Zvonimir Dinter

Genetic Markers Associated with Virulence of Foot-and-Mouth Disease Virus.∗

Summary Attenuated strains of FMDV types A4, C and O3 are more sensitive to heat and acid inactivation than virulent strains. The attenuated strains of FMDV type C and O3 are inhibited by dextran sulphate which does not affect the other strains.

Equine abortion (herpes) virus: Properties of the hemagglutinin in virus suspensions

Abstract Equine abortion virus (EAV), a herpesvirus, agglutinates horse red blood cells (RBC). The hemagglutinin appears to be an integral part of the viral envelope and is not “soluble” as was formerly anticipated. The hemagglutination proved to be stable at 4 °, 20 °, and 37 °, and could not be reversed by Vibrio cholerae neuraminidase. Trypsin could not be used for reversion since RBC treated with trypsin proved to be nonagglutinable by EAV. The hemagglutinating (HA) activity was destroyed by dithiothreitol indicating the role of disulfide groups in hemagglutinin. The HA activity was also destroyed by proteolytic enzymes (trypsin, α-chymotrypsin, or Pronase), but proved to be resistant to the action of lipid solvents (chloroform or ether) or phospholipase C. The EAV hemagglutinin is thus a protein, the activity of which is not dependent on lipids. In fresh virus harvests the HA titers were directly proportional to infectivity titers, 1 HA unit being equal to about 10 7.0 plaque-forming units in PK-15 cells. In virus preparations, purified from such harvests, 1 HA unit was found to be equal to approximately 0.65 μg protein. These figures might explain why the antibody response to hemagglutinin was poor following immunization by natural infection or vaccination.

The reversion of guanidine inhibition of poliovirus synthesis

Abstract The inhibitory effect of guanidine on the multiplication of poliovirus in HeLa cells is suppressed by the amino acids methionine, leucine, and valine but also by choline. Of substances structurally similar to choline, dimethylethanolamine and dimethylpropanolamine are much more effective and ethanolamine is also more effective than choline. A synergistic effect between choline derivatives and amino acids could be demonstrated. Cells of different origin differed in response to various guanidine competitors. Guanidine inhibition was reversed most effectively by choline in KB cells and by dimethylethanolamine in HeLa cells, but cynomolgus monkey kidney cells gave only partial reversion with these metabolites. The reversion of guanidine inhibition was, however, not affected by actinomycin or folic acid analogs. The guanidine competitors could neither affect the yield nor replace guanidine for guanidine-dependent variants of the virus in HeLa cells. A low molecular weight compound was demonstrated in poliovirus-infected cells but not in uninfected cells that were labeled with choline-C 14 H 3 . The implications of these findings on the mechanism of guanidine inhibition are discussed.

Properties of foot-and-mouth disease virus in tissue culture. II. Persistent infection induced by temporary exposure of the cultures to antibodies.

By temporary exposure of FMDV-infected calf kidney cultures to homologous antibodies a persistent infection was observed. The persistently infected cultures showed resistance to challenge with 100 TCD50 of the FMDV-strain used, for about 8–10 days after removal of antiserum, although persistent infection could be detected for additional 10 days. The persistent infection could be cured by antibody and in fully developed persistently infected cultures each 200th–600th cell was infected with cytopathogenic virus.

Properties of foot-and-mouth disease virus in tissue culture. I. Changes in plaque morphology and antigenicity following passage in tissue culture.

By passage of the Brussels-O strain of foot-and-mouth disease virus through tissue cultures, variants were obtained which differed from the original virus in antigenicity, antigenic character, and rate of neutralization by homologous and probably also heterologous antibodies. Further, a variant forming a plaque-pattern different from that of the parental strain was obtained. An increase in cytopathogenicity was also observed during tissue-culture passages. The nature of the variance is discussed, and it seems probable that passage through tissue culture selectively favours the virus of the variant type in the heterogenous original population.

Suppression of the inhibitory action of guanidine on virus multiplication by some amino acids

Abstract The inhibition of foot-and-mouth disease virus (FMDV) multiplication by guanidine-HCl (GHCl) is suppressed by lactalbumin hydrolysate (LAH) in a concentration of 10 mg/ml and to a certain extent by Eagles minimal essential medium (MEM). It was found that the suppression of the effects of GHCl by MEM is due mainly to the amino acids methionine, valine, leucine, and threonine in decreasing order of effectiveness. Fractionation of LAH by gel filtration on Sephadex G 25 and subsequent amino acid analysis showed the effect of LAH to be due mainly to the same active amino acids as in MEM; in addition, the alanine and serine present in LAH had a slight effect. The optimal concentration of methionine was found to be 0.5–1.0 m M , which is approximately the concentration present in a solution of 10 mg LAH per milliliter. The inhibition of the bovine enterovirus, G-UP, by GHCl is also suppressed by LAH whereas the inhibition of this virus by 2-(α-hydroxybenzyl)benzimidazole (HBB) is not affected.

Vergleichende Untersuchungen über die atypische und klassische Hühnerpest

Die von Traub (1942) als atypische Htihnerpest bezeichnete und in Europa zur Zeit weitverbreitete u liefert beim t t u h n ein Zerlegungsbild, wie es yon der sogenannten klassischen tI i ihnerpest her bekannt ist. Klinisch besteht jedoch insofern ein auffal lender Unte~schied zwischen den beiden Krankheiten, als die Inkubat ionsfrist nach ktinstlicher Infektion bei tier atypischen Pest l~nger und der Krankhei tsablauf 1.angsamer ist als bei der i iberaus stiirmisch ~erlaufenden klassischen Hiihnerpest. Der ausschlaggebende, zuerst yon Traub festgestellte Untersch,ied ist der immunologische. Es besteht keinerlei immanisatori~che Verwandtschaft zwischen den beiden Erregern. Die atypische Pest ahnelt weitgehen, d der asiatischen Gefliigelpest (Newcastle-Krankheit oder Pseudovogelpest), mit der sie jedoch erst nach dem Kr iege wird eingehend verglichen werden kSnnen. Die vorliegende Arbeit befal~t sich m i t der noch offenen Frage, ob das urs~ichliche Agens der atypischen Pest einen immunologischen Typ des Hiihnerpestvirus oder aber einen selbstan.digen Krankhei tserreger darstellt.