Effect of influenza virus infection on phagocytic and cytopeptic capacities of guinea pig macrophages

Pathogenesis of viral infections

The article considers factors that influence pathogenesis, initiation of infection, dissemination of virus within a host, lytic viral infections, viral immunosuppression, viral immunopathology, and viral oncogenesis.

Depressed chemiluminescence response by influenza virus is enhanced after conjugation of viral subunits to muramyl dipeptide

The effect on respiratory burst of murine spleen cells after in vitro exposure to influenza virus, subunits, or subunits conjugated to muramyl dipeptide (MDP) was studied by luminol-dependent chemiluminescence (CL) in response to stimulation by zymosan. CL induced by infectious influenza A virus was depressed but could be elevated to normal levels when MDP was added together with a low, but not with a high, dose of the virus. Profound depression of CL was induced by high doses of influenza A/Brazil, A/Bangkok, and B/Singapore subunits. The same amounts of viral subunits conjugated to MDP restored or even enhanced the CL responses of spleen cells from BALB/c and C57BL/6 mice. Splenic cells from BALB/c mice generated higher levels of CL than did cells from C57BL/6 mice.

Depression of chemiluminescence response in mouse spleen cells by infective and inactivated influenza virus

The effect on respiratory burst of murine splenic cells after exposure to influenza viruses was studied by luminol-dependent chemiluminescence (CL). Infectious influenza A and B viruses considerably depressed the zymosan-induced CL response of the cells. Commercially available trivalent influenza virus vaccines also depressed CL activity. The whole-virus vaccine induced the greatest inhibition of the CL response, followed by the subunit and the split-virus vaccines. Virus-induced depression of CL was observed in the unseparated and in the granulocyte-enriched populations but no apparent effect was found in the lymphocyte-enriched populations. Prior sensitization of mice with representative, inactivated prototype strains of human influenza A and B viruses depressed the moderate CL induced by infectious influenza viruses. These results indicate that both infectious and inactivated influenza viruses impair the generation of the respiratory burst.

Replication of five bovine respiratory viruses in cultured bovine alveolar macrophages

The replication of five bovine respiratory viruses in cultured bovine alveolar macrophages (BAM) was investigated. The bovine herpesvirus DN-599 strain did not cause cytophatic effect (CPE), extracellular virus and intracellular antigen were not demonstrated. Although a small number of bovine respiratory syncytial virions were consistently released and about 1 percent of the BAM were fluorescence antibody (FA) positive the virus caused no CPE. Infectious bovine rhinotracheitis virus caused CPE at an input multiplicity of about 0.5, and 5 percent of the BAM were FA positive. Both bovine parainfluenza-3 and bovine viral diarrhea viruses caused CPE, infective virions were released and considerable proportions of the BAM were FA positive.

Interaction of influenza virus with swine alveolar macrophages: Influence of anti-virus antibodies and cytochalasin B

Interactions between swine influenza virus and swine alveolar macrophages were studied in vitro. Cell lysis occurred 24 h post-infection and was shown by a decreased neutral red uptake. UV inactivation of the influenza virus, or the addition of anti-influenza antibodies suppressed the virus-induced macrophage lysis. Inversely, pretreatment of swine alveolar macrophages by a phagocytosis inhibitor, namely cytochalasin B, increased the cell susceptibility to virus-induced lysis.

The present in vitro studies support the hypothesis that defects in pulmonary antibacterial mechanisms associated with influenza infections are partly due to a direct toxic effect of the virus on alveolar macrophages. Furthermore, the studies show that virus-induced macrophage lysis is influenced by specific humoral immune responses and by modifications in microfilament cell functions.

Influenza A virus-induced polymorphonuclear leukocyte dysfunction

Previous studies have shown that influenza A virus can activate the polymorphonuclear leukocyte (PMN) respiratory burst and that upon subsequent stimulation of the cell there is depressed metabolic function. We examined the mechanism by which influenza virus causes PMN dysfunction by measuring the effect upon the chemiluminescent activity of cells of varying the type of influenza virus used, the period of time that cells were exposed to virus, and the secondary stimulus that was used. The various types of intact influenza virus elicited different amounts of chemiluminescent activity, but when cells were subsequently stimulated with phorbol myristate acetate, each virus caused equivalent depression of the PMN response. Purified glycoproteins incorporated into a liposome structure similarly stimulated the PMN chemiluminescence, yet did not induce PMN dysfunction. Depressed PMN function was noted after as little as 5 min of incubation of cells with virus and occurred to both receptor-dependent (zymosan, N-formylmethionyl-leucyl-phenylalanine, and phorbol myristate acetate) and -independent (calcium ionophore A23187) stimuli.

Influenza A virus-induced polymorphonuclear leukocyte dysfunction in the pathogenesis of experimental pneumococcal otitis media

The role of influenza A virus-induced polymorphonuclear leukocyte and eustachian tube dysfunction in the pathogenesis of acute purulent otitis media was studied in chinchillas. Polymorphonuclear leukocyte function, middle ear pressure, and the incidence of pneumococcal otitis media were observed after intranasal inoculation with influenza A virus, Streptococcus pneumoniae, or both. Results showed that depressed negative middle ear pressure and polymorphonuclear leukocyte chemiluminescence and chemotactic activity occurred after influenza inoculation, but not after inoculation with pneumococcus alone. The greatest incidence of pneumococcal otitis media occurred when the pneumococcus was inoculated just before the time of influenza-induced polymorphonuclear leukocyte dysfunction and negative middle ear pressure. Animals that had unilateral tympanostomy tubes placed before inoculation of influenza with pneumococcus showed no difference in the occurrence of pneumococcal otitis media in ventilated and nonventilated ears, suggesting that polymorphonuclear leukocyte dysfunction contributes more to the pathogenesis of pneumococcal otitis media than does negative middle ear pressure in this animal model.

Depression of monocyte and polymorphonuclear leukocyte oxidative metabolism and bactericidal capacity by influenza A virus

Decreased host defense against bacterial disease associated with influenza infection may be related to virus-induced changes in phagocytic cell function. Influenza A virus initiates the respiratory burst in peripheral blood monocytes and polymorphonuclear leukocytes, with a peak chemiluminescent response approximately 3 min after virus is added to the cells in vitro. Electron micrographs of phagocytic cells incubated with influenza virus demonstrated virus attached to the cell membrane and within phagocytic vacuoles. After 20 min of incubation of the virus with phagocytic cells, the chemiluminescent response to opsonized zymosan or phorbol myristate acetate was decreased by 30 to 90%. Phagocytic activity of monocytes and polymorphonuclear leukocytes incubate with influenza virus was normal, but the bactericidal activity was significantly depressed. Influenza A virus therefore stimulates an oxidative burst in monocytes as well as polymorphonuclear leukocytes, leading to a subsequent depression of the oxidative metabolic response and bactericidal capacity of the phagocytic cells.

Alveolar macrophage ingestion and phagosome-lysosome fusion defect associated with virus pneumonia

Virus-induced suppression of pulmonary phagocytic defenses is associated with defects in the intracellular processing of bacteria by alveolar macrophages. To determine whether the intracellular defect is related to a failure in phagosomelysosome fusion, mice were infected with a sublethal dose of Sendai virus, and the capacity of phagocytic cells, obtained by lung lavage, to exhibit phagosomelysosome fusion was quantitated during the course of the viral infection. Lysosomes of alveolar macrophages were prelabeled with acridine orange, the cells were challenged with Candida krusei, and fusion was determined with fluorescence microscopy by the discharge of the dye into the yeast-containing phagosome. Ultrastructural cytochemical studies verified the validity of the fluorescent fusion assay. Simultaneous experiments were performed to determine whether the viral infection also suppressed phagocytic ingestion by alveolar macrophages. Phagosome-lysosome fusion was progressively inhibited during the viral infection, reaching a low at day 7 when only 13 +/- 3% of the phagocytic cells fused as compared with 97 +/- 3% in cells from uninfected control animals; respectively, 55 +/- 5% as compared with 74 +/- 2% of the phagocytic cells contained yeasts. Thereafter, phagosome-lysosome fusion progressively increased reaching near normal levels (92 +/- 3%) on day 17 of the infection. At the same time period, phagocytic uptake was enhanced to a level where 97 +/- 3% of the cells contained yeasts. These data demonstrated that virus-induced suppression of intrapulmonary killing of bacteria involves functional lesions that retard the ingestion of inhaled organisms by alveolar macrophages and inhibit intracellular processing by degradative lysosomal enzymes by interfering with phagosome-lysosome fusion.