Immunization with Recombinant Pb27 Protein Reduces the Levels of Pulmonary Fibrosis Caused by the Inflammatory Response Against Paracoccidioides brasiliensis

Diagnosis and Treatment of Pulmonary Coccidioidomycosis and Paracoccidioidomycosis

Coccidioidomycosis (CM) and paracoccidioidomycosis (PCM) are systemic mycoses that are highly endemic in Latin America and have recently been included on the World Health Organization (WHO) Fungal Priority Pathogens List. Coccidioides immitis and Coccidioides posadasii are recognized as etiological agents of CM, with peculiarities in their geographic distribution. The genus Paracoccidioides now includes Paracoccidioides lutzii and the Paracoccidioides brasiliensis complex, which encompasses four phylogenetic species. In both diseases, pulmonary signs and symptoms are the main reasons for patients to seek medical assistance, and they are frequently misdiagnosed as tuberculosis. In this paper, we present a critical view of the strategies for diagnosis and clinical management of CM and PCM. Over the past few decades, there has been an increase in the number of reports of endemic fungal infections in areas previously thought to be "non-endemic" due to climate change and increased travel, among other factors. Learning to recognize their main epidemiological aspects and clinical manifestations is crucial so that clinicians can include them in the differential diagnosis of lung disease and avoid late diagnosis.

The Therapy of Pulmonary Fibrosis in Paracoccidioidomycosis: What Are the New Experimental Approaches?

Pulmonary fibrosis (PF) is considered the most important sequela developed in patients suffering from the chronic form of paracoccidioidomycosis (PCM), which leads to the loss of respiratory function in 50% of cases; this residual pulmonary abnormality is present even after antifungal treatment. To date, there is no effective treatment for PF. However, the use of antifungal drugs in combination with other antibiotics or immunomodulatory compounds, as well as biological therapies that include a monoclonal antibody specific to neutrophils, or prophylactic vaccination employing a recombinant antigen of Paracoccidioides brasiliensis that successfully attenuated PF, has been reported. Additionally, mesenchymal stem cell transplantation in combination with antifungal therapy slightly reduced the inflammatory response and profibrotic molecules induced by P. brasiliensis infection. In this review, I report experimental findings from several studies aiming to identify promising therapeutic strategies for treating PF developed in PCM.

Evaluation of antifibrotic and antifungal combined therapies in experimental pulmonary paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by the Paracoccidioides genus. Most of the patients with chronic form present sequelae, like pulmonary fibrosis, with no effective treatment, leading to impaired lung functions. In the present study, we aimed to investigate the antifibrotic activity of three compounds: pentoxifylline (PTX), azithromycin (AZT), and thalidomide (Thal) in a murine model of pulmonary PCM treated with itraconazole (ITC) or cotrimoxazole (CMX). BALB/c mice were inoculated with P. brasiliensis (Pb) by the intratracheal route and after 8 weeks, they were submitted to one of the following six treatments: PTX/ITC, PTX/CMX, AZT/ITC, AZT/CMX, Thal/ITC, and Thal/CMX. After 8 weeks of treatment, the lungs were collected for determination of fungal burden, production of OH-proline, deposition of reticulin fibers, and pulmonary concentrations of cytokines and growth factors. Pb-infected mice treated with PTX/ITC presented a reduction in the pulmonary concentrations of OH-proline, associated with lower concentrations of interleukin (IL)-6, IL-17, and transforming growth factor (TGF)-β1 and higher concentrations of IL-10 compared to the controls. The Pb-infected mice treated with AZT/CMX exhibited decreased pulmonary concentrations of OH-proline associated with lower levels of TGF-β1, and higher levels of IL-10 compared controls. The mice treated with ITC/Thal and CMX/Thal showed intense weight loss, increased deposition of reticulin fibers, high pulmonary concentrations of CCL3, IFN-γ and VEGF, and decreased concentrations of IL-6, IL-1β, IL-17, and TGF-β1. In conclusion, our findings reinforce the antifibrotic role of PTX only when associated with ITC, and AZT only when associated with CMX, but Thal did not show any action upon addition.

Clinical and microbiological characteristics of paracoccidioidomycosis in patients with AIDS in Buenos Aires, Argentina

Paracoccidioidomycosis (Pm) is a systemic disease, endemic in the American continent. There are two different clinical forms, the infant-juvenile or subacute form (PmS) and the chronic adult form (PmC). The human immunodeficiency virus (HIV) associated paracoccidioidomycosis (PmHIV) shares characteristics with both of the previously mentioned forms. The objective of this work was to describe the epidemiological, clinical and laboratory features of the PmHIV and to compare them with the ones of PmS and the PmC. A retrospective analysis of 119 patients with paracoccidioidomycosis was performed. Ninety four suffered the chronic form, 11 the subacute one and 14 were coinfected with HIV. Patients with PmHIV presented a CD4+ T lymphocytes median of 70.5 cells/μl, 71.4% had fever, 64.3% had a miliary pattern on the chest radiography, 64.3% had hepatosplenomegaly, 64.3% had mucosal lesions and 50% had skin lesions. One patient died during his hospitalization. The clinical presentation of Pm in patients with HIV resembled the subacute form with fever, hepatomegaly and skin lesions. However, they also tended to present mucosal lesions, positive serology for Pm and pulmonary parenchyma lesions as usually seen in PmC (9/14 PmHIV patients had overlapping features, while 4/14 PmHIV patients clinically resembled PmS and 1/14 PmC). The incidence of Pm has not changed with the burden of AIDS as it has happened with other fungal infections but it appears clinically different from the classic clinical forms of the disease.

Secreted aspartyl proteinase (PbSap) contributes to the virulence of Paracoccidioides brasiliensis infection

Paracoccidioidomycosis (PCM) is the most prevalent deep mycosis in Latin America and is caused by fungi from the Paracoccidioides genus. Virulence factors are important fungal characteristics that support the development of disease. Aspartyl proteases (Saps) are virulence factors in many human fungal pathogens that play an important role in the host invasion process. We report here that immunization with recombinant Sap from Paracoccidioides brasiliensis (rPbSap) imparted a protective effect in an experimental PCM model. The rPbSap-immunized mice had decreased fungal loads, and their lung parenchyma were notably preserved. An aspartyl protease inhibitor (pepstatin A) significantly decreased pulmonary injury and reduced fungal loads in the lung. Additionally, we observed that pepstatin A enhanced the fungicidal and phagocytic profile of macrophages against P. brasiliensis. Furthermore, PbSAP expression was highly altered by environmental conditions, including thermal stress, dimorphism switching and low pH. Hence, our data suggest that PbSap is an important virulence regulator in P. brasiliensis.

Current trends to control fungal pathogens: exploiting our knowledge in the host-pathogen interaction

Human fungal infections remain a major challenge in medicine. Only a limited number of antifungal drugs are available, which are often related to severe adverse effects. In addition, there is an increased emergence related to resistant strains, which makes imperative to understand the host-pathogen interactions as well as to develop alternative treatments. Host innate and adaptive immunity play a crucial role controlling fungal infections; therefore, vaccines are a viable tool to prevent and treat fungal pathogens. Innate immunity is triggered by the interaction between the cell surface pattern recognition receptors (PRRs) and the pathogen-associated molecular patterns (PAMPs). Such an initial immunological response is yet little understood in fungal infections, in part due to the complexity and plasticity of the fungal cell walls. Described host cell-fungus interactions and antigenic molecules are addressed in this paper. Furthermore, antigens found in the cell wall and capsule, including peptides, glycoproteins, glycolipids, and glycans, have been used to trigger specific immune responses, and an increased production of antibodies has been observed when attached to immunogenic molecules. The recent biotechnological advances have allowed the development of vaccines against viral and bacterial pathogens with positive results; therefore, this technology has been applied to develop anti-fungal vaccines. Passive immunization has also emerged as an appealing alternative to treat disseminated mycosis, especially in immunocompromised patients. Those approaches have a long way to be seen in clinical cases. However, all studies discussed here open the possibility to have access to new therapies to be applied alone or in combination with current antifungal drugs. Herein, the state of the art of fungal vaccine developments is discussed in this review, highlighting new advances against Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, Paracoccidioides brasiliensis, and Sporothrix spp.

Recombinant vaccines of a CD4+ T-cell epitope promote efficient control of Paracoccidioides brasiliensis burden by restraining primary organ infection

Paracoccidioidomycosis (PCM) is an infectious disease endemic to South America, caused by the thermally dimorphic fungi Paracoccidioides. Currently, there is no effective human vaccine that can be used in prophylactic or therapeutic regimes. We tested the hypothesis that the immunogenicity of the immunodominant CD4+ T-cell epitope (P10) of Paracoccidioides brasiliensis gp43 antigen might be significantly enhanced by using a hepatitis B virus-derived particle (VLP) as an antigen carrier. This chimera was administered to mice as a (His)6-purified protein (rPbT) or a replication-deficient human type 5 adenoviral vector (rAdPbT) in an immunoprophylaxis assay. The highly virulent Pb18 yeast strain was used to challenge our vaccine candidates. Fungal challenge evoked robust P10-specific memory CD4+ T cells secreting protective Th-1 cytokines in most groups of immunized mice. Furthermore, the highest level of fungal burden control was achieved when rAdPbT was inoculated in a homologous prime-boost regimen, with 10-fold less CFU recovering than in non-vaccinated mice. Systemic Pb18 spreading was only prevented when rAdPbT was previously inoculated. In summary, we present here VLP/P10 formulations as vaccine candidates against PCM, some of which have demonstrated for the first time their ability to prevent progression of this pernicious fungal disease, which represents a significant social burden in developing countries.

Therapeutic effect of monophosphoryl lipid A administration on Paracoccidioides brasiliensis-infected mice

The lack of antifungals with low toxicity and short-term therapy for patients with paracoccidioidomycosis (PCM) led us to evaluate adjuvants in immunotherapeutic intervention. We have previously shown complete Freund's adjuvant (CFA) to be therapeutic on experimental PCM. Owing to CFA toxicity, here we tested adjuvants approved for clinical use or in preclinical phase in experimental mouse PCM. Of all, only monophosporyl lipid A (MPLA) demonstrates a beneficial effect, by reducing the fungal burden and increasing the concentrations of IFN-γ and TNF-α, which are immunoprotective in PCM. These results suggest that MPLA might improve intervention in PCM.

Th1-Inducing Agents in Prophylaxis and Therapy for Paracoccidioidomycosis

Adjuvants and immunomodulatory molecules could be included in the treatment of P. brasiliensis infection. In this context, we reported that the therapeutic and/or prophylactic administration of Th1-inducing agents, such as immunomodulatory lectins and adjuvants, was able to provide protection against experimental paracoccidioidomycosis. Then, we described the protocols to investigate the effect of immunomodulatory agents on the course of P. brasiliensis infection. In this sense, we detailed the measurement of fungal burden and cytokine production, and the histopathological analysis used to evaluate the most effective administration regime.

PARACOCCIDIOIDOMYCOSIS: CHALLENGES IN THE DEVELOPMENT OF A VACCINE AGAINST AN ENDEMIC MYCOSIS IN THE AMERICAS

Paracoccidioidomycosis (PCM), caused by Paracoccidioides spp, is an important endemic mycosis in Latin America. There are two recognized Paracoccidioides species, P. brasiliensis and P. lutzii, based on phylogenetic differences; however, the pathogenesis and disease manifestations of both are indistinguishable at present. Approximately 1,853 (~51,2%) of 3,583 confirmed deaths in Brazil due to systemic mycoses from 1996-2006 were caused by PCM. Antifungal treatment is required for patients with PCM. The initial treatment lasts from two to six months and sulfa derivatives, amphotericin B, azoles and terbinafine are used in clinical practice; however, despite prolonged therapy, relapses are still a problem. An effective Th1-biased cellular immune response is essential to control the disease, which can be induced by exogenous antigens or modulated by prophylactic or therapeutic vaccines. Stimulation of B cells or passive transference of monoclonal antibodies are also important means that may be used to improve the efficacy of paracoccidioidomycosis treatment in the future. This review critically details major challenges facing the development of a vaccine to combat PCM.

PARACOCCIDIOIDOMYCOSIS TREATMENT

Considered to be an emerging endemic mycosis in Latin America, paracoccidioidomycosis is characterized by a chronic course and involvement of multiple organs in immunocompromised hosts. Infection sequelae are mainly related to pulmonary and adrenal insufficiency. The host-parasite interaction results in different expressions of the immune response depending on parasite pathogenicity, fungal load and genetic characteristics of the host. A few controlled and case series reports have shown that azoles and fast-acting sulfa derivatives are useful treatment alternatives in milder forms of the disease. For moderate/severe cases, more prolonged treatments or even parenteral routes are required especially when there is involvement of the digestive tract mucosa, resulting in poor drug absorption. Although comparative studies have reported that shorter treatment regimens with itraconazole are able to induce cure in chronically-infected patients, there are still treatment challenges such as the need for more controlled studies involving acute cases, the search for new drugs and combinations, and the search for compounds capable of modulating the immune response in severe cases as well as the paradoxical reactions.

Paracoccidioides-host Interaction: An Overview on Recent Advances in the Paracoccidioidomycosis

Paracoccidioides brasiliensis and P. lutzii are etiologic agents of paracoccidioidomycosis (PCM), an important endemic mycosis in Latin America. During its evolution, these fungi have developed characteristics and mechanisms that allow their growth in adverse conditions within their host through which they efficiently cause disease. This process is multi-factorial and involves host-pathogen interactions (adaptation, adhesion, and invasion), as well as fungal virulence and host immune response. In this review, we demonstrated the glycoproteins and polysaccharides network, which composes the cell wall of Paracoccidioides spp. These are important for the change of conidia or mycelial (26°C) to parasitic yeast (37°C). The morphological switch, a mechanism for the pathogen to adapt and thrive inside the host, is obligatory for the establishment of the infection and seems to be related to pathogenicity. For these fungi, one of the most important steps during the interaction with the host is the adhesion. Cell surface proteins called adhesins, responsible for the first contact with host cells, contribute to host colonization and invasion by mediating this process. These fungi also present the capacity to form biofilm and through which they may evade the host's immune system. During infection, Paracoccidioides spp. can interact with different host cell types and has the ability to modulate the host's adaptive and/or innate immune response. In addition, it participates and interferes in the coagulation system and phenomena like cytoskeletal rearrangement and apoptosis. In recent years, Paracoccidioides spp. have had their endemic areas expanding in correlation with the expansion of agriculture. In response, several studies were developed to understand the infection using in vitro and in vivo systems, including alternative non-mammal models. Moreover, new advances were made in treating these infections using both well-established and new antifungal agents. These included natural and/or derivate synthetic substances as well as vaccines, peptides, and anti-adhesins sera. Because of all the advances in the PCM study, this review has the objective to summarize all of the recent discoveries on Paracoccidioides-host interaction, with particular emphasis on fungi surface proteins (molecules that play a fundamental role in the adhesion and/or dissemination of the fungi to host-cells), as well as advances in the treatment of PCM with new and well-established antifungal agents and approaches.

TLR 9 involvement in early protection induced by immunization with rPb27 against Paracoccidioidomycosis

Paracoccidioidomycosis is caused by fungi of the Paracoccidioides genus and constitutes the most prevalent deep mycosis in Latin America. Toll-like receptors promote immune response against infectious agents. Recently, it was reported that TLR9 is crucial for mice survival during the first 48 h of P. brasiliensis infection. In this study, we used CPG oligodeoxynucleotide motif as an adjuvant with and without rPb27 to immunize mice against Paracoccidioidomycosis. CPG adjuvant induced differential recruitment of lymphocytes in the inflammatory process and a lower recruitment of neutrophils. In addition, CPG induced the production of pro-inflammatory cytokines such as IL-1β, TNF-α, IL-6 and IL-12; increased phagocytic ability and microbicidal activity by macrophages; and induced differential production of lgG2a and lgG2b, subtypes of Ig. Knockout mice for TLR9 and IL-12 showed higher fungal loads and rates of mortality compared to control mice after 30 days of infection. The association between CPG and rPb27 induced a high level of protection against Paracoccidioidomycosis after the first 30 days of infection but not at 60 days. Our findings demonstrate that TLR 9 plays a role in the protection induced by immunization with rPb27 and confirms the importance of TLR9 in the initial protection against Paracoccidioidomycosis.