A mouse model of influenza protection.

A mouse model has been developed in order to examine the parts played by humoral and cellular mechanisms in influenza immunity. Protection is assessed in terms of the amount of virus detectable in the lungs within 48 h of challenge. This system has two major advantages over the more common mouse lethality models. It is no longer necessary to use a mouse-lethal strain of virus; and protection is measured within days rather than weeks of challenge. Thus it is possible to determine the ability of the immune system to limit infection at an early stage, as distinct from curing a pre-existing infection and so preventing death. Transfer of spleen cells from an immune donor to a normal recipient will significantly reduce the amount of virus found in the lungs 24 h after challenge. The transferred cells are, however, capable of producing significant serum levels of anti-influenza antibody. Administration of serum from immune mice to normal recipients also results in a significant degree of protection within 24 h of challenge. These results give additional evidence that in the mouse significant protection is provided by serum antibody very soon after infection, but do not exclude the possibility that a part may be played by other mechanisms.