Differential mononuclear leukocyte attracting chemokine production after stimulation with active and inactivated influenza A virus.

After influenza A virus infection of human monocytes, we found a rapid and marked release of the mononuclear cell attracting chemokines MCP-1, MIP-1 alpha, and IP-10, with corresponding gene expression patterns as determined by Northern blot analysis. In striking contrast, the expression and release of the neutrophil chemoattractant IL-8 was not inducible. To determine the underlying mechanisms responsible for the induction of this differential chemokine pattern, we stimulated monocytes with UV- and heat-inactivated (56 degrees C and 100 degrees C) influenza A virus. In comparison with fully infectious influenza A, 56 degrees C-inactivated virus induced a strong production of MCP-1, MIP-1 alpha, and IP-10, while the release of MIP-1 alpha and IP-10 was substantially lower after exposure to UV-inactivated virus. No chemokine expression was found after stimulation with 100 degrees C-inactivated influenza A virus. Our data indicate that, contingent upon the chemokine examined, the maximal induction depends on the unrestricted infectivity of the virus, the unaltered hemagglutinin molecule, or the intact viral RNA. This diversified chemokine production may enable the infected host to mount an efficient antiviral response against infective and noninfective virus particles.