Article

The PD-1/PD-L costimulatory pathway critically affects host resistance to the pathogenic fungus Histoplasma capsulatum.

Departments of Microbiology and Immunology, Albert Einstein College of Medicine, Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 03/2008; 105(7):2658-63. DOI: 10.1073/pnas.0711918105
Source: PubMed

ABSTRACT The PD-1 costimulatory receptor inhibits T cell receptor signaling upon interacting with its ligands PD-L1 and PD-L2. The PD-1/PD-L pathway is critical in maintaining self-tolerance. In this study, we examined the role of PD-1 in a mouse model of acute infection with Histoplasma capsulatum, a major human pathogenic fungus. In a lethal model of histoplasmosis, all PD-1-deficient mice survived infection, whereas the wild-type mice died with disseminated disease. PD-L expression on macrophages and splenocytes was up-regulated during infection, and macrophages from infected mice inhibited in vitro T cell activation. Of interest, antibody blocking of PD-1 significantly increased survival of lethally infected wild-type mice. Thus, our studies extend the role of the PD-1/PD-L pathway in regulating antimicrobial immunity to fungal pathogens. The results show that the PD-1/PD-L pathway has a key role in the regulation of antifungal immunity, and suggest that manipulation of this pathway represents a strategy of immunotherapy for histoplasmosis.

0 Bookmarks
 · 
73 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A major pathophysiologic mechanism in sepsis is impaired host immunity which results in failure to eradicate invading pathogens and increased susceptibility to secondary infections. Although many immunosuppressive mechanisms exist, increased expression of the inhibitory receptor programmed cell death 1 (PD-1) and its ligand (PD-L1) are thought to play key roles. The newly recognized phenomenon of T cell exhaustion is mediated in part by PD-1 effects on T cells. This study tested the ability of anti-PD-1 and anti-PD-L1 antibodies to prevent apoptosis and improve lymphocyte function in septic patients. Blood was obtained from 43 septic and 15 non-septic critically-ill patients. Effects of anti-PD-1, anti-PD-L1, or isotype-control antibody on lymphocyte apoptosis and interferon gamma (IFN-gamma) and interleukin-2 (IL-2) production were quantitated by flow cytometry. Lymphocytes from septic patients produced decreased IFN-gamma and IL-2 and had increased CD8 T cell expression of PD-1 and decreased PD-L1 expression compared to non-septic patients (P < 0.05). Monocytes from septic patients had increased PD-L1 and decreased HLA-DR expression compared to non-septic patients (P < 0.01). CD8 T cell expression of PD-1 increased over time in ICU as PD-L1, IFN-gamma, and IL2 decreased. In addition, donors with the highest CD8 PD-1 expression together with the lowest CD8 PD-L1 expression also had lower levels of HLA-DR expression in monocytes, and an increased rate of secondary infections, suggestive of a more immune exhausted phenotype. Treatment of cells from septic patients with anti-PD-1 or anti-PD-L1 antibody decreased apoptosis and increased IFN-gamma and IL-2 production in septic patients; (P < 0.01). The percentage of CD4 T cells that were PD-1 positive correlated with the degree of cellular apoptosis (P < 0.01). In vitro blockade of the PD-1:PD-L1 pathway decreases apoptosis and improves immune cell function in septic patients. The current results together with multiple positive studies of anti-PD-1 and anti-PD-L1 in animal models of bacterial and fungal infections and the relative safety profile of anti-PD-1/anti-PD-L1 in human oncology trials to date strongly support the initiation of clinical trials testing these antibodies in sepsis, a disorder with a high mortality.
    Critical care (London, England) 01/2014; 18(1):R3. · 4.72 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sepsis remains the leading cause of death in most intensive care units. Advances in understanding the immune response to sepsis provide the opportunity to develop more effective therapies. The immune response in sepsis can be characterized by a cytokine-mediated hyper-inflammatory phase, which most patients survive, and a subsequent immune-suppressive phase. Patients fail to eradicate invading pathogens and are susceptible to opportunistic organisms in the hypo-inflammatory phase. Many mechanisms are responsible for sepsis-induced immuno-suppression, including apoptotic depletion of immune cells, increased T regulatory and myeloid-derived suppressor cells, and cellular exhaustion. Currently in clinical trial for sepsis are granulocyte macrophage colony stimulating factor and interferon gamma, immune-therapeutic agents that boost patient immunity. Immuno-adjuvants with promise in clinically-relevant animal models of sepsis include anti-programmed cell death-1 and interleukin-7. The future of immune-therapy in sepsis will necessitate identification of the immunologic phase using clinical and laboratory parameters as well as biomarkers of innate and adaptive immunity.
    Virulence 09/2013; 5(1). · 2.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Programmed cell death 1 (PD-1) is an inhibitory immune receptor that regulates T cell function, yet the molecular events that control its expression are largely unknown. We show here that B lymphocyte-induced maturation protein 1 (Blimp-1)-deficient CD8 T cells fail to repress PD-1 during the early stages of CD8 T cell differentiation after acute infection with lymphocytic choriomeningitis virus (LCMV) strain Armstrong. Blimp-1 represses PD-1 through a feed-forward repressive circuit by regulating PD-1 directly and by repressing NFATc1 expression, an activator of PD-1 expression. Blimp-1 binding induces a repressive chromatin structure at the PD-1 locus, leading to the eviction of NFATc1 from its site. These data place Blimp-1 at an important phase of the CD8 T cell effector response and provide a molecular mechanism for its repression of PD-1.
    Journal of Experimental Medicine 03/2014; · 13.21 Impact Factor

Full-text (2 Sources)

Download
23 Downloads
Available from
Jun 5, 2014