Induction of interferon-alpha in human leukocytes by polioviruses: wild-type strains are better inducers than attenuated strains.

Cultures of human peripheral blood leukocytes were exposed to different poliovirus strains at a multiplicity of infection of 1 TCID50/cell. Induction of interferon was a regular phenomenon in the cultures but the maximal yields varied between experiments. Resistance to moderate temperature (56 degrees) and pH 2, as well as antigenic properties, indicated that most of the activity was due to interferon-alpha. Low levels of interferon-gamma were also measured in the cultures using a radioimmunoassay. Using kinetic uv-inactivation we found that infectivity of the virus preparations was affected more rapidly than the capability to induce interferon-alpha. Dependence of interferon-alpha yields on the inducing virus strain was examined in 46 independent cultures by comparing the three serotypes of the attenuated poliovirus vaccine strains and two wild-type strains of serotype 3 (Saukett and P3/FIN/23127/84). The wild-type strains were significantly better inducers of interferon than the attenuated strains (P less than 0.001). Four other wild-type strains representing all serotypes tested in 12 independent cultures were also better interferon inducers than the corresponding Sabin strains (P less than 0.02). Induction of interferon may have a role in the poliovirus-induced inhibition of lymphocyte mitogenesis previously reported by others.