Influenza continues to cause substantial morbidity and mortality each year despite broad vaccine availability. Licensed vaccines primarily elicit antibody-mediated protection directed at rapidly changing surface glycoproteins of the virus. Because these surface antigens mutate frequently, current vaccines must be reformulated and administered annually to match circulating strains. This constraint motivates interest in immune mechanisms that target more conserved viral components.
CD8+ T cells can recognise peptide fragments derived from internal viral proteins and therefore target more conserved epitopes than antibodies. These cytotoxic T lymphocytes contribute to control and clearance of viral infections by recognising peptides presented on HLA class I molecules and killing infected cells. Given their potential to provide broader, cross-reactive protection across viral variants, CD8+ T cell responses are a focus for future vaccine and therapeutic strategies.
Both Alphainfluenzavirus (commonly referred to as FLUAV) and Betainfluenzavirus (FLUBV) co-circulate in human populations and contribute to seasonal epidemics. Although FLUAV has been the major focus of much influenza research, FLUBV also plays a significant role in human disease burden. The review emphasises that, despite FLUBV’s clinical importance, it has been comparatively understudied with respect to CD8+ T cell immunity.
The available data on CD8+ T cell epitopes derived from FLUBV are limited relative to FLUAV. The review summarises existing studies that have identified FLUBV-derived peptides recognised by CD8+ T cells, but notes that both the number of characterised epitopes and the depth of cellular immunology data for FLUBV remain sparse. Where studies exist, they provide initial descriptions of target peptides and T cell recognition, but comprehensive mapping of dominant and subdominant epitope landscapes across diverse human populations is not yet realised.
Presentation of viral peptides on HLA class I molecules is fundamental for CD8+ T cell recognition. The review addresses molecular-level considerations for FLUBV peptide generation, processing, and binding to HLA class I, highlighting that detailed structural and biochemical characterisation has been more extensively performed for FLUAV-derived peptides than for FLUBV. Specific data on peptide-HLA binding motifs, allele restriction, and processing pathways for FLUBV-derived peptides are less comprehensive in the literature.
Compared with FLUAV, FLUBV research exhibits a notable knowledge gap at both immunological and molecular levels. For FLUAV there is a richer catalogue of CD8+ T cell epitopes, better characterisation of HLA restrictions, and more structural and functional data on peptide presentation. The review highlights that this imbalance leaves unanswered questions about the breadth, cross-reactivity and protective capacity of FLUBV-specific CD8+ T cell responses in humans.
Because CD8+ T cells recognise conserved internal viral epitopes, they are attractive targets for vaccines intended to confer broader and longer-lasting protection than strain-matched humoral vaccines. The paucity of detailed data on FLUBV-derived peptides and their presentation by HLA class I molecules may limit rational design of T cell–focused vaccines or immunotherapies that include FLUBV components. The review suggests that improving molecular and cellular characterisation of FLUBV epitopes is important to guide development of next-generation, broad-spectrum influenza interventions.
The review summarises current knowledge on FLUBV-derived CD8+ T cell epitopes at cellular and molecular levels and contrasts this with the more comprehensive literature on FLUAV. Its principal conclusion is that there is limited data on FLUBV despite its clinical relevance, and that this gap spans epitope identification, HLA class I presentation, allele-specific restriction, and functional characterisation of T cell responses. The article underscores the need for expanded studies to map FLUBV epitopes across populations and to dissect the molecular details of peptide processing and HLA binding that underpin CD8+ T cell recognition.
PMID: 42535260 DOI: 10.1042/BST20260075