Human macrophage responses to vaccine strains of influenza virus: synthesis of viral proteins, interleukin-1β, interleukin-6, tumour necrosis factor-α and interleukin-1 inhibitor

Interactions between influenza viruses and human macrophages were examined to detect potential mechanisms for enhanced febrile reactions previously associated with administration of an avian-human H1N1 reassortant vaccine. Cells exposed to that strain were compared with cells exposed to wild-type and cold-adapted H1H1 and H3H2 strains and an avian-human H3N2 strain. Cells exposed to the avian-human H1N1 virus showed increased synthesis of viral neuraminidase, previously reported to induce fever-producing cytokines, but no detectable increase in production of interleukin-1β, interleukin-6 and tumour necrosis factor-α measured by immunoassay, or decrease in interleukin-1 inhibitor activity by bioassay.