). Control animals received PBS. Six mice per period were sacrificed at 24, 48, 72h (initial) and 1, 2, 4, 8, 12 and 16 weeks post-challenge (late). Paraffin embedded lungs were sectioned and stained with H&E, trichromic (Masson), reticulin and Grocot&tacute;s. During the initial period PMNs influx was important in both groups and acute inflammation involving 34% to 45% of the lungs was noticed. Later on, mononuclear cells predominated. In group I, the inflammation progressed and granulomas were formed and by the 12th week they fussed and became loose. Thick collagen I fibers were observed in 66.6% and 83.3% of the animals at 8 and 12 weeks, respectively. Collagen III, thick fibers became apparent in some animals at 4 weeks and by 12 weeks, 83% of them exhibited alterations in the organization and thickness of these elements. In group II mice, this pattern was different with stepwise decrease in the number of inflammatory foci and lack of granulomas. Although initially most animals in this group had minor alterations in thin collagen I fibers, they disappeared by the 4th week. Results indicate that tissue response to fragmented yeast cells was transitory while viable conidia evoked a progressive inflammatory reaction leading to granuloma formation and to excess production and/or disarrangement of collagens I and III; the latter led to fibrosis.

Haematological alterations induced by biochemical fractions of Paracoccidioides brasiliensis in mice

Biochemical fractions of Paracoccidioides brasiliensis were obtained for experimental inoculation in mice followed by haematological analysis. Dead total fungus, total fungus disrupted by ultrasonic waves, lipids of the fungus, supernatant of the lipid purification, and integral and disrupted fungus free of lipids were obtained. The six fractions were obtained from lyophilized yeasts of a recent isolate of P. brasiliensis and from a pool comprising equal amounts of four strains maintained in the laboratory for some time. Different doses of the 12 fractions were intraperitoneally inoculated into mice and haematological analysis was done 30 days later. No significant alterations were detected in the red blood cell series. However, the white blood cell series showed marked alterations, such as leukopenia, with relative neutrophilia and lymphopenia. Thrombocytosis occurred widely. The haematological alterations revealed associations with the injected doses without relation to the biochemical composition of the different fractions. No difference in the capacity for inducing haematological alterations was found between the fractions obtained from the recent isolate and from the older ones.

Histological and ultrastructural study of the inflammation evoked by Paracoccidioides brasiliensis antigen in previously immunized mice

Bentonite particles uncoated and coated with soluble antigen of Paracoccidioides brasiliensis (Pb) were intravenously injected into mice with and without previous immunization with Pb antigen. The inflammatory reaction around the bentonite emboli in small lung vessels was quantitated and morphologically studied by light and electron (EM) microscopy, 2 to 8 days after challenge. In control nonimmunized animals, coated and uncoated bentonite particles caused mild and nonspecific inflammation made up by macrophages. By EM, they formed loosely aggregated clusters with cytoplasm containing few organelles and borders without interdigitation. In immunized mice injected with coated bentonite particles, the inflammatory area was significantly greater than that in nonimmunized animals in all periods of study with maximum difference at day 2. The inflammatory process at days 2 and 4 was characterized as mature granulomata, composed of macrophages with great number of organelles in the cytoplasm, large euchromatic nuclei and prominent nucleoli. Altogether these findings indicated a lesion with high metabolic activity, compatible with a granulomatous hypersensitivity reaction. At days 6 and 8, there was a change from mature to epithelioid granulomata, well demonstrated by EM which showed macrophages with characteristically interdigitated cytoplasmic borders. The results strengthen the importance of cellular immunity in the genesis of epithelioid granuloma in paracoccidioidomycosis and reinforce the usefulness of the present model in studies of the inflammatory cellular sequency and events in this mycosis.

Host-parasite relationships in paracoccidioidomycosis

A viewpoint of host-parasite relationships in paracoccidioidomycosis is presented. The characteristics of the fungus which are important to the host-parasite interaction are discussed. Aspects of inhibition of mycelium-to-yeast transformation by estrogens acting at receptors on the fungal wall and in the cytoplasm, and the role of polysaccharide components of the cell wall in virulence are reviewed. The natural mechanisms of host defense are also examined, including phagocytosis, complement system, natural-killer cells and genetic control of resistance and susceptibility. Finally, a discussion of granuloma morphogenesis and its relationship to the humoral and cellular anti-P. brasiliensis immune response is presented.

The role of fractions from Paracoccidioides brasiliensis in the genesis of inflammatory response

The influx of inflammatory cells towards the peritoneal cavity in rats inoculated intraperitoneally with subcellular preparations of the fungus Paracoccidioides brasiliensis was studied. In addition to the dead fungus, also fractions F1 of the cell wall, which mainly consisted of polysaccharides and the lipid extract, induced intense cell migration 4 hr after inoculation, with a greatly increased number of polymorphonuclear leucocytes (PMN). Study of the kinetics of cell influx showed that both fraction F1 and the lipid extract initially induced intense PMN migration between the 4th and 24th hr after inoculation of these agents, followed by migration of mononuclear cells (MN) around the 48th hr. We also observed that migration of these cells increased gradually after inoculation of growing doses of fraction F1. The present data suggest that polysaccharides and lipids isolated from P. brasiliensis may participate in the initial phase of the inflammatory response in paracoccidioidomycosis.

Parasitic adaptation of pathogenic fungi to mammalian hosts

Pathogenic fungi involved in medical and veterinary mycology can be classified in three different groups according to their level of adaptation to parasitism. Only a few species belonging to dermatophytes can be considered genuine parasites as opposed to molds or fungi involved in systemic mycoses. Ecological, ethological, biochemical, and immunological factors can play a role in preadaptation or adaptation to parasitic life and are discussed.