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Induction of antibody responses to influenza virus in human lymphocyte cultures. I. Role of interleukin 2.

Tan PL, Booth RJ, Prestidge RL, Watson JD, Dower SK, Gillis S.

The in vitro T cell-dependent antibody response of human lymphocytes to influenza virus X31 was used to study the role of T cell-derived lymphokines in antigen-specific responses. Supernatant from cultures of phytohaemagglutinin-stimulated, pooled human tonsil cells (PHA-MLR) was capable of replacing T cells and inducing T-depleted tonsil cells to secrete influenza-specific antibody. The T cell-replacing activity of PHA-MLR supernatant co-purified with interleukin 2 (IL 2) on Ultrogel AcA54 gel filtration and reversed phase-high performance liquid chromatography. PHA-MLR supernatant and IL 2 also enhanced B cell proliferation induced by anti-mu or Staphylococcal aureus strain Cowan I (SAC). A murine monoclonal antibody directed against the human IL 2 receptor (Mab 2A3) was used to completely block the enhancement of influenza-specific antibody production mediated by PHA-MLR supernatant, purified IL 2, and recombinant human IL 2. Mab 2A3 did not affect the T-independent B cell proliferation induced by anti-mu or SAC, but abrogated the enhancing effect of the PHA-MLR supernatant and IL 2 in this culture system. Immunofluorescence studies failed to demonstrate binding of Mab 2A3 to B cells activated by the X31 influenza virus and IL 2, or by SAC. By using Mab 2A3 to mask out IL 2 effects in the influenza-specific culture system, no other B cell differentiating activities were revealed in supernatants from lymphocytic cultures stimulated with a variety of mitogens. Thus, our results indicate that the production of influenza-specific antibodies by T-depleted human lymphocyte cultures is absolutely dependent on the presence of both antigen and IL 2.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3926896&dopt=Abstract flu, influenza



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Role of serum in stimulation of polymorphonuclear leukocyte, luminol-dependent chemiluminescence by influenza A.

Shult PA, Dick EC, Joiner KA, Busse WW.

Granulocyte membrane perturbation activates oxidative metabolism with the release of highly reactive species (O2-, H2O2, OH., and 'O2) and emission of light (chemiluminescence (CL)). Using the CL response as a measure of oxidative metabolism, we assayed the effects of influenza A on the granulocyte respiratory burst. Human polymorphonuclear leukocytes (PMNs) were isolated by Ficoll-Hypaque cushioning and dextran sedimentation. The isolated PMNs were incubated with egg-grown influenza A (H3N2) virus, or a medium control, in the presence of 1 microM luminol and fresh autologous serum (10%). No light emission occurred during the incubation of PMNs with the medium control. Influenza A (33 to 50% egg-infective-doses (EID50):1 PMN) stimulated PMN light emission with a maximal response (48,386 +/- 10,764 cpm/10(6) PMN) occurring at 37 degrees CL was dependent on the virus dose with a diminished response (6,041 +/- 3,200 cpm/10(6) PMN) occurring at a lower infectivity of 10 EID50:1 PMN. Chemiluminescence responses were similar with infective and with noninfective virus particles (heat inactivated, 56 degrees C X 2 h). Fresh serum was necessary for the influenza virus to cause a CL response. A significant correlation (p less than 0.01) existed between the level of light emission and the hemagglutination-inhibiting (HI) antibody titer to influenza A of the autologous serum. Virus in the absence of detectable antibody did not stimulate CL. The virus-associated CL was completely inhibited if autologous serum was heated (56 degrees C X 30 min) or if the PMNs were pretreated with cytochalasin B (5 mcg/ml X 5 min). These findings suggest that influenza A-associated PMN CL requires antibody, complement, and phagocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3970456&dopt=Abstract flu, influenza



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Characterization of virulent and avirulent A/chicken/Pennsylvania/83 influenza A viruses: potential role of defective interfering RNAs in nature.

Bean WJ, Kawaoka Y, Wood JM, Pearson JE, Webster RG.

In April 1983, an influenza virus of low virulence appeared in chickens in Pennsylvania. Subsequently, in October 1983, the virus became virulent and caused high mortality in poultry. The causative agent has been identified as an influenza virus of the H5N2 serotype. The hemagglutinin is antigenically closely related to tern/South Africa/61 (H5N3) and the neuraminidase is similar to that from human H2N2 strains (e.g., A/Japan/305/57) and from some avian influenza virus strains (e.g., A/turkey/Mass/66 [H6N2]). Comparison of the genome RNAs of chicken/Penn with other influenza virus isolates by RNA-RNA hybridization indicated that all of the genes of this virus were closely related to those of various other influenza virus isolates from wild birds. Chickens infected with the virulent strain shed high concentrations of virus in their feces (10(7) 50% egg infective dose per g), and the virus was isolated from the albumin and yolk of eggs layed just before death. Virus was also isolated from house flies in chicken houses. Serological and virological studies showed that humans are not susceptible to infection with the virus, but can serve as short-term mechanical carriers. Analysis of the RNA of the viruses isolated in April and October by gel migration and RNA-RNA hybridization suggested that these strains were very closely related. Oligonucleotide mapping of the individual genes of virulent and avirulent strains showed a limited number of changes in the genome RNAs, but no consistent differences between the virulent and avirulent strains that could be correlated with pathogenicity were found. Polyacrylamide gel analysis of the early (avirulent) isolates demonstrated the presence of low-molecular-weight RNA bands which is indicative of defective-interfering particles. These RNAs were not present in the virulent isolates. Experimental infection of chickens with mixtures of the avirulent and virulent strains demonstrated that the avirulent virus interferes with the pathogenicity of the virulent virus. The results suggest that the original avirulent virus was probably derived from influenza viruses from wild birds and that the virulent strain was derived from the avirulent strain by selective adaptation rather than by recombination or the introduction of a new virus into the population. This adaptation may have involved the loss of defective RNAs, as well as mutations, and thus provides a possible model for a role of defective-interfering particles in nature.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3973976&dopt=Abstract flu, influenza



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The Ebola virus VP35 protein functions as a type I IFN antagonist.

Basler CF, Wang X, Muhlberger E, Volchkov V, Paragas J, Klenk HD, Garcia-Sastre A, Palese P.

Department of Microbiology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.

An assay has been developed that allows the identification of molecules that function as type I IFN antagonists. Using this assay, we have identified an Ebola virus-encoded inhibitor of the type I IFN response, the Ebola virus VP35 protein. The assay relies on the properties of an influenza virus mutant, influenza delNS1 virus, which lacks the NS1 ORF and, therefore, does not produce the NS1 protein. When cells are infected with influenza delNS1 virus, large amounts of type I IFN are produced. As a consequence, influenza delNS1 virus replicates poorly. However, high-efficiency transient transfection of a plasmid encoding a protein that interferes with type I IFN-induced antiviral functions, such as the influenza A virus NS1 protein or the herpes simplex virus protein ICP34.5, rescues growth of influenza delNS1 virus. When plasmids expressing individual Ebola virus proteins were transfected into Madin Darby canine kidney cells, the Ebola virus VP35 protein enhanced influenza delNS1 virus growth more than 100-fold. VP35 subsequently was shown to block double-stranded RNA- and virus-mediated induction of an IFN-stimulated response element reporter gene and to block double-stranded RNA- and virus-mediated induction of the IFN-beta promoter. The Ebola virus VP35 therefore is likely to inhibit induction of type I IFN in Ebola virus-infected cells and may be an important determinant of Ebola virus virulence in vivo.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11027311&dopt=Abstract flu, influenza



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Epizootiology of avian influenza: effect of season on incidence in sentinel ducks and domestic turkeys in Minnesota.

Halvorson DA, Kelleher CJ, Senne DA.

Sentinel ducks and domestic turkey flocks were monitored for influenza infection during a 4-year period. The onset of infection among ducks was similar each year, occurring in late July or early August. Influenza in turkeys was also shown to be seasonal, but the usual onset was 6 to 8 weeks after the detection of influenza in sentinel ducks. Possible explanations for the delayed infection in turkeys are (i) increased waterfowl activity associated with fledging and congregating in late summer and early fall; (ii) vectors transmitting virus from the waterfowl habitat to poultry farms; (iii) cooler environmental temperature, allowing prolonged virus viability; (iv) cooler surface water temperature, allowing prolonged virus viability; (v) groundwater contamination from contaminated surface water; and (vi) virus adaptation in domestic turkeys before infection is detected. We conclude that ducks are not only a natural reservoir of influenza but also have a seasonal infection that appears to be related to seasonal influenza outbreaks in domestic turkeys in Minnesota. However, only some influenza A virus isolates circulating among waterfowl at any given time appear capable of causing detectable infection in turkeys. It is speculated that the seasonal infection in migratory waterfowl may also be related to seasonal influenza infections in other species including humans.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4004223&dopt=Abstract flu, influenza



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Concurrent outbreaks of influenza A and influenza B.

Spelman DW, McHardy CJ.

During the winter of 1982 concurrent outbreaks of influenza A and influenza B occurred. The epidemiology and clinical features of 151 cases referred during this time are described, and patients are discussed according to age and presenting clinical syndrome: croup was the commonest presentation in young children, a typical influenza syndrome predominated in young adults, while older patients were more likely to have lower respiratory tract infection. There was no significant difference between the clinical features of influenza A and influenza B. Unusual clinical features include rash, exudative tonsillitis and the need for myringotomy during the course of influenza.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4008920&dopt=Abstract flu, influenza



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Acute respiratory disease hospitalizations as a measure of impact of epidemic influenza.

Perrotta DM, Decker M, Glezen WP.

Current measures of the health impact of epidemic influenza focus on analyses of death certificate data which may underestimate the true health effect. Previous investigations of influenza-related morbidity either have lacked virologic confirmation of influenza virus activity in the community or were not population-based. Community virologic surveillance in Houston, Texas has demonstrated that influenza viruses have produced epidemics each year since 1974. This study examined the relationship of hospitalizations with acute respiratory disease to the occurrence of influenza epidemics. Discharge records of 13,297 acute respiratory disease hospitalizations that occurred between July 1978 and June 1981 were obtained from 11 hospitals with 48.4% of hospital beds available in Harris County (metropolitan Houston). The correlation of adult acute respiratory disease hospitalizations with established indices of community acute respiratory disease morbidity was strong (r = 0.74) and indicated that the peak of adult acute respiratory disease hospitalizations followed the peak of influenza virus isolations by one week. Only 23.2% of persons hospitalized were 65 years of age or older, compared to 60-70% of persons who die during influenza epidemics. Although the highest rates of acute respiratory disease hospitalizations occurred among infants and persons aged 65 years or older, the rates for adults 45-64 years and preschool children aged 1-4 years were greater than 1 per 1,000 persons. Surveillance of acute respiratory disease hospitalizations can improve the measurement of serious morbidity associated with epidemic influenza, and can better define the characteristics of persons at risk for development of illness requiring hospitalization.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4025296&dopt=Abstract flu, influenza



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Influenza vaccination and the risk of primary cardiac arrest.

Siscovick DS, Raghunathan TE, Lin D, Weinmann S, Arbogast P, Lemaitre RN, Psaty BM, Alexander R, Cobb LA.

Department of Medicine, University of Washington, Seattle, USA. dsisk u.washington.edu

Influenza epidemics are associated with an excess of mortality not only from respiratory diseases but also from other causes, and cardiovascular mortality increases abruptly during influenza epidemics, with little evidence of a lag period. In a population-based case-control study, the authors examined whether influenza vaccination was associated with a reduced risk of out-of-hospital primary cardiac arrest (PCA), a major contributor to cardiovascular mortality in the community. Cases of PCA (n = 342) without prior heart disease or life-threatening comorbidity that occurred in King County, Washington, were identified from paramedic incident reports from October 1988 to July 1994. Demographically similar controls (n = 549) were identified from the community by using random digit dialing. Spouses of subjects were interviewed to assess treatment with influenza vaccine during the previous year and other risk factors. After adjustment for demographic, clinical, and behavioral risk factors, influenza vaccination was associated with a reduced risk of PCA (odds ratio = 0.51, 95 percent confidence interval: 0.33, 0.79). The authors suggest that while the association of influenza vaccination with a reduced risk of PCA is consistent with cohort studies of influenza vaccination and total mortality, further studies are needed to determine whether the observed association reflects protection or selection.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11032163&dopt=Abstract flu, influenza



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Policies and outcomes for control of influenza among the elderly in the USA.

Kendal AP, Patriarca PA, Arden NH.

For about 20 years official recommendations have been made to provide influenza vaccine to elderly persons in the USA because they are high risk of complications if infected during epidemics. Residents of homes for the aged (Nursing Homes) are of particular concern and we have studied this subgroup in greater detail than before. A prospectively organized surveillance programme of about 7000 residents of more than 65 homes in several states indicated that vaccination rates varied from about 9 to 98%, with the average about 60%. Biases in vaccinating residents according to age and medical condition were not detected. Vaccine use was greatest when the policy of the homes was to administer vaccine without requesting consent of relatives. In separate studies of influenza A(H3N2) outbreaks in homes for the elderly during 1982/83, influenza vaccine was found to reduce influenza-associated mortality by about 75% although febrile respiratory illness rates were reduced less than 50%. The frequency of outbreaks was lowest in homes having fewest residents, and highest vaccination rates. Professional Educational Programmes are no being developed to assist homes for the elderly to improve the organization of their influenza vaccination activities in an attempt to further reduce influenza mortality.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4060857&dopt=Abstract flu, influenza



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Protection and recovery in influenza virus-infected mice immunosuppressed with anti-IgM.

Kris RM, Asofsky R, Evans CB, Small PA Jr.

BALB/c mice, immunosuppressed from birth with goat anti-mouse IgM, were able to recover from influenza virus infection in the absence of detectable serum and nasal antibody. Recovery was delayed a few days when compared with control animals. Antibody-deficient mice, that had recovered from an initial influenza virus infection, i.e., convalescent mice, were subsequently rechallenged with homologous influenza virus in order to study the importance of nasal and serum antibody in prevention of infection. Convalescent mice were susceptible to reinfection when nasal and serum antibody were not detectable. The mice were resistant to reinfection when serum and/or nasal antibody was detectable by radioimmunoassay. Normal mice that were passively immunized with high titer mouse anti-influenza virus serum were susceptible to challenge with homologous influenza virus. The serum antibody levels in these mice were higher than most of those found in the immune convalescent mice suppressed with anti-IgM, thereby suggesting that the serum antibody, found in convalescent suppressed mice, is not protective. We conclude that 1) mice can recover from influenza virus infection in the absence of detectable levels of nasal and serum antibody, thus indirectly confirming the role of cell-mediated immunity in recovery; 2) serum IgM, IgG2A, IgG2B, IgG3, and probably IgG1 antibody levels are not responsible for protection against influenza virus infection of the upper respiratory tract; and 3) nasal IgA antibody correlates best with protection against reinfection of the upper respiratory tract, but some other locally protective agent cannot be excluded.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2981265&dopt=Abstract flu, influenza



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Entry of influenza viruses into cells is inhibited by a highly specific protein kinase C inhibitor.

Root CN, Wills EG, McNair LL, Whittaker GR.

Department of Microbiology & Immunology, C5141 Veterinary Medical Center, Cornell University, Ithaca, NY 14853, USA.

Following binding to cell surface sialic acid, entry of influenza viruses into cells is mediated by endocytosis. Productive entry of influenza virus requires the low-pH environment of the late endosome for fusion and release of the virus into the cytoplasm and transport of the virus genome into the nucleus. We investigated novel mechanisms to inhibit influenza virus infection using highly specific inhibitors of protein kinase C. We found that one inhibitor, bisindolylmaleimide I, prevented replication of influenza A virus in a dose-dependent manner when added at the time of infection, but had little specific effect when added 2 h after infection had commenced. Virus yields dropped by more than 3 log units in the presence of micromolar levels of bisindolylmaleimide I. Influenza B virus replication was also inhibited by bisindolylmaleimide at micromolar concentrations. We carried out experiments to determine the point in infection that was blocked by bisindolylmaleimide I, and determined that entry of viral ribonucleoproteins (vRNPs) into the nucleus was prevented. Upon drug washout vRNP nuclear entry resumed, showing that bisindolylmaleimide I is reversible. Bisindolylmaleimide I did not affect virus binding and was apparently not acting as a weak base, because its effects were independent of the pH of the external growth medium. These experiments show that bisindolylmaleimide I blocks replication of different types of influenza virus in a dose-dependent and reversible manner, and that virus entry into the cell is inhibited.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11038382&dopt=Abstract flu, influenza