Long-term maintenance of lung resident memory T cells is mediated by persistent antigen.

Tissue-resident memory T cells (TRM) in the lungs are pivotal for protection against repeated infection with respiratory viruses. However, the gradual loss of these cells over time and the associated decline in clinical protection represent a serious limit in the development of efficient T cell based vaccines against respiratory pathogens. Here, using an adenovirus expressing influenza nucleoprotein (AdNP), we show that CD8 TRM in the lungs can be maintained for at least 1 year post vaccination. Our results reveal that lung TRM continued to proliferate in situ 8 months after AdNP vaccination. Importantly, this required airway vaccination and antigen persistence in the lung, as non-respiratory routes of vaccination failed to support long-term lung TRM maintenance. In addition, parabiosis experiments show that in AdNP vaccinated mice, the lung TRM pool is also sustained by continual replenishment from circulating memory CD8 T cells that differentiate into lung TRM, a phenomenon not observed in influenza-infected parabiont partners. Concluding, these results demonstrate key requirements for long-lived cellular immunity to influenza virus, knowledge that could be utilized in future vaccine design.

Environmental cues regulate epigenetic reprogramming of airway-resident memory CD8+ T cells.

Tissue-resident memory T cells (TRM cells) are critical for cellular immunity to respiratory pathogens and reside in both the airways and the interstitium. In the present study, we found that the airway environment drove transcriptional and epigenetic changes that specifically regulated the cytolytic functions of airway TRM cells and promoted apoptosis due to amino acid starvation and activation of the integrated stress response. Comparison of airway TRM cells and splenic effector-memory T cells transferred into the airways indicated that the environment was necessary to activate these pathways, but did not induce TRM cell lineage reprogramming. Importantly, activation of the integrated stress response was reversed in airway TRM cells placed in a nutrient-rich environment. Our data defined the genetic programs of distinct lung TRM cell populations and show that local environmental cues altered airway TRM cells to limit cytolytic function and promote cell death, which ultimately leads to fewer TRM cells in the lung.

Pulmonary monocytes interact with effector T cells in the lung tissue to drive TRM differentiation following viral infection.

Lung resident memory CD8 T cells (TRM) are critical for protection against respiratory viruses, but the cellular interactions required for their development are poorly understood. Herein we describe the necessity of classical monocytes for the establishment of lung TRM following influenza infection. We find that, during the initial appearance of lung TRM, monocytes and dendritic cells are the most numerous influenza antigen-bearing APCs in the lung. Surprisingly, depletion of DCs after initial T cell priming did not impact lung TRM development or maintenance. In contrast, a monocyte deficient pulmonary environment in CCR2-/- mice results in significantly less lung TRM following influenza infection, despite no defect in the antiviral effector response or in the peripheral memory pool. Imaging shows direct interaction of antigen-specific T cells with antigen-bearing monocytes in the lung, and pulmonary classical monocytes from the lungs of influenza infected mice are sufficient to drive differentiation of T cells in vitro. These data describe a novel role for pulmonary monocytes in mediating lung TRM development through direct interaction with T cells in the lung.

CXCR6 regulates localization of tissue-resident memory CD8 T cells to the airways.

Resident memory T cells (TRM cells) are an important first-line defense against respiratory pathogens, but the unique contributions of lung TRM cell populations to protective immunity and the factors that govern their localization to different compartments of the lung are not well understood. Here, we show that airway and interstitial TRM cells have distinct effector functions and that CXCR6 controls the partitioning of TRM cells within the lung by recruiting CD8 TRM cells to the airways. The absence of CXCR6 significantly decreases airway CD8 TRM cells due to altered trafficking of CXCR6-/- cells within the lung, and not decreased survival in the airways. CXCL16, the ligand for CXCR6, is localized primarily at the respiratory epithelium, and mice lacking CXCL16 also had decreased CD8 TRM cells in the airways. Finally, blocking CXCL16 inhibited the steady-state maintenance of airway TRM cells. Thus, the CXCR6/CXCL16 signaling axis controls the localization of TRM cells to different compartments of the lung and maintains airway TRM cells.

Pulmonary antigen encounter regulates the establishment of tissue-resident CD8 memory T cells in the lung airways and parenchyma.

Resident memory CD8 T (TRM) cells in the lung parenchyma (LP) and airways provide heterologous protection against influenza virus challenge. However, scant knowledge exists regarding factors necessary to establish and maintain lung CD8 TRM. Here we demonstrate that, in contrast to mechanisms described for other tissues, airway, and LP CD8 TRM establishment requires cognate antigen recognition in the lung. Systemic effector CD8 T cells could be transiently pulled into the lung in response to localized inflammation, however these effector cells failed to establish tissue residency unless antigen was present in the pulmonary environment. The interaction of effector CD8 T cells with cognate antigen in the lung resulted in increased and prolonged expression of the tissue-retention markers CD69 and CD103, and increased expression of the adhesion molecule VLA-1. The inability of localized inflammation alone to establish lung TRM resulted in decreased viral clearance and increased mortality following heterosubtypic influenza challenge, despite equal numbers of circulating memory CD8 T cells. These findings demonstrate that pulmonary antigen encounter is required for the establishment of lung CD8 TRM and may inform future vaccine strategies to generate robust cellular immunity against respiratory pathogens.

Mathematical Model Reveals the Role of Memory CD8 T Cell Populations in Recall Responses to Influenza.

The current influenza vaccine provides narrow protection against the strains included in the vaccine, and needs to be reformulated every few years in response to the constantly evolving new strains. Novel approaches are directed toward developing vaccines that provide broader protection by targeting B and T cell epitopes that are conserved between different strains of the virus. In this paper, we focus on developing mathematical models to explore the CD8 T cell responses to influenza, how they can be boosted, and the conditions under which they contribute to protection. Our models suggest that the interplay between spatial heterogeneity (with the virus infecting the respiratory tract and the immune response being generated in the secondary lymphoid organs) and T cell differentiation (with proliferation occurring in the lymphoid organs giving rise to a subpopulation of resident T cells in the respiratory tract) is the key to understand the dynamics of protection afforded by the CD8 T cell response to influenza. Our results suggest that the time lag for the generation of resident T cells in the respiratory tract and their rate of decay following infection are the key factors that limit the efficacy of CD8 T cell responses. The models predict that an increase in the level of central memory T cells leads to a gradual decrease in the viral load, and, in contrast, there is a sharper protection threshold for the relationship between the size of the population of resident T cells and protection. The models also suggest that repeated natural influenza infections cause the number of central memory CD8 T cells and the peak number of resident memory CD8 T cells to reach their plateaus, and while the former is maintained, the latter decays with time since the most recent infection.

Inclusion of Flagellin during Vaccination against Influenza Enhances Recall Responses in Nonhuman Primate Neonates.

UNLABELLED: Influenza virus can cause life-threatening infections in neonates and young infants. Although vaccination is a major countermeasure against influenza, current vaccines are not approved for use in infants less than 6 months of age, in part due to the weak immune response following vaccination. Thus, there is a strong need to develop new vaccines with improved efficacy for this vulnerable population. To address this issue, we established a neonatal African green monkey (AGM) nonhuman primate model that could be used to identify effective influenza vaccine approaches for use in young infants. We assessed the ability of flagellin, a Toll-like receptor 5 (TLR5) agonist, to serve as an effective adjuvant in this at-risk population. Four- to 6-day-old AGMs were primed and boosted with inactivated PR8 influenza virus (IPR8) adjuvanted with either wild-type flagellin or inactive flagellin with a mutation at position 229 (m229), the latter of which is incapable of signaling through TLR5. Increased IgG responses were observed following a boost, as well as at early times after challenge, in infants vaccinated with flagellin-adjuvanted IPR8. Inclusion of flagellin during vaccination also resulted in a significantly increased number of influenza virus-specific T cells following challenge compared to the number in infants vaccinated with the m229 adjuvant. Finally, following challenge infants vaccinated with IPR8 plus flagellin exhibited a reduced pathology in the lungs compared to that in infants that received IPR8 plus m229. This study provides the first evidence of flagellin-mediated enhancement of vaccine responses in nonhuman primate neonates. IMPORTANCE: Young infants are particularly susceptible to severe disease as a result of influenza virus infection. Compounding this is the lack of effective vaccines for use in this vulnerable population. Here we describe a vaccine approach that results in improved immune responses and protection in young infants. Incorporation of flagellin during vaccination resulted in increased antibody and T cell responses together with reduced disease following virus infection. These results suggest that flagellin may serve as an effective adjuvant for vaccines targeted to this vulnerable population.

Nonhuman primate infants have an impaired respiratory but not systemic IgG antibody response following influenza virus infection.

Respiratory infection of young infants results in increased morbidity and mortality compared to infection of adults. In spite of the significance of this health issue, our understanding of the immune response elicited in infants especially in the respiratory tract is highly limited. We developed a nonhuman primate model to probe the virus-specific antibody response in infants following infection with influenza virus. Infection of infants resulted in more pulmonary damage and higher viral loads compared to adults. While the systemic IgG antibody response was similar in infant and adult animals, the response in the upper respiratory tract of the infant was compromised. This lower response was associated with an increased prevalence of Treg cells and low levels of BALT. These data suggest a defect in the ability to produce effective virus-specific antibody responses at the local infection site is a contributor to increased pulmonary damage in the at-risk infant population.

Coinfection with Streptococcus pneumoniae negatively modulates the size and composition of the ongoing influenza-specific CD8⁺ T cell response.

Infection with influenza A virus can lead to increased susceptibility to subsequent bacterial infection, often with Streptococcus pneumoniae. Given the substantial modification of the lung environment that occurs following pathogen infection, there is significant potential for modulation of immune responses. In this study, we show that infection of mice with influenza virus, followed by the noninvasive EF3030 strain of Streptococcus pneumoniae, leads to a significant decrease in the virus-specific CD8(+) T cell response in the lung. Adoptive-transfer studies suggest that this reduction contributes to disease in coinfected animals. The reduced number of lung effector cells in coinfected animals was associated with increased death, as well as a reduction in cytokine production in surviving cells. Further, cells that retained the ability to produce IFN-γ exhibited a decreased potential for coproduction of TNF-α. Reduced cytokine production was directly correlated with a decrease in the level of mRNA. Negative regulation of cells in the mediastinal lymph node was minimal compared with that present in the lung, supporting a model of selective regulation in the tissue harboring high pathogen burden. These results show that entry of a coinfecting pathogen can have profound immunoregulatory effects on an ongoing immune response. Together, these findings reveal a novel dynamic interplay between concurrently infecting pathogens and the adaptive immune system.

Respiratory syncytial virus regulates human microRNAs by using mechanisms involving beta interferon and NF-κB.

UNLABELLED: Respiratory syncytial virus (RSV) is the most common viral cause of severe lower respiratory tract illness in infants and children. The virus replicates in polarized epithelial cells in the airway and, to a lesser extent, infects airway antigen-presenting cells, such as dendritic cells (DCs). RSV possesses a number of expressed genes that antagonize the effect of type I interferons and other related host factor pathways that inhibit replication efficiency. Virus infection alters host gene transcription and the translation of host transcripts through specific antagonism of the function of host proteins, through induction of RNA stress granules, and through induction of altered patterns of host gene expression. In healthy cells, microRNAs (miRNAs) regulate gene expression by targeting the noncoding region of mRNA molecules to cause silencing or degradation of transcripts. It is not known whether or not RSV infection alters the level of microRNAs in cells. We profiled the pattern of expression of host cell microRNAs in RSV-infected epithelial cells or DCs and found that RSV did alter microRNA expression but in a cell-type-specific manner. The studies showed that let-7b was upregulated in DCs, while let-7i and miR-30b were upregulated in epithelial cells in a process that required viral replication. Interestingly, we found that the RSV nonstructural genes NS1 and NS2 antagonized the upregulation of let-7i and miR-30b. RSV appears to manipulate host cell gene expression through regulation of expression of miRNAs related to the interferon response. The data suggest a new mechanism of virus-host cell interactions for paramyxoviruses. IMPORTANCE: Respiratory syncytial virus (RSV) is the most common cause of serious lower respiratory tract illness in infants and children. The human innate immune response inhibits RSV replication early after inoculation, principally through the effect of substances called interferons. The virus, however, has developed several mechanisms for counteracting the host innate immune response. It is not known whether or not RSV infection alters the expression of host microRNAs, which are short RNA sequences that are posttranscriptional regulators. This paper shows that RSV does induce unique patterns of microRNA expression related to the NF-κB pathway or interferon pathways. The microRNA profiles differed depending on the cell type that was infected, airway cell or antigen-presenting cell. Interestingly, the virus appears to counteract the microRNA response by expressing nonstructural viral genes in the cell that reduce microRNA induction. The data suggest a new way in which paramyxoviruses regulate the host cell response to infection.

A radioligand binding assay to measure anti-thyroperoxidase autoantibodies in mice.

Autoimmune (Hashimoto's) thyroiditis is a chronic inflammatory disease which affects >3% of the population and shows an increasing prevalence with increasing age. Anti-thyroid autoantibodies, particularly against thyroperoxidase (also known as thyroid peroxidase or TPO), occur commonly in humans with autoimmune thyroid disease, and assays for anti-TPO autoantibodies are used in clinical diagnosis. In contrast anti-TPO autoantibodies have not been observed in classical mouse models of autoimmune thyroiditis, except in cases where mice were deliberately immunized with TPO. In the past, detection of anti-TPO autoantibodies in mice has relied on an indirect immunofluorescence assay (iIFA) which screens for thyroid follicle membrane staining in frozen sections of mouse thyroid glands. Since recent transgenic mouse models of autoimmune thyroiditis spontaneously develop anti-TPO autoantibodies, an assay other than serial dilution and iIFA would be useful to detect and quantify these autoantibodies. In this paper we describe such an assay, based on the capacity of autoimmune mouse sera to bind to the extracellular domain of mouse TPO which was produced in a radioactively labeled form using a coupled in vitro transcription/translation system. The same approach, using human TPO, could provide a highly sensitive method to detect anti-TPO autoantibodies in humans.

Innovations in the Ethical Review of Health-Related Quality Improvement and Research: The Alberta Research Ethics Community Consensus Initiative (ARECCI).

The Alberta Research Ethics Community Consensus Initiative (ARECCI) is a unique Canadian initiative that addresses the ethical oversight of two main categories of health-related investigative projects: research and quality improvement (including quality assurance and program evaluation). ARECCI was formed as a result of discussions arising from health regions, health researchers and the Alberta Committee of Research Ethics Boards (REBs) Chairs, who all desired a clearer and more consistent approach to the ethical oversight of investigative health projects. The Alberta Heritage Foundation for Medical Research (AHFMR) established and supported ARECCI in 2003 in response to this need. ARECCI is unique in its ongoing efforts to bring together a wide-ranging group of stakeholders to develop consensus on a set of pragmatic recommendations and tools for the ethical review of research and quality improvement, and to get extensive consultation on those recommendations. This paper presents the ARECCI context and process, recommendations and tools produced by ARECCI and lessons learned from the ongoing ARECCI process.

Networks: better language required.

While networks have proliferated in literature and in our health system, our day-to-day language has not kept up in sophistication. This commentary builds on the work presented by Huerta, Casebeer and VanderPlaat to further explore the language of networks. An expansion of our "network literacy" needs to be reflected in a broader vocabulary for describing particular networks and identifying patterns of relationship that are not appropriately labelled a network. Dimensions along which network managers often understand and place their networks are reported, and the implications of various network images are considered. The distinction between the image of a fishing net and that of a spider's web explores the difference between networks as system substrates and as centres. A moratorium on the term network is called for, to ensure an expanded vocabulary is applied to emerging new relationship patterns between or independent of organizations.

CD4 T cells play major effector role and CD8 T cells initiating role in spontaneous autoimmune myocarditis of HLA-DQ8 transgenic IAb knockout nonobese diabetic mice.

In humans, spontaneous autoimmune attack against cardiomyocytes often leads to idiopathic dilated cardiomyopathy (IDCM) and life-threatening heart failure. HLA-DQ8 transgenic IAb knockout NOD mice (NOD.DQ8/Ab(0); DQA1*0301, DQB1*0302) develop spontaneous anticardiomyocyte autoimmunity with pathology very similar to human IDCM, but why the heart is targeted is unknown. In the present study, we first investigated whether NOD/Ab(0) mice transgenic for a different DQ allele, DQ6, (DQA1*0102, DQB1*0602) would also develop myocarditis. NOD.DQ6/Ab(0) animals showed no cardiac pathology, implying that DQ8 is specifically required for the myocarditis phenotype. To further characterize the cellular immune mechanisms, we established crosses of our NOD.DQ8/Ab(0) animals with Rag1 knockout (Rag1(0)), Ig H chain knockout (IgH(0)), and beta(2)-microglobulin knockout (beta(2)m(0)) lines. Adoptive transfer of purified CD4 T cells from NOD.DQ8/Ab(0) mice with complete heart block (an indication of advanced myocarditis) into younger NOD.DQ8/Ab(0) Rag1(0) animals induced cardiac pathology in all recipients, whereas adoptive transfer of purified CD8 T cells or B lymphocytes had no effect. Despite the absence of B lymphocytes, NOD.DQ8/Ab(0)IgH(0) animals still developed complete heart block, whereas NOD.DQ8/Ab(0)beta(2)m(0) mice (which lack CD8 T cells) failed to develop any cardiac pathology. CD8 T cells (and possibly NK cells) seem to be necessary to initiate disease, whereas once initiated, CD4 T cells alone can orchestrate the cardiac pathology, likely through their capacity to recruit and activate macrophages. Understanding the cellular immune mechanisms causing spontaneous myocarditis/IDCM in this relevant animal model will facilitate the development and testing of new therapies for this devastating disease.

Analysis of known bacterial protein vaccine antigens reveals biased physical properties and amino acid composition.

Many vaccines have been developed from live attenuated forms of bacterial pathogens or from killed bacterial cells. However, an increased awareness of the potential for transient side-effects following vaccination has prompted an increased emphasis on the use of sub-unit vaccines, rather than those based on whole bacterial cells. The identification of vaccine sub-units is often a lengthy process and bioinformatics approaches have recently been used to identify candidate protein vaccine antigens. Such methods ultimately offer the promise of a more rapid advance towards preclinical studies with vaccines. We have compared the properties of known bacterial vaccine antigens against randomly selected proteins and identified differences in the make-up of these two groups. A computer algorithm that exploits these differences allows the identification of potential vaccine antigen candidates from pathogenic bacteria on the basis of their amino acid composition, a property inherently associated with sub-cellular location.

A recombinant carboxy-terminal domain of the protective antigen of Bacillus anthracis protects mice against anthrax infection.

The immunogenicity and protective efficacy of overlapping regions of the protective antigen (PA) polypeptide, cloned and expressed as glutathione S-transferase fusion proteins, have been assessed. Results show that protection can be attributed to individual domains and imply that it is domain 4 which contains the dominant protective epitopes of PA.