Antibody-neutralized Avian Infectious Bronchitis Virus in Chicken Embryo Kidney Cells: Entry and Degradation

Abstract

SUMMARY The interaction of avian infectious bronchitis virus with the chicken embryo kidney cell was studied before and after neutralization by homotypic antiserum containing only 7 s (IgG) antibody. Entry of virus into the cell, measured by the ability of antibody to neutralize only extracellular virus, occurred at 37 ° and 25 ° but not at 4 °. To study entry of neutralized virus, infectious bronchitis virus was adsorbed and then neutralized at 4 °. The cells were incubated at 4 ° (control), 25 °, or 37 °. Antibody was dissociated from extracellular neutralized infectious bronchitis virus with a pH 2.o buffer solution which subsequently reactivated the virus. This acid treatment for Io sec. did not dissociate the virus from the cell or injure the cell. Antibody did not enhance or suppress elution of infectious bronchitis virus from the cell. Neutralized infectious bronchitis virus either merged with the cytoplasmic membrane or was pinocytosed at 37 ° and 25°; however, the neutralized virus remained extracellular at 44 °. After the neutralized virus had interacted with the cytoplasmic membrane, it was not readily accessible to acid and could not be reactivated. The entry of virus without antibody was faster than that for virus with antibody. After I hr at 37 °, the % uncoated virus RNA in cells with unneutralized virus remained essentially constant. However, in cells with neutralized virus the % uncoated virus RNA decreased and the acid-soluble material increased simultaneously.