Facebook Twitter

Gregory Gauthier

Picture of Gregory GauthierAssociate Professor of Medicine, CHS
3472 Microbial Sciences Building
1550 Linden Drive
Office: (608) 265-0429
Laboratory: (608) 265-3352
Email: gmgauthier@wisc.edu
Overview · Personnel · Publications
  • McBride JA, Gauthier GM, Klein BS (2018) Turning on Virulence: Mechanisms that underpin the Morphologic Transition and Pathogenicity of Blastomyces. Virulence :1-24 View Abstract · Pubmed Record

    This review article focuses on the mechanisms underlying temperature adaptation and virulence of the etiologic agents of blastomycosis, Blastomyces dermatitidis, Blastomyces gilchristii, and Blastomyces percursus. In response to temperature, Blastomyces undergoes a reversible morphologic switch between hyphae and yeast known as the phase transition. The conversion to yeast for Blastomyces and related thermally dimorphic fungi is essential for virulence. In the yeast phase, Blastomyces upregulates the essential virulence factor, BAD1, which promotes attachment to host cells, impairs activation of immune cells, and blunts cytokine release. Blastomyces yeast also secrete dipeptidyl-peptidase IVA (DPPIVA), a serine protease that blunts the action of cytokines released from host immune cells. In vivo transcriptional profiling of Blastomyces yeast has uncovered genes such as PRA1 and ZRT1 involved in zinc scavenging that contribute to virulence during murine pulmonary infection. The discovery and characterization of genes important for virulence has led to advances at the bedside regarding novel diagnostics, vaccine development, and new targets for drug discovery.

  • McBride JA, Gauthier GM, Klein BS (2017) Clinical Manifestations and Treatment of Blastomycosis. Clin. Chest Med. 38(3):435-449 (PMC5657236) View Abstract · Pubmed Record

    The causal agents of blastomycosis, Blastomyces dermatitidis and Blastomyces gilchristii, belong to a group of thermally dimorphic fungi that can infect healthy and immunocompromised individuals. Following inhalation of mycelial fragments and spores into the lungs, Blastomyces spp convert into pathogenic yeast and evade host immune defenses to cause pneumonia and disseminated disease. The clinical spectrum of pulmonary blastomycosis is diverse. The diagnosis of blastomycosis requires a high degree of clinical suspicion and involves culture-based and non-culture-based fungal diagnostic tests. The site and severity of infection, and the presence of underlying immunosuppression or pregnancy, influence the selection of antifungal therapy.

  • Lacerda Pigosso L, Baeza LC, Vieira Tomazett M, Batista Rodrigues Faleiro M, Brianezi Dignani de Moura VM, Melo Bailão A, Borges CL, Alves Parente Rocha J, Rocha Fernandes G, Gauthier GM, Soares CMA (2017) Paracoccidioides brasiliensis presents metabolic reprogramming and secretes a serine proteinase during murine infection. Virulence 8(7):1417-1434 (PMC5711425) View Abstract · Pubmed Record

    Paracoccidoides brasiliensis and Paracoccidioides lutzii, the etiologic agents of paracoccidioidomycosis, cause disease in healthy and immunocompromised persons in Latin America. We developed a method for harvesting P. brasiliensis yeast cells from infected murine lung to facilitate in vivo transcriptional and proteomic profiling. P. brasiliensis harvested at 6 h post-infection were analyzed using RNAseq and LC-MS. In vivo yeast cells had 594 differentially expressed transcripts and 350 differentially expressed proteins. Integration of transcriptional and proteomic data indicated that early in infection (6 h), P. brasiliensis yeast cells underwent a shift in metabolism from glycolysis to β-oxidation, upregulated detoxifying enzymes to defend against oxidative stress, and repressed cell wall biosynthesis. Bioinformatics and functional analyses also demonstrated that a serine proteinase was upregulated and secreted in vivo. To our knowledge this is the first study depicting transcriptional and proteomic data of P. brasiliensis yeast cells upon 6 h post-infection of mouse lung.

  • Gauthier GM (2017) Fungal Dimorphism and Virulence: Molecular Mechanisms for Temperature Adaptation, Immune Evasion, and In Vivo Survival. Mediators Inflamm. 2017:8491383 (PMC5463121) View Abstract · Pubmed Record

    The thermally dimorphic fungi are a unique group of fungi within the Ascomycota phylum that respond to shifts in temperature by converting between hyphae (22-25°C) and yeast (37°C). This morphologic switch, known as the phase transition, defines the biology and lifestyle of these fungi. The conversion to yeast within healthy and immunocompromised mammalian hosts is essential for virulence. In the yeast phase, the thermally dimorphic fungi upregulate genes involved with subverting host immune defenses. This review highlights the molecular mechanisms governing the phase transition and recent advances in how the phase transition promotes infection.

  • Brennan MB, Herwaldt BL, Kazmierczak JJ, Weiss JW, Klein CL, Leith CP, He R, Oberley MJ, Tonnetti L, Wilkins PP, Gauthier GM (2016) Transmission of Babesia microti Parasites by Solid Organ Transplantation. Emerging Infect. Dis. 22(11): (PMC5088010) View Abstract · Pubmed Record

    Babesia microti, an intraerythrocytic parasite, is tickborne in nature. In contrast to transmission by blood transfusion, which has been well documented, transmission associated with solid organ transplantation has not been reported. We describe parasitologically confirmed cases of babesiosis diagnosed ≈8 weeks posttransplantation in 2 recipients of renal allografts from an organ donor who was multiply transfused on the day he died from traumatic injuries. The organ donor and recipients had no identified risk factors for tickborne infection. Antibodies against B. microti parasites were not detected by serologic testing of archived pretransplant specimens. However, 1 of the organ donor's blood donors was seropositive when tested postdonation and had risk factors for tick exposure. The organ donor probably served as a conduit of Babesia parasites from the seropositive blood donor to both kidney recipients. Babesiosis should be included in the differential diagnosis of unexplained fever and hemolytic anemia after blood transfusion or organ transplantation.

  • Muñoz JF, Gauthier GM, Desjardins CA, Gallo JE, Holder J, Sullivan TD, Marty AJ, Carmen JC, Chen Z, Ding L, Gujja S, Magrini V, Misas E, Mitreva M, Priest M, Saif S, Whiston EA, Young S, Zeng Q, Goldman WE, Mardis ER, Taylor JW, McEwen JG, Clay OK, Klein BS, Cuomo CA (2015) The Dynamic Genome and Transcriptome of the Human Fungal Pathogen Blastomyces and Close Relative Emmonsia. PLoS Genet. 11(10):e1005493 (PMC4595289) View Abstract · Pubmed Record

    Three closely related thermally dimorphic pathogens are causal agents of major fungal diseases affecting humans in the Americas: blastomycosis, histoplasmosis and paracoccidioidomycosis. Here we report the genome sequence and analysis of four strains of the etiological agent of blastomycosis, Blastomyces, and two species of the related genus Emmonsia, typically pathogens of small mammals. Compared to related species, Blastomyces genomes are highly expanded, with long, often sharply demarcated tracts of low GC-content sequence. These GC-poor isochore-like regions are enriched for gypsy elements, are variable in total size between isolates, and are least expanded in the avirulent B. dermatitidis strain ER-3 as compared with the virulent B. gilchristii strain SLH14081. The lack of similar regions in related species suggests these isochore-like regions originated recently in the ancestor of the Blastomyces lineage. While gene content is highly conserved between Blastomyces and related fungi, we identified changes in copy number of genes potentially involved in host interaction, including proteases and characterized antigens. In addition, we studied gene expression changes of B. dermatitidis during the interaction of the infectious yeast form with macrophages and in a mouse model. Both experiments highlight a strong antioxidant defense response in Blastomyces, and upregulation of dioxygenases in vivo suggests that dioxide produced by antioxidants may be further utilized for amino acid metabolism. We identify a number of functional categories upregulated exclusively in vivo, such as secreted proteins, zinc acquisition proteins, and cysteine and tryptophan metabolism, which may include critical virulence factors missed before in in vitro studies. Across the dimorphic fungi, loss of certain zinc acquisition genes and differences in amino acid metabolism suggest unique adaptations of Blastomyces to its host environment. These results reveal the dynamics of genome evolution and of factors contributing to virulence in Blastomyces.

  • Marty AJ, Broman AT, Zarnowski R, Dwyer TG, Bond LM, Lounes-Hadj Sahraoui A, Fontaine J, Ntambi JM, KeleÅ (2015) Fungal Morphology, Iron Homeostasis, and Lipid Metabolism Regulated by a GATA Transcription Factor in Blastomyces dermatitidis. PLoS Pathog. 11(6):e1004959 (PMC4482641) View Abstract · Pubmed Record

    In response to temperature, Blastomyces dermatitidis converts between yeast and mold forms. Knowledge of the mechanism(s) underlying this response to temperature remains limited. In B. dermatitidis, we identified a GATA transcription factor, SREB, important for the transition to mold. Null mutants (SREBΔ) fail to fully complete the conversion to mold and cannot properly regulate siderophore biosynthesis. To capture the transcriptional response regulated by SREB early in the phase transition (0-48 hours), gene expression microarrays were used to compare SREBâ

  • Gauthier GM (2015) Dimorphism in fungal pathogens of mammals, plants, and insects. PLoS Pathog. 11(2):e1004608 (PMC4335504) View Abstract · Pubmed Record
  • Schmutz JS, Ramey NA, Gauthier GM, Lucarelli MJ (2014) Severe Oculofacial Sequelae of Cutaneous Blastomyces dermatitidis. Ophthal Plast Reconstr Surg 32(3):e61-2 View Abstract · Pubmed Record

    This study reports a case of Blastomyces dermatitidis soft tissue infection resulting in a disfiguring lower eyelid ectropion from cicatricial and postinflammatory cutaneous changes. Primary treatment included intravenous amphotericin B followed by long-term oral itraconazole, which resulted in complete remission of the disease without debridement, after which cicatricial ectropion was repaired surgically with scar release, full-thickness skin graft, and temporary Frost tarsorraphy. Cutaneous blastomycosis may cause severe oculofacial sequelae, ranging from eyelid ectropion to widespread facial cicatrix, and may mimic other more common infectious processes, in addition to malignancy. Recommended antifungal therapy includes induction with intravenous amphotericin B and a long course of oral antifungals, preferably coordinated in conjunction with an infectious disease specialist. Ectropion repair should be delayed until the inflammatory response has completely healed. If the ocular surface is compromised or nearby ocular structures are threatened, primary debridement and repair may be indicated.

  • Barocas JA, Gauthier GM (2014) Peritonitis caused by Blastomyces dermatitidis in a kidney transplant recipient: case report and literature review. Transpl Infect Dis 16(4):634-41 View Abstract · Pubmed Record

    Blastomyces dermatitidis is a dimorphic fungus endemic to the midwestern, south-central, and southeastern United States known to cause disseminated infection in immunocompromised individuals. We report a case of B. dermatitidis peritonitis in a renal allograft recipient with new-onset ascites and cytomegalovirus encephalitis. Peritoneal blastomycosis is a rare clinical entity and, to our knowledge, this patient represents the first known case of peritoneal blastomycosis in a solid organ transplant recipient. We review the clinical characteristics of B. dermatitidis peritonitis as well as the literature on fungal peritonitis with emphasis on dimorphic fungal pathogens. Clinical features suggestive of fungal peritonitis include new-onset ascites, abdominal pain, and fevers, especially with antecedent or concomitant pneumonia. A high index of clinical suspicion, along with the use of culture and non-culture diagnostics, is needed for early diagnosis and prompt initiation of therapy.

  • Silva-Bailão MG, Bailão EF, Lechner BE, Gauthier GM, Lindner H, Bailão AM, Haas H, de Almeida Soares CM (2014) Hydroxamate production as a high affinity iron acquisition mechanism in Paracoccidioides spp. PLoS ONE 9(8):e105805 (PMC4144954) View Abstract · Pubmed Record

    Iron is a micronutrient required by almost all living organisms, including fungi. Although this metal is abundant, its bioavailability is low either in aerobic environments or within mammalian hosts. As a consequence, pathogenic microorganisms evolved high affinity iron acquisition mechanisms which include the production and uptake of siderophores. Here we investigated the utilization of these molecules by species of the Paracoccidioides genus, the causative agents of a systemic mycosis. It was demonstrated that iron starvation induces the expression of Paracoccidioides ortholog genes for siderophore biosynthesis and transport. Reversed-phase HPLC analysis revealed that the fungus produces and secretes coprogen B, which generates dimerumic acid as a breakdown product. Ferricrocin and ferrichrome C were detected in Paracoccidioides as the intracellular produced siderophores. Moreover, the fungus is also able to grow in presence of siderophores as the only iron sources, demonstrating that beyond producing, Paracoccidioides is also able to utilize siderophores for growth, including the xenosiderophore ferrioxamine. Exposure to exogenous ferrioxamine and dimerumic acid increased fungus survival during co-cultivation with macrophages indicating that these molecules play a role during host-pathogen interaction. Furthermore, cross-feeding experiments revealed that Paracoccidioides siderophores promotes growth of Aspergillus nidulans strain unable to produce these iron chelators. Together, these data denote that synthesis and utilization of siderophores is a mechanism used by Paracoccidioides to surpass iron limitation. As iron paucity is found within the host, siderophore production may be related to fungus pathogenicity.

  • Gauthier GM, Keller NP (2013) Crossover fungal pathogens: the biology and pathogenesis of fungi capable of crossing kingdoms to infect plants and humans. Fungal Genet. Biol. 61:146-57 View Abstract · Pubmed Record

    The outbreak of fungal meningitis associated with contaminated methylprednisolone acetate has thrust the importance of fungal infections into the public consciousness. The predominant pathogen isolated from clinical specimens, Exserohilum rostratum (teleomorph: Setosphaeria rostrata), is a dematiaceous fungus that infects grasses and rarely humans. This outbreak highlights the potential for fungal pathogens to infect both plants and humans. Most crossover or trans-kingdom pathogens are soil saprophytes and include fungi in Ascomycota and Mucormycotina phyla. To establish infection, crossover fungi must overcome disparate, host-specific barriers, including protective surfaces (e.g. cuticle, skin), elevated temperature, and immune defenses. This review illuminates the underlying mechanisms used by crossover fungi to cause infection in plants and mammals, and highlights critical events that lead to human infection by these pathogens. Several genes including veA, laeA, and hapX are important in regulating biological processes in fungi important for both invasive plant and animal infections.

  • Marty AJ, Wüthrich M, Carmen JC, Sullivan TD, Klein BS, Cuomo CA, Gauthier GM (2013) Isolation of Blastomyces dermatitidis yeast from lung tissue during murine infection for in vivo transcriptional profiling. Fungal Genet. Biol. 56:1-8 (PMC3696400) View Abstract · Pubmed Record

    Blastomyces dermatitidis belongs to a group of thermally dimorphic fungi that grow as sporulating mold in the soil and convert to pathogenic yeast in the lung following inhalation of spores. Knowledge about the molecular events important for fungal adaptation and survival in the host remains limited. The development of high-throughput analytic tools such as RNA sequencing (RNA-Seq) has potential to provide novel insight on fungal pathogenesis especially if applied in vivo during infection. However, in vivo transcriptional profiling is hindered by the low abundance of fungal cells relative to mammalian tissue and difficulty in isolating fungal cells from the tissues they infect. For the purpose of obtaining B. dermatitidis RNA for in vivo transcriptional analysis by RNA-Seq, we developed a simple technique for isolating yeast from murine lung tissue. Using a two-step approach of filtration and centrifugation following lysis of murine lung cells, 91% of yeast cells causing infection were isolated from lung tissue. B. dermatitidis recovered from the lung yielded high-quality RNA with minimal murine contamination and was suitable for RNA-Seq. Approximately 87% of the sequencing reads obtained from the recovered yeast aligned with the B. dermatitidis genome. This was similar to 93% alignment for yeast grown in vitro. The use of near-freezing temperature along with short ex vivo time minimized transcriptional changes that would have otherwise occurred with higher temperature or longer processing time. In conclusion, we have developed a technique that recovers the majority of yeast causing pulmonary infection and yields high-quality fungal RNA with minimal contamination by mammalian RNA.

  • Marty AJ, Gauthier GM (2013) Blastomyces dermatitidis septins CDC3, CDC10, and CDC12 impact the morphology of yeast and hyphae, but are not required for the phase transition. Med. Mycol. 51(1):93-102 (PMC3607453) View Abstract · Pubmed Record

    Blastomyces dermatitidis, the etiologic agent of blastomycosis, belongs to a group of thermally dimorphic fungi that change between mold (22°C) and yeast (37°C) in response to temperature. The contribution of structural proteins such as septins to this phase transition in these fungi remains poorly understood. Septins are GTPases that serve as a scaffold for proteins involved with cytokinesis, cell polarity, and cell morphology. In this study, we use a GFP sentinel RNA interference system to investigate the impact of CDC3, CDC10, CDC12, and ASPE on the morphology and phase transition of B. dermatitidis. Targeting CDC3, CDC10, and CDC12 by RNA interference resulted in yeast with aberrant morphology at 37°C with defects in cytokinesis. Downshifting the temperature to 22°C promoted the conversion to the mold phase, but did not abrogate the morphologic defects. CDC3, CDC10, and CDC12 knockdown strains grew as mold with curved, thickened hyphae. Knocking down ASPE transcript did not alter morphology of yeast at 37°C or mold at 22°C. Following an increase in temperature from 22°C to 37°C, all septin knockdown strains were able to revert to yeast. In conclusion, CDC3, CDC10, and CDC12 septin- encoding genes are required for proper morphology of yeast and hyphae, but are dispensable for the phase transition.