Dengue virus (DENV) causes pathologies ranging from the febrile illness dengue fever to the potentially lethal severe dengue disease. A major risk factor for developing severe dengue disease is the presence of sub-protective DENV-reactive antibodies from a previous infection (or from an immune mother), which can induce antibody-dependent enhancement of infection (ADE). However, infection in the presence of sub-protective anti-DENV antibodies does not always result in severe disease, suggesting that other factors influence disease severity. This study investigates how CD8+ T cell responses influence the outcome of antibody-mediated severe dengue disease. Mice were primed with alum-adjuvanted UV-inactivated DENV prior to challenge with DENV. Priming failed to induce robust CD8+ T cell responses, and induced non-neutralizing antibody responses that increased disease severity upon infection. Transfer of exogenous DENV-activated CD8+ T cells into primed mice prior to infection prevented antibody-dependent enhancement and dramatically reduced viral load. Our results suggest that in the presence of sub-protective anti-DENV antibodies, efficient CD8+ T cell responses reduce the risk of antibody-mediated severe dengue disease.

With 2.5 billion people at risk, dengue is a major emerging disease threat and an escalating public health problem worldwide. Dengue virus causes disease ranging from a self-limiting febrile illness (dengue fever) to the potentially fatal dengue hemorrhagic fever/dengue shock syndrome. Severe dengue disease is associated with sub-protective levels of antibody, which exacerbate disease upon re-infection. A dengue vaccine should generate protective immunity without increasing severity of disease. To date, the determinants of vaccine-mediated protection against dengue remain unclear, and additional correlates of protection are urgently needed. Here, mice were immunized with viral replicon particles expressing the dengue envelope protein ectodomain to assess the relative contribution of humoral versus cellular immunity to protection. Vaccination with viral replicon particles provided robust protection against dengue challenge. Vaccine-induced humoral responses had the potential to either protect from or exacerbate dengue disease upon challenge, whereas cellular immune responses were beneficial. This study explores the immunological basis of protection induced by a dengue vaccine and suggests that a safe and efficient vaccine against dengue should trigger both arms of the immune system.

The antiviral activity of UV-4 was previously demonstrated against dengue virus serotype 2 (DENV2) in multiple mouse models. Herein, step-wise minimal effective dose and therapeutic window of efficacy studies of UV-4B (UV-4 hydrochloride salt) were conducted in an antibody-dependent enhancement (ADE) mouse model of severe DENV2 infection in AG129 mice lacking types I and II interferon receptors. Significant survival benefit was demonstrated with 10–20 mg/kg of UV-4B administered thrice daily (TID) for seven days with initiation of treatment up to 48 h after infection. UV-4B also reduced infectious virus production in in vitro antiviral activity assays against all four DENV serotypes, including clinical isolates. A set of purified enzyme, in vitro, and in vivo studies demonstrated that inhibition of endoplasmic reticulum (ER) α-glucosidases and not the glycosphingolipid pathway appears to be responsible for the antiviral activity of UV-4B against DENV. Along with a comprehensive safety package, these and previously published data provided support for an Investigational New Drug (IND) filing and Phases 1 and 2 clinical trials for UV-4B with an indication of acute dengue disease.

Dengue virus (DENV) is a major public health threat worldwide. Infection with one of the four serotypes of DENV results in a transient period of protection against reinfection with all serotypes (cross-protection), followed by lifelong immunity to the infecting serotype. While a protective role for neutralizing antibody responses is well established, the contribution of T cells to reinfection is less clear, especially during heterotypic reinfection. This study investigates the role of T cells during homotypic and heterotypic DENV reinfection. Mice were sequentially infected with homotypic or heterotypic DENV serotypes, and T cell subsets were depleted before the second infection to assess the role of DENV-primed T cells during reinfection. Mice primed nonlethally with DENV were protected against reinfection with either a homotypic or heterotypic serotype 2 weeks later. Homotypic priming induced a robust neutralizing antibody response, whereas heterotypic priming elicited binding, but nonneutralizing antibodies. CD8 ؉ T cells were required for protection against heterotypic, but not homotypic, reinfection. These results suggest that T cells can contribute crucially to protection against heterotypic reinfection in situations where humoral responses alone may not be protective. Our findings have important implications for vaccine design, as they suggest that inducing both humoral and cellular responses during vaccination may maximize protective efficacy across all DENV serotypes. IMPORTANCEDengue virus is present in more than 120 countries in tropical and subtropical regions. Infection with dengue virus can be asymptomatic, but it can also progress into the potentially lethal severe dengue disease. There are four closely related dengue virus serotypes. Infection with one serotype results in a transient period of resistance against all serotypes (cross-protection), followed by lifelong resistance to the infecting serotype, but not the other ones. The duration and mechanisms of the transient cross-protection period remain elusive. This study investigates the contribution of cellular immunity to cross-protection using mouse models of DENV infection. Our results demonstrate that cellular immunity is crucial to mediate cross-protection against reinfection with a different serotype, but not for protection against reinfection with the same serotype. A better understanding of the mediators responsible for the cross-protection period is important for vaccine design, as an ideal vaccine against dengue virus should efficiently protect against all serotypes.T he four serotypes of dengue virus (DENV) are the etiologic agent of dengue, a rapidly spreading arboviral disease that is present in more than 120 countries (1-5). Recent estimates suggest that more than 3.5 billion people living in tropical and subtropical regions are at risk of infection, with 390 million infections per year, of which 96 million are symptomatic (1-3).Infection with DENV is often asymptomatic (6, 7), but if disease is apparent, it ranges from den...

Macrophages have important functional roles in regulating the timely promotion and resolution of inflammation. While many of the intracellular signaling pathways involved in the pro-inflammatory responses of macrophages are well characterized, the components that regulate macrophage reparative properties are less well understood. We identified the MEK1/2 pathway as a key regulator of macrophage reparative properties. Pharmacological inhibition of the MEK1/2 pathway (MEKi) significantly increased expression of IL-4/IL-13 (M2) responsive genes in murine bone marrow-derived and alveolar macrophages. Deletion of the MEK1 gene using LysMCre+/+MEK1fl/fl macrophages as an alternate approach yielded similar results. MEKi enhanced STAT6 phosphorylation, and MEKi induced changes in M2 polarization were dependent on STAT6. In addition, MEKi-treatment significantly increased both murine and human macrophage efferocytosis of apoptotic cells (AC) independent of macrophage polarization and STAT6. These phenotypes were associated with increased gene and protein expression of Mertk, Tyro3, and Abca1, three proteins that promote macrophage efferocytosis. We also studied the effects of MEKi on in vivo macrophage efferocytosis and polarization. MEKi treated mice had increased efferocytosis of apoptotic PMNs instilled into the peritoneum. Furthermore, administration of MEKi after LPS-induced lung injury led to improved recovery of weight, fewer neutrophils in the alveolar compartment, and greater macrophage M2 polarization. Collectively, these results show that MEK1/2 inhibition is capable of promoting reparative properties of both murine and human macrophages. These studies suggest that the MEK1/2 pathway may be a therapeutic target to promote the resolution of inflammation via modulation of macrophage functions.

Background: Macrophage plasticity allows cells to adopt different phenotypes, a property with important implications in disorders such as cystic fibrosis (CF) and asthma. Objective: We sought to examine the transcriptional and functional significance of macrophage repolarization from an M1 to an M2 phenotype and assess the role of a common human genetic disorder (CF) and a prototypical allergic disease (asthma) in this transformation. Methods: Monocyte-derived macrophages were collected from healthy subjects and patients with CF and polarized to an M2 state by using IL-4, IL-10, glucocorticoids, apoptotic PMNs, or azithromycin. We performed transcriptional profiling and

Chronic obstructive pulmonary disease (COPD) comprises chronic bronchitis and emphysema, and is a leading cause of morbidity and mortality. Because tissue destruction is the prominent characteristic of emphysema, extracellular proteinases, particularly those with elastolytic ability, are often considered to be key drivers in this disease. Several human and mouse studies have implicated roles for matrix metalloproteinases (MMPs), particularly macrophage-derived proteinases, in COPD pathogenesis. MMP-28 is expressed by the pulmonary epithelium and macrophage, and we have found that it regulates macrophage recruitment and polarization. We hypothesized that MMP-28 has contributory roles in emphysema via alteration of macrophage numbers and activation. Because of the established association of emphysema pathogenesis to macrophage influx, we evaluated the inflammatory changes and lung histology of Mmp28 mice exposed to 3 and 6 months of cigarette smoke. At earlier time points, we found altered macrophage polarization in the smoke-exposed Mmp28 lung consistent with other published findings that MMP-28 regulates macrophage activation. At both 3 and 6 months, Mmp28 mice had blunted inflammatory responses more closely resembling nonsmoked mice, with a reduction in neutrophil recruitment and CXCL1 chemokine expression. By 6 months, Mmp28 mice were protected from emphysema. These results highlight a previously unrecognized role for MMP-28 in promoting chronic lung inflammation and tissue remodeling induced by cigarette smoke and highlight another potential target to modulate COPD.

We tested the role of Stat5 in dendritic cell (DC) and alveolar macrophage homeostasis in the lung using CD11c-cre mediated deletion (Cre+5f/f). We show that Stat5 is required for CD103+ dendritic cell (DC) and alveolar macrophage development. We found that fetal monocyte maturation into alveolar macrophages was impaired in Cre+5f/f mice, and we also confirmed impaired alveolar macrophage development of progenitor cells using mixed chimera experiments. In the absence of Stat5 signaling in alveolar macrophages, mice developed alveolar proteinosis with altered lipid homeostasis. In addition, loss of Stat5 in CD11c+ cells was associated with exaggerated LPS-induced inflammatory responses and vascular leak. In Cre+5f/f mice, there was loss of immune-dampening effects on epithelial cells, a key source of CCL2 that serves to recruit monocytes/macrophages. These findings demonstrate the critical importance of Stat5 signaling in maintaining lung homeostasis and underscore the importance of resident macrophages in moderating tissue damage and excess inflammation.