Inhibition of the phagocytic action of leucocytes by mumps and influenza viruses

Phage-Phagocyte Interactions and Their Implications for Phage Application as Therapeutics

Phagocytes are the main component of innate immunity. They remove pathogens and particles from organisms using their bactericidal tools in the form of both reactive oxygen species and degrading enzymes-contained in granules-that are potentially toxic proteins. Therefore, it is important to investigate the possible interactions between phages and immune cells and avoid any phage side effects on them. Recent progress in knowledge concerning the influence of phages on phagocytes is also important as such interactions may shape the immune response. In this review we have summarized the current knowledge on phage interactions with phagocytes described so far and their potential implications for phage therapy. The data suggesting that phage do not downregulate important phagocyte functions are especially relevant for the concept of phage therapy.

Bacteriophage interactions with phagocytes and their potential significance in experimental therapy

Bacteriophages are among the most numerous creatures on earth and they are omnipresent. They are thus in constant natural contact with humans and animals. However, the clinical and technological use of bacteriophages has also become more frequent, which is why all aspects of phage–mammal interactions need to be explored. Bacteriophages are able to interact with mammalian phagocytes. They may inhibit the phagocytosis of bacteria, but they may also undergo phagocytosis themselves. The ability of bacteriophages to reduce reactive oxygen species production by polymorphonuclear leukocytes in the presence of bacteria or their endotoxins was also confirmed. Studies show that the high immunogenicity of bacteriophages may also be employed in anti-tumor treatment. The present knowledge of phage interactions with cellular components of the mammalian immune system is sparse and insufficient, especially considering the increasing interest in the application of these viruses in human life. We believe that continuation of such research is indispensable.

Depression of rat neutrophil exudation and motility by influenza virus

Purified influenza A and B viruses (3000 HA units) were injected intraperitoneally into rats. 1 h later the animals were given starch solution intraperitoneally, after which the number and composition of the exuded cells were determined at intervals. Both influenza A and B viruses depressed neutrophil exudation into the peritoneal cavity for a period of 10 to 17 h after the starch injection. The exudation of leukocytes other than neutrophils (a mixture of mononuclear cells and 5% to 10% eosinophils) was depressed for 17 h after starch injection by influenza A virus. When tested in vitro by a modification of the Boyden method, the peritoneal exudate neutrophils from virus-treated animals exhibited significantly depressed chemotaxis and consistently, although not always significantly, reduced chemokinesis (migration in the presence of a chemoattractant without a gradient) and random locomotion. Both influenza A and B viruses inhibited in vitro the motility of starch-induced peritoneal exudate neutrophils in Boyden chambers after a virus-cell interaction of 60 min at 37 degrees C. The present findings support the concept that impaired neutrophil exudation caused by depressed motility is one mechanism responsible for the increased susceptibility to bacterial superinfection during influenza.

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.

The NBT (Nitroblue Tetrazolium) activity of neutrophil granulocytes in patients with influenza A infection

The NBT activity of granulocytes from 11 influenza patients was determined during the acute stage of the disease and 6-8 weeks after recovery. The NBT activity was generally higher during influenza than after recovery. In the presence as well as in the absence of the patient's serum the differences were significant both without and with Escherichia coli stimulation.

The effect of Sendai virus infection on bactericidal and transport mechanisms of the murine lung

Pulmonary virus infections predispose to bacterial infections in the lung. The mechanism of this effect was studied by quantitative comparison of the effects of airborne acute viral infection on pulmonary transport vs. in situ bactericidal mechanisms in mice. Animals infected by aerosol with 10(4) TCID(50) of Sendai virus developed pathologic pulmonary changes of interstitial pneumonitis, bronchial epithelial desquamation, and peribronchial mononuclear cell infiltration 7 days later. At that time, the mice were challenged with an aerosol of viable (32)P-labeled Staphylococcus aureus. Pulmonary bactericidal activity and physical transport by the lung were determined by the determination of viable staphylococcal and (32)P radiotracer counts respectively at 4, 24, 48, and 72 hr after bacterial challenge. Infected mice showed a significant decrease from normal in the rate of reduction of viable bacterial counts in the first 4 hr after challenge followed by a proliferation of the staphylococci. By contrast, radiotracer removal rates at 4 and 24 hr were similar in infected and noninfected mice. There was a small but significant retention of (32)P in the lungs of the infected animals at the later periods. These data demonstrate that bacterial multiplication associated with virus infection of lungs is related to defects in in situ bactericidal (phagocytic) mechanisms rather than transport mechanisms of the lung, despite histologic evidence of extensive destruction of bronchial-ciliated epithelium.