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Influenza B virus PB1 protein; nucleotide sequence of the genome RNA segment predicts a high degree of structural homology with the corresponding influenza A virus polymerase protein.

Kemdirim S, Palefsky J, Briedis DJ.

The complete nucleotide sequence of a cloned cDNA copy of the genome RNA segment encoding the influenza B/Lee/40 virus PB1 polymerase protein has been determined. The genome RNA segment is 2368 nucleotides in length and is capable of encoding a polymerase (PB1) protein of 752 amino acids with a calculated mol mass of 84,407 Da. As expected, the protein is highly basic with a net charge of +20 at pH 7.0. Sequence comparison between the influenza A and B virus PB1 proteins reveals that they share 61% amino acid homology. An internal hydrophobic domain and 90% of the proline residues found within the influenza A virus PB1 protein are conserved in the influenza B virus molecule. The influenza A and B virus PB1 proteins share the highest homology yet seen between proteins encoded by these disparate viruses. This remarkable conservation of primary structure argues for severe functional constraint on the evolution of this influenza virus polymerase protein.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3754992&dopt=Abstract flu, influenza



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Influenza in the United Kingdom 1982-85.

Chakraverty P, Cunningham P, Shen GZ, Pereira MS.

Influenza surveillance in the UK between the years 1982 and 1985 has demonstrated the regular winter appearance of influenza A virus of both H1N1 and H3N2 subtypes and influenza B. Their antigenic diversity is described and correlated with the national statistics for morbidity and mortality for influenza. One unexpected finding has been that despite the wide circulation of influenza viruses there has been a continuation of winters without significant increases in influenza deaths or morbidity. A previous report of influenza surveillance (Pereira & Chakraverty, 1982) noted an already unusual series of three consecutive winters with this pattern. This report records a further 4 years bringing a total of seven successive winters without evidence of epidemics of severe disease associated with influenza viruses, as indicated by the national UK statistics.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3782786&dopt=Abstract flu, influenza



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Laboratory studies of the 1984 influenza epidemic on the Witwatersrand.

Schoub BD, Johnson S, McAnerney JM, Martin E, dos Santos IL.

A particularly severe outbreak of influenza occurred on the Witwatersrand from May to August 1984, caused sequentially by influenza A (H3N2), B/influenza and influenza A (H1N1) viruses. Although the precise extent of the infection was impossible to determine, valuable anecdotal information was provided by a network of sentinel sampling stations in private practices, clinics and hospitals, representing a cross-section of population groups on the Witwatersrand. This active surveillance programme was invaluable in providing some 85% of all the specimens, the remainder being routine clinical specimens; in addition, isolation was approximately twice as efficient for the actively acquired specimens than for the routine ones. The epidemic affected all individuals approximately equally, regardless of age, race or socio-economic status. Infection with H1N1 virus tended to predominate in the younger age group, 78% of isolates being from subjects under 30 years of age, whereas 71% of H3N2 isolates came from subjects over 30 years of age. The B/influenza isolates tended to be more evenly dispersed. Novel strains of B/influenza and H1N1 viruses were introduced into the country and possibly contributed to the greater than usual severity of the epidemic. An active surveillance programme is essential to monitor the extent of influenza virus activity and to alert virologists to the introduction of new strains, although at present forecasting of future influenza epidemics is not possible with any significant degree of reliability.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3798269&dopt=Abstract flu, influenza



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Recent influenza virus A infections in forensic cases of sudden unexplained death.

Drescher J, Zink P, Verhagen W, Flik J, Milbradt H.

84 forensic necropsy cases with a history of sudden unexpected death and where no acceptable cause of death was found at autopsy (= cases of sudden unexplained death, SUD) were found to have a significantly higher rate of influenza A (H 3 N 2) infection than did matched controls of the general population and a group of forensic necropsy cases with known cause of death (NON-SUD cases). By contrast, the group of SUD cases was found to have no significantly increased infection rate with influenza H 1 N 1 and B virus, parainfluenza viruses, RS virus, adenovirus, and cytomegalovirus. The influenza A associated SUD cases had a significantly higher rate of pathological and histological findings previously described for cases of primary viral pneumonia than did SUD cases without recent influenza A infection and NON-SUD cases. These findings suggest that virological examination of SUD cases could be helpful in order to determine the probable cause of death. A considerable portion of the influenza associated SUD cases occurred during interepidemic influenza periods. Therefore, such cases could be a useful source for monitoring the interepidemic spread of influenza virus.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3800658&dopt=Abstract flu, influenza



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Macrophages are required for influenza virus infection of human lymphocytes.

Mock DJ, Domurat F, Roberts NJ Jr, Walsh EE, Licht MR, Keng P.

Monocyte and lymphocyte surface-expressed viral antigens have been demonstrated after exposure of unseparated human mononuclear leukocytes to influenza virus in vitro. The current studies, using [35S]methionine pulse-labeled purified preparations of virus-exposed macrophages, depleted of lymphocytes, demonstrate that the presence of these viral proteins does represent new synthesis. However, purified lymphocytes, depleted of monocytes-macrophages and exposed to influenza virus, showed no detectable viral protein synthesis. In further experiments, unseparated mononuclear leukocytes were exposed to virus and subsequently separated by countercurrent centrifugal elutriation. Both macrophages and lymphocytes were then shown to synthesize influenza proteins. Cell-free control or influenza virus-infected macrophage-derived supernatant fluids did not facilitate influenza virus infection of the lymphocytes. The data suggest that macrophages are required for influenza virus infection of human lymphocytes, and raise the possibility that macrophage facilitation of an abortive infection of lymphocytes plays a role in the generation of effective immunity to viral antigens.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3805284&dopt=Abstract flu, influenza



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Infectious influenza A and B virus variants with long carboxyl terminal deletions in the NS1 polypeptides.

Norton GP, Tanaka T, Tobita K, Nakada S, Buonagurio DA, Greenspan D, Krystal M, Palese P.

An influenza A virus, A/turkey/Oregon/71, was shown by protein gel analysis to code for an NS1 protein approximately half the size of those of other influenza A viruses. Sequence analysis of the NS gene of this virus revealed a 10 nucleotide deletion resulting in an NS1 protein of only 124 amino acids. This truncated NS1 polypeptide retained its karyophilic pattern as detected by indirect immunofluorescence analysis of virus infected cells. Also, A/turkey/Oregon/71 virus grew to high titer in embryonated chicken eggs comparable to other influenza A viruses. We also identified a laboratory variant of an influenza B virus, clone 201, which codes for a truncated NS1 protein. Sequence analysis revealed a 13 nucleotide deletion resulting in a shortened NS1 protein of only 127 amino acids as compared to other influenza B virus NS1 proteins possessing a length of 281 amino acids. Again as shown for the NS1 proteins of other influenza B viruses the NS1 polypeptide of B virus clone 201 was found to localize in the nucleus of infected cells. It appears that large deletions in the carboxyl terminus of the NS1 proteins of influenza A and B viruses can be tolerated without affecting the functional integrity of the NS1 polypeptide.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3811235&dopt=Abstract flu, influenza



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[Operative assessment of the influenza situation based on a complex accounting of standardized indices of incidence and data on rapid diagnosis]

[Article in Russian]

Khokhlova GG, Zakstel'skaia LIa, Zhdanov VM.

The paper described a method allowing most objective and operative evaluation of the influenza situation in the autumn-winter period, the detection of the onset of influenza epidemic in a given population area, and characterization of the intensity of the epidemic. The development of a more accurate method of operative evaluation of the influenza situation is necessary because influenza is one of widely prevalent virus diseases which still plays a significant role in human pathology and simultaneously takes away from productive labor tremendous numbers of workers. Follow-up of the incidence levels is based on the idea of comparison of the actual data with standardized parameters. These parameters (incidence at the start week, the pace of epidemic increase, the critical seasonal coefficient) are calculated by weekly data of the basic period for a number of years for each town under study on the basis of comparison with the mean minimal level of influenza and ARD incidence (summer normal level) and also the use of mathematical statistics apparatus. To establish epidemiologically unfavourable situation it is necessary that operatively estimated current parameters (analogous with pre-calculated standardized ones) be equal to or exceeding the standardized parameters. The methods of rapid diagnosis are used additionally for identification of the etiology of the starting outbreak or epidemic. The use of the developed methods is exemplified in the paper by practical estimates of the influenza situation in Moscow in the seasons of 1983-1984 and 1984-1985.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3825088&dopt=Abstract flu, influenza



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Intestinal replication of influenza A viruses in two mammalian species. Brief report.

Kawaoka Y, Bordwell E, Webster RG.

The sites of replication of influenza A viruses in ferrets and pigs were studied. The majority of the swine, equine, and avian influenza A viruses tested were recovered from the intestinal tract of ferrets as well as from the respiratory tract; most of the human influenza viruses studied were recovered only from the respiratory tract. In contrast with ferrets, only Hong Kong/1/68 (H 3 N 2) influenza virus was recovered from the intestinal tract of pigs. Despite the large biological variability found in ferrets and in pigs, the results do establish that the majority of influenza viruses have the potential to replicate in the intestinal tissues of some mammals. Additionally, the study suggests that there are differences among the influenza A viruses in tissue tropism in different mammals. Both viral and host genetic factors determine the tissue tropism of influenza viruses in mammals.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3827601&dopt=Abstract flu, influenza



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Antigenic mapping of an avian H1 influenza virus haemagglutinin and interrelationships of H1 viruses from humans, pigs and birds.

Austin FJ, Webster RG.

Monoclonal antibodies to the haemagglutinin (HA) of the avian H1 influenza virus A/duck/Alberta/35/76 were used to construct an operational antigenic map of the HA molecule and to study the interrelationships of H1 viruses from different hosts. Haemagglutination inhibition tests between the monoclonal antibodies and variants selected by them provided evidence of four antigenic regions which overlap to varying degrees. Avian H1 influenza viruses displayed a spectrum of reactivities to the monoclonal antibody panel. Representatives of the epidemic strains of human H1 influenza viruses and early swine influenza viruses showed little or no reactivity with the monoclonal antibodies but swine influenza-like viruses isolated from pigs and humans in the last decade reacted with 11 of 17 antibodies. The antigenic similarity of these viruses to many avian isolates suggests that there has been a transfer of HA genetic information between mammalian and avian H1 influenza viruses.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2423640&dopt=Abstract flu, influenza



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[Immunogenicity and the protective effectiveness of the subunit trivalent influenza vaccine Grippovac]

[Article in Russian]

Chumakov MP, Malyshkina LP, Mart'ianova LI, Marinina VP, Mel'nikova SK.

In the process of the immunological approbation of several experimental batches of the triyalent subunit influenza vaccine Grippovac, the pronounced immunogenicity of the antigens of all strains contained in the vaccine was established; most of the vaccinees were found to retain sufficiently high antibody titers for a year, and the essential total increase of antibody titers was found to occur after a single booster immunization. The serological checking of the diagnosed cases of influenza among immunized and nonimmunized children, carried out in two boarding schools during the influenza epidemic in the winter of 1984-1985 provided the proofs of the high effectiveness of Grippovac in preventing viral influenza, types A and B: the decrease of influenza morbidity among the immunized children reached 79,5-67,2-66,5% and the total morbidity rate in influenza in these two boarding scholls dropped, on the average, 3,0-3,5 times.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2938372&dopt=Abstract flu, influenza



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[Varying nature of the cell receptors for influenza and para-influenza viruses]

[Article in Russian]

Kornilaeva GV, Slepushkin VA, Bukrinskaia AG.

A comparative study of receptors for influenza virus, fowl plague virus, and human parainfluenza type 3 virus was carried out. Natural receptors of guinea pig erythrocytes were destroyed with neuraminidase, and individual gangliosides GM1, GD1a, and GT1b were inserted into their membranes. The labeled virus was adsorbed on the erythrocytes modified in this manner, and the degree of restoration of the receptor activity of erythrocytes lost after neuraminidase treatment was determined. Two gangliosides, GD1a and GT1b, were found to be capable of functioning as specific receptors for influenza virus. Both gangliosides restored completely the virus adsorption on erythrocytes. In contrast, none of the three gangliosides used did not restore parainfluenza virus adsorption. It is concluded that the nature of influenza and parainfluenza virus receptors is different.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3008439&dopt=Abstract flu, influenza