Role of serum in stimulation of polymorphonuclear leukocyte, luminol-dependent chemiluminescence by influenza A

Granulocyte membrane perturbation activates oxidative metabolism with the release of highly reactive species (O₂^-, H₂O₂, OH·, and 'O₂) and emission of light (chemiluminescence (CL)). Using the CL response as a measure of oxidative metabolism, we assayed the effects of influenza A on the granulocyte respiratory burst. Human polymorphonuclear leukocytes (PMNs) were isolated by Ficoll-Hypaque cushioning and dextran sedimentation. The isolated PMNs were incubated with egg-grown influenza A (H₃N₂) virus, or a medium control, in the presence of 1 μM luminol and fresh autologous (10%). No light emission occurred during the incubation of PMNs with the medium control. Influenza A (33 to 50% egg-infective-doses (EID₅₀):1 PMN) stimulated PMN light emission with a maximal response (48,386 ± 10,764 cpm/10⁶ PMN) occurring at 37°C. The degree of CL was dependent on the virus dose with a diminished response (6,041 ± 3,200 cpm/10⁶ PMN) occurring at a lower infectivity of 10 EID₅₀:1 PMN. Chemiluminescence responses were similar with infective and with noninfective virus particles (heat inactivated, 56°C x 2 h). Fresh serum was necessary for the influenza virus to cause a CL response. A significant correlation (p < 0.01) existed between the level of light emission and the hemagglutination-inhibiting (HI) antibody titer to influenza A of the autologous serum. Virus in the absence of detectable antibody did not stimulate CL. The virus-associated CL was completely inhibited if autologous serum was heated (56°C x 30 min) or if the PMNs were pretreated with cytochalasin B (5 mcg/ml x 5 min). These findings suggest that influenza A-associated PMN CL requires antibody, complement, and phagocytosis. In addition, PMNs incubated with influenza virus and autologous serum showed a marked inhibition (up to 95%) of the CL response to zymosan particles when compared with non-virus treated cells. The degree of inhibition was directly related to the level of HI antibody in the serum. Our data suggest that influenza virus inhibits chemiluminescence by consuming serum factors necessary to opsonize the zymosan particles rather than by a direct virus-induced defect of the PMN.