Biological properties of interleukin-12 and its therapeutic use in persistent hepatitis B virus and hepatitis C virus infection

Interleukin-12 and host defense against murine Pneumocystis pneumonia

Little is known about the role of the cytokine interleukin-12 (IL-12) in Pneumocystis pneumonia or its potential use as immunotherapy. We asked whether release of IL-12 is part of the normal host response to this infection and whether local treatment with IL-12 or gene transfer of IL-12 could accelerate clearance of infection. IL-12 was assayed by enzyme-linked immunosorbent assay in normal mice and in mice deficient in IL-12 after inoculation of Pneumocystis carinii. P. carinii-infected mice were treated with local instillation of IL-12 and gene transfer of the IL-12 gene. Inoculation of P. carinii into normal mice evoked a brisk release of IL-12 into lung tissue, and IL-12 P35-deficient mice showed delayed clearance of infection measured by PCR for P. carinii rRNA. In control mice, intranasal recombinant IL-12 accelerated clearance of infection, and this was associated with increased recruitment of inflammatory cells into lavage fluid and increased release of tumor necrosis factor alpha, IL-12, and gamma interferon. Similar results were observed in infected mice depleted of CD4+ lymphocytes by using in vivo transfer of the IL-12 gene in a replication-deficient adenoviral vector. IL-12 is part of the normal host response to infection with P. carinii. IL-12 therapy can enhance host resistance to infection in both normal mice and mice depleted of CD4+ T lymphocytes. A treatment effect of IL-12 is mediated through enhanced inflammatory cell recruitment into lung tissue and increased tissue concentrations of proinflammatory cytokines.

Interleukin 6 and 12, Alanine Aminotransferase Activity, and HCV Viral Load in Children with Chronic Hepatitis C Treated with Interferon and Ribavirin

The response to viral infections is mediated through the co-operation of cellular and humoral mechanisms. The aim of this study was to seek the correlation between IL-6 and IL-12 level, HCV viral load, ALT activity during the 48-week treatment with interferon-alpha-2b (IFN-alpha-2b) combined with ribavirin in children with diagnosed CHC and to search their influence on positive response to treatment. The group of 27 children with CHC was enrolled into this study. The children were treated with interferon-alpha and ribavirin in the course of 48-week therapy. The results show that both ALT activity and the viral load at the time of implementation of treatment with IFN-alpha and ribavirin is an important prognostic tool when treating children. It has been shown that the levels of IL-6 do not bear any significant prognostic importance to the implemented therapy, yet the increase of IL-12 levels in the 24th week of the treatment may be of prognostic value and may point out the possible elimination of HCV-RNA.

Chronic immune activation and inflammation in the pathogenesis of AIDS and cancer

Infection with the human immunodeficiency virus (HIV) invariably leads to the development of acquired immunodeficiency syndrome (AIDS) in most infected humans, yet does so rarely, if at all, in HIV-infected chimpanzees. The differences between the two species are not due to differences in cellular receptors or an inability of the chimpanzee to be infected, but rather to the lack of pan-immune activation in the infected primate. This results in reduced apoptotic death in CD4+ T-helper lymphocytes and a lower viral load. In humans the degree of chronic immune activation correlates with virus load and clinical outcome with high immune activation leading to high viral loads and the more rapid progression to AIDS and death. The type of immune perturbation seen in HIV-associated AIDS is similar to that of chronic graft-versus-host disease (GVHD) where reduced cell-mediated immune (CMI) responses occur early in the course of the disease and where humoral responses (HI) predominate. A reduced CMI response occurs in a number of chronic infectious diseases, including tuberculosis and leishmaniasis. More recently, it has become increasingly apparent that the CMI response is suppressed in virtually all malignant diseases, including melanoma and colorectal and prostate cancer. This raises the possibility that, as the malignant process develops, the cancer cells evolve to subvert the CMI response. Moreover, the reduced CMI response seen in colorectal cancer (CRC) patients is completely reversed following curative surgery strongly supporting the hypothesis that CRC can suppress the systemic immune response. Wound healing, ovulation, embryo implantation, and fetal growth are all associated with suppressed CMI and neovascularization (the formation of new blood vessels) or angiogenesis (the formation of new blood vessels from an existing vasculature). If unresolved, wound healing results in chronic inflammation, which can give rise to the phenomenon of "scar cancers." Indeed all the chronic inflammatory conditions known to be associated with the subsequent development of malignant disease, including chronic obstructive airway disease (COPD), ulcerative colitis (UC), and asbestosis, give rise to similar proangiogenic, suppressed CMI, and HI-predominant environments. In keeping with this CMI-associated cytokines such as interleukin (IL)-2 and interferon (IFN)-gamma tend to be antiangiogenic, whereas HI cytokines such as IL-6 tend to be proangiogenic. Furthermore, chronic immune activation leads to the synthesis and release of factors such as macrophage inflammatory protein (MIP)-1 that inhibit apoptosis through suppression of p53 activity. The "Golden Triangle" of suppressed CMI, angiogenesis, and reduced apoptosis would provide the ideal environment for the serial mutations to occur that are required for the development of malignant disease. If the observed association is relevant to carcinogenesis, then treatments aimed at reducing the components of these inflammatory conditions may be useful both in the setting of chemoprevention and the therapeutic management of established disease.

Treatment of chronic viral hepatitis

Significant advances have been made in the treatment of both hepatitis B and C. Cure for the majority is becoming reality. Combination regimens are now established therapy in hepatitis C and the near future will see the adoption of a similar approach to hepatitis B. Interferon alpha therapy remains important, with the development of more efficacious pegylated forms. In this article we review current therapy and discuss future strategies of the therapy for chronic viral hepatitis.

Compartmental differences in NK cell responsiveness to IL-12 during lymphocytic choriomeningitis virus infection

Some, but not all, viral infections induce endogenous IL-12 to drive NK cell IFN-gamma production and downstream antiviral defenses during innate immune responses. Even though lymphocytic choriomeningitis virus (LCMV) can be sensitive to IFN-gamma-mediated antiviral effects, infections with this agent do not elicit IL-12 or early IFN-gamma in immunocompetent hosts. Studies presented here demonstrate that LCMV infections of mice not only fail to induce IL-12, but also modify responsiveness to exogenous IL-12 for IFN-gamma production. IFN-gamma responses induced by IL-12 administration were greatly diminished in splenic populations, but significantly increased in serum and hepatic leukocytes, during the early course of LCMV infections. The IFN-gamma production was NK cell dependent, and the compartmental dichotomy between spleen and liver was also demonstrated in response to in vitro IL-12 stimulation. Although infections did increase proportions and numbers of liver NK cells, changes in responsiveness for IFN-gamma expression could not be explained by cell redistribution. Corroborating changes in proportions of NK cells induced to express intracellular IFN-gamma protein within the compartments were observed. The reduction in ability of splenic populations to produce IL-12-induced IFN-gamma after infection by LCMV was associated with decreased efficacy of administered IL-12 for promoting IFN-gamma-dependent antiviral effects in the spleen. Concomitantly, the maintenance of hepatic population IFN-gamma production was associated with preserved efficacy of administered IL-12 to elicit IFN-gamma-dependent antiviral effects in the liver. Taken together, these results demonstrate modifications of compartmental responses to IL-12 by viral infections and the consequences of these changes for efficacy of cytokine therapy.

The relationship between angiogenesis and the immune response in carcinogenesis and the progression of malignant disease

Recent studies have demonstrated that angiogenesis and suppressed cell-mediated immunity (CMI) play a central role in the pathogenesis of malignant disease facilitating tumour growth, invasion and metastasis. In the majority of tumours, the malignant process is preceded by a pathological condition or exposure to an irritant which itself is associated with the induction of angiogenesis and/or suppressed CMI. These include: cigarette smoking, chronic bronchitis and lung cancer; chronic oesophagitis and oesophageal cancer; chronic viral infections such as human papilloma virus and ano-genital cancers, chronic hepatitis B and C and hepatocellular carcinoma, and Epstein-Barr virus (EBV) and lymphomas; chronic inflammatory conditions such as Crohn's disease and ulcerative colitis and colorectal cancer; asbestos exposure and mesothelioma and excessive sunlight exposure/sunburn and malignant melanoma. Chronic exposure to growth factors (insulin-like growth factor-I in acromegaly), mutations in tumour suppressor genes (TP53 in Li Fraumeni syndrome) and long-term exposure to immunosuppressive agents (cyclosporin A) may also give rise to similar environments and are associated with the development of a range of solid tumours. The increased blood supply would facilitate the development and proliferation of an abnormal clone or clones of cells arising as the result of: (a) an inherited genetic abnormality; and/or (b) acquired somatic mutations, the latter due to local production and/or enhanced delivery of carcinogens and mutagenic growth factors. With progressive detrimental mutations and growth-induced tumour hypoxia, the transformed cell, to a lesser or greater extent, may amplify the angiogenic process and CMI suppression, thereby facilitating further tumour growth and metastasis. There is accumulating evidence that long-term treatment with cyclo-oxygenase inhibitors (aspirin and indomethacin), cytokines such as interferon-alpha, anti-oestrogens (tamoxifen and raloxifene) and captopril significantly reduces the incidence of solid tumours such as breast and colorectal cancer. These agents are anti-angiogenic and, in the case of aspirin, indomethacin and interferon-alpha have proven immunomodulatory effects. Collectively these observations indicate that angiogenesis and suppressed CMI play a central role in the development and progression of malignant disease.

Predictors of sustained response to alpha interferon therapy in chronic hepatitis C

OBJECTIVES

To utilize cytokine levels to predict sustained response (SR) to alpha interferon (IFN alpha) therapy in chronic hepatitis C patients, and to determine the relationship between serum tumor necrosis factor alpha (TNF alpha), interleukin (IL) IL 6, IL 8, IL 12, transforming growth factor beta (TGF beta 1) and the degree of liver damage as reflected by traditional markers.

DESIGN AND METHODS

Serum cytokine levels were assessed using ELISA in 18 patients included in a controlled clinical trial of IFN alpha.

RESULTS

Of the 18 patients, 27% were sustained responders (SR), 27% were response and relapse responders (RR), and 46% were non-responders (NR). Multivariate analysis showed that a low serum TNF alpha level and high serum IL 8 levels were independent factors associated with SR to IFN alpha therapy. Serum TNF alpha level highly correlated with viral load and genotype predictive values (p < 0.001). Therapy lowered the IL 6 and IL 12 profile. TGF beta 1 levels in serum are positively correlated with fibrinogenesis.

CONCLUSIONS

IFN alpha therapy modulates immune response to hepatitis C virus, contributing to sustained response.

Treatment of chronic viral hepatitis

Interferon-alpha therapy has proved effective for up to 40% of patients with adult-acquired chronic hepatitis B virus (HBV) infection and for 20-25% of those with chronic hepatitis C virus (HCV) infection. Nucleoside analogues, such as lamivudine and famciclovir, are showing promise as antiviral agents for chronic HBV and the combination of interferon-alpha and ribavirin is proving to be successful therapy for 40-50% of patients with chronic HCV. In this article we review current therapy and discuss future strategies of the therapy of chronic viral hepatitis.