• Login
    View Item 
    •   Home
    • UMass Chan Student Research and Publications
    • Morningside Graduate School of Biomedical Sciences
    • Morningside GSBS Dissertations and Theses
    • View Item
    •   Home
    • UMass Chan Student Research and Publications
    • Morningside Graduate School of Biomedical Sciences
    • Morningside GSBS Dissertations and Theses
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of eScholarship@UMassChanCommunitiesPublication DateAuthorsUMass Chan AffiliationsTitlesDocument TypesKeywordsThis CollectionPublication DateAuthorsUMass Chan AffiliationsTitlesDocument TypesKeywordsProfilesView

    My Account

    LoginRegister

    Help

    AboutSubmission GuidelinesData Deposit PolicySearchingUsage StatisticsAccessibilityTerms of UseWebsite Migration FAQ

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    The Virus-Specific CD4+ T Cell Response During Acute Lymphocytic Choriomeningitis Virus Infection and into Long Term Memory: a Dissertation

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Varga_Steven.pdf
    Size:
    8.836Mb
    Format:
    PDF
    Download
    Authors
    Varga, Steven Michael
    Faculty Advisor
    Raymond M. Welsh PhD
    Academic Program
    Immunology and Microbiology
    UMass Chan Affiliations
    Pathology
    Document Type
    Doctoral Dissertation
    Publication Date
    1999-01-01
    Keywords
    Antigens
    CD4
    T-Lymphocytes
    Lymphocytic Choriomeningitis
    Biological Factors
    Cells
    Hemic and Immune Systems
    Viruses
    
    Metadata
    Show full item record
    Abstract
    CD4+ T cells play a central role in immunity. During virus infections, CD4+ T cells provide the necessary help for B cells to secrete anti-viral antibody and may act as effector cells themselves through the secretion of anti-viral cytokines such as IFN-γ and TNF-α. Recent studies in the lymphocytic choriomeningitis virus (LCMV) system have shown that CD4+ T cells are required to maintain the clearance of persistent viral infections as well as maintain virus-specific memory CD8+ cytotoxic T lymphocytes (CTL). Despite these important functions, surprisingly little information exists concerning the longevity, magnitude, and stability of the CD4+ T cell response following a virus infection. This thesis takes advantage of the well-studied LCMV system to address the above issues as well as to examine the role CD4+ T cells play during heterologous virus infections and to determine the fate of CD4+T cells following a high-dose LCMV infection. The cell surface phenotype of the CD4+ T cells was first examined in C57BL/6 mice acutely infected with LCMV. FACS analysis revealed the modulation of several activation markers on CD4+ T cells during an acute infection with LCMV, consistent with an activated cell phenotype. In addition, 25% of the CD4+ T cells were blast-sized by day 7 post-infection (p.i.) even though the total number of CD4+ T cells did not increase in the spleen during the acute infection. Additional studies were performed using CZ-1, a novel monoclonal antibody (mAb) previously generated in our laboratory that defines a sialic acid-dependent CD45RB-associated epitope. Examination of the expression of the CZ-1 antigen on CD4+ T cells following LCMV infection revealed that the blast-sized CD4+ T cells at day 6 p.i. were CZ-1 +. Further cell surface phenotyping showed that those blast cells activated at day 6 p.i. were CD45RB1oCD44hiCD62L-. This contrasts with the CZ-1-CD45RBhiCD441oCD62L+ resting cell population prior to infection. To determine if memory CD4+ T cells continued to express the CZ-1 epitope long after resolution of the LCMV infection, CD4+CZ-1+ and CD4+CZ-1- populations were purified by cell sorting and placed into an in vitro proliferation assay with LCMV-infected antigen-presenting cells (APC). It was found that the CD4+CZ-1+ population contained virtually all of the virus-specific memory. Thus, these studies indicate that the CZ-1 epitope defines a novel activation and memory marker for murine CD4+T cells. Examination of virus-specific cytokine production using ELISPOT assays showed a significant increase in the number of IFN-γ-secreting cells in the spleen during an acute LCMV-infection. CD8+ T cells made up the majority of the IFN-γ-producing cells, but analysis of the cell culture supernatants by ELISA revealed that the CD4+T cells produced more IFN-γ on a per cell basis. No significant increase in IL-4 levels was detected under these experimental conditions. These data suggest that LCMV infection induces primarily a virus-specific Th1 response that is characterized by increased IFN-γ production. No quantitative information was known about the frequency and longevity of the LCMV-specific CD4+ T cell response. Using limiting dilution assays (LDA), I examined the CD4+ T cell precursor (Thp) frequency in C57BL/6 mice infected with LCMV. The virus-specific CD4+ Thp frequency increased from <1/100,000 in uninfected mice to a peak of approximately 1/600 in FACS-purified splenic CD4+ T cell populations by 10 days p.i. with LCMV. After the peak of the response, the CD4+ Thp frequency decreased only about 2-fold per CD4+ T cell to approximately 1/1200 and remained stable into long-term memory. The CD4+ Thp frequency to each of the two known LCMV major histocompatibility complex (MHC) class II-restricted peptides dropped only 2- to 7-fold from the peak of the acute LCMV response into long-term memory. Thus, the CD4+T cell frequencies remain elevated after the acute infection subsides and remain extremely stable throughout long-term immunity. The above results show that LDA can account for +T cells as being virus-specific following LCMV infection. However, using newer, more sensitive assays based on intracellular cytokine production, >20% of the CD4+ T cells secreted IFN-γ after stimulation with phorbol myristic acid and ionomycin during the peak of the acute CD4+ T cell response. In addition, >10% of the CD4+ T cells secreted IFN-γ after stimulation with the LCMV MHC class II-restricted CD4 peptides. Thus, these new sensitive assays reveal a heretofore unappreciated, yet profound antigen-specific CD4+T cell response during LCMV infection. Infection of mice with a series of unrelated viruses, termed heterologous viruses, causes the reduction of memory CD8+ T cells specific to earlier infections. In order to examine the fate of CD4+ T cells under these conditions, I examined cytokine production and followed the CD4+ Thp frequency following heterologous virus infections. Challenge of LCMV-immune mice with vaccinia virus (VV) resulted in a significant increase in both the amount of IFN-γ protein and the frequency of IFN-γ-producing cells in the peritoneal cavity 3 days after infection as compared to control non-immune mice acutely infected with VV or to LCMV-immune mice alone. Intracellular IFN-γ staining revealed that both CD4+ and CD8+ T cells contributed to this increased IFN-γ production. LDA analysis of the LCMV-specific CD4+ Thp frequency following multiple heterologous virus infections or protein antigen immunizations, revealed that the CD4+ Thp frequency remains stable even under conditions that reduce the LCMV-specific CD8+ CTLp frequency. Additional studies using high-dose LCMV Clone 13 demonstrated that, like CD8+ T cells, there is a decline in detectable LCMV-specific CD4+Thp during overwhelming virus infections. The data presented in this thesis help provide a better understanding of the CD4+ T cell response during virus infections. I make several novel observations, including the demonstration that mAb CZ-1 defines a novel activation and memory marker for CD4+ T cells, that the LCMV-specific memory CD4+ Thp frequency remains extremely stable into long-term immunity, and that heterologous virus infections do not disturb the stable memory CD4+ T cell pool following a virus infection. I also provide data using new sensitive assays based on intracellular cytokine production that there is a much more profound antigen-specific CD4+ T cell response during viral infections than has previously been realized. Finally, I provide evidence that the virus-specific CD4+ T cells become unresponsive following a high-dose LCMV Clone 13 infection. Thus, the data presented in this thesis highlight some important similarities and differences between the CD4+ and CD8+ T cell responses during acute viral infections.
    DOI
    10.13028/zj0e-xx59
    Permanent Link to this Item
    http://hdl.handle.net/20.500.14038/31392
    Rights
    Copyright is held by the author, with all rights reserved.
    ae974a485f413a2113503eed53cd6c53
    10.13028/zj0e-xx59
    Scopus Count
    Collections
    Morningside GSBS Dissertations and Theses

    entitlement

     
    DSpace software (copyright © 2002 - 2023)  DuraSpace
    Lamar Soutter Library, UMass Chan Medical School | 55 Lake Avenue North | Worcester, MA 01655 USA
    Quick Guide | escholarship@umassmed.edu
    Works found in eScholarship@UMassChan are protected by copyright unless otherwise indicated.
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.