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Studies on binding of HIV-1 p24gag peptide to HLA-Cw3+ cells
A Kość1, J Dubis, I Wojciechowska
1Laboratory of Immunogenetics, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw.
Insights
Low peptide binding limits human leukocyte antigen C (HLA-C) expression. Adding specific peptides increased HLA-C cell surface levels, suggesting peptide availability is key for HLA-C expression.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Human leukocyte antigen C (HLA-C) molecules are expressed at lower levels than HLA-A and HLA-B.
- This lower expression may be due to limited high-affinity peptide binding, affecting transport and stability.
Purpose of the Study:
- To investigate if peptide availability limits cell surface expression of HLA-C.
- To determine if adding exogenous peptides can enhance HLA-C surface levels.
Main Methods:
- Utilized lymphoblastoid cell lines, including HLA-Cw3+ and HLA-Cw3- variants.
- Pulsed cells with a synthetic HIV-1 p24gag peptide presented by HLA-Cw3.
- Analyzed cell surface HLA expression using flow cytometry with specific monoclonal antibodies.
Main Results:
- HLA-Cw3+ cells showed higher binding of the specific peptide compared to HLA-Cw3- cells.
- Pulsing HLA-Cw3+ cells with the peptide increased cell surface expression of HLA-B,C antigens.
- No significant increase in HLA class I expression was observed in HLA-Cw3- cells after peptide pulsing.
Conclusions:
- Limited availability of high-affinity peptides is a potential factor restricting HLA-C cell surface expression.
- Exogenous peptide addition can upregulate HLA-C surface levels, supporting the peptide-limitation hypothesis.
Abstract:
Human major histocompatibility complex class I antigens, HLA-C, are expressed on the cell surface at approximately a tenfold lower level than HLA-A and -B. We hypothesized that the expression of HLA-C is limited by the quantity of high affinity peptides which bind to these molecules, thus allowing only a small fraction of HLA-C molecules to be transported and/or to remain stable on the cell surface. If this assumption is correct, then the addition of exogenous peptide should increase cell surface HLA-C expression. To verify the hypothesis, we pulsed lymphoblastoid cell line PAJ (HLA-Cw3+) with synthetic HIV-1 p24gag 145-152 peptide, known to be presented to T-lymphocytes by HLA-Cw3 molecule. PAJ (HLA-Cw3+) cells bound approximately two times more of the peptide than HAJ (HLA-Cw3-), and four times more than 500/C9 (HLA-Cw3-) cells. Accordingly, overnight pulsing of PAJ cells with the p24gag 145-152 peptide caused an increase in class I HLA expression detected on the cell surface by flow cytofluorimetric analysis with anti-HLA-B,C monoclonal antibodies but not by anti-HLA-A antibody. In contrast, HLA-Cw3- cells treated in the same manner did not show any increase of HLA class I expression. Our data suggest that low concentration of high affinity peptides within the cell may be one of the factors limiting cell surface expression of HLA-C molecules.
