Toll-like receptor 3 blockade in rhinovirus-induced experimental asthma exacerbations: A randomized controlled study.

BACKGROUND: Human rhinoviruses (HRVs) commonly precipitate asthma exacerbations. Toll-like receptor 3, an innate pattern recognition receptor, is triggered by HRV, driving inflammation that can worsen asthma. OBJECTIVE: We sought to evaluate an inhibitory mAb to Toll-like receptor 3, CNTO3157, on experimental HRV-16 inoculation in healthy subjects and asthmatic patients. METHODS: In this double-blind, multicenter, randomized, parallel-group study in North America and Europe, healthy subjects and patients with mild-to-moderate stable asthma received single or multiple doses of CNTO3157 or placebo, respectively, and were then inoculated with HRV-16 within 72 hours. All subjects were monitored for respiratory symptoms, lung function, and nasal viral load. The primary end point was maximal decrease in FEV1 during 10 days after inoculation. RESULTS: In asthmatic patients (n = 63) CNTO3157 provided no protection against FEV1 decrease (least squares mean: CNTO3157 [n = 30] = -7.08% [SE, 8.15%]; placebo [n = 25] = -5.98% [SE, 8.56%]) or symptoms after inoculation. In healthy subjects (n = 12) CNTO3157 versus placebo significantly attenuated upper (P = .03) and lower (P = .02) airway symptom scores, with area-under-the-curve increases of 9.1 (15.1) versus 34.9 (17.6) and 13.0 (18.4) versus 50.4 (25.9) for the CNTO3157 (n = 8) and placebo (n = 4) groups, respectively, after inoculation. All of the severe and 4 of the nonserious asthma exacerbations occurred while receiving CNTO3157. CONCLUSION: In summary, CNTO3157 was ineffective in attenuating the effect of HRV-16 challenge on lung function, asthma control, and symptoms in asthmatic patients but suppressed cold symptoms in healthy subjects. Other approaches, including blockade of multiple pathways or antiviral agents, need to be sought for this high unmet medical need.

Utility of animal and in vivo experimental infection of humans with rhinoviruses in the development of therapeutic agents for viral exacerbations of asthma and chronic obstructive pulmonary disease.

There is an association with acute viral infection of the respiratory tract and exacerbations of asthma and chronic obstructive pulmonary disease (COPD). Although these exacerbations are associated with several types of viruses, human rhinoviruses (HRVs) are associated with the vast majority of disease exacerbations. Due to the lack of an animal species that is naturally permissive for HRVs to use as a facile model system, and the limitations associated with animal models of asthma and COPD, studies of controlled experimental infection of humans with HRVs have been used and conducted safely for decades. This review discusses how these experimental infection studies with HRVs have provided a means of understanding the pathophysiology underlying virus-induced exacerbations of asthma and COPD with the goal of developing agents for their prevention and treatment.

Generation of bleomycin-induced lung fibrosis is independent of IL-16.

Given that CD4+ cells are found in the lungs of patients with fibrotic lung diseases such as idiopathic pulmonary fibrosis (IPF) we hypothesized that IL-16, a potent chemoattractant for CD4+ cells, may be involved in the pathogenesis of this disease. We found that baseline IL-16 gene expression is greater in fibroblasts isolated from IPF patients compared to non-fibrotic fibroblasts. Furthermore, IL-16 gene expression increased in IPF fibroblasts following stimulation with either of the pro-fibrotic growth factors TGFb1 or PDGF. In contrast, PDGF had no effect on IL-16 gene expression in non-fibrotic lung fibroblasts, whereas TGFb1 down-regulated IL-16 gene expression in non-fibrotic fibroblasts. To gain a better understanding of an association of IL-16 with fibrosis, we used the bleomycin-induced mouse model of fibrosis to examine IL-16 gene expression. Our current study demonstrates that IL-16, and its activator caspase 3, are highly expressed at the mRNA level in the lungs of mice prior to the deposition of collagen following intratracheal bleomycin administration. We then sought to determine the role of IL-16 in the generation of fibrosis in the mouse by using IL-16KO mice. There were no differences observed between IL-16WT and IL-16KO mice (cellular infiltrate, collagen deposition, total lung collagen generation and cytokine expression) following bleomycin instillation. These results indicate that IL-16 is prominently expressed in both murine and human fibrosis however as complete loss of this cytokine did not modulate pulmonary fibrosis, IL-16 is a candidate biomarker for IPF.

Chemokine expression during mouse-hepatitis-virus-induced encephalitis: contributions of the spike and background genes.

Infection of mice with mouse hepatitis virus (MHV) strain JHM (RJHM) induces lethal encephalitis, with high macrophage and neutrophil, but minimal T-cell, infiltration into the brain when compared to the neuroattenuated strain RA59. To determine if chemokine expression corresponds with the cellular infiltrate, chemokine protein and RNA levels from the brains of infected mice were quantified. RJHM-infected mice had lower T-cell (CXCL9, CXCL10), but higher macrophage-attracting (CCL2), chemokine proteins compared to RA59. RJHM also induced significantly higher CXCL2 (a neutrophil chemoattractant) mRNA compared to RA59. The neurovirulent spike gene chimera SJHM/RA59 induces high levels of T cells and macrophages in the brain compared to the attenuated SA59/RJHM chimera. Accordingly, SJHM/RA59 induced higher levels of CXCL9, CXCL10, and CCL2 protein compared to SA59/RJHM. Chemokine mRNA patterns were in general agreement. Thus, chemokine patterns correspond with the cellular infiltrate, and the spike protein influences levels of macrophage, but not T-cell, chemokines.

Relationship between the loss of neutralizing antibody binding and fusion activity of the F protein of human respiratory syncytial virus.

To elucidate the relationship between resistance to HRSV neutralizing antibodies directed against the F protein and the fusion activity of the F protein, a recombinant approach was used to generate a panel of mutations in the major antigenic sites of the F protein. These mutant proteins were assayed for neutralizing mAb binding (ch101F, palivizumab, and MAb19), level of expression, post-translational processing, cell surface expression, and fusion activity. Functional analysis of the fusion activity of the panel of mutations revealed that the fusion activity of the F protein is tolerant to multiple changes in the site II and IV/V/VI region in contrast with the somewhat limited spectrum of changes in the F protein identified from the isolation of HRSV neutralizing antibody virus escape mutants. This finding suggests that aspects other than fusion activity may limit the spectrum of changes tolerated within the F protein that are selected for by neutralizing antibodies.

Binding kinetics, uptake and intracellular accumulation of F105, an anti-gp120 human IgG1kappa monoclonal antibody, in HIV-1 infected cells.

The use of targeting moieties is a new and exciting field of scientific research for facilitating the specific delivery of therapeutic agents in HIV-infected patients. The interaction of a potential targeting moiety with its ligand is a crucial factor in the evaluation of a targeted approach for chemotherapeutic intervention. Therefore, we have further characterized the interaction between a potential targeting agent, the monoclonal human antibody F105, and its ligand gp120, a glycoprotein expressed on the surface of HIV-1 infected cells. We demonstrate the specificity of binding and entry of F105 to infected cells. F105 was rapidly taken up into the cell and accumulated in the Golgi apparatus. Kinetic analysis of the F105-gp120 interaction revealed an equilibrium dissociation constant (K(D)) of 0.62 nM, compared with the gp120-CD4 interaction where the K(D) was determined at 35 nM. Consequently, F105 displayed a higher gp120 affinity. This was due to a slower dissociation as compared with the natural ligand. These data further underline the potential of monoclonal antibodies as targeting agents, and offer new insights into the possibility of F105 as a targeting moiety for the delivery of antiretroviral drugs to HIV-1 infected cells.

Contribution of cysteine residues in the extracellular domain of the F protein of human respiratory syncytial virus to its function.

The mature F protein of all known isolates of human respiratory syncytial virus (HRSV) contains fifteen absolutely conserved cysteine (C) residues that are highly conserved among the F proteins of other pneumoviruses as well as the paramyxoviruses. To explore the contribution of the cysteines in the extracellular domain to the fusion activity of HRSV F protein, each cysteine was changed to serine. Mutation of cysteines 37, 313, 322, 333, 343, 358, 367, 393, 416, and 439 abolished or greatly reduced cell surface expression suggesting these residues are critical for proper protein folding and transport to the cell surface. As expected, the fusion activity of these mutations was greatly reduced or abolished. Mutation of cysteine residues 212, 382, and 422 had little to no effect upon cell surface expression or fusion activity at 32 degrees C, 37 degrees C, or 39.5 degrees C. Mutation of C37 and C69 in the F2 subunit either abolished or reduced cell surface expression by 75% respectively. None of the mutations displayed a temperature sensitive phenotype.

Use of a novel cell-based fusion reporter assay to explore the host range of human respiratory syncytial virus F protein.

Human respiratory syncytial virus (HRSV) is an important respiratory pathogen primarily affecting infants, young children, transplant recipients and the elderly. The F protein is the only virion envelope protein necessary and sufficient for virus replication and fusion of the viral envelope membrane with the target host cell. During natural infection, HRSV replication is limited to respiratory epithelial cells with disseminated infection rarely, if ever, occurring even in immunocompromised patients. However, in vitro infection of multiple human and non-human cell types other than those of pulmonary tract origin has been reported. To better define host cell surface molecules that mediate viral entry and dissect the factors controlling permissivity for HRSV, we explored the host range of HRSV F protein mediated fusion. Using a novel recombinant reporter gene based fusion assay, HRSV F protein was shown to mediate fusion with cells derived from a wide range of vertebrate species including human, feline, equine, canine, bat, rodent, avian, porcine and even amphibian (Xenopus). That finding was extended using a recombinant HRSV engineered to express green fluorescent protein (GFP), to confirm that viral mRNA expression is limited in several cell types. These findings suggest that HRSV F protein interacts with either highly conserved host cell surface molecules or can use multiple mechanisms to enter cells, and that the primary determinants of HRSV host range are at steps post-entry.

Biomedicines to reduce inflammation but not viral load in chronic HCV--what's the sense?

Although cytokines and cytotoxic T lymphocytes (CTL) are among the predominant mechanisms of host defense against viral pathogens, they can induce an inflammatory response that often leads to tissue injury. Hepatitis C virus (HCV) infection, a major cause of liver-related disease, results in the induction of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), and CTL activity, followed by liver injury. Although inflammation facilitates the wound healing process, chronic persistence over several decades results in scar accumulation, fibrosis and often cirrhosis. This review summarizes biological data implicating a cause-and-effect relationship between TNF-alpha levels and the progression of fibrosis in chronic HCV infections, in contrast to the role of TNF-alpha in hepatitis B virus infections. Furthermore, an overview of therapeutic approaches to halting the inflammatory cascade in individuals with chronic HCV, including the use of agents to reduce the level of TNF-alpha, is presented.

Sustained and specific in vitro inhibition of HIV-1 replication by a protease inhibitor encapsulated in gp120-targeted liposomes.

Selective delivery of antiretrovirals to human immunodeficiency virus (HIV) infected cells may reduce toxicities associated with long-term highly active antiretroviral therapy (HAART), may improve therapeutic compliance and delay the emergence of resistance. We developed sterically stabilized pegylated liposomes coated with targeting ligands derived from the Fab' fragment of HIV-gp120-directed monoclonal antibody F105, and evaluated these liposomes as vehicles for targeted delivery of a novel HIV-1 protease inhibitor. We demonstrated that the immunoliposomes were selectively taken up by HIV-1-infected cells and localized intracellularly, enabling the establishment of a cytoplasmic reservoir of protease inhibitor. In antiviral experiments, the drug delivered by the immunoliposomes showed greater and longer antiviral activity than comparable concentrations of free drug or drug encapsulated in non-targeted liposomes. In conclusion, by combining a targeting moiety with drug-loaded liposomes, efficient and specific uptake by non-phagocytic HIV-infected cells was facilitated, resulting in drug delivery to infected cells. This approach to targeted delivery of antiretroviral compounds may enable the design of drug regimens for patients that allow increased therapeutic adherence and less toxic treatment of HIV infection.

IL-16 signaling specifically induces STAT6 activation through CD4.

Biologic activities of IL-16 have been well described (e.g., chemotaxis of CD4+ cells, CD25 upregulation, secretion of IL-1b, IL-4 and TNF-a secretion) but very few signaling events have been described. To gain a better understanding of how the biologic activities of IL-16 are regulated following receptor engagement (CD4) we have analyzed the activation state of numerous STAT proteins in primary human peripheral blood mononuclear cells (PBMCs) and the human monocytic cell line THP-1 following IL-16 stimulation. Of the four STAT proteins tested, only STAT6 was activated (phosphorylated) in a dose-dependant manner by IL-16. The activation of STAT6 was completely abolished when IL-16 was pre-incubated with soluble CD4 (the IL-16 cell surface receptor), demonstrating the need for CD4 engagement in STAT6 activation. These results are the first to demonstrate a link between IL-16 and STAT6 activation.

Diminished inflammatory responses to natural pneumovirus infection among older mice.

Immune responses to virus infection undergo significant change as part of the aging process. Here we examine the inflammatory responses of older, but otherwise immunologically naive mice to infection with pneumonia virus of mice (PVM). Although we see no changes in the extent or kinetics of virus replication, we observe diminished local production of inflammatory mediators, including MIP-1alpha, JE/MCP-1, IFN-gamma and IFN-gamma-induced MIG and IP-10, and interleukins (IL)-6 and IL-17. Levels of KC and IL-1alpha remained unchanged. Age-dependent diminished production of proinflammatory mediators was associated with diminished recruitment of granulocytes and reduced severity of clinical responses, including weight loss and respiratory dysfunction. The differences observed when comparing these results to those reported among elderly human subjects may be related to the specific extent of aging and its impact on biochemical and cellular inflammatory responses and/or the role of lifetime virus re-exposure on the clinical outcome from acute pneumovirus disease.

Characterization of the epitope for anti-human respiratory syncytial virus F protein monoclonal antibody 101F using synthetic peptides and genetic approaches.

Chimeric 101F (ch101F) is a mouse-human chimeric anti-human respiratory syncytial virus (HRSV) neutralizing antibody that recognizes residues within antigenic site IV, V, VI of the fusion (F) glycoprotein. The binding of ch101F to a series of peptides overlapping aa 422-438 spanning antigenic site IV, V, VI was analysed. Residues 423-436 comprise the minimal peptide sequence for ch101F binding. Substitution analysis revealed that R429 and K433 are critical for ch101F binding, whilst K427 makes a minor contribution. Binding of ch101F to a series of single mutations at positions 427, 429 and 433 in the F protein expressed recombinantly on the cell surface confirmed the peptide results. Sequence analysis of viruses selected for resistance to neutralization by ch101F indicated that a single change (K433T) in the F protein allowed ch101F escape. The results confirm that ch101F and palivizumab have different epitope specificity and define key residues for ch101F recognition.

Cold virus fusion or stopping fusion cold--inhibitors of the human respiratory syncytial virus F protein.

Human respiratory syncytial virus (HRSV) is a major respiratory viral pathogen causing moderate to severe upper and lower respiratory tract infections in all ages and across a wide range of patient populations. There are no currently approved vaccines and although a number of candidates are in various stages of development, the challenges are quite substantial. Presently, only a single agent is approved for HRSV prophylaxis, and therapeutic treatment options are severely limited and ineffective, particularly in the infant population. Antibody prophylaxis is restricted to use in populations at high-risk for hospitalization (infants under 35 weeks gestational age, infants with chronic lung disease, and infants with congenital heart disease). Aerosol administration of the guanosine analog ribavirin has been approved for the treatment of severe HRSV LRTI in both children and mechanically ventilated patients; however, there is still debate over its overall benefit and the risks associated with its use. Current therapy for those hospitalized due to HRSV is supportive. As such, there is great medical need for the development of agents to prevent and treat HRSV infections in all populations. Interestingly, many of the discovered agents against HRSV, both neutralizing antibodies and small molecules inhibitors, target the viral fusion (F) glycoprotein. In particular, three distinct chemical classes as exemplified by JNJ-2408068, VP-14637, and BMS-433771, which appear to block conformational intermediates of the viral fusion protein are reviewed.

Molecular mechanism of a thumb domain hepatitis C virus nonnucleoside RNA-dependent RNA polymerase inhibitor.

A new pyranoindole class of small-molecule inhibitors was studied to understand viral resistance and elucidate the mechanism of inhibition in hepatitis C virus (HCV) replication. HCV replicon variants less susceptible to inhibition by the pyranoindoles were selected in Huh-7 hepatoma cells. Variant replicons contained clusters of mutations in the NS5B polymerase gene corresponding to the drug-binding pocket on the surface of the thumb domain identified by X-ray crystallography. An additional cluster of mutations present in part of a unique beta-hairpin loop was also identified. The mutations were characterized by using recombinant replicon variants engineered with the corresponding amino acid substitutions. A single mutation (L419M or M423V), located at the pyranoindole-binding site, resulted in an 8- to 10-fold more resistant replicon, while a combination mutant (T19P, M71V, A338V, M423V, A442T) showed a 17-fold increase in drug resistance. The results of a competition experiment with purified NS5B enzyme with GTP showed that the inhibitory activity of the pyranoindole inhibitor was not affected by GTP at concentrations up to 250 microM. Following de novo initiation, the presence of a pyranoindole inhibitor resulted in the accumulation of a five-nucleotide oligomer, with a concomitant decrease in higher-molecular-weight products. The results of these studies have confirmed that pyranoindoles target the NS5B polymerase through interactions at the thumb domain. This inhibition is independent of GTP concentrations and is likely mediated by an allosteric blockade introduced by the inhibitor during the transition to RNA elongation after the formation of an initiation complex.

Novel nonnucleoside inhibitor of hepatitis C virus RNA-dependent RNA polymerase.

A novel nonnucleoside inhibitor of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), [(1R)-5-cyano-8-methyl-1-propyl-1,3,4,9-tetrahydropyano[3,4-b]indol-1-yl] acetic acid (HCV-371), was discovered through high-throughput screening followed by chemical optimization. HCV-371 displayed broad inhibitory activities against the NS5B RdRp enzyme, with 50% inhibitory concentrations ranging from 0.3 to 1.8 microM for 90% of the isolates derived from HCV genotypes 1a, 1b, and 3a. HCV-371 showed no inhibitory activity against a panel of human polymerases, including mitochondrial DNA polymerase gamma, and other unrelated viral polymerases, demonstrating its specificity for the HCV polymerase. A single administration of HCV-371 to cells containing the HCV subgenomic replicon for 3 days resulted in a dose-dependent reduction of the steady-state levels of viral RNA and protein. Multiple treatments with HCV-371 for 16 days led to a >3-log10 reduction in the HCV RNA level. In comparison, multiple treatments with a similar inhibitory dose of alpha interferon resulted in a 2-log10 reduction of the viral RNA level. In addition, treatment of cells with a combination of HCV-371 and pegylated alpha interferon resulted in an additive antiviral activity. Within the effective antiviral concentrations of HCV-371, there was no effect on cell viability and metabolism. The intracellular antiviral specificity of HCV-371 was demonstrated by its lack of activity in cells infected with several DNA or RNA viruses. Fluorescence binding studies show that HCV-371 binds the NS5B with an apparent dissociation constant of 150 nM, leading to high selectivity and lack of cytotoxicity in the antiviral assays.