Characterization of Respiratory Syncytial Virus M- and M2-Specific CD4 T Cells in a Murine Model

Vaccine Research Center, NIAID, National Institutes of Health, 40 Convent Dr., Bethesda, MD 20892-3017, USA.
Journal of Virology (Impact Factor: 4.44). 04/2009; 83(10):4934-41. DOI: 10.1128/JVI.02140-08
Source: PubMed


CD4 T cells have been shown to play an important role in the immunity and immunopathogenesis of respiratory syncytial virus (RSV) infection. We identified two novel CD4 T-cell epitopes in the RSV M and M2 proteins with core sequences M(213-223) (FKYIKPQSQFI) and M2(27-37) (YFEWPPHALLV). Peptides containing the epitopes stimulated RSV-specific CD4 T cells to produce gamma interferon (IFN-gamma), interleukin 2 (IL-2), and other Th1- and Th2-type cytokines in an I-A(b)-restricted pattern. Construction of fluorochrome-conjugated peptide-I-A(b) class II tetramers revealed RSV M- and M2-specific CD4 T-cell responses in RSV-infected mice in a hierarchical pattern. Peptide-activated CD4 T cells from lungs were more activated and differentiated, and had greater IFN-gamma expression, than CD4 T cells from the spleen, which, in contrast, produced greater levels of IL-2. In addition, M(209-223) peptide-activated CD4 T cells reduced IFN-gamma and IL-2 production in M- and M2-specific CD8 T-cell responses to D(b)-M(187-195) and K(d)-M2(82-90) peptides more than M2(25-39) peptide-stimulated CD4 T cells. This correlated with the fact that I-A(b)-M(209-223) tetramer-positive cells responding to primary RSV infection had a much higher frequency of FoxP3 expression than I-A(b)-M2(26-39) tetramer-positive CD4 T cells, suggesting that the M-specific CD4 T-cell response has greater regulatory function. Characterization of epitope-specific CD4 T cells by novel fluorochrome-conjugated peptide-I-A(b) tetramers allows detailed analysis of their roles in RSV pathogenesis and immunity.

Download full-text


Available from: Teresa R. Johnson,
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The respiratory system forms a major mucosal interface with the external environment. Consequently, the respiratory tract is constantly exposed to inhaled foreign antigens, commensal microorganisms, and potential pathogens. The respiratory system has evolved a complex regulatory network designed to prevent unnecessary inflammation to harmless antigens and to limit immune-mediated damage to the fragile lung epithelium in response to infection. The lung maintains a default anti-inflammatory state that is coordinated by the respiratory epithelium, alveolar macrophages, dendritic cells, and regulatory Foxp3+ CD4 T cells (Tregs). It is likely that all of these cells influence the development of pathogen-specific T cell responses in the lung. Following infection with a respiratory virus, virus-specific CD8 T cells in the lung are inhibited in their ability to produce cytokines. Current studies suggest that this functional inactivation occurs following infection with respiratory viruses within the Paramyxoviridae family. The data presented here demonstrate that suppression of effector functions of virus-specific CD8 T cells in the lungs occurs following infection with several unrelated respiratory viruses. These results indicate that the functional inhibition of virus-specific T cell responses is not restricted to infection with viruses from the Paramyxoviridae family. Furthermore, I show data indicating that the functional inactivation of virus-specific CD8 T cells in the lungs occurs in the absence of infection. I also demonstrate for the first time that the lung environment also regulates the effector functions of virus-specific CD4 T cells. Inhibition of cytokine production by pulmonary T cells is reversible as stimulation with exogenous peptide-pulsed antigen-presenting cells rescues IFN-gamma production. The inhibition of IFN-gamma production by virus-specific T cells occurs in other organs such as the kidney. These data suggest that regulation of T cell cytokine production by peripheral tissues may serve as an important mechanism to prevent immunopathology and preserve normal tissue function. Foxp3+ Tregs have been shown to inhibit conventional effector T cell responses in a large number of chronic infection models. However, their role during acute infections remains unclear. Examination of Foxp3+ Tregs during RSV infection showed that Tregs are rapidly recruited into the lungs and acquire an activated phenotype. Depletion of Foxp3+ Tregs prior to RSV infection revealed that Tregs facilitate the early recruitment of RSV-specific CD8 T cells from the draining lymph nodes to the lung and later limit the overall magnitude of the virus-specific CD8 T cell response. Depletion of Tregs increased TNF-αa production by RSV-specific CD8 T cells and enhanced T-cell-mediated immunopathology. These data demonstrate that Foxp3+ Tregs play a major role in regulating CD8 T cell responses to respiratory virus infections. Collectively, the data presented here demonstrate that CD8 T cell responses to respiratory pathogens are tightly regulated within the lung environment.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Worldwide, respiratory syncytial virus (RSV) causes severe bronchiolitis and pneumonia in children, the elderly and immuno-compromised individuals. Moreover, RSV is the mayor cause of infant hospitalization due to lower respiratory infection, regardless socioeconomic status. Accumulating data support the notion that immune responses elicited against naturally acquired RSV infections are non-lasting and inappropriate for efficient virus clearance. Although there is consensus over the capacity of RSV to impair the development of an effective and protective adaptive immune response, very little is known about specific viral determinants involved in these processes as well as the molecular mechanisms developed by this virus to inhibit T cell function. Recent studies have provided evidence supporting an important role for dendritic cells in RSV-induced suppression of immunity. Although recognized for over 50 years as an important respiratory pathogen and healthcare problem, to date there are no available vaccines against this virus, which highlights the complexity of RSV-induced immunopathology. The development of new prophylactic and therapeutic tools against RSV requires the unveiling of molecular mechanisms and virulence factors responsible for the pathogenesis caused by this virus. In this review, we discuss recent findings describing virulence mechanisms evolved by RSV to negatively modulate the adaptive immune response in the host. Furthermore, novel strategies aimed to induce efficient T cell immunity against RSV are reviewed.
    Current Medicinal Chemistry 11/2009; 16(34):4609-4625. DOI:10.2174/092986709789760724 · 3.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The history of vaccines for respiratory syncytial virus (RSV) illustrates the complex immunity and immunopathology to this ubiquitous virus, starting from the failed formalin-inactivated vaccine trials performed in the 1960s. An attractive alternative to traditional live or killed virus vaccines is a defined vaccine composed of discrete antigenic epitopes for which immunological activities have been characterized as comprehensively as possible. Here we present cumulative data on murine and human CD4, CD8 and neutralization epitopes identified in RSV proteins along with information regarding their associated immune responses and host-dependent variability. Identification and characterization of RSV epitopes is a rapidly expanding topic of research with potential contributions to the tailored design of improved safe and effective vaccines.
    Future Microbiology 04/2010; 5(4):585-602. DOI:10.2217/fmb.10.22 · 4.28 Impact Factor
Show more