In the study of fungal pathogenesis, alternative methods have gained prominence due to recent global legislation restricting the use of mammalian animals in research. The principle of the 3 Rs (replacement, reduction, and refinement) is integrated into regulations and guidelines governing animal experimentation in nearly all countries. This principle advocates substituting vertebrate animals with other invertebrate organisms, embryos, microorganisms, or cell cultures. This review addresses host–fungus interactions by employing three-dimensional (3D) cultures, which offer more faithful replication of the in vivo environment, and by utilizing alternative animal models to replace traditional mammals. Among these alternative models, species like Caenorhabditis elegans and Danio rerio share approximately 75% of their genes with humans. Furthermore, models such as Galleria mellonella and Tenebrio molitor demonstrate similarities in their innate immune systems as well as anatomical and physiological barriers, resembling those found in mammalian organisms.

Organoboron compounds, especially those containing boronic acid and benzoxaborole in their structure, have been gaining prominence in medicinal chemistry, following the FDA approval of tavaborole for the treatment of onychomycosis and bortezomib for multiple myeloma. The antimicrobial and anticancer effects of organoboron compounds motivate the investigation of the effects of the novel derivatives described here. A total of fourteen new boronic derivatives were synthesized and characterized using analytical methods. The antimicrobial activities were evaluated against M. tuberculosis (Mtb) H37Rv strains and fungal dermatophytes (C. albicans, ATCC 90028; T. rubrum, ATCC 28189; and T. mentagrophytes, ATCC 11481), while the anticancer effect was evaluated against oral squamous cell carcinoma (SCC) cell lines. Several promising boron-containing prototypes were identified, providing a foundation for further molecular optimization in the development of new antimicrobial and anticancer compounds.

Vulvovaginal candidiasis (VVC) remains a prevalent fungal disease, characterized by challenges, such as increased fungal resistance, side effects of current treatments, and the rising prevalence of non-albicans Candida spp. naturally more resistant. This study aimed to propose a novel therapeutic approach by investigating the antifungal properties and toxicity of 2-hydroxychalcone (2-HC) and 3′-hydroxychalcone (3′-HC), both alone and in combination with fluconazole (FCZ) and clotrimazole (CTZ). A lipid carrier (LC) was also developed to deliver these molecules. The study evaluated in vitro anti-Candida activity against five Candida species and assessed cytotoxicity in the C33-A cell line. The safety and therapeutic efficacy of in vivo were tested using an alternative animal model, Galleria mellonella. The results showed antifungal activity of 2-HC and 3′-HC, ranging from 7.8 to 31.2 as fungistatic and 15.6 to 125.0 mg/L as fungicide effect, with cell viability above 80% from a concentration of 9.3 mg/L (2-HC). Synergistic and partially synergistic interactions of these chalcones with FCZ and CTZ demonstrated significant improvement in antifungal activity, with MIC values ranging from 0.06 to 62.5 mg/L. Some combinations reduced cytotoxicity, achieving 100% cell viability in many interactions. Additionally, two LCs with suitable properties for intravaginal application were developed. These formulations demonstrated promising therapeutic efficacy and low toxicity in Galleria mellonella assays. These results suggest the potential of this approach in developing new therapies for VVC.

Over the last two decades, the incidence of Invasive Fungal Infections (IFIs) globally has risen, posing a considerable challenge despite available antifungal therapies. Addressing this, the World Health Organization (WHO) prioritized research on specific fungi, notably Histoplasma spp. and Paracoccidioides spp. These dimorphic fungi have a mycelial life cycle in soil and a yeast phase associated with tissues of mammalian hosts. Inhalation of conidia and mycelial fragments initiates the infection, crucially transforming into the yeast form within the host, influenced by factors like temperature, host immunity, and hormonal status. Survival and multiplication within alveolar macrophages are crucial for disease progression, where innate immune responses play a pivotal role in overcoming physical barriers. The transition to pathogenic yeast, triggered by increased temperature, involves yeast phase-specific gene expression, closely linked to infection establishment and pathogenicity. Cell adhesion mechanisms during host-pathogen interactions are intricately linked to fungal virulence, which is critical for tissue colonization and disease development. Yeast replication within macrophages leads to their rupture, aiding pathogen dissemination. Immune cells, especially macrophages, dendritic cells, and neutrophils, are key players during infection control, with macrophages crucial for defense, tissue integrity, and pathogen elimination. Recognition of common virulence molecules such as heat- shock protein-60 (Hsp60) and enolase by pattern recognition receptors (PRRs), mainly via the complement receptor 3 (CR3) and plasmin receptor pathways, respectively, could be pivotal in host-pathogen interactions for Histoplasma spp. and Paracoccidioides spp., influencing adhesion, phagocytosis, and inflammatory regulation. This review provides a comprehensive overview of the dynamic of these two IFIs between host and pathogen. Further research into these fungi's virulence factors promises insights into pathogenic mechanisms, potentially guiding the development of effective treatment strategies.

The 14-3-3 protein in dimorphic fungi from the Ajellomycetaceae family, including Blastomyces spp., Histoplasma spp., Paracoccidioides spp., Emergomyces spp., and Emmonsia spp., play a crucial role in host-pathogen interactions. Thus, we performed a comparative genomic analysis across 21 fungal species which revealed the presence of two 14-3-3 gene copies in most fungi, with exceptions in Histoplasma ohiense and Emergomyces africanus which revealed one and three gene copies, respectively. Moreover, in this study it was found a high degree of similarity (over 70%) between fungal 14-3-3 proteins and the human 14-3-3ɛ isoform, particularly in conserved Ser/Thr phosphorylation sites. However, distinct differences were noted in the C- and N-terminal regions, where fungal 14-3-3 proteins have additional amino acids. Though not directly linked to pathogenicity, these structural differences may offer insights into new therapeutic strategies. The conserved regions and 3D similarities identified could serve as potential targets for broad-spectrum antifungal drug development and vaccine production. Further research is necessary to validate these in silico findings and explore the functional roles of these phosphorylation sites, which could contribute to understanding fungal pathogenicity and developing specific antifungal interventions.

Cryptococcosis is a systemic mycosis affecting immunocompromised individuals (mainly C. neoformans ) and immunocompetent hosts (mainly C. gattii ). Effective treatment remains challenging due to antifungal resistance, driven by efflux pumps, target enzyme mutations, biofilm formation, and persister cells. This study evaluated efflux pump gene expression and its role in biofilm development and resistance in persister cells of both species, as well as the effects of combined treatments—fluconazole + FK506 and fluconazole + octyl protocatechuate—on biofilms. Materials and Methods included microscopy, biofilm characterization during formation, treatment assays, induction of persister cells, and relative quantification of efflux pump genes AFR1 , AFR2 , AFR3 , and MDR1 . Biofilms of both species were robust, with increased extracellular matrix linked to efflux pump overexpression. Combined treatments reduced biofilm growth and extracellular matrix production while downregulating AFR1 , AFR2 , AFR3 , and MDR1 , highlighting a link between efflux pumps and matrix export. Persister cells displayed low metabolic activity under amphotericin B treatment, followed by slow regrowth and reactivation of efflux pumps. These findings demonstrate multifaceted roles of efflux pumps in antifungal resistance and biofilm development, confirm the presence of persister cells in C. neoformans and C. gattii , and suggest novel therapeutic strategies for cryptococcosis. IMPORTANCE: Cryptococcosis is a fungal infection with mortality exceeding 75%, predominantly affecting immunocompromised individuals—including transplant recipients and people living with HIV—but also capable of infecting healthy people. Treatments are lengthy, toxic, and increasingly ineffective due to antifungal resistance. Two major contributors to therapeutic failure are biofilms—protective fungal communities encased in a self-produced matrix—and persister cells, a dormant subpopulation that survives lethal drug concentrations and reactivates infection once treatment stops. This study reveals that efflux pumps—proteins that expel drugs from fungal cells—are not only resistance mechanisms but also active contributors to biofilm construction. Critically, persister cells reactivate their efflux pumps upon recovery, providing a biological explanation for infection recurrence. Two drug combinations—fluconazole + FK506 and fluconazole + octyl protocatechuate—synergistically disrupted biofilms and reduced persister cell viability while potentially lowering drug doses and toxicity, pointing toward safer, more effective strategies for cryptococcosis.