The role of cytokines in mycobacterial infection

Disseminated cryptococcosis and anti-granulocyte-macrophage colony-stimulating factor autoantibodies: An underappreciated association

The development of disseminated cryptococcosis has historically occurred in patients living with advanced human immunodeficiency virus or other immunosuppressive conditions affecting T-cell function. Recently, patients with anti-cytokine neutralising autoantibodies have been recognised to be at risk for disseminated infections by opportunistic intracellular pathogens, including Cryptococcus species. Herein, we present a previously healthy 26-year-old man who was evaluated with disseminated cryptococcosis involving the bone, lung, mediastinum and brain. The patient's serum cryptococcal antigen titres were >1:1,100,000, and evaluation for an underlying immunodeficiency revealed high titres for anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies. We also review the literature of all published cases of disseminated cryptococcosis associated with the presence of anti-GM-CSF autoantibodies. Clinicians should have a heightened awareness of anti-cytokine autoantibodies in patients without a known immunodeficiency and development disseminated infections by opportunistic intracellular pathogens.

A New Method for Recognizing Cytokines Based on Feature Combination and a Support Vector Machine Classifier

Research on cytokine recognition is of great significance in the medical field due to the fact cytokines benefit the diagnosis and treatment of diseases, but the current methods for cytokine recognition have many shortcomings, such as low sensitivity and low F-score. Therefore, this paper proposes a new method on the basis of feature combination. The features are extracted from compositions of amino acids, physicochemical properties, secondary structures, and evolutionary information. The classifier used in this paper is SVM. Experiments show that our method is better than other methods in terms of accuracy, sensitivity, specificity, F-score and Matthew's correlation coefficient.

Human Granulocyte Macrophage Colony-Stimulating Factor Enhances Antibiotic Susceptibility of Pseudomonas aeruginosa Persister Cells

Bacterial persister cells are highly tolerant to antibiotics and cause chronic infections. However, little is known about the interaction between host immune systems with this subpopulation of metabolically inactive cells, and direct effects of host immune factors (in the absence of immune cells) on persister cells have not been studied. Here we report that human granulocyte macrophage-colony stimulating factor (GM-CSF) can sensitize the persister cells of Pseudomonas aeruginosa PAO1 and PDO300 to multiple antibiotics including ciprofloxacin, tobramycin, tetracycline, and gentamicin. GM-CSF also sensitized the biofilm cells of P. aeruginosa PAO1 and PDO300 to tobramycin in the presence of biofilm matrix degrading enzymes. The DNA microarray and qPCR results indicated that GM-CSF induced the genes for flagellar motility and pyocin production in the persister cells, but not the normal cells of P. aeruginosa PAO1. Consistently, the supernatants from GM-CSF treated P. aeruginosa PAO1 persister cell suspensions were found cidal to the pyocin sensitive strain P. aeruginosa PAK. Collectively, these findings suggest that host immune factors and bacterial persisters may directly interact, leading to enhanced susceptibility of persister cells to antibiotics.

Dynamics of immune effector mechanisms during infection with Mycobacterium avium in C57BL/6 mice

Opportunistic infections with non-tuberculous mycobacteria such as Mycobacterium avium are receiving renewed attention because of increased incidence and difficulties in treatment. As for other mycobacterial infections, a still poorly understood collaboration of different immune effector mechanisms is required to confer protective immunity. Here we have characterized the interplay of innate and adaptive immune effector mechanisms contributing to containment in a mouse infection model using virulent M. avium strain 104 in C57BL/6 mice. M. avium caused chronic infection in mice, as shown by sustained organ bacterial load. In the liver, bacteria were contained in granuloma-like structures that could be defined morphologically by expression of the antibacterial innate effector protein Lipocalin 2 in the adjoining hepatocytes and infiltrating neutrophils, possibly contributing to containment. Circulatory anti-mycobacterial antibodies steadily increased throughout infection and were primarily of the IgM isotype. Highest levels of interferon-γ were found in infected liver, spleen and serum of mice approximately 2 weeks post infection and coincided with a halt in organ bacterial growth. In contrast, expression of tumour necrosis factor was surprisingly low in spleen compared with liver. We did not detect interleukin-17 in infected organs or M. avium-specific T helper 17 cells, suggesting a minor role for T helper 17 cells in this model. A transient and relative decrease in regulatory T cell numbers was seen in spleens. This detailed characterization of M. avium infection in C57BL/6 mice may provide a basis for future studies aimed at gaining better insight into mechanisms leading to containment of infections with non-tuberculous mycobacteria.

Comparison of whole-blood interferon-γ assay and flow cytometry for the detection of tuberculosis infection

OBJECTIVE

Limited data exist about the performance of the intracellular cytokine flow cytometry (ICCFC) with respect to that of the commercial interferon-γ release assay for the detection of tuberculosis (TB) infection. Here, we compared the diagnostic accuracy of an ICCFC with that of the QuantiFERON-TB Gold In-Tube (QFT-IT) test for the detection of TB in a clinical setting.

METHODS

Eighty-nine patients suspected of having TB were prospectively included. Both the QFT-IT test and ICCFC were performed for all subjects (TB [n = 65] and non-TB [n = 24]). Ten healthy controls who tested negative by QFT-IT were also assessed by ICCFC.

RESULTS

The sensitivity of the ICCFC was significantly superior to that of the QFT-IT test (91% vs. 78%, p = 0.021). The clinical characteristics of patients in whom the ICCFC exhibited superior sensitivity compared to the QFT-IT test included advanced age, lymphocytopenia, hypoalbuminemia, increased C-reactive protein level, a positive acid-fast bacilli smear of respiratory specimens, and radiographically more extensive disease.

CONCLUSIONS

ICCFC might be a preferable technique for the detection of TB infection, particularly in patients with conditions associated with impaired performance of the QFT-IT test.

Sphingosine kinase-1 (SphK-1) regulates Mycobacterium smegmatis infection in macrophages

Sphingosine kinase-1 is known to mediate Mycobacterium smegmatis induced inflammatory responses in macrophages, but its role in controlling infection has not been reported to date. We aimed to unravel the significance of SphK-1 in controlling M. smegmatis infection in RAW 264.7 macrophages. Our results demonstrated for the first time that selective inhibition of SphK-1 by either D, L threo dihydrosphingosine (DHS; a competitive inhibitor of Sphk-1) or Sphk-1 siRNA rendered RAW macrophages sensitive to M. smegmatis infection. This was due to the reduction in the expression of iNOs, p38, pp-38, late phagosomal marker, LAMP-2 and stabilization of the RelA (pp-65) subunit of NF-kappaB. This led to a reduction in the generation of NO and secretion of TNF-alpha in infected macrophages. Congruently, overexpression of SphK-1 conferred resistance in macrophages to infection which was due to enhancement in the generation of NO and expression of iNOs, pp38 and LAMP-2. In addition, our results also unraveled a novel regulation of p38MAPK by SphK-1 during M. smegmatis infection and generation of NO in macrophages. Enhanced NO generation and expression of iNOs in SphK-1++ infected macrophages demonstrated their M-1(bright) phenotype of these macrophages. These findings thus suggested a novel antimycobacterial role of SphK-1 in macrophages.

Immunological defense mechanisms in tuberculosis and MAC-infection

Protective immunity to mycobacterial infections develops in immunocompetent hosts after activation of alpha beta- and gamma delta-T cells in association with the generation of a protection-specific cytokine profile that stimulates the bactericidal potential of the macrophages. The maintenance of a delicate balance between Th1 and Th2 response is decisive for infection control and prevention of exacerbation of disease. Mycobacterial infection in the immunocompromised host is mainly due to the diminished cellular immune function. In addition, nontuberculous mycobacteria isolated from AIDS patients have special virulence factors that promote development of disease by further compromising the function of an already damaged cytokine network.

Cerebrospinal fluid cytokines in patients with tuberculous meningitis

The level of tumor necrosis factor (TNF)-alpha, soluble TNF receptors p75 (sTNFR-75) and sTNFR-55, interferon (IFN)-gamma, and interleukin (IL)-10 and IL-12 were measured in 59 cerebrospinal fluid (CSF) samples from 15 patients with tuberculous meningitis (TBM). TBM was associated with elevated concentrations of TNF-alpha, sTNFR-75, sTNFR-55, IFN-gamma, and IL-10, while CSF IL-12 was undetectable in all TBM patients. A significant correlation between cytokines and CSF adenosine deaminase activity was also found. The levels of TNF-alpha did not decrease over time, being still detectable in the CSF 16 months after starting antibiotic therapy, whereas IFN-gamma along with anti-inflammatory mediators sTNFR-75, sTNFR-55, and IL-10 remained elevated in the CSF for 4-8 months. The chronic release of cytokines in the CSF compartment was related neither to the TBM stage nor to the clinical outcome of the disease, thus suggesting the presence of a continuous activity of the inflammatory process at the site of infection.

Reproductive effects of chronic administration of murine interferon-gamma

Daily subcutaneous doses of 0.02, 0.2, or 2 mg/kg/d of recombinant murine interferon-gamma (rmuIFN-gamma) were given to mice on postnatal days 8 through 60 to determine effects on maturation, behavioral/ functional development, and reproductive capacity. Male mice receiving 2 mg/kg/d rmuIFN-gamma had delayed sexual maturation, reduced epididymal and testes weights, reduced sperm count and concentration, and sperm abnormalities (crimped flagellum). Mating performance and fertility were also reduced in the absence of altered histopathology of the testes. Males given 0.2 and 2 mg/kg/d had swelling and ulcerative dermatitis around the urogenital area, which were observed after sexual contact and attributed to a bacterial infection. Motor activity (time spent in movement) was decreased in all mice receiving 2 mg/kg/d. No microscopic changes observed in any organs were attributed to rmuIFN-gamma administration.

Cytokines and bacterial infections

During the recent 10-15 years a growing amount of knowledge has been accumulated on the role of cytokines in the pathogenesis and resistance to infections caused by nonviral agents, including a wide range of bacteria. Cytokines can be major mediators of the pathogenic effect in some diseases, and represent important defense mechanisms in others. Detailed knowledge on the role of the growing number of recognised cytokines is important, because it may represent means to combat and to prevent diseases caused by such infections.