Significance of Antigenic Differences Among Strains of Influenza A Virus in Reinfection of Ferrets.

Abstract

Four to 10 weeks following an initial infection with influenza A virus, ferrets were found to be immune to clinical reinfection with that same strain of virus but were susceptible to reinfection with a strain of virus which was antigenically related to but different from the strain used for the original infection. The results indicated that for a constant amt. of virus there was a critical level of specific antibodies which separated a state of relative resistance from a state of relative susceptibility. In general, the strain specific titer of the time of inoculation can be taken as an index of that critical antibody level. However, that titer is not necessarily an index of the total amt. of antibodies which will be available to combat clinical infection because the speed with which the animal can produce additional antibodies must also be taken into consideration . The speed of response was influenced by the extent of previous experience of the animal with influenza virus antigens .