In vivo hyporesponsiveness induced by Sendai virus in CFLP mice

Sendai and Semliki Forest viruses (SFV) raised the interferon (IFN) level in blood and suppressed the acute inflammatory response induced by carrageenan in CFLP mice. After Sendai virus had been inoculated, unresponsiveness developed to repeated challenge either with the same virus or with SFV. The hyporeactive state culminated 48 hr after first virus inoculation. It was characterized (1) by absence of IFN induction and (2) by disappearance of the virus-induced anti-inflammatory effect. In contrast, the anti-inflammatory effect of indomethacin and dexamethasone remained unchanged. In addition, peripheral white blood cells were counted upon Sendai virus inoculation either in normal or in hyporesponsive mice. Six hr after inoculation, Sendai virus induced a marked granulocytosis with lymphopenia. In hyporesponsive mice leukocytosis was observed. Repeated Sendai virus injection was followed by a less pronounced granulocytosis, while the decreased number of mononuclear cells remained unchanged. These alterations in mice inoculated with Sendai virus offers a model of hyporesponsiveness established in vivo.