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Anti-CD4 cytotoxic T lymphocyte (CTL) activity in HIV+ patients: flow cytometric analysis
Y Yamamura1, N Rodriguez, A Schwartz
1Ponce School of Medicine, AIDS Research Program, Puerto Rico 00732.
Insights
Human immunodeficiency virus type 1 (HIV-1) infection leads to CD4 cell destruction, despite no extracellular viral p24 antigen production. HIV-1-infected CD8 cells exhibit cytotoxic activity against CD4 cells.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Peripheral blood mononuclear cells (PBMC) play a crucial role in immune responses.
- Human immunodeficiency virus type 1 (HIV-1) infection is characterized by a decline in CD4+ T cell counts.
- Understanding the mechanisms of CD4+ T cell loss in HIV-1 is critical for therapeutic development.
Purpose of the Study:
- To investigate the proliferative responses and cell death patterns of CD4+ and CD8+ T cell subsets in HIV-1-infected individuals.
- To analyze the cytotoxic activity of CD8+ T cells against CD4+ T cells in the context of HIV-1 infection.
- To determine the role of viral p24 antigen production and IL-2 in HIV-1-induced T cell dynamics.
Main Methods:
- Cell proliferation analysis using flow cytometry on mitogen-stimulated PBMC from healthy donors and HIV-1-infected individuals.
- Stimulation with phytohemagglutinin (PHA) and assessment of CD4 and CD8 T cell subsets.
- Co-culture experiments to evaluate cytotoxic T lymphocyte (CTL) activity of HIV-1-infected CD8+ cells against CD4+ T cells.
- Measurement of extracellular viral p24 antigen and assessment of IL-2 effects.
Main Results:
- Phytohemagglutinin stimulation induced proliferation of CD4 and CD8 T cells in healthy donors.
- PBMC from certain HIV-1-infected individuals showed CD8+ T cell proliferation but CD4+ T cell destruction, without extracellular p24 antigen.
- Purified HIV-1-infected CD4+ cells did not undergo cell death upon activation but produced p24 antigen.
- HIV-1-infected CD8+ T cells exhibited cytotoxic activity against both HIV-1-infected and normal CD4+ T cells, with a preference for less proliferative CD4+ cells.
- Exogenous IL-2 did not prevent CD4+ T cell death or alter p24 production.
- Anti-CD4 CTL activity correlated with higher CD8+ T cell counts in HIV-1+ patients.
Conclusions:
- HIV-1 infection can lead to CD4+ T cell destruction mediated by cytotoxic CD8+ T cells, independent of extracellular viral p24 antigen production.
- The cytotoxic activity of HIV-1-infected CD8+ T cells is a significant factor in CD4+ T cell depletion.
- CD8+ T cell counts, rather than CD4+ T cell counts, are associated with the presence of anti-CD4 CTL activity in HIV-1 patients.
Abstract:
A new cell proliferation analysis by flow cytometry was applied to the mitogen induced cultures of peripheral blood mononuclear cells (PBMC) from either normal, healthy donors or those individuals who are infected by human immunodeficiency virus, type 1 (HIV-1). While phytohemagglutinin (PHA) stimulation of normal PBMC (nPBMC) yielded propagation of both CD4 (nCD4) and CD8 (nCD8) T cell subsets, similar activation of PBMC from certain HIV-1-infected individuals (HIV-PBMC) produced active proliferation of CD8 (HIV-CD8) cells but varying degrees of CD4 (HIV-CD4) cell destruction. However, no measurable viral p24 antigen was produced extracellularly. On the other hand, when the purified HIV-CD4 cells were similarly activated, no such cell death was noted and high titer p24 was detected in the culture supernatants. Addition of exogenous IL-2 to either HIV-PBMC or HIV-CD4 cultures, did not alter either CD4 cell death or HIV-1 p24 production. Isolated HIV-CD8 killed not only HIV-CD4 but also nCD4, when co-cultured and less proliferative fractions of CD4 cell population was the more preferred targets of the HIV-CD8 CTL activity. The presence of anti-CD4 CTL activity was closely associated with high CD8, but not with CD4 counts, of the HIV+ patients.
