The role of tumor necrosis factor in viral disease

Differential and sequential immunomodulatory role of neutrophils and Ly6Chi inflammatory monocytes during antiviral antibody therapy

Antiviral monoclonal antibodies (mAbs) can generate protective immunity through Fc-FcγRs interactions. We previously showed a role for immune complexes (ICs) in the enhancement of antiviral T-cell responses through FcγR-mediated activation of dendritic cells (DCs). Here we addressed how mAb therapy in retrovirus-infected mice affects the activation of neutrophils and inflammatory monocytes, two FcγR-expressing innate effector cells rapidly recruited to sites of infection. We found that both cell-types activated in vitro by viral ICs secreted chemokines able to recruit monocytes and neutrophils themselves. Moreover, inflammatory cytokines potentiated chemokines and cytokines release by IC-activated cells and induced FcγRIV upregulation. Similarly, infection and mAb-treatment upregulated FcγRIV on neutrophils and inflammatory monocytes and enhanced their cytokines/chemokines secretion. Notably, upon antibody therapy neutrophils and inflammatory monocytes displayed distinct functional activation states and sequentially modulated the antiviral immune response by secreting Th1-type polarizing cytokines and chemokines, which occurred in a FcγRIV-dependent manner. Consistently, FcγRIV- blocking in mAb-treated, infected mice led to reduced immune protection. Our work provides new findings on the immunomodulatory role of neutrophils and monocytes in the enhancement of immune responses upon antiviral mAb therapy.

Association of LTA gene haploblock with periodontal disease in Italian adults

BACKGROUND

Periodontitis is a common oral disease caused by host inflammatory response towards bacteria biofilm. The chronic activation of immune response leads to destruction of teeth supporting tissue, bone loss and tooth detachment. Different factors could be involved in the development and severity of the disease; among them the host genetic background should be considered.

OBJECTIVES

In our study, we analysed haploblocks in a genomic region within major histocompatibility complex (MHC) locus aimed at disclosing a possible correlation with the risk of periodontal disease in 602 adult subjects from North-East Italy.

RESULTS

The CTTAC haploblock (formed by LTA-rs2857709, LTA-rs2844484, LTA- rs2229094, LTA-rs2229092 and LTA-rs1041981 polymorphisms) correlated with protection towards periodontitis condition, after regression analysis including age and smoking status as covariates (P-value = 0.015).

CONCLUSION

Our results suggest that a haplotype within LTA gene (encoding for lymphotoxin alpha) is involved in the susceptibility towards chronic periodontitis.

Insulin Resistance Predicts Virological Response to Interferon-α in Chronic Hepatitis B Patients

GOALS

To elucidate impact of insulin resistance (IR) on the response to interferon-α (IFN-α) therapy in chronic hepatitis B (CHB) patients.

BACKGROUND

Metabolic factors influencing the virological response of CHB patients on IFN-α treatment are still unexplored.

STUDY

Eighty CHB patients were treated with IFN-α for 48 weeks. The IR was evaluated by homeostasis model assessment of IR (HOMA-IR) before treatment. Viral load and biochemical parameters were measured at 12, 24, and 48 weeks after starting treatment, and then 24 weeks after the end of treatment. IFN-γ and tumor necrosis factor-α were tested at baseline and 12 weeks of treatment.

RESULTS

Pretreatment HOMA-IR proved to be the only independent predictor of primary nonresponse, as well as the pretreatment HOMA-IR, viral load and primary nonresponse were independently associated with virological response at 24, 48 weeks of treatment and at the follow-up endpoint. The significant higher virological relapse rate in patients with IR was observed in patients with virological response at 48 weeks of treatment. The mean HOMA-IR was significantly lower in virological responders than in virological nonresponders. The secretion of IFN-γ and tumor necrosis factor-α was not induced in patients with IR at 12 weeks after IFN-α treatment.

CONCLUSIONS

Our data suggest that IR is strongly associated with virological response, thus reflecting the important role played by metabolic factors in the viral kinetics during IFN-α treatment. These findings suggested clinical application of pretreatment HOMA-IR could enable treatment outcome to be predicted and treatment regimens to be determined.

In vitro immunomodulatory activity of oxymatrine on Toll-like receptor 9 signal pathway in chronic hepatitis B

Oxymatrine, extracted from the herb Sophora alopecuraides L., was investigated to determine its anti-HBV immunomodulatory mechanism in vitro. Human peripheral lymphocytes were isolated from heparinized whole blood from 48 chronic hepatitis B (CHB) patients. The lymphocytes from each patient were divided into two groups according to pretreatment or no pretreatment with Oxymatrine in vitro. We examined the changes of expression and function of the toll-like receptor 9 (TLR9) signal transduction pathway in the peripheral lymphocytes with different treatment methods and investigated the synergism of Oxymatrine and the TLR9 ligand on antiviral cytokine secretions in vitro. The data showed Oxymatrine could induce antiviral cytokine secretions directly from the peripheral lymphocytes. For the TLR9 signal pathway, Oxymatrine not only augmented the expressions of TLR9 signal transduction molecules, but also activated the TLR9 signal function. This study has clearly demonstrated that TLR9 ligand could stimulate peripheral lymphocytes that have been pretreated with Oxymatrine. Furthermore, the quantity of antiviral cytokines secreted by the pretreated lymphocytes was greater than that of those without pretreatment. The interaction between the Oxymatrine and the TLR9 ligand appears to be synergistic. This study suggests Oxymatrine could be a strong immunomodulator, influence TLR9 signaling transduction, and synergistically improve the immune efficacy of the TLR9 ligand against CHB.

In vitro immunomodulatory activity of interferon alpha on toll-like receptor 9 signaling pathway in chronic hepatitis B

Interferon alpha (IFN-α) is registered for chronic hepatitis B (CHB) treatment. However, the antiviral mechanism of IFN-α and the biological function of many IFN-α responsive genes have not been fully elucidated. We investigated to determine the regulative effect of IFN-α on toll-like receptor (TLR) 9 signaling in peripheral blood mononuclear cells (PBMCs) from CHB patients in vitro. We examined the changes of expression and function of TLR9 signaling pathway in the PBMCs with different treatment methods and investigated the synergism of IFN-α and TLR9 ligand on antiviral cytokine secretions in vitro. The data showed that, for the TLR9 signaling pathway, IFN-α not only augmented the expressions of TLR9 signal transduction molecules but also activated the TLR9 signal function. This study has clearly demonstrated that the TLR9 ligand could stimulate PBMCs that have been pretreated with IFN-α. Furthermore, the quantity of antiviral cytokines secreted by the pretreated PBMCs was greater than those without pretreatment. The interaction between IFN-α and TLR9 ligand appears to be synergistic. Data revealed IFN-α could influence TLR9 signaling transduction and synergistically improve the immune efficacy of TLR9 ligand against CHB. The present study suggests a potential novel mechanism for the antiviral activity against hepatitis B virus and a new individualized antiviral strategy.

Nodavirus increases the expression of Mx and inflammatory cytokines in fish brain

Nodavirus has become a serious pathogen for a wide range of cultured marine fish species. In the present work, the expression of genes related to immune and inflammatory responses of sea bream (Sparus aurata L.), considered as non susceptible species, was studied both in vitro and in vivo. No replication of the virus was observed in head kidney macrophages and blood leukocytes. Moreover, the enhancement of expression of several immune genes (tumor necrosis factor alpha (TNFalpha), interleukin-1-beta (IL-1beta), interferon-induced Mx protein) was not detected in both head kidney macrophages and blood leucocytes in response to an in vitro infection with nodavirus. However, in vivo, nodavirus was detected 1 day post-infection (p.i.) by a reverse transcription-polymerase chain reaction (RT-PCR) in blood, liver, head kidney and brain of experimentally infected sea bream, while its presence clearly decreased in blood after 3 days p.i. Also, a transitory increment of the expression of TNFalpha and IL-1beta was detected in the brain of intramuscular (i.m.) infected sea bream 3 days p.i. In head kidney, the over expression of TNFalpha was only observed 1 day p.i. The expression of Mx, an interferon induced gene, was increased in brain and head kidney of infected sea bream, reaching values of 1300-fold compared to controls in brain three days post-infection. For comparative purposes, we analyzed the expression of the same genes on a susceptible species, such as sea bass (Dicentrarchus labrax) and, although the same pattern of expression was observed both in brain and kidney, the magnitude was different mainly in the case of brain, the key organ of the infection, where higher expression of TNFalpha and lower expression of Mx compared with control was observed.

Evidence of NK cell dysfunction in SIV-infected rhesus monkeys: impairment of cytokine secretion and NKG2C/C2 expression

Defects in the adaptive immune response have been extensively characterized in human immunodeficiency virus type-1 (HIV-1)-infected individuals; however, much less is known about the function of natural killer (NK) cells during the course of HIV-1 infection. In the present study, we demonstrate that the NK cells from simian immunodeficiency virus (SIV)-infected rhesus monkeys are significantly impaired in their ability to secrete IFN-gamma, TNF-alpha, and IL-2, while NK cell function in SIV-infected long-term non-progressor monkeys is similar to that of normal monkeys. These findings suggest that abnormal NK cell activity may contribute to the global immune dysfunction observed in HIV-1-infected individuals. NK cell function is modulated by several families of cell surface receptors, including the CD94/NKG2 family. We evaluated the messenger RNA levels of these inhibitory and activating NKG2 molecules in SIV-infected rhesus monkeys. These experiments demonstrate that the activating molecules NKG2C and NKG2C2 are significantly down-regulated in peripheral blood mononuclear cells of SIV-infected rhesus monkeys, suggesting that the dysregulation of these molecules may contribute to the abnormal NK cell function observed in the setting of infection.

Effect of varicella zoster virus infection on bone marrow function

BACKGROUND

Most viral infections are known to exert adverse effects on bone marrow function. However, certain viruses have recently been found to be therapeutically beneficial in the treatment of some malignant disorders.

METHODS AND MATERIALS

A retrospective study was conducted at the Armed Forces Hospital, Riyadh, Saudi Arabia. The changes in the hematological parameters following varicella-zoster virus (VZV) infection in patients with a variety of hematological disorders were compared with those in a control group having the same spectrum of disorders and treated in the same unit over the same period of time but never had VZV infection. Both groups of patients received the same treatment protocols for their primary hematological disorders. Definitive treatment (DT) such as chemotherapy alone, anti-thymocyte globulin or bone marrow transplant was also employed in the management of patients belonging to both groups.

RESULTS

White blood cell counts, platelet counts and hemoglobin concentrations in the study group started to increase 40 d after chickenpox or herpes zoster infection and these increases lasted for periods as long as 1050 d. The changes in platelet counts were more pronounced than those in other hematological parameters. There was a significant difference (P < 0.0001) between the two groups of patients in the values of platelet counts achieved between 280 and 1050 d after DT (mean platelet count: 262 x 10(9)/L in the study group vs. 180 x 10(9)/L in the control group, median: 288.17 x 10(9)/L in the study group vs. 180 x 10(9)/L in the control group, range: 102 to 415 x 10(9)/L in the study group vs. 26 to 365 x 10(9)/L in the control group of patients). Compared to the control group, the study group of patients achieved their maximum blood counts much earlier after DT. The maximum leucocytic count was achieved at a mean duration of 269.21 d in the study group and 349.61 d in the control group. The maximum hemoglobin level was achieved at a mean duration of 319.5 d in the study group and 402.6 d in the control group. The maximum platelet count was achieved at a mean duration of 271.4 d in the study group and 318.9 d in the control group of patients.

CONCLUSION

VZV may behave differently from other members of the herpes group of viruses e.g. human cytomegalovirus and Epstein-Barr virus. Our observations suggest that VZV infection causes stimulation of bone marrow activity.

The regulation of rhinovirus infection in vitro by IL-8, HuIFN-alpha, and TNF-alpha

The influence of three important cytokines (IL-8, TNF-alpha, and HuIFN-alpha) on ongoing rhinovirus infections has been examined in vitro, individually or as combinations. TNF-alpha was able to transform traces of HRV infections into full-blown infections. Furthermore, TNF-alpha was able to down-regulate the antiviral action of HuIFN-alpha completely, even at levels of just a few pg/ml. This suggests that the induction of TNF-alpha by HRV may be part of the virus's strategy to minimize the interferon response which is part of the host's immune defence system. However, troxerutin (a flavonoid) was able to neutralize the downregulatory action of TNF-alpha on the HuIFN-alpha system at low levels and re-establish the antiviral activity ascribed to IFN-alpha. IL-8 exerted a minor influence on the interferon system, and had no influence on rhinovirus infections. The in vitro findings are supported, in part, by recent in vivo findings in a common cold pilot study.

Poliovirus protein 3A inhibits tumor necrosis factor (TNF)-induced apoptosis by eliminating the TNF receptor from the cell surface

Viral infections often trigger host defensive reactions by activating intrinsic (intracellular) and extrinsic (receptor-mediated) apoptotic pathways. Poliovirus is known to encode an antiapoptotic function(s) suppressing the intrinsic pathway. Here, the effect of poliovirus nonstructural proteins on cell sensitivity to tumor necrosis factor (TNF)-induced (i.e., receptor-mediated) apoptosis was studied. This sensitivity is dramatically enhanced by the viral proteinase 2A, due, most likely, to inhibition of cellular translation. On the other hand, cells expressing poliovirus noncapsid proteins 3A and 2B exhibit strong TNF resistance. Expression of 3A neutralizes the proapoptotic activity of 2A and results in a specific suppression of TNF signaling, including the lack of activation of NF-kappaB, due to elimination of the TNF receptor from the cell surface. In agreement with this, poliovirus infection results in a dramatic decrease in TNF receptor abundance on the surfaces of infected cells as early as 4 h postinfection. Poliovirus proteins that confer resistance to TNF interfere with endoplasmic reticulum-Golgi protein trafficking, and their effect on TNF signaling can be imitated by brefeldin A, suggesting that the mechanism of poliovirus-mediated resistance to TNF is a result of aberrant TNF receptor trafficking.

Overexpression of interleukin-6 aggravates viral myocarditis: impaired increase in tumor necrosis factor-alpha

The process of inflammation and immune response is regulated by proinflammatory cytokines. Interleukin-6 (IL-6), one of the proinflammatory cytokines, plays a potentially critical role in viral-induced myocarditis. Our previous work demonstrates that exogenous IL-6 administration, given at the time of encephalomyocarditis virus (EMCV) inoculation in C3H/HeJ mice, has a protective effect on myocardium and improves survival rates. In the present study, we examined whether overexpression of IL-6 modified viral myocarditis. On day 3 and 10 after inoculation with EMCV, the ratio of heart weight to body weight and myocardial injury were significantly increased in IL-6 transgenic mice (IL-6TG). On day 3, a reduction of viral clearance was shown by the presence of elevated viral titers and viral replication in the heart of IL-6TG. The concentrations of serum tumor necrosis factor- alpha (TNF alpha) were dramatically increased in wild-type mice on day 1, in contrast, this change was not observed in IL-6TG. Treatment with recombinant human TNF (2 microg) significantly improved viral clearance in the IL-6TG hearts. Thus, overexpression of IL-6 promotes myocardial injury by interrupting both the cytokine network and viral clearance. These experiments suggest the possibility that IL-6 is one of the factors that accelerates tissue damage, including myocardial injury, in the viral myocarditis.

Gene delivery from the E3 region of replicating human adenovirus: evaluation of the ADP region

Genetically modified replication-selective human adenoviruses are currently undergoing testing in the clinical setting as anticancer agents. Coupling the lytic function of these viruses with virus-mediated transgene delivery represents a powerful extension of this treatment. We have designed a unique system for gene delivery from the replicating virus. It takes advantage of the endogenous gene expression control sequences (promoter, splicing, polyadenylation signals) to efficiently and predictably deliver transgenes from the non-essential E3 transcription unit while still maintaining the expression of the remaining E3 genes in the multi-gene transcription unit. In this article, we engineered restriction enzyme sites into the virus genome selectively to delete the ADP gene and replace it with the therapeutic transgenes CD and TNFalpha. We demonstrate that: (1) transgene expression from this region mirrors the substituted ADP gene; (2) the loss of ADP in these viruses results in infected cells with extended viability and protein synthesis when compared with a wild-type Ad5 infected cell; and (3) expression of surrounding E3 genes can be maintained in such a system. The potential advantages of delivering transgenes from the ADP region of the replicating adenovirus are discussed.

Innate antiviral defenses in body fluids and tissues

Innate, non-specific, resistance mechanisms are important barriers to pathogens, particularly delaying virus multiplication at the onset of infections. These innate defense mechanisms include a series of mechanical barriers, pre-existing inhibitory molecules, and cellular responses with antimicrobial activity. The antiviral activities of these innate inhibitors reside in a variety of partly characterized substances. This review presents the innate antiviral inhibitors in cell cultures, urine, serum, the gastrointestinal tract, the nervous system, tissues of crustaceans, and saliva. Medical adaptation of the innate antiviral defense mechanisms may be useful for prevention and treatment of viral infections.

Innate defences against viraemia

Human blood plasma has been reported to possess nonspecific antiviral activity. This activity is due to several preexisting naturally occurring molecules that are either active against individual members or a family of viruses. These molecules, however, have not been adequately studied to reveal their molecular structures and mechanisms of action presumably because of their low and nonspecific antiviral action. Therefore, their possible role against viraemia remains unknown. Recently, two naturally occurring nonspecific broad-spectrum antiviral agents, University of Texas Inhibitor beta (UTIbeta) glycoprotein and high density lipoprotein, have been described in human serum. They are active against DNA and RNA viruses and one of them, UTIbeta, possesses significant antiviral activity of 40 units/mL. Since preexisting antiviral molecules in serum appear to be the only defence mechanisms available at the onset of viral infection they may have protective significance against viraemia. In view of this potential, we have undertaken to review the properties of these innate viral inhibitory molecules.

TNF alpha and the TNF receptor superfamily: structure-function relationship(s)

Tumour Necrosis Factor alpha (TNF alpha), is an inflammatory cytokine produced by macrophages/monocytes during acute inflammation and is responsible for a diverse range of signalling events within cells, leading to necrosis or apoptosis. The protein is also important for resistance to infection and cancers. TNF alpha exerts many of its effects by binding, as a trimer, to either a 55 kDa cell membrane receptor termed TNFR-1 or a 75 kDa cell membrane receptor termed TNFR-2. Both these receptors belong to the so-called TNF receptor superfamily. The superfamily includes FAS, CD40, CD27, and RANK. The defining trait of these receptors is an extra cellular domain comprised of two to six repeats of cysteine rich motifs. Additionally, a number of structurally related "decoy receptors" exist that act to sequester TNF molecules, thereby rescuing cells from apoptosis. The crystal structures of TNF alpha, TNF beta, the extracellular domain of TNFR-1 (denoted sTNFR-1), and the TNF beta sTNFR-1 complex have been defined by crystallography. This article will review the structure/function relationships of the TNF alpha and the TNF receptor superfamily. It will also discuss insights as to how structural features play a role in the pleiotropic effects of TNF alpha.

Functional effects of lymphotoxin on crushed peripheral nerve

The effect of lymphotoxin (LT) on the functional recovery of crushed peripheral nerves was studied. Using a specially designed compression device, a 5 mm segment of the right sciatic nerve of rats was subjected to a 100 g crush load with a 2 hr duration. The rats in the experimental and control groups received two doses of LT (20 micrograms/kg each) or the same volume of saline, respectively, administered intraperitoneously 24 hr and 1 hr before the procedure. Walking track tests and histologic examinations were performed at intervals up to 56 days after the crush. Motor functional recovery in the LT pretreated group started at day 7 while the crushed limb in the control group remained totally dysfunctional. The sciatic functional index improved faster in the LT group than in the control group during the second week after the crush and reached a significant difference (P < 0.05) at day 18. Subsequently, both groups had a similar evolution. Histologic results paralleled the functional findings. In conclusion, LT can promote motor functional recovery of crushed rat peripheral nerve in the early stage of regeneration.

Effect of hepatitis B virus on tumour necrosis factor (TNF alpha) gene expression in human THP-1 monocytic and Namalwa B-cell lines

In response to viruses, monocytes and B cells produce TNF alpha. Therefore, we investigated TNF alpha gene expression and protein secretion in a human monocytic cell line, THP-1, and a Burkitt's lymphoma B-cell line, Namalwa, in response to hepatitis B virus (HBV). Stimulation by phorbol myristate acetate (PMA) (100 ng/ml for 48 h) induced TNF alpha secretion in THP-1 and Namalwa cells (100 to 300 pg/ml). In THP cells, the optimum response (> 2000 pg/ml) was obtained in the presence of a second mitogenic signal such as lipopolysaccharide (LPS) (10 microg/ml for 24 h). In our activation conditions, Northern blot analysis revealed a marked accumulation of TNF alpha mRNA species at 1.7 kb in both cell lines. When PMA- or PMA+LPS-stimulated THP-1 cells were exposed to HBV, TNF alpha protein and mRNA significantly decreased (> 50%). In contrast, HBV exposure of PMA-activated Namalwa cells resulted in strongly increased TNF alpha protein secretion (1 ng/ml). In this case, HBV induced TNF alpha mRNA accumulation that consisted of two types: a regular 1.7 kb and two novel high molecular weight (HMW) species at 3.7 and 4.3 kb. Exposure of stimulated THP-1 and Namalwa cells to HBV resulted in HBs and pre-S1 antigen production in the supernatants. In addition, HMW HBV DNA forms were detected in both cell lines, but with distinct HindIII restriction patterns. These findings indicate that TNF alpha gene expression may be differently regulated by HBV in activated human macrophages and B cells, and thus TNF alpha may be involved in the pathogenesis of HBV.

The role of cytokines in the acquired immunodeficiency syndrome

HIV replication in vitro is regulated by many factors, including various exogeneous stimuli and proteins encoded by either virus or cellular genomes. During the asymptomatic period, cells latently or chronically infected with HIV gradually express virus, leading to immunosuppression and opportunistic infection. These conditions would result in the increased secretion of cytokines, especially TNF, from infected and uninfected cells, which can induce HIV and killing of infected cells. A vicious circle is then set in motion in which heterologous microbial infections directly or indirectly activate HIV and the production of cytokines, thereby accelerating lymphocyte depletion and immunodeficiency. AIDS is a disorder of the immune network caused by a unique retrovirus HIV. However, if the whole story described above is true, this disease can also be termed a "cytokine disease". Immunity resembles a "double-edged sword", with aspects not only protective, but also deleterious to the host. Therefore, it is essential to more extensively investigate the mechanism of cytokine regulation of HIV expression in vivo, not only to understand the complex pathophysiology of AIDS, but also to design a therapeutic strategy to halt this deadly disease.