Killer T-cellsUsing a technique called flow cytometry, the BioVaxys team found that its haptenized SARS-CoV-2 s-spike vaccine activated CD4+ helper T cells and CD8+ killer T cells that express the activation markers, CD69 and CD25. This result indicates that immunization with BVX-0320 at two different dose levels of 3µg or 10µg stimulated immune system memory 'helper' T-cells as well as killer T cells. CD4 + T-cells are crucial in achieving a regulated effective immune response to viral pathogens, and are central to adaptive immune responses. Generated following an immune response, memory 'helper' CD4+ T-cells retain information about the virus, which enables them to respond rapidly after viral exposure. CD8+ T cells have the capacity to kill cells infected by the virus, thereby stopping viral replication in those cells.