Attempts to Influence the Incomplete Reproductive Cycle of Influenza Virus in HeLa Cells by Antibodies

Abstract

The question whether antibodies are truly incapable of entering cells was studied in HeLa cultures infected with the PR8 strain of influenza A virus and in uninfected populations treated with antiviral or normal rabbit sera. The results were evaluated by staining of cells vitally or after acetone fixation with fluorescein isothiocyanate-coupled antibodies to PR8 virus or rabbit γ-globulin, as well as by hemagglutination and complement fixation tests. Replication of influenza virus in HeLa cells is restricted to one cycle because solely noninfectious hemagglutinins (NIHA) are produced. The ultimate yields of NIHA and the maximal percentage of cells containing influenza antigens were strictly proportional to the dose of seed virus employed. Few, if any, cells reacted with fluorescent antibodies in the second passage, and none after further passages. Differential staining of acetone-fixed cells from infected, untreated cultures showed that S antigen developed first and remained restricted to the nucleus. V antigen appeared initially in the region of the Golgi apparatus, from where it spread throughout the cytoplasm and, in time, reached the cell surface, as evident from vital staining with labeled anti-PR8 γ-globulin. Exposure of infected or uninfected cultures to antiviral or normal rabbit serum provided the following data: As the data stand, no evidence was obtained to indicate entry of antibodies into normal or infected cells in sufficient amounts to be detectable by the immunofluorescence techniques employed or by reduction in production of viral antigens.