47 results found
Jackson WD, Giacomassi C, Ward S, et al., 2023, TLR7 activation at epithelial barriers promotes emergency myelopoiesis and lung antiviral immunity, eLife, Vol: 12, ISSN: 2050-084X
Monocytes are heterogeneous innate effector leukocytes generated in the bone marrow and released into circulation in a CCR2-dependent manner. During infection or inflammation, myelopoiesis is modulated to rapidly meet the demand for more effector cells. Danger signals from peripheral tissues can influence this process. Herein we demonstrate that repetitive TLR7 stimulation via the epithelial barriers drove a potent emergency bone marrow monocyte response in mice. This process was unique to TLR7 activation and occurred independently of the canonical CCR2 and CX3CR1 axes or prototypical cytokines. The monocytes egressing the bone marrow had an immature Ly6C-high profile and differentiated into vascular Ly6C-low monocytes and tissue macrophages in multiple organs. They displayed a blunted cytokine response to further TLR7 stimulation and reduced lung viral load after RSV and influenza virus infection. These data provide insights into the emergency myelopoiesis likely to occur in response to the encounter of single-stranded RNA viruses at barrier sites.
Tregoning JS, Stirling DC, Wang Z, et al., 2023, Formulation, inflammation, and RNA sensing impact the immunogenicity of self-amplifying RNA vaccines, Molecular Therapy : Nucleic Acids, Vol: 31, Pages: 29-42, ISSN: 2162-2531
To be effective, RNA vaccines require both in situ translation and the induction of an immune response to recruit cells to the site of immunization. These factors can pull in opposite directions with the inflammation reducing expression of the vaccine antigen. We investigated how formulation affects the acute systemic cytokine response to a self-amplifying RNA (saRNA) vaccine. We compared a cationic polymer (pABOL), a lipid emulsion (nanostructured lipid carrier, NLC), and three lipid nanoparticles (LNP). After immunization, we measured serum cytokines and compared the response to induced antibodies against influenza virus. Formulations that induced a greater cytokine response induced a greater antibody response, with a significant correlation between IP-10, MCP-1, KC, and antigen-specific antibody titers. We then investigated how innate immune sensing and signaling impacted the adaptive immune response to vaccination with LNP-formulated saRNA. Mice that lacked MAVS and are unable to signal through RIG-I-like receptors had an altered cytokine response to saRNA vaccination and had significantly greater antibody responses than wild-type mice. This indicates that the inflammation induced by formulated saRNA vaccines is not solely deleterious in the induction of antibody responses and that targeting specific aspects of RNA vaccine sensing might improve the quality of the response.
Hooftman A, Peace CG, Ryan DG, et al., 2023, Macrophage fumarate hydratase restrains mtRNA-mediated interferon production., Nature, Vol: 615, Pages: 490-498, ISSN: 0028-0836
Metabolic rewiring underlies the effector functions of macrophages1-3, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable isotope-assisted tracing, we show that an inflammatory aspartate-argininosuccinate shunt is induced following lipopolysaccharide stimulation. The shunt, supported by increased argininosuccinate synthase (ASS1) expression, also leads to increased cytosolic fumarate levels and fumarate-mediated protein succination. Pharmacological inhibition and genetic ablation of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) further increases intracellular fumarate levels. Mitochondrial respiration is also suppressed and mitochondrial membrane potential increased. RNA sequencing and proteomics analyses demonstrate that there are strong inflammatory effects resulting from FH inhibition. Notably, acute FH inhibition suppresses interleukin-10 expression, which leads to increased tumour necrosis factor secretion, an effect recapitulated by fumarate esters. Moreover, FH inhibition, but not fumarate esters, increases interferon-β production through mechanisms that are driven by mitochondrial RNA (mtRNA) release and activation of the RNA sensors TLR7, RIG-I and MDA5. This effect is recapitulated endogenously when FH is suppressed following prolonged lipopolysaccharide stimulation. Furthermore, cells from patients with systemic lupus erythematosus also exhibit FH suppression, which indicates a potential pathogenic role for this process in human disease. We therefore identify a protective role for FH in maintaining appropriate macrophage cytokine and interferon responses.
Ogger PP, Martín MG, Michalaki C, et al., 2022, Type I interferon signaling deficiency results in dysregulated innate immune responses to SARS-CoV-2 in mice, European Journal of Immunology, Vol: 52, Pages: 1768-1775, ISSN: 0014-2980
SARS-CoV-2 is a newly emerged coronavirus, causing the global pandemic of respiratory coronavirus disease (COVID-19). The type I interferon (IFN) pathway is of particular importance for anti-viral defence and recent studies identified that type I IFNs drive early inflammatory responses to SARS-CoV-2. Here, we use a mouse model of SARS-CoV-2 infection, facilitating viral entry by intranasal recombinant Adeno-Associated Virus (rAAV) transduction of hACE2 in wildtype (WT) and type I IFN-signalling-deficient (Ifnar1-/- ) mice, to study type I IFN signalling deficiency and innate immune responses during SARS-CoV-2 infection. Our data show that type I IFN signaling is essential for inducing anti-viral effector responses to SARS-CoV-2, control of virus replication and to prevent enhanced disease. Furthermore, hACE2-Ifnar1-/- mice had increased gene expression of the chemokine Cxcl1 and airway infiltration of neutrophils as well as a reduced and delayed production of monocyte-recruiting chemokine CCL2. hACE2-Ifnar1-/- mice showed altered recruitment of inflammatory myeloid cells to the lung upon SARS-CoV-2 infection, with a shift from Ly6C+ to Ly6C- expressing cells. Together, our findings suggest that type I IFN deficiency results in a dysregulated innate immune response to SARS-CoV-2 infection. This article is protected by copyright. All rights reserved.
Penn R, Tregoning J, Flight K, et al., 2022, Levels of Influenza defective viral genomes determine pathogenesis in the BALB/c mouse model, Journal of Virology, Vol: 96, Pages: 1-18, ISSN: 0022-538X
Defective viral genomes (DVGs), which are generated by the viral polymerase in error during RNA replication, can trigger innate immunity and are implicated in altering the clinical outcome of infection. Here, we investigated the impact of DVGs on innate immunity and pathogenicity in a BALB/c mouse model of influenza virus infection. We generated stocks of influenza viruses containing the internal genes of an H5N1 virus that contain different levels of DVGs (indicated by different genome to PFU ratios). In lung epithelial cells, the high DVG stock was immunostimulatory at early time points post infection. DVGs were amplified during virus replication in myeloid immune cells and triggered pro-inflammatory cytokine production. In the mouse model, infection with the different virus stocks produced divergent outcomes. The high DVG stock induced an early type I IFN resonse that limited viral replication in the lungs resulting in minimal weight loss. In contrast, the virus stock with low levels of DVGs replicated to hightitres and amplified DVGs over time resulting in elevated pro-inflammatory cytokines accompanied by rapid weight loss and increased morbidity and mortality. Our results suggest that the timing and levels of immunostimulatory DVGs generated duringinfection contribute to H5N1 pathogenesis.
Michalaki C, Dean C, Johansson C, 2022, The use of precision-cut lung slices for studying innate immunity to viral infections., Current Protocols, Vol: 2, Pages: e505-e505, ISSN: 2691-1299
Precision-cut lung slices (PCLS) are a novel tool to study cells of the lower airways. As PCLS retain the integrity and architecture of the lung, they constitute a robust model for studying the cells of the lower respiratory tract. Use of PCLS for imaging has been previously documented; however, other applications and techniques can also be applied to PCLS to increase their use and therefore decrease the number of animals needed for each experiment. We present a detailed protocol for generating PCLS from the murine lung. We show that cultured PCLS remain viable up to at least 8 days of culture, that RNA can be isolated from the tissue, and that flow cytometry can be carried out on the cells obtained from the PCLS. Furthermore, we demonstrate that cytokines and chemokines can be detected in the culture supernatants of PCLS exposed to viruses. Overall, these protocols expand the use of PCLS, especially for infection studies. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Precision-cut lung slices (PCLS) Basic Protocol 2: PCLS culture and viability Basic Protocol 3: RNA isolation from PCLS, cDNA conversion, and RT-qPCR Basic Protocol 4: Staining of cells from PCLS for flow cytometry Basic Protocol 5: In vivo RSV administration and ex vivo PCLS RSV exposure.
Varese A, Nakawesi J, Farias A, et al., 2022, Type I interferons and MAVS signaling are necessary for tissue resident memory CD8+ T cell responses to RSV infection, PLoS Pathogens, Vol: 18, ISSN: 1553-7366
Respiratory syncytial virus (RSV) can cause bronchiolitis and viral pneumonia in young children and the elderly. Lack of vaccines and recurrence of RSV infection indicate the difficulty in eliciting protective memory immune responses. Tissue resident memory T cells (TRM) can confer protection from pathogen re-infection and, in human experimental RSV infection, the presence of lung CD8+ TRM cells correlates with a better outcome. However, the requirements for generating and maintaining lung TRM cells during RSV infection are not fully understood. Here, we use mouse models to assess the impact of innate immune response determinants in the generation and subsequent expansion of the TRM cell pool during RSV infection. We show that CD8+ TRM cells expand independently from systemic CD8+ T cells after RSV re-infection. Re-infected MAVS and MyD88/TRIF deficient mice, lacking key components involved in innate immune recognition of RSV and induction of type I interferons (IFN-α/β), display impaired expansion of CD8+ TRM cells and reduction in antigen specific production of granzyme B and IFN-γ. IFN-α treatment of MAVS deficient mice during primary RSV infection restored TRM cell expansion upon re-challenge but failed to recover TRM cell functionality. Our data reveal how innate immunity, including the axis controlling type I IFN induction, instructs and regulates CD8+ TRM cell responses to RSV infection, suggesting possible mechanisms for therapeutic intervention.
Antepowicz A, Habib O, Kirsebom F, et al., 2021, Lentiviral and AAV-mediated expression of palivizumab offer protection against Respiratory Syncytial Virus infection, Scientific Reports, Vol: 11, Pages: 1-12, ISSN: 2045-2322
Respiratory syncytial virus (RSV) infection is a common cause of hospitalisation in infants and the elderly. Palivizumab prophylaxis is the only approved treatment modality but is costly and only offered to select vulnerable populations. Here, we investigated gene delivery approaches via recombinant adeno-associated virus (rAAV2/8) and simian immunodeficiency virus (rSIV.F/HN) vectors to achieve sustained in vivo production of palivizumab in a murine model. Delivery of palivizumab-expressing vectors 28 days prior to RSV challenge resulted in complete protection from RSV-induced weight loss. This approach offers prophylaxis against RSV infection, allowing for wider use and reduction in treatment costs in vulnerable populations.
Johansson C, Kirsebom F, 2021, Neutrophils in respiratory viral infections, Mucosal Immunology, Vol: 14, Pages: 815-827, ISSN: 1933-0219
Viral respiratory infections are a common cause of severe disease, especially in infants,people who are immunocompromised and in the elderly. Neutrophils, an important innateimmune cell, infiltrate the lungs rapidly after an inflammatory insult. The most wellcharacterized effector mechanisms by which neutrophils contribute to host defense arelargely extracellular and the involvement of neutrophils in protection from numerousbacterial and fungal infections is well established. However, the role of neutrophils inresponses to viruses, which replicate intracellularly, has been less studied. It remainsunclear whether and, by which underlying immunological mechanisms, neutrophilscontribute to viral control or confer protection against an intracellular pathogen.Furthermore, neutrophils need to be tightly regulated to avoid bystander damage to hosttissues. This is especially relevant in the lung where damage to delicate alveolar structurescan compromise gas exchange with life-threatening consequences. It is inherently lessclear how neutrophils can contribute to host immunity to viruses without causingimmunopathology and/or exacerbating disease severity. In this review we summarize anddiscuss the current understanding of how neutrophils in the lung direct immune responsesto viruses, control viral replication and spread, and cause pathology during respiratory viralinfections.
Harker JA, Johansson C, 2021, Rapidly deployable mouse models of SARS-CoV-2 infection add flexibility to the COVID-19 toolbox, American Journal of Respiratory Cell and Molecular Biology, Vol: 64, Pages: 7-9, ISSN: 1044-1549
Habibi M, Thwaites R, Chang M, et al., 2020, Neutrophilic inflammation in the respiratory mucosa predisposes to RSV infection, Science, Vol: 370, Pages: 1-15, ISSN: 0036-8075
INTRODUCTIONEven with intimate exposure to a virus, some people fail to become infected. Variable transmission partly depends on the dose and duration of exposure but is also governed by the immune status of the host, such as the presence of specific protective antibodies or T cells. However, for some infections, the reasons for erratic transmission are largely unknown. For example, respiratory syncytial virus (RSV) can repeatedly reinfect individuals throughout their lives despite the presence of specific immunity. Additionally, antibodies and T cells have limited efficacy against newly emergent pathogens with pandemic potential. However, the intrinsic and innate mechanisms underlying protection when people are exposed to these viruses are poorly understood.RATIONALEWe reasoned that the prior state of the respiratory mucosa’s innate defenses may contribute to the variable outcome of RSV inoculation. By performing experimental challenge of adult volunteers, we were able to measure variations in the status of the nasal mucosa before inoculation and in mucosal responses during the presymptomatic phase of infection. Neither of these phases is easily observable during natural spontaneous transmission. Our observations could then be validated using specific interventional studies in a well-established mouse model of RSV infection.RESULTSAfter nasal administration of RSV, 57% of inoculated volunteers became infected. The uptake of infection was poorly explained by specific B or T cell immunity. However, transcriptomic profiling of the nasal tissue before inoculation demonstrated a neutrophilic inflammatory signal in those destined to develop symptomatic infection, and this was associated with suppression of an early interleukin-17 (IL-17)–dominated immune response during the presymptomatic period. This was followed by symptomatic infection associated with the expression of proinflammatory cytokines. By contrast, those who resisted infection showed a transient
Paulsen M, Varese A, Pinpathomrat N, et al., 2020, MAVS-deficiency is associated with a reduced T cell response upon secondary RSV infection in mice, Frontiers in Immunology, Vol: 11, ISSN: 1664-3224
Infections with respiratory syncytial virus (RSV) occurs repeatedly throughout life because sustained, protective memory responses fail to develop. Why this occurs is not known. During RSV infection the recognition of the virus via the cytosolic RIG-I like receptors and signaling via the adaptor protein MAVS is crucial for mounting an innate immune response. However, if this signaling pathway is important for T cell responses during primary infection and during re-infection is not fully elucidated. We describe a second peak of pro-inflammatory mediators during the primary immune response to RSV that coincides with the arrival of T cells into the lung. This second peak of cytokines/chemokines is regulated differently than the early peak and is largely independent of signaling via MAVS. This was concurrent with Mavs−/− mice mounting a strong T cell response to primary RSV infection, with robust IFN-γ; and Granzyme B production. However, after RSV re-infection, Mavs−/− mice showed fewer CD4+ and CD8+ short term memory T cells and their capacity to produce IFN-γ; and Granzyme B, was decreased. In sum, cytosolic recognition of RSV is important not only for initiating innate anti-viral responses but also for generating or maintaining efficient, short term T cell memory responses.
Johansson C, Makris S, 2020, R848 or influenza virus can induce potent innate immune responses in the lungs of neonatal mice, Mucosal Immunology, Vol: 14, Pages: 267-276, ISSN: 1933-0219
Innate immune responses are important to protect the neonatal lung, which becomes exposed to commensal and pathogenic microorganisms immediately after birth, at a time when both the lung and the adaptive immune system are still developing. How immune cells in the neonatal lung respond to innate immune stimuli, including toll-like receptor (TLR) agonists, or viruses, is currently unclear. To address this, adult and neonatal mice were intranasally administered with various innate immune stimuli, respiratory syncytial virus (RSV) or influenza virus and cytokine and chemokine levels were quantified. The neonatal lungs responded weakly to RSV and most stimuli but more strongly than adult mice to R848 and influenza virus, both of which activate TLR7 and the inflammasome. Notably, neonatal lungs also contained higher levels of cAMP, a secondary messenger produced following adenosine receptor signaling, than adult lungs and increased responsiveness to R848 was observed in adult mice when adenosine was coadministered. Our data suggest that the neonatal lung may respond preferentially to stimuli that coactivate TLR7 and the inflammasome and that these responses may be amplified by extracellular adenosine. Improved understanding of regulation of immune responses in the neonatal lung can inform the development of vaccine adjuvants for the young.
Kirsebom F, Michalaki C, Agueda-Oyarzabal M, et al., 2020, Neutrophils do not impact viral load or the peak of disease severity during RSV infection, Scientific Reports, Vol: 10, ISSN: 2045-2322
Lung and airway neutrophils are a hallmark of severe disease in infants with respiratory syncytial virus (RSV)-induced lower respiratory tract infections. Despite their abundance in the lungs during RSV infection of both mice and man, the role of neutrophils in viral control and in immune pathology is not clear. Here, antibody mediated neutrophil depletion was used to investigate the degree to which neutrophils impact the lung immune environment, the control of viral replication and the peak severity of disease after RSV infection of mice. Neutrophil depletion did not substantially affect the levels of inflammatory mediators such as type I interferons, IL-6, TNF-α or IL-1β in response to RSV. In addition, the lack of neutrophils did not change the viral load during RSV infection. Neither neutrophil depletion nor the enhancement of lung neutrophils by administration of the chemoattractant CXCL1 during RSV infection affected disease severity as measured by weight loss. Therefore, in this model of RSV infection, lung neutrophils do not offer obvious benefits to the host in terms of increasing anti-viral inflammatory responses or restricting viral replication and neutrophils do not contribute to disease severity.
Kirsebom FCM, Kausar F, Nuriev R, et al., 2019, Neutrophil recruitment and activation are differentially dependent on MyD88/TRIF and MAVS signaling during RSV infection, Mucosal Immunology, Vol: 12, Pages: 1244-1255, ISSN: 1933-0219
Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections, especially in infants. Lung neutrophilia is a hallmark of RSV disease but the mechanism by which neutrophils are recruited and activated is unclear. Here, we investigate the innate immune signaling pathways underlying neutrophil recruitment and activation in RSV-infected mice. We show that MyD88/TRIF signaling is essential for lung neutrophil recruitment while MAVS signaling, leading to type I IFN production, is necessary for neutrophil activation. Consistent with that notion, administration of type I IFNs to the lungs of RSV-infected Mavs-/- mice partially activates lung neutrophils recruited via the MyD88/TRIF pathway. Conversely, lack of neutrophil recruitment to the lungs of RSV-infected Myd88/Trif-/- mice can be reversed by administration of chemoattractants and those neutrophils become fully activated. Interestingly, Myd88/Trif-/- mice did not have increased lung RSV loads during infection, suggesting that neutrophils are dispensable for control of the virus. Thus, two distinct pathogen sensing pathways collaborate for neutrophil recruitment and full activation during RSV infection.
Progatzky F, Jha A, Wane M, et al., 2019, Induction of innate cytokine responses by respiratory mucosal challenge with R848 in zebrafish, mice and humans, Journal of Allergy and Clinical Immunology, Vol: 144, Pages: 342-345.e7, ISSN: 0091-6749
We compared live zebrafish, mouse and human nasal challenge responses to the TLR7/8 agonist resiquimod (R848). We found remarkably similar induction of mediators in the three species, offering novel mucosal models of innate anti-viral immunity.
Nuriev R, Johansson C, 2019, Chemokine regulation of inflammation during respiratory syncytial virus infection., F1000Res, Vol: 8
Respiratory syncytial virus (RSV) can cause severe lower respiratory tract infections especially in infants, immunocompromised individuals and the elderly and is the most common cause of infant hospitalisation in the developed world. The immune responses against RSV are crucial for viral control and clearance but, if dysregulated, can also result in immunopathology and impaired gas exchange. Lung immunity to RSV and other respiratory viruses begins with the recruitment of immune cells from the bloodstream into the lungs. This inflammatory process is controlled largely by chemokines, which are small proteins that are produced in response to innate immune detection of the virus or the infection process. These chemokines serve as chemoattractants for granulocytes, monocytes, lymphocytes and other leukocytes. In this review, we highlight recent advances in the field of RSV infection and disease, focusing on how chemokines regulate virus-induced inflammation.
Antepowicz A, Kirsebom F, Johansson C, et al., 2018, Antibody gene transfer for prophylaxis of respiratory syncytial virus (RSV) infection, Conference on Changing the Face of Modern Medicine - Stem Cell and Gene Therapy, Publisher: MARY ANN LIEBERT, INC, Pages: A118-A118, ISSN: 1043-0342
Li H, Bradley KC, Long JS, et al., 2018, Internal genes of a highly pathogenic H5N1 influenza virus determine high viral replication in myeloid cells and severe outcome of infection in mice., PLoS Pathogens, Vol: 14, ISSN: 1553-7366
The highly pathogenic avian influenza (HPAI) H5N1 influenza virus has been a public health concern for more than a decade because of its frequent zoonoses and the high case fatality rate associated with human infections. Severe disease following H5N1 influenza infection is often associated with dysregulated host innate immune response also known as cytokine storm but the virological and cellular basis of these responses has not been clearly described. We rescued a series of 6:2 reassortant viruses that combined a PR8 HA/NA pairing with the internal gene segments from human adapted H1N1, H3N2, or avian H5N1 viruses and found that mice infected with the virus with H5N1 internal genes suffered severe weight loss associated with increased lung cytokines but not high viral load. This phenotype did not map to the NS gene segment, and NS1 protein of H5N1 virus functioned as a type I IFN antagonist as efficient as NS1 of H1N1 or H3N2 viruses. Instead we discovered that the internal genes of H5N1 virus supported a much higher level of replication of viral RNAs in myeloid cells in vitro but not in epithelial cells and that this was associated with high induction of type I IFN in myeloid cells. We also found that in vivo during H5N1 recombinant virus infection cells of haematopoetic origin were infected and produced type I IFN and proinflammatory cytokines. Taken together our data infer that human and avian influenza viruses are differently controlled by host factors in alternative cell types; internal gene segments of avian H5N1 virus uniquely drove high viral replication in myeloid cells, which triggered an excessive cytokine production, resulting in severe immunopathology.
Webb LM, Lundie RJ, Borger JG, et al., 2017, Type I interferon is required for T helper (Th) 2 induction by dendritic cells, EMBO JOURNAL, Vol: 36, Pages: 2404-2418, ISSN: 0261-4189
Type 2 inflammation is a defining feature of infection with parasitic worms (helminths), as well as being responsible for widespread suffering in allergies. However, the precise mechanisms involved in T helper (Th) 2 polarization by dendritic cells (DCs) are currently unclear. We have identified a previously unrecognized role for type I IFN (IFN‐I) in enabling this process. An IFN‐I signature was evident in DCs responding to the helminth Schistosoma mansoni or the allergen house dust mite (HDM). Further, IFN‐I signaling was required for optimal DC phenotypic activation in response to helminth antigen (Ag), and efficient migration to, and localization with, T cells in the draining lymph node (dLN). Importantly, DCs generated from Ifnar1−/− mice were incapable of initiating Th2 responses in vivo. These data demonstrate for the first time that the influence of IFN‐I is not limited to antiviral or bacterial settings but also has a central role to play in DC initiation of Th2 responses.
Makris S, Paulsen M, Johansson C, 2017, Type I interferons as regulators of lung inflammation, Frontiers in Immunology, Vol: 8, ISSN: 1664-3224
Immune responses to lung infections must be tightly regulated in order to permit pathogen eradication while maintaining organ function. Exuberant or dysregulated inflammation can impair gas exchange and underlies many instances of lung disease. An important driver of inflammation in the lung is the interferon (IFN) response. Type I IFNs are anti-viral cytokines that induce a large range of proteins that impair viral replication in infected cells. This cell-intrinsic action plays a crucial role in protecting the lungs from spread of respiratory viruses. However, type I IFNs have also recently been found to be central to the initiation of lung inflammatory responses, by inducing recruitment and activation of immune cells. This helps control virus burden but can cause detrimental immunopathology and contribute to disease severity. Furthermore, there is now increasing evidence that type I IFNs are not only induced after viral infections but also after infection with bacteria and fungi. The pro-inflammatory function of type I IFNs in the lung opens up the possibility of immune modulation directed against this anti-viral cytokine family. In this review, the initiation and signaling of type I IFNs as well as their role in driving and maintaining lung inflammation will be discussed.
Respiratory syncytial virus (RSV) is an exceptional mucosal pathogen. It specializes in infection of the ciliated respiratory epithelium, causing disease of variable severity with little or no direct systemic effects. It infects virtually all children by the age of three years and then repeatedly infects throughout life; this it does despite relatively slight variations in antigenicity, apparently by inducing selective immunological amnesia. Inappropriate or dysregulated responses to RSV can be pathogenic, causing disease-enhancing inflammation that contributes to short- and long-term effects. In addition, RSV's importance as a largely unrecognized pathogen of debilitated older people is increasingly evident. Vaccines that induce nonpathogenic protective immunity may soon be available, and it is possible that different vaccines will be optimal for infants; older children; young to middle-age adults (including pregnant women); and elderly persons. At the dawn of RSV vaccination, it is timely to review what is known (and unknown) about immune responses to this fascinating virus.
Johansson C, 2016, Respiratory syncytial virus infection: an innate perspective., F1000Research, Vol: 5, ISSN: 2046-1402
Respiratory syncytial virus (RSV) is a common cause of upper respiratory tract infection in children and adults. However, infection with this virus sometimes leads to severe lower respiratory disease and is the major cause of infant hospitalisations in the developed world. Several risk factors such as baby prematurity and congenital heart disease are known to predispose towards severe disease but previously healthy, full-term infants can also develop bronchiolitis and viral pneumonia during RSV infection. The causes of severe disease are not fully understood but may include dysregulation of the immune response to the virus, resulting in excessive recruitment and activation of innate and adaptive immune cells that can cause damage. This review highlights recent discoveries on the balancing act of immune-mediated virus clearance versus immunopathology during RSV infection.
Makris S, Bajorek M, Culley F, et al., 2016, Alveolar Macrophages Can Control Respiratory Syncytial Virus Infection in the Absence of Type I Interferons, Journal of Innate Immunity, Vol: 8, ISSN: 1662-8128
Goritzka M, Pereira C, Makris S, et al., 2015, T cell responses are elicited against Respiratory Syncytial Virus in the absence of signalling through TLRs, RLRs and IL-1R/IL-18R, Scientific Reports, Vol: 5, ISSN: 2045-2322
Pattern recognition receptors (PRRs) and cytokine receptors are key players in the initiation of immune responses to infection. PRRs detecting viral RNA, such as toll like receptor (TLR)-3, -7/8, and RIG-I like receptors (RLRs; RIG-I and MDA-5), as well as cytokine receptors such as interleukin 1 receptor (IL-1R), have been implicated in responses to RNA viruses that infect the airways. The latter includes respiratory syncytial virus (RSV), a human pathogen that can cause severe lower respiratory tract infections, especially in infants. To evaluate the collective contribution of PRRs and IL-1R signalling to RSV immunity, we generated Myd88/Trif/Mavs−/− mice that are deficient in signalling by all TLRs, RLRs and IL-1R, as well as other cytokine receptors such as IL-18 receptor. Early production of pro-inflammatory mediators and lung infiltration by immune cells were completely abrogated in infected Myd88/Trif/Mavs−/− mice. However, RSV-specific CD8+ T cells were elicited and recruited into the lungs and airways. Consistent with these findings, Myd88/Trif/Mavs−/− mice survived RSV infection but displayed higher viral load and weight loss. These data highlight an unappreciated level of redundancy in pathways that couple innate virus sensing to adaptive immunity, providing the host with remarkable resilience to infection.
Goritzka M, Makris S, Kausar F, et al., 2015, Alveolar macrophage-derived type I interferons orchestrate innate immunity to RSV through recruitment of antiviral monocytes, Journal of Experimental Medicine, Vol: 212, Pages: 699-714, ISSN: 0022-1007
Type I interferons (IFNs) are important for host defense from viral infections, acting to restrict viral production in infected cells and to promote antiviral immune responses. However, the type I IFN system has also been associated with severe lung inflammatory disease in response to respiratory syncytial virus (RSV). Which cells produce type I IFNs upon RSV infection and how this directs immune responses to the virus, and potentially results in pathological inflammation, is unclear. Here, we show that alveolar macrophages (AMs) are the major source of type I IFNs upon RSV infection in mice. AMs detect RSV via mitochondrial antiviral signaling protein (MAVS)–coupled retinoic acid–inducible gene 1 (RIG-I)–like receptors (RLRs), and loss of MAVS greatly compromises innate immune restriction of RSV. This is largely attributable to loss of type I IFN–dependent induction of monocyte chemoattractants and subsequent reduced recruitment of inflammatory monocytes (infMo) to the lungs. Notably, the latter have potent antiviral activity and are essential to control infection and lessen disease severity. Thus, infMo recruitment constitutes an important and hitherto underappreciated, cell-extrinsic mechanism of type I IFN–mediated antiviral activity. Dysregulation of this system of host antiviral defense may underlie the development of RSV-induced severe lung inflammation.
Goritzka M, Makris S, Kausar F, et al., 2014, Alveolar macrophages modulate innate immune responses to Respiratory Syncytial Virus (RSV) infection through MAVS signalling and type I interferons, 9th European-Mucosal-Immunology-Group Meeting, Publisher: WILEY-BLACKWELL, Pages: 7-8, ISSN: 0019-2805
Durant LR, Pereira C, Boakye A, et al., 2014, DNGR-1 is dispensable for CD8(+) T-cell priming during respiratory syncytial virus infection, European Journal of Immunology, Vol: 44, Pages: 2340-2348, ISSN: 1521-4141
During respiratory syncytial virus (RSV) infection CD8+ T cells both assist in viral clearance and contribute to immunopathology. CD8+ T cells recognize viral peptides presented by dendritic cells (DCs), which can directly present viral antigens when infected or, alternatively, “cross-present” antigens after endocytosis of dead or dying infected cells. Mouse CD8α+ and CD103+ DCs excel at cross-presentation, in part because they express the receptor DNGR-1 that detects dead cells by binding to exposed F-actin and routes internalized cell debris into the cross-presentation pathway. As RSV causes death in infected epithelial cells, we tested whether cross-presentation via DNGR-1 is necessary for CD8+ T-cell responses to the virus. DNGR-1-deficient or wild-type mice were intranasally inoculated with RSV and the magnitude of RSV-specific CD8+ T-cell induction was measured. We found that during live RSV infection, cross-presentation via DNGR-1 did not have a major role in the generation of RSV–specific CD8+ T-cell responses. However, after intranasal immunization with dead cells infected with RSV, a dependence on DNGR-1 for RSV-specific CD8+ T-cell responses was observed, confirming the ascribed role of the receptor. Thus, direct presentation by DCs may be the major pathway initiating CD8+ T-cell responses to RSV, while DNGR-1-dependent cross-presentation has no detectable role.
Goritzka M, Durant LR, Pereira C, et al., 2014, Alpha/Beta Interferon Receptor Signaling Amplifies Early Proinflammatory Cytokine Production in the Lung during Respiratory Syncytial Virus Infection, Journal of Virology, Vol: 88, Pages: 6128-6136, ISSN: 0022-538X
Type I interferons (IFNs) are produced early upon virus infection and signal through the alpha/beta interferon (IFN-α/β) receptor (IFNAR) to induce genes that encode proteins important for limiting viral replication and directing immune responses. To investigate the extent to which type I IFNs play a role in the local regulation of inflammation in the airways, we examined their importance in early lung responses to infection with respiratory syncytial virus (RSV). IFNAR1-deficient (IFNAR1−/−) mice displayed increased lung viral load and weight loss during RSV infection. As expected, expression of IFN-inducible genes was markedly reduced in the lungs of IFNAR1−/− mice. Surprisingly, we found that the levels of proinflammatory cytokines and chemokines in the lungs of RSV-infected mice were also greatly reduced in the absence of IFNAR signaling. Furthermore, low levels of proinflammatory cytokines were also detected in the lungs of IFNAR1−/− mice challenged with noninfectious innate immune stimuli such as selected Toll-like receptor (TLR) agonists. Finally, recombinant IFN-α was sufficient to potentiate the production of inflammatory mediators in the lungs of wild-type mice challenged with innate immune stimuli. Thus, in addition to its well-known role in antiviral resistance, type I IFN receptor signaling acts as a central driver of early proinflammatory responses in the lung. Inhibiting the effects of type I IFNs may therefore be useful in dampening inflammation in lung diseases characterized by enhanced inflammatory cytokine production.
Durant LR, Makris S, Voorburg CM, et al., 2013, Regulatory T Cells Prevent Th2 Immune Responses and Pulmonary Eosinophilia during Respiratory Syncytial Virus Infection in Mice, JOURNAL OF VIROLOGY, Vol: 87, Pages: 10946-10954, ISSN: 0022-538X
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