Multiple effector functions mediated by human immunodeficiency virus-specific CD4(+) T-cell clones

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Human immunodeficiency virus type 1 (HIV-1) Gag-specific T helper cells are crucial for controlling viral load.
• The exact functional capabilities and targeted epitopes of these cells require further elucidation.

Purpose of the Study:

• To characterize the functional attributes of Gag-specific CD4(+) T-cell clones from HIV-1-infected individuals.
• To identify specific T helper cell epitopes within the HIV-1 Gag protein.
• To investigate the mechanism of T cell-mediated cytotoxicity against HIV-1-infected cells.

Main Methods:

• Generation of Gag-specific CD4(+) T-cell clones from HIV-1-infected individuals.
• Peptide mapping to identify minimal T helper epitopes within the Gag protein.
• Assessment of T cell proliferation, cytokine secretion (IFN-gamma), and cytolytic activity.
• Mechanism of action studies using inhibitors (concanamycin A, EGTA, brefeldin A) and anti-Fas antibody.

Main Results:

• Identification of multiple Gag-specific T helper epitopes, including a minimal epitope (VHAGPIAG) in the cyclophilin binding domain.
• T cell clones demonstrated antigen-specific proliferation, IFN-gamma secretion, and perforin-mediated cytolysis.
• Evidence of serine esterase release, indicating perforin-mediated cytotoxicity.

Conclusions:

• HIV-1 Gag protein harbors multiple T helper epitopes recognized by CD4(+) T cells.
• T helper cells possess cytolytic capabilities, potentially contributing to the overall antiviral response against HIV-1.
• Perforin-mediated cytotoxicity is a key mechanism employed by these Gag-specific T helper cells.