The Pathophysiology and Treatment of Candida Sepsis

Clinical features, diagnosis and treatment outcome of fungal endocarditis: A systematic review of reported cases

The landscape of fungal endocarditis (FE) has constantly been evolving in the last few decades. Despite the advancement in diagnostic methods and the introduction of newer antifungals, mortality remains high in FE. This systematic review aimed to evaluate the epidemiology, clinical features, diagnostic and therapeutic interventions in patients with FE. We also aim to examine the aforementioned factors as a determinant of mortality in FE. A literature search was performed in PubMed, Google Scholar and Scopus, and all patients ≥18 years with proven fungal endocarditis were included. A total of 220 articles (250 patients) were included in the final analysis. Candida was the commonest aetiology (49.6%), followed by Aspergillus (30%) and Scedosporium species (3.2%). The proportion of prosthetic valve endocarditis (PVE) and intravenous drug users was 35.2% and 16%, respectively. The overall mortality rate was 40%. On multivariate analysis, Aspergillus endocarditis (HR 3.7, 95% CI 1.4-9.7; p = .009) and immunocompromised state (HR 2.8, 95% CI 1.24-6.3; p = .013) were independently associated with mortality. Patients treated with surgery along antifungals had better survival (HR 0.20, 95% CI 0.09-0.42; p < .001) compared to those treated with antifungals alone. Recurrence of FE was reported in 10.4% of patients. In conclusion, FE carries significant mortality, particularly in immunodeficient and Aspergillus endocarditis. We advocate the use of surgery combined with antifungals to improve clinical outcomes.

Irisin attenuates lipopolysaccharide-induced acute lung injury by downregulating inflammatory cytokine expression through miR-199a-mediated Rad23b overexpression

AIMS

Acute lung injury (ALI) is a leading cause of mortality as a result of inflammatory cytokine overexpression and increased rates of apoptosis. Therapies for ALI are yet to be thoroughly investigated. Recent evidence has shown that irisin exerts protective effects against many types of pathologies. The present study aimed to determine the function of irisin in an ALI mouse model induced by lipopolysaccharide (LPS) and the corresponding underlying mechanisms at the tissue, cellular, and molecular levels.

MAIN METHODS

We assessed irisin function in A549 cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. The cell apoptosis was evaluated by flow cytometry. Western blotting and RT-PCR were used to test expression level. Animal models of ALI was established.

KEY FINDINGS

We found that irisin treatment maintained lung weight, significantly reduced inflammatory cytokine expression, and alleviated lung injury by downregulating miR-199a. In LPS-stimulated cells, forced miR-199a expression downregulated Rad23b expression by targeting its 3' untranslated region, indicating that Rad23b is a direct target of miR-199a.

SIGNIFICANCE

These findings reveal that irisin can alleviate ALI by inhibiting miR-199a and upregulating Rad23b expression, suggesting that irisin has clinical potential for the treatment of ALI.

Candida albicans endocarditis involving a normal native aortic valve in an immunocompetent patient

Fungal endocarditis, specifically from Candida species, is a rare but serious infection with a high mortality rate. Most cases occur in bioprosthetic or mechanical valves and are uncommon in native, structurally normal valves. When Candida endocarditis is detected and appropriate treatment is initiated earlier, there is an improvement in mortality. While the recommendation is usually to treat with a combination of surgery and antifungal medications, patient comorbidities may limit treatment options.

Seselin ameliorates inflammation via targeting Jak2 to suppress the proinflammatory phenotype of macrophages

BACKGROUND AND PURPOSE

Sepsis is a serious clinical condition with a high mortality rate. Anti inflammatory agents have been found to be beneficial for the treatment of sepsis. Here, we have evaluated the anti-inflammatory activity of seselin in models of sepsis and investigated the underlying molecular mechanism(s).

EXPERIMENTAL APPROACH

In vivo therapeutic effects of seselin was evaluated in two models of sepsis, caecal ligation and puncture or injection of LPS, in C57BL/6 mice. In vitro, anti-inflammatory activity of seselin was assessed with macrophages stimulated with LPS and IFN-γ. Anti inflammatory actions were analysed with immunohistochemical methods, ELISA and Western blotting. Flow cytometry was used to assess markers of macrophage phenotype (pro- or anti-inflammatory). Other methods used included co-immunoprecipitation, cellular thermal shift assay and molecular docking.

KEY RESULTS

In vivo, seselin clearly ameliorated sepsis induced by caecal ligation and puncture. In lung tissue from septic mice and in cultured macrophages, seselin down-regulated levels of proinflammatory factors and activity of STAT1 and p65, the master signal pathway molecules for polarization of macrophages into the proinflammatory phenotype. Importantly, adoptive transfer of bone marrow-derived macrophages, pretreated with seselin, lowered systemic proinflammatory factors in mice challenged with LPS. The underlying mechanism was that seselin targeted Jak2 to block interaction with IFNγ receptors and downstream STAT1.

CONCLUSIONS AND IMPLICATIONS

Seselin exhibited anti-inflammatory activity through its action on Jak2. These results indicated a possible application of seselin to the treatment of inflammatory disease via blocking the development of the proinflammatory phenotype of macrophages.

Inhibiting the immunoproteasome exacerbates the pathogenesis of systemic Candida albicans infection in mice

Apart from its role in MHC class I antigen processing, the immunoproteasome has recently been implicated in the modulation of T helper cell differentiation under polarizing conditions in vitro and in the pathogenesis of autoimmune diseases in vivo. In this study, we investigated the influence of LMP7 on T helper cell differentiation in response to the fungus Candida albicans. We observed a strong effect of ONX 0914, an LMP7-selective inhibitor of the immunoproteasome, on IFN-γ and IL-17A production by murine splenocytes and human peripheral blood mononuclear cells (PBMCs) stimulated with C. albicans in vitro. Using a murine model of systemic candidiasis, we could confirm reduced generation of IFN-γ- and IL-17A-producing cells in ONX 0914 treated mice in vivo. Interestingly, ONX 0914 treatment resulted in increased susceptibility to systemic candidiasis, which manifested at very early stages of infection. Mice treated with ONX 0914 showed markedly increased kidney and brain fungal burden which resulted in enhanced neutrophil recruitment and immunopathology. Together, these results strongly suggest a role of the immunoproteasome in promoting proinflammatory T helper cells in response to C. albicans but also in affecting the innate antifungal immunity in a T helper cell-independent manner.

Recalcitrant prosthetic valve endocarditis requiring repeated reconstruction: running out of options

In this report we describe a previously healthy 36-year-old man who presented with septic shock secondary to bacterial endocarditis with multiple cerebral, mesenteric, and peripheral embolic phenomena. He underwent emergent porcine prosthetic valve replacement with aortic annular reconstruction. Subsequently, he developed recalcitrant Candida parapsilosis endocarditis requiring treatment with multiple antifungal agents and 4 repeated complex reconstructions of the aortic root and fibrous trigones over 3 years, before the infection was successfully controlled. This case underscores the significant morbidity associated with fungal endocarditis and importance of an early combined medical and surgical approach.

Endogenous thrombospondin-1 regulates leukocyte recruitment and activation and accelerates death from systemic candidiasis

Disseminated Candida albicans infection results in high morbidity and mortality despite treatment with existing antifungal drugs. Recent studies suggest that modulating the host immune response can improve survival, but specific host targets for accomplishing this goal remain to be identified. The extracellular matrix protein thrombospondin-1 is released at sites of tissue injury and modulates several immune functions, but its role in C. albicans pathogenesis has not been investigated. Here, we show that mice lacking thrombospondin-1 have an advantage in surviving disseminated candidiasis and more efficiently clear the initial colonization from kidneys despite exhibiting fewer infiltrating leukocytes. By examining local and systemic cytokine responses to C. albicans and other standard inflammatory stimuli, we identify a crucial function of phagocytes in this enhanced resistance. Subcutaneous air pouch and systemic candidiasis models demonstrated that endogenous thrombospondin-1 enhances the early innate immune response against C. albicans and promotes activation of inflammatory macrophages (inducible nitric oxide synthase⁺, IL-6^high, TNF-α^high, IL-10^low), release of the chemokines MIP-2, JE, MIP-1α, and RANTES, and CXCR2-driven polymorphonuclear leukocytes recruitment. However, thrombospondin-1 inhibited the phagocytic capacity of inflammatory leukocytes in vivo and in vitro, resulting in increased fungal burden in the kidney and increased mortality in wild type mice. Thus, thrombospondin-1 enhances the pathogenesis of disseminated candidiasis by creating an imbalance in the host immune response that ultimately leads to reduced phagocytic function, impaired fungal clearance, and increased mortality. Conversely, inhibitors of thrombospondin-1 may be useful drugs to improve patient recovery from disseminated candidiasis.

Humoral and cell-mediated immunity following vaccination with synthetic Candida cell wall mannan derived heptamannoside-protein conjugate: immunomodulatory properties of heptamannoside-BSA conjugate

Chemically defined glycoprotein conjugate composed of synthetically prepared mannan-derived heptamannoside with terminal β-1,2-linked mannose residue attached to the α-1,3-linked mannose residues and BSA as carrier protein (M7-BSA conjugate) was analysed for the capacity to induce protective humoral immunity and appropriate alteration cellular immunity. To identify protective antigenic structure of Candida cell wall mannan M7-BSA conjugate was used for BALB/c mice immunization. The obtained results were compared with placebo group and with heat-inactivated C. albicans whole cells immunization. The administration route of M7-BSA conjugate secondary booster injection significantly affected the intensity of humoral immune response and the specificity of produced antibodies. All prepared sera were able to elevate candidacidal activity of polymorphonuclear leukocytes (PMN) in cooperation with complement. Moreover, polyclonal sera obtained after secondary subcutaneous (s.c.) booster injection of M7-BSA conjugate were able to induce candidacidal activity of PMN also in complement independent manner. M7-BSA conjugate immunization induced increases of phagocytic activity and respiratory burst of granulocytes, caused a raise of the proportion of CD3(+) T lymphocytes and increased the CD4(+)/CD8(+) T lymphocyte ratio. We observed also an increasing proportion of CD4(+)CD25(+) T cells compared to immunization with heat inactivated whole C. albicans cells, which in turn promoted an increase of the CD8(+)CD25(+) cell proportion. Immunization with M7-BSA conjugate induced Th1, Th2 and Th17 immune responses as indicated by the elevation of relevant cytokines levels. These data provide some insights on the immunomodulatory properties of oligomannosides and contribute to the development of synthetic oligosaccharide vaccines against fungal diseases.

Hosting infection: experimental models to assay Candida virulence

Although normally commensals in humans, Candida albicans, Candida tropicalis, Candida parapsilosis, Candida glabrata, and Candida krusei are capable of causing opportunistic infections in individuals with altered physiological and/or immunological responses. These fungal species are linked with a variety of infections, including oral, vaginal, gastrointestinal, and systemic infections, with C. albicans the major cause of infection. To assess the ability of different Candida species and strains to cause infection and disease requires the use of experimental infection models. This paper discusses the mucosal and systemic models of infection available to assay Candida virulence and gives examples of some of the knowledge that has been gained to date from these models.

An insight into the antifungal pipeline: selected new molecules and beyond

Invasive fungal infections are increasing in incidence and are associated with substantial mortality. Improved diagnostics and the availability of new antifungals have revolutionized the field of medical mycology in the past decades. This Review focuses on recent developments in the antifungal pipeline, concentrating on promising candidates such as new azoles, polyenes and echinocandins, as well as agents such as nikkomycin Z and the sordarins. Developments in vaccines and antibody-based immunotherapy are also discussed. Few therapeutic products are currently in active development, and progression of therapeutic agents with fungus-specific mechanisms of action is of key importance.

Candida parapsilosis: a review of its epidemiology, pathogenesis, clinical aspects, typing and antimicrobial susceptibility

The Candida parapsilosis family has emerged as a major opportunistic and nosocomial pathogen. It causes multifaceted pathology in immuno-compromised and normal hosts, notably low birth weight neonates. Its emergence may relate to an ability to colonize the skin, proliferate in glucose-containing solutions, and adhere to plastic. When clusters appear, determination of genetic relatedness among strains and identification of a common source are important. Its virulence appears associated with a capacity to produce biofilm and production of phospholipase and aspartyl protease. Further investigations of the host-pathogen interactions are needed. This review summarizes basic science, clinical and experimental information about C. parapsilosis.

The anti-Candida vaccine based on the recombinant N-terminal domain of Als1p is broadly active against disseminated candidiasis

We have previously shown that vaccination with a vaccine based on the recombinant N-terminal domain of Als1p (rAls1p-N) protected BALB/c mice against disseminated infection caused by a single strain of Candida albicans (A. S. Ibrahim, B. J. Spellberg, V. Avenissian, Y. Fu, S. G. Filler, and J. E. Edwards, Jr., Infect. Immun. 73:999-1005, 2005, and B. J. Spellberg, A. S. Ibrahim, V. Avenissian, S. G. Filler, C. Myers, Y. Fu, and J. E. Edwards, Jr., Infect. Immun. 73:6191-6193, 2005). Here we show that the rAls1p-N vaccine also improves survival of outbred mice from disseminated candidiasis and that it is active against multiple virulent strains of C. albicans and non-C. albicans spp.

Evaluation of the usefulness of anti-glyceraldehyde-3-phosphate dehydrogenase antibodies as a treatment for invasive candidiasis in a murine model

We have evaluated the effect of antibodies against the Candida albicans glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a potential immunotherapeutic treatment for acute invasive candidiasis in a murine model of infection. Three different approaches were assayed: (i) active immunization of mice using recombinant His-tagged GAPDH, (ii) treatment of fungal yeast cells with anti-GAPDH antibodies prior to infection, and (iii) passive transfer of polyclonal anti-GAPDH antibodies. Results showed that all three approaches, although tending to show a slight beneficial effect in some instances, fail to have a relevant and statistically significant effect on the infection course, determined by survival curves and fungal burden in kidneys. This suggests that the cell wall-associated GAPDH of C. albicans, despite its potential role in virulence, does not appear to be a suitable target protein for the development of immunotherapeutic strategies against candidiasis, although further studies may be required to confirm this observation.

A novel glyco-conjugate vaccine against fungal pathogens

To generate a vaccine to protect against a variety of human pathogenic fungi, we conjugated laminarin (Lam), a well-characterized but poorly immunogenic beta-glucan preparation from the brown alga Laminaria digitata, with the diphtheria toxoid CRM197, a carrier protein used in some glyco-conjugate bacterial vaccines. This Lam-CRM conjugate proved to be immunogenic and protective as immunoprophylactic vaccine against both systemic and mucosal (vaginal) infections by Candida albicans. Protection probably was mediated by anti-beta-glucan antibodies as demonstrated by passive transfer of protection to naive mice by the whole immune serum, the immune vaginal fluid, and the affinity-purified anti-beta-glucan IgG fractions, as well as by administration of a beta-glucan-directed IgG2b mAb. Passive protection was prevented by adsorption of antibodies on Candida cells or beta-glucan particles before transfer. Anti-beta-glucan antibodies bound to C. albicans hyphae and inhibited their growth in vitro in the absence of immune-effector cells. Remarkably, Lam-CRM-vaccinated mice also were protected from a lethal challenge with conidia of Aspergillus fumigatus, and their serum also bound to and markedly inhibited the growth of A. fumigatus hyphae. Thus, this novel conjugate vaccine can efficiently immunize and protect against two major fungal pathogens by mechanisms that may include direct antifungal properties of anti-beta-glucan antibodies.

Current treatment strategies for disseminated candidiasis

The incidence of disseminated candidiasis has increased dramatically over the past several decades. Fortunately, in recent years, a variety of new antifungal agents have become available to treat these infections. On the basis of efficacy, safety, and cost considerations, fluconazole is the agent of choice for the empirical treatment of disseminated candidiasis in nonneutropenic, hemodynamically stable patients, unless a patient is suspected to be infected with an azole-resistant species (i.e., Candida glabrata or Candida krusei). For hemodynamically unstable or neutropenic patients, agents with broader species coverage, such as polyenes, echinocandins, or, possibly, voriconazole, are preferred for empirical treatment of candidemia. Modification of the initial, empirical regimen depends on the response to therapy and the subsequent identification of the species of the offending pathogen. Echinocandins or high-dose polyenes are preferred for the treatment of infections with C. glabrata or C. krusei. Central venous catheters should be removed from all patients who have disseminated candidiasis, if feasible, and antifungal therapy should be administered to all patients who have candidemia or proven candidiasis.

The anti-Candida albicans vaccine composed of the recombinant N terminus of Als1p reduces fungal burden and improves survival in both immunocompetent and immunocompromised mice

We have previously shown that intraperitoneal vaccination with the recombinant N terminus of Als1p (rAls1p-N) modestly improves survival during murine disseminated candidiasis. We now report marked efficacy with subcutaneous rAls1p-N vaccination. Efficacy is retained in neutropenic and corticosteroid-treated mice. The rAls1p-N vaccine is a promising candidate for the prevention of invasive candidiasis.

Vaccination with recombinant N-terminal domain of Als1p improves survival during murine disseminated candidiasis by enhancing cell-mediated, not humoral, immunity

Candida spp. are opportunistic fungal pathogens that are among the most common causes of nosocomial bloodstream infections. The mortality attributable to disseminated candidiasis is 40 to 50% despite antifungal therapy. Clearly, new strategies are needed to prevent this life-threatening infection. Because risk factors for disseminated candidiasis are well defined and frequently of limited duration, vaccination is an appealing prophylactic strategy. We have identified a cell surface protein, Als1p, that mediates adherence of Candida albicans to a variety of human substrates and plastic. Here we report that immunizing BALB/c mice with the recombinant N-terminal domain of Als1p (rAls1p-N) improved survival during a subsequent challenge with a lethal inoculum of C. albicans. The protective 20-mug dose of rAls1p-N significantly increased Candida stimulation of Th1 splenocytes and increased in vivo delayed-type hypersensitivity. In contrast, antibody titers did not correlate with protection. Finally, the vaccine was not protective in T-cell-deficient mice but was protective in B-cell-deficient mice. These data indicate that the mechanism of action of the rAls1p-N vaccine is stimulation of cell-mediated, rather than humoral, immunity against C. albicans. The majority of efforts to date have focused on the development of passive immunization strategies to prevent or treat disseminated candidiasis. In contrast, our results provide proof of principle for vaccination with an adhesin of C. albicans and emphasize the potential for cell-mediated immune modulation as a prophylactic or therapeutic strategy against disseminated candidiasis.

Fungal endocarditis

Recent advances in medicine have caused fungal endocarditis (FE) to be a more common disease entity. Many fungi are potential pathogens in FE, although Candida species and Aspergillus species are the most common. Valvular heart disease is the necessary underlying condition for FE, with intravenous devices and antibiotic use being the predisposing factors for yeast endocarditis, whereas immunosuppression in patients with valvulopathy predisposes for mold endocarditis. Better prognosis of FE depends on fast and accurate diagnosis and subsequent treatment. Echocardiography was the most valuable recent technique in the past two decades that allowed early diagnosis of FE and is probably responsible for the improved prognosis of patients with FE. In the future, development of nonculture-based diagnostic tests may further improve the sensitivity, specificity, and rapidity of microbiologic diagnosis of FE. Novel approaches in treatment, such as new antifungal drugs, also may assist in achieving cure and further improving the prognosis of this disease entity.

Parenchymal organ, and not splenic, immunity correlates with host survival during disseminated candidiasis

We examined the relationship between host survival and renal and splenic immune responses in a murine model of hematogenously disseminated candidiasis. Male BALB/c mice were infected via tail vein injection with wild-type C. albicans or with an isogenic, Deltaefg1/Deltaefg1 hypha-deficient mutant. Host survival, organ fungal burden, intracellular cytokine content of splenic and kidney lymphocytes, and whole-organ cytokine profiles were determined. Wild-type C. albicans induced type 2 splenocyte responses with both nonfatal and fatal inocula. In the kidney, conversely, wild-type inocula causing no or low mortality induced type 1 responses and 100% fatal inocula induced type 2 or interleukin-10 (IL-10)-dominant responses. Hypha-deficient mutant C. albicans caused no or low mortality while inducing type 1 responses in both the spleen and kidney. To our knowledge, this is the first demonstration that host survival during systemic infection correlates with the type of immune response engendered in a nonlymphoid, parenchymal organ and not with the response in the spleen. Furthermore, the results provide in vivo confirmation that hyphal formation by C. albicans induces type 2 or IL-10-dominant host responses in tissues.

The interaction of human dendritic cells with yeast and germ-tube forms ofCandida albicansleads to efficient fungal processing, dendritic cell maturation, and acquisition of a Th1 response-promoting function

T helper cell type 1 (Th1) cell-mediated immunity plays a critical role in protection against the opportunistic pathogen Candida albicans. Virulence of the fungus is closely associated with its ability to form germ-tubes (GT), the early phase of the dimorphic transition from the commensal yeast (Y) to the more invasive hyphal (H) form. In this study, we examined the functional outcome of the interaction of Y or GT forms with human dendritic cells (DCs), professional antigen-presenting cells, which are pivotal for initiation and modulation of T cell responses. DCs phagocytosed and killed Y and GT cells with a comparable efficiency, becoming able to trigger strong proliferative responses by Candida-specific, autologous T cell clones. Both fungal forms induced DC maturation, as indicated by up-regulation of CD83, CD80, CD86, CD40, and major histocompatibility complex classes I and II surface antigens. Chemokine receptors were also modulated in Candida-DCs, which showed increased CCR7/CXCR4 and decreased CCR5 expression. Y- and GT-activated DCs differed in the pattern of cytokine expression. In particular, GT cells, in common with fully differentiated H cells, induced significantly more elevated levels of interleukin (IL)-10 than Y cells. Nevertheless, Y-, GT-, or H-pulsed DCs secreted comparable amounts of IL-12p70. In addition, irrespective of the fungal form triggering DC activation, Candida-DCs acquired the ability to prime naive T lymphocytes with a defined Th1 phenotype. Overall, our findings highlight the induction of substantially similar functional patterns in human DCs encountering the different forms of growth of C. albicans, both seemingly activating the Th1-type immunity which is characteristic of the healthy human subjects, naturally immunized and protected against the fungus.