Inhibition of influenza A virus hemagglutinin and induction of interferon by synthetic sialylated glycoconjugates.

Multivalent forms of neoglycoproteins and polyacrylamides containing sialic acid were prepared and shown to be potent inhibitors of influenza A virus (H3N2) hemagglutinin with chick red blood cells. The synthetic sialylated glycoconjugates, although they were neuraminidase substrates, did not suppress viral neuraminidase and did not reduce infectivities in chick embryos. The copolyacrylamide conjugate containing a spacer group of approximately 11 A (1 A = 0.1 nm) between the polymer backbone and the sialic acid residues was the best hemagglutinin inhibitor. Moreover, it exhibited promising interferon-inducing properties.

Kinetics of the binding of immunoglobulins, antibodies and virus haemagglutination inhibitors to kaolin.

Kaolin is widely used in diagnostic virology, mainly to remove serum lipoproteins that may interfere with antibody assaying. The binding kinetics of antibody to kaolin at different pH values and with varying amounts of kaolin indicated a uniform and characteristic binding pattern for IgG with maximum adsorption at pH 5 and no adsorption at pH above 9. To avoid loss of IgG antibody adsorption with kaolin should therefore be performed at pH greater than or equal to 9. The amount adsorbed increased with the amount of kaolin used. The IgM pattern was less uniform with maximum adsorption of total IgM at about 7.0, the amount adsorbed being highly dependent on kaolin concentration. Serum lipoproteins were rapidly and strongly adsorbed independent of pH from 7 to 11 and independent of the lipoprotein content of the serum. The amount of kaolin used was, however, critical.

Selective inhibition of WSN influenza virus haemolysis by pea lectin.

The capacity of lectins to inhibit viral haemolysis of chicken erythrocytes was tested, to evaluate the role of carbohydrate in the fusion reaction. Pretreatment of cells with pea lectin provided a 70% to 85% haemolysis inhibition with WSN influenza virus, but only 10% to 14% with PR8 influenza virus. Pea lectin did not detectably bind to virus, nor did it inhibit virus binding to cells, but it did inhibit WSN influenza virus elution. Additionally, pea lectin was active against Sendai virus and B/Lee influenza virus, but inactive against Newcastle disease virus. Haemolysis by WSN and PR8 influenza viruses was unaffected in cells pretreated with concanavalin A, peanut, wheatgerm or soybean lectins. A possible role of cellular carbohydrate in virus-cell fusion is discussed.

The use of circular dichroism to study conformational changes induced in Sendai virus envelope glycoproteins. A correlation with the viral fusogenic activity.

Fusion of Sendai virus envelopes with erythrocyte membranes or with phosphatidylcholine/cholesterol liposomes requires the presence of the two viral glycoproteins, namely the hemagglutinin/neuraminidase (HN) and the fusion (F) polypeptides. Membrane vesicles bearing only the HN or the F glycoprotein (HN or F vesicles) or a mixture of both do not possess fusogenic activity. These results clearly show that in order to be fusogenic, the two viral envelope glycoproteins must be present within the same membrane, thus indicating their mutual interaction. Circular dichroism studies revealed that the conformation of the viral glycoproteins in reconstituted viral envelopes or in HN-F vesicles (vesicles formed by co-reconstitution of the HN and F glycoproteins) is different from that of the conformation of these glycoproteins in either HN or F vesicles or in a mixture of both. It has been observed that the mean residue ellipticity as measured at 222 nm (theta 222) of the viral glycoproteins in reconstituted Sendai virus envelopes (RSVE) is lower by about 75% than the value observed for these glycoproteins in isolated HN or F vesicles. Treatment of RSVE or of HN-F vesicles with inhibitors of the viral fusogenic activity such as phenylmethylsulfonyl fluoride, proteolytic enzymes, or incubation at 70 degrees C caused a substantial conformational change in the viral glycoproteins. The theta 222 of unfusogenic RSVE or unfusogenic HN-F vesicles is very close to that observed for a mixture of HN and F vesicles. It is proposed here that in order to be fusogenic, the viral envelope glycoproteins must possess a certain conformation which exists only when they are present within the same membrane.

[Hemagglutination by simian adenovirus 7]. / Hémagglutination par l'adénovirus simien 7.

Simian adenovirus 7, either complete virus or its capsid subunits, agglutinates Rat (Sprague-Dowley) red blood cells in the presence of heterotypical antiserum. Haemagglutination takes place at 4 degrees C and room temperature. The antigen could not be eluted and its haemagglutinin properties are heat-stable. The reaction is specific. It is inhibited by homologous antiserum only. This property and its characteristics permit a camparison of this strongly oncogenic adenovirus to the human adenovirus of subgroup III of Rosen.

[Role of intracellular proteinases and glycosidases in the degradation of the 'large glycoprotein' responsible for the neuraminidase and hemagglutinating activity of the Newcastle disease virus]. / Rol' vnutrikletochnykh proteinaz i glikozidaz v degradatsii 'bol'shogo glikoproteida', otvetstvennogo za neiraminidagnuiu i gemaggliutiniruiushchuiu aktivnost' virusa bolezni N'iukasla

It was shown that the decrease in neuraminidase and hemagglutinin activities in Newcastle disease virus (NDV) infected cells, which was revealed in conditions of disturbed protein synthesis, could be significantly diminished by addition of an inhibitor or trypsin-like proteinases tosyl-lysil-chloromethyl keton. The same effect was caused by D-galactonolactone--inhibitor of some glycosidases. These data suggested that the action of intracellular proteinases and glycosidases are the cause of degradation of 'large glycoprotein', responsible for neuraminidase and hemagglutinin activities in NDV-infected cells.

Equine abortion (herpes) virus: strain differences in susceptibility to inactivation by dithiothreitol.

The infectivity of equine abortion (herpes) virus (EAV) was inactivated by treatment with reduced dithiothreitol (DTT). According to their susceptibility to DTT, the EAV strains could be divided into three groups. The vaccine strain RAC-H (419) proved to be more resistant to DTT than all of the other 14 strains tested. The hemagglutinin of EAV was also inactivated by DTT; no strain differences were observed in this respect.

Inactivation of the hemagglutinins of type A influenza viruses by physical and chemical means: an aid to classification.

The effects of temperature and treatment with sodium dodecyl sulfate, Tween 20, dithiothreitol, trypsin, or guanidine on the hemagglutinating capacity of six strains of type A influenza virus (A(0)/PR8/34, A(1)/CAME/46, A(2)/J305/57, A(2)/Bethesda/63, A(2)/HK/Aichi/68, and A(2)/HK/80/68), one strain of swine virus (A/Swine/76/?), and one equine strain (A/Equi-2/63) were determined. The two Hong Kong strains could be readily distinguished from the earlier A(2) strains by the resistance of their hemagglutinins to trypsin treatment and their inability to recover hemagglutinating capacity after removal of dithiothreitol from treated virus preparations. In these respects, the equine strain most closely resembled the Hong Kong variants. The pattern of hemagglutination inactivation also set the swine, PR8, and CAME strains apart from each other as well as from the other five strains. The results suggest that separation of type A viruses into groups by the pattern of inactivation of their hemagglutinins may be a valuable adjunct to standard serology for a more definite classification of these viruses.

Enzymes produced by a Pseudomonas species which inactivate inhibitors of certain viral hemagglutinins. I. Identification and purification of a proteinase and phospholipase C.

Filtrates from cultures of a psychrophilic Pseudomonas species, which inactivate serum inhibitors of certain viral hemagglutinins, were shown to contain both lecithinase (phospholipase C) and a proteolytic enzyme with elastase activity. The bacterium was cultivated under conditions favoring production of the respective enzymes, and the enzymes were purified by ammonium sulfate precipitation followed by column chromatography or by gel filtration. The elastase was obtained in crystalline form and was recrystallized. It has properties similar to those of a number of other bacterial elastases but is more heat-labile than most. Although a high degree of purification was achieved for the lecithinase, as evidenced by an increase in specific activity, it was not obtained in crystalline form. Partially purified preparations of the lecithinase had extremely high activity compared to that of commercial preparations of phospholipase C from Clostridium welchii.

Destruction of L cells by Mengo virus: use of interferon to study the mechanism.

Interferon, when added to L cells, inhibited the synthesis of infectious Mengo viral ribonucleic acid, hemagglutinins, and infectious virus by 85 to 95%. Serum-blocking antigens were also reduced by the action of interferon, but threefold excess amounts of these antigens accumulated in interferon-treated cultures above the amounts expected for the quantity of infectious virus that was produced in these cultures. Radioautographic analysis showed that 28 to 36% of the cells of an interferon-treated population synthesized viral ribonucleic acid and 36 to 47% produced viral antigens as determined by an immunofluorescence technique. Despite the reductions in synthesis of viral components, all cells in an interferon-treated culture underwent cytopathic effects at the same time as cells in infected cultures which had not been treated with interferon. The results are compatible with the hypothesis that the cell destruction which results from the infection of L cells with Mengo virus is due to a protein which is coded for by the virus but is not a component of the mature virion.