Promising immunotherapies with Th1-related cytokines against infectious diseases

Immunomodulatory therapy in yeast infections

Invasive yeast infections are a significant cause of morbidity and mortality in patients with defective immune response, such as those with cancer-related immunosuppression, organ transplantation or other immunodeficiencies, and neonates. Hospitalization in the intensive care unit may increase the risk for such infections. Despite the advent of new antifungal agents, the problem is escalating as the number of susceptible hosts increase and virulent, more resistant fungal strains emerge. Over the past few years, advances in immunology and molecular biology have greatly contributed to a better understanding of the pathogenesis of yeast infections. There is evidence that reconstitution of the host immune function is a major contributor to the resolution of yeast infections. Strategies aiming to increase the phagocyte number (e.g., granulocyte transfusions), to stimulate immune response (e.g., administration of hematopoietic growth factors and other proinflammatory cytokines) and to stimulate antigen-specific immunity (e.g., antibody therapy or vaccination) benefit patients at risk of, or suffering from, yeast infections. Further preclinical and clinical studies, as well as improving our understanding of immune system functions and dysfunctions, remain a future challenge.

Improved survival of mice deficient in secretory immunoglobulin M following systemic infection with Cryptococcus neoformans

Cryptococcus neoformans causes severe, and often fatal, disease (cryptococcosis) in immunocompromised patients, particularly in those with HIV/AIDS. Although resistance to cryptococcosis requires intact T-cell immunity, a possible role for antibody/B cells in protection against natural disease has not been definitively established. Previous studies of the antibody response to the C. neoformans capsular polysaccharide glucuronoxylomannan (GXM) have demonstrated that patients who are at increased risk for cryptococcosis have lower serum levels of GXM-reactive IgM than those who are not at risk, leading to the hypothesis that IgM might contribute to resistance to cryptococcosis. To determine the influence of IgM on susceptibility to systemic cryptococcosis in a murine model, we compared the survival of mice deficient in serum IgM (secretory IgM deficient [sIgM(-/-)]) and C57BL/6 x 129Sv (control) mice after intraperitoneal infection with C. neoformans strain 24067 and analyzed the splenic B- and T-cell subsets by flow cytometry and the serum and splenic cytokine/chemokine and serum antibody profiles of each mouse strain. The results showed that sIgM(-/-) mice survived significantly longer than control mice when challenged with 10(5) CFU of C. neoformans 24067. Naïve sIgM(-/-) mice had higher levels of B-1 (CD5(+)) B cells, proinflammatory mediators (interleukin-6 [IL-6], IL-1beta, MIP-1beta, tumor necrosis factor alpha [TNF-alpha], and gamma interferon [IFN-gamma]), and anti-inflammatory mediators (IL-10 and IL-13) and significantly higher titers of GXM-specific IgG2a 3 weeks postinfection. In addition, CD5(+) splenocytes from both mouse strains had fungicidal activity against C. neoformans. Taken together, these results suggest that the inflammatory milieu in sIgM(-/-) mice might confer enhanced resistance to systemic cryptococcosis, stemming in part from the antifungal activity of B-1 B cells.

Lyn kinase controls basophil GATA-3 transcription factor expression and induction of Th2 cell differentiation

T helper 1 (Th1)-Th2 cell balance is key to host defense and its dysregulation has pathophysiological consequences. Basophils are important in Th2 cell differentiation. However, the factors controlling the onset and extent of basophil-mediated Th2 cell differentiation are unknown. Here, we demonstrate that Lyn kinase dampened basophil expression of the transcription factor GATA-3 and the initiation and extent of Th2 cell differentiation. Lyn-deficient mice had a marked basophilia, a constitutive Th2 cell skewing that was exacerbated upon in vivo challenge of basophils, produced antibodies to a normally inert antigen, and failed to appropriately respond to a Th1 cell-inducing pathogen. The Th2 cell skewing was dependent on basophils, immunoglobulin E, and interleukin-4, but was independent of mast cells. Our findings demonstrate that basophil-expressed Lyn kinase exerts regulatory control on Th2 cell differentiation and function.

Lipid A mimetics are potent adjuvants for an intranasal pneumonic plague vaccine

An effective intranasal (i.n.) vaccine against pneumonic plague was developed. The formulation employed two synthetic lipid A mimetics as adjuvant combined with Yersinia pestis-derived V- and F1-protective antigens. The two nontoxic lipid A mimetics, classed as amino-alkyl glucosaminide 4-phosphates (AGPs) are potent ligands for the Toll-like receptor (TLR) 4. Using a murine (BALB/c) pneumonic plague model, we showed a single i.n. application of the vaccine provided 63% protection within 21 days against a Y. pestis CO92 100 LD50 challenge. Protection reached 100% by 150 days. Using a homologous i.n. 1 degrees /2 degrees dose regimen, with the boost administered at varying times, 63% protection was achieved within 7 days and 100% protection was achieved by 21 days after the first immunization. Little or no protection was observed in animals that received antigens alone, and no protection was observed when the vaccine was administered to BALB/c TLR4 mutant mice. Vaccine-induced serum IgG titers to F1 and V-antigen were reflected in high titers for IgG1 and IgG2a, the latter reflecting a bias for a cell-mediated (TH1) immune response. This intranasal vaccine showed 90% protection in Sprague-Dawley rats challenged with 1000 LD50. We conclude that lipid A mimetics are highly effective adjuvants for an i.n. plague vaccine.

IL-24 modulates IFN-gamma expression in patients with tuberculosis

IL-24 is a newly described member of the IL-10 family. We previously demonstrated that PBMC from TB patients exhibited low levels of IL-24 and IFN-gamma compared to subjects with latent tuberculosis infection (LTBI). In order to investigate the role of IL-24 in IFN-gamma expression in TB patients, we stimulated PBMC from individuals with LTBI or TB patients with the Mtb-specific antigen, early secretory antigenic target-6 (ESAT-6) and measured cytokine expression using quantitative real-time PCR (qPCR). Exogenous IL-24 increased IFN-gamma expression in PBMC obtained from TB patients while neutralization of IL-24 reduced IFN-gamma expression in PBMC from subjects with LTBI. Exogenous IL-24 enhanced IFN-gamma expression by increasing expression of IL-12 family cytokines, including IL-12alpha, IL-12beta, IL-23alpha and IL-27, and by reducing FOXP3 expression in PBMC from TB patients. This is the first demonstration that IL-24 may play an important role in IFN-gamma expression following infection with Mtb.

Cloning and characterization of an adenoviral vector for highly efficient and doxycycline-suppressible expression of bioactive human single-chain interleukin 12 in colon cancer

BACKGROUND

Interleukin-12 (IL-12) is well characterized to induce cellular antitumoral immunity by activation of NK-cells and T-lymphocytes. However, systemic administration of recombinant human IL-12 resulted in severe toxicity without perceptible therapeutic benefit. Even though intratumoral expression of IL-12 leads to tumor regression and long-term survival in a variety of animal models, clinical trials have not yet shown a significant therapeutic benefit. One major obstacle in the treatment with IL-12 is to overcome the relatively low expression of the therapeutic gene without compromising the safety of such an approach. Our objective was to generate an adenoviral vector system enabling the regulated expression of very high levels of bioactive, human IL-12.

RESULTS

High gene expression was obtained utilizing the VP16 herpes simplex transactivator. Strong regulation of gene expression was realized by fusion of the VP16 to a tetracycline repressor with binding of the fusion protein to a flanking tetracycline operator and further enhanced by auto-regulated expression of its fusion gene within a bicistronic promoter construct. Infection of human colon cancer cells (HT29) at a multiplicity of infection (m.o.i.) of 10 resulted in the production of up to 8000 ng/106 cells in 48 h, thus exceeding any published vector system so far. Doxycycline concentrations as low as 30 ng/ml resulted in up to 5000-fold suppression, enabling significant reduction of gene expression in a possible clinical setting. Bioactivity of the human single-chain IL-12 was similar to purified human heterodimeric IL-12. Frozen sections of human colon cancer showed high expression of the coxsackie adenovirus receptor with significant production of human single chain IL-12 in colon cancer biopsies after infection with 3*107 p.f.u. Ad.3r-scIL12. Doxycycline mediated suppression of gene expression was up to 9000-fold in the infected colon cancer tissue.

CONCLUSION

VP16 transactivator-mediated and doxycycline-regulated expression of the human interleukin-12 gene enables highly efficient and tightly controlled cytokine expression in human cancer. These data illustrate the potential of the described adenoviral vector system for the safe and superior expression of therapeutic genes in the treatment of colorectal cancer and other malignancies.

Subcutaneously administered interferon-gamma for the treatment of multidrug-resistant pulmonary tuberculosis

OBJECTIVE

We evaluated the clinical and laboratory effects of subcutaneously administered interferon-gamma (IFN-gamma) in the treatment of chronic and advanced multidrug-resistant tuberculosis (MDR-TB).

DESIGN

Eight patients with sputum smear and culture persistently positive MDR-TB were subcutaneously administered 2 million international units of recombinant human IFN-gamma three times a week for 24 weeks (72 doses total) between December 2002 and May 2003. Subjects also received a customized drug regimen containing second- and third-line antituberculosis agents based upon drug susceptibility testing and previous treatment history.

RESULTS

Body weight remained stable or slightly decreased in all subjects during the study period, and none displayed radiographic improvement on serial chest computed tomography scanning. Sputum smears and cultures remained positive for all patients, and there was no increase in the mean time to yield a positive culture (from 16.5+/-6.4 to 11.8+/-4.9 days). There was no enhancement of cell-mediated immune responses in terms of production of IFN-gamma or IL-10, or of composition of lymphocytes among peripheral blood mononuclear cells. In four patients, therapy was discontinued because of adverse reactions.

CONCLUSION

In patients with chronic and advanced MDR-TB, subcutaneous IFN-gamma treatment did not result in improvement in clinical, radiologic, microbiologic, or immunologic parameters.

Immunomodulatory effects of a traditional Chinese medicine with potential antiviral activity: a self-control study

Traditional Chinese medicine (TCM) has been used for prevention and treatment of severe acute respiratory syndrome (SARS) in Hong Kong during the outbreak in spring 2003. We investigated the immunomodulating effects of an innovative TCM regimen derived from two herbal formulas (Sang Ju Yin and Yu Ping Feng San) for treating febrile diseases. Thirty-seven healthy volunteers were given the oral TCM regimen daily for 14 days. Peripheral venous blood samples were taken on days 0, 15 and 29 for hematology, biochemistry and immunology tests, including the measurement of blood lymphocyte subsets and plasma T-helper lymphocyte types 1 and 2 cytokines and receptor. After 3 months, 23 of the volunteers participated in a control study without TCM treatment for the same time course of blood tests. Two volunteers withdrew on day 2, due to headache and dizziness. All others remained well without any side effects. No participants showed significant changes in their blood test results, except that the T-lymphocyte CD4/CD8 ratio increased significantly from 1.31 +/- 0.50 (mean +/- SD) on day 0 to 1.41 +/- 0.63 on day 15 (p < 0.02), and reduced to 1.32 +/- 0.47 on day 29 (p < 0.05). In the control study, there were no changes in the CD4/CD8 ratio. The transient increase in CD4/CD8 ratio was likely due to the TCM intake. We postulate that the administration of the innovative TCM may have beneficial immunomodulatory effects for preventing viral infections including SARS.

Pulmonary Infection with Cryptococcus neoformans in the Face of Underlying Sarcoidosis

We present a case of limited pulmonary cryptococcal infection following exposure to pigeon excreta in a patient with sarcoidosis. The pathogenicity of Cryptococcus neoformans depends on the interplay between the immune status of the host and the virulence of the infecting strain. It can range from asymptomatic lung colonization in the immunocompetent host to rapidly progressive meningitis in immunocompromised patients. Immunological models of respiratory disease emphasize a distinction between infections associated with immune suppression on the one hand and diseases such as sarcoidosis believed to involve an excessive Th1-mediated immune response on the other. This case exemplifies the complex nature of immunological responses in the lung and highlights the importance of considering the possibility of co-existent fungal infection in individuals with sarcoidosis. Novel immunotherapeutic options for cryptococcal infection are discussed.

Stress-induced enhancement of leukocyte trafficking into sites of surgery or immune activation

Effective immunoprotection requires rapid recruitment of leukocytes into sites of surgery, wounding, infection, or vaccination. In contrast to immunosuppressive chronic stressors, short-term acute stressors have immunoenhancing effects. Here, we quantify leukocyte infiltration within a surgical sponge to elucidate the kinetics, magnitude, subpopulation, and chemoattractant specificity of an acute stress-induced increase in leukocyte trafficking to a site of immune activation. Mice acutely stressed before sponge implantation showed 200-300% higher neutrophil, macrophage, natural killer cell, and T cell infiltration than did nonstressed animals. We also quantified the effects of acute stress on lymphotactin- (LTN; a predominantly lymphocyte-specific chemokine), and TNF-alpha- (a proinflammatory cytokine) stimulated leukocyte infiltration. An additional stress-induced increase in infiltration was observed for neutrophils, in response to TNF-alpha, macrophages, in response to TNF-alpha and LTN, and natural killer cells and T cells in response to LTN. These results show that acute stress initially increases trafficking of all major leukocyte subpopulations to a site of immune activation. Tissue damage-, antigen-, or pathogen-driven chemoattractants subsequently determine which subpopulations are recruited more vigorously. Such stress-induced increases in leukocyte trafficking may enhance immunoprotection during surgery, vaccination, or infection, but may also exacerbate immunopathology during inflammatory (cardiovascular disease or gingivitis) or autoimmune (psoriasis, arthritis, or multiple sclerosis) diseases.

Regulatory mechanisms and their therapeutic implications of interleukin-12 production in immune cells

Studies with neutralizing anti-interleukin (IL)-12 antibodies and IL-12-deficient mice have suggested that endogenous IL-12 plays an important role in the normal host defense against infection by a variety of intracellular microorganisms. However, IL-12 also appears to play a central role in the pathogenesis of autoimmune diseases such as multiple sclerosis or rheumatic arthritis. Therefore, it is crucial to understand how IL-12 is produced and its production is regulated at the molecular level. IL-12 production is differentially regulated through multiple pathways, which can be classified as follows: nuclear factor-kappaB (NF-kappaB) and other transcription factors, p38 mitogen-activated protein (MAP) kinase, cyclic adenosine monophosphate (cyclic AMP)-modulating molecules, cell membrane ion channels and pumps, nitric oxide (NO), and receptors. In this review we describe the regulatory mechanisms of IL-12 production in immune cells and also some agents to control IL-12 production for the treatment of immune-related diseases.

Geranylgeraniol regulates negatively caspase-1 autoprocessing: implication in the Th1 response against Mycobacterium tuberculosis

Caspase-1 is a cysteine protease composed by two 20-kDa and two 10-kDa subunits that processes pro-IL-1beta and pro-IL-18 to their mature forms. This enzyme is present in cells as a latent zymogen that becomes active through a tightly regulated proteolytic cascade. Activation is initiated by the oligomerization of an adaptor molecule, or by the formation of a multiprotein complex named inflammasome. Negative regulation of caspase-1 activation is exerted by proteins that compete with the adaptor molecule or with the inflammasome formation. We previously reported that fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, increases caspase-1 activity in PBMC. This effect was strengthened by Mycobacterium tuberculosis, rending an exacerbated IL-1beta, IL-18, and IFN-gamma production. Mevalonate, the product of 3-hydroxy-3-methylglutaryl coenzyme A reductase, is a precursor for both nonsterol isoprenoid and sterol formation. In this study, we studied the involvement of mevalonate derivatives in the regulation of caspase-1 activation. Inhibition of sterol formation by SKF-104976 or haloperidol had no effect on IL-1beta release. However, the isoprenoid geranylgeraniol prevented both caspase-1 activation and the exacerbated IL production induced by fluvastatin. This isoprenoid significantly reduced the release of IL-18 and IFN-gamma by PBMC treated with mycobacteria, even in the absence of fluvastatin. In correlation with the increased caspase-1 activity, fluvastatin stimulated the proforms cleavage, enhancing the formation of active subunit p10. Geranylgeraniol not only prevented this effect, but induced proforms accumulation. Present results suggest that, once the proteolytic cascade is initiated, geranylgeraniol may exert an additional negative regulation on caspase-1 cleavage process.