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The design of a three-stage filtration system to remove contaminating hydrogen sulphide from a supply of carbon dioxide for long-term tree growth experiments is described. The system is designed to treat a gas mix of 75% CO2 in air at a flow rate of 30 m3 h-1 originating from biogas at a waste water treatment plant. The concentration of H2S in the raw gas is 2500 mu l l-1 and this is reduced to less than 1 mu l l-1 by the filtration process. The three filtration stages consist of a recirculating liquid system using a self-regenerating solution of iron chelate, a dry iron oxide box, and drums containing activated carbon. Regular, low intensity maintenance is necessary to remove the precipitated sulphur compounds from the liquid system. The iron oxide and activated carbon need to be changed at three monthly and monthly intervals, respectively. The spent iron oxide is discarded, while the activated carbon is able to be regenerated using caustic soda solution. After filtering, the gas is diluted with ambient air in large open-top chambers surrounding the trees. The air in the chambers has a concentration of CO2 of approximately 650 mu l l-1 with the concentration of H2S being less than 0.001 mu ll-1, which is acceptable for tree growth studies. The system is reliable and has operated continuously for 3 years. This provides a low cost option for the long-term supply of CO2 to experimental field sites. [ABSTRACT FROM AUTHOR]

Human and animal (avian and equine) influenza A virus isolates of the H3 serotype exhibit marked differences in their ability to bind specific sialyloligosaccharide sequences that serve as cell surface receptor determinants (G. Rogers and J. Paulson, 1983, Virology 127, 361-373). Whereas human isolates of this subtype strongly agglutinate enzymatically modified human erythrocytes containing the terminal SA alpha 2,6Gal sequence, avian and equine isolates preferentially agglutinate erythrocytes bearing the SA alpha 2, 3Gal sequence. As shown in this report, a glycoprotein found in horse serum, alpha 2-macroglobulin, is a potent inhibitor of viral adsorption to the cell surface for human H3 isolates. In contrast, avian and equine isolates are poorly inhibited suggesting a correlation between receptor specificity and inhibitor sensitivity. Growth of a human H3 isolate (A/Memphis/102/72) on MDCK cells in the presence of horse serum resulted in an overall shift in the virus receptor specificity from preferential binding of the SA alpha 2,6Gal linkage to preferential binding of the SA alpha 2,3Gal linkage characteristic of avian and equine isolates. Clonally isolated variants of A/Memphis/102/72 grown in the presence or absence of horse serum exhibited binding properties that account for those observed in the field isolates. Clones which preferentially bound the SA alpha 2,6Gal linkage, like the parent human virus, were very sensitive to inhibition of hemagglutination by horse serum and equine alpha 2-macroglobulin. In contrast, receptor variants which preferentially bound the SA alpha 2,3Gal linkage, like the avian and equine isolate, were insensitive to such inhibitors. None of the variants was very sensitive to inhibition of hemagglutination by human alpha 2-macroglobulin. These results suggest that the presence, in vivo, of a glycoprotein inhibitor such as equine alpha 2-macroglobulin could suppress infection of influenza viruses bearing an H3 hemagglutinin with a SA alpha 2,6Gal specific, inhibitor sensitive phenotype, allowing growth to predominance of a virus which is SA alpha 2,3Gal specific and inhibitor insensitive as found in avian and equine isolates.

This report examines the ability of three sialic acids (SA), N-acetylneuraminic acid (NeuAc), N-glycollylneuraminic acid (NeuGc), and 9-O-acetyl-N-acetylneuraminic acid (9-O-Ac-NeuAc), to serve as receptor determinants for 18 human and animal influenza type A viruses. Viruses were compared by agglutination of receptor-modified erythrocytes containing either the Sa alpha 2,6Gal or the SA alpha 2,3Gal linkages with each of the three sialic acids. Individual isolates differed markedly in their ability to agglutinate cells containing NeuAc, NeuGc, and 9-O-Ac-NeuAc. The results suggest that recognition of the various sialic acids is an important factor in analysis of the receptor specificity of influenza virus hemagglutinins.

It has been previously reported that several human H1 influenza viruses isolated prior to 1956, in contrast to human H3 isolates which are quite specific for SA alpha 2,6Gal sequences, apparently recognize both SA alpha 2,3Gal and SA alpha 2,6Gal sequences (Rogers, G.N., and Paulson, J.C., Virology 127, 361-373, 1983). In this report human H1 isolates representative of two epidemic periods, from 1934 to 1957 and from 1977 to 1986, and H1 influenza isolated from pigs, ducks, and turkeys were compared for their ability to utilize sialyloligosaccharide structures containing terminal SA alpha 2,3Gal or SA alpha 2,6Gal sequences as receptor determinants. Five of the eight human isolates from the first epidemic period recognize both SA alpha 2,3Gal and SA alpha 2,6Gal linkages, in agreement with our previous results. Of the remaining three strains, all isolated towards the end of the first epidemic, two appear to prefer SA alpha 2,6Gal sequences while the third preferentially binds SA alpha 2,3Gal sequences. In contrast to the early isolates, 11 of 13 human strains isolated during the second epidemic period preferentially bind SA alpha 2,6Gal containing oligosaccharides. On the basis of changes in receptor binding associated with continued passage in the laboratory for some of these later strains, it seems likely that human H1 isolates preferentially bind SA alpha 2,6Gal sequences in nature, and that acquisition of SA alpha 2,3Gal-binding is associated with laboratory passage. Influenza H1 viruses isolated from pigs were predominantly SA alpha 2,6Gal-specific while those isolated from ducks were primarily SA alpha 2,3Gal-specific. Thus, as has been previously reported for H3 influenza isolates, receptor specificity for influenza H1 viruses appears to be influenced by the species from which they were isolated, human isolates binding preferentially to SA alpha 2,6Gal-containing oligosaccharides while those isolated from ducks prefer SA alpha 2,3Gal-containing oligosaccharides. However, unlike the SA alpha 2,6Gal-specific H3 isolates, binding to cell surface receptors by the H1 influenza viruses is not sensitive to inhibition by horse serum glycoproteins, regardless of their receptor specificity. These results suggest that, while the H1 and H3 hemagglutinins appear to be subject to similar host-derived selective pressures, there appear to be certain fundamental differences in the detailed molecular interaction of the two hemagglutinins with their sialyloligosaccharide receptor determinants.

Monoclonal antibodies were used to compare the antigenicities of the haemagglutinins of two receptor binding mutants of X-31 (H3N2) influenza virus. The mutants which differed from each other in recognizing sialic acid in either alpha 2-6 linkage or alpha 2-3 linkage to galactose also differed exclusively at residue 226 of the HA1 polypeptides of their haemagglutinins (G. N. Rogers, J. C. Paulson, R. S. Daniels, J. J. Skehel, I. A. Wilson, and D. C. Wiley, Nature (London) 304, 76-78, 1983). The results obtained indicate that whereas the majority of antihaemagglutinin monoclonal antibodies react with both mutants equally well, a number which specifically recognize residues 193, 199, 219, and 229 of HA1 of the alpha 2-6 linkage-binding mutant fail to recognize the alpha 2-3 linkage-binding haemagglutinins. The results are discussed with reference to the three-dimensional structure of the haemagglutinin and in relation to differences in antigenicity observed in the haemagglutinins of viruses grown in cells of different types.

Among the pathological effects in man following infection with Mycoplasma pneumoniae is a transient autoimmune disorder characterized by the presence of high-titre erythrocyte autoantibodies (cold agglutinins). These autoantibodies are usually directed against the carbohydrate antigen termed I (ref. 3) which consists of a branched oligosaccharide. The mechanism by which the anti-I antibodies are elicited is unknown. However, sialic acid-containing receptors have been implicated in the adherence of M. pneumoniae to erythrocytes and other cell types, and both I and the related antigen i occur on erythrocytes in sialylated form: i is the predominant antigen on fetal erythrocytes and I is predominant in adults. Anti-I antibodies might arise in M. pneumoniae infection in response to a modification of the 'self' antigen-I as a result of its interaction with this agent. Here we report our study of the specificity of the interaction of M. pneumoniae with human erythrocytes. We found that this interaction is mediated by long chain oligosaccharides of sialic acid joined by alpha 2-3 linkage to the terminal galactose residues of poly-N-acetyllactosamine sequences of Ii antigen type.

The binding of influenza virus to erythrocytes and host cells is mediated by the interaction of the viral hemagglutinin (H) with cell surface receptors containing sialic acid (SA). The specificity of this interaction for 19 human and animal influenza isolates was examined using human erythrocytes enzymatically modified to contain cell surface sialyloligosaccharides with the sequence SA alpha 2,6Gal beta 1,4GlcNAc; SA alpha 2,3Gal beta 1,4(3)GlcNAc; SA alpha 2,3Gal beta 1,3GalNAc; or SA alpha 2,6GalNAc. Although none of the viruses agglutinated cells containing the SA alpha 2,6GalNAc linkage, differential agglutination of cells containing the other three sequences revealed at least three distinct receptor binding types. Several virus isolates exhibited marked receptor specificity, binding only to cells containing the SA alpha 2,6Gal or the SA alpha 2,3Gal linkage, while others bound equally well to cells containing either linkage. Moreover, some viruses could distinguish between two oligosaccharide receptor determinants containing the terminal SA alpha 2,3Gal linkage when present in the SA alpha 2,3Gal beta 1,4(3)GlcNAc sequence or the SA alpha 2,3Gal beta 1,3GalNAc sequence binding cells containing only the former. The observed receptor specificities were not significantly influenced by the viral neuraminidases as shown by the use of the potent neuraminidase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid. Receptor specificity appeared, to some extent, to be dependent on the species from which the virus was isolated. In particular, human isolates of the H3 serotype all agglutinated cells containing the SA alpha 2,6Gal linkage, but not cells bearing the SA alpha 2,3Gal beta 1,3GalNAc sequence. In contrast, antigenically similar (H3) isolates from avian and equine species preferentially bound erythrocytes containing the SA alpha 2,3Gal linkage. This is of particular interest in view of the identification of the avian virus H3 hemagglutinin as the progenitor of the H3 hemagglutinin present on the current human Hong Kong viruses.