Mouse Immunization with Radioattenuated Yeast Cells of Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis, the most prevalent mycosis in Latin America, and currently there is no effective vaccine. The present chapter describes the methodology to obtain radioattenuated yeast cells of P. brasiliensis and a protocol to evaluate protective response elicited by this immunogen in experimental paracoccidioidomycosis. The radioattenuated yeast provides a valuable tool for immunological studies in experimental paracoccidioidomycosis and vaccine research.

Photodynamic inactivation of Paracoccidioides brasiliensis helps the outcome of oral paracoccidiodomycosis.

The antifungal drug therapy often employed to treat paracoccidiodomycosis (PCM), an important neglected fungal systemic infection, leads to offensive adverse effects, besides being very long-lasting. In addition, PCM compromises the oral health of patients by leading to oral lesions that are very painful and disabling. In that way, photodynamic therapy (PDT) arises as a new promising adjuvant treatment for inactivating Paracoccidioides brasiliensis (Pb), the responsible fungus for PCM, and also for helping the patients to deal with such debilitating oral lesions. PDT has been linked to an improved microbial killing, also presenting the advantage of not inducing immediate microbial resistance such as drugs. For the present study, we investigated the generation of reactive oxygen species (ROS) by using the fluorescent probes hydroxyphenyl fluorescein (HPF) and aminophenyl fluorescein (APF) after toluidine blue (TBO-37.5 mg/L)-mediated PDT (660 nm, 40 mW, and 0.04 cm2 spot area) and the action of TBO-PDT upon Pb cultures grown for 7 or 15 days in semisolid Fava Netto's culture medium; we also targeted oral PCM manifestations by reporting the first clinical cases (three patients) to receive topic PDT for such purpose. We were able to show a significant generation of hydroxyl radicals and hypochlorite after TBO-PDT with doses around 90 J/cm2; such ROS generation was particularly useful to attack and inactivate Pb colonies at 7 and 15 days. All three patients reported herein related an immediate relief when it came to pain, mouth opening, and also the ability to chew and swallow. As extracted from our clinical results, which are in fact based on in vitro outcomes, TBO-PDT is a very safe, inexpensive, and promising therapy for the oral manifestations of PCM.

Low-level laser therapy to the mouse femur enhances the fungicidal response of neutrophils against Paracoccidioides brasiliensis.

Neutrophils (PMN) play a central role in host defense against the neglected fungal infection paracoccidioidomycosis (PCM), which is caused by the dimorphic fungus Paracoccidioides brasiliensis (Pb). PCM is of major importance, especially in Latin America, and its treatment relies on the use of antifungal drugs. However, the course of treatment is lengthy, leading to side effects and even development of fungal resistance. The goal of the study was to use low-level laser therapy (LLLT) to stimulate PMN to fight Pb in vivo. Swiss mice with subcutaneous air pouches were inoculated with a virulent strain of Pb or fungal cell wall components (Zymosan), and then received LLLT (780 nm; 50 mW; 12.5 J/cm2; 30 seconds per point, giving a total energy of 0.5 J per point) on alternate days at two points on each hind leg. The aim was to reach the bone marrow in the femur with light. Non-irradiated animals were used as controls. The number and viability of the PMN that migrated to the inoculation site was assessed, as well as their ability to synthesize proteins, produce reactive oxygen species (ROS) and their fungicidal activity. The highly pure PMN populations obtained after 10 days of infection were also subsequently cultured in the presence of Pb for trials of protein production, evaluation of mitochondrial activity, ROS production and quantification of viable fungi growth. PMN from mice that received LLLT were more active metabolically, had higher fungicidal activity against Pb in vivo and also in vitro. The kinetics of neutrophil protein production also correlated with a more activated state. LLLT may be a safe and non-invasive approach to deal with PCM infection.

Cell survival and altered gene expression following photodynamic inactivation of Paracoccidioides brasiliensis.

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidioides brasiliensis. Currently, the treatment approach involves the use of antifungal drugs and requires years of medical therapy, which can induce nephrotoxicity and lead to resistance in yeast strains. Photodynamic inactivation (PDI) is a new therapy capable of killing microorganisms via the combination of a nontoxic dye with visible light to generate toxic reactive oxygen species (ROS). We investigated the phototoxic effect of 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (TMPyP), a cationic porphyrin, on the survival of P. brasiliensis following exposure to light. Phototoxicity was found to depend on both the fluence and concentration of the photosensitizer (PS). Although the biological effects of PDI are known, the molecular mechanisms underlying the resultant damage to cells are poorly defined. Therefore, we evaluated the molecular response to PDI-induced oxidative stress by gene transcription analysis. We selected genes associated with the high-osmolarity glycerol (HOG)-mitogen-activated protein kinase (MAPK) pathway and antioxidant enzymes. The genes analyzed were all overexpressed after PDI treatment, suggesting that the oxidative stress generated in our experimental conditions induces antioxidant activity. In addition to PDI-induced gene expression, there was high cell mortality, suggesting that the antioxidant response was not sufficient to avoid fungal mortality.

Effect of HeNe laser irradiation on extracellular matrix deposition and expression of cytokines and chemokines in paracoccidioidomycotic lesions.

Paracoccidioidomycosis is the most prevalent human mycosis in Latin America. Cutaneous lesions are extremely painful and sensitive, and current treatment with antifungal drugs is lengthy and may cause side effects to patients. In this perspective, the helium-neon (HeNe) laser emerges as a novel therapy form due to its ability to heal wounds without changing cell function. In this work, we evaluate the effects of HeNe laser irradiation on extracellular matrix deposition and expression of cytokines and chemokines in cutaneous lesions caused by experimental infection of Balb/c mice. Our results showed decreased levels of pro-inflammatory interleukin (IL)-17 and tumor necrosis factor-alpha, and of anti-inflammatory IL-10 cytokines in lesions exposed to HeNe laser irradiation. Chemokines CCL3 and CXCL10 showed decreased levels in laser-treated lesions, but no significant difference was observed in relation to CCL5 expression. We also detected decreased density of fibronectin and laminin in HeNe laser-treated lesions. Data presented herein support the validity of our previous results suggesting positive effects of HeNe laser in accelerating wound healing in this experimental model. We believe that HeNe laser is a new nonharmful strategy that may be used as adjuvant and/or alternative therapy for improving treatment of paracoccidioidomycotic lesions.

Mice immunization with radioattenuated yeast cells of Paracoccidiodes brasiliensis: influence of the number of immunizations.

Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis, the most prevalent mycosis in Latin America. Up to the moment no vaccine has been reported. The aim of this study was to evaluate the influence of the number of immunizations on the protection elicited by radioattenuated yeast cells of P. brasiliensis. BALB/c mice were divided into two groups that were immunized once (Group 1) or twice (Group 2), respectively. In each group, mice were divided into sub-groups that were challenged 30, 45, or 60 days after the second immunization. Organ colony-forming units (CFUs) was determined 90 days post-challenge. A significant reduction in CFUs recovery was verified in both groups, but it was higher in Group 2. Histologic alterations were observed only in Group 1. The cytokines IL-4, IL-10, and IFN-gamma were produced in mice of Group 1. In Group 2, only IFN-gamma was significantly detected. IgG2a predominance relative to IgG1 was also observed in Group 2. Altogether, our results indicated that mice immunized once developed a mixed Th1/Th2 response, which was less efficient in the infection control, while a trend to a Th1 pattern was obtained with two immunizations, promoting optimal elimination of P. brasiliensis yeast cells from mice tissues.

Ultrastructural changes in Paracoccidioides brasiliensis yeast cells attenuated by gamma irradiation.

Paracoccidioides brasiliensis is a thermally dimorphic fungus agent of paracoccidioidomycosis, a deep-seated systemic infection of humans with high prevalence in Latin America. Until now no vaccine has been reported. Ionizing radiation can be used to attenuate pathogens for vaccine development and we have successfully attenuated yeast cells of P. brasiliensis by gamma irradiation. The aim of the present study was to examine at ultrastructural level the effects of gamma irradiation attenuation on the morphology of P. brasiliensis yeast cells. Paracoccidioides brasiliensis (strain Pb-18) cultures were irradiated with a dose of 6.5 kGy. The irradiated cells were examined by scanning and also transmission electron microscopy. When examined 2 h after the irradiation by scanning electron microscopy, the 6.5 kGy irradiated cells presented deep folds or were collapsed. These lesions were reversible since when examined 48 h after irradiation the yeast had recovered the usual morphology. The transmission electron microscopy showed that the irradiated cells plasma membrane and cell wall were intact and preserved. Remarkable changes were found in the nucleus that was frequently in a very electrondense form. An extensive DNA fragmentation was produced by the gamma irradiation treatment.

Paracoccidioides brasiliensis: attenuation of yeast cells by gamma irradiation.

Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis, the most prevalent mycosis in Latin America, and currently there is no effective vaccine. The aim of this study was to attenuate the yeast form of P. brasiliensis by gamma irradiation for further studies on vaccine research. Paracoccidioides brasiliensis (strain Pb 18) cultures were irradiated at doses between 0.5 and 8.0 kGy. After each dose the viability, reproductive ability and protein metabolism were evaluated. The comparison between the antigenic profile of irradiated and control yeast was made by Western blot and the virulence evaluated by the inoculation in C(57)Bl/J6 mice. At 6.5 kGy the yeast lost its reproductive capacity. The viability and the incorporation of [L-(35)S]-methionine were the same in control and up to 6.5 kGy irradiated cells, but 6.5 kGy-irradiated yeast secreted 40% less proteins. The Western blot profile was clearly similar in control and 6.5 kGy-irradiated yeast. No colony-forming unit (CFU) could be recovered from the tissues of the mice infected with the radioattenuated yeast. We concluded that for P. brasiliensis yeast it is possible to find a dose in which the pathogen loses its reproductive ability and virulence, while retaining its viability, metabolic activity and the antigenic profile.