Inactivation of Reovirus Type 2 by a Combination of Chloroform and Moderate Temperature

The infectivity and hemagglutinins of reovirus type 2 were destroyed at 37 C in the presence of chloroform, whereas no effect of chloroform was noted at 0 C.     

Hemagglutinins in brown seaweeds

Twenty-eight brown seaweeds contain agglutinins that show activity against animal and human erythrocytes. Three brown seaweeds are described whose hemagglutinic activity has not been previously reported: Ectocarpus confervoides, Giffordia granulosa and Cutleria multifida. Hemagglutinic activity against different erythrocytes is as follows: rabbit, 100%; sheep, 71%; chicken, 64%; guinea-pig, 39%; human, 38%; horse, 25% and calf, 21%. The highest agglutinic activity was found with rabbit erythrocytes, with maximum titres of: Fucus serratus (2¹⁸), Laminaria saccharina (2¹⁷) and Himanthalia elongata (2¹⁷). The species Giffordia granulosa showed certain specificity against human erythrocytes. In general, the hemagglutinic activity of these brown seaweeds seems to be of a polyphenolic nature. Agglutinic activity of some of these brown seaweeds can be used as a taxonomic index.     

Hemagglutinins of some Aspergilli

Hemagglutinins for human red blood cells have been found in hot-water soluble mycelial extracts of a strain of Aspergillus flavus and two mutant strains of A. parasiticus. The agglutinin from one strain of A. parasiticus was specific for blood group A cells while the other two agglutinins were non-specific. With the A. flavus strain, the greatest hemagglutination activity (HA) was found at 10 days for the mycelial extract, and at 12 days for culture fluid preparations. More agglutinin was produced by fungi grown on sucrose than on d-glucose as carbon source. Solubilities in ammonium sulfate solutions and protein and carbohydrate analyses show that the agglutinins from the mycelial extract and culture fluid preparation are different. The mycelial agglutinin was inhibited by a number of different sugars, many of which possess common stereochemical features.     

Hemagglutinins extracted from locks of unopened cotton bolls

Hemagglutinins, which may mediate plant-fungal interactions, were detected in water soluble extracts from locks of unopened cotton bolls. Hemagglutinating activity was nondialyzable, and thus the agglutinating components possess molecular weights greater than 6 000 daltons. Five of 23 tested sugars inhibited agglutination. The inhibitory sugars did not possess common stereochemical features and included mono-, di-, and trisaccharides.     

Defective Virions of Reovirus

When purified preparations of stock reovirus, type 3, were digested with chymotrypsin, the virions were converted into two different types of particle. These new particles could be separated from each other by isopycnic centrifugation in cesium chloride gradients. One particle banded at a buoyant density of 1.43 g/cm(3), the other at a density of 1.415 g/cm(3). The former particle is termed the heavy (H) particle, the latter is the light (L) particle. The ratio of H/L particles varied between 0.5 and 0.25 in various purified preparations of virus. In electron micrographs, both H and L particles had the appearance and dimensions of viral cores. H particles were infectious for L cells. When plaques formed by stock virus, or by H particles, were picked and propagated in L cells, the majority of the clones gave rise only to H particles on chymotrypsin digestion. On continued serial passage of the clones, virions containing L particles again appeared in the progeny. The simplest explanation of these results was that stock virus was comprised of two populations of virions. One type of virion which contained H particles was infectious, whereas the other, which contained L particles, was not itself infectious and could replicate only in cells coinfected with an H particle virion. Added weight was given to this hypothesis by two observations. First, a small but definite separation of H and L virions could be achieved by isopycnic centrifugation in a gradient of cesium chloride. Second, L particles and virions containing L particles were both shown to lack the largest of the ten segments of double-stranded ribonucleic acid genome. Thus, L particle virions have defective genomes.     

Hemagglutinins and fimbriae of Providencia spp.

A series of 25 strains of Providencia spp. produced at least five different patterns of hemagglutination as judged by results from hemagglutination tests in the presence and absence of D-mannose and at least six distinct types of fimbriae as seen from observations with the electron microscope.     

Hemolysis by Liposomes Containing Influenza Virus Hemagglutinins

Liposomes containing influenza virus hemagglutinin were reassembled from envelopes solubilized with Nonidet P-40 and were shown to induce hemolysis and cell fusion at low pH.     

Fluorescent Trimeric Hemagglutinins Reveal Multivalent Receptor Binding Properties

Influenza A virus carries hundreds of trimeric hemagglutinin (HA) proteins on its viral envelope that interact with various sialylated glycans on a host cell. This interaction represents a multivalent binding event that is present in all the current receptor binding assays, including those employing viruses or precomplexed HA trimers. To study the nature of such multivalent binding events, we fused a superfolder green fluorescent protein (sfGFP) to the C-terminus of trimeric HA to allow for direct visualization of HA–receptor interactions without the need for additional fluorescent antibodies. The multivalent binding of the HA–sfGFP proteins was studied using glycan arrays and tissue staining. The HA–sfGFP with human-type receptor specificity was able to bind to a glycan array as the free trimer. In contrast, the HA–sfGFP with avian-type receptor specificity required multimerization by antibodies before binding to glycans on the glycan array could be observed. Interestingly, multimerization was not required for binding to tissues. The array data may be explained by the possible bivalent binding mode of a single human-specific HA trimer to complex branched N-glycans, which is not possible for the avian-specific HA due to geometrical constrains of the binding sites. The fact that this specificity pattern changes upon interaction with a cell surface probably represents the enhanced amount of glycan orientations and variable densities versus those on the glycan array.