CHARACTERIZATION OF INFLUENZA VIRUS-INDUCED LEUKOCYTE ADHERENCE TO HUMAN UMBILICAL VEIN ENDOTHELIAL-CELL MONOLAYERS

The adherence of undifferentiated Cr-51-labeled HL-60 (0.5 x 10(6) HL- 60 cells/well) cells was monitored on influenza virus-infected HUVEC m onolayers. Whereas only 3.0 +/- 1.6% (n = 36) of HL-60 cells adhered t o uninfected HUVEC, adherence was increased to 41.7 +/- 2.2% (n = 6), 79.7 +/- 1.2% (n = 6), 83.9 +/- 0.7% (n = 6), and 84.4 +/- 0.5% (n = 6 ) on HUVEC infected for 7 h at a MOI of 1, 3, 6, and 9, respectively. In comparison, HL-60 cell adherence increased to 35% when HUVEC monola yers were stimulated with LPS (0.2-20 mug) for 4 h. Increased adherenc e to infected HUVEC occurred at 5 h postinfection, peaked at 7 h, and was maintained at 24 h postinfection. Active virus and metabolically a ctive endothelial cells were required to mediate the virus-induced adh erence. E-selectin and ICAM-1 Ag were upregulated 78.3- and 4.1 -fold, respectively, by LPS (0.02-20 mug, 4 h) whereas virus infection (7 h) only increased these proteins 2.6- and 1.4-fold with a MOI greater-th an-or-equal-to 16. Although the time courses of expression for both ad hesion molecules after LPS treatment or virus infection were similar, the difference in the magnitude of upregulation suggests that virus-in duced adherence is not a result of upregulation of E-selectin and ICAM -1. In contrast, surface expression of HA is involved in HL-60 cell ad herence to virus-infected HUVEC because (1) the time course and magnit ude of HA Ag expression paralleled the time course and magnitude of HL -60 cell adherence after virus infection of HUVEC; (2) HL-60 cell aggr egates were absent on infected HUVEC monolayers in the presence of ant i-HA; (3) HL-60 cells competed with RBC for infected endothelial cells stained for cellular HA Ag and (4) anti-HA abolished the virus-induce d adherence. Furthermore, it appears that HL-60 cells are binding dire ctly to HA because HL-60 cell adherence to a cell-free surface was inc reased if virus was prebound and neuraminidase treatment of HL-60 cell s prevented the HL-60 cell adherence to influenza virus-infected endot helial monolayers.