The production of a persistent alteration in influenza virus by lanthanum or ultraviolet irradiation

STUDIES OF THE HEMOLYSIS OF RED BLOOD CELLS BY MUMPS VIRUS : II. THE RELATIONSHIPS OF HEMAGGLUTINATION, VIRUS ELUTION, AND HEMOLYSIS

The relationship between hemagglutination and hemolysis by the mumps virus has been studied under conditions which affect (a) the receptors of chicken red cells and (b) the adsorption and subsequent elution of the virus from these cells. The results show that the hemolytic action of the virus appears to involve some of the same receptor areas of erythrocytes that are implicated in hemagglutination. Materials such as allantoic fluid, egg white, and red cell extract, which inhibit the agglutination of chicken red cells by mumps virus, also interfere with its hemolytic activity. Of these inhibitors, egg white and red cell extract, which are readily destroyed by the virus during incubation at 37°C., exert a greater antagonistic effect on hemagglutination than on hemolysis. Heated mumps virus or unheated influenza virus interferes with the hemolysis of red cells by untreated mumps virus. Though hemolysis takes place during elution of the virus after its adsorption on the red cell, the processes are apparently distinct. The hemolytic activity is easily affected by certain conditions of pH and temperature which have no effect on the ability of mumps virus to adsorb on and elute from red cells.

The associative reactions of pneumonia virus of mice and influenza viruses; the effects of pH and electrolytes upon virus-host cell combinations

Combination between PVM and erythrocytes as well as between the influenza viruses and erythrocytes is inhibited at low electrolyte concentrations. Combination between PVM and lung particles as well as between the virus and erythrocytes can be dissociated in solutions of low electrolyte concentration. The rate of elution of influenza virus is decreased under similar conditions. PVM can combine with and be dissociated from erythrocytes repeatedly without affecting the combining capacity of the ceils and does not possess an enzyme-like activity similar to that of the influenza viruses. Because dissociation depends on electrolyte concentration and pH, it appears that the PVM-cell component complex may be in the nature of a weak salt.

A resistant variant of mumps virus; multiplication of the variant in the presence of inhibitory quantities of Friedländer bacillus polysaccharide

Serial passage of mumps virus in the presence of inhibitory quantities of the capsular polysaccharide of Friediänder bacillus type B results in the appearance of a variant strain of the virus. Multiplication of the variant virus is not inhibited by the polysaccharide. A similar resistant variant is obtained with polysaccharide in a single cycle of multiplication when very large inocula of mumps virus are employed. The resistant variant is indistinguishable from the parent strain as to infectivity, reactivity with erythrocytes, and immunological properties, but appears to have a somewhat slower rate of multiplication. Serial passage of the resistant variant in the absence of polysaccharide results in the reappearance of a sensitive strain. It is suggested that mumps virus populations are inhomogeneous; that naturally occurring variants are present in such populations and possess distinctive properties; that the use of a chemical inhibitor of mumps virus multiplication makes possible the selection of a variant possessing a predictable property. The findings are discussed in relation to the mechanism of inhibition of mumps virus multiplication by polysaccharide.

Persistent antigenic variation of influenza A viruses after incomplete neutralization in ovo with heterologous immune serum

Antigenic variants of influenza A virus strains emerge on serial passage in ovo in the presence of immune serum against different but related strains. An old laboratory strain (PR8) which had been through hundreds of animal passages was as readily modified by this procedure as recently recovered strains. Such variants apparently can be obtained at will and show antigenic patterns which are reproducible and appear to be predictable in terms of the immune serum used for their selection. Variant strains retain their new antigenic patterns on serial passage in ovo in the absence of immune serum. Limited serial passage in ovo of strains in the absence of immune serum did not result in the emergence of antigenic variants. Similarly, serial passages of strains in ovo in the presence of immune serum against widely different strains, which failed to show significant cross-neutralization, did not lead to the appearance of antigenic variants.

Enzymatic variants of influenza virus. I. Isolation and characterization of slowly reacting enzymatic variants of influenza B virus

Slowly reacting enzymatic variants of the Lee strain of influenza B virus were isolated by the serial application of a technique which concentrated the fraction of the virus population obtained by slow elution followed by passage of this fraction at high dilution in chicken embryos. The variants were stable upon serial passage in chicken embryos and did not differ significantly from the parent virus in any of the characteristics tested other than those relating to the virus enzyme. Enzymatically, the variants had a much slower rate of activity on chicken mucoproteins than the parent virus. Their activity was greater at 25 degrees C. than at 37 degrees C. and was much enhanced by calcium ions and depressed by a calcium chelating agent. The enzyme of the variant virus was more labile to heat than that of the parent virus although their hemagglutinins were equally stable. It was estimated that the variants comprised less than 3 per cent of the original population of the Lee strain of influenza B virus particles.