PRR adjuvants restrain high stability peptides presentation on APCs.

Area of Science:

• Immunology
• Vaccinology
• Molecular Biology

Background:

• Adjuvants enhance adaptive immunity but their impact on immune response specificity and antigen presentation mechanisms is unclear.
• Understanding how adjuvants modulate epitope hierarchy and antigen processing is crucial for vaccine development.

Purpose of the Study:

• To investigate how different adjuvants affect antigen-specific CD4+ T-cell immunodominant epitope hierarchy.
• To explore the mechanisms by which adjuvants regulate antigen processing and presentation by antigen-presenting cells (APCs).

Main Methods:

• Screening of dominant Th1 T-cell epitopes using overlapping synthetic peptides in mice vaccinated with different adjuvants.
• Analysis of MHC-II immunopeptidomes to characterize peptide repertoires presented by APCs.
• Assessment of peptide-MHC (pMHC) stability and T-cell responses.

Main Results:

• Adjuvants significantly altered the immunodominant epitope hierarchy of antigen-specific CD4+ T-cells.
• Adjuvant stimulation, particularly with MPLA and CpG, led to the disappearance of high-stability peptides presented by APCs.
• Low-stability peptides, revealed after adjuvant treatment, elicited robust T-cell responses and immune memory.

Conclusions:

• Adjuvants (MPLA, CpG) inhibit the presentation of high-stability peptides rather than revealing cryptic epitopes.
• This modulation of pMHC stability by adjuvants alters CD4+ T-cell-dominant epitope responses, impacting vaccine specificity.
• Findings have significant implications for selecting adjuvants in vaccine design and developing epitope-based vaccines.