Systemic T-Cell Activation Landscapes Elicited Following Intramuscular and Intranasal Immunization with the Active NDV-Vectored Anti-COVID-19 Vaccine “Patria” in Humans

COVID-19 vaccines remain essential for pandemic control, but antibody responses wane, and viral variants emerge. Affordable platforms enabling local manufacturing are important for equitable vaccine access in low- and middle-income countries (LMICs). The locally developed and manufactured NDV-vectored AVX/COVID-12 “Patria” vaccine may help address this need. We conducted an exploratory analysis of antigen-specific cellular immunity in 17 healthy SARS-CoV-2-naïve volunteers from a previously reported phase I safety and immunogenicity cohort (NCT04871737). Eight participants received intramuscular (IM) and nine received intranasal (IN) vaccination. Peripheral blood collected through 90 days was stimulated in vitro with recombinant Wuhan-Spike protein and analyzed using activation-induced marker (AIM) assays, intracellular cytokine staining, and high-dimensional flow cytometry. AIM+ CD4+ T-cell frequencies peaked around day 28 at 0.45 (1.13)% after IM and 0.18 (0.6)% after IN vaccination, while AIM+ CD8+ T-cell responses remained lower, reaching 0.09 (0.22)% and 0.03 (0.33)%, respectively, median (IQR). Cytokine-producing T-cell responses showed no consistent route-related differences. High-dimensional analysis identified multiple activation-associated phenotypes in CD3+ and CD3− compartments, across both vaccination routes, with distinct temporal dynamics. These exploratory findings show systemic Spike-responsive T-cell activation in this cohort after both routes and provide a refined characterization of vaccine-induced cellular immunity, warranting further investigation of IN administration.