Drug-induced modulation of cellular activation during latency reversal changes antigen processing and peptide presentation in primary CD4 T cells

Abstract Objective: EBV-specific CD8+ T cells have been extensively studied in various settings, and appear to play a major role in the control of EBV-related malignancies. In contrast, it is still unclear whether EBV-specific CD4+ T cells play a role in vivo. To study this question, an assay was developed to measure the CD4+ T-cell response towards two EBV antigens, in both healthy (n=14) and HIV-infected subjects (n=23). In addition, both HAART-treated (n=12) and untreated HIV+ individuals (n=14) - including progressors to EBV-related lymphoma - were studied longitudinally. Methods: EBV-specific CD4+ T cells were stimulated with peptide pools from latent protein EBNA1 and lytic protein BZLF1, and detected by measurement of IFNg-production. Results: After direct ex vivo stimulation, EBNA1 or BZLF1-specific IFNg- (and/or IL2) producing CD4+ T cell numbers were low, and measurable in less than half of the subjects studied (either HIV- and HIV+). Therefore, PBMC were cultured for 12 days in the presence of peptides and IL2 (from day 3), and then restimulated with peptides, allowing specific and reproducible expansion of EBV-specific CD4+ T cells, independent of HLA type and ex vivo antigen processing. Interestingly, numbers of EBV-specific CD4+ T cells inversely correlated with EBV viral load, implying an important role for EBV-specific CD4+ T cells in the control of EBV in vivo. Untreated HIV-infected individuals had a lower CD4+ T cell response to EBNA1 and BZLF1 as compared to healthy EBV carriers and HAART-treated HIV+ subjects. In longitudinal samples, EBNA1-specific, but not BZLF1-specific T-cell numbers increased after HAART, while EBV load was not affected by treatment. In all the progressors to EBV-related lymphoma, EBV-specific CD4+ T cells were lost at least 24 months before lymphoma diagnosis. Conclusions: Both cross-sectional and longitudinal data suggest an important role for EBV-specific CD4+ T cells in the control of EBV-related malignancies. Furthermore, it seems that HAART treatment leads to recovery of EBNA1-specific, but not BZLF1-specific CD4+ T-cell responses, implying changes in the latency pattern of EBV, despite an unaltered cell-associated EBV DNA load. Thus, early HAART treatment might prevent loss of specific CD4+ T-cell help and progression to NHL.

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Direct Expansion of Functional CD25+ CD4+ Regulatory T Cells by Antigen-processing Dendritic Cells

Journal of Experimental Medicine ◽

10.1084/jem.20030422 ◽

2003 ◽

Vol 198 (2) ◽

pp. 235-247 ◽

Cited By ~ 649

Author(s):

Sayuri Yamazaki ◽

Tomonori Iyoda ◽

Kristin Tarbell ◽

Kara Olson ◽

Klara Velinzon ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

T Cell Receptor ◽

Cd4 T Cells ◽

Antigen Processing ◽

Specific Antigen ◽

Cell Receptor ◽

Cd4 T Cell

An important pathway for immune tolerance is provided by thymic-derived CD25+ CD4+ T cells that suppress other CD25− autoimmune disease–inducing T cells. The antigen-presenting cell (APC) requirements for the control of CD25+ CD4+ suppressor T cells remain to be identified, hampering their study in experimental and clinical situations. CD25+ CD4+ T cells are classically anergic, unable to proliferate in response to mitogenic antibodies to the T cell receptor complex. We now find that CD25+ CD4+ T cells can proliferate in the absence of added cytokines in culture and in vivo when stimulated by antigen-loaded dendritic cells (DCs), especially mature DCs. With high doses of DCs in culture, CD25+ CD4+ and CD25− CD4+ populations initially proliferate to a comparable extent. With current methods, one third of the antigen-reactive T cell receptor transgenic T cells enter into cycle for an average of three divisions in 3 d. The expansion of CD25+ CD4+ T cells stops by day 5, in the absence or presence of exogenous interleukin (IL)-2, whereas CD25− CD4+ T cells continue to grow. CD25+ CD4+ T cell growth requires DC–T cell contact and is partially dependent upon the production of small amounts of IL-2 by the T cells and B7 costimulation by the DCs. After antigen-specific expansion, the CD25+ CD4+ T cells retain their known surface features and actively suppress CD25− CD4+ T cell proliferation to splenic APCs. DCs also can expand CD25+ CD4+ T cells in the absence of specific antigen but in the presence of exogenous IL-2. In vivo, both steady state and mature antigen-processing DCs induce proliferation of adoptively transferred CD25+ CD4+ T cells. The capacity to expand CD25+ CD4+ T cells provides DCs with an additional mechanism to regulate autoimmunity and other immune responses.

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