Viral-specific T lymphocytes play an important protective role in HIV infection. Although most infected subjects without AIDS have a high frequency of HIV-specific CD8 T lymphocytes, the targeted immune response fails to control HIV production. Freshly isolated peripheral blood lymphocytes from HIV-infected donors often lack HIV-specific cytotoxicity, which develops after overnight culture. To investigate reasons for in vivo T cell dysfunction, we analyzed by flow cytometry the relative expression of CD3 and CD3 , the signaling component of the T cell receptor complex. In 28 HIV-infected donors of all disease stages, a substantial fraction of circulating T cells downmodulate CD3 (fraction of CD3 -expressing T cells 0.74+0.16 vs 1.01+0.07 in normal donors, p<0.0000005). CD3 expression is downregulated more in CD8 than CD4 T cells, decreases early in infection and correlates with declining CD4 counts and disease stage. CD3 expression returns to normal over 6-10 hr of culture in an IL-2 dependent manner, coincident with restoration of viral-specific cytotoxicity. The hypothesis of this proposal is that abnormal CD3 expression by circulating T cells interferes with T cell antiviral functions of direct cytotoxicity and viral suppression by cytokine and chemokine secretion. Impaired T cell receptor signaling in vivo may help explain why the high frequency of HIV-specific precursor CTL fails to control HIV replication. This proposal will examine the extent to which CD3 downmodulation interferes with T cell signaling and cytokine production and determine whether certain subsets of T cells (such as activated, memory, cycling, apoptotic or HIV-specific CTL) are preferentially affected. Reasons for downmodulation will be investigated, including lack of specific helper function via IL-2 or other cytokine secretion, viral antigen excess causing CD8 T cell anergy, or inhibition by activated or HIV-infected macrophages or their products. Clinical trial and MACS cohort samples will be used to examine when CD3 downmodulation and T cell dysfunction occur and whether they improve with antiretroviral and immune based therapy.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI042519-02
Application #
2887675
Study Section
AIDS and Related Research Study Section 1 (ARRA)
Program Officer
Plaeger, Susan F
Project Start
1998-04-01
Project End
2001-03-31
Budget Start
1999-04-01
Budget End
2000-03-31
Support Year
2
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Immune Disease Institute, Inc.
Department
Type
DUNS #
115524410
City
Boston
State
MA
Country
United States
Zip Code
02115
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