Carbohydrate-rich high-molecular-mass antigens are strongly recognized during experimental Histoplasma capsulatum infection

Re-Evaluation of the Cross-Reactions of the Antibody against the Causative Agent for Paracoccidioidomycosis Ceti; Paracoccidioides ceti and the Related Fungal Species

Paracoccidioidomycosis ceti (PCM-C) is a chronic granulomatous keloidal dermatitis in cetaceans that has been reported worldwide and is caused by Paracoccidioides ceti. Serological cross-reactions among highly pathogenic fungal infections and related diseases have been reported. However, the true cross-reaction of antibodies against P. ceti has remained unknown due to the use of positive control sera from infected dolphins. This study aimed to re-evaluate antibodies from mechanically dislodged fungal cells in the infected tissue of a PCM-C case and demonstrate the actual cross-reaction. The results revealed a limited cross-reaction between PCM-C and paracoccidioidomycosis, while the antibodies did not react with other pathogens such as Coccidioides posadasii, Histoplasama capsulatum, and Arthrographis kalrae. Thus, the method for evaluation of the antibody against PCM-C is reliable, and there is potential for epidemiological study.

Histoplasma Capsulatum: Mechanisms for Pathogenesis

Histoplasmosis, caused by the dimorphic environmental fungus Histoplasma capsulatum, is a major mycosis on the global stage. Acquisition of the fungus by mammalian hosts can be clinically silent or it can lead to life-threatening systemic disease, which can occur in immunologically intact or deficient hosts, albeit severe disease is more likely in the setting of compromised cellular immunity. H. capsulatum yeast cells are highly adapted to the mammalian host as they can effectively survive within intracellular niches in select phagocytic cells. Understanding the biological response by both the host and H. capsulatum will facilitate improved approaches to prevent and/or modify disease. This review presents our current understanding of the major pathogenic mechanisms involved in histoplasmosis.

Prostaglandins D2 and E2 have opposite effects on alveolar macrophages infected with Histoplasma capsulatum

Prostaglandin E₂ (PGE₂) suppresses macrophage effector mechanisms; however, little is known about the function of PGD₂ in infected alveolar macrophages (AMs). Using serum-opsonized Histoplasma capsulatum (Ops-H. capsulatum) in vitro, we demonstrated that AMs produced PGE₂ and PGD₂ in a time-dependent manner, with PGE₂ levels exceeding those of PGD₂ by 48 h postinfection. Comparison of the effects of both exogenous PGs on AMs revealed that PGD₂ increased phagocytosis and killing through the chemoattractant receptor-homologous molecule expressed on Th2 lymphocytes receptor, whereas PGE₂ had opposite effects, through E prostanoid (EP) receptor 2 (EP2)/EP4-dependent mechanisms. Moreover, PGD₂ inhibited phospholipase C-γ (PLC-γ) phosphorylation, reduced IL-10 production, and increased leukotriene B4 receptor expression. In contrast, exogenous PGE₂ treatment reduced PLC-γ phosphorylation, p38 and nuclear factor κB activation, TNF-α, H₂O₂, and leukotriene B₄, but increased IL-1β production. Using specific compounds to inhibit the synthesis of each PG in vitro and in vivo, we found that endogenous PGD₂ contributed to fungicidal mechanisms and controlled inflammation, whereas endogenous PGE₂ decreased phagocytosis and killing of the fungus and induced inflammation. These findings demonstrate that, although PGD₂ acts as an immunostimulatory mediator to control H. capsulatum infection, PGE₂ has immunosuppressive effects, and the balance between these two PGs may limit collateral immune damage at the expense of microbial containment.

Usefulness of the murine model to study the immune response against Histoplasma capsulatum infection

The present paper is an overview of the primary events that are associated with the histoplasmosis immune response in the murine model. Valuable data that have been recorded in the scientific literature have contributed to an improved understanding of the clinical course of this systemic mycosis, which is caused by the dimorphic fungus Histoplasma capsulatum. Data must be analyzed carefully, given that misinterpretation could be generated because most of the available information is based on experimental host-parasite interactions that used inappropriate proceedings, i.e., the non-natural route of infection with the parasitic and virulent fungal yeast-phase, which is not the usual infective phase of the etiological agent of this mycosis. Thus, due to their versatility, complexity, and similarities with humans, several murine models have played a fundamental role in exploring the host-parasite interaction during H. capsulatum infection.