Replication of Influenza A Virus in Suspensions of Ehrlich Ascites Tumor Cells Kept in vitro. Results Obtained by the Fluorescent Antibody Technique

Abstract

Suspensions of Ehrlich ascites tumor cells maintained in vitro were infected with the tumor-adapted strain WSA of influenza A₀ virus and studied by the fluorescent antibody technique. Replication was found to follow the sequence established for influenza virus infection in several cell systems: The nucleoprotein antigen became first detectable in the cell nucleus 2 h after infection and could be seen in the cytoplasm 2 to 3 h later. The hemagglutinating antigen remained in the cytoplasm throughout, where it first appeared 3 h after infection. A constant feature not previously described was the emergence of brightly fluorescing granular spots in the cytoplasm during the first 2 h of infection. These early spots did not seem to represent the virus input, since their number per infected cell was independent of the multiplicity of infection. They could be revealed with the aid of post-infectious mouse sera, but not with sera of mice immunized with killed virus. They may represent a new antigenic entity appearing early in the replication cycle.