GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE347nnn/GSE347532/primaryOK200TranscriptomicsMus musculusExpression profiling by high throughput sequencinghttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE347532GEOGSEfalseIntranasal live vaccine harnesses pre-existing T cell memory for broad influenza protectionInfluenza A virus (IAV) continually drives seasonal epidemics and pandemics through antigenic evolution, yet conventional vaccines afford limited cross-protection due to their subtype-restricted antibody responses. Respiratory tissue-resident memory T (TRM) cells recognize conserved epitopes and serve as key effectors against heterosubtypic IAV, but effective induction strategies remain elusive. Here we show that the CA4-dNS1 live attenuated influenza nasal spray vaccine confers broad heterosubtypic protection against circulating IAVs via pulmonary TRM induction, independent of cross-reactive antibodies. Notably, pre-existing memory T cells, established by prior infection or intramuscular vaccination, are efficiently recruited by nasal boosting and differentiate into functional pulmonary TRM, substantially augmenting protective efficacy. Mechanistically, intramuscular priming expands the central memory T (TCM) pool, whereas nasal spray vaccination acts as a "portal-of-entry" immunization that both induces local TRM maturation and directs circulating TCM trafficking to the respiratory mucosa, thereby establishing a robust local immune barrier. This paradigm is generalizable to other vector-based nasal spray vaccines, providing a strategic framework for universal influenza vaccine development and for harnessing pre-existing immunity in mucosal vaccine design.2026/09/21GSE347532GSM10054794GSM10054793GSM10054792GSM10054791GSM10054787GSM10054798GSM10054797GSM10054796GSM10054795GSM10054789GSM10054788GSM1005479024247347532Mus musculus