Modulation of murine macrophage responses stimulated with influenza glycoproteins

Abstract

Previously it was reported that influenza virus stimulated, nonspecific resistance was largely due to its glycoproteins, hemagglutinin (HA) and neuraminidase (NA). The enhancement of natural killer cell activity was the intrinsic property of NA and HA. In the present study, the stimulatory effect of these glycoproteins on the murine peritoneal macrophages was studied. Electrophoretically purified glycoproteins, NA and HA, of influenza virus A/USSR/90/77 (H1N1) were administered intraperitoneally to C3H/HeN mice, with or without stearyl tyrosine (ST). Macrophages were isolated and were restimulated with phorbol myristate acetate. H2O2 secretion was determined by horseradish peroxidase dependent oxidation of phenol red assay. HA enhanced H2O2 secretion only in the presence of ST (60 nmol∙mg−1∙h−1), whereas NA alone stimulated H2O2 secretion (83 nmol∙mg−1∙h−1), by 6-fold over control (13 nmol∙mg−1∙h−1), and this stimulation was further increased (136 nmol∙mg−1∙h−1) in the presence of ST. Interleukin 1 (IL-1) activity was determined by using D10.G4.1 cells. There was a little stimulation of IL-1 activity (<1 U/mL) of macrophages isolated from HA-primed or HA+ST-primed mice restimulated with HA. On the other hand, IL-1 activity of macrophages isolated from NA-primed mice restimulated with NA significantly increased (102 U/mL) over control (<1 U/mL), and an additional 2-fold increase (231 U/mL) resulted when macrophages from NA + ST-primed mice were used. Tumor necrosis factor (TNF) activity was examined by using L929 cells. Negligible TNF activity was observed in macrophages isolated from either HA-primed or HA + ST-primed mice restimulated with HA. Macrophages from NA-primed mice restimulated with NA increased TNF activity from 2.1 (control) to 20 U/mL, and this activity increased further to 536 U/mL in macrophages from NA + ST-primed mice. NA of N2 subtype also possessed the potential to stimulate TNF activity. ST had an enhancing effect on the stimulatory potential of proteins. Our present results supported by our earlier findings show that NA, even though enzymatically inactive, can stimulate nonspecific resistance mechanisms and probably plays an important role in the control of early influenza infection. Key words: influenza, glycoproteins, modulation, macrophages.