Human Cytomegalovirus Antigen Presentation by HLA-G in Infected Cells

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Human Leukocyte Antigen (HLA)-E and -G are class Ib molecules with poorly understood roles in antigen presentation.
• HLA-E is known to bind viral peptides and interact with NK cell receptors, while HLA-G's presentation capabilities are largely unknown.
• This study investigates the potential of HLA-G to present human cytomegalovirus (HCMV) antigens.

Purpose of the Study:

• To investigate whether HLA-G presents viral peptides in HCMV-infected cells.
• To determine if these presented peptides elicit CD8+ T cell responses.
• To assess the impact of HLA-G presented peptides on Natural Killer (NK) cell function.

Main Methods:

• Proteomic analysis of infected cells to identify HLA-G displayed peptides.
• In vitro binding assays to confirm peptide-HLA-G interactions.
• Functional assays using CD8+ T cells and NK cells from HCMV-seropositive donors.

Main Results:

• Identified 22 HCMV-derived peptides presented by HLA-G, with 17 confirmed to bind in vitro.
• No significant CD8+ T cell cytokine production was observed in short-term assays with HLA-G-binding peptides.
• While some viral peptides bound both HLA-G and HLA-E, they did not activate CD94/NKG2 NK cell receptors.

Conclusions:

• HLA-G can present potentially immunogenic viral peptides in HCMV-infected cells.
• The study does not support a role for HLA-G in restricting CD8+ T cell responses to these viral peptides.
• HLA-G presented viral peptides did not modulate NK cell functions in this context.