A cell-free antigen processing system informs HIV-1 epitope selection and vaccine design.

Area of Science:

• Immunology
• Virology
• Proteomics

Background:

• Distinct CD4+ T cell epitopes are linked to spontaneous control of HIV-1.
• Factors influencing HIV-1 epitope selection by antigen-presenting cells remain poorly understood.

Purpose of the Study:

• To investigate antigen-dependent factors governing HIV-1 epitope selection.
• To identify novel HIV-1 epitopes using a cell-free processing system.

Main Methods:

• Utilized a cell-free system with soluble HLA-DR, HLA-DM, cathepsins, and full-length HIV-1 proteins (Gag, Pol, Env, Vif, Tat, Rev, Nef).
• Employed liquid chromatography-tandem mass spectrometry (LC-MS/MS) for epitope identification.
• Assessed CD4+ T cell recall responses to identified epitopes in HIV-1+ donors.

Main Results:

• Identified 35 novel HIV-1 epitopes, including glycopeptides.
• Epitopes from smaller HIV-1 proteins were located in regions of low stability and high solvent accessibility.
• Efficient processing correlated with antigens eliciting limited CD4+ T cell responses; some protective epitopes were processed inefficiently.
• 55% of cell-free derived epitopes induced memory CD4+ T cell responses, including 8 of 19 novel epitopes.

Conclusions:

• The cell-free system effectively mimics Class II antigen processing, revealing key factors in HIV-1 epitope selection.
• This in vitro approach provides insights into epitope selection for HIV-1 and potentially other antigens.
• Identified epitopes and processing insights may inform vaccine development and immunotherapeutic strategies.