The inactivation of enterovirus infectivity by the sulfhydryl reagent p-chloromercuribenzoate

Spectrum and characteristics of the virus inhibitory action of 2-(alpha-hydroxybenzyl)-benzimidazole

2-(α-Hydroxybenzyl)-benzimidazole (HBB) inhibited the cytopathic effects of the following enteroviruses: polio 1 to 3; Coxsackie A9; Coxsackie B 1 to 6; and ECHO virus types 1 to 9, 11 to 21, and 24 to 27. The following enteroviruses were not inhibited: Coxsackie A types 7, 11, 13, 16, and 18; and ECHO types 22, 23, and 28. Other HBB-insusceptible viruses were: arbor B and C, reo 1 to 3; adeno 2 to 4; influenza B; para-influenza 2 and 3; mumps; herpes simplex, and vaccinia. HBB had no inactivating effect on viral infectivity, but rather inhibited some intracellular step in the reproductive cycle of susceptible viruses. With all viruses examined, inhibition of viral cytopathic effects appeared to be due to inhibition of virus multiplication. Virus inhibition by HBB was demonstrable in monkey kidney, HeLa, and ERK cells. HBB-susceptible viruses varied quantitatively in their susceptibility to the compound, and different strains of the same virus also exhibited varying susceptibility. No relationship was found between attenuation of polioviruses and their susceptibility to the compound. After passage of HBB-susceptible enteroviruses in the presence of the compound, virus populations with lowered susceptibility to HBB were obtained. At virus inhibitory concentrations, HBB did not affect the morphology of cells, nor the following cellular metabolic activities: oxygen uptake; glucose utilization; lactic acid production; and incorporation of adenosine into RNA, and of alanine into proteins. The rates of multiplication of HeLa and ERK. cells were not significantly altered by HBB at virus inhibitory concentrations.

Age and susceptibility of mice to Coxsackie A viruses

Mice varying in age from 1 day to 8 months were inoculated intraperitoneally with Coxsackie A virus, type 9 and studies were made of the quantity of virus in striated muscle and myocardium, the presence of neutralizing antibody in the serum, and the pathological changes in the tissues. The hind limbs of young (1- to 20-day-old) mice yielded high titers of virus and showed diffuse myositis, whereas only low yields of virus and focal myositis were obtained in older mice. In the 20-day-old mice the skeletal lesions were not accompanied by manifest symptoms and histologically showed evidence of regeneration progressing from the 3rd to the 11th day after inoculation. Older mice showed no symptoms and only focal myositis and low yields of virus were found in their hind limbs. Coxsackie A9 virus replicated to relatively low titers in the hearts of young (1- to 40-day-old) mice without producing any demonstrable lesions whereas frank myocarditis with high yields of virus were demonstrated in mice infected at 8 months of age. The data suggest that at least for the 2 strains used, the adult mouse should be considered susceptible to subclinical infection with Coxsackie A9 virus. Neither subclinical infection, nor antibody formation was demonstrable in young adult mice inoculated with a strain of Coxsackie A4 virus.

Formation and activity of covalent conjugates of poliovirus and ligands binding to cell surface structures

Disulfide-linked conjugates of poliovirus with streptavidin or concanavalin A were formed and the binding of the conjugates to mouse L cells that lack natural poliovirus receptors was studied. The conjugate with streptavidin was specifically bound to biotinylated L cells, but not to unmodified L cells. The conjugate with conA was bound to L cells in the absence of, but not in the presence of alpha-methyl mannoside. Incubation of L cells with bound conjugates did not produce virus, although the conjugates were highly infectious in HeLa cells, containing natural poliovirus receptors. This suggests that the artificially bound virus was unable to penetrate the L cells and start replication. The possibility that binding of the virus to the natural receptor is required for efficient infection is discussed.

Effect of sulfhydryl reagents on the infectivity of vesicular stomatitis virus

The infectivity of vesicular stomatitis virus (VSV) was moderately affected by iodoacetic acid and drastically affected by N-ethylmaleimide; the antiviral effect of these sulfhydryl reagents was enhanced somewhat by the reducing agent, 2-mercaptoethanol. Reducing and/or alkylating reagents did not affect VSV hemagglutination and the impermeable sulfhydryl reagent, dextran-maleimide, did not significantly influence VSV infectivity. These data indicate that glycoprotein spikes are not the major sites for the antiviral activity of sulfhydryl reagents. [¹⁴C]Iodoacetic acid was able to penetrate the virion membrane to bind covalently to the free sulfhydryl groups of all five virion proteins, particularly the reduced disulfides of the L protein. The RNA polymerase activity of intact VSV was inhibited by iodoacetic acid and to a greater extent by N-ethylmaleimide, which probably accounts for the loss of viral infectivity caused by the permeable sulfhydryl reagents.

Loss on serial passage of rhesus monkey kidney cells of proteolytic activity required for Sendai virus activation

Primary and secondary cultures of rhesus monkey kidney cells supported multiple-cycle replication of Sendai virus, but later passages lost this ability, and this was reflected in decreased plaque formation. Multiple-cycle replication also did not occur in LLC-MK2 cells, a continuous line of RMK cells. Failure of replication in serially passed cells was correlated with a decrease in proteolytic cleavage of a viral surface glycoprotein (Fo), and the ability of cells to support multiple-cycle replication and plaque formation could be restored by the addition of trypsin (0.3 microgram/ml) to the overlay medium. The use of wild-type virus, which requires trypsin, and protease activation mutants that require chymotrypsin or elastase for activation has provided evidence that the activating protease supplied by primary or secondary cells has trypsin-like activity. Inactive virus, with uncleaved Fo glycoprotein, absorbed to primary or secondary cells but did not infect them, even though such cells possess the enzyme that is capable of cleaving the Fo glycoprotein of virus synthesized in these cells. The inability of these cells to activate adsorbed virus indicates that the activating protease that they possess is inacessible to adsorbed virus, although it can act on the Fo glycoprotein during virus maturation in these cells. These data provide a biochemical explanation for the failure of later passages of a cell strain or a continuous cell line to support the replication of a paramyxovirus.

R factor-mediated antibiotic resistance in Shigella

The infectivities of herpes simplex virus types 1 and 2 were inactivated by silver nitrate at concentrations of 30 μM or less, which did not affect at all the infectivities of hemagglutinating virus of Japan, vesicular stomatitis virus, poliovirus, vaccinia virus, and adenovirus. The inactivated virus retained the capability of adsorbing to the cell, with an adsorption kinetics quite similar to that of intact virus, and of inducing the concanavalin A agglutinability in the infected cells, whereas it lost completely the capability of producing viral antigens and other cytopathic changes.

Virucidal effect of sodium p-chloromercuribenzoate on influenza viruses attributable to inhibition of virus particle-associated RNA-dependent RNA polymerase

Sodium p-chloromercuribenzoate (PCMB) caused a noticeable reduction of infectivity of prototype strains of type A and Lee strain of type B influenza viruses at concentrations of 100 and 200 mug/ml, respectively, after an incubation at 37 C for 60 min. The virucidal effect on A/AA/2/60 (H2N2) strain was dependent on the concentration of the drug and temperature as well as on the time of incubation. The reagent exerted this effect at a concentration which induced little change in the hemagglutinating and neuraminidase activities of the virus. PCMB inhibited by 50% the virus particle-associated RNA polymerase activity of all prototype strains of type A influenza virus at about 2 mug/ml and that of Lee strain of type B influenza virus at 8.5 mug/ml. Other sulfhydryl reagent such as phenylmercuric nitrate also exhibited virucidal effect on A/AA/2/60 virus which paralleled their inhibition of the virus particle-associated RNA polymerase activity. From these results it was considered likely that the virucidal action of PCMB on influenza viruses was attributable to inhibition of the virus particle-associated RNA polymerase activity.

Inactivation and heat stabilization of poliovirus by 2-thiouracil

Treatment of poliovirus Type I with 10(-3)m 2-thiouracil (2-TU) resulted in the inactivation of greater than 90% of the virus infectivity and stabilization of approximately 50% of the residual virus to heat inactivation. These effects were due to a reaction with the protein moiety of the virus and could be blocked by pre-treatment of the virus with l-cystine or of the drug with cysteine. Both inactivation and stabilization occurred synchronously and reached equilibrium at the same time. Neither process was reversed by reducing agents. It is suggested that an oxidized form of 2-TU reacts with capsid sulfhydryl groups to form a product which is stable in either the inactive or heat-resistant form.

Isolation and properties of the helical nucleocapsid of the parainfluenza virus SV5

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Distribution of cell receptors and simple sugar inhibitors during encephalomyocarditis virus-cell union

Encephalomyocarditis (EMC) virus was studied for ability to agglutinate erythrocytes of various species. Human, rat, and guinea pig erythrocytes, as well as those from young rabbits, were readily agglutinated. Cells from older rabbits absorbed virus poorly, and showed little agglutination. Uptake of virus by rabbit brain also diminished with age. Various mouse tissues absorbed virus about equally well. Hemagglutination-inhibition studies demonstrated that a number of simple sugars, particularly glucose and galactosamine, interfered with uptake of virus by cells. Dextran sulfates were highly active inhibitors of EMC hemagglutination. Attempts to localize the site of action of the sugars on virus or cell are described. Treatment of virus with periodate or p-chloromercurobenzoate, and acetylation of virus, inhibited hemagglutination, but acetylation of semipurified receptor did not. Clarification of the nature of the virus-cell union will require studies to identify possible specific sugars in the virus capsid and the cell receptor.

On the role of the response of the cell membrane in determining virus virulence. Contrasting effects of the parainfluenza virus SV5 in two cell types

The simian myxovirus SV5 multiplies in a continuous line of baby hamster kidney (BHK21-F) cells causing extensive cell fusion, followed by cell death. After inoculation of 15 PFU/cell, the latent period was 7 hr, the doubling time approximately 60 min, and the yield 7 PFU per cell. Giant cell formation began about 6 hr after infection and rapidly progressed to the formation by 14 to 18 hr of a single syncytium which disintegrated by 24 to 36 hr. In contrast, SV5 multiplies in primary rhesus monkey kidney cells for long periods of time producing high yields of virus with little cytopathic effect. High multiplicities of SV5 induced cell fusion in BHK21-F cells within 1 hr in the absence of virus multiplication but had no visible effect on monkey kidney cells. Time-lapse photomicrography has demonstrated that giant cells form by fusion of infected cells, and that some polykaryocytes divide. During aberrant division of polykaryocytes giant nuclei are formed from the nuclear material of several parent nuclei. The cytoplasmic development of viral antigens as demonstrated by immunofluorescence is similar in BHK21-F and monkey kidney cells. Synthesis of cellular DNA, RNA, and protein in monkey kidney cells is not shut off by SV5-infection, and in BHK21-F cells synthesis of these macromolecules is not inhibited until after extensive cell fusion has occurred 12 to 15 hr after infection. Persistently infected BHK21-F and monkey kidney cells have been serially carried through 11 and 28 cell passages, respectively. The results suggest that whether SV5 acts as a moderate virus, as in monkey kidney cells, or a virulent virus, as in BHK21-F cells, depends on the response of the cell membrane to the virus.