Virulence Factors IN Fungi of Systemic Mycoses

Fatores de virulência em fungos de micoses sistêmicaFungos patogênicos causadores de micoses sistêmicas possuem vários fatores que permitem seu crescimento nas condições adversas oferecidas pelo hospedeiro, propiciando o estabelecimento da relação parasitária e contribuindo no processo de doença. Esses fatores são conhecidos como fatores de virulência auxiliando no desenvolvimento da infecção e interferindo com a patogênese das micoses. O presente trabalho avalia os fatores de virulência em fungos patogênicos como Blastomyces dermatitidis, Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum e Paracoccidioides brasiliensis, em relação à termotolerância, dimorfismo, componentes da parede celular ou cápsula, bem como a produção de enzimas. Os fatores de virulência auxiliam na aderência, colonização, disseminação e habilidade do fungo para resistir a ambientes hostis e escapar dos mecanismos da resposta imune do hospedeiro.Tanto os fatores de virulência apresentados por diferentes fungos, como os mecanismos de defesa oferecidos pelo hospedeiro requerem ação e interação de processos complexos, cujo conhecimento permitirá a melhor compreensão da patogenia das micoses sistêmicas.

Micoses sistémicas

Este trabalho teve como objetivo a análise das micoses sistémicas, no que respeita à sua identificação, morfologia dos agentes patogénicos que lhes dão origem, onde são endémicas, os sintomas que apresentam, os métodos de diagnóstico e as terapêuticas disponíveis para cada patologia. As micoses sistémicas são infeções causadas por fungos patogénicos primários que têm o trato respiratório como porta de entrada, e a partir daí podem disseminar-se por todo o organismo. Os agentes antifúngicos são usados no tratamento destas infeções, em que, no caso das infeções sistémicas, predominam o uso de cetoconazol (polieno), fluconazol e itraconazol (azóis). Existem ainda estudos que demonstram que as vacinas atenuadas podem ser usadas na profilaxia destas infeções. Com este trabalho conclui-se que as infeções fúngicas estão longe de ser extintas, uma vez que se verifica cada vez mais a existência de resistências por parte dos fungos aos fármacos, sendo o diagnóstico e a terapêutica usada dois parâmetros fundamentais para um tratamento eficaz.

Attempts at a peptide vaccine against paracoccidioidomycosis, adjuvant to chemotherapy

Chemotherapy is the basis of treatment of paracoccidioidomycosis in its various forms. Depending on the Paracoccidioides brasiliensis virulence, the status of host immunity, the degree of tissue involvement and fungal dissemination, treatment can be extended for long periods with an alarming frequency of relapses. Association of chemotherapy with a vaccine to boost the cellular immune response seemed a relevant project not only to reduce the time of treatment but also to prevent relapses and improve the prognosis of anergic cases. The candidate immunogen is the gp43 major diagnostic antigen of P. brasiliensis and more specifically its derived peptide P10, carrying the CD4(+) T-cell epitope. Both gp43 and P10 protected Balb/c mice against intratracheal infections with virulent P. brasiliensis strain. P10 as single peptide or in a multiple-antigen-peptide (MAP) tetravalent construction was protective without adjuvant either by preimmunization and intratracheal challenge or as a therapeutic agent in mice with installed infection. P10 showed additive protective effects in drug-treated mice stimulating a Th-1 type immune response with high IFN-gamma and IL-12. P10 and few other peptides in the gp43 were selected by Tepitope algorithm and actually shown to promiscuously bind several prominent HLA-DR molecules suggesting that a peptide vaccine could be devised for a genetically heterogenous population. P10 was protective in animals turned anergic, was effective in a DNA minigene vaccine, and increased the protection by monoclonal antibodies in Balb/c mice. DNA vaccines and peptide vaccines are promising therapeutic tools to be explored in the control of systemic mycoses.

Phylogenetic and evolutionary aspects of Paracoccidioides brasiliensis reveal a long coexistence with animal hosts that explain several biological features of the pathogen

The habitat of the mycelial saprobic form of Paracoccidio ides brasiliensis, which produces the infectious propagula, has not been determined and has proven difficult for mycologists to describe. The fungus has been rarely isolated from the environment, the disease has a prolonged latency period and no outbreaks have been reported. These facts have precluded the adoption of preventive measures to avoid infection. The confirmation of natural infections in nine-banded armadillos (Dasypus novemcinctus) with P. brasiliensis, in high frequency and wide geographic distribution, has opened new avenues for the study and understanding of its ecology. Armadillos belong to the order Xenarthra, which has existed in South America ever since the Paleocene Era (65 million years ago), when the South American subcontinent was still a detached land, before the consolidation of what is now known as the American continent. on the other hand, strong molecular evidence suggests that P. brasiliensis and other dimorphic pathogenic fungi - such as Blastomyces dermatitidis, Coccidioides immitis and Histoplasma capsulatum - belong to the family Onygenaceae sensu Into (order Onygenales, Ascomycota), which appeared around 150 million years ago.P. brasiliensis ecology and relation to its human host are probably linked to the fungal evolutionary past, especially its long coexistence with and adaptation to animal hosts other than Homo sapiens, of earlier origin. Instead of being a blind alley, the meaning of parasitism for dimorphic pathogenic fungi should be considered as an open two-way avenue, in which the fungus may return to the environment, therefore contributing to preserve its teleomorphic (sexual) and anamorphic (asexual) forms in a defined and protected natural habitat. (c) 2006 Elsevier B.V. All rights reserved.

Paracoccidioidomycosis: Survey and clinical aspects from the Department of Dermatology of the School of Medicine of Botucatu (Sao Paulo - Brazil)

Background - Paracoccidioidomycosis is the most frequent among the systemic mycoses in Brazil. Objective: To study the cases of paracoccidioidomycosis diagnosed from 1976 to 1996 at the Department of Dermatology of the School of Medicine of Botucatu. Methods - Descriptive study obtained from specific protocols comprising anamnesis, clinical- dermatological-laboratorial examination, treatment and follow-up of the patients. Results - Paracoccidioidomycosis was diagnosed in 1.04% of the dermatologic outpatients assisted from 1976 to 1996. In 315 cases, 89.8% were male, 61.9% were over forty and 53.7% were rural workers. The complaints were related more to oropharyngolaryngeal (53.6%) or cutaneous (23.8%) lesions or adenopathy (10.2%). Seventy patients had already been treated in other health services. The chronic multifocal clinical from was the most common: 80.6% of the cases, followed by the acute-subacute (juvenile type) 15.5%. The disease was pulmonary in 80.0%, oropharyngolaryngeal in 69.2% and cutaneous in 45.7%. Th treatment: Amphotericin B in 146 patients, Ketoconazole - 88, Itraconazole - 56, Sulfonamide derivatives - 146 and Terbinafine in 3. The lethality index resulting from the disease or its treatment was 2.0%. Conclusions - The high number of cases, showing the regional relevance of the disease and the high percentage of tegumentary complaints and the high number of relapsing are remarkable.

Importance of xenarthrans in the eco-epidemiology of Paracoccidioides brasiliensis

Background. Several pathogens that cause important zoonotic diseases have been frequently associated with armadillos and other xenarthrans. This mammal group typically has evolved on the South American continent and many of its extant species are seriously threatened with extinction. Natural infection of armadillos with Paracoccidioides brasiliensis in hyperendemic areas has provided a valuable opportunity for understanding the role of this mammal in the eco-epidemiology of Paracoccidioidomycosis (PCM), one of the most important systemic mycoses in Latin America. Findings. This study aimed to detect P. brasiliensis in different xenarthran species (Dasypus novemcinctus, Cabassous spp., Euphractus sexcinctus, Tamandua tetradactyla and Myrmecophaga tridactyla), by molecular and mycological approaches, in samples obtained by one of the following strategies: i) from road-killed animals (n = 6); ii) from naturally dead animals (n = 8); iii) from animals that died in captivity (n = 9); and iv) from living animals captured from the wild (n = 2). Specific P. brasiliensis DNA was detected in several organs among 7/20 nine-banded armadillos (D. novemcinctus) and in 2/2 anteaters (M. tridactyla). The fungus was also cultured in tissue samples from one of two armadillos captured from the wild. Conclusion. Members of the Xenarthra Order, especially armadillos, have some characteristics, including a weak cellular immune response and low body temperature, which make them suitable models for studying host-pathogen interaction. P. brasiliensis infection in wild animals, from PCM endemic areas, may be more common than initially postulated and reinforces the use of these animals as sentinels for the pathogen in the environment. © 2009 Bagagli et al; licensee BioMed Central Ltd.

Expressão gênica das adesinas e fatores de virulência da fase miceliar e leveduriforme do complexo paracoccidioides e de sua interação com células epiteliais e fagócitos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Experimental Model of Arthritis Induced by Paracoccidioides brasiliensis in Rats

Paracoccidioidomycosis (PCM), a disease caused by the fungus Paracoccidioides brasiliensis (Pb), is highly prevalent in Brazil, where it is the principal cause of death by systemic mycoses. The disease primarily affects men aged 30-50 year old and usually starts as a pulmonary focus and then may spread to other organs and systems, including the joints. The present study aimed to develop an experimental model of paracoccidioidomycotic arthritis. Two-month-old male Wistar rats (n = 48) were used, divided in 6 groups: test groups EG/15 and EG/45 (received one dose of 100 mu l of saline containing 10(5) Pb viable yeasts in the knee); heat killed Pb-group HK/15 and HK/45 (received a suspension of 10(5) Pb nonviable yeasts in the knee) and control groups CG/15 and CG/45 (received only sterile saline in the knee). The rats were killed 15 and 45 days postinoculation. In contrast with the control rats, the histopathology of the joints of rats of the test groups (EG/15 and EG/45) revealed a picture of well-established PCM arthritis characterized by extensive sclerosing granulomatous inflammation with numerous multiple budding fungal cells. The X-ray examination revealed joint alterations in these groups. Only metabolic active fungi evoked inflammation. The experimental model was able to induce fungal arthritis in the knees of the rats infected with metabolic active P. brasiliensis. The disease tended to be regressive and restrained by the immune system. No evidence of fungal dissemination to the lungs was observed.

Therapeutic DNA Vaccine Encoding Peptide P10 against Experimental Paracoccidioidomycosis

Paracoccidioidomycosis (PCM), caused by Paracoccidioides brasiliensis, is the most prevalent invasive fungal disease in South America. Systemic mycoses are the 10th most common cause of death among infectious diseases in Brazil and PCM is responsible for more than 50% of deaths due to fungal infections. PCM is typically treated with sulfonamides, amphotericin B or azoles, although complete eradication of the fungus may not occur and relapsing disease is frequently reported. A 15-mer peptide from the major diagnostic antigen gp43, named P10, can induce a strong T-CD4+ helper-1 immune response in mice. The TEPITOPE algorithm and experimental data have confirmed that most HLA-DR molecules can present P10, which suggests that P10 is a candidate antigen for a PCM vaccine. In the current work, the therapeutic efficacy of plasmid immunization with P10 and/or IL-12 inserts was tested in murine models of PCM. When given prior to or after infection with P. brasiliensis virulent Pb 18 isolate, plasmid-vaccination with P10 and/or IL-12 inserts successfully reduced the fungal burden in lungs of infected mice. In fact, intramuscular administration of a combination of plasmids expressing P10 and IL-12 given weekly for one month, followed by single injections every month for 3 months restored normal lung architecture and eradicated the fungus in mice that were infected one month prior to treatment. The data indicate that immunization with these plasmids is a powerful procedure for prevention and treatment of experimental PCM, with the perspective of being also effective in human patients.

Importance of xenarthrans in the eco-epidemiology of Paracoccidioides brasiliensis

Abstract Background Several pathogens that cause important zoonotic diseases have been frequently associated with armadillos and other xenarthrans. This mammal group typically has evolved on the South American continent and many of its extant species are seriously threatened with extinction. Natural infection of armadillos with Paracoccidioides brasiliensis in hyperendemic areas has provided a valuable opportunity for understanding the role of this mammal in the eco-epidemiology of Paracoccidioidomycosis (PCM), one of the most important systemic mycoses in Latin America. Findings This study aimed to detect P. brasiliensis in different xenarthran species (Dasypus novemcinctus, Cabassous spp., Euphractus sexcinctus, Tamandua tetradactyla and Myrmecophaga tridactyla), by molecular and mycological approaches, in samples obtained by one of the following strategies: i) from road-killed animals (n = 6); ii) from naturally dead animals (n = 8); iii) from animals that died in captivity (n = 9); and iv) from living animals captured from the wild (n = 2). Specific P. brasiliensis DNA was detected in several organs among 7/20 nine-banded armadillos (D. novemcinctus) and in 2/2 anteaters (M. tridactyla). The fungus was also cultured in tissue samples from one of two armadillos captured from the wild. Conclusion Members of the Xenarthra Order, especially armadillos, have some characteristics, including a weak cellular immune response and low body temperature, which make them suitable models for studying host-pathogen interaction. P. brasiliensis infection in wild animals, from PCM endemic areas, may be more common than initially postulated and reinforces the use of these animals as sentinels for the pathogen in the environment.

Crystal structure of cytochrome P450 14α-sterol demethylase (CYP51) from Mycobacterium tuberculosis in complex with azole inhibitors

Cytochrome P450 14α-sterol demethylases (CYP51) are essential enzymes in sterol biosynthesis in eukaryotes. CYP51 removes the 14α-methyl group from sterol precursors such as lanosterol, obtusifoliol, dihydrolanosterol, and 24(28)-methylene-24,25-dihydrolanosterol. Inhibitors of CYP51 include triazole antifungal agents fluconazole and itraconazole, drugs used in treatment of topical and systemic mycoses. The 2.1- and 2.2-Å crystal structures reported here for 4-phenylimidazole- and fluconazole-bound CYP51 from Mycobacterium tuberculosis (MTCYP51) are the first structures of an authentic P450 drug target. MTCYP51 exhibits the P450 fold with the exception of two striking differences—a bent I helix and an open conformation of BC loop—that define an active site-access channel running along the heme plane perpendicular to the direction observed for the substrate entry in P450BM3. Although a channel analogous to that in P450BM3 is evident also in MTCYP51, it is not open at the surface. The presence of two different channels, with one being open to the surface, suggests the possibility of conformationally regulated substrate-in/product-out openings in CYP51. Mapping mutations identified in Candida albicans azole-resistant isolates indicates that azole resistance in fungi develops in protein regions involved in orchestrating passage of CYP51 through different conformational stages along the catalytic cycle rather than in residues directly contacting fluconazole. These new structures provide a basis for rational design of new, more efficacious antifungal agents as well as insight into the molecular mechanism of P450 catalysis.

Mycoses associated with AIDS in the Third World

Despite advances in diagnosis and treatment, the epidemiological status of the human immunodeficiency virus (HIV) infection is far from under control in most of the developing world. Sub-Saharan Africa, Southeast Asia and India show increased rates of new infections. In Latin America and the Caribbean there were 1.6 million estimated cases of HIV-infected patients at the end of 1997. Fungal diseases have been one of the most relevant diagnoses in relation to the acquired immunodeficiency syndrome (AIDS), Infections due to Candida species and Cryptococcus neoformans var, neoformans are common worldwide. Histoplasma capsulatum, Coccidioides immitis and Penicillium marneffei are important causes of disease in endemic areas. Infection due to Sporothrix schenckii, Blastomyces dermatitidis and Paracoccidioides brasiliensis are uncommon even where they are endemic. Phaeohyphomycetes, hyalohyphomycetes and zygomycetes are still rare as a cause of disease among AIDS patients, However, agents pertaining to these groups, such as Aspergillus spp., have an increasing incidence. Superficial mycoses due to dermatophytes have special features from epidemiological, clinical and therapeutic points of view.

Experimental systemic virulence of oral Candida dubliniensis isolates in comparison with Candida albicans, Candida tropicalis and Candida krusei

There are no previous studies on the comparative virulence of Candida dubliniensis with other non-albicans species. The aim of this study was to compare the virulence and infection kinetics of C. dubliniensis and other species. Candida albicans, C. dubliniensis, Candida tropicalis and Candida krusei (reference strains) were inoculated intravenously in mice. For infection kinetics evaluation, a group of five animals were sacrificed after 6 h, 3, 7, 14 and 21 days. Microbiological evaluations (liver, spleen, kidneys, lungs and brain) and histopathological examination of the kidney were performed. The results of virulence evaluation were analysed using Kaplan-Meier survival analysis (5%). Candida dubliniensis-inoculated mice survived for longer periods compared with those with C. albicans (P = 0.005). No differences were detected in relation to C. tropicalis (P = 0.326) and C. krusei (P = 0.317). Most of the organs were persistently colonised by C. albicans and C. dubliniensis even by day 21. Tendency of C. krusei clearance was observed in all organs. Fungal masses and renal lesions were observed after inoculation of C. albicans, C. dubliniensis and C. tropicalis. Within the limits of the study, data on survival rate and dissemination capacity suggest that C. dubliniensis is less virulent than C. albicans.

Systemic racism: the hidden barrier to educational success for Indigenous school students

Explanations for poor educational experiences and results for Australian Indigenous school students have, to a great extent, focused on intended or conscious acts or omissions. This paper adopts an analysis based on the legislation prohibiting indirect racial discrimination. Using the elements of the legislation and case law it argues that apparently benign and race-neutral policies and practices may unwittingly be having an adverse impact on Indigenous students' education. These practices or policies include the building blocks of learning, a Eurocentric school culture. Standard English as the language of assessment, legislation to limit schools' legal liability, and teachers' promotions.

In Pursuit of Excellence : A Policy Driven Systemic Initiative to Embed Gifted Education

Embedding gifted education practices requires major professional development strategies supported by transparent, credible and enforceable policy. This paper describes an analysis of a state-wide initiative involving the establishment of a series of schools tasked to develop and disseminate gifted education principles. The authors have been involved with this initiative at a number of levels over a ten-year period. Their involvement culminated in a commissioned review of the program. Extensive qualitative data were purposively collected from all stakeholders and the effectiveness of the initiative is examined from a theoretical framework of policy development and excellence. The findings summarised in this proposal, indicate the achievement of excellence at a systemic level was constrained by lack of vision, leadership and commitment to long term achievements of excellence. At a local level evidence exists that excellence can be manifested when there is synchronicity of vision, purpose, decisions, and actions.