46 results found
Killingley B, Mann AJ, Kalinova M, et al., 2022, Safety, tolerability and viral kinetics during SARS-CoV-2 human challenge in young adults, Nature Medicine, Pages: 1-27, ISSN: 1078-8956
Since its emergence in 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused hundreds of millions of cases and continues to circulate globally. To establish a novel SARS-CoV-2 human challenge model that enables controlled investigation of pathogenesis, correlates of protection and efficacy testing of forthcoming interventions, 36 volunteers aged 18–29 years without evidence of previous infection or vaccination were inoculated with 10 TCID50 of a wild-type virus (SARS-CoV-2/human/GBR/484861/2020) intranasally in an open-label, non-randomized study (ClinicalTrials.gov identifier NCT04865237; funder, UK Vaccine Taskforce). After inoculation, participants were housed in a high-containment quarantine unit, with 24-hour close medical monitoring and full access to higher-level clinical care. The study’s primary objective was to identify an inoculum dose that induced well-tolerated infection in more than 50% of participants, with secondary objectives to assess virus and symptom kinetics during infection. All pre-specified primary and secondary objectives were met. Two participants were excluded from the per-protocol analysis owing to seroconversion between screening and inoculation, identified post hoc. Eighteen (~53%) participants became infected, with viral load (VL) rising steeply and peaking at ~5 days after inoculation. Virus was first detected in the throat but rose to significantly higher levels in the nose, peaking at ~8.87 log10 copies per milliliter (median, 95% confidence interval (8.41, 9.53)). Viable virus was recoverable from the nose up to ~10 days after inoculation, on average. There were no serious adverse events. Mild-to-moderate symptoms were reported by 16 (89%) infected participants, beginning 2–4 days after inoculation, whereas two (11%) participants remained asymptomatic (no reportable symptoms). Anosmia or dysosmia developed more slowly in 15 (83%) participants. No quantitative cor
McKendry R, Lemm N-M, Papargyris L, et al., 2022, Human Challenge Studies with Coronaviruses Old and New., Curr Top Microbiol Immunol, ISSN: 0070-217X
Coronavirus infections have been known to cause disease in animals since as early as the 1920s. However, only seven coronaviruses capable of causing human disease have been identified thus far. These Human Coronaviruses (HCoVs) include the causes of the common cold, but more recent coronaviruses that have emerged (i.e. SARS-CoV, MERS-CoV and SARS-CoV-2) are associated with much greater morbidity and mortality. HCoVs have been relatively under-studied compared to other common respiratory infections, as historically they have presented with mild symptoms. This has led to a relatively limited understanding of their animal reservoirs, transmission and determinants of immune protection. To address this, human infection challenge studies with HCoVs have been performed that enable a detailed clinical and immunological analysis of the host response at specific time points under controlled conditions with standardised viral inocula. Until recently, all such human challenge studies were conducted with common cold HCoVs, with the study of SARS-CoV and MERS-CoV unacceptable due to their greater pathogenicity. However, with the emergence of SARS-CoV-2 and the COVID-19 pandemic during which severe outcomes in young healthy adults have been rare, human challenge studies with SARS-CoV-2 are now being developed. Two SARS-CoV-2 human challenge studies in the UK studying individuals with and without pre-existing immunity are underway. As well as providing a platform for testing of antivirals and vaccines, such studies will be critical for understanding the factors associated with susceptibility to SARS-CoV-2 infection and thus developing improved strategies to tackle the current as well as future HCoV pandemics. Here, we summarise the major questions about protection and pathogenesis in HCoV infection that human infection challenge studies have attempted to answer historically, as well as the knowledge gaps that aim to be addressed with contemporary models.
Cable J, Rappuoli R, Klemm EJ, et al., 2022, Innovative vaccine approaches-a Keystone Symposia report, ANNALS OF THE NEW YORK ACADEMY OF SCIENCES, ISSN: 0077-8923
Cuthbertson L, James P, Habibi MS, et al., 2022, Resilience of the respiratory microbiome in controlled adult RSV challenge study, European Respiratory Journal, Vol: 59, ISSN: 0903-1936
Barker C, Collet K, Gbesemete D, et al., 2022, Public attitudes to a human challenge study with SARS-CoV-2: a mixed-methods study., Wellcome Open Res, Vol: 7, ISSN: 2398-502X
Background: Human challenge studies involve the deliberate exposure of healthy volunteers to an infectious micro-organism in a highly controlled and monitored way. They are used to understand infectious diseases and have contributed to the development of vaccines. In early 2020, the UK started exploring the feasibility of establishing a human challenge study with SARS-CoV-2. Given the significant public interest and the complexity of the potential risks and benefits, it is vital that public views are considered in the design and approval of any such study and that investigators and ethics boards remain accountable to the public. Methods: Mixed methods study comprising online surveys conducted with 2,441 UK adults and in-depth virtual focus groups with 57 UK adults during October 2020 to explore the public's attitudes to a human challenge study with SARS-CoV-2 taking place in the UK. Results: There was overall agreement across the surveys and focus groups that a human challenge study with SARS-CoV-2 should take place in the UK. Transparency of information, trust and the necessity to provide clear information on potential risks to study human challenge study participants were important. The perceived risks of taking part included the risk of developing long-term effects from COVID, impact on personal commitments and mental health implications of isolation. There were a number of practical realities to taking part that would influence a volunteer's ability to participate (e.g. Wi-Fi, access to exercise, outside space and work, family and pet commitments). Conclusions: The results identified practical considerations for teams designing human challenge studies. Recommendations were grouped: 1) messaging to potential study participants, 2) review of the protocol and organisation of the study, and 3) more broadly, making the study more inclusive and relevant. This study highlights the value of public consultation in research, particularly in fields attracting public intere
Rapeport G, Chiu C, McShane H, 2021, SARS-CoV-2 Human Challenge Studies. Reply., N Engl J Med, Vol: 385
Grzesiak E, Bent B, McClain MT, et al., 2021, Assessment of the Feasibility of Using Noninvasive Wearable Biometric Monitoring Sensors to Detect Influenza and the Common Cold Before Symptom Onset, JAMA NETWORK OPEN, Vol: 4, ISSN: 2574-3805
She X, Zhai Y, Henao R, et al., 2021, Adaptive multi-channel event segmentation and feature extraction for monitoring health outcomes, IEEE Transactions on Biomedical Engineering, Vol: 68, Pages: 2377-2388, ISSN: 0018-9294
Objective: To develop a multi-channel device event segmentation and feature extraction algorithm that is robust to changes in data distribution. Methods: We introduce an adaptive transfer learning algorithm to classify and segment events from non-stationary multi-channel temporal data. Using a multivariate hidden Markov model (HMM) and Fisher's linear discriminant analysis (FLDA) the algorithm adaptively adjusts to shifts in distribution over time. The proposed algorithm is unsupervised and learns to label events without requiring a priori information about true event states. The procedure is illustrated on experimental data collected from a cohort in a human viral challenge (HVC) study, where certain subjects have disrupted wake and sleep patterns after exposure to an H1N1 influenza pathogen. Results: Simulations establish that the proposed adaptive algorithm significantly outperforms other event classification methods. When applied to early time points in the HVC data, the algorithm extracts sleep/wake features that are predictive of both infection and infection onset time. Conclusion: The proposed transfer learning event segmentation method is robust to temporal shifts in data distribution and can be used to produce highly discriminative event-labeled features for health monitoring. Significance: Our integrated multisensor signal processing and transfer learning method is applicable to many ambulatory monitoring applications.
Rapeport G, Smith E, Gilbert A, et al., 2021, SARS-CoV-2 human challenge studies - establishing the model during an evolving pandemic, New England Journal of Medicine, Vol: 385, Pages: 961-964, ISSN: 0028-4793
Paterson S, Kar S, Ung SK, et al., 2021, Innate-like gene expression of lung-resident memory CD8+ T-cells during experimental human influenza, American Journal of Respiratory and Critical Care Medicine, Vol: 204, Pages: 826-841, ISSN: 1073-449X
Rationale: Suboptimal vaccine immunogenicity and antigenic mismatch, compounded by poor uptake, means that influenza remains a major global disease. T cells recognizing peptides derived from conserved viral proteins could enhance vaccine-induced cross-strain protection.Objectives: To investigate the kinetics, phenotypes, and function of influenza virus–specific CD8+ resident memory T (Trm) cells in the lower airway and infer the molecular pathways associated with their response to infection in vivo.Methods: Healthy volunteers, aged 18–55, were inoculated intranasally with influenza A/California/4/09(H1N1). Blood, upper airway, and (in a subgroup) lower airway samples were obtained throughout infection. Symptoms were assessed by using self-reported diaries, and the nasal viral load was assessed by using quantitative PCR. T-cell responses were analyzed by using a three-color FluoroSpot assay, flow cytometry with MHC I–peptide tetramers, and RNA sequencing, with candidate markers being confirmed by using the immunohistochemistry results for endobronchial biopsy specimens.Measurements and Main Results: After challenge, 57% of participants became infected. Preexisting influenza-specific CD8+ T cells in blood correlated strongly with a reduced viral load, which peaked at Day 3. Influenza-specific CD8+ T cells in BAL fluid were highly enriched and predominantly expressed the Trm markers CD69 and CD103. Comparison between preinfection CD8+ T cells in BAL fluid and blood by using RNA sequencing revealed 3,928 differentially expressed genes, including all major Trm-cell markers. However, gene set enrichment analysis of BAL-fluid CD8+ T cells showed primarily innate cell–related pathways and, during infection, included upregulation of innate chemokines (Cxcl1, Cxcl10, and Cxcl16) that were also expressed by CD8+ cells in bronchial tissues.Conclusions: CD8+ Trm cells in the human lung display innate-like gene and protein expression that demonstrates blur
Felt SA, Sun Y, Jozwik A, et al., 2021, Detection of respiratory syncytial virus defective genomes in nasal secretions is associated with distinct clinical outcomes, Nature Microbiology, Vol: 6, Pages: 672-681, ISSN: 2058-5276
Respiratory syncytial virus (RSV) causes respiratory illness in children, immunosuppressed individuals and the elderly. However, the viral factors influencing the clinical outcome of RSV infections remain poorly defined. Defective viral genomes (DVGs) can suppress virus replication by competing for viral proteins and by stimulating antiviral immunity. We studied the association between detection of DVGs of the copy-back type and disease severity in three RSV A-confirmed cohorts. In hospitalized children, detection of DVGs in respiratory samples at or around the time of admission associated strongly with more severe disease, higher viral load and a stronger pro-inflammatory response. Interestingly, in experimentally infected adults, the presence of DVGs in respiratory secretions differentially associated with RSV disease severity depending on when DVGs were detected. Detection of DVGs early after infection associated with low viral loads and mild disease, whereas detection of DVGs late after infection, especially if DVGs were present for prolonged periods, associated with high viral loads and severe disease. Taken together, we demonstrate that the kinetics of DVG accumulation and duration could predict clinical outcome of RSV A infection in humans, and thus could be used as a prognostic tool to identify patients at risk of worse clinical disease.
Thwaites RS, Sanchez Sevilla Uruchurtu A, Siggins MK, et al., 2021, Inflammatory profiles across the spectrum of disease reveal a distinct role for GM-CSF in severe COVID-19, Science Immunology, Vol: 6, Pages: 1-17, ISSN: 2470-9468
While it is now widely accepted that host inflammatory responses contribute to lung injury, the pathways that drive severity and distinguish coronavirus disease 2019 (COVID-19) from other viral lung diseases remain poorly characterized. We analyzed plasma samples from 471 hospitalized patients recruited through the prospective multicenter ISARIC4C study and 39 outpatients with mild disease, enabling extensive characterization of responses across a full spectrum of COVID-19 severity. Progressive elevation of levels of numerous inflammatory cytokines and chemokines (including IL-6, CXCL10, and GM-CSF) were associated with severity and accompanied by elevated markers of endothelial injury and thrombosis. Principal component and network analyses demonstrated central roles for IL-6 and GM-CSF in COVID-19 pathogenesis. Comparing these profiles to archived samples from patients with fatal influenza, IL-6 was equally elevated in both conditions whereas GM-CSF was prominent only in COVID-19. These findings further identify the key inflammatory, thrombotic, and vascular factors that characterize and distinguish severe and fatal COVID-19.
Habibi MS, Thwaites RS, Chang M, et al., 2020, Neutrophilic inflammation in the respiratory mucosa predisposes to RSV infection., Science, Vol: 370
The variable outcome of viral exposure is only partially explained by known factors. We administered respiratory syncytial virus (RSV) to 58 volunteers, of whom 57% became infected. Mucosal neutrophil activation before exposure was highly predictive of symptomatic RSV disease. This was associated with a rapid, presymptomatic decline in mucosal interleukin-17A (IL-17A) and other mediators. Conversely, those who resisted infection showed presymptomatic activation of IL-17- and tumor necrosis factor-related pathways. Vulnerability to infection was not associated with baseline microbiome but was reproduced in mice by preinfection chemokine-driven airway recruitment of neutrophils, which caused enhanced disease mediated by pulmonary CD8+ T cell infiltration. Thus, mucosal neutrophilic inflammation at the time of RSV exposure enhances susceptibility, revealing dynamic, time-dependent local immune responses before symptom onset and explaining the as-yet unpredictable outcomes of pathogen exposure.
Guvenel A, Jozwik A, Ascough S, et al., 2020, Epitope-specific airway-resident CD4+ T-cell dynamics during experimental human RSV infection, Journal of Clinical Investigation, Vol: 130, Pages: 523-538, ISSN: 0021-9738
Background: Respiratory syncytial virus (RSV) is an important cause of acute pulmonary disease and one of the last remaining major infections of childhood for which there is no vaccine. CD4+ T-cells play a key role in antiviral immunity, but they have been little studied in the human lung. Methods: Healthy adult volunteers were inoculated intranasally with RSV A Memphis 37. CD4+ T-cells in blood and lower airway were analysed by flow cytometry and immunohistochemistry. Bronchial soluble mediators were measured using quantitative PCR and MesoScale Discovery. Epitope mapping was performed by IFN-γ ELISpot screening, confirmed by in vitro MHC binding. Results: Activated CD4+ T-cell frequencies in bronchoalveolar lavage correlated strongly with local CXCL10 levels. Thirty-nine epitopes were identified, predominantly towards the 3’ end of the viral genome. Five novel MHC-II tetramers were made using an immunodominant F-EFY epitope restricted to HLA-DR4, -DR9 and -DR11 (combined allelic frequency: 15% in Europeans) and G- DDF restricted to HLA-DPA1*01:03/DPB1*02:01 and -DPA1*01:03/DPB1*04:01 (allelic frequency: 55%). Tetramer labelling revealed enrichment of resident memory CD4+ T-cells (TRM) cells in the lower airway; these TRM displayed progressive differentiation, down-regulation of co- stimulatory molecules and elevated CXCR3 expression as infection evolved. Conclusion: Human infection challenge provides a unique opportunity to study the breadth of specificity and dynamics of RSV-specific T-cell responses in the target organ, allowing the precise investigation of TRM recognising novel viral antigens over time. The new tools that we describe enable precise tracking of RSV-specific CD4+ cells, potentially accelerating the development of effective vaccines.
Holzer B, Morgan SB, Martini V, et al., 2019, Immunogenicity and protective efficacy of seasonal human live attenuated cold-adapted influenza virus vaccine in pigs, Frontiers in Immunology, Vol: 10, Pages: 1-13, ISSN: 1664-3224
Influenza A virus infection is a global health threat to livestock and humans, causing substantial mortality and morbidity. As both pigs and humans are readily infected with influenza viruses of similar subtype, the pig is a robust and appropriate model for investigating swine and human disease. We evaluated the efficacy of the human cold-adapted 2017–2018 quadrivalent seasonal LAIV in pigs against H1N1pdm09 challenge. LAIV immunized animals showed significantly reduced viral load in nasal swabs. There was limited replication of the H1N1 component of the vaccine in the nose, a limited response to H1N1 in the lung lymph nodes and a low H1N1 serum neutralizing titer. In contrast there was better replication of the H3N2 component of the LAIV, accompanied by a stronger response to H3N2 in the tracheobronchial lymph nodes (TBLN). Our data demonstrates that a single administration of human quadrivalent LAIV shows limited replication in the nose and induces detectable responses to the H1N1 and H3N2 components. These data suggest that pigs may be a useful model for assessing LAIV against influenza A viruses.
Ascough S, Vlachantoni I, Kalyan M, et al., 2019, Local and systemic immunity against RSV induced by a novel intranasal vaccine: A randomised, double- blind, placebo-controlled trial, American Journal of Respiratory and Critical Care Medicine, Vol: 200, Pages: 481-492, ISSN: 1073-449X
RATIONALE: Needle-free intranasal vaccines offer major potential advantages, especially against pathogens entering via mucosal surfaces. As yet, there is no effective vaccine against respiratory syncytial virus (RSV), a ubiquitous pathogen of global importance that preferentially infects respiratory epithelial cells; new strategies are urgently required. OBJECTIVES: Here, we report the safety and immunogenicity of a novel mucosal RSV F protein vaccine linked to an immunostimulatory bacterium-like particle (BLP). METHODS: In this phase I, randomised, double-blind placebo-controlled trial, 48 healthy volunteers aged 18-49 years were randomly assigned to receive placebo or SynGEM (low- or high-dose) intranasally by prime-boost administration. The primary outcome was safety and tolerability, with secondary objectives assessing virus-specific immunogenicity. MEASUREMENTS AND MAIN RESULTS: There were no significant differences in adverse events between placebo and vaccinated groups. SynGEM induced systemic plasmablast responses and significant, durable increases in RSV-specific serum antibody in healthy seropositive adults. Volunteers given low-dose SynGEM (140 µg F, 2mg BLP) required a boost at day 28 to achieve plateau responses with a maximum fold-change of 2.4, whereas high-dose recipients (350 µg F, 5mg BLP) achieved plateau responses with a fold-change of 1.5 after first vaccination that remained elevated up to 180 days post-vaccination irrespective of further boosting. Palivizumab-like antibodies were consistently induced, but F protein site Ø-specific antibodies were not detected and virus-specific nasal IgA responses were heterogeneous, with strongest responses in individuals with lower pre-existing antibody levels. CONCLUSIONS: SynGEM is thus the first non-replicating intranasal RSV subunit vaccine to induce persistent antibody responses in human volunteers. Clinical trial registration available at www.clinicaltrials.gov, ID NCT02958540.
Fourati S, Taa A, Mahmoudian M, et al., 2018, A crowdsourced analysis to identify ab initio molecular signatures predictive of susceptibility to viral infection, Nature Communications, Vol: 9, Pages: 1-11, ISSN: 2041-1723
The response to respiratory viruses varies substantially between individuals, and there are currently no known molecular predictors from the early stages of infection. Here we conduct a community-based analysis to determine whether pre- or early post-exposure molecular factors could predict physiologic responses to viral exposure. Using peripheral blood gene expression profiles collected from healthy subjects prior to exposure to one of four respiratory viruses (H1N1, H3N2, Rhinovirus, and RSV), as well as up to 24 h following exposure, we find that it is possible to construct models predictive of symptomatic response using profiles even prior to viral exposure. Analysis of predictive gene features reveal little overlap among models; however, in aggregate, these genes are enriched for common pathways. Heme metabolism, the most significantly enriched pathway, is associated with a higher risk of developing symptoms following viral exposure. This study demonstrates that pre-exposure molecular predictors can be identified and improves our understanding of the mechanisms of response to respiratory viruses.
Ascough SC, Paterson S, Chiu C, 2018, Induction and subversion of human protective immunity: contrasting influenza and respiratory syncytial virus, Frontiers in Immunology, Vol: 9, ISSN: 1664-3224
Respiratory syncytial virus (RSV) and influenza are among the most important causes of severe respiratory disease worldwide. Despite the clinical need, barriers to developing reliably effective vaccines against these viruses have remained firmly in place for decades. Overcoming these hurdles requires better understanding of human immunity and the strategies by which these pathogens evade it. Although superficially similar, the virology and host response to RSV and influenza are strikingly distinct. Influenza induces robust strain-specific immunity following natural infection, although protection by current vaccines is short-lived. In contrast, even strain-specific protection is incomplete after RSV and there are currently no licensed RSV vaccines. Although animal models have been critical for developing a fundamental understanding of antiviral immunity, extrapolating to human disease has been problematic. It is only with recent translational advances (such as controlled human infection models and high-dimensional technologies) that the mechanisms responsible for differences in protection against RSV compared to influenza have begun to be elucidated in the human context. Influenza infection elicits high-affinity IgA in the respiratory tract and virus-specific IgG, which correlates with protection. Long-lived influenza-specific T cells have also been shown to ameliorate disease. This robust immunity promotes rapid emergence of antigenic variants leading to immune escape. RSV differs markedly, as reinfection with similar strains occurs despite natural infection inducing high levels of antibody against conserved antigens. The immunomodulatory mechanisms of RSV are thus highly effective in inhibiting long-term protection, with disturbance of type I interferon signaling, antigen presentation and chemokine-induced inflammation possibly all contributing. These lead to widespread effects on adaptive immunity with impaired B cell memory and reduced T cell generation and funct
Vlachantoni I, Ascough S, Grimaldi R, et al., 2017, PHASE 1 TRIAL OF AN INTRANASAL RESPIRATORY SYNCYTIAL VIRUS (RSV) SUBUNIT CANDIDATE VACCINE: SAFETY RESULTS FROM THE MUC-SYNGEM STUDY, Winter Meeting of the British-Thoracic-Society, Publisher: BMJ PUBLISHING GROUP, Pages: A43-A44, ISSN: 0040-6376
Turner RD, Chiu C, Churchyard GJ, et al., 2017, Tuberculosis Infectiousness and Host Susceptibility, Journal of Infectious Disease, Vol: 216, Pages: S636-S643, ISSN: 1537-6613
The transmission of tuberculosis is complex. Necessary factors include a source case with respiratory disease that has developed sufficiently for Mycobacterium tuberculosis to be present in the airways. Viable bacilli must then be released as an aerosol via the respiratory tract of the source case. This is presumed to occur predominantly by coughing but may also happen by other means. Airborne bacilli must be capable of surviving in the external environment before inhalation into a new potential host—steps influenced by ambient conditions and crowding and by M. tuberculosis itself. Innate and adaptive host defenses will then influence whether new infection results; a process that is difficult to study owing to a paucity of animal models and an inability to measure infection directly. This review offers an overview of these steps and highlights the many gaps in knowledge that remain.
Li S, Sullivan NL, Rouphael N, et al., 2017, Metabolic Phenotypes of response to vaccination in humans., Cell, Vol: 169, Pages: 862-877.e17, ISSN: 0092-8674
Herpes zoster (shingles) causes significant morbidity in immune compromised hosts and older adults. Whereas a vaccine is available for prevention of shingles, its efficacy declines with age. To help to understand the mechanisms driving vaccinal responses, we constructed a multiscale, multifactorial response network (MMRN) of immunity in healthy young and older adults immunized with the live attenuated shingles vaccine Zostavax. Vaccination induces robust antigen-specific antibody, plasmablasts, and CD4(+) T cells yet limited CD8(+) T cell and antiviral responses. The MMRN reveals striking associations between orthogonal datasets, such as transcriptomic and metabolomics signatures, cell populations, and cytokine levels, and identifies immune and metabolic correlates of vaccine immunity. Networks associated with inositol phosphate, glycerophospholipids, and sterol metabolism are tightly coupled with immunity. Critically, the sterol regulatory binding protein 1 and its targets are key integrators of antibody and T follicular cell responses. Our approach is broadly applicable to study human immunity and can help to identify predictors of efficacy as well as mechanisms controlling immunity to vaccination.
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.
Chiu C, 2017, Novel immunological insights in accelerating RSV vaccine development, Vaccine, Vol: 35, Pages: 459-460, ISSN: 0264-410X
Habibi MS, Chiu C, 2016, Controlled human infection with RSV: the opportunities of experimental challenge, Vaccine, Vol: 35, Pages: 489-495, ISSN: 1873-2518
Despite the recent explosion in RSV vaccine development, there remain substantial hurdles to overcome before licensing of effective vaccines will allow widespread use, particularly in high-risk populations. Incomplete understanding of mechanisms and correlates of protection against RSV mean that, for the time being, successful RSV vaccines must directly demonstrate efficacy, which necessitates large and costly clinical trials in naturally infected patients. To mitigate the risks inherent in progressing to these late-stage trials, experimental human RSV infection studies have recently been re-established, representing the interface between pre-clinical models and observational studies of patients. Not only can they be used for early proof-of-concept clinical trials to test vaccine efficacy, but human challenge studies also offer the potential to better understand protective immunity against RSV infection to improve vaccine design and delivery. In the past, controlled human infection studies with RSV have been instrumental in elucidating the influence of factors such as route of infection and type of inoculum on the course of disease. Recently, efficacy trials of novel RSV antiviral drugs have also been successfully undertaken. Now, with advances in technology, detailed investigations of human mucosal immunity in the RSV-infected airway are possible. These have indicated defects in RSV-induced humoral and CD8+ T cell immunity that may contribute to the recurrent symptomatic infection that occurs throughout life and should be circumvented by optimal vaccines. Here, we discuss the insights derived from RSV human challenge models; the major impediments to their more widespread uptake; and their potential benefit in accelerating vaccine development, including future directions to further enhance the relevance of these models to at-risk patient populations.
Chiu C, 2016, Seasonal influenza vaccines and hurdles to mutual protection, Clinical Microbiology and Infection, Vol: 22, Pages: S113-S119, ISSN: 1469-0691
While vaccines against seasonal influenza are available, major hurdles still exist that prevent their use having any impact on epidemic spread. Recent epidemiologic data question the appropriateness of traditional vaccination timing (prior to the winter season) in many parts of the world. Furthermore, vaccine uptake in most countries even in high-risk populations does not reach the 75% target recommended by the World Health Organization. Influenza viruses continually undergo antigenic variation, and both inactivated and live attenuated influenza vaccines confer only short-lived strain-specific immunity, so annual revaccination is required. Improving vaccine-induced immunity is therefore an important goal. A vaccine that could confer durable protection against emerging influenza strains could significantly reduce onward transmission. Therefore, further understanding of protective immunity against influenza (including broadly cross-protective immune mechanisms such as haemagglutinin stem-binding antibodies and T cells) offers the hope of vaccines that can confer the long-lived heterosubtypic immune responses required for mutual protection.
Jozwik A, Habibi MS, Paras A, et al., 2016, Erratum: RSV-specific airway resident memory CD8+ T cells and differential disease severity after experimental human infection, Nature Communications, Vol: 7, ISSN: 2041-1723
Currie SM, Findlay EG, McFarlane AJ, et al., 2016, Cathelicidins have direct antiviral activity against respiratory syncytial virus in vitro and protective function in vivo in mice and humans, Journal of Immunology, Vol: 196, Pages: 2699-2710, ISSN: 1550-6606
Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infection in infants, causing significant morbidity and mortality. No vaccine or specific, effective treatment is currently available. A more complete understanding of the key components of effective host response to RSV and novel preventative and therapeutic interventions are urgently required. Cathelicidins are host defense peptides, expressed in the inflamed lung, with key microbicidal and modulatory roles in innate host defense against infection. In this article, we demonstrate that the human cathelicidin LL-37 mediates an antiviral effect on RSV by inducing direct damage to the viral envelope, disrupting viral particles and decreasing virus binding to, and infection of, human epithelial cells in vitro. In addition, exogenously applied LL-37 is protective against RSV-mediated disease in vivo, in a murine model of pulmonary RSV infection, demonstrating maximal efficacy when applied concomitantly with virus. Furthermore, endogenous murine cathelicidin, induced by infection, has a fundamental role in protection against disease in vivo postinfection with RSV. Finally, higher nasal levels of LL-37 are associated with protection in a healthy human adult RSV infection model. These data lead us to propose that cathelicidins are a key, nonredundant component of host defense against pulmonary infection with RSV, functioning as a first point of contact antiviral shield and having additional later-phase roles in minimizing the severity of disease outcome. Consequently, cathelicidins represent an inducible target for preventative strategies against RSV infection and may inform the design of novel therapeutic analogs for use in established infection.
Jozwik A, Habibi MS, Paras A, et al., 2015, RSV-specific airway resident memory CD8+ T cells and differential disease severity after experimental human infection, Nature Communications, Vol: 6, Pages: 1-17, ISSN: 2041-1723
In animal models, resident memory CD8+ T (Trm) cells assist in respiratory virus elimination but their importance in man has not been determined. Here, using experimental human respiratory syncytial virus (RSV) infection, we investigate systemic and local virus-specific CD8+ T cell responses in adult volunteers. Having defined the immunodominance hierarchy, we analyze phenotype and function longitudinally in blood and by serial bronchoscopy. Despite rapid clinical recovery, we note surprisingly extensive lower airway inflammation with persistent viral antigen and cellular infiltrates. Pulmonary virus-specific CD8+ T cells display a CD69+CD103+ Trm phenotype and accumulate to strikingly high frequencies into convalescence without continued proliferation. These are more highly differentiated but express fewer cytotoxicity markers than in blood, but their abundance prior to infection correlates with protection from more severe disease.
Habibi MS, Jozwik A, Makris S, et al., 2015, Impaired antibody-mediated protection and defective IgA B cell memory in experimental infection of adults with respiratory syncytial virus, American Journal of Respiratory and Critical Care Medicine, Vol: 191, ISSN: 1535-4970
Rationale: Despite relative antigenic stability, respiratory syncytial virus (RSV) re-infects throughout life. After >40 years of research, no effective human vaccine exists and correlates of protection remain poorly defined. Most current vaccine candidates seek to induce high levels of RSV-specific serum neutralizing antibodies, which are associated with reduced RSV-related hospitalization rates in observational studies but may not actually prevent infection. Objectives: Characterize correlates of protection from infection and the generation of RSV-specific humoral memory to promote effective vaccine development. Methods: We inoculated 61 healthy adults with live RSV and studied protection from infection by serum and mucosal antibody. We analyzed RSV-specific peripheral blood plasmablast and memory B cell frequencies and antibody longevity. Measurements and Main Results: Despite moderately high levels of pre-existing serum antibody, 34 (56%) became infected, of whom 23 (68%) developed symptomatic colds. Prior RSV-specific nasal IgA correlated significantly more strongly with protection from PCR-confirmed infection than serum neutralizing antibody. Increases in virus-specific antibody titers were variable and transient in infected subjects, but correlated with plasmablasts that peaked around day 10. During convalescence, only IgG (and no IgA) RSV-specific memory B cells were detectable in peripheral blood. This contrasted with natural influenza infection, where virus-specific IgA memory B cells were readily recovered. Conclusions: This observed specific defect in IgA memory may partly explain RSV's ability to cause recurrent symptomatic infections. If so, vaccines able to induce durable RSV-specific IgA responses may be more protective than those generating systemic antibody alone.
Chiu C, Ellebedy AH, Wrammert J, et al., 2015, B Cell Responses to Influenza Infection and Vaccination, INFLUENZA PATHOGENESIS AND CONTROL - VOL II, Vol: 386, Pages: 381-398, ISSN: 0070-217X
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