Activity of cyclosporin A in experimental influenza virus infection in mice.

Oral administration of the immunosuppressive fungal metabolite cyclosporin A increased the mortality of Balb/c mice infected intranasally with influenza A/Hong Kong/1/68 (H3N2) virus. Cyclosporin A also increased the amount of virus that could be recovered from the lungs of infected mice and delayed the rate at which it was eliminated. Treatment with cyclosporin A did not, however, prevent the appearance of haemagglutination inhibiting antibody in the sera of animals that had been infected with a sub-lethal concentration of virus.