Stimulation of lymphokines in Jurkat cells persistently infected with vaccinia virus

The response of the human CD4⁺ T-cell line Jurkat to infection with vaccinia virus was investigated. Virus titers peaked approximately 3 to 4 days after infection, while cell growth paralleled that of uninfected cells, indicating that growth rates were not appreciably affected by viral infection. Results from plaque assays and fluorescence-activated cell sorter (FACS) analyses of virus antigens demonstrated that a persistent infection in which the percentage of infected cells and the virus titers fluctuated from passage to passage was established. Further characterization of the persistent infection revealed that the virus influences cellular functions. Induction of interleukin-2 (IL-2) and IL-2 receptor α (IL-2Rα) in J_vac cells was shown by enzyme-linked immunosorbent assay and FACS analysis, respectively. Hybridization of cellular RNA with cloned probes confirmed the increased IL-2 expression and demonstrated that J_vac cells also expressed more IL-6 but not gamma interferon (IFN-γ) or IL-1β. Dual-antibody staining and FACS analysis for vaccinia virus antigens and IL-2Rα indicated that IL-2Rα expression was restricted to the infected cells. J_vac cells were also resistant to superinfection, an additional proof that persistent infection elicited phenotypic changes in the cell population.