Fluorescent dye labeled influenza virus mainly infects innate immune cells and activated lymphocytes and can be used in cell-mediated immune response assay.

Early results have recognized that influenza virus infects the innate and adaptive immune cells. The data presented in this paper demonstrated that influenza virus labeled with fluorescent dye not only retained the ability to infect and replicate in host cells, but also stimulated a similar human immune response as did unlabeled virus. Influenza virus largely infected the innate and activated adaptive immune cells. Influenza B type virus was different from that of A type virus. B type virus was able to infect the immature lymphocytes, but in lower amounts when compared to activated lymphocytes. Protection from influenza is tightly associated with cellular immunity. Traditional methods of cellular immunity assay had limitations to imitate the natural human cell-mediated responses to influenza virus. Labeled viruses could be used in the assay of virus-specific cytotoxicity, which might reflect the natural process more closely. Furthermore, human immune cells activated by one influenza subtype virus could kill the cells infected by other subtype virus. These results implied the human immune cells could directly handle and remove free virus using similar mechanism that was used to remove virus-infected nonimmune cells, which might help to simplify the design and production of influenza vaccine, thereby reduce the cost.