In vivo treatment with interleukin 12 protects mice from immune abnormalities observed during murine acquired immunodeficiency syndrome (MAIDS)

Dose of Retroviral Infection Determines Induction of Antiviral NK Cell Responses

Natural killer (NK) cells are part of the innate immune system and recognize virus-infected cells as well as tumor cells. Conflicting data about the beneficial or even detrimental role of NK cells in different infectious diseases have been described previously. While the type of pathogen strongly influences NK cell functionality, less is known about how the infection dose influences the quality of a NK cell response against retroviruses. In this study, we used the well-established Friend retrovirus (FV) mouse model to investigate the impact of virus dose on the induction of antiviral NK cell functions. High-dose virus inoculation increased initial virus replication compared to that with medium- or low-dose viral challenge and significantly improved NK cell activation. Antiviral NK cell activity, including in vivo cytotoxicity toward infected target cells, was also enhanced by high-dose virus infection. NK cell activation following high-dose viral challenge was likely mediated by activated dendritic cells (DCs) and macrophages and the NK cell-stimulating cytokines interleukin 15 (IL-15) and IL-18. Neutralization of these cytokines decreased NK cell functions and increased viral loads, whereas IL-15 and IL-18 therapy improved NK cell activity. Here we demonstrate that virus dose positively correlates with antiviral NK cell activity and function, which are at least partly driven by IL-15 and IL-18. Our results suggest that NK cell activity may be therapeutically enhanced by administering IL-15 and IL-18 in virus infections that inadequately activate NK cells.

IMPORTANCE In infections with retroviruses, like HIV and FV infection of mice, NK cells clearly mediate antiviral activities, but they are usually not sufficient to prevent severe pathology. Here we show that the initial infection dose impacts the induction of an antiviral NK cell response during an acute retroviral infection, which had not investigated before. High-dose infection resulted in a strong NK cell functionality, whereas no antiviral activities were detected after low- or medium-dose infection. Interestingly, DCs and macrophages were highly activated after high-dose FV challenge, which corresponded with increased levels of NK cell-stimulating cytokines IL-15 and IL-18. IL-15 and IL-18 neutralization decreased NK cell functions, whereas IL-15 and IL-18 therapy improved NK cell activity. Here we show the importance of cytokines for NK cell activation in retroviral infections; our findings suggest that immunotherapy combining the well-tolerated cytokines IL-15 and IL-18 might be an interesting approach for antiretroviral treatment.

Insufficient natural killer cell responses against retroviruses: how to improve NK cell killing of retrovirus-infected cells

Natural killer (NK) cells belong to the innate immune system and protect against cancers and a variety of viruses including retroviruses by killing transformed or infected cells. They express activating and inhibitory receptors on their cell surface and often become activated after recognizing virus-infected cells. They have diverse antiviral effector functions like the release of cytotoxic granules, cytokine production and antibody dependent cellular cytotoxicity. The importance of NK cell activity in retroviral infections became evident due to the discovery of several viral strategies to escape recognition and elimination by NK cells. Mutational sequence polymorphisms as well as modulation of surface receptors and their ligands are mechanisms of the human immunodeficiency virus-1 to evade NK cell-mediated immune pressure. In Friend retrovirus infected mice the virus can manipulate molecular or cellular immune factors that in turn suppress the NK cell response. In this model NK cells lack cytokines for optimal activation and can be functionally suppressed by regulatory T cells. However, these inhibitory pathways can be overcome therapeutically to achieve full activation of NK cell responses and ultimately control dissemination of retroviral infection. One effective approach is to modulate the crosstalk between NK cells and dendritic cells, which produce NK cell-stimulating cytokines like type I interferons (IFN), IL-12, IL-15, and IL-18 upon retrovirus sensing or infection. Therapeutic administration of IFNα directly increases NK cell killing of retrovirus-infected cells. In addition, IL-2/anti-IL-2 complexes that direct IL-2 to NK cells have been shown to significantly improve control of retroviral infection by NK cells in vivo. In this review, we describe novel approaches to improve NK cell effector functions in retroviral infections. Immunotherapies that target NK cells of patients suffering from viral infections might be a promising treatment option for the future.

Golgi phosphoprotein 2 in physiology and in diseases

Golgi phosphoprotein 2 (GOLPH2, also termed GP73 and GOLM1) is a type II transmembrane protein residing in the cis and medial-Golgi cisternae. GOLPH2 is predominantly expressed in the epithelial cells of many human tissues. Under poorly defined circumstances, GOLPH2 can be cleaved and released to the extracellular space. Despite of its relatively “young age” since the first description in 2000, the physiological and pathological roles of GOLPH2 have been the subject that has attracted considerable amount of attention in recent years. Here, we review the history of GOLPH2’s discovery and the multitude of studies by many groups around the world aimed at understanding its molecular, cellular, physiological, and pathogenic activities in various settings.

Current investigational drugs in psoriasis

INTRODUCTION

The advent of biologic therapies has revolutionized the treatment of psoriasis. Increased understanding of immunogenetic pathways has allowed for the development of more selective targeted biologic therapies. Multiple new treatments are currently in development for the treatment of psoriasis. Preliminary data for many of these agents, particularly with regard to agents targeting the IL-23/Th17 pathway, are promising. Proven long-term safety, however, is an absolute necessity with newly developed drugs, and should, therefore, still be considered second-line agents to current established treatments with long-term safety data.

AREAS COVERED

This review details the mechanisms of action of drugs currently in development or in clinical trials for the treatment of psoriasis, using clinical trial registries and associated publications. Readers will gain a comprehensive overview about the mechanism of action of emerging treatments targeting various immune pathways deeply involved in psoriasis. Pathogenesis, clinical efficacy and safety data for these treatments are discussed where available.

EXPERT OPINION

Psoriasis remains a heavily undertreated systemic immune-mediated disease despite increased understanding of immunopathogenesis of the disease and advent of a multitude of novel therapeutic agents with potentially improved bioavailability and safety profiles. Limitations, however, remain in the realm of topical agents for treatment of mild to moderate psoriasis, which has seen little progress over the years. A concerted effort will need to be made among researchers, clinicians and patient advocacy groups to ensure new therapeutic agents are developed and gain proper exposure.

Viral reservoir is suppressed but not eliminated by CD8 vaccine specific lymphocytes

It has long been postulated that while CD8 lymphocytes are capable of suppressing human immunodeficiency virus (HIV)-1 replication it is unlikely that the viral reservoirs once formed can be cleared. Our previous studies demonstrate that co-immunizing cynomologous macaques with a simian/human immunodeficiency virus (SHIV) DNA-based vaccines induces a strong cellular immune response that is able to suppress viral replication. We further demonstrated that interleukin (IL)-12 could significantly enhance the vaccine specific CD8 lymphocyte response. In this manuscript cynomologous macaques were vaccinated with a SHIV DNA-based vaccine co-delivered with IL-12. The macaques were then challenged with SHIV89.6p. Two years post-immunization and viral challenge we transiently depleted CD8(+) T cells. Plasma viral load increased, demonstrating the central role of CD8(+) T cells in viral suppression yet an inability to clear the viral reservoirs. Furthermore, in the data presented here, we found a higher number of IFN-gamma producing vaccine specific cells did not enhance suppression of viral replication.

The role of MHC haplotypes H2d/H2b in mouse resistance/susceptibility to cyst formation is influenced by the lineage of infective Toxoplasma gondii strain

Toxoplasma gondii strains displaying the Type I/III genotype are associated with acquired ocular toxoplasmosis in humans. Here, we used a mice model to characterize some immunological mechanisms involved in host resistance to infection with such strains. We have chosen the Type I/III strains D8, G2 and P-Br, which cause a chronic infection in mice that resembles human toxoplamosis. Mice deficient of molecules MyD88, IFN-gamma, and IL-12 were susceptible to all three parasite strains. This finding indicates the importance of innate mechanisms in controlling infection. On the other hand, MHC haplotype did not influenced resistance/susceptibility; since mice lineages displaying a same genetic background but different MHC haplotypes (H2b or H2d) developed similar mortality and cyst numbers after infection with those strains. In contrast, the C57BL/6 genetic background, and not MHC haplotype, was critical for development of intestinal inflammation caused by any of the studied strains. Finally, regarding effector mechanisms, we observed that B and CD8+ T lymphocytes controlled survival,whereas the inducible nitric oxide synthase influenced cyst numbers in brains of mice infected with Type I/III strains. These findings are relevant to further understanding of the immunologic mechanisms involved in host protection and pathogenesis during infection with T. gondii.

Interleukin-12, interleukin-23, and psoriasis: Current prospects

The clinical phenotype of psoriasis results from infiltration of T cells in the skin and elaboration of inflammatory cytokines. Interleukin (IL)-12 and, more recently, IL-23 have been implicated in the pathogenesis of psoriatic lesions. New therapies, including a monoclonal antibody against a subunit shared by IL-12 and IL-23, have been developed to treat psoriasis. Our purpose was to review the literature on IL-12 and IL-23 as a basis for understanding the use of anti-IL-12/IL-23 therapy for psoriasis. A review of English-language articles was performed using PubMed to identify articles pertaining to IL-12, IL-23, and psoriasis. IL-12 and IL-23 share a common subunit (p40) and have a distinct subunit (p35 and p19, respectively). Transgenic mice that overexpress IL-12 p40 develop inflammatory skin lesions. Both IL-12 knockout mice, which are deficient in IL-12, and human beings with a genetic IL-12 deficiency show increased susceptibility to intracellular pathogens and defective delayed-type hypersensitivity responses. These genetic deficiency states suggest the potential for adverse side effects from clinical administration of anti IL-12 p40 therapy. IL-12 p40 antibody was well tolerated in a phase I clinical trial with few adverse events and substantial improvements in psoriasis in most individuals. There was dose-dependent efficacy and substantial improvement in a larger cohort of patients in a phase II clinical trial. Larger and longer trials of anti IL-12/IL-23 therapies are needed to assess their clinical use and potential for infection and other adverse events.

The Fas death pathway controls coordinated expansions of type 1 CD8 and type 2 CD4 T cells in Trypanosoma cruzi infection

We investigated the role of the Fas ligand (FasL)/Fas death pathway on apoptosis and cytokine production by T cells in Trypanosoma cruzi infection. Anti-FasL, but not anti-TNF-alpha or anti-TRAIL, blocked activation-induced cell death of CD8 T cells and increased secretion of IL-10 and IL-4 by CD4 T cells from T. cruzi-infected mice. CD4 and CD8 T cells up-regulated Fas/FasL expression during T. cruzi infection. However, Fas expression increased earlier in CD8 T cells, and a higher proportion of CD8 T cells was activated and expressed IFN-gamma compared with CD4 T cells. Injection of anti-FasL in infected mice reduced parasitemia and CD8 T cell apoptosis and increased the ratio of CD8:CD4 T cells recovered from spleen and peritoneum. FasL blockade increased the number of activated T cells, enhanced NO production, and reduced parasite loads in peritoneal macrophages. Injection of anti-FasL increased IFN-gamma secretion by splenocytes responding to T. cruzi antigens but also exacerbated production of type 2 cytokines IL-10 and IL-4 at a late stage of acute infection. These results indicate that the FasL/Fas death pathway regulates apoptosis and coordinated cytokine responses by type 1 CD8 and type 2 CD4 T cells in T. cruzi infection.

Reconstitution of erythroid, megakaryocyte and myeloid hematopoietic support function with neutralizing antibodies against IL-4 and TGFbeta1 in long-term bone marrow cultures infected with LP-BM5 murine leukemia virus

Murine acquired immunodeficiency syndrome (MAIDS) induced by a defective LP-BM5 murine leukemia virus (MuLV) produces hematopoietic cytopenias similar to HIV in patients with AIDS. The pathogenesis of MAIDS induced cytopenias remains obscure; however, direct retroviral infection of bone marrow stroma has been implicated to play a role. To evaluate the consequential effect of viral infection, primary stromal cell cultures were transiently incubated in vitro with LP-BM5 MuLV viral supernatant. Reverse transcription polymerase chain reaction (RT-PCR) and Southern blot hybridization revealed that defective LP-BM5 MuLV infection resulted in elevated levels of IL-4 and TGFbeta1 transcript expression in infected stromal cells. The increased expression of both IL-4 and TGFbeta1 transcripts was associated with enhanced production of corresponding proteins as determined by quantitative western blot analyses. Hematopoietic reconstitution assays revealed that the hematopoietic support function of stromal cells was significantly reduced following transient exposure to LP-BM5 MuLV. The production of nonadherent mononuclear cells and the growth of myeloid, megakaryocyte and erythroid lineages were all suppressed in infected cultures. Culture supernatant conditioned by infected stromal cells demonstrated growth-inhibitory activity for hematopoietic progenitor colony formation. This growth-inhibitory activity could be significantly abolished by addition of anti-IL-4 and/or anti-TGFbeta1 neutralizing antibodies to the culture supernatant or directly to the stromal cell cultures. This study demonstrates LP-BM5 MuLV increases two known cytokines to suppress hematopoiesis implicating viral infection can directly suppress hematopoiesis mediated by inhibitors released from marrow stroma.

The role of IL-12, IL-23 and IFN-gamma in immunity to viruses

IL-12, IL-23 and IFN-γ form a loop and have been thought to play a crucial role against infectious viruses, which are the prototype of “intracellular” pathogens. In the last 10 years, the generation of knock-out (KO) mice for genes that control IL-12/IL-23-dependent IFN-γ-dependent mediated immunity (STAT1, IFN-γR1, IFNγR2, IL-12p40 and IL-12Rβ1) and the identification of patients with spontaneous germline mutations in these genes has led to a re-examination of the role of these cytokines in anti-viral immunity. We here review viral infections in mice and humans with genetic defects in the IL-12/IL-23-IFN-γ axis. A comparison of the phenotypes observed in KO mice and deficient patients suggests that the human IL-12/IL-23-IFN-γ axis plays a redundant role in immunity to most viruses, whereas its mouse counterparts play a more important role against several viruses.

Quantitation of defective and ecotropic viruses during LP-BM5 infection by real time PCR and RT-PCR

Murine AIDS (MAIDS) is a pathology induced by the LP-BM5 murine leukaemia virus mixture in susceptible strains of mice such as C57BL/6J resulting in lymphoproliferation and progressive immunodeficiency. The etiologic agent of this pathology is BM5d, a replication defective virus. BM5e is a replication competent virus in the viral mixture that functions as a helper virus. This paper describes real time PCR and RT-PCR assays for quantitation of the proviral DNA and viral RNA of BM5d and BM5e. Data is presented describing the change in BM5d and BM5e proviral DNA levels and viral RNA levels in both blood and spleen in the first 8 weeks of infection. Infected mice have increasing levels of BM5d and BM5e viral DNA and RNA detectable from as early as 2 weeks post infection. Similar levels of proviral DNA was found for BM5d and BM5e in PBMC and spleen, however higher levels of BM5e viral RNA were observed in both tissues throughout infection. The assays described can be used as both a diagnostic tool and to investigate the direct effect of treatments on the BM5d and BM5e viruses and MAIDS development.

Use of recombinant cytokines for optimized induction of antiviral immunity against SIV in the nonhuman primate model of human AIDS

Outbreaks of infectious diseases such as HIV and the much televised and attention-getting outbreaks of diseases such as Ebola, Hantaviruses, and the most recent outbreak of SARS have induced a significant new interest in the formulations and more importantly the science of vaccinology, which has previously to a large extent been conducted empirically. Our laboratory has focused on the use of recombinant nonhuman primate cytokines as adjunctive therapies for inducing antigen-specific immune responses in monkeys because most recombinant human cytokines appear to be immunogenic. This article provides a summary of our work with such cytokines, which includes attempts to define optimum dosing schedules that lead to optimal primary and lasting memory antigen-specific immune responses.

The use of growth factors and cytokines to treat opportunistic infections in HIV-1 disease

The success of highly active antiretroviral therapy (HAART) in reducing AIDS-related mortality means that in regions where HAART is available, HIV infection may now be regarded as a chronic disease. However the inability of HAART to eliminate HIV-1 from various anatomical and cellular reservoirs within the body means that HIV-infected individuals require life-long treatment with therapy that can have significant side effects. Management of HIV disease is therefore increasingly focused on drug-related toxicities and the improvement of current HAART regimens. Here we review the potential use of immunomodulatory cytokines to directly or indirectly stimulate the mononuclear phagocyte system as adjuncts to current HIV treatment as well as their use in the management of opportunistic infections in individuals who develop immunodeficiency. We argue that cytokines, which stimulate mononuclear phagocyte activity against opportunistic pathogens, may be useful for the treatment of individuals who develop recurrent opportunistic infections. Cytokines may act synergistically with antimicrobial agents to improve outcomes, which is of particular importance since recurrent infections frequently result in resistance to standard antimicrobial treatments. Before their use can be advocated however, given their toxicity and significant cost, the potential benefits of cytokines must be demonstrated in larger clinical trials.

IL-12 and IL-18 act in synergy to clear vaccinia virus infection: involvement of innate and adaptive components of the immune system

Development of a protective host response against intracellular pathogens requires innate and cell-mediated immune responses, with cytokines playing an important role in host defences. Different studies in mice have shown that IL-12 can promote protective immunity to a variety of viruses but, during virus infection, little is known about the in vivo function of IL-18 alone or in combination with IL-12. Using recombinant vaccinia viruses (rVVs) expressing IL-12 and IL-18, the antiviral role of both cytokines in mice has been analysed. The specific anti-VV immune response elicited and the persistence of the virus in target tissues were compared in BALB/c mice inoculated with rVVs expressing IL-12 and IL-18 either singly or in combination. Delivery of IL-12 and IL-18 by rVVs in mice induced a significant enhancement in virus clearance from ovaries and spleen, greater than that expected from the sum of action of both cytokines. Virus clearance involved NK and T cells, as demonstrated in mice depleted of NK cells and in immunodeficient SCID animals. Th1 parameters (CD8(+) T cell response and IgG2a : IgG1 ratios) were increased in mice inoculated with rVVs expressing both IL-12 and IL-18 as compared to those animals receiving a single cytokine. These findings indicate that when IL-12 and IL-18 are delivered by rVVs, different mechanisms involving both the innate and specific arms of the immune system act as mediators in the synergistic action of IL-12 and IL-18, leading to VV clearance. These results are of interest for the design of prophylactic as well as therapeutic VV-based strategies.

A new one-step RT-PCR method for virus quantitation in murine AIDS

The causative agent of murine AIDS (MAIDS) in C57BL/6 mice, is a defective murine leukemia virus (BM5d) that requires the replication-competent helper virus (BM5e). Since this animal model of immunodeficiency, which shows many similarities to human AIDS, is also used to test the efficacy and toxicity of antiretroviral drugs, a method that allows the quantitative detection of both viruses would be very useful also if hampered potentially by endogenous viral sequences usually present in mice. While BM5d alone could induce the disease, the effect of BM5e on the immune system of diseased mice is unclear. A specific and reliable one-step RT-PCR method was developed for the co-amplification, with the same efficiency, of BM5d or BM5e with ss-actin used as an internal standard. The standard curves produced with cloned cDNA sequences (ss-actin and BM5d or BM5e) assure that all samples are analyzed during the exponential phase of the reaction. Using this new assay which provided a dynamic range of at least four-log-unit, the ratio of initial absolute amounts of the virus and ss-actin RNA was determined, obtaining quantitative information on virus-specific cellular-transcript in the lymph nodes and spleen during the natural history of the disease and during therapeutic regimens.

Quantitative analysis of LP-BM5 murine leukemia retrovirus RNA using real-time RT-PCR

Murine AIDS (MAIDS) develops in susceptible mouse strains after infection with the LP-BM5 murine leukemia virus (MuLV) complex that contains a mixture of defective (BM5def) and replication-competent viruses. While the BM5def virus is the causative agent in MAIDS, the replication-competent viruses in LP-BM5, including ecotropic MuLV (BM5eco), are required for BM5def propagation and thus function as helper viruses. We describe quantitative real-time RT-PCR assays for RNA encoded by the BM5def and BM5eco components of LP-BM5. The assays were used to standardize better the input doses of LP-BM5 viruses across viral preparations and to quantify BM5def and BM5eco gag RNA levels in spleen and blood cells from MAIDS-susceptible and -insusceptible infected mice. Spleens of MAIDS-susceptible infected mice harbored approximately similar levels of BM5def gag RNA as infected spleens of mice that are insusceptible to MAIDS due to lack of CD40. In contrast, the same infected spleens of CD40-deficient mice contained substantially higher (up to 10-fold) levels of BM5eco gag RNA compared with susceptible controls. Similar to that seen in spleen, infected blood of CD40-deficient mice contained similar levels of BM5def gag as susceptible strains, but increased levels (up to threefold) of BM5eco gag RNA. The assays described below can be used to characterize better the contributions of different functional viral components of the LP-BM5 mixture to the development of MAIDS.

Overexpression of interleukin-15 prevents the development of murine retrovirus-induced acquired immunodeficiency syndrome

LP-BM5 murine leukemia virus (MuLV) infection causes murine acquired immunodeficiency syndrome (MAIDS), a disease characterized by varied functional abnormalities of immunocompetent cells. We found that MAIDS progression was severely retarded in IL-15 transgenic (Tg) mice constructed with cDNA encoding secretable IL-15 under the control of an MHC class I promoter. Several immune defects, including impaired natural killer activity, depressed IFN-gamma production by T cells stimulated with anti-T cell receptor cross-linking, and increased susceptibility to Mycobacterium bovis infection, were prevented in IL-15 Tg mice inoculated with LP-BM5 MuLV. Cytotoxic T lymphocyte response to a highly antigenic 10-mer peptide encoded by LP-BM5-defective virus gag p12 gene was detected in the spleen and peritoneal exudate cells from IL-15 Tg mice infected with LP-BM5 MuLV. Intramuscular injection of cDNA encoding secretable IL-15 also prevented the development of MAIDS. These results indicate that IL-15 prevents the progression of MAIDS and may provide insight into an immunotherapeutic approach using the IL-15 gene for controlling retrovirus-induced immunodeficiency.

A Phase I, placebo-controlled trial of multi-dose recombinant human interleukin-12 in patients with HIV infection

OBJECTIVES

Interleukin (IL)-12 is a cytokine that stimulates T lymphocytes and natural killer cells to generate a Type 1 T-helper lymphocyte immune response. The primary objective of this study was to determine the safety and immunologic activity of repeated recombinant human IL-12 (rhIL-12) dosing in HIV-infected patients over a broad range of the HIV disease spectrum.

DESIGN

A randomized, placebo-controlled, Phase 1 trial design was chosen to control for the effects of HIV disease alone on safety and immunologic measurements.

METHODS

HIV-infected patients on antiretroviral therapy received rhIL-12 or placebo twice weekly for 4 weeks. Subjects were monitored for safety and changes in absolute lymphocyte subset number, serum interferon (IFN)gamma and neopterin levels, plasma HIV RNA level, peripheral blood mononuclear cell (PBMC)-inducible IFNgamma responses to mitogen, and PBMC proliferative responses to phytohemagglutinin, tetanus, Candida, Mycobacterium avium complex, streptokinase, and HIV p24 and gp160 antigens.

RESULTS

rhIL-12 was well tolerated at doses up to 100 ng/kg in subjects enrolled with CD4 cell counts < 50 x 10(6) cells/l and at all doses in subjects with CD4 cell counts of 300 x 10(6)-500 x 10(6) cells/l. rhIL-12 resulted in dose-related increases in serum neopterin (particularly in subjects with baseline CD4 cell counts of 300-500 x 10(6) cells/l) but in no significant changes in other immunologic measurements or plasma HIV RNA levels.

CONCLUSIONS

rhIL-12 dosed twice weekly at < or = 100 ng/kg was well tolerated in HIV-infected patients and resulted in dose-related increases in serum neopterin (possibly reflecting the effect of some degree of IFNgamma induction). However, there was no evidence of improvement in antigen-specific immune response.

Chemical sympathectomy has no effect on the severity of murine AIDS: murine AIDS alone depletes norepinephrine levels in infected spleen

Numerous studies have shown that alterations in sympathetic nervous system (SNS) function produced by beta-adrenergic receptor blockade or chemical sympathectomy can produce changes in T and B lymphocyte function and both innate and acquired immune responses. However, fewer studies have investigated changes in immune response following SNS alterations in animal models of disease. We tested whether blocking SNS activity using 6-OHDA or the beta-receptor antagonist nadolol alters the typical pattern in production of T helper 1 (Th1) and Th2 cytokines seen in cultures of spleen cells from C57BL/6 mice infected with murine AIDS (MAIDS). We found that neither method of sympathetic blockade affected cytokine response to MAIDS. We also found that the norepinephrine concentration and content of the spleen were reduced dramatically by the MAIDS infection itself at 3 and 6 weeks after LP-BM5 inoculation. This finding has not been previously reported in mice with MAIDS and suggests that the viral infection itself produces a functional sympathectomy in the spleen, a target of that infection.

Temporal effects of gamma interferon deficiency on the course of Friend retrovirus infection in mice

The current studies demonstrate complex and seemingly contradictory effects by gamma interferon (IFN-gamma) on Friend virus (FV) infection. Both temporal and tissue-specific effects were observed. During the first week of infection, IFN-gamma-deficiency caused increased levels of FV infection in multiple tissues. Surprisingly, however, by 2 weeks postinfection, IFN-gamma-deficient mice had significantly lower levels of infection in both the spleen and bone marrow compared to wild-type mice. The rapid reduction of virus in the IFN-gamma-deficient mice correlated with a more rapid virus-neutralizing antibody response than was observed in the wild-type mice. Furthermore, the virus-neutralizing antibody response in wild-type mice could be accelerated by ablation of their IFN-gamma response. Although the IFN-gamma-deficient mice developed an accelerated virus-neutralizing antibody response, they did not class-switch to immunoglobulin G class immunoglobulins nor could they maintain long-term virus-neutralizing antibody titers. Eventually, all of the IFN-gamma-deficient mice failed to keep persistent virus in check and developed fatal FV-induced erythroleukemia.

Essential roles for CD8+ T cells and gamma interferon in protection of mice against retrovirus-induced immunosuppression

It is known that both animal and human retroviruses typically cause immunosuppression in their respective hosts, but the mechanisms by which this occurs are poorly understood. The present study uses Friend virus (FV) infections of mice as a model to determine how major histocompatibility complex (MHC) genes influence immunosuppression. Previously, MHC-I genes were shown to influence antibody responses to potent antigenic challenges given during acute FV infection. The mapping of an immune response to an MHC-I gene implicated CD8+ T cells in the mechanism, so we directly tested for their role by using in vivo CD8+ T-cell depletions. Mice resistant to FV-induced immunosuppression became susceptible when they were depleted of CD8+ T cells. Resistance also required gamma interferon (IFN-gamma), as in vivo neutralization of IFN-gamma converted mice from a resistant to susceptible phenotype. On the other hand, susceptibility to FV-induced immunosuppression was dependent on the immunosuppressive cytokine, interleukin-10 (IL-10), as antibody responses were restored in susceptible mice when IL-10 function was blocked in vivo. Thus, FV-induced immunosuppression of antibody responses involves complex mechanisms controlled at least in part by CD8+ T cells.

Interleukin-12 in the treatment of chronic hepatitis B and C

Interleukin-12 plays a central role in mounting an effective cellular immune response directed towards elimination of intracellular pathogens. In two open label, multicenter, dose-escalation phase I/II studies tolerability, pharmacokinetics, pharmacodynamics, and efficacy of subcutaneously administered recombinant human interleukin-12 (rHuIL-12) was assessed in the treatment of chronic hepatitis B and C. Forty-six patients with chronic hepatitis B and 60 patients with chronic hepatitis C were treated for 12 and 10 consecutive weeks, respectively. rHuIL-12 was generally well tolerated, but was associated with temporary decreases in neutrophils and lymphocyte counts, and with elevations in serum transaminases and bilirubin. Serum IL-12 levels observed were higher at 0.5 microg/kg compared with 0.25 microg/kg doses, suggesting a dose-related increase in systemic exposure of IL-12. Measurable levels of interferon-gamma were also observed at the highest dose of 0.5 microg/kg. At the end of treatment HBV DNA clearance was greater in patients treated with 0.50 microg/kg (25%) or with 0.25 microg/kg (13%) compared with those given 0.03 microg/kg. In patients with chronic hepatitis C, HCV RNA remained detectable in all patients. A more than 50% decrease in pretreatment HCV RNA levels was observed in 3/16 patients (0.03 microg/kg), in 3/14 (0.10 microg/kg), in 6/15 (0.25 microg/kg), and in 8/15 patients of the 0.5 microg/kg dose group. In conclusion, antiviral activity of rHuIL-12 in patients with chronic hepatitis B or C does not appear to be advantageous in comparison to other currently available treatments.

Il-12 antagonism enhances apoptotic death of T cells within hepatic allografts from Flt3 ligand-treated donors and promotes graft acceptance

Mouse livers are accepted across MHC barriers and induce donor-specific tolerance without immunosuppressive therapy. By contrast, livers from donors treated with Flt3 ligand, which dramatically increases hepatic interstitial dendritic cells, are rejected acutely (median survival time 5 days). This switch from tolerance to rejection is associated with a marked reduction in apoptotic activity of graft-infiltrating cells. We hypothesized that IL-12 production by enhanced numbers of donor APC might inhibit apoptosis, promote expansion of Th1 cells, and play a key role in liver rejection. Therefore, C3H (H2(k)) recipients of liver grafts from Flt3 ligand-treated B10 donors were given neutralizing anti-IL-12 mAb (200 or 500 microg) on days 0 and 2 after transplant. Graft survival was markedly prolonged at the higher mAb dose, with 50% of grafts surviving >100 days. This effect was associated with reductions in IFN-gamma gene transcripts within the graft-infiltrating cell population and with reductions in circulating IFN-gamma and IL-10 levels, donor-specific CTL and NK cell activities, and circulating alloantibody levels. At the same time, there were marked increases in apoptotic (TUNEL(+)) CD4(+) and especially CD8(+) cells, both within the grafts and in spleens of anti-IL-12 mAb-treated mice. In vitro, exogenous IL-12 inhibited apoptotic death induced in naive allogeneic T cells by liver nonparenchymal cells. These findings suggest that suppression of rejection by IL-12 antagonism, linked to restoration of apoptotic activity within the peripheral alloreactive T cell population, is important for liver allograft survival and tolerance induction.

Glycyrrhizin restores the impaired IL-12 production in thermally injured mice

Mice 6 days after thermal injury (TI-mice) did not respond to lipopolysaccharide (LPS) stimulation for production of serum interleukin 12 (IL-12; 2 h after LPS stimulation, <20 pg/ml in TI-mice; 1091+/-162 pg/ml in normal mice). However, 2 h after LPS stimulation, 1456+/-118 pg/ml of IL-12 were demonstrated in sera of TI-mice previously treated with a 10 mg/kg i.p. dose of glycyrrhizin (GR). IL-12 was not induced by LPS in sera of normal mice inoculated with burn-associated type 2 T cells (IL-4/IL-10-producing CD8+CD11b+TCRgamma/delta+T cells isolated from spleens of TI-mice). However, IL-12 production was induced by LPS in sera of these mice previously treated with GR or a mixture of monoclonal antibodies (mAbs) for type 2 cytokines. Also, IL-12 production was induced by LPS in TI-mice inoculated with CD4+T cells from spleens of GR-treated normal mice (GR-CD4+T cells, 5x10(6)cells/mouse). Since GR-CD4+T cells have been shown to be antagonistic cells against production of type 2 cytokines by burn-associated type 2 T cells, these results indicate that IL-12 unresponsiveness shown in TI-mice is recovered by GR through the regulation of burn-associated type 2 T cell responses.

A mechanism of interleukin-12 unresponsiveness associated with thermal injury

An unresponsive state for the production of interleukin-12 (IL-12) is commonly observed in animals and patients with severe thermal injuries. In the present study, the participation of corticosteroids, prostaglandin E(2) (PGE(2)), and type 2 cytokines, which appeared in association with thermal injury, on the burn-associated IL-12 unresponsiveness was studied. These substances have been described as inhibitors of IL-12 production. Less than 20 pg/ml serum IL-12 was produced in thermally injured mice (TI-mice) after stimulation with lipopolysaccharide (LPS), while 1037 pg/ml IL-12 was detected in sera of unburned mice equally stimulated with LPS. Almost complete restoration of the impaired IL-12 production was witnessed in TI-mice after treatment with soluble IL-4 receptor (50 ng/mouse, 2 h and 2 days after thermal injury). However, IL-12 was not induced by LPS stimulation in TI-mice treated with an inhibitor of PGE(2) (indomethacin, 0.1-5 mg/kg) or an inhibitor of corticosteroid production (ketoconazole, 10 mg/kg). LPS-stimulated IL-12 production was also impaired in normal mice inoculated with burn-associated type 2 T cells. In addition, in the presence of 1 microg/ml LPS, naive macrophages cocultured with burn-associated type 2 T cells did not produce IL-12 in their culture fluids, while IL-12 was produced by LPS-stimulated naive macrophages that were cocultured with naive splenic CD8(+) T cells. These results suggest that the IL-12-unresponsive state demonstrated in TI-mice is associated mainly with type 2 cytokines released from burn-associated type 2 T cells.

In vitro HIV-specific CTL activity from HIV-seropositive individuals is augmented by interleukin-12 (IL-12)

IL-12 production is reduced in HIV infection, and recombinant human IL-12 (rhIL-12) augments in vitro HIV-specific proliferative responses in PBMC from HIV-seropositive individuals. To determine whether rhIL12 could also augment HIV-specific CTL responses we studied 41 HIV-seropositive individuals. Recombinant hIL-12 increased the detectable in vitro HIV-specific CD8 CTL activity of PBMC taken from HIV-seropositive individuals with CD4 counts >500 cells/microl and from some individuals with lower CD4 counts. IL-12 increased cell recovery in cultures of PBMC from HIV-seropositive individuals with CD4 counts >500 cells/microl and also increased the precursor CTL frequency. However, the increase in HIV-specific CTL activity was not due to IL-2 or IFN-gamma production or an increase in the number of cells with surface markers characteristic of CTL effector cells. This study demonstrates that rhIL-12 augments in vitro HIV-specific CTL activity and provides evidence to justify further investigation within clinical trials of this cytokine in HIV infection.

Role of interleukin-4 (IL-4), IL-12, and gamma interferon in primary and vaccine-primed immune responses to Friend retrovirus infection

The immunological resistance of a host to viral infections may be strongly influenced by cytokines such as interleukin-12 (IL-12) and gamma interferon (IFN-gamma), which promote T helper type 1 responses, and IL-4, which promotes T helper type 2 responses. We studied the role of these cytokines during primary and secondary immune responses against Friend retrovirus infections in mice. IL-4- and IL-12-deficient mice were comparable to wild-type B6 mice in the ability to control acute and persistent Friend virus infections. In contrast, more than one-third of the IFN-gamma-deficient mice were unable to maintain long-term control of Friend virus and developed gross splenomegaly with high virus loads. Immunization with a live attenuated vaccine virus prior to challenge protected all three types of cytokine-deficient mice from viremia and high levels of spleen virus despite the finding that the vaccinated IFN-gamma-deficient mice were unable to class switch from immunoglobulin M (IgM) to IgG virus-neutralizing antibodies. The results indicate that IFN-gamma plays an important role during primary immune responses against Friend virus but is dispensable during vaccine-primed secondary responses.

Kinetics of cytokine gene expression in experimental chagasic cardiomyopathy: tissue parasitism and endogenous IFN-gamma as important determinants of chemokine mRNA expression during infection with Trypanosoma cruzi

We investigated the kinetics of parasite replication, leukocyte migration, and cytokine/chemokine mRNA expression in the heart tissue from animals infected with the Colombiana strain of Trypanosoma cruzi. Cardiac tissue parasitism was noticeable at 15 days, peaked around 30 days and was dramatically reduced at 120 days postinfection (p.i.). Kinetic studies showed that the inflammatory infiltrate was dominated by the presence of alphabetaT CD3(+ )CD4(+ )CD8(-), alphabetaT CD3(+ )CD4(-)CD8(+ )lymphocytes and macrophages. The mRNA expression of the monokines IL-1beta and IL-12(p40) was elevated at 15 days p.i. and controlled at later time points. In contrast, TNF-alpha mRNA was expressed throughout the infection. Interestingly, we found that at 15 and 30 days p.i. cytokine expression was dominated by the presence of IFN-gamma mRNA, whereas at 60 days or later time points the balance of type 1 and type 2 cytokines was switched in favor of IL-4 and IL-10 mRNAs. The chemokine mRNAs encoding JE, MIP-1alpha, MIP-1beta, KC, and MIP-2 were all mainly expressed at 15 and/or 30 days p.i. and diminished thereafter. In contrast, the expression of RANTES, MIG and IP-10 mRNAs was augmented at 15 days p.i. and persisted at high levels up to 120 days p.i. Taken together, our results indicate that regulation of IFN-gamma and chemokine expression, associated with decreased tissue parasitism, may be largely responsible for the control of inflammation and immunopathology observed in the cardiac tissue of animals infected with T. cruzi.

The autoimmune accelerating yaa mutation does not accelerate murine AIDS

Murine acquired immunodeficiency syndrome (MAIDS) is characterized by lymphoproliferation, polyclonal B cell activation resulting in the production of autoantibodies, and a progressive immunodeficiency. These are all hallmarks of some autoimmune diseases. Yaa is a Y-chromosome-linked gene that accelerates autoimmune diseases in some autoimmune-prone strains of mice. To further elucidate a possible relationship with autoimmunity, the effect of the Yaa gene on MAIDS was investigated. Analysis of phenotypic and functional disease parameters revealed that Yaa does not accelerate MAIDS disease. This is probably due to the generalized activation of most or all lymphoid cells in MAIDS, which cannot be enhanced by the Yaa gene. This result is in accordance with the selective enhancing effect of the Yaa gene on the immune response against self and foreign antigens in a specific genetic background. It suggests that the autoimmune response associated with MAIDS is a secondary phenomenon. Interestingly, even in wild-type C57BL/6 mice, autoantibody production may contribute overproportionally to the hypergammaglobulinemia associated with MAIDS.

IL-4 and IL-10 antagonize IL-12-mediated protection against acute vaccinia virus infection with a limited role of IFN-gamma and nitric oxide synthetase 2

Resistance or susceptibility to most infectious diseases is strongly determined by the balance of type 1 vs type 2 cytokines produced during infection. However, for viruses, this scheme may be applicable only to infections with some cytopathic viruses, where IFN-gamma is considered as mandatory for host defense with little if any participation of type 2 responses. We studied the role of signature Th1 (IL-12, IFN-gamma) and Th2 (IL-4, IL-10) cytokines for immune responses against vaccinia virus (VV). IL-12-/- mice were far more susceptible than IFN-gamma-/- mice, and primary CTL responses against VV were absent in IL-12-/- mice but remained intact in IFN-gamma-/- mice. Both CD4+ and CD8+ T cells from IL-12-/- mice were unimpaired in IFN-gamma production, although CD4+ T cells showed elevated Th2 cytokine responses. Virus replication was impaired in IL-4-/- mice and, even more strikingly, in IL-10-/- mice, which both produced elevated levels of the proinflammatory cytokines IL-1alpha and IL-6. Thus, IL-4 produced by Th2 cells and IL-10 produced by Th2 cells and probably also by macrophages counteract efficient anti-viral host defense. Surprisingly, NO production, which is considered as a major type 1 effector pathway inhibited by type 2 cytokines, appears to play a limited role against VV, because NO sythetase 2-deficient mice did not show increased viral replication. Thus, our results identify a new role for IL-12 in defense beyond the induction of IFN-gamma and show that IL-4 and IL-10 modulate host protective responses to VV.

IL-12 is produced by antigen-presenting cells stimulated with soluble alphabeta TCR and restores impaired T(h)1 responses

Contact sensitivity (CS) is a cutaneous T(h)1 response that is induced by skin painting with reactive hapten. In prior in vivo studies of CS, we showed that recombinant soluble alphabetaTCR (sTCR) acted non-specifically to protect CS-effector T cells from suppression, but no molecular mechanism was determined. In the current study, we employed an in vitro system to investigate the mechanism of how sTCR protect CS-effector T cells from suppression. Immune CS-effector cells and appropriate hapten-conjugated antigen-presenting cells (APC) were incubated together with down-regulatory culture supernatant produced by suppressive spleen cells from mice tolerized i.v. with specific hapten, which produced strong inhibition of IFN-gamma production by the CS-effector cells. Importantly, addition of two different sTCR, of unrelated specificity, reversed this down-regulation and thus restored IFN-gamma production. We found that the APC, and not the CS-effector T cells, were the locus of the sTCR-mediated protection and showed direct binding of sTCR to APC by flow cytometry. Further, addition of anti-IL-12 showed that sTCR protection was due to IL-12 induced by sTCR and released by the APC, and was confirmed by ELISA measurement of IL-12 induced in APC supernatants by sTCR incubation. These results indicated a possible new regulatory loop in which suppression was reversed by IL-12 derived from APC, following direct surface binding of sTCR, and enhanced by IFN-gamma production from the T(h)1 CS-effector cells.

Mice transgenic for a soluble form of murine cytotoxic T lymphocyte antigen 4 are refractory to murine acquired immune deficiency sydrome development

Interactions between B and CD4+ T cells are central to the pathogenesis of retrovirus-induced murine acquired immune deficiency virus (MAIDS). Prompted by previous work showing that treatment with cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) partly inhibited the disease, we studied the course of infection in mice deficient for CD28-B7 interactions (mCTLA4-Hgamma1 transgenic mice). Despite a relative viral load identical to that of non-transgenic mice, the transgenic mice did not develop any of the major MAIDS symptoms (i.e. lymphoproliferation and immune anergy). The mCTLA4-Hgamma1 did not however, completely inhibit B-cell activation as indicated by a slight hypergammaglobulinaemia and microscopic blastic transformation. Absence of MAIDS in transgenic mice was associated with much lower levels of both interleukin-4 and interferon-gamma transcripts following viral infection. These results support the theory that the CD28/B7 costimulatory pathway is a critical determinant to MAIDS development.

The role of endogenous interleukin-12 in resistance to murine cytomegalovirus (MCMV) infection and a novel action for endogenous IL-12 p40

Biologically active interleukin-12 (IL-12), comprising a 40 kDa subunit (p40) covalently linked to a 35 kDa subunit (p35), is produced in response to a range of infectious stimuli. Here, we demonstrate that mice deficient in either IL-12 p40 (p40-/-) or IL-12 p35 (p35-/-) are susceptible to murine cytomegalovirus (MCMV) infection in terms of survival (Balb/c p35-/-) and viral clearance (Balb/c p35-/- and Balb/c p40-/-), and this susceptibility may be correlated to a deficiency in serum interferon-gamma (IFN-gamma) levels. These data support a role for endogenous IL-12 in controlling MCMV infection. The IL-12 p40 subunit is produced in excess of IL-12 p35, and to date the function of the excess endogenous p40 has been assumed to be one of IL-12 antagonism, as demonstrated by experiments with exogenous p40 both in vivo and in vitro. We show that Balb/c p35-/- alone are significantly compromised in survival of a sublethal infection and in clearance of virus from the spleen. These mice produce a very early IFN-gamma spike (8 h after infection) and an aberrant tumor necrosis factor-alpha (TNF-alpha) spike (day 2 after infection). MCMV infection has revealed an altered Balb/c p35-/- phenotype compared with Balb/c p40-/-, and this indicates that endogenous p40 may have an activity independent of and additional to IL-12 antagonism in vivo.

Dose-dependent effects of IL-12 treatment to immune response induced after immunization with a recombinant respiratory syncytial virus (RSV) fusion protein fragment

The amino acid (aa) sequence 190-289 of the RSV fusion (F) glycoprotein expressed in insect cells (bF(190-289)) has been shown to partially protect BALB/c mice and to prime for a Th2 cell response. We evaluated the effects of IL-12 treatment during antigen priming of bF(190-289) on immune response and protective efficacy. Low doses of IL-12 (10 ng) reduced IL-4 and IL-5 secretion (but did not affect IL-10 production) and decreased inflammatory signs whereas high doses of IL-12 had no effects. In addition, IL-12 treatment did not improve resistance to RSV replication. These results suggest that IL-12 treatment attenuates Th2 response and Th2 associated pulmonary inflammatory response in a dose-dependent manner, without improving protective efficacy.

Retrovirally induced switch from production of IL-12 to IL-4 in dendritic cells

Dendritic cells (DC) in HIV-1 infection show a reduced capacity to stimulate primary T cell proliferation. Exposure of bone marrow-derived DC to Rauscher leukemia virus (RLV) provides a mouse model for studying retrovirally induced reduction in stimulatory capacity for T cells. Treatment with IL-12, a cytokine that promotes the development of Th1 cells, has been postulated as a treatment for AIDS and is effective at restoring cell-mediated immunity in mice infected with mouse AIDS virus or with RLV (see Knight, S. C. and Patterson, S., Annu. Rev. Immunol. 1994. 15: 593-615 for references). Here we studied the direct effect of RLV and of IL-12 on bone marrow-derived DC. Normal DC produced IL-12 and IL-10 and stimulated primary allogeneic T cell proliferation. Exposure of DC to RLV caused reduced production of IL-12, production of IL-4 was seen in DC for the first time and T cell stimulation was inhibited. Addition of IL-12 reinstated and enhanced IL-12 synthesis in RLV-treated DC, abrogated production of IL-10 and IL-4 and restored stimulatory activity. Manipulation of cytokine production in DC could be a stratagem that has evolved in the retrovirus to avoid stimulation of cellular responses.

Therapeutic Protective Effects of IL-12 Combined with Soluble IL-4 Receptor Against Established Infections of Herpes Simplex Virus Type 1 in Thermally Injured Mice

The effect of combination therapy between IL-12 and soluble IL-4R (sIL-4R) on the established infection of HSV-1 in thermally injured mice (TI mice) was investigated. All of the TI mice infected with lethal amounts of HSV-1 died when IL-12 was given therapeutically at a dose of 500 U/mouse. However, 80% of these mice treated prophylactically with IL-12 survived compared with 0% survival of the same mice treated with saline. The therapeutic administration of IL-12 to TI mice currently infected with HSV-1 caused an 80% survival of these mice when the treatment was combined with sIL-4R. Although IL-12 did not stimulate IFN-γ production in cultures of splenic T cells from TI mice, IFN-γ was produced by stimulation with IL-12 when the producer cells were prepared from TI mice that had been treated previously with sIL-4R. After stimulation with anti-CD3 mAb, splenic T cells from TI mice with the established infection of HSV-1 produced IL-4 into their culture fluids. However, IL-4 was not produced by splenic T cells that were prepared from the same infected mice treated with IL-12 and sIL-4R in combination. The results obtained herein indicate that the efficacies of the combination therapy against the established infection of HSV-1 may result from the IFN-γ production stimulated by IL-12 in TI mice that are treated with sIL-4R for reducing burn-associated type 2 T cell responses.

Interleukin-12 (IL-12)-driven alloimmune responses in vitro and in vivo: requirement for beta1 subunit of the IL-12 receptor

BACKGROUND

Interleukin-12 (IL-12) mediates its biologic activities via binding high-affinity receptors on T and natural killer cells. Although emphasis has been placed on the requirement for IL-12Rbeta2 in IL-12 bioactivity, the role of IL-12Rbeta1 is less well defined. The current study evaluated the effects of exogenous IL-12 on alloantigen-specific immune responses and determined the requirement for IL-12Rbeta1 in IL-12-mediated alloimmunity.

METHODS

The mouse heterotopic cardiac transplant model was employed to evaluate the effects of IL-12 on alloantigen-specific immune responses in vivo. In addition, IFN-gamma production in mixed lymphocyte cultures (MLC) supplemented with IL-12 was measured to assess the effects of IL-12 on Th1 function in vitro. Mice deficient in IL-12Rbeta1 (IL-12Rbeta1-/-) were used to determine the requirement for this receptor component in IL-12-driven alloimmune responses.

RESULTS

Addition of IL-12 to MLC consisting of wild-type splenocytes enhanced alloantigen-specific proliferative responses and Th1 development. In contrast, IL-12 did not alter these in vitro immune parameters in IL-12Rbeta1-/- MLC. Treatment of wild-type cardiac allograft recipients with IL-12 resulted in high concentrations of serum interferon-gamma (IFN-gamma) and a 10-fold increase in IFN-gamma production by recipient splenocytes after restimulation in vitro. However, this fulminate Th1 response did not accelerate allograft rejection. Importantly, IL-12 had no effect on serum IFN-gamma or in vivo priming of Thl in IL-12Rbeta1-/- recipients. Finally, administration of IL-12 to WT allograft recipients resulted in a bimodal alloantibody response: antibody production was suppressed at high doses of IL-12, and enhanced at lower doses.

CONCLUSIONS

IL-12 markedly enhances alloantigen-specific immune function; however, these exaggerated Th1-driven responses do not culminate in accelerated allograft rejection. Further, these data indicate that IL-12Rbeta1 is essential for the enhancement of both in vitro and in vivo alloimmune responses by exogenous IL-12.

IL-12 Delivery from Recombinant Vaccinia Virus Attenuates the Vector and Enhances the Cellular Immune Response Against HIV-1 Env in a Dose-Dependent Manner

To develop vaccination strategies against HIV-1 infection aimed to specifically enhance the cell-mediated immunity (CMI), we have engineered vaccinia virus (VV) recombinants expressing HIV-1 Env (rVVenv) and murine IL-12 (rVVlucIL-12) genes or coexpressing both genes (rVVenvIL-12). In mice inoculated with rVVlucIL-12 there is a rapid clearance of the virus, and this correlates with the induction of high levels of IL-12 and IFN-γ in serum and spleen early after infection. Enzyme-linked immunospot analysis of mice inoculated with rVVlucIL-12, revealed a nearly 2-fold increase in the number of specific anti-VV CD8+ T cells compared with that in mice given control rVV, and the serum Ab response was biased in favor of a Th1 response. An enhancement of about 2-fold in the number of anti-gp160 IFN-γ-secreting CD8+ T cells was observed in mice inoculated with rVVenvIL-12, when a dose of 1 × 107 PFU/mouse was used, but this enhancement was not observed when mice were given 5 × 107 PFU. This variation with virus dosage was confirmed in mice immunized simultaneously with different multiplicities of rVV expressing singly the env or IL-12 genes. The highest specific CMI was obtained in mice coadministered a low dose (2 × 104 PFU) of rVVlucIL-12 and 1 × 107 PFU of rVVenv. Our findings provide evidence for specific enhancement of the CMI to HIV-1 Env by the differential expression of IL-12 and env genes delivered from VV recombinants. This approach can be of wide vaccination interest as a means to improve immune responses to other Ags.

Enhanced protection against viral infection by co-administration of plasmid DNA coding for viral antigen and cytokines in mice

BACKGROUND

DNA vaccines have been shown to induce protective immunity against viral infections in different animal models. We have recently demonstrated that DNA vaccine induced protective immunity against influenza A virus and La Crosse virus (LACV) is primarily mediated by humoral immune response.

OBJECTIVE

The goal of this study was to investigate whether administration of DNA coding for cytokines such as interleukin 12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF) could increase the protective immune response induced by vaccination with DNA coding for viral antigens.

STUDY DESIGN

For the influenza A virus or LACV model, C57BL/6 or interferon-alpha/beta receptor (IFNAR-1)-deficient mice, respectively, were vaccinated once or twice with 100 micrograms of DNA encoding viral antigens. At the same time plasmid DNAs (100 micrograms) coding either for mouse GM-CSF or mouse IL-12 were administered. The mice were subsequently challenged with a lethal dose of influenza A virus or LACV and monitored for clinical symptoms (weight loss) and survival.

RESULTS

To achieve a high degree of protection (70% survival) two injections of DNA encoding the influenza A virus surface protein hemagglutinin (HA) were required. Intriguingly, administration of DNA coding for IL-12 alone also led to a pronounced protective effect against virus challenge. Co-administration of DNAs encoding IL-12 and HA significantly increased the protective immunity against influenza A virus, while IL-12 expression did not improve protection upon vaccination with DNA coding for the internal nucleocapsid protein N of LACV. Co-injection of DNA coding for mouse GM-CSF and HA also showed an adjuvant effect.

CONCLUSIONS

The data clearly indicate that co-administration of DNA encoding cytokines such as IL-12 and GM-CSF with DNA coding for viral antigens has adjuvant effects on the protective immune response against different viral pathogens.

Atopy, anergic status, and cytokine expression in HIV-infected subjects

BACKGROUND

In HIV infection T-cell dysfunction resulting in anergy and hypersensitivity reactions precedes T-cell depletion. A shift in the cytokine profile from a type 1 to a type 2 response has been postulated.

OBJECTIVE

We sought to examine the cytokine expression patterns in HIV infection and the relationship to allergy, stage of HIV disease, and other laboratory parameters.

METHODS

A cross-sectional analysis of IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p35, IL-13, and IFN-gamma mRNA expression in PBMCs by noncompetitive dot-blot PCR was performed on blood obtained from 18 HIV-infected subjects. Delayed-type hypersensitivity multitests to detect anergy, skin prick testing and in vitro assay for specific IgE antibodies, assay for total IgE, and enumeration of eosinophils, CD4(+), and CD8(+) T cells were also performed on all subjects.

RESULTS

We found evidence of a decline in type 1 cytokines (IL-2, IL-12p35, and IFN-gamma) associated with AIDS, CD4(+) T cells less than 200/microL, anergy, and atopy, although this only reached statistical significance in anergy. There was no associated significant alteration in type 2 cytokines.

CONCLUSIONS

This is the first report of an association between low constitutive in vivo expression of IL-12 mRNA and anergy, which supports earlier data from in vitro stimulation studies. The presence of atopy was associated with a more global reduction in cytokine expression. Because the decline in type 1 cytokines was not accompanied by a similar decline in type 2 cytokines, this does suggest a shift in the type 1/type 2 balance.

A phase I/II study of recombinant human interleukin-12 in patients with chronic hepatitis C

Interleukin-12 (IL-12) plays a central role in mounting an effective cellular immune response directed towards elimination of intracellular pathogens. The present open-label, multicenter, dose-escalation phase I/II study was designed to assess tolerability, pharmacokinetics, pharmacodynamics, and efficacy of subcutaneously administered recombinant human interleukin-12 (rHuIL-12) in the treatment of chronic hepatitis C. Sixty patients (42 men, 18 women, aged 24-60) were treated with 0.03 microgram/kg (n = 16), 0.1 microgram/kg (n = 14), 0.25 microgram/kg (n = 15), or 0.5 microgram/kg rHuIL-12 (n = 15) for 10 consecutive weeks. rHuIL-12 was generally well tolerated, with 2 patients (3.3%) being withdrawn from treatment for adverse events. Treatment was associated with temporary decreases in neutrophils and lymphocyte counts and with elevations in serum transaminases and bilirubin. Serum IL-12 levels observed were higher at 0.5 microgram/kg compared with 0.25 microgram/kg doses, suggesting a dose-related increase in systemic exposure of IL-12. Measurable levels of interferon gamma (IFN-gamma) were also observed at the highest dose of 0.5 microgram/kg. At the end of treatment hepatitis C virus (HCV) RNA was detectable in all patients. A more than 50% decrease in pretreatment HCV RNA levels was observed in 3 of 16 patients of the 0.03-microgram/kg dose group, in 3 of 14 of the 0.10-microgram/kg dose group, in 6 of 15 of the 0.25-microgram/kg dose group, and in 8 of 15 patients of the 0.5-microgram/kg dose group. Although in several cases serum alanine transaminase (ALT) levels decreased either during or after treatment, ALT normalization was observed in only 4 patients at the end of treatment and in 5 patients at the end of follow-up. Significant anti-rHuIL-12 antibody titers were not detectable in any patient. In conclusion, antiviral activity of rHuIL-12 in patients with chronic hepatitis C does not appear advantageous in comparison with other currently available treatments.

Delayed progression of murine AIDS in C57BL/6 mice pre-immunized with a highly antigenic 10-mer peptide encoded by the murine AIDS defective virus gag p12 gene

C57BL/6 (B6) mice were immunized with a highly antigenic 10-mer peptide (P12-10), which is encoded by the murine AIDS (MAIDS) defective virus gag p12 gene, emulsified in incomplete Freund's adjuvant (ICFA). One week later, the mice were inoculated with the MAIDS virus to see if the immunization affects progression of MAIDS. It was demonstrated that the immunization significantly delayed progression of MAIDS, although it failed to induce appreciable cytotoxic T lymphocyte (CTL) responses against the P12-10 antigen. In contrast, immunization of B6 mice with the P12-10 coupled with liposome induced substantial CTL responses but failed to protect the mice against MAIDS development. This segregation between CTL activity and in vivo protection efficacy might be worth considering when we exploit vaccines for augmenting cellular immunity mediated by CD8+ T cells.

IL-12 and viral infections

Interleukin-12 activates natural killer cells and promotes the differentiation of Th1 CD4+ cells; it is a critical factor in viral immunity. IL-12 is secreted by antigen presenting cells including dendritic cells, macrophages and astrocytes, both in tissues and in secondary lymphoid organs. Experimental studies have shown that administration of the cytokine rapidly activates both innate and specific immune responses; this results in enhanced host cellular responses and generally, promotes clearance of virus and host recovery from infection. The observations of many laboratories, studying viral immunity to both RNA and DNA based pathogens, are summarized.

Prevention of murine AIDS development by (R)-9-(2-phosphonylmethoxypropyl)adenine

LP-BM5 murine leukemia virus (MuLV) infection causes severe immunodeficiency termed murine AIDS (MAIDS). The acyclic nucleoside phosphonates, (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) were examined, in comparison with zidovudine (AZT), for their inhibitory effect on the development of MAIDS. Although no significant difference in inhibition of LP-BM5 MuLV replication was identified between PMPA and PMEA in cell cultures, PMPA was obviously less cytotoxic to the host lymphocytes. None of the mice treated in vivo with 5 or 25 mg/kg of PMPA or 25 mg/kg of PMEA developed MAIDS at 5 weeks after viral infection. However at 9 weeks, none of the 25 mg/kg PMPA-treated mice progressed to MAIDS, except for one that developed mild MAIDS, whereas PMEA, even at 100 mg/kg, could not prevent disease progression. MAIDS-associated activation of lymphocytes and viral replication were drastically inhibited by PMPA treatment. These results indicate that PMPA is a highly effective antiretroviral agent in vivo.

Role of interleukin-12 in primary influenza virus infection

The effect of endogenous interleukin-12 (IL-12) on the influenza virus immune response in BALB/c mice was evaluated. Following primary influenza virus infection, IL-12 mRNA and protein are detected in the lung, with live virus being required for cytokine induction. Endogenous IL-12 contributes to early NK cell-dependent gamma interferon (IFN-gamma) production (days 3 and 5) but not late T-cell-dependent IFN-gamma secretion (day 7). IL-12 contributes to the inhibition of early virus replication but is not required for virus clearance. IL-12 also modestly contributes to the activation of cytotoxic T lymphocytes. Thus, in this model of experimental influenza virus infection, endogenous IL-12 contributes primarily to the early development and activation of the innate immune response.

The interleukin-12/interleukin-12-receptor system: role in normal and pathologic immune responses

Interleukin-12 (IL-12) is a heterodimeric cytokine that plays a central role in promoting type 1 T helper cell (Th1) responses and, hence, cell-mediated immunity. Its activities are mediated through a high-affinity receptor composed of two subunits, designated beta 1 and beta 2. Of these two subunits, beta 2 is more restricted in its distribution, and regulation of its expression is likely a central mechanism by which IL-12 responsiveness is controlled. Studies with neutralizing anti-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 pathogens. However, IL-12 appears also to play a central role in the genesis of some forms of immunopathology. Inhibition of IL-12 synthesis or activity may be beneficial in diseases associated with pathologic Th1 responses, such as multiple sclerosis or Crohn's disease. On the other hand, administration of recombinant IL-12 may have utility in the treatment of diseases associated with pathologic Th2 responses such as allergic disorders and asthma.