Contrasting functions of ATP hydrolysis by MDA5 and LGP2 in viral RNA sensing

Cytosolic long dsRNA, among the most potent proinflammatory signals, is recognized by melanoma differentiation-associated protein 5 (MDA5). MDA5 binds dsRNA cooperatively forming helical filaments. ATP hydrolysis by MDA5 fulfills a proofreading function by promoting dissociation of shorter endogenous dsRNs from MDA5 while allowing longer viral dsRNAs to remain bound leading to activation of interferon-β responses. Here, we show that adjacent MDA5 subunits in MDA5-dsRNA filaments hydrolyze ATP cooperatively, inducing cooperative filament disassembly. Consecutive rounds of ATP hydrolysis amplify the filament footprint, displacing tightly bound proteins from dsRNA. Our electron microscopy and biochemical assays show that LGP2 binds to dsRNA at internal binding sites through noncooperative ATP hydrolysis. Unlike MDA5, LGP2 has low nucleic acid selectivity and can hydrolyze GTP and CTP as well as ATP. Binding of LGP2 to dsRNA promotes nucleation of MDA5 filament assembly resulting in shorter filaments. Molecular modeling identifies an internally bound MDA5-LGP2-RNA complex, with the LGP2 C-terminal tail forming the key contacts with MDA5. These contacts are specifically required for NTP-dependent internal RNA binding. We conclude that NTPase-dependent binding of LGP2 to internal dsRNA sites complements NTPase-independent binding to dsRNA ends, via distinct binding modes, to increase the number and signaling output of MDA5-dsRNA complexes.

Mechanisms of type I interferon production by chicken TLR21

The innate immune response relies on the ability of host cells to rapidly detect and respond to microbial nucleic acids. Toll-like receptors (TLRs), a class of pattern recognition receptors (PRRs), play a fundamental role in distinguishing self from non-self at the molecular level. In this study, we focused on TLR21, an avian TLR that recognizes DNA motifs commonly found in bacterial genomic DNA, specifically unmethylated CpG motifs. TLR21 is believed to act as a functional homologue to mammalian TLR9. By analysing TLR21 signalling in chickens, we sought to elucidate avian TLR21 activation outputs in parallel to that of other nucleic acid species. Our analyses revealed that chicken TLR21 (chTLR21) triggers the activation of NF-κB and induces a potent type-I interferon response in chicken macrophages, similar to the signalling cascades observed in mammalian TLR9 activation. Notably, the transcription of interferon beta (IFNB) by chTLR21 was found to be dependent on both NF-κB and IRF7 signalling, but independent of the TBK1 kinase, a distinctive feature of mammalian TLR9 signalling. These findings highlight the conservation of critical signalling components and downstream responses between avian TLR21 and mammalian TLR9, despite their divergent evolutionary origins. These insights into the evolutionarily conserved mechanisms of nucleic acid sensing contribute to the broader understanding of host-pathogen interactions across species.

DNA-PKcs is required for cGAS/STING-dependent viral DNA sensing in human cells

To mount an efficient interferon response to virus infection, intracellular pattern recognition receptors (PRRs) sense viral nucleic acids and activate anti-viral gene transcription. The mechanisms by which intracellular DNA and DNA viruses are sensed are relevant not only to anti-viral innate immunity, but also to autoinflammation and anti-tumour immunity through the initiation of sterile inflammation by self-DNA recognition. The PRRs that directly sense and respond to viral or damaged self-DNA function by signaling to activate interferon regulatory factor (IRF)-dependent type one interferon (IFN-I) transcription. We and others have previously defined DNA-dependent protein kinase (DNA-PK) as an essential component of the DNA-dependent anti-viral innate immune system. Here, we show that DNA-PK is essential for cyclic GMP-AMP synthase (cGAS)- and stimulator of interferon genes (STING)-dependent IFN-I responses in human cells during stimulation with exogenous DNA and infection with DNA viruses.

LUBAC is required for RIG-I sensing of RNA viruses

The ability of cells to mount an interferon response to virus infections depends on intracellular nucleic acid sensing pattern recognition receptors (PRRs). RIG-I is an intracellular PRR that binds short double-stranded viral RNAs to trigger MAVS-dependent signalling. The RIG-I/MAVS signalling complex requires the coordinated activity of multiple kinases and E3 ubiquitin ligases to activate the transcription factors that drive type I and type III interferon production from infected cells. The linear ubiquitin chain assembly complex (LUBAC) regulates the activity of multiple receptor signalling pathways in both ligase-dependent and -independent ways. Here, we show that the three proteins that constitute LUBAC have separate functions in regulating RIG-I signalling. Both HOIP, the E3 ligase capable of generating M1-ubiquitin chains, and LUBAC accessory protein HOIL-1 are required for viral RNA sensing by RIG-I. The third LUBAC component, SHARPIN, is not required for RIG-I signalling. These data cement the role of LUBAC as a positive regulator of RIG-I signalling and as an important component of antiviral innate immune responses.

PKR-mediated stress response enhances dengue and Zika virus replication

IMPORTANCE

One of the fundamental features that make viruses intracellular parasites is the necessity to use cellular translational machinery. Hence, this is a crucial checkpoint for controlling infections. Here, we show that dengue and Zika viruses, responsible for nearly 400 million infections every year worldwide, explore such control for optimal replication. Using immunocompetent cells, we demonstrate that arrest of protein translations happens after sensing of dsRNA and that the information required to avoid this blocking is contained in viral 5'-UTR. Our work, therefore, suggests that the non-canonical translation described for these viruses is engaged when the intracellular stress response is activated.

Transcriptional reprogramming of natural killer cells by vaccinia virus shows both distinct and conserved features with mCMV

Natural killer (NK) cells have an established role in controlling poxvirus infection and there is a growing interest to exploit their capabilities in the context of poxvirus-based oncolytic therapy and vaccination. How NK cells respond to poxvirus-infected cells to become activated is not well established. To address this knowledge gap, we studied the NK cell response to vaccinia virus (VACV) in vivo, using a systemic infection murine model. We found broad alterations in NK cells transcriptional activity in VACV-infected mice, consistent with both direct target cell recognition and cytokine exposure. There were also alterations in the expression levels of specific NK surface receptors (NKRs), including the Ly49 family and SLAM receptors, as well as upregulation of memory-associated NK markers. Despite the latter observation, adoptive transfer of VACV-expercienced NK populations did not confer protection from infection. Comparison with the NK cell response to murine cytomegalovirus (MCMV) infection highlighted common features, but also distinct NK transcriptional programmes initiated by VACV. Finally, there was a clear overlap between the NK transcriptional response in humans vaccinated with an attenuated VACV, modified vaccinia Ankara (MVA), demonstrating conservation between the NK response in these different host species. Overall, this study provides new data about NK cell activation, function, and homeostasis during VACV infection, and may have implication for the design of VACV-based therapeutics.

Suppression of innate immunity by the vaccinia virus protein N1 promotes skin microbiota expansion and increased immune infiltration following vaccination

Vaccinia virus (VACV) protein N1 is an intracellular immunomodulator that contributes to virus virulence via inhibition of NF-κB. Intradermal infection with a VACV lacking gene N1L (vΔN1) results in smaller skin lesions than infection with wild-type virus (WT VACV), but the impact of N1 deletion on the local microbiota as well as the innate and cellular immune responses in infected ear tissue is mostly uncharacterized. Here, we analysed the bacterial burden and host immune response at the site of infection and report that the presence of protein N1 correlated with enhanced expansion of skin microbiota, even before lesion development. Furthermore, early after infection (days 1-3), prior to lesion development, the levels of inflammatory mediators were higher in vΔN1-infected tissue compared to WT VACV infection. In contrast, infiltration of ear tissue with myeloid and lymphoid cells was greater after WT VACV infection and there was significantly greater secondary bacterial infection that correlated with greater lesion size. We conclude that a more robust innate immune response to vΔN1 infection leads to better control of virus replication, less bacterial growth and hence an overall reduction of tissue damage and lesion size. This analysis shows the potent impact of a single viral immunomodulator on the host immune response and the pathophysiology of VACV infection in the skin.

Selective modulation of cell surface proteins during vaccinia infection: A resource for identifying viral immune evasion strategies

The interaction between immune cells and virus-infected targets involves multiple plasma membrane (PM) proteins. A systematic study of PM protein modulation by vaccinia virus (VACV), the paradigm of host regulation, has the potential to reveal not only novel viral immune evasion mechanisms, but also novel factors critical in host immunity. Here, >1000 PM proteins were quantified throughout VACV infection, revealing selective downregulation of known T and NK cell ligands including HLA-C, downregulation of cytokine receptors including IFNAR2, IL-6ST and IL-10RB, and rapid inhibition of expression of certain protocadherins and ephrins, candidate activating immune ligands. Downregulation of most PM proteins occurred via a proteasome-independent mechanism. Upregulated proteins included a decoy receptor for TRAIL. Twenty VACV-encoded PM proteins were identified, of which five were not recognised previously as such. Collectively, this dataset constitutes a valuable resource for future studies on antiviral immunity, host-pathogen interaction, poxvirus biology, vector-based vaccine design and oncolytic therapy.

Vaccinia virus (VACV) is the vaccine used to eradicate smallpox and an excellent model for studying host-pathogen interactions. Many VACV-mediated immune evasion strategies are known, however how immune cells recognise VACV-infected cells is incompletely understood because of the complexity of surface proteins regulating such interactions. Here, a systematic study of proteins on the cell surface at different times during infection with VACV is presented. This shows not only the precise nature and kinetics of appearance of VACV proteins, but also the selective alteration of cellular surface proteins. The latter thereby identified potential novel immune evasion strategies and host proteins regulating immune activation. Comprehensive comparisons with published datasets provided further insight into mechanisms used to regulate surface protein expression. Such comparisons also identified proteins that are targeted by both VACV and human cytomegalovirus (HCMV), and which are therefore likely to represent host proteins regulating immune recognition and activation. Collectively, this work provides a valuable resource for studying viral immune evasion mechanisms and novel host proteins critical in host immunity.

Smallpox vaccination induces a substantial increase in commensal skin bacteria that promote pathology and influence the host response

Interactions between pathogens, host microbiota and the immune system influence many physiological and pathological processes. In the 20th century, widespread dermal vaccination with vaccinia virus (VACV) led to the eradication of smallpox but how VACV interacts with the microbiota and whether this influences the efficacy of vaccination are largely unknown. Here we report that intradermal vaccination with VACV induces a large increase in the number of commensal bacteria in infected tissue, which enhance recruitment of inflammatory cells, promote tissue damage and influence the host response. Treatment of vaccinated specific-pathogen-free (SPF) mice with antibiotic, or infection of genetically-matched germ-free (GF) animals caused smaller lesions without alteration in virus titre. Tissue damage correlated with enhanced neutrophil and T cell infiltration and levels of pro-inflammatory tissue cytokines and chemokines. One month after vaccination, GF and both groups of SPF mice had equal numbers of VACV-specific CD8+ T cells and were protected from disease induced by VACV challenge, despite lower levels of VACV-neutralising antibodies observed in GF animals. Thus, skin microbiota may provide an adjuvant-like stimulus during vaccination with VACV and influence the host response to vaccination.

DNA-PK senses DNA virus infection in human cells

The type I interferon (IFN-I) response to virus infection is initiated by the detection of nucleic acids by intracellular pattern recognition receptors (PRRs). The sensing of DNA viruses by PRRs is carried out by a number of DNA-binding PRRs that signal via the adaptor protein stimulator of interferon genes (STING) to drive IFN-I transcription. We previously described the role of DNA-dependent protein kinase (DNA-PK) as a viral DNA sensor in murine fibroblasts. In this study we show that DNA-PK is essential for the host response to DNA and DNA viruses in human fibroblasts. In the absensce of the catalytic subunit of the DNA-PK heterotrimer, DNA-PKcs, fibroblasts are deficient in their ability to activate a IFN-I response to DNA. DNA-PKcs is activated rapidly following exogenous DNA transfection or DNA virus infection and is required for signalling via STING and the kinase TBK-1 to the transcription factor interferon regulator factor 3 (IRF-3). Most wild-type DNA viruses combat intracellular DNA PRRs using immunomodulatory proteins encoded in their genomes and are effective at blocking IFN-I responses in infected cells. Here we make use of attenutated vaccina and herpes simplex 1 viruses that are lacking the immunomodulators that target DNA sesining mechanisms. We show that DNA-PKcs can sense these viruses and is required for triggering the IFN-I response in infected cells. These data cement the role of DNA-PK in the sensing of DNA virus infections in human cells.

Exploiting Connections for Viral Replication

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the COVID-19 (coronavirus disease 2019) pandemic, is a positive strand RNA (+RNA) virus. Like other +RNA viruses, SARS-CoV-2 is dependent on host cell metabolic machinery to survive and replicate, remodeling cellular membranes to generate sites of viral replication. Viral RNA-containing double-membrane vesicles (DMVs) are a striking feature of +RNA viral replication and are abundant in SARS-CoV-2-infected cells. Their generation involves rewiring of host lipid metabolism, including lipid biosynthetic pathways. Viruses can also redirect lipids from host cell organelles; lipid exchange at membrane contact sites, where the membranes of adjacent organelles are in close apposition, has been implicated in the replication of several +RNA viruses. Here we review current understanding of DMV biogenesis. With a focus on the exploitation of contact site machinery by +RNA viruses to generate replication organelles, we discuss evidence that similar mechanisms support SARS-CoV-2 replication, protecting its RNA from the host cell immune response.

Vaccinia Virus Infection Inhibits Skin Dendritic Cell Migration to the Draining Lymph Node

There is a paucity of information on dendritic cell (DC) responses to vaccinia virus (VACV), including the traffic of DCs to the draining lymph node (dLN). In this study, using a mouse model of infection, we studied skin DC migration in response to VACV and compared it with the tuberculosis vaccine Mycobacterium bovis bacille Calmette-Guérin (BCG), another live attenuated vaccine administered via the skin. In stark contrast to BCG, skin DCs did not relocate to the dLN in response to VACV. Infection with UV-inactivated VACV or modified VACV Ankara promoted DC movement to the dLN, indicating that interference with skin DC migration requires replication-competent VACV. This suppressive effect of VACV was capable of mitigating responses to a secondary challenge with BCG in the skin, ablating DC migration, reducing BCG transport, and delaying CD4+ T cell priming in the dLN. Expression of inflammatory mediators associated with BCG-triggered DC migration were absent from virus-injected skin, suggesting that other pathways invoke DC movement in response to replication-deficient VACV. Despite adamant suppression of DC migration, VACV was still detected early in the dLN and primed Ag-specific CD4+ T cells. In summary, VACV blocks skin DC mobilization from the site of infection while retaining the ability to access the dLN to prime CD4+ T cells.

Chicken cGAS Senses Fowlpox Virus Infection and Regulates Macrophage Effector Functions

The anti-viral immune response is dependent on the ability of infected cells to sense foreign nucleic acids. In multiple species, the pattern recognition receptor (PRR) cyclic GMP-AMP synthase (cGAS) senses viral DNA as an essential component of the innate response. cGAS initiates a range of signaling outputs that are dependent on generation of the second messenger cGAMP that binds to the adaptor protein stimulator of interferon genes (STING). Here we show that in chicken macrophages, the cGAS/STING pathway is essential not only for the production of type-I interferons in response to intracellular DNA stimulation, but also for regulation of macrophage effector functions including the expression of MHC-II and co-stimulatory molecules. In the context of fowlpox, an avian DNA virus infection, the cGAS/STING pathway was found to be responsible for type-I interferon production and MHC-II transcription. The sensing of fowlpox virus DNA is therefore essential for mounting an anti-viral response in chicken cells and for regulation of a specific set of macrophage effector functions.

Viral interactions with non-homologous end-joining: a game of hide-and-seek

There are extensive interactions between viruses and the host DNA damage response (DDR) machinery. The outcome of these interactions includes not only direct effects on viral nucleic acids and genome replication, but also the activation of host stress response signalling pathways that can have further, indirect effects on viral life cycles. The non-homologous end-joining (NHEJ) pathway is responsible for the rapid and imprecise repair of DNA double-stranded breaks in the nucleus that would otherwise be highly toxic. Whilst directly repairing DNA, components of the NHEJ machinery, in particular the DNA-dependent protein kinase (DNA-PK), can activate a raft of downstream signalling events that activate antiviral, cell cycle checkpoint and apoptosis pathways. This combination of possible outcomes results in NHEJ being pro- or antiviral depending on the infection. In this review we will describe the broad range of interactions between NHEJ components and viruses and their consequences for both host and pathogen.

Temporal analysis of the plasma membrane proteome after vaccinia virus infection sheds light on virus strategies to evade the immune response

Vaccinia virus (VACV) is a poxvirus and the vaccine used to protect against variola virus and related orthopoxviruses. VACV encodes multiple proteins whose function is to evade the host immune response, contributing to an immune suppressive environment at the site of infection. There is, however, an incomplete understanding of how this immune suppression by VACV is consistent with a strong induction of immunological memory. There is especially little known about the relationship between NK cells and VACV, such as which ligands trigger NK activation and whether VACV uses strategies to interfere with the NK cell response. The purposes of this study is to clarify these open questions.

Here, we performed a quantitative proteomic analysis of membrane-associated proteins from VACV-infected cells at various time points. Using tandem mass-tag spectrometry we detected about 70 viral proteins and 900 membrane-associated host proteins. Analysis revealed that VACV infection rapidly altered the expression of proteins with immune functions, downregulated the surface expression of plexins, ephrins, cadherins and selectively downregulated MHC-I proteins. Moreover, VACV prevented the upregulation of stress-induced ligands and death receptors. Finally, the kinetics of expression of VACV proteins at the surface of the infected cell were analysed.

Collectively, these data constitute a valuable resource for the study of VACV and its interaction with the host immune response, provide insights into the interaction of NK cells with VACV, suggest novel VACV immune evasion mechanisms and shed light on which host factors are required to raise a protective immunological memory.

Enhanced Efficacy of Vaccination With Vaccinia Virus in Old vs. Young Mice

Immunosenescence is believed to be responsible for poor vaccine efficacy in the elderly. To overcome this difficulty, research into vaccination strategies and the mechanisms of immune responses to vaccination is required. By analyzing the innate and adaptive immune responses to vaccination with vaccinia virus (VACV) in mice of different age groups, we found that immune cell recruitment, production of cytokines/chemokines and control of viral replication at the site of intradermal vaccination were preserved in aged mice and were comparable with younger groups. Analysis of cervical draining lymph nodes (dLN) collected after vaccination showed that numbers of germinal center B cells and follicular T helper cells were similar across different age groups. The number of VACV-specific CD8 T cells in the spleen and the levels of serum neutralizing antibodies 1 month after vaccination were also comparable across all age groups. However, following intranasal challenge of vaccinated mice, body weight loss was lower and virus was cleared more rapidly in aged mice than in younger animals. In conclusion, vaccination with VACV can induce an effective immune response and stronger protection in elderly animals. Thus, the development of recombinant VACV-based vaccines against different infectious diseases should be considered as a strategy for improving vaccine immunogenicity and efficacy in the elderly.

ISG15-Induced IL-10 Is a Novel Anti-Inflammatory Myeloid Axis Disrupted during Active Tuberculosis

IFN-stimulated gene 15 (ISG15) deficiency in humans leads to severe IFNopathies and mycobacterial disease, the latter being previously attributed to its extracellular cytokine-like activity. In this study, we demonstrate a novel role for secreted ISG15 as an IL-10 inducer, unique to primary human monocytes. A balanced ISG15-induced monocyte/IL-10 versus lymphoid/IFN-γ expression, correlating with p38 MAPK and PI3K signaling, was found using targeted in vitro and ex vivo systems analysis of human transcriptomic datasets. The specificity and MAPK/PI3K-dependence of ISG15-induced monocyte IL-10 production was confirmed in vitro using CRISPR/Cas9 knockout and pharmacological inhibitors. Moreover, this ISG15/IL-10 axis was amplified in leprosy but disrupted in human active tuberculosis (TB) patients. Importantly, ISG15 strongly correlated with inflammation and disease severity during active TB, suggesting its potential use as a biomarker, awaiting clinical validation. In conclusion, this study identifies a novel anti-inflammatory ISG15/IL-10 myeloid axis that is disrupted in active TB.

The Non-Homologous End Joining Protein PAXX Acts to Restrict HSV-1 Infection

Herpes simplex virus 1 (HSV-1) has extensive interactions with the host DNA damage response (DDR) machinery that can be either detrimental or beneficial to the virus. Proteins in the homologous recombination pathway are known to be required for efficient replication of the viral genome, while different members of the classical non-homologous end-joining (c-NHEJ) pathway have opposing effects on HSV-1 infection. Here, we have investigated the role of the recently-discovered c-NHEJ component, PAXX (Paralogue of XRCC4 and XLF), which we found to be excluded from the nucleus during HSV-1 infection. We have established that cells lacking PAXX have an intact innate immune response to HSV-1 but show a defect in viral genome replication efficiency. Counterintuitively, PAXX-/- cells were able to produce greater numbers of infectious virions, indicating that PAXX acts to restrict HSV-1 infection in a manner that is different from other c-NHEJ factors.

SCUAD and chronic rhinosinusitis. Reinforcing hypothesis driven research in difficult cases

BACKGROUND

Our objective is to present recent research findings on recalcitrant chronic rhinosinusitis (CRS) in relation to "Severe Chronic Upper Airway Disease" (SCUAD).

METHODOLOGY

Literature review using Medline and Em base databases (search terms 'chronic rhinosinusitis'; "chronic sinusitis" or"Severe Chronic Upper Airway Disease") limited to articles published in the English language.

RESULTS

Complex pathophysiological mechanisms characterize various forms of chronic rhinitis and rhinosinusitis (CRS), where inflammation persists in spite of adequate medical treatment. In these cases, a multifactorial etiology often underlies the development of sino-nasal inflammation. The interaction between chronic upper and lower airway inflammation via neurogenic and systemic pathways may complicate the therapy of these patients, and lead to insufficient symptom control.

CONCLUSION

The recently introduced definition of"Severe Chronic Upper Airway Disease" (SCUAD) increases awareness of those patients with persistent inflammation and symptoms despite guideline-driven pharmacologic treatment. The concept of SCUAD may prove helpful in directing research towards clarifying the definition, diagnosis and pathophysiology of rhinitis and rhinosinusitis,their limits and overlap. In this review, a hypothesis on SCUAD immunopathology is also presented.

Genome-wide analyses reveal a highly conserved Dengue virus envelope peptide which is critical for virus viability and antigenic in humans

Targeting regions of proteins that show a high degree of structural conservation has been proposed as a method of developing immunotherapies and vaccines that may bypass the wide genetic variability of RNA viruses. Despite several attempts, a vaccine that protects evenly against the four circulating Dengue virus (DV) serotypes remains elusive. To find critical conserved amino acids in dengue viruses, 120 complete genomes of each serotype were selected at random and used to calculate conservation scores for nucleotide and amino acid sequences. The identified peptide sequences were analysed for their structural conservation and localisation using crystallographic data. The longest, surface exposed, highly conserved peptide of Envelope protein was found to correspond to amino acid residues 250 to 270. Mutation of this peptide in DV1 was lethal, since no replication of the mutant virus was detected in human cells. Antibodies against this peptide were detected in DV naturally infected patients indicating its potential antigenicity. Hence, this study has identified a highly conserved, critical peptide in DV that is a target of antibodies in infected humans.

--LUBAC deficiency perturbs TLR3 signaling to cause immunodeficiency and autoinflammation

LUBAC components interact with the TLR3 signaling cascade at different levels, thereby tightly controlling TLR3-mediated innate immunity.

The linear ubiquitin chain assembly complex (LUBAC), consisting of SHANK-associated RH-domain–interacting protein (SHARPIN), heme-oxidized IRP2 ubiquitin ligase-1 (HOIL-1), and HOIL-1–interacting protein (HOIP), is a critical regulator of inflammation and immunity. This is highlighted by the fact that patients with perturbed linear ubiquitination caused by mutations in the Hoip or Hoil-1 genes, resulting in knockouts of these proteins, may simultaneously suffer from immunodeficiency and autoinflammation. TLR3 plays a crucial, albeit controversial, role in viral infection and tissue damage. We identify a pivotal role of LUBAC in TLR3 signaling and discover a functional interaction between LUBAC components and TLR3 as crucial for immunity to influenza A virus infection. On the biochemical level, we identify LUBAC components as interacting with the TLR3-signaling complex (SC), thereby enabling TLR3-mediated gene activation. Absence of LUBAC components increases formation of a previously unrecognized TLR3-induced death-inducing SC, leading to enhanced cell death. Intriguingly, excessive TLR3-mediated cell death, induced by double-stranded RNA present in the skin of SHARPIN-deficient chronic proliferative dermatitis mice (cpdm), is a major contributor to their autoinflammatory skin phenotype, as genetic coablation of Tlr3 substantially ameliorated cpdm dermatitis. Thus, LUBAC components control TLR3-mediated innate immunity, thereby preventing development of immunodeficiency and autoinflammation.

The Schistosoma mansoni T2 ribonuclease omega-1 modulates inflammasome-dependent IL-1β secretion in macrophages

The T2 ribonuclease omega-1 is a powerful Th2-inducing factor secreted by the eggs of the blood fluke Schistosoma mansoni. Omega-1 can modulate pattern recognition receptor-induced inflammatory signatures and alter antigen presentation by dendritic cells. Recent findings have suggested that component(s) contained in or secreted by S. mansoni eggs (soluble egg antigen) can also enhance IL-1β secretion by dendritic cells stimulated with pattern recognition receptor ligands. Here we show that omega-1 enhances IL-1β secretion in macrophages stimulated with Toll-like receptor 2 ligand, and propose omega-1 as the factor in soluble egg antigen capable of regulating inflammasome activity. This effect is dependent on the C-type lectin receptor Dectin-1, caspase-8 and the ASC inflammasome adaptor protein, highlighting the ability of omega-1 to regulate multiple pattern recognition receptor signalling pathways. These mechanistic insights into manipulation of host immunity by a parasite product have implications for the design of anti-inflammatory therapeutic drugs.

The role of shed placental DNA in the systemic inflammatory syndrome of preeclampsia

Preeclampsia is a syndrome occurring only in pregnancy characterized by systemic maternal inflammation and associated with the presence of the placenta. How these 2 aspects of the disease are linked has been the subject of numerous theories and ideas. Recently, there has been increasing interest in DNA shed from the placenta into the maternal circulation as a potential agent initiating the inflammatory response. This review will discuss the current evidence and future directions for placental DNA as the linking factor in preeclampsia in the context of other hypotheses.

Enhancement of CD8(+) T-cell memory by removal of a vaccinia virus nuclear factor-κB inhibitor

Factors influencing T-cell responses are important for vaccine development but are incompletely understood. Here, vaccinia virus (VACV) protein N1 is shown to impair the development of both effector and memory CD8⁺ T cells and this correlates with its inhibition of nuclear factor-κB (NF-κB) activation. Infection with VACVs that either have the N1L gene deleted (vΔN1) or contain a I6E mutation (vN1.I6E) that abrogates its inhibition of NF-κB resulted in increased central and memory CD8⁺ T-cell populations, increased CD8⁺ T-cell cytotoxicity and lower virus titres after challenge. Furthermore, CD8⁺ memory T-cell function was increased following infection with vN1.I6E, with more interferon-γ production and greater protection against VACV infection following passive transfer to naive mice, compared with CD8⁺ T cells from mice infected with wild-type virus (vN1.WT). This demonstrates the importance of NF-κB activation within infected cells for long-term CD8⁺ T-cell memory and vaccine efficacy. Further, it provides a rationale for deleting N1 from VACV vectors to enhance CD8⁺ T-cell immunogenicity, while simultaneously reducing virulence to improve vaccine safety.

Stimulation of cytoplasmic DNA sensing pathways in vitro and in vivo

In order to efficiently stimulate an innate immune response, DNA must be of sufficient length and purity. We present a method where double stranded DNA (dsDNA) which has the requisite characteristics to stimulate the cytoplasmic DNA sensing pathways can be generated cheaply and with ease. By the concatemerization of short, synthetic oligonucleotides (which lack CpG motifs), dsDNA can be generated to be of sufficient length to activate the cytosolic DNA sensing pathway. This protocol involves blunt end ligation of the oligonucleotides in the presence of polyethylene glycol (PEG), which provides an environment for efficient ligation to occur. The dsDNA concatemers can be used, following purification by phenol/chloroform extraction, to simulate the innate immune response in vitro by standard transfection protocols. This DNA can also be used to stimulate innate immunity in vivo by intradermal injection into the ear pinna of a mouse, for example. By standardizing the concatemerization process and the subsequent stimulation protocols, a reliable and reproducible activation of the innate immune system can be produced.

A mechanism for the inhibition of DNA-PK-mediated DNA sensing by a virus

The innate immune system is critical in the response to infection by pathogens and it is activated by pattern recognition receptors (PRRs) binding to pathogen associated molecular patterns (PAMPs). During viral infection, the direct recognition of the viral nucleic acids, such as the genomes of DNA viruses, is very important for activation of innate immunity. Recently, DNA-dependent protein kinase (DNA-PK), a heterotrimeric complex consisting of the Ku70/Ku80 heterodimer and the catalytic subunit DNA-PKcs was identified as a cytoplasmic PRR for DNA that is important for the innate immune response to intracellular DNA and DNA virus infection. Here we show that vaccinia virus (VACV) has evolved to inhibit this function of DNA-PK by expression of a highly conserved protein called C16, which was known to contribute to virulence but by an unknown mechanism. Data presented show that C16 binds directly to the Ku heterodimer and thereby inhibits the innate immune response to DNA in fibroblasts, characterised by the decreased production of cytokines and chemokines. Mechanistically, C16 acts by blocking DNA-PK binding to DNA, which correlates with reduced DNA-PK-dependent DNA sensing. The C-terminal region of C16 is sufficient for binding Ku and this activity is conserved in the variola virus (VARV) orthologue of C16. In contrast, deletion of 5 amino acids in this domain is enough to knockout this function from the attenuated vaccine strain modified vaccinia virus Ankara (MVA). In vivo a VACV mutant lacking C16 induced higher levels of cytokines and chemokines early after infection compared to control viruses, confirming the role of this virulence factor in attenuating the innate immune response. Overall this study describes the inhibition of DNA-PK-dependent DNA sensing by a poxvirus protein, adding to the evidence that DNA-PK is a critical component of innate immunity to DNA viruses.

Vaccinia virus immune evasion: mechanisms, virulence and immunogenicity

Virus infection of mammalian cells is sensed by pattern recognition receptors and leads to an innate immune response that restricts virus replication and induces adaptive immunity. In response, viruses have evolved many countermeasures that enable them to replicate and be transmitted to new hosts, despite the host innate immune response. Poxviruses, such as vaccinia virus (VACV), have large DNA genomes and encode many proteins that are dedicated to host immune evasion. Some of these proteins are secreted from the infected cell, where they bind and neutralize complement factors, interferons, cytokines and chemokines. Other VACV proteins function inside cells to inhibit apoptosis or signalling pathways that lead to the production of interferons and pro-inflammatory cytokines and chemokines. In this review, these VACV immunomodulatory proteins are described and the potential to create more immunogenic VACV strains by manipulation of the gene encoding these proteins is discussed.

Vaccinia virus protein N2 is a nuclear IRF3 inhibitor that promotes virulence

Vaccinia virus (VACV) expresses many proteins that are non-essential for virus replication but promote virulence by inhibiting components of the host immune response to infection. These immunomodulators include a family of proteins that have, or are predicted to have, a structure related to the B-cell lymphoma (Bcl)-2 protein. Five members of the VACV Bcl-2 family (N1, B14, A52, F1 and K7) have had their crystal structure solved, others have been characterized and a function assigned (C6, A46), and others are predicted to be Bcl-2 proteins but are uncharacterized hitherto (N2, B22, C1). Data presented here show that N2 is a nuclear protein that is expressed early during infection and inhibits the activation of interferon regulatory factor (IRF)3. Consistent with its nuclear localization, N2 inhibits IRF3 downstream of the TANK-binding kinase (TBK)-1 and after IRF3 translocation into the nucleus. A mutant VACV strain Western Reserve lacking the N2L gene (vΔN2) showed normal replication and spread in cultured cells compared to wild-type parental (vN2) and revertant (vN2-rev) viruses, but was attenuated in two murine models of infection. After intranasal infection, the vΔN2 mutant induced lower weight loss and signs of illness, and virus was cleared more rapidly from the infected tissue. In the intradermal model of infection, vΔN2 induced smaller lesions that were resolved more rapidly. In summary, the N2 protein is an intracellular virulence factor that inhibits IRF3 activity in the nucleus.

Poxvirus targeting of E3 ligase β-TrCP by molecular mimicry: a mechanism to inhibit NF-κB activation and promote immune evasion and virulence

The transcription factor NF-κB is essential for immune responses against pathogens and its activation requires the phosphorylation, ubiquitination and proteasomal degradation of IκBα. Here we describe an inhibitor of NF-κB from vaccinia virus that has a closely related counterpart in variola virus, the cause of smallpox, and mechanistic similarity with the HIV protein Vpu. Protein A49 blocks NF-κB activation by molecular mimicry and contains a motif conserved in IκBα which, in IκBα, is phosphorylated by IKKβ causing ubiquitination and degradation. Like IκBα, A49 binds the E3 ligase β-TrCP, thereby preventing ubiquitination and degradation of IκBα. Consequently, A49 stabilised phosphorylated IκBα (p-IκBα) and its interaction with p65, so preventing p65 nuclear translocation. Serine-to-alanine mutagenesis within the IκBα-like motif of A49 abolished β-TrCP binding, stabilisation of p-IκBα and inhibition of NF-κB activation. Remarkably, despite encoding nine other inhibitors of NF-κB, a VACV lacking A49 showed reduced virulence in vivo.

The host response to infection provides a powerful means of restricting the replication and spread of viruses. Consequently, viruses have evolved mechanisms to reduce activation of host response to infection and this paper provides an example of this. Nuclear factor kappa B (NF-κB) is an important transcription factor that activates the host response to infection and is normally retained in an inactive form in the cytoplasm bound to an inhibitor called IκBα. However, upon stimulation by infection, IκBα is degraded and NF-κB moves to the nucleus to activate expression of genes mediating the host response. Here we describe how protein A49 from vaccinia virus, the vaccine used to eradicate smallpox, mimics IκBα to hijack the cellular degradation machinery and so stabilise IκBα and retain NF-κB in the cytoplasm. The importance of A49 is demonstrated by the fact that a virus lacking A49 was less virulent than control viruses, despite the expression of several other NF-κB inhibitors by vaccinia virus. Interestingly, HIV protein Vpu functions in a similar way to A49 and, given that A49 is highly conserved in variola virus, this work reveals a common strategy for suppression of host innate immunity by the viruses that cause smallpox and AIDS.

DNA-PK is a DNA sensor for IRF-3-dependent innate immunity

Innate immunity is the first immunological defence against pathogens. During virus infection detection of nucleic acids is crucial for the inflammatory response. Here we identify DNA-dependent protein kinase (DNA-PK) as a DNA sensor that activates innate immunity. We show that DNA-PK acts as a pattern recognition receptor, binding cytoplasmic DNA and triggering the transcription of type I interferon (IFN), cytokine and chemokine genes in a manner dependent on IFN regulatory factor 3 (IRF-3), TANK-binding kinase 1 (TBK1) and stimulator of interferon genes (STING). Both cells and mice lacking DNA-PKcs show attenuated cytokine responses to both DNA and DNA viruses but not to RNA or RNA virus infection. DNA-PK has well-established functions in the DNA repair and V(D)J recombination, hence loss of DNA-PK leads to severe combined immunodeficiency (SCID). However, we now define a novel anti-microbial function for DNA-PK, a finding with implications for host defence, vaccine development and autoimmunity.

DOI:http://dx.doi.org/10.7554/eLife.00047.001

For multicellular organisms, the innate immune system is the first immunological defence against infection, rapidly recognizing and responding to the presence of any pathogen. Many different cell types contribute to the innate immunity, including fibroblasts, epithelial cells, dendritic cells and macrophages. Once alerted to injury or infection, these cells release proteins called cytokines, interferons and chemokines into the blood or directly into tissue. These proteins act as messengers and interact with receptors on the surfaces of other cells in the immune system, stimulating them to join the battle against the infection.

Detecting nucleic acids such as DNA is an important part of recognizing pathogens and infectious agents, particularly viruses, and activating the innate immune system. However, while the presence of DNA in the cytoplasm is known to initiate an innate immune response, we do not fully understand how this foreign DNA is sensed, or how the innate immune system is activated once foreign DNA has been detected.

Here Ferguson et al. report that a well-known complex of three proteins, collectively called DNA-dependent protein kinase, is able to activate an innate immune response when it detects foreign DNA. This enzyme, called DNA-PK for short, is best known for its ability to repair broken DNA inside the nucleus. Now Ferguson et al. have found that it is also present at high levels within fibroblasts, cells that are often primary targets of viral infection, and they go on to explain how the detection of DNA by DNA-PK triggers a sequence of events that leads to the innate immune response being activated. These events include the transcription of type I interferon, chemokines and cytokines in a manner that depends on the presence IRF-3, a transcription factor that has a central role in the response of the immune system to viral infection.

By identifying a role for DNA-PK in the cytoplasm as a DNA sensor, the work of Ferguson et al. increases our understanding of innate immunity. It may also, in the future, lead to an improved understanding of autoimmunity, and might also assist in the development of more immunogenic vaccines based on DNA or microbes that contain DNA.

DOI:http://dx.doi.org/10.7554/eLife.00047.002

Vaccinia virus protein C4 inhibits NF-κB activation and promotes virus virulence

Vaccinia virus (VACV) strain Western Reserve protein C4 has been characterized and its function and contribution to virus virulence assessed. Bioinformatic analysis showed that C4 is conserved in six orthopoxvirus species and shares 43 % amino acid identity with VACV protein C16, a known virulence factor. A recombinant VACV expressing a C-terminally tagged version of C4 showed that, like C16, this 37 kDa protein is expressed early during infection and localizes to both the cytoplasm and the nucleus. Functional assays using a firefly luciferase reporter plasmid under the control of a nuclear factor kappa B (NF-κB)-dependent promoter demonstrated that C4 inhibits NF-κB activation at, or downstream of, the inhibitor of kappa kinase (IKK) complex. Consistent with this, C4 inhibited interleukin-1β-induced translocation of p65 into the nucleus. A VACV lacking the C4L gene (vΔC4) showed no significant differences from wild-type virus in growth kinetics or spread in cell culture, but had reduced virulence in a murine intranasal model of infection. vΔC4-infected mice exhibited fewer symptoms, lost less weight and recovered 7 days earlier than animals infected with control viruses expressing C4. Furthermore, bronchoalveolar lavage fluid from vΔC4-infected mice had increased cell numbers at day 5 post-infection, which correlated with reduced lung virus titres from this time onward. C4 represents the ninth VACV protein to inhibit NF-κB activation and remarkably, in every case examined, loss of each protein individually caused an alteration in virus virulence, despite the presence of other NF-κB inhibitors.

Mapping the IkappaB kinase beta (IKKbeta)-binding interface of the B14 protein, a vaccinia virus inhibitor of IKKbeta-mediated activation of nuclear factor kappaB

The IκB kinase (IKK) complex regulates activation of NF-κB, a critical transcription factor in mediating inflammatory and immune responses. Not surprisingly, therefore, many viruses seek to inhibit NF-κB activation. The vaccinia virus B14 protein contributes to virus virulence by binding to the IKKβ subunit of the IKK complex and preventing NF-κB activation in response to pro-inflammatory stimuli. Previous crystallographic studies showed that the B14 protein has a Bcl-2-like fold and forms homodimers in the crystal. However, multi-angle light scattering indicated that B14 is in monomer-dimer equilibrium in solution. This transient self-association suggested that the hydrophobic dimerization interface of B14 might also mediate its interaction with IKKβ, and this was investigated by introducing amino acid substitutions on the dimer interface. One mutant (Y35E) was entirely monomeric but still co-immunoprecipitated with IKKβ and blocked both NF-κB nuclear translocation and NF-κB-dependent gene expression. Therefore, B14 homodimerization is nonessential for binding and inhibition of IKKβ. In contrast, a second monomeric mutant (F130K) neither bound IKKβ nor inhibited NF-κB-dependent gene expression, demonstrating that this residue is required for the B14-IKKβ interaction. Thus, the dimerization and IKKβ-binding interfaces overlap and lie on a surface used for protein-protein interactions in many viral and cellular Bcl-2-like proteins.

Vaccinia protein F12 has structural similarity to kinesin light chain and contains a motor binding motif required for virion export

Vaccinia virus (VACV) uses microtubules for export of virions to the cell surface and this process requires the viral protein F12. Here we show that F12 has structural similarity to kinesin light chain (KLC), a subunit of the kinesin-1 motor that binds cargo. F12 and KLC share similar size, pI, hydropathy and cargo-binding tetratricopeptide repeats (TPRs). Moreover, molecular modeling of F12 TPRs upon the crystal structure of KLC2 TPRs showed a striking conservation of structure. We also identified multiple TPRs in VACV proteins E2 and A36. Data presented demonstrate that F12 is critical for recruitment of kinesin-1 to virions and that a conserved tryptophan and aspartic acid (WD) motif, which is conserved in the kinesin-1-binding sequence (KBS) of the neuronal protein calsyntenin/alcadein and several other cellular kinesin-1 binding proteins, is essential for kinesin-1 recruitment and virion transport. In contrast, mutation of WD motifs in protein A36 revealed they were not required for kinesin-1 recruitment or IEV transport. This report of a viral KLC-like protein containing a KBS that is conserved in several cellular proteins advances our understanding of how VACV recruits the kinesin motor to virions, and exemplifies how viruses use molecular mimicry of cellular components to their advantage.

Vaccinia virus (VACV), the vaccine used to eradicate smallpox, exploits the host cell motor kinesin-1 to export virus particles to the cell surface. We demonstrate that the VACV F12 protein has structural similarity with kinesin light chain (KLC) and facilitates viral transport using a kinesin binding sequence (KBS) that is conserved in several neuronal proteins. Dysfunction of some of these neuronal proteins can contribute to diseases, such as Alzheimer's. Mutation of the KBS in protein F12 showed it is essential for kinesin recruitment to virions and for virion transport to the cell surface. These findings enhance our understanding of how viruses hijack the host cell transport system, demonstrate conservation of a kinesin binding motif in cellular and viral proteins and identify targets for drug development.

PML depletion disrupts normal mammary gland development and skews the composition of the mammary luminal cell progenitor pool

Nuclear domains of promyelocytic leukemia protein (PML) are known to act as signaling nodes in many cellular processes. Although the impact of PML expression in driving cell fate decisions for injured cells is well established, the function of PML in the context of tissue development is less well understood. Here, the in vivo role of PML in developmental processes in the murine mammary gland has been investigated. Data are presented showing that expression of PML is tightly regulated by three members of the Stat family of transcription factors that orchestrate the functional development of the mammary secretory epithelium during pregnancy. Developmental phenotypes were also discovered in the virgin and pregnant Pml null mouse, typified by aberrant differentiation of mammary epithelia with reduced ductal and alveolar development. PML depletion was also found to disturb the balance of two distinct luminal progenitor populations. Overall, it is shown that PML is required for cell lineage determination in bi-potent luminal progenitor cells and that the precise regulation of PML expression is required for functional differentiation of alveolar cells.

New insights into the role of PML in tumour suppression

The PML gene is involved in the t(15;17) translocation of acute promyelocytic leukaemia (APL), which generates the oncogenic fusion protein PML (promyelocytic leukaemia protein)-retinoic acid receptor alpha. The PML protein localises to a subnuclear structure called the PML nuclear domain (PML-ND), of which PML is the essential structural component. In APL, PML-NDs are disrupted, thus implicating these structures in the pathogenesis of this leukaemia. Unexpectedly, recent studies indicate that PML and the PML-ND play a tumour suppressive role in several different types of human neoplasms in addition to APL. Because of PML's extreme versatility and involvement in multiple cellular pathways, understanding the mechanisms underlying its function, and therefore role in tumour suppression, has been a challenging task. In this review, we attempt to critically appraise the more recent advances in this field and propose new avenues of investigation.

Death in the AIRE

When thymic epithelia begin to synthesize peripheral tissue antigens such as insulin, we are seeing the result of autoimmune regulator (AIRE) activity and the workings of central tolerance. AIRE is an extraordinary protein that repatterns the transcriptome of medullary thymic epithelia (mTECs) to produce a stroma decorated with peripheral self-peptides. These peptidic arrays are used to purge self-reactive T cells, thereby averting autoimmunity. We now propose that an inherently cytotoxic event such as global chromatin modification paves the way for AIRE action. This injury stimulus might impose temporal restrictions for the T-cell education process and is endured, at least transiently, by the unique cellular environment provided by the medullary thymic epithelia.

AIRE's CARD revealed, a new structure for central tolerance provokes transcriptional plasticity

Developing T cells encounter peripheral self-antigens in the thymus in order to delete autoreactive clones. It is now known that the autoimmune regulator protein (AIRE), which is expressed in thymic medullary epithelial cells, plays a key role in regulating the thymic transcription of these peripheral tissue-specific antigens. Mutations in the AIRE gene are associated with a severe multiorgan autoimmune syndrome (APECED), and autoimmune reactivities are manifest in AIRE-deficient mice. Functional AIRE protein is expressed as distinct nuclear puncta, although no structural basis existed to explain their relevance to disease. In addressing the cell biologic basis for APECED, we made the unexpected discovery that an AIRE mutation hot spot lies in a caspase recruitment domain. Combined homology modeling and in vitro data now show how APECED mutations influence the activity of this transcriptional regulator. We also provide novel in vivo evidence for AIRE's association with a global transcription cofactor, which may underlie AIRE's focal, genome-wide, alteration of the transcriptome.

Nuclear Phospholipase C Gamma: Punctate Distribution and Association with the Promyelocytic Leukemia Protein

The marriage between transducers of cell stress stimuli and their nuclear targets is likely to be achieved in part by some spatial-temporal compartmentalization of the relevant effectors. A candidate compartment for these events is the promyelocytic leukemia nuclear domain (PML-ND), within which are found numerous effectors of damage recognition, repair, and cell death. We predicted that the identification of PML-ND cargo proteins would clarify those biochemical pathways that straddle the recognition of cellular damage and cell fate. We now use mass spectrometry of peptides eluted from PML coprecipitates to demonstrate that the gamma 1 (gamma1) isoform of PLC associates with nuclear PML. Though thought to act primarily in the cytoplasm, we use biochemical fractionation combined with immunocytochemistry to verify the nuclear expression of PLC-gamma1 and its interaction with PML. These are the first data to show an interaction between endogenous levels of a phosphoinositide metabolizing protein and the biophysically labile PML-ND by mass spectrometry and add weight to the view that PML-NDs may act as tumor suppressors by sequestering mitogenic effectors.

Care for adolescent pregnancy and childbirth

The rise in adolescent pregnancy in the 20th century has been influenced by declining age at menarche, increased schooling, delay of marriage, inadequate contraception and poverty. The main problems are preterm labor, hypertensive disease, anemia, more severe forms of malaria, obstructed labor in very young girls in some regions, poor maternal nutrition and poor breastfeeding. In many regions HIV infection is an important problem. The infants of adolescent mothers are more prone to low birth weight and increased neonatal mortality and morbidity. Antenatal care is often inadequate. The most important problem is the increased incidence of preterm labor and delivery, the youngest age groups running the highest risk. Technically, care of adolescents during labor need not differ from care of older women; most adolescents are not at increased risk during labor, although, they are more in need of empathic support. Generally, care of pregnant adolescents should be adjusted to their specific needs.

Unsafe abortion in adolescents

Every year, an estimated 2.0-4.4 million adolescents resort to abortion. In comparison with adults, adolescents are more likely to delay the abortion, resort to unskilled persons to perform it, use dangerous methods and present late when complications arise. Adolescents are also more likely to experience complications. Consequently, adolescents seeking abortion or presenting with complications of abortion should be considered as a medical emergency. Issues requiring special attention in the management of abortion complications in adolescents are identified. Approaches to adolescent abortion should involve all levels of the health care system, as well as the community, and should include not only management of the consequences of unsafe abortion, but also post-abortion contraception and counseling. Prevention of unwanted pregnancy by providing information on sexuality, ensuring that reproductive health services are adolescent-friendly, creating a supportive environment, building young people's social and decision-making skills, and offering counseling in times of crisis are highlighted.

A study of the effect of nasal steroid sprays in perennial allergic rhinitis patients with rhinitis medicamentosa

OBJECTIVE

To determine if rebound congestion can be reduced with concomitant nasal steroid spray usage.

STUDY DESIGN AND SETTING

Randomized, double blind, controlled single center study.

PARTICIPANTS

Twenty subjects with perennial allergic rhinitis with nasal congestion.

INTERVENTION

All subjects received 3 weeks of twice-daily oxymetazoline. After 2 weeks, subjects were randomized to 2 additional weeks of concomitant budesonide aqueous nasal spray (n = 9) or placebo (n = 10). In the sixth week, all sprays were stopped.

RESULTS

Both groups showed subjective and objective evidence of rebound congestion 24 hours after cessation of oxymetazoline (P < 0.05). Subjective rebound congestion resolved in 48 hours in the budesonide aqueous nasal spray group but persisted for over 1 week in the placebo group.

CONCLUSION

Rebound congestion is objectively present in patients with perennial allergic rhinitis after 3 weeks of oxymetazoline spray. Rebound congestion is reduced by concomitant budesonide aqueous nasal spray use.

SIGNIFICANCE

This study supports the common clinical practice of nasal steroid sprays to ameliorate rebound congestion concomitant with and after cessation of topical decongestant sprays.

Eosinophilic mucin rhinosinusitis: a distinct clinicopathological entity

BACKGROUND

Allergic fungal sinusitis (AFS) was recognized in 1981. Since 1983, a form of sinusitis histologically similar to AFS except for the absence of fungal hyphae has also been noted. The designation "eosinophilic mucin rhinosinusitis (EMRS)" is proposed. Its relationship to AFS is controversial and problematic.

OBJECTIVE

To determine whether distinctive clinical and immunological differences exist to differentiate the histological entity of EMRS from AFS.

STUDY DESIGN

Literature review and comparison of cases of AFS (n = 418) to EMRS (n = 40) from the literature, as well as cases of AFS (n = 13) and EMRS (n = 29) accrued in the present study.

RESULTS

A total of 431 AFS patients were compared with 69 EMRS patients. The mean age of patients with AFS was significantly younger than patients with EMRS (30.7 y compared with 48.0 y, respectively; P < .001). Male-to-female ratios were 1.03:1 and 1.26:1 for AFS and EMRS, respectively, and were not significantly different. Forty-one percent of patients with AFS were asthmatic compared with 93% of patients with EMRS (P < .0001). Thirteen percent of patients with AFS were aspirin sensitive compared with 54% of patients with EMRS (P < .0001). Polyp occurrence was almost 100% in both groups. Eighty-four percent of patients with AFS had allergic rhinitis (AR), while only 63% of patients with EMRS had AR (P = .004). Fifty-five percent of AFS patients had bilateral disease, in contrast to the 100% of EMRS patients with bilateral disease (P < .0001). Although average total immunoglobulin E (IgE) was elevated in both groups, it was significantly more elevated in AFS patients (range, 12-13,084 mg/ dL; mean, 1,941 mg/dL) compared with EMRS patients (range, 14-1,162 mg/dL; mean, 267 mg/dL; P < .001). Total immunoglobulin G (IgG) and IgG subclasses were seldom reported in the cases available from the literature of either AFS or EMRS. However, in the present series of EMRS, IgG1 deficiency occurred in 50% of evaluated patients (mean, 475 +/- 175 mg/dL; range, 250-869 mg/dL; normal, 422 to 1,200 mg/dL) but in no cases of AFS reported in the literature.

CONCLUSIONS

Significant clinical and immunological differences exist to distinguish AFS from EMRS. It is postulated that AFS is an allergic response to fungi in predisposed individuals, while EMRS occurs because of a systemic dysregulation of immunological controls. Because EMRS is a systemic disease, unilateral disease is not seen. In contrast, AFS, an allergic response to fungi, may occur unilaterally or bilaterally depending on the antigenic stimulation. EMRS also has a significantly higher association with asthma, an increased incidence of aspirin sensitivity, and an increased incidence of IgG1 deficiency. Therapy with a systemic steroid, a potent and indiscriminant anti-inflammatory agent, is a useful adjunct in both disorders. Fungal immunotherapy following surgical extirpation of AFS is useful in preventing AFS recurrence. It is predicted that fungal immunotherapy and antifungal agents will be ineffective in patients with EMRS. It is important to differentiate these two similar histopathological entities in future trials assessing therapeutic efficacy. Inclusion of both entities in a study could obscure recognition of the true effectiveness of intervention, because of the possible variable response differences between the two entities. This study shows that significant clinical and immunological differences exist between EMRS and AFS. The future awaits an exploration of the pathophysiological basis of these differences.

Mucormycosis of the nose and paranasal sinuses

Rhinocerebral mucormycosis is an invasive fungal infection initiated in the paranasal sinuses that frequently progresses to orbital and brain involvement. If recognized early, involvement is limited to the nasal cavity and paranasal sinuses. Diabetics in poor control are at greatest risk, however, any immunocompromised individual may be infected. The mainstays of therapy are reversal of immunosuppression, systemic amphortericin B, and surgical débridement. Survival has improved dramatically, yet deaths still occur if the infection is not recognized and not treated early in its course or if the source of immunocompromise is not reversible. Several case examples illustrate the clinical course of this unusual, but potentially fatal, fungal infection. Taxonomy, clinical presentation, diagnosis, and management of mucormycosis of the paranasal sinuses are reviewed in detail.