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Experimental influenza infection: influence of stress.

The effect of immobilization stress on the course of various forms of influenza infection has been investigated. Influenza was produced in 10-14-week-old inbred mice by intranasal infection with pathogenic influenza virus strain A/PR/8/34 (H1N1) at different doses. Immobilization for 6 hr resulted in the appearance of virus-inhibiting activity in the serum of mice. This activity suppressed the reproduction of test-virus in tissue culture, it was resistant to acid pH 2.0 treatment and to heating at 56 degrees C. However, the high level of virus-inhibiting activity failed to protect the animals from subsequent development of lethal influenza infection. Immobilization stress caused a transient depression of virus induced interferon (IFN) production, as revealed by the use of virus inducer at early intervals after stress. Contemporarily, the stress could aggravate the course of virus infection promoting its transition from non-lethal form into a lethal one and virus penetration into brain.