Influenza A virus-induced polymorphonuclear leukocyte dysfunction

Influenza Virus Infects and Depletes Activated Adaptive Immune Responders

Influenza infections cause several million cases of severe respiratory illness, hospitalizations, and hundreds of thousands of deaths globally. Secondary infections are a leading cause of influenza's high morbidity and mortality, and significantly factored into the severity of the 1918, 1968, and 2009 pandemics. Furthermore, there is an increased incidence of other respiratory infections even in vaccinated individuals during influenza season. Putative mechanisms responsible for vaccine failures against influenza as well as other respiratory infections during influenza season are investigated. Peripheral blood mononuclear cells (PBMCs) are used from influenza vaccinated individuals to assess antigen-specific responses to influenza, measles, and varicella. The observations made in humans to a mouse model to unravel the mechanism is confirmed and extended. Infection with influenza virus suppresses an ongoing adaptive response to vaccination against influenza as well as other respiratory pathogens, i.e., Adenovirus and Streptococcus pneumoniae by preferentially infecting and killing activated lymphocytes which express elevated levels of sialic acid receptors. These findings propose a new mechanism for the high incidence of secondary respiratory infections due to bacteria and other viruses as well as vaccine failures to influenza and other respiratory pathogens even in immune individuals due to influenza viral infections.

Novel case of an adult with toxic shock syndrome following COVID-19 infection

Purpose

To report a case of an adult who developed toxic shock syndrome following COVID-19 infection.

Observations

A 28-year-old female tested positive for COVID-19. 19 days later, she developed a fever, rash and a burning sensation in both eyes. Her examination revealed mild ocular inflammation with bilateral eyelid and conjunctival involvement. Skin biopsy favored a diagnosis of toxic shock syndrome. She was initiated on corticosteroid eye drops and her ocular symptoms resolved three days later.

Conclusion and importance

Toxic shock syndrome is almost always associated with conjunctival inflammation. To our knowledge, this is the first report of an adult patient with toxic shock syndrome following COVID-19 infection. The association between toxic shock syndrome and COVID-19 is unclear; however, patients should be vigilant for symptoms as toxic shock syndrome can progress rapidly and cause multi-organ failure.

Differential Ability of Pandemic and Seasonal H1N1 Influenza A Viruses To Alter the Function of Human Neutrophils

A long-standing notion is that IAV inhibits normal neutrophil function and thereby predisposes individuals to secondary bacterial infections. Here we report that seasonal H1N1 IAV primes human neutrophils for enhanced killing of Staphylococcus aureus. Moreover, we provide a comprehensive view of the changes in neutrophil gene expression during interaction with seasonal or pandemic IAV and report how these changes relate to functions such as bactericidal activity. This study expands our knowledge of IAV interactions with human neutrophils.

Neutrophils are essential cells of host innate immunity. Although the role of neutrophils in defense against bacterial and fungal infections is well characterized, there is a relative paucity of information about their role against viral infections. Influenza A virus (IAV) infection can be associated with secondary bacterial coinfection, and it has long been posited that the ability of IAV to alter normal neutrophil function predisposes individuals to secondary bacterial infections. To better understand this phenomenon, we evaluated the interaction of pandemic or seasonal H1N1 IAV with human neutrophils isolated from healthy persons. These viruses were ingested by human neutrophils and elicited changes in neutrophil gene expression that are consistent with an interferon-mediated immune response. The viability of neutrophils following coculture with either pandemic or seasonal H1N1 IAV was similar for up to 18 h of culture. Notably, neutrophil exposure to seasonal (but not pandemic) IAV primed these leukocytes for enhanced functions, including production of reactive oxygen species and bactericidal activity. Taken together, our results are at variance with the universal idea that IAV impairs neutrophil function directly to predispose individuals to secondary bacterial infections. Rather, we suggest that some strains of IAV prime neutrophils for enhanced bacterial clearance.

IMPORTANCE A long-standing notion is that IAV inhibits normal neutrophil function and thereby predisposes individuals to secondary bacterial infections. Here we report that seasonal H1N1 IAV primes human neutrophils for enhanced killing of Staphylococcus aureus. Moreover, we provide a comprehensive view of the changes in neutrophil gene expression during interaction with seasonal or pandemic IAV and report how these changes relate to functions such as bactericidal activity. This study expands our knowledge of IAV interactions with human neutrophils.

Influenza A virus alters pneumococcal nasal colonization and middle ear infection independently of phase variation

Streptococcus pneumoniae (pneumococcus) is both a widespread nasal colonizer and a leading cause of otitis media, one of the most common diseases of childhood. Pneumococcal phase variation influences both colonization and disease and thus has been linked to the bacteria's transition from colonizer to otopathogen. Further contributing to this transition, coinfection with influenza A virus has been strongly associated epidemiologically with the dissemination of pneumococci from the nasopharynx to the middle ear. Using a mouse infection model, we demonstrated that coinfection with influenza virus and pneumococci enhanced both colonization and inflammatory responses within the nasopharynx and middle ear chamber. Coinfection studies were also performed using pneumococcal populations enriched for opaque or transparent phase variants. As shown previously, opaque variants were less able to colonize the nasopharynx. In vitro, this phase also demonstrated diminished biofilm viability and epithelial adherence. However, coinfection with influenza virus ameliorated this colonization defect in vivo. Further, viral coinfection ultimately induced a similar magnitude of middle ear infection by both phase variants. These data indicate that despite inherent differences in colonization, the influenza A virus exacerbation of experimental middle ear infection is independent of the pneumococcal phase. These findings provide new insights into the synergistic link between pneumococcus and influenza virus in the context of otitis media.

Differential effect of prior influenza infection on alveolar macrophage phagocytosis of Staphylococcus aureus and Escherichia coli: involvement of interferon-gamma production

The influenza A virus is one of the main causes of respiratory infection. Although influenza virus infection alone can result in pneumonia, secondary bacterial infection combined with the virus is the major cause of morbidity and mortality. Interestingly, while influenza infection increases susceptibility to some bacteria, including Streptococcus pneumoniae, Staphylococcus aureus (S. aureus), and Haemophilus influenzae, other bacteria such as Escherichia coli (E. coli) and Klebsiella pneumoniae are not associated with influenza infection. The reason for this discrepancy is not known. In this study, it was found that prior influenza virus infection inhibits murine alveolar macrophage phagocytosis of S. aureus but not of E. coli. Here, the mechanism for this inhibition is elucidated: prior influenza virus infection strongly increases interferon gamma (IFN-γ) production. Furthermore, it was shown that IFN-γ differentially affects alveolar macrophage phagocytosis of S. aureus and E. coli. The findings of the present study explain how influenza virus infection increases susceptibility to some bacteria, such as S. aureus, but not others, and provides evidence that IFN-γ might be a promising target for protecting the human population from secondary bacterial infection by influenza.

Type I IFNs mediate development of postinfluenza bacterial pneumonia in mice

Influenza-related complications continue to be a major cause of mortality worldwide. Due to unclear mechanisms, a substantial number of influenza-related deaths result from bacterial superinfections, particularly secondary pneumococcal pneumonia. Here, we report what we believe to be a novel mechanism by which influenza-induced type I IFNs sensitize hosts to secondary bacterial infections. Influenza-infected mice deficient for type I IFN-alpha/beta receptor signaling (Ifnar-/- mice) had improved survival and clearance of secondary Streptococcus pneumoniae infection from the lungs and blood, as compared with similarly infected wild-type animals. The less effective response in wild-type mice seemed to be attributable to impaired production of neutrophil chemoattractants KC (also known as Cxcl1) and Mip2 (also known as Cxcl2) following secondary challenge with S. pneumoniae. This resulted in inadequate neutrophil responses during the early phase of host defense against secondary bacterial infection. Indeed, influenza-infected wild-type mice cleared secondary pneumococcal pneumonia after pulmonary administration of exogenous KC and Mip2, whereas neutralization of Cxcr2, the common receptor for KC and Mip2, reversed the protective phenotype observed in Ifnar-/- mice. These data may underscore the importance of the type I IFN inhibitory pathway on CXC chemokine production. Collectively, these findings highlight what we believe to be a novel mechanism by which the antiviral response to influenza sensitizes hosts to secondary bacterial pneumonia.

Elevated levels of high mobility group box chromosomal protein-1 (HMGB-1) in sera from patients with severe bacterial pneumonia coinfected with influenza virus

Plasma levels of high mobility group box chromosomal protein-1 (HMGB-1), as well as of other inflammatory molecules such as interleukin-6 (IL-6), regulated on activation normal T-cell expressed and secreted (RANTES), and soluble intercellular adhesion molecule-1 (sICAM-1), were determined in patients with bacterial pneumonia coinfected with influenza virus. HMGB-1 levels were significantly elevated in these patients compared to patients undergoing mild bacterial pneumonia alone (p < 0.01). Among cases of coinfection, we found a significant correlation between the concentration of HMGB-1 and white blood cell counts (p < 0.05, r = 0.612). Levels of IL-6 were also higher in these patients than in patients with bacterial pneumonia alone (p < 0.05), despite similar levels of RANTES and sICAM-1 in the 2 groups. These data suggest that HMGB-1 is involved in the pathogenesis of severe bacterial pneumonia coinfected with influenza virus.

Disease severity in patients with simultaneous influenza and bacterial pneumonia

OBJECTIVE

To determine the differences in the clinical features of bacterial pneumonia patients between patients co-infected with influenza virus or not co-infected.

METHODS

Fifteen adult patients with bacterial pneumonia (7 men and 8 women) who also tested positive for influenza virus antigen were compared with those with bacterial pneumonia alone (n=28).

RESULTS

Complications with chronic lung diseases were more frequently found in bacterial pneumonia patients with influenza virus infection, compared with those who had bacteria pneumonia alone. Statistical differences were also found in body temperature, and heart rates between the two groups. CRP levels, chest X-ray infiltrates and the severity of pneumonia, as determined using the criteria of the Japan Respiratory Society (JRS) and/or the Infectious Diseases Society of America (IDSA), were also significantly worse in patients of bacterial pneumonia infected with influenza virus, than in those who had bacterial pneumonia alone.

CONCLUSIONS

The severity of pneumonia in patients co-infected with influenza virus and bacteria was significantly higher than in those infected with bacteria alone. These data suggested that the influenza virus infection enhanced the bacterial pneumonia. Further study of the pathogenesis of the synergic interaction between influenza virus and bacteria is warranted.

Both influenza-induced neutrophil dysfunction and neutrophil-independent mechanisms contribute to increased susceptibility to a secondary Streptococcus pneumoniae infection

Since secondary Streptococcus pneumoniae infections greatly increase the mortality of influenza infections, we determined the relative roles of neutrophil-dependent and -independent mechanisms in increased susceptibility to S. pneumoniae during influenza infection. Mice infected with influenza for 6 days, but not 3 days, showed a significant increase in susceptibility to S. pneumoniae infection compared to mice not infected with influenza. There was significant neutrophil accumulation in the lungs of S. pneumoniae-infected mice regardless of whether or not they were infected with influenza for 3 or 6 days. Depletion of neutrophils in these mice resulted in increased susceptibility to S. pneumoniae in both the non-influenza-infected mice and mice infected with influenza for 3 days but not in the mice infected with influenza for 6 days, indicating that a prior influenza infection of 6 days may compromise neutrophil function, resulting in increased susceptibility to a S. pneumoniae infection. Neutrophils from the lungs of mice infected with influenza for 3 or 6 days exhibited functional impairment in the form of decreased phagocytosis and intracellular reactive oxygen species generation in response to S. pneumoniae. In addition, neutrophil-depleted mice infected with influenza for 6 days were more susceptible to S. pneumoniae than neutrophil-depleted mice not infected with influenza, indicating that neutrophil-independent mechanisms also contribute to influenza-induced increased susceptibility to S. pneumoniae. Pulmonary interleukin-10 levels were increased in coinfected mice infected with influenza for 6 days but not 3 days. Thus, an influenza infection of 6 days increases susceptibility to S. pneumoniae by both suppression of neutrophil function and by neutrophil-independent mechanisms such as enhanced cytokine production.

Decreased bacterial clearance from the lungs of mice following primary respiratory syncytial virus infection

Virus respiratory infections often precede bacterial pneumonia in healthy individuals. In order to determine the potential role of respiratory syncytial virus (RSV) in bacterial secondary infections, a mouse sequential pulmonary infection model was developed. Mice were exposed to RSV then challenged with Streptococcus pneumoniae (StPn). Exposure of BALB/c mice to 10(6)-10(7) plaque forming units (pfu) of virus of RSV significantly decreased StPn clearance 1-7 days following RSV exposure. This finding was not restricted to StPn alone: exposure to RSV followed by Staphylococcus aureus (SA) or Pseudomonas aeruginosa(PA) resulted in similar decreases in bacterial clearance. Both bronchoalveolar lavage (BAL) cell counts and pulmonary histopathology demonstrated that RSV-StPn exposed mice had increased lung cellular inflammation compared to mice receiving StPn or RSV alone. The effect of RSV infection on bacterial clearance was dependent on the mouse genetic background: C57BL/6J mice (relatively resistant to RSV infection) demonstrated a modest change in StPn clearance following RSV exposure, whereas FVBN/J mice (similar to the BALB/cJ mice in RSV susceptibility) demonstrated a similar degree of RSV-associated decrease in StPn clearance 7 days following RSV exposure. Neutrophils from the RSV-StPn sequentially exposed BALB/cJ mice were functionally altered-produced greater levels of peroxide production but less myeloperoxidase (MPO) compared to mice receiving StPn alone. These data demonstrate that RSV infection decreases bacterial clearance, potentially predisposing to secondary bacterial pneumonia despite increased lung cellular inflammation, and suggest that functional changes occur in the recruited neutrophils that may contribute to the decreased bacterial clearance.

Immunology of avian influenza virus: a review

Avian influenza virus can cause serious disease in a wide variety of birds and mammals, but its natural host range is in wild ducks, gulls, and shorebirds. Infections in poultry can be inapparent or cause respiratory disease, decreases in production, or a rapidly fatal systemic disease known as highly pathogenic avian influenza (HPAI). For the protection of poultry, neutralizing antibody to the hemagglutinin and neuraminidase proteins provide the primary protection against disease. A variety of vaccines elicit neutralizing antibody, including killed whole virus vaccines and fowl-pox recombinant vaccines. Antigenic drift of influenza viruses appears to be less important in causing vaccine failures in poultry as compared to humans. The cytotoxic T lymphocyte response can reduce viral shedding in mildly pathogenic avian influenza viruses, but provides questionable protection against HPAI. Influenza viruses can directly affect the immune response of infected birds, and the role of the Mx gene, interferons, and other cytokines in protection from disease remains unknown.

Effect of respiratory syncytial virus-antibody complexes on cytokine (IL-8, IL-6, TNF-alpha) release and respiratory burst in human granulocytes

The release of interleukin-8 (IL-8), IL-6, and tumour necrosis factor-alpha (TNF-alpha) from human polymorphonuclear granulocytes (PMN) after exposure to infectious respiratory syncytial virus (RSV) particles was investigated. Our data showed that PMN secreted IL-8 and IL-6 in a time- and RSV-dose-dependent manner. During the RSV exposure, TNF-alpha was not detected in the cell supernatant of PMN. Similar amounts of IL-8 were secreted after either incubation with infectious or UV-inactivated RSV particles. Obviously, PMN bind and phagocytose the viral particles, which leads to the secretion of cytokines. The increased IL-8 secretion was accompanied with an enhanced cytoplasmic IL-8 mRNA steady state level, as shown by Northern blot analysis. The IL-8 secretion pattern from PMN was also studied after its interaction with RSV--antibody complexes. Non-neutralizing monoclonal antibodies (mAb) directed to the RSV fusion protein and glycoprotein were used to generate immune complexes. Only the mAb directed to the RSV fusion protein enhanced the IL-8 release from PMN significantly. In addition, the chemiluminescence response from PMN was analysed after exposure of the cells to RSV particles, RSV-mAb complexes, Ca-ionophore A23187 or N-formyl-methionyl-leucyl-phenylalanine (FMLP). The phagocytosis of RSV inhibited the oxygen radical production induced by the Ca-ionophore A23187 or FMLP. Only RSV-anti-fusion protein mAb complexes generated a chemiluminescence response from PMN. Thus, PMN play an important role in the control of RSV infection.

Depression of chemiluminescence during dengue virus infection of mice: role of cytokines

The effect of dengue type 2 virus (DV) and the cytokines induced by it, on the chemiluminescence (CL) response of mouse spleen cells was studied by luminol-dependent CL. Following intracerebral (i.c.) inoculation of DV, an initial increase in CL response was observed which was followed by a sharp decline from the 4th day post-infection with lowest values on days 5 and 6. DV-induced depression of CL was inhibited by pretreatment of mice with antisera against the two DV-induced cytokines, the cytotoxic factor (CF) and the cytotoxin (CF2), but antisera against the other two helper (HF) or suppressor (SF) cytokines had minimal effect. Inoculation of CF or CF2 into mice depressed the CL in dose-dependent manner at 2 hours but increased it at the 3rd day. Inoculation of HF or SF had no significant effect. Treatment of mice with the cytokines in presence of the specific antisera had an enhancing effect on the CL response. The antisera alone had no effect on CL. Thus, these findings indicate that DV infection impaired the generation of respiratory burst, and the impairment appeared to be mediated by two DV-induced cytokines (CF/CF2). Targetting of the cytokines to M phi was significantly enhanced in the presence of specific anti-cytokine antibodies.

Altered oxidative responses and antibacterial activity of adult rabbit alveolar macrophages exposed to poly(methyl methacrylate)

The effect of poly(methyl methacrylate) (PMMA) on the oxidative responses and antibacterial activity of adult rabbit alveolar macrophages (AM) was studied. PMMA beads (ca. 0.3 micron diameter) elicited an acute respiratory burst within 6-8 min after the addition of the beads. In contrast. Teflon beads of comparable size (ca. 0.2 micron diameter) did not elicit an oxidative burst of AM. An oxidative response was elicited only by those PMMA samples that had affinity for AM adherence. Incubation of AM with PMMA beads reduced the subsequent phorbol myristate acetate (PMA)-elicited oxidative burst by more than 80%. The Staphylococcus epidermidis--RP12 killing capacity of AM was greatly increased when PMMA beads (ca. 0.3 micron) were added to the challenge dose of bacteria. Pre-incubation of freshly harvested AM with PMMA beads, which greatly reduced subsequent PMA-elicited chemiluminescent (CL) responses did not significantly affect the RP12 killing capacity of AM. Our data also suggest that killing of the RP12 strain of S. epidermidis does not involve reactive oxygen intermediates.

Oxidative stress in lungs of mice infected with influenza A virus

As oxidative stress has been implicated in the pathogenesis of certain viral diseases we determined antioxidant and prooxidant parameters in lungs and bronchoalveolar lavage fluid (BALF) of mice infected with a lethal dose of influenza A/PR8/34 virus. Viral infection was characterized by massive infiltration of leukocytes, mainly polymorphonuclear leukocytes, into the alveolar space. The total number of BALF cells increased up to 8-fold (day 3 post-infection) and these cells appeared activated as judged by their increased rates of superoxide anion radical (O2-.) generation upon stimulation. Maximal rates of radical generation by BALF cells during the early stages of infection were 15- or 70-fold higher than those of cells from control animals when expressed per cell or total BALF cells, respectively. At the terminal stages of infection the total capacity of BALF cells to release O2-. declined to approximately 35-fold the control values. Infection also resulted in increased in vivo formation of hydrogen peroxide (H2O2) within the lungs at a time that coincided with the maximal capacity of BALF cells to release O2-.. Whereas pulmonary activities of glutathione peroxidase and reductase remained unaltered, levels of ascorbate in the cell-free BALF decreased significantly during the early stages of the infection and then returned to normal levels and above, late in infection. The oxidation state of the dehydroascorbic acid/ascorbate couple increased concomitantly with the decrease in ascorbate concentrations early in infection and remained elevated throughout the infection. As assessed by the prevention of peroxyl radical-induced loss of phycoerythrin fluorescence, the total antioxidant capacity present in lung tissue homogenate from terminally ill animals was not diminished when compared to that prepared from lungs of control mice. We conclude that although early stages of influenza infection are associated with the presence of oxidative stress in the lung tissue and alveolar fluid lining the epithelial cells, this stress does not appear to overwhelm local antioxidant defenses. The results therefore do not support a direct causative role of oxidative tissue damage in the pathogenesis of influenza virus infection.

The effect of virus particle size on chemiluminescence induction by influenza and Sendai viruses in mouse spleen cells

Suspensions of orthomyxo- and paramyxoviruses are composed of pleomorphic particles ranging from large filaments to small spheres. Influenza and Sendai viruses were separated according to size by gel filtration and the induction of luminol-dependent chemiluminescence (CL) by particles of similar size was studied in suspensions of mouse spleen cells known to contain phagocytes. CL reflects the generation by the cells of reactive oxygen species. CL induction decreased with particle size for both viruses. Compared with small spheres, large influenza filaments were approximately 10 times as efficient in activating cellular light emission while the ratio between large and small Sendai viruses was 3:1. Small Sendai virus particles were also less efficient in lysing red cells and had lower neuraminidase activity. By contrast, with influenza virus, only neuraminidase and not the hemolytic activity decreased with the virus size. When influenza virus filaments were broken into smaller particles by sonication, the capacity to induce chemiluminescence dropped markedly while the hemolytic and hemagglutinating activities increased and neuraminidase activity remained unaltered. These results suggest that the presentation of influenza virus hemagglutinin and neuraminidase glycoproteins in a large particle, leading to extensive receptor crosslinking, may be an important factor in the efficient activation of CL by filamentous influenza virus. We suggest that radical generation as reflected in cellular CL may relate to the toxic in vivo effects that contribute to the pathogenesis of influenza and infections with paramyxoviruses.

Preincubation of bovine blood neutrophils with bovine herpesvirus-1 does not impair neutrophil interaction with Pasteurella haemolytica A1 in vitro

In this study we examined the direct effects of bovine herpesvirus-1 on the interaction of bovine blood neutrophils with Pasteurella haemolytica A1. Preincubation of neutrophils for approximately 2 h in vitro with BHV-1 at a multiplicity of infection of 5:1 had no effect on neutrophil random migration and directed migration to zymosan-activated bovine serum. Neutrophils also were unimpaired in their ability to ingest and kill P. haemolytica A1. Preincubation of neutrophils with BHV-1 did not elicit an oxidative burst, as measured by luminol-enhanced chemiluminescence, nor did it alter neutrophil chemiluminescence in response to opsonized P. haemolytica A1. Prolonged preincubation with BHV-1 for 18-24 h similarly did not affect neutrophil chemiluminescence in response to opsonized P. haemolytica A1. The susceptibility of neutrophils to the lethal effects of crude P. haemolytica cytotoxin also was unaltered by preincubation with BHV-1. We observed no evidence of BHV-1 replication in bovine neutrophils as determined by indirect immunofluorescence and electron microscopy. Previous reports have indicated that active BHV-1 infection alters certain neutrophil functions and results in hypersusceptibility to pulmonary pasteurellosis. Our results suggest that these effects are unlikely to be mediated directly by BHV-1, but instead may reflect the action of endogenous mediators that are released during active BHV-1 infection.

Viral-bacterial synergistic interaction in respiratory disease

In the present review we have identified how viruses can alter the host's susceptibility to bacterial infections by altering both environmental conditions in the lung which favor bacterial replication as well as by suppressing the host's defense mechanisms which prevent clearance of the bacteria. In many instances, these interactions are extremely complex but similar for many viruses. If the virus can overcome the initial host defense mechanisms, which include local antibody and mucus, the virus initiates tissue damage as a result of direct replication within the epithelial cells lining the mucosal surfaces of the respiratory tract. As a result of virus infection, the host cells respond by producing a variety of mediators including various types of interferons, which can alter both virus replication and host response. Replication also produces by-products of virus infection capable of initiating an inflammatory process, which in turn, through release of other mediators, can further modify lung defense mechanisms and encourage bacterial adherence and growth. The bacterium, in turn, releases chemotactic factors which encourage infiltration of specific effector cells into the lung. These effector cells can cause tissue damage and immunopathology, which encourage rapid bacterial growth and may result in death of the animal. In order to be able to control this complicated scenario, it is important either to prevent the initial infection with viruses or to reduce the degree of immunosuppression, so that bacterial clearance can occur rapidly before microcolony formation and extensive lung damage occur. Once a large amount of bacterial replication and lung damage is present, the use of antibiotics is generally of limited value. A schematic illustration of the complexity of the various interactions and counteractions occurring during virus--bacterial synergistic interactions is presented in Fig. 1.

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.

Interactions between human polymorphonuclear leukocytes and influenza virus

The effects of influenza virus A (H3N2) on several functions of human polymorphonuclear leukocytes (PMN) were examined. Incubation of PMN with virus induced chemiluminescence, aggregation, and degranulation of the leukocytes. The amount of chemiluminescence generated increased from 1 X 10(6) to 6 X 10(6) cpm when 2.5 X 10(6) to 2 X 10(7) virus particles were added to 2.5 X 10(6) PMN. Maximal aggregation occurred within 2 min and the response depended on the amount of virus added to the PMN. Release of acid phosphatase by virus-treated PMN was 62 +/- 12% within 1 h compared with 7 +/- 7% by control PMN (P less than 0.005). Incubation of PMN with influenza virus resulted in a diminished phagocytic activity of the phagocytes. PMN from a patient with chronic granulomatous disease were similarly affected. It was thus concluded that the observed defect in phagocytic activity was not due to the reactive oxygen species generated by the PMN during incubation with virus.

Defense mechanisms in the bovine lung

The purpose of this article is to examine factors contributing to defense of the bovine lung from microbial infection. Appropriate physical, cellular, and secretory defense components are assessed. Attention is paid to the thin line separating host-mediated defense from host-mediated injury of the lung.

Chemiluminescence in neutrophils and Lettré cells induced by myxoviruses

Luminol-mediated chemiluminescence in neutrophils is stimulated by Sendai virus and by influenza virus; Lettré cells also exhibit chemiluminescence (less than 10% of that of neutrophils), which is stimulated by Sendai virus and by influenza virus. Virally induced permeability changes are not responsible for chemiluminescence, since (i) extracellular Ca2+ inhibits permeability changes but stimulates chemiluminescence, and (ii) influenza virus, which induces permeability changes at pH 5.3 but not at pH 7.4, induces chemiluminescence at either pH. Other agents [zymosan, N-formyl-L-methionyl-L-leucyl-L-phenylalanine, 4-phorbol 12-myristate 13-acetate (phorbol ester), A23187] likewise induce chemiluminescence in the absence of permeability changes.

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.

Lethal synergism induced in mice by influenza type A virus and type Ia group B streptococci

Intranasal inoculation of CD-1 or BALB/c mice with low doses of influenza A/PR8/34 (HON1) virus followed 48 h later by intranasal inoculation of low doses of type Ia group B streptococci effected a lethal synergism. At a constant input dose of virus, a direct relationship between input dose of bacteria and percent mortality was observed; the converse was also true. An inverse relationship between input dose of group B streptococci, but not input dose of virus, and mean time to death was observed in CD-1 but not in BALB/c mice. The kinetics of influenza A/PR8/34 virus and group B streptococcal replication in singly and dually infected BALB/c mice was determined by assaying samples from the lungs, liver, spleen, and blood for viable group B streptococci and infectious influenza A/PR8/34 virus. No significant difference in virus replication in the lung was observed between singly and dually infected mice. Extrapulmonary dissemination of virus was not observed. Concurrent virus infection effected a 10,000- to 100,000-fold increase in the levels of type Ia group B streptococci in the lung. Potentiation of group B streptococcal infection of the lung was not associated with bacteremia or infection of the liver or spleen, a finding contrary to previous observations of fulminant septicemia after intranasal inoculation of mice with input doses of group B streptococci less than one-tenth of the pulmonary levels observed in the present study.