Influenza hemagglutinin peptide-HLA-DR complex (HA-HLA-DR)

The Influenza hemagglutinin peptide-HLA-DR complex is a molecular assembly consisting of a processed peptide fragment from the influenza virus hemagglutinin (HA) protein, typically the HA 306-318 epitope, non-covalently bound to the peptide-binding groove of a Human Leukocyte Antigen (HLA) class II DR molecule (Stern et al., 1994, Nature). This complex is expressed on the surface of professional antigen-presenting cells (APCs) such as dendritic cells and B cells, where it serves as the primary ligand for the T-cell receptors (TCRs) of CD4+ helper T cells (Hennecke & Wiley, 2002, Cell). The interaction between the TCR and the HA-HLA-DR complex is highly specific and determines the magnitude and quality of the T-cell response against influenza infection. This system is a cornerstone of immunological research, used to study the structural biology of antigen recognition and to evaluate the efficacy of influenza vaccines and immunotherapies. It is particularly well-characterized in the context of the HLA-DRB1*01:01 allele, providing a model for understanding how MHC polymorphism influences disease susceptibility and vaccine performance (UniProt, P01911). Drugs and vaccines targeting this complex aim to modulate the immune response, either by enhancing protection against the virus or by investigating therapeutic interventions for immune-mediated conditions. The complex is also used in the development of TCR-like antibodies and soluble TCR therapeutics that can specifically target infected cells. Understanding the binding affinity and kinetics of this interaction is crucial for designing next-generation vaccines that elicit robust and long-lasting T-cell memory.

Other names

HA306-318/HLA-DR1 complexHemagglutinin peptide-MHC class II complexHA-DRB1*01:01 complexHA-DR4 complexHA-DR complex

The complex acts as a ligand for the T-cell receptor (TCR) on CD4+ T cells, triggering signal transduction pathways that lead to T-cell proliferation, cytokine production, and orchestration of the adaptive immune response (Stern et al., 1994, Nature).