Influenza virus replication in human alveolar macrophages.

Studies with animal models suggest that alveolar macrophages may be important cells in some respiratory virus infections, but little is known about the role of these cells in virus infections in man. In this study human alveolar macrophages were obtained by fibreoptic bronchoscopy and infected in vitro with a variety of influenza viruses. After infection with the NWS strain of influenza virus the haemagglutinin and nucleoprotein viral antigens were demonstrated in greater than 90% of cells at 24 h by immunofluorescence with specific antisera. There was no cytopathic effect at this time, and no virus release was detected by plaque assay of culture fluids on MDCK cells. Alveolar macrophages were also infected with a human vaccine strain (H1N1) of influenza virus and with two recent isolates (H1N1 and H3N2). In each case viral nucleoprotein antigen was produced in 10-20% of the cells by 24 h postincubation, but there was no release of infectious virus. There was no cytopathic effect and the phagocytosis of IgG-coated latex beads was unimpaired 24 h after in vitro infection.