A Protease-Activated Fluorescent Probe Allows Rapid Visualization of Keratinocyte Carcinoma during Excision

Keratinocyte carcinomas, including basal and squamous cell carcinomas, are the most common human cancers worldwide. While 75% of all keratinocyte carcinoma (4 million annual cases in the United States) are treated with conventional excision, this surgical modality has much lower cure rates than Mohs micrographic surgery, likely due to the bread-loaf histopathologic assessment that visualizes <1% of the tissue margins. A quenched protease-activated fluorescent probe 6qcNIR, which produces a signal only in the protease-rich tumor microenvironment, was topically applied to 90 specimens ex vivo immediately following excision. "Puzzle-fit" analysis was used to correlate the fluorescent images with histology. Probe-dependent fluorescent images correlated with cancer determined by conventional histology. Point-of-care fluorescent detection of skin cancer had a clinically relevant sensitivity of 0.73 and corresponding specificity of 0.88. Importantly, clinicians were effectively trained to read fluorescent images within 15 minutes with reliability and confidence, resulting in sensitivities of 62%-78% and specificities of 92%-97%. Fluorescent imaging using 6qcNIR allows 100% tumor margin assessment by generating en face images that correlate with histology and may be used to overcome the limitations of conventional bread-loaf histology. The utility of 6qcNIR was validated in a busy real-world clinical setting, and clinicians were trained to effectively read fluorescent margins with a short guided instruction, highlighting clinical adaptability. When used in conventional excision, this approach may result in higher cure rates at a lower cost by allowing same-day reexcision when needed, reducing patient anxiety and improving compliance by expediting postsurgical specimen assessment. SIGNIFICANCE: A fluorescent-probe-tumor-visualization platform was developed and validated in human keratinocyte carcinoma excision specimens that may provide simple, rapid, and global assessment of margins during skin cancer excision, allowing same-day reexcision when needed.

The use of 3-dimensionally printed models to optimize patient education and alleviate perioperative anxiety in Mohs micrographic surgery: A randomized controlled trial

BACKGROUND

Perioperative patient anxiety in Mohs micrographic surgery (MMS) is associated with increased postoperative pain and decreased satisfaction.

OBJECTIVE

To determine whether a 3-dimensionally printed MMS model with standardized education (SE) improves perioperative patient understanding and anxiety.

METHODS

An unblinded, randomized controlled trial was conducted, with patients randomly assigned to receive the MMS model plus SE or SE alone. Baseline and poststage understanding and anxiety were evaluated with the Visual Analog Scale (VAS) and State-Trait Anxiety Inventory (STAI). Additionally, patients completed a 6-item knowledge assessment.

RESULTS

Eighty-two patients were enrolled, 42 in the MMS model and 40 in the SE group, with similar group mean age (67.8 years), sex (59.8% male), and previous MMS experience (47.6%). Both groups experienced significant reductions in VAS anxiety and State-Trait Anxiety Inventory scores and significant increases in VAS understanding. Compared with SE alone, the MMS model group had larger VAS anxiety reduction (change, -1.31; approaching significance) than the SE group (change, -0.52; P = .052) and 5.59 (93.25%) correct responses versus 5.15 (85.83%) correct responses in the SE group (P < .028).

LIMITATIONS

Overestimations of baseline patient anxiety in our population and 91.1% recruitment of the intended study population limited study power.

CONCLUSION

A 3-dimensionally printed MMS model with SE may improve patient understanding of MMS and decrease perioperative anxiety.

Soluble Fc-Disabled Herpes Virus Entry Mediator Augments Activation and Cytotoxicity of NK Cells by Promoting Cross-Talk between NK Cells and Monocytes

CD160 is highly expressed by NK cells and is associated with cytolytic effector activity. Herpes virus entry mediator (HVEM) activates NK cells for cytokine production and cytolytic function via CD160. Fc-fusions are a well-established class of therapeutics, where the Fc domain provides additional biological and pharmacological properties to the fusion protein including enhanced serum t 1/2 and interaction with Fc receptor-expressing immune cells. We evaluated the specific function of HVEM in regulating CD160-mediated NK cell effector function by generating a fusion of the HVEM extracellular domain with human IgG1 Fc bearing CD16-binding mutations (Fc*) resulting in HVEM-(Fc*). HVEM-(Fc*) displayed reduced binding to the Fc receptor CD16 (i.e., Fc-disabled HVEM), which limited Fc receptor-induced responses. HVEM-(Fc*) functional activity was compared with HVEM-Fc containing the wild type human IgG1 Fc. HVEM-(Fc*) treatment of NK cells and PBMCs caused greater IFN-γ production, enhanced cytotoxicity, reduced NK fratricide, and no change in CD16 expression on human NK cells compared with HVEM-Fc. HVEM-(Fc*) treatment of monocytes or PBMCs enhanced the expression level of CD80, CD83, and CD40 expression on monocytes. HVEM-(Fc*)-enhanced NK cell activation and cytotoxicity were promoted via cross-talk between NK cells and monocytes that was driven by cell-cell contact. In this study, we have shown that soluble Fc-disabled HVEM-(Fc*) augments NK cell activation, IFN-γ production, and cytotoxicity of NK cells without inducing NK cell fratricide by promoting cross-talk between NK cells and monocytes without Fc receptor-induced effects. Soluble Fc-disabled HVEM-(Fc*) may be considered as a research and potentially therapeutic reagent for modulating immune responses via sole activation of HVEM receptors.

Characterization of the facial microbiome in twins discordant for rosacea

Previously, we determined that genetic and environmental factors contributed equally towards rosacea in twins. To assess an environmental factor, we characterized the malar cheek bacterial microbiome from twins discordant for rosacea. We found no significant difference in facial microbiome alpha and beta diversity between related twins discordant for rosacea. However, the relative percentage abundance of Gordonia and Geobacillus, low-abundant genera, was positively and negatively associated with rosacea severity, respectively. Our data demonstrate a significant correlation between facial microbiome and severity of rosacea in genetically matched twins and importantly that overall microbiome composition is largely unchanged.

Molecular imaging and validation of margins in surgically excised nonmelanoma skin cancer specimens

In an effort to increase the efficiency and cure rate of nonmelanoma skin cancer (NMSC) excisions, we have developed a point-of-care method of imaging and evaluation of skin cancer margins. We evaluate the skin surgical specimens using a smart, near-infrared probe (6qcNIR) that fluoresces in the presence of cathepsin proteases overexpressed in NMSC. Imaging is done with an inverted, flying-spot fluorescence scanner that reduces scatter, giving a 70% improved step response as compared to a conventional imaging system. We develop a scheme for careful comparison of fluorescent signals to histological annotation, which involves image segmentation, fiducial-based registration, and nonrigid free-form deformation on fluorescence images, corresponding color images, "bread-loafed" tissue images, hematoxylin and eosin (H&E)-stained slides, and pathological annotations. From epidermal landmarks, spatial accuracy in the bulk of the sample is ∼ 500    μ m , which when extrapolated with a linear stretch model, suggests an error at the margin of ∼ 100    μ m , within clinical reporting standards. Cancer annotations on H&E slides are transformed and superimposed on the fluorescence images to generate the final results. Using this methodology, fluorescence cancer signals are generally found to correspond spatially with histological annotations. This method will allow us to accurately analyze molecular probes for imaging skin cancer margins.

In vitro Evidence That Combination Therapy With CD16-Bearing NK-92 Cells and FDA-Approved Alefacept Can Selectively Target the Latent HIV Reservoir in CD4+ CD2hi Memory T Cells

Elimination of the latent HIV reservoir remains the biggest hurdle to achieve HIV cure. In order to specifically eliminate HIV infected cells they must be distinguishable from uninfected cells. CD2 was recently identified as a potential marker enriched in the HIV-1 reservoir on CD4+ T cells, the largest, longest-lived and best-characterized constituent of the HIV reservoir. We previously proposed to repurpose FDA-approved alefacept, a humanized α-CD2 fusion protein, to reduce the HIV reservoir in CD2hi CD4+ memory T cells. Here, we show the first evidence that alefacept can specifically target and reduce CD2hi HIV infected cells in vitro. We explore a variety of natural killer (NK) cells as mediators of antibody-dependent cell-mediated cytotoxicity (ADCC) including primary NK cells, expanded NK cells as well as the CD16 transduced NK-92 cell line which is currently under study in clinical trials as a treatment for cancer. We demonstrate that CD16.NK-92 has a natural preference to kill CD2hi CD45RA- memory T cells, specifically CD45RA- CD27+ central memory/transitional memory (TCM/TM) subset in both healthy and HIV+ patient samples as well as to reduce HIV DNA from HIV+ samples from donors well controlled on antiretroviral therapy. Lastly, alefacept can combine with CD16.NK-92 to decrease HIV DNA in some patient samples and thus may yield value as part of a strategy toward sustained HIV remission.

A requirement for slc15a4 in imiquimod-induced systemic inflammation and psoriasiform inflammation in mice

There is competing evidence that plasmacytoid dendritic cells (pDC), the most potent source of IFN-I, may initiate psoriasis. We targeted pDC function using the slc15a4^feeble loss-of-function mouse whose pDC are unresponsive to TLR agonists. slc15a4^feeble treated with the topical TLR7-agonist imiquimod (IMQ) demonstrated decreased epidermal thickening 24 hours post-treatment which was more pronounced by day 5 as compared to wildtype mice. These findings were specific to the acute IMQ model and not the protracted IL23 model that drives inflammation downstream of TLR activation. Systemically, slc15a4 was required for IMQ-induced weight loss and cutaneous accumulation of CD4+ and Siglec H+, but not CD11b+ cells. Consistent with this phenotype and the function of slc15a4, induction of IFN-I was virtually absent systemically and via cutaneous gene expression. Induction of other inflammatory cytokines (cytokine storm) was modestly blunted in slc15a4^feeble except for inflammasome-associated genes consistent with slc15a4 being required for TLR7-mediated (but not inflammasome-mediated) inflammation downstream of IMQ. Surprisingly, only IFN-I gene expression was suppressed within IMQ-treated skin. Other genes including conserved psoriasiform trademark gene expression were augmented in slc15a4^feeble versus littermate controls. Taken together, we have identified a role for slc15a4 but not canonical psoriasiform genes in the imiquimod model of psoriasiform dermatitis.

Soluble Markers of Immune Activation Differentially Normalize and Selectively Associate with Improvement in AST, ALT, Albumin, and Transient Elastography During IFN-Free HCV Therapy

Background

During chronic hepatitis C virus (HCV) infection, Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) levels mark active liver inflammation and tissue damage, while albumin reflects synthetic liver function and nutritional status. Transient Elastography (TE) is a clinical measure of liver stiffness that facilitates evaluation of liver damage stage. While a portion of the TE score is attributable to liver fibrosis and relatively irreversible damage, another component of the TE score is attributable to liver inflammation or edema. Markers of inflammation during chronic HCV infection include soluble markers of immune activation, which are also associated with morbid outcome (including cardiovascular disease and liver-disease progression). Whether soluble markers of immune activation or changes in their level during HCV therapy relate to normalization of AST, ALT, Albumin, or TE score, is not clear.

Methods

We evaluated soluble markers of immune activation (plasma sCD14, IL-6, sCD163, autotaxin [ATX], and Mac2BP) and TE score, and their relationship in 20 HCV-infected patients before, during, and after HCV-directed IFN-free direct-acting antiviral (DAA) therapy. We evaluated normalization of parameters and the relationship between each over a 6-month window.

Results

Before therapy, serum AST levels positively correlated with plasma levels of sCD14, sCD163, and Mac2BP, while ALT levels positively correlated with Mac2BP. Serum albumin level negatively correlated with plasma IL-6 and ATX levels. IFN-free therapy uniformly resulted in sustained virological response at 12 and 24 weeks after therapy completion. After initiation of therapy AST and ALT normalized, while levels of ATX, Mac2BP, sCD163, and TE score partially normalized over 6 months. Additionally, change in AST level and APRI score correlated with change in sCD163, IL-6, and Mac2BP levels, and change in ALT correlated with change in IL-6 and Mac2BP levels. Improvement in TE score correlated with a decrease in the level of sCD14 at week 4, and almost statistically significant with decrease in sCD14 at weeks 20-24 after initiation of IFN-free HCV therapy.

Conclusions

Soluble markers of immune activation normalize or partially normalize at different rates after initiation of curative HCV DAA therapy, and TE scores improve, with wide variability in the degree of absolute improvement in liver stiffness from patient to patient. Decline magnitude of sCD14 was associated with improvement in TE score, while magnitude of improvement in AST correlated with reduction in sCD163 levels. These data provide support for a model where monocyte/Kupffer cell activation may account for a portion of the liver inflammation and edema, which is at least partially reversible following initiation of HCV DAA therapy.

Cetylpyridinium Chloride (CPC) Exhibits Potent, Rapid Activity Against Influenza Viruses in vitro and in vivo

Background:

There is a continued need for strategies to prevent influenza. While cetylpyridinium chloride (CPC), a broad-spectrum antimicrobial agent, has an extensive antimicrobial spectrum, its ability to affect respiratory viruses has not been studied in detail.

Objectives:

Here, we evaluate the ability of CPC to disrupt influenza viruses in vitro and in vivo.

Methods:

The virucidal activity of CPC was evaluated against susceptible and oseltamivir- resistant strains of influenza viruses. The effective virucidal concentration (EC) of CPC was determined using a hemagglutination assay and tissue culture infective dose assay. The effect of CPC on viral envelope morphology and ultrastructure was evaluated using transmission electron microscopy (TEM). The ability of influenza virus to develop resistance was evaluated after multiple passaging in sub-inhibitory concentrations of CPC. Finally, the efficacy of CPC in formulation to prevent and treat influenza infection was evaluated using the PR8 murine influenza model.

Results:

The virucidal effect of CPC occurred within 10 minutes, with mean EC₅₀ and EC_2log ranging between 5 to 20 μg/mL, for most strains of influenza tested regardless of type and resistance to oseltamivir. Examinations using TEM showed that CPC disrupted the integrity of the viral envelope and its morphology. Influenza viruses demonstrated no resistance to CPC despite prolonged exposure. Treated mice exhibited significantly increased survival and maintained body weight compared to untreated mice.

Conclusions:

The antimicrobial agent CPC possesses virucidal activity against susceptible and resistant strains of influenza virus by targeting and disrupting the viral envelope. Substantial virucidal activity is seen even at very low concentrations of CPC without development of resistance. Moreover, CPC in formulation reduces influenza-associated mortality and morbidity in vivo.

Overexpression of AQP3 and AQP10 in the skin exacerbates psoriasiform acanthosis

We previously observed that aquaporin-3 and aquaporin-10 are upregulated in the epidermis of hand dermatitis patients (Med. Hypotheses, 84, 2015, 498). To address the functional relevance of this upregulation, we overexpressed AQP3/AQP10 in mice using the human K1 promoter. Combining imiquimod with detergent-containing water challenge, a common trigger in hand and other dermatitis, resulted in an increase in acanthosis in mice overexpressing AQP3 or AQP3 and AQP10. Aquaporin overexpression also drove a trend towards greater weight loss in these animals. These data support a role for cutaneous aquaporins in the pathogenesis of dermatitis and as a potential target in their treatment.

During Hepatitis C Virus (HCV) Infection and HCV-HIV Coinfection, an Elevated Plasma Level of Autotaxin Is Associated With Lysophosphatidic Acid and Markers of Immune Activation That Normalize During Interferon-Free HCV Therapy

BACKGROUND

 Immune activation predicts morbidity during hepatitis C virus (HCV) infection and human immunodeficiency virus (HIV) infection, although mechanisms underlying immune activation are unclear. Plasma levels of autotaxin and its enzymatic product, lysophosphatidic acid (LPA), are elevated during HCV infection, and LPA activates immunocytes, but whether this contributes to immune activation is unknown.

METHODS

 We evaluated plasma levels of autotaxin, interleukin 6 (IL-6), soluble CD14 (sCD14), soluble CD163 (sCD163), and Mac2 binding protein (Mac2BP) during HCV infection, HIV infection, and HCV-HIV coinfection, as well as in uninfected controls, before and after HIV antiretroviral therapy (ART) initiation and during interferon-free HCV therapy.

RESULTS

 We observed greater plasma autotaxin levels in HCV-infected and HCV-HIV-coinfected participants, compared with uninfected participants, primarily those with a higher ratio of aspartate aminotransferase level to platelet count. Autotaxin levels correlated with IL-6, sCD14, sCD163, Mac2BP, and LPA levels in HCV-infected participants and with Mac2BP levels in HCV-HIV-coinfected participants, while in HIV-infected individuals, sCD14 levels correlated with Mac2BP levels. Autotaxin, LPA, and sCD14 levels normalized, while sCD163 and Mac2BP levels partially normalized within 6 months of starting interferon-free HCV therapy. sCD163 and IL-6 levels normalized within 6 months of starting ART for HIV infection. In vitro, LPA activated monocytes.

CONCLUSIONS

 These data indicate that elevated levels of autotaxin and soluble markers of immune activation during HCV infection are partially reversible within 6 months of initiating interferon-free HCV treatment and that autotaxin may be causally linked to immune activation during HCV infection and HCV-HIV coinfection.

Genetic vs Environmental Factors That Correlate With Rosacea: A Cohort-Based Survey of Twins

IMPORTANCE

To our knowledge, this is the first study on rosacea to formally define genetic and environmental contributions.

OBJECTIVES

To study a cohort of identical and fraternal twins to determine whether genetic factors contribute to rosacea development and, if genetic factors are present, quantitatively estimate the genetic contribution, as well as to identify environmental factors that correlate with rosacea by controlling for genetic susceptibility.

DESIGN, SETTING, AND PARTICIPANTS

Identical and fraternal twins were surveyed regarding risk factors implicated in rosacea. Faculty dermatologists determined a rosacea score for each twin participant according to the National Rosacea Society (NRS) grading system. Data were collected at the annual Twins Days Festival in Twinsburg, Ohio, on August 4-5, 2012, and August 2-3, 2013. Analysis was conducted for several months after each meeting. A cohort of 550 twin individuals, with most from Ohio, Pennsylvania, and the northeastern United States, participated.

MAIN OUTCOMES AND MEASURES

The NRS score and rosacea subtype were assessed using the NRS grading system and physical examination by board-certified dermatologists.

RESULTS

Among the 275 twin pairs (550 individuals), there were 233 identical twin pairs with a mean rosacea score of 2.46 and 42 fraternal twin pairs with a mean rosacea score of 0.75. We observed a higher association of NRS scores between identical vs fraternal twins (r = 0.69 vs r = 0.46; P = .04), demonstrating a genetic contribution. Using the ACE model (proportion of variance in a trait heritable secondary to additive genetics [A] vs the proportions due to a common environment [C] and unique environment [E]), we calculated this genetic contribution to be 46%. A higher NRS score was also significantly associated with the following factors: age (r = 0.38; P < .001) and lifetime UV radiation exposure (r = 0.26; P < .001). These associations remained after use of propensity score matching to adjust for multicollinearity. Other correlated variables included body mass index (r = 0.21; P < .001), smoking (r = 0.10; P < .02), alcohol consumption (r = 0.11; P = .01), cardiovascular comorbidity (r = 0.17; P < .001), and skin cancer comorbidity (r = 0.19; P < .001).

CONCLUSIONS AND RELEVANCE

The study of twins allows us to separate genetic susceptibility and the influence of environmental factors affecting rosacea. We found that approximately half of the contribution to the NRS score could be accounted for by genetics and the other half by environment. We identified correlations between rosacea and UV radiation exposure, alcohol, smoking, skin cancer history, cardiac comorbidity, and age. These findings may help improve current management and expectations of individuals affected by rosacea.

Tropism of CPMV to Professional Antigen Presenting Cells Enables a Platform to Eliminate Chronic Infections

Chronic viral infections (e.g., HIV, HBV, HCV) represent a significant source of morbidity and mortality with over 500 million people infected worldwide. Dendritic cells (DCs) and macrophages are key cell types for productive viral replication and persistent systemic infection. We demonstrate that the plant virus cowpea mosaic virus (CPMV) displays tropism for such antigen presenting cells in both mice and humans, thus making it an ideal candidate for targeted drug delivery toward viral infections. Furthermore, we show inhibition of a key host protein for viral infection, site-1 protease (S1P), using the small molecule PF-429242 in the model pathogen arenavirus lymphocytic choriomeningitis virus (LCMV) limits viral growth. By packaging PF-429242 in CPMV, we are able to control drug release and efficiently deliver the drug. This sets the groundwork for utilizing the natural tropism of CPMV for a therapeutic approach that specifically targets cell types most commonly subverted by chronic viruses.

The key role of aquaporin 3 and aquaporin 10 in the pathogenesis of pompholyx

Pompholyx remains a chronic skin affliction without a compelling pathophysiological explanation. The disease is characterized by the sudden onset of vesicles exclusively in the palms and soles which generally resolves. However, the disease may progress and the vesicles may expand and fuse; with chronicity there is deep fissuring. Multiple therapeutic approaches are available, but the disease is often resistant to conventional treatments. Currently, oral alitretinoin is used for patients with resistant chronic disease; however, this therapy is only approved for use in the UK, Europe and Canada. In this paper we wish to put forward a hypothesis: exposure to water and the subsequent steep osmotic gradient imbalance are key factors driving skin dehydration seen in pompholyx patients once the disease becomes chronic. The mechanistic explanation for the epidermal fissuring might lie in the over-expression across the mid and upper epidermis, including the stratum corneum, of two water/glycerol channel proteins aquaporin 3 and aquaporin 10, expressed in the keratinocytes of afflicted pompholyx patients. The over-expression of these two aquaporins may bridge the abundantly hydrated dermis and basal epidermis to the outer environment allowing cutaneous water and glycerol to flow outward. The beneficial effects reported in alitretinoin-treated patients with chronic hand eczemas may be due potential regulation of aquaporin 3 and aquaporin 10 by alitretinoin.

Role of lymphocytic choriomeningitis virus (LCMV) in understanding viral immunology: past, present and future

Lymphocytic choriomeningitis virus (LCMV) is a common infection of rodents first identified over eighty years ago in St. Louis, MO, U.S.A. It is best known for its application in immunological studies. The history of LCMV closely correlates with the development of modern immunology. With the use of LCMV as a model pathogen several key concepts have emerged: Major Histocompatibility Complex (MHC) restriction, T cell memory, persistent infections, T cell exhaustion and the key role of immune pathology in disease. Given the phenomenal infrastructure within this field (e.g., defined immunodominant and subdominant epitopes to all T cell receptor specificities as well as the cognate tetramers for enumeration in vivo) the study of LCMV remains an active and productive platform for biological research across the globe to this day. Here we present a historical primer that highlights several breakthroughs since the discovery of LCMV. Next, we highlight current research in the field and conclude with our predictions for future directions in the remarkable field of LCMV research.

ENU-induced phenovariance in mice: inferences from 587 mutations

Background

We present a compendium of N-ethyl-N-nitrosourea (ENU)-induced mouse mutations, identified in our laboratory over a period of 10 years either on the basis of phenotype or whole genome and/or whole exome sequencing, and archived in the Mutagenetix database. Our purpose is threefold: 1) to formally describe many point mutations, including those that were not previously disclosed in peer-reviewed publications; 2) to assess the characteristics of these mutations; and 3) to estimate the likelihood that a missense mutation induced by ENU will create a detectable phenotype.

Findings

In the context of an ENU mutagenesis program for C57BL/6J mice, a total of 185 phenotypes were tracked to mutations in 129 genes. In addition, 402 incidental mutations were identified and predicted to affect 390 genes. As previously reported, ENU shows strand asymmetry in its induction of mutations, particularly favoring T to A rather than A to T in the sense strand of coding regions and splice junctions. Some amino acid substitutions are far more likely to be damaging than others, and some are far more likely to be observed. Indeed, from among a total of 494 non-synonymous coding mutations, ENU was observed to create only 114 of the 182 possible amino acid substitutions that single base changes can achieve. Based on differences in overt null allele frequencies observed in phenotypic vs. non-phenotypic mutation sets, we infer that ENU-induced missense mutations create detectable phenotype only about 1 in 4.7 times. While the remaining mutations may not be functionally neutral, they are, on average, beneath the limits of detection of the phenotypic assays we applied.

Conclusions

Collectively, these mutations add to our understanding of the chemical specificity of ENU, the types of amino acid substitutions it creates, and its efficiency in causing phenovariance. Our data support the validity of computational algorithms for the prediction of damage caused by amino acid substitutions, and may lead to refined predictions as to whether specific amino acid changes are responsible for observed phenotypes. These data form the basis for closer in silico estimations of the number of genes mutated to a state of phenovariance by ENU within a population of G3 mice.

Slc15a4, a gene required for pDC sensing of TLR ligands, is required to control persistent viral infection

Plasmacytoid dendritic cells (pDCs) are the major producers of type I IFN in response to viral infection and have been shown to direct both innate and adaptive immune responses in vitro. However, in vivo evidence for their role in viral infection is lacking. We evaluated the contribution of pDCs to acute and chronic virus infection using the feeble mouse model of pDC functional deficiency. We have previously demonstrated that feeble mice have a defect in TLR ligand sensing. Although pDCs were found to influence early cytokine secretion, they were not required for control of viremia in the acute phase of the infection. However, T cell priming was deficient in the absence of functional pDCs and the virus-specific immune response was hampered. Ultimately, infection persisted in feeble mice. We conclude that pDCs are likely required for efficient T cell priming and subsequent viral clearance. Our data suggest that reduced pDC functionality may lead to chronic infection.

The immune system consists of two arms aimed at fighting infection. Innate immunity represents the first barrier of defense to swiftly react – within minutes – following intrusion by a pathogen. Adaptive immunity is activated a few days later. Cross-talk between these two systems is critical but the means of communication are not yet fully understood. Plasmacytoid dendritic cells (pDCs) are innate immune cells best recognized for their ability to produce type I interferon (e.g. in response to viral infection.) Evidence for pDCs to modulate the adaptive system in vivo is only recent and still elusive. Using a newly described mouse model named feeble that is characterized by functional deficiency of pDCs, we analysed the role of feeble in the context of acute and chronic viral infection. We found that the feeble mutation affecting pDCs is dispensable for immunity during an acute infection. However our data show that feeble mice failed to control a chronic infection. This was likely due to a reduction in early cytokine secretion and improper activation of adaptive T cells, resulting in virus persistence. Therefore we propose that pDCs are critical for the resolution of chronic infection by linking both arms of immunity.

Hypomorphic mutation in the site-1 protease Mbtps1 endows resistance to persistent viral infection in a cell-specific manner

The prototypic arenavirus lymphocytic choriomeningitis virus (LCMV), which naturally persists in rodents, represents a model for HIV, HBV, and HCV. Cleavage of the viral glycoprotein precursor by membrane-bound transcription factor peptidase, site 1 (Mbtps1 or site-1 protease), is crucial for the life cycle of arenaviruses and therefore represents a potential target for therapy. Recently, we reported a viable hypomorphic allele of Mbtps1 (woodrat) encoding a protease with diminished enzymatic activity. Using the woodrat allele, we examine the role of Mbtps1 during persistent LCMV infection. Surprisingly, Mbtps1 inhibition limits persistent but not acute viral infection and is associated with an organ/cell type-specific decrease in viral titers. Analysis of bone marrow-derived dendritic cells from woodrat mice supports their specific role in resolving persistent viral infection. These results support in vivo targeting of Mbtps1 in the treatment of arenavirus infections and demonstrate a critical role for dendritic cells in persistent viral infections.

Gamma interferon blocks gammaherpesvirus reactivation from latency

Establishment of latent infection and reactivation from latency are critical aspects of herpesvirus infection and pathogenesis. Interfering with either of these steps in the herpesvirus life cycle may offer a novel strategy for controlling herpesvirus infection and associated disease pathogenesis. Prior studies show that mice deficient in gamma interferon (IFN-gamma) or the IFN-gamma receptor have elevated numbers of cells reactivating from murine gammaherpesvirus 68 (gammaHV68) latency, produce infectious virus after the establishment of latency, and develop large-vessel vasculitis. Here, we demonstrate that IFN-gamma is a powerful inhibitor of reactivation of gammaHV68 from latency in tissue culture. In vivo, IFN-gamma controls viral gene expression during latency. Importantly, depletion of IFN-gamma in latently infected mice results in an increased frequency of cells reactivating virus. This demonstrates that IFN-gamma is important for immune surveillance that limits reactivation of gammaHV68 from latency.

Murine cytomegalovirus paralyzes macrophages by blocking IFN gamma-induced promoter assembly

Macrophages (M phi) are activated by IFN gamma and are important cellular targets for infection by human and murine cytomegalovirus (MCMV), making it advantageous for CMVs to block IFN gamma-induced M phi differentiation. We found that MCMV infection inhibited IFN gamma regulation of many genes in M phi. MCMV infection blocked IFN gamma responses at the level of transcription without blocking Janus kinase/signal transducer and activator of transcription pathway activation and targeted IFN response factor 1- and class II transactivator-dependent and independent promoters. MCMV did not alter basal transcription from IFN gamma-responsive promoters and left the majority of cellular transcripts unchanged even after 48 h of infection. The effects of MCMV infection were specific to chromosomal rather than transiently transfected promoters. Characterization of the IFN gamma-responsive chromosomal class II transactivator promoter revealed that MCMV infection blocked IFN gamma-induced promoter assembly, allowing the virus to transcriptionally paralyze infected M phi responses while allowing basal transcription to proceed.

Murine cytomegalovirus infection inhibits tumor necrosis factor alpha responses in primary macrophages

Despite robust host immune responses the betaherpesvirus murine cytomegalovirus (MCMV) is able to establish lifelong infection. This capacity is due at least in part to the virus utilizing multiple immune evasion mechanisms to blunt host responses. Macrophages are an important cell for MCMV infection, dissemination, and latency despite expression in the host of multiple cytokines, including tumor necrosis factor alpha (TNF-alpha), that can induce an antiviral state in macrophages or other cells. In this study, we found that MCMV infection of bone marrow-derived macrophages inhibited TNF-alpha-induced ICAM-1 surface expression and mRNA expression in infected cells via expression of immediate early and/or early viral genes. MCMV infection blocked TNF-alpha-induced nuclear translocation of NF-kappaB. This inhibition of TNF-alpha signaling was explained by a decrease in TNF receptor 1 (TNFR1) and TNFR2 that was due to decreased mRNA for the latter. These findings provide a mechanism by which MCMV can evade the effects of an important host cytokine in macrophages.

Novel cell type-specific antiviral mechanism of interferon gamma action in macrophages

Interferon (IFN)-gamma and macrophages (Mphi) play key roles in acute, persistent, and latent murine cytomegalovirus (MCMV) infection. IFN-gamma mechanisms were compared in embryonic fibroblasts (MEFs) and bone marrow Mphi (BMMphi). IFN-gamma inhibited MCMV replication in a signal transducer and activator of transcription (STAT)-1alpha-dependent manner much more effectively in BMMphi (approximately 100-fold) than MEF (5-10-fold). Although initial STAT-1alpha activation by IFN-gamma was equivalent in MEF and BMMphi, microarray analysis demonstrated that IFN-gamma regulates different sets of genes in BMMphi compared with MEFs. IFN-gamma inhibition of MCMV growth was independent of known mechanisms involving IFN-alpha/beta, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase RNA activated (PKR), RNaseL, and Mx1, and did not involve IFN-gamma-induced soluble mediators. To characterize this novel mechanism, we identified the viral targets of IFN-gamma action, which differed in MEF and BMMphi. In BMMphi, IFN-gamma reduced immediate early 1 (IE1) mRNA during the first 3 h of infection, and significantly reduced IE1 protein expression for 96 h. Effects of IFN-gamma on IE1 protein expression were independent of RNaseL and PKR. In contrast, IFN-gamma had no significant effects on IE1 protein or mRNA expression in MEFs, but did decrease late gene mRNA expression. These studies in primary cells define a novel mechanism of IFN-gamma action restricted to Mphi, a cell type key for MCMV pathogenesis and latency.

The Cpx envelope stress response is controlled by amplification and feedback inhibition

In Escherichia coli, the Cpx two-component regulatory system activates expression of protein folding and degrading factors in response to misfolded proteins in the bacterial envelope (inner membrane, periplasm, and outer membrane). It is comprised of the histidine kinase CpxA and the response regulator CpxR. This response plays a role in protection from stresses, such as elevated pH, as well as in the biogenesis of virulence factors. Here, we show that the Cpx periplasmic stress response is subject to amplification and repression through positive and negative autofeedback mechanisms. Western blot and operon fusion analyses demonstrated that the cpxRA operon is autoactivated. Conditions that lead to elevated levels of phosphorylated CpxR cause a concomitant increase in transcription of cpxRA. Conversely, overproduction of CpxP, a small, Cpx-regulated protein of previously unknown function, represses the regulon and can block activation of the pathway. This repression is dependent on an intact CpxA sensing domain. The ability to autoactivate and then subsequently repress allows for a temporary amplification of the Cpx response that may be important in rescuing cells from transitory stresses and cueing the appropriately timed elaboration of virulence factors.