Human CD4+ T cells displaying viral epitopes elicit a functional virus-specific memory CD8+ T cell response

Area of Science:

• Immunology
• Virology
• Cellular Biology

Background:

• Herpes virus infections trigger rapid recall responses via memory T cells.
• Immunological synapse formation and trogocytosis are key for T cell activation.
• The role of T cell-derived antigen presentation in viral memory responses is not fully understood.

Purpose of the Study:

• To investigate the function of antigen-specific CD4+ T cells as antigen-presenting T cells (T-APCs) in herpes virus infections.
• To compare the efficacy of CD4+ T-APCs with professional antigen-presenting B cells (CD40B-APCs).
• To elucidate the contribution of T-APC mediated epitope presentation to CD8+ T cell memory expansion and function.

Main Methods:

• Comparison of CD4+ T-APCs and CD40B-APCs in stimulating virus-specific CD8+ T cells.
• Analysis of T cell expansion, effector functions (lysis, cytokine production), and phenotype.
• Assessment of costimulatory ligand expression on different antigen-presenting cell types.

Main Results:

• CD4+ T-APCs showed reduced costimulatory ligand levels compared to CD40B-APCs.
• Despite differences, CD4+ T-APCs induced a significant >35-fold expansion of herpes virus-specific CD8+ T cells.
• CD8+ T cells generated by both T-APCs and CD40B-APCs exhibited comparable effector functions and phenotypes.

Conclusions:

• Antigen-specific CD4+ T cells can function as potent antigen-presenting T cells (T-APCs) during viral recall responses.
• T-APC mediated presentation of viral epitopes contributes to the expansion of virus-specific CD8+ T cell memory.
• These findings highlight a novel mechanism in regulating cellular immune memory during herpes virus infections.