Tumor Necrosis Factor Inhibition and Invasive Fungal Infections

Transcription

1 SUPPLEMENT ARTICLE Tumor Necrosis Factor Inhibition and Invasive Fungal Infections Scott G. Filler, 1,2 Michael R. Yeaman, 1,2 and Donald C. Sheppard 1,a 1 St. Johns Cardiovascular Research Center, Division of Infectious Diseases, Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, and 2 The David Geffen School of Medicine at University of California, Los Angeles Candida albicans and Aspergillus fumigatus occur ubiquitously in nature; C. albicans is part of the natural flora of most healthy individuals, and A. fumigatus is commonly found in soil, plant debris, and indoor air. Neither fungus poses a threat to healthy individuals, but each can cause fatal infections in immunocompromised patients. The use of tumor necrosis factor (TNF) antagonists for the treatment of rheumatoid arthritis and other autoimmune diseases has been associated with an increased incidence of opportunistic infections, including infections with both of these fungi. Because the use of TNF antagonists is expected to increase in the future, understanding the role that TNF plays and the effect of its antagonism on host defense against infections with these fungi is critical for reducing the associated morbidity and mortality. TNF plays a major role in host defense and regulation of the immune response [1]. It has also been identified as an important factor in the pathogenesis of such autoimmune diseases as rheumatoid arthritis. Three TNF antagonists etanercept, infliximab, and adalimumab have been shown to effectively reduce the progression of disease in patients with rheumatoid arthritis. All 3 agents were well tolerated in clinical trials. However, the US Food and Drug Administration s MedWatch Spontaneous Adverse Event Reporting System for tabulating voluntary reports from around the world indicates that the use of TNF antagonists is associated with an increased incidence of opportunistic infections, such as tuberculosis, histoplasmosis, listeriosis, candidiasis, and aspergillosis. In the United States, there has been a trend toward a higher incidence of Candida infections among patients treated with infliximab (10.15 cases/100,000 persons) than among patients treated with etanercept (5.31 cases/100,000 pera Present affiliation: Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada. Reprints and correspondence: Dr. Scott G. Filler, Div. of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, 1124 W. Carson St., Torrance, CA (sfiller@ucla.edu). Clinical Infectious Diseases 2005; 41:S by the Infectious Diseases Society of America. All rights reserved /2005/4103S3-0006$15.00 sons) ( P p.061). A similar trend was found for Aspergillus infections (8.63 and 6.19 cases/100,000 persons, respectively; P p.243) [2, 3]. One possible explanation for these data is that these 2 drugs are used in different populations. For example, infliximab is approved for use in patients with rheumatoid arthritis and Crohn disease. Infliximab is also used to treat graft-versus-host disease in bone marrow transplant recipients, but it is not approved for this indication. Although etanercept is approved for the treatment of rheumatoid arthritis, it is also approved for use in patients with juvenile rheumatoid arthritis, ankylosing spondylitis, and psoriasis. Thus, it is possible that the higher incidence of reported invasive fungal infections among patients receiving infliximab is related to the characteristics of the patients who receive this drug. Differences in the mechanisms of action of the TNF antagonists may explain the differences in their effectiveness in the treatment of various autoimmune diseases and in inducing susceptibility to infection. Etanercept is a dimeric fusion protein consisting of the extracellular ligand binding portion of the human 75- kda (p75) TNF receptor (TNFR) fused to the Fc portion of human IgG1. Infliximab is a chimeric anti-tnf monoclonal antibody (MAb) composed of the human IgG1 constant region fused to murine variable regions. S208 CID 2005:41 (Suppl 3) Filler et al.

2 Adalimumab is a recombinant, fully human IgG1 MAb. The 2 MAbs, adalimumab and infliximab, have longer half-lives than does the fusion protein etanercept [4 6]. Unlike etanercept, MAbs bind to membrane-anchored TNF-a and can activate complement or cause antibody-dependent cytotoxicity of cells that are expressing TNF-a [7]. In addition, etanercept and infliximab demonstrate different TNF-a binding patterns, with a high on and a high off rate for etanercept, and persistent binding, with a low off rate for infliximab [8]. Finally, intravascular administration of infliximab results in a higher serum concentration of this agent, compared with levels resulting from subcutaneous administration of either etanercept or adalimumab [4 6]. Although Candida species are part of the normal flora of mucosal surfaces in most healthy individuals, the organisms can cause fatal systemic infections in high-risk patients [9]. Hematogenously disseminated candidiasis is increasing in frequency, and Candida species are now the fourth most common pathogen isolated from the blood of hospitalized patients [10]. This infection is associated with a mortality rate of 38% 49%, even with currently available therapy [11, 12]. The classic risk factors for developing hematogenously disseminated candidiasis include neutropenia, intra-abdominal surgery, the presence of an indwelling vascular catheter, the use of broad-spectrum antibiotics, receipt of total parenteral nutrition, and low birth weight (for infants) [9, 13, 14]. Candida species can also cause invasive infections in single organs, as well as skin and mucosal infections. Aspergillus species are molds that are commonly isolated from decaying organic material. Airborne spores are ubiquitous, and the average person inhales an estimated 100 spores/ day. A major risk factor for the development of invasive pulmonary A. fumigatus infections is immunosuppression, including that caused by the use of corticosteroids and the presence of neutropenia [15]. Despite current therapeutic options, the mortality rate associated with invasive aspergillosis is at least 50% [16 18]. The use of TNF antagonists in the treatment of rheumatoid arthritis and other autoimmune diseases is expected to increase over time. In addition, administration of these agents is associated with an increased incidence of invasive C. albicans and A. fumigatus infections. It is, therefore, important to understand the role that TNF plays in mediating the inflammatory response to Candida species and Aspergillus species. Studies providing evidence of the role of TNF in the host response to infections caused by these fungi are discussed below. lining of the gut or entering through an indwelling vascular catheter. The fungus adheres to endothelial cells and then invades these cells by inducing its own endocytosis [19]. Cytotoxic products secreted by the ingested fungus during germination within the host cell cause endothelial cell injury and, eventually, cell death; this results in loss of integrity of the endothelial lining, thereby enabling the fungus to invade deep tissues [20, 21]. TNF-a plays an important role in the host defense against C. albicans infections. TNF-a is released in response to fungal infection and stimulates expression of chemokines and leukocyte adhesion molecules, which leads to recruitment of polymorphonuclear leukocytes, and enhanced phagocytosis and killing of fungi by these cells [22]. In mice, expression of TNFa increases during the first 12 h of infection and is correlated with the accumulation of large numbers of leukocytes at foci of infection [22]. The role that TNF-a plays in host defense against C. albicans has been demonstrated by the study of mice in which both copies of the TNF-a gene have been disrupted (TNF-a / mice). When challenged intravenously with C. albicans, all TNF-a / mice died of infection, whereas all of the wild-type mice survived (figure 1) [23]. The heterozygous mice (TNF +/ mice) had an intermediate phenotype, and 60% died within 20 days after infection. In another study, neutralization of TNF-a with polyclonal antimurine TNF-a antibodies promoted growth of C. albicans in the kidneys and spleen and accelerated death after intravenous infection [24]. The biological responses to TNF are mediated through 2 receptors, TNFRp55 and TNFRp75. The extracellular portion ROLE OF TNF-a IN THE HOST DEFENSE AGAINST INVASIVE FUNGAL INFECTIONS C. albicans. During hematogenously disseminated infection, C. albicans first enters the bloodstream by either traversing the Figure 1. Survival rate after infection with Candida albicans., Wildtype mice (TNF-a +/+ );, heterozygous mice in which 1 copy of the TNFa gene was disrupted (TNF-a +/ );, mice in which both copies of the TNF-a gene were disrupted (TNF-a / ). * P!.05, vs. wild-type mice. Adapted with permission from Marino et al. [23]. TNF-a and Fungal Infections CID 2005:41 (Suppl 3) S209

3 of both receptors is found as soluble TNFR in the circulation. Although the extracellular domains share homology with each other, the intracellular domains have no homology, which indicates that the 2 receptors may use different mechanisms for intracellular signaling. When TNFRp55 / mice are infected with C. albicans, they have impaired ability to clear infection with C. albicans and readily die of the infection [25]. In contrast, TNFRp75 / mice are compromised in their ability to clear the fungus, but the lethality of the infection is not greater than that in wild-type mice, which indicates that TNF-a mediates the host defense against C. albicans infections predominantly through TNFRp55. In similar experiments involving mice deficient for the same receptor, TNFRp55 was found to be crucial in mediating the antibacterial defense against infection with Listeria monocytogenes [26, 27]. TNF-a either stimulates the expression of or mediates the activity of several other molecules involved in the host defense against C. albicans infections. These other molecules include E-selectin, vascular cell adhesion molecule (VCAM) 1, IL-8, and platelet-activating factor (PAF) (figure 2) [28, 29]. E-selectin and VCAM-1 are leukocyte adhesion molecules. Therefore, they are likely to participate in the recruitment of leukocytes to sites of a candidal infection. IL-8 is a potent neutrophil chemoattractant that also primes these leukocytes for enhanced anticandidal activity [30]. Interestingly, maximal endothelial cell expression of E-selectin, VCAM-1, and IL-8 in response to C. albicans in vitro requires TNF-a [28]. These in vitro data provide a possible explanation for the central role that TNF-a plays in the host defense against C. albicans. PAF is a potent phospholipid-derived modulator of immunological and inflammatory processes that is produced by basophils, neutrophils, eosinophils, monocytes/macrophages, platelets, and endothelial cells [29]. Some of the effects of PAF are likely mediated via TNF-a. Among mice infected intravenously with a lethal dose of C. albicans, 70% were rescued with the daily administration of exogenous PAF for 3 days after infection. In that study [29], administration of PAF was associated with an increase in serum levels of TNF-a, and most of the salutary effects of exogenous PAF could be inhibited by blocking production of TNF-a. Administration of the PAF antagonist BN50739 resulted in a significant reduction in TNF-a levels and shortened survival time. These results indicate that the beneficial effects of PAF are mediated, at least in part, by TNF-a. A. fumigatus. In immunocompetent hosts, alveolar macrophages are the primary line of defense against pulmonary infection with A. fumigatus. These cells ingest and kill the inhaled A. fumigatus conidia [31, 32]. Conidia that escape macrophage killing then germinate to form filamentous hyphae, which invade and destroy host tissues. Neutrophils are the primary host defense against these hyphae [31]. TNF-a and lymphotoxin (LT), which also binds to TNFR, are important for host defense against A. fumigatus infections. Increased levels of TNF-a are present in the lungs of mice infected intranasally or intratracheally with A. fumigatus conidia [33 35]. Maximal pulmonary production of TNF-a in response to infection with A. fumigatus is dependent on the presence of IL-12 and IL-18 [34]. TNF-a/LT double knockout mice are more susceptible to pulmonary infection with A. fumigatus [33]. Despite the absence of TNF-a/LT, the recruitment of macrophages and neutrophils to sites of infection was normal in these knockout mice. This finding suggests that TNF-a and LT are more important for enhancing leukocyte killing of A. fumigatus than for recruitment of leukocytes. Indeed, incubation of human neutrophils with recombinant TNF-a augments hyphal killing by these leukocytes [36]. Similarly, incubation of rabbit pulmonary alveolar macrophages with TNF-a results in increased phagocytosis of A. fumigatus conidia by the macrophages [36]. Both immunocompetent and cyclophosphamide-treated mice become more susceptible to pulmonary infection with A. fumigatus when they are administered neutralizing antibodies against TNF-a (figure 3) [34, 35]. This enhanced susceptibility Figure 2. Schematic diagram of the molecules involved in the host defense against Candida albicans. ICAM-1, intercellular adhesion molecule 1; VCAM-1, vascular cell adhesion molecule 1. The question mark (?) indicates that C. albicans stimulates endothelial cells to express ICAM-1 by an unknown mechanism that is independent of TNF-a and IL-1. Adapted with permission from Orozco et al. [28]. S210 CID 2005:41 (Suppl 3) Filler et al.

4 to elucidate the role that TNF-a plays in the mechanism of host defense against these invasive fungal infections. The current TNF antagonists used clinically have different mechanisms of action. Etanercept is a dimeric fusion protein consisting of the extracellular ligand binding portion of TNFRp75 fused to the Fc portion of human IgG1. Evidence suggests that TNFRp55, rather than TNFRp75, is primarily responsible for host defense. Infliximab is a chimeric MAb and binds with a high affinity to membrane-bound TNF, which can result in neutralization of TNF activity and cell lysis. These differences in mechanism of action may explain the variation in their effectiveness in the treatment of various autoimmune diseases and in inducing susceptibility to infection. Acknowledgments We thank Mary Beth Poole and Ruth Pereira for expert editorial assistance. Financial support. National Institutes of Health (Public Health Service grant RO1 AI and contract N01 AI30041). Potential conflicts of interest. All authors have received research grants from Amgen. Figure 3. Effect of TNF-a neutralization on survival of immunocompetent and cyclophosphamide (Cy) treated mice after infection with Aspergillus fumigatus. A, Immunocompetent mice were infected with A. fumigatus ( conidia). B, Cy-treated mice were infected with A. 5 fumigatus ( conidia). * P!.01, vs. mice that received control rabbit serum. Adapted with permission from Mehrad et al. [35]. is manifested by both increased pulmonary fungal burden and, in the case of cyclophosphamide-treated mice, enhanced mortality. In contrast to the findings noted for the TNF-a/LT knockout mice, the mice treated with the anti TNF-a antibodies showed diminished neutrophil recruitment into the infected lungs. This lack of neutrophil influx was likely the result of the reduction in pulmonary expression of the chemokines macrophage inflammatory proteins 1a and 2 [35]. SUMMARY AND CONCLUSIONS The number of individuals receiving immunomodulators, such as TNF antagonists, has increased sharply in recent years and is expected to increase substantially in the near future. The incidence of invasive fungal infections, such as candidiasis and aspergillosis, is increased among patients who are receiving TNF antagonists. Experimental animal studies indicate that the innate immune system plays a major role in host defense against these 2 fungal pathogens. Although TNF-a is not the only cytokine involved, it plays a major role in the recruitment of neutrophils to the infection site during hematogenously disseminated candidiasis. TNF-a also potentiates the antifungal capacity of both neutrophils and macrophages. Well-established murine models of candidiasis and aspergillosis have been used References 1. Kollias G, Douni E, Kassiotis G, Kontoyiannis D. On the role of tumor necrosis factor and receptors in models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease. Immunol Rev 1999; 169: Wallis RS, Broder MS, Wong JY, Hanson ME, Beenhouwer DO. Granulomatous infectious diseases associated with tumor necrosis factor antagonists. Clin Infect Dis 2004; 38: Wallis RS, Broder M, Wong J, Beenhouwer D. Granulomatous infections due to tumor necrosis factor blockade: correction. Clin Infect Dis 2004; 39: Humira [package insert]. North Chicago, IL: Abbott Laboratories, Enbrel [package insert]. Thousand Oaks, CA: Immunex, Remicade [package insert]. Malvern, PA: Centecor, Scallon BJ, Moore MA, Trinh H, Knight DM, Ghrayeb J. Chimeric anti-tnf-a monoclonal antibody ca2 binds recombinant transmembrane TNF-a and activates immune effector functions. Cytokine 1995; 7: Scallon B, Cai A, Solowski N, et al. Binding and functional comparisons of two types of tumor necrosis factor antagonists. J Pharmacol Exp Ther 2002; 301: Wenzel RP. Nosocomial candidemia: risk factors and attributable mortality. Clin Infect Dis 1995; 20: Edmond MB, Wallace SE, McClish DK, Pfaller MA, Jones RN, Wenzel RP. Nosocomial bloodstream infections in United States hospitals: a three-year analysis. Clin Infect Dis 1999; 29: Gudlaugsson O, Gillespie S, Lee K, et al. Attributable mortality of nosocomial candidemia, revisited. Clin Infect Dis 2003; 37: Wey SB, Mori M, Pfaller MA, Woolson RF, Wenzel RP. Hospital-acquired candidemia: the attributable mortality and excess length of stay. Arch Intern Med 1988; 148: Rangel-Frausto MS, Wiblin T, Blumberg HM, et al. National epidemiology of mycoses survey (NEMIS): variations in rates of bloodstream infections due to Candida species in seven surgical intensive care units and six neonatal intensive care units. Clin Infect Dis 1999; 29: Klein RS, Harris CA, Small CB, Moll B, Lesser M, Friedland GH. Oral candidiasis in high-risk patients as the initial manifestation of the acquired immunodeficiency syndrome. N Engl J Med 1984; 311: TNF-a and Fungal Infections CID 2005:41 (Suppl 3) S211

5 15. Ho PL, Yuen KY. Aspergillosis in bone marrow transplant recipients. Crit Rev Oncol Hematol 2000; 34: Denning DW. Therapeutic outcome in invasive aspergillosis. Clin Infect Dis 1996; 23: Denning DW, Marinus A, Cohen J, et al. An EORTC multicentre prospective survey of invasive aspergillosis in haematological patients: diagnosis and therapeutic outcome. EORTC Invasive Fungal Infections Cooperative Group. J Infect 1998; 37: Herbrecht R, Denning DW, Patterson TF, et al. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N Engl J Med 2002; 347: Rotrosen D, Edwards JE Jr, Gibson TR, Moore JC, Cohen AH, Green I. Adherence of Candida to cultured vascular endothelial cells: mechanisms of attachment and endothelial cell penetration. J Infect Dis 1985; 152: Filler SG, Ibe BO, Luckett PM, Raj JU, Edwards JE Jr. Candida albicans stimulates endothelial cell eicosanoid production. J Infect Dis 1991; 164: Filler SG, Swerdloff JN, Hobbs C, Luckett PM. Penetration and damage of endothelial cells by Candida albicans. Infect Immun 1995; 63: Cannom RR, French SW, Johnston D, Edwards JE Jr, Filler SG. Candida albicans stimulates local expression of leukocyte adhesion molecules and cytokines in vivo. J Infect Dis 2002; 186: Marino MW, Dunn A, Grail D, et al. Characterization of tumor necrosis factor-deficient mice. Proc Natl Acad Sci USA 1997; 94: Louie A, Baltch AL, Smith RP, et al. Tumor necrosis factor alpha has a protective role in a murine model of systemic candidiasis. Infect Immun 1994; 62: Steinshamn S, Bemelmans MH, van Tits LJ, Bergh K, Buurman WA, Waage A. TNF receptors in murine Candida albicans infection: evidence for an important role of TNF receptor p55 in antifungal defense. J Immunol 1996; 157: Rothe J, Lesslauer W, Lotscher H, et al. Mice lacking the tumour necrosis factor receptor 1 are resistant to TNF-mediated toxicity but highly susceptible to infection by Listeria monocytogenes. Nature 1993; 364: Pfeffer K, Matsuyama T, Kundig TM, et al. Mice deficient for the 55 kd tumor necrosis factor receptor are resistant to endotoxic shock, yet succumb to L. monocytogenes infection. Cell 1993; 73: Orozco AS, Zhou X, Filler SG. Mechanisms of the proinflammatory response of endothelial cells to Candida albicans infection. Infect Immun 2000; 68: Im SY, Choi JH, Ko HM, et al. A protective role of platelet-activating factor in murine candidiasis. Infect Immun 1997; 65: Djeu JY, Matsushima K, Oppenheim JJ, Shiotsuki K, Blanchard DK. Functional activation of human neutrophils by recombinant monocyte derived neutrophil chemotactic factor/il-8. J Immunol 1990; 144: Schaffner A, Douglas H, Braude A. Selective protection against conidia by mononuclear and against mycelia by polymorphonuclearphagocytes in resistance to Aspergillus: observations on these two lines of defense in vivo and in vitro with human and mouse phagocytes. J Clin Invest 1982; 69: Waldorf AR, Levitz SM, Diamond RD. In vivo bronchoalveolar macrophage defense against Rhizopus oryzae and Aspergillus fumigatus. J Infect Dis 1984; 150: Cenci E, Mencacci A, Fe d Ostiani C, et al. Cytokine- and T helper dependent lung mucosal immunity in mice with invasive pulmonary aspergillosis. J Infect Dis 1998; 178: Brieland JK, Jackson C, Menzel F, et al. Cytokine networking in lungs of immunocompetent mice in response to inhaled Aspergillus fumigatus. Infect Immun 2001; 69: Mehrad B, Strieter RM, Standiford TJ. Role of TNF-a in pulmonary host defense in murine invasive aspergillosis. J Immunol 1999; 162: Roilides E, Dimitriadou-Georgiadou A, Sein T, Kadiltsoglou I, Walsh TJ. Tumor necrosis factor alpha enhances antifungal activities of polymorphonuclear and mononuclear phagocytes against Aspergillus fumigatus. Infect Immun 1998; 66: S212 CID 2005:41 (Suppl 3) Filler et al.