Heterogeneity of Coxsackie B4 virus: two kinds of particles which differ in antibody sensitivity, growth rate, and plaque size

Experimentally induced alterations in antigenic properties of an arbovirus serotype

Antigenic properties of Getah virus were monitored during 80 serial passages in Vero tissue cultures. The parent virus lost its serotype identity by passage 80. A clone derived from the parent remained antigenically stable during passage. The experimentally induced antigenic alterations in Getah virus were attributable to the tissue culture host selection of constituent subpopulations of virus with properties unlike those of the original parent. The marked differences in neutralization titers of low- and high-passage virus were considered related to or influenced by (i) the variation in subpopulation selection of the virus during passage and (ii) the variation in availability of antigenic stimulants during preparation of antiserum.

Impact on routine diagnosis of echovirus infections of intratypic differentiation and antigenic variation in echovirus type 25 studied by using monoclonal antibodies

We studied the biological and antigenic properties of wild strains of echovirus type 25 isolated in France between 1982 and 1987 and compared them with the JV-4 prototype strains isolated in 1957. The wild strains differed from the prototype strain in their cellular tropism. The prototype strain grew readily in five cell lines (MRC5, MA 104, Vero, BGM, and HT 29-18), while for wild strains MRC5 and HT 29-18 cells were the most sensitive and supported growth to high titres (between 4.5 and 7.4 50% tissue culture infective doses per 0.05 ml). Plaques produced by wild strains were larger (6.05 +/- 0.94 mm in diameter [mean +/- standard deviation]) than those of the prototype strain (2.3 +/- 0.97 mm in diameter) and heterogeneous, even after cloning by three terminal dilution passages, which suggested heterogeneous virus populations. Virus neutralization with polyclonal monovalent sera showed that wild strains were significantly less neutralized by two reference immune sera than the prototype strain was. Monoclonal antibodies were raised against the echovirus type 25 JV-4 prototype strain. Nine clones with neutralizing activity were identified. Heterologous neutralizations of 14 clinical isolates revealed highly conserved, moderately conserved, and poorly conserved epitopes. The natural isolates differed from the prototype strain in two to four epitopes and can be classified into four different groups. We concluded that echovirus type 25, like coxsackie- and polioviruses, consists of heterogeneous viral populations with respect to biological and antigenic properties. In term of viral diagnosis, it may become increasingly difficult to identify recently isolated strains because of their antigenic variation.

Polysaccharides as antiviral agents: antiviral activity of carrageenan

A number of polysaccharides showed good antiviral activity against several animal viruses. At 5 micrograms/ml, carrageenan prevented the cell monolayer from destruction by herpes simplex virus type 1 (HSV-1) growth. At 10 micrograms/ml, carrageenan reduced the formation of new infectious HSV-1 by almost five logs. No cytotoxic effects were detected with concentrations of carrageenan up to 200 micrograms/ml. When 10 micrograms of carrageenan per ml was added at the beginning of HSV-1 infection of HeLa cells, there was potent inhibition of viral protein synthesis, and the cells continued synthesizing cellular proteins. This did not occur if carrageenan was added 1 h after HSV-1 infection. The use of [35S]methionine-labeled virions to analyze the entry of HSV-1 or Semliki Forest virions into cells indicated that carrageenan had no effect on virus attachment or virus entry. Moreover, carrageenan did not block the early permeabilization of cells to the toxic protein alpha-sarcin. These results suggest that this sulfated polysaccharide inhibits a step in virus replication subsequent to viral internalization but prior to the onset of late viral protein synthesis.

Differing cardiotropic and myocarditic properties of group B type 4 coxsackievirus strains

A murine model system for evaluation of myocarditic and cardiotropic properties of strains of group B, type 4 coxsackievirus (CBV-4) was developed in male BALB/c mice 4 weeks of age. Differing cardiotropic and myocarditic properties could be identified among field strains within the CBV-4 serotype. These properties were consistent for the virus strains, and were independent of the infecting virus dose. Virus replication in the heart appeared to be essential for development of myocarditis, but some infected hearts with high levels of infectious virus did not show myocarditis. Two of the myocarditic strains showed different histopathology in infected hearts; with one strain (Mil) the myocarditis was characterized by a marked inflammatory reaction with occasional accompanying myofiber necrosis. With the other strain (Bol), necrosis was the predominant finding, with a much lesser degree of inflammation. These findings suggest that there may be various pathogenic or immunopathogenic mechanisms by which CBV-4 can produce myocarditis.

Altered receptor specificity of coxsackievirus B3 after growth in rhabdomyosarcoma cells

Serial "blind" passages in human rhabdomyosarcoma (RD) cells of prototype viruses from each of the six immunotypes of the group B coxsackieviruses (CB) resulted in the isolation of intratypic variants of CB1, CB3, CB5, and CB6. Each variant virus strain acquired the capacity to agglutinate human erythrocytes and produce small plaques on HeLa cells, although their serological specificity remained unchanged. An alteration in VP1 mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis was noted for CB3-RD. The CB3-RD variant was plaque purified on RD cells and studied for receptor interactions on both HeLa and RD cells. An attachment restriction appeared to exist for prototype CB3 on RD cells, whereas CB3-RD attached well to both cells. In attachment interference assays, HeLa cells saturated with CB3-RD blocked the attachment of CB3. In contrast, saturation of cells with CB1 (which shares a common receptor with parental CB3) failed to block the attachment of CB3-RD. This unidirectional receptor blockade suggested that a second site for the attachment of virions to receptors was acquired by the CB3-RD variant. Thus, more than one virus receptor specificity may be operative in the selection of host range virus mutants. The implications of this phenomenon as they may relate to pathogenesis are discussed.

Isolation and characterization of an equine rotavirus

A rotavirus, designated as the H-1 strain, was isolated from a diarrheic foal in primary African green monkey kidney cells and MA104 cells. This cell culture-adapted strain hemagglutinated erythrocytes of human group O, rhesus monkeys, guinea pigs, and sheep. It was found to be similar, if not identical, to porcine rotaviruses (strains OSU, EE, and A-580) by plaque reduction neutralization and hemagglutination inhibition tests, and, in addition, it was found to belong to subgroup 1. This equine rotavirus has an RNA electrophoretic migration pattern which was distinct from those of the three strains of porcine rotavirus. The serological relationship established by plaque reduction neutralization and hemagglutination inhibition tests between the equine (H-1) and porcine (OSU, EE, and A-580) rotaviruses is an example of a rotavirus of the same serotype being isolated from different species. The H-1 strain was distinct from four human rotavirus serotypes (Wa, DS-1, P, and St. Thomas 4) as well as from bovine rotavirus NCDV, simian rotavirus MMU18006, and canine rotavirus CU-1 by plaque reduction neutralization tests. This equine isolate (H-1) was found to be related antigenically to canine CU-1 and bovine NCDV rotaviruses in a one-way fashion by hemagglutination inhibition tests.

Cross antigenicity among enteroviruses as revealed by immunoblot technique

Antigenic relationships of various human and two animal picornaviruses were investigated by the immunoblotting ("Western blot") technique. The viruses included all coxsackievirus B types (1-6), poliovirus types 1-3, several strains of echovirus 11, EMC virus, and FMDV. Antisera included human sera and sera from rabbits hyperimmunized with either purified picornaviruses, viral structural polypeptides (VP8), boiled or "sample-boiled" virions. Group-specific reactions of various extent were observed among the human picornaviruses, but not with EMC virus. These reactions were obtained with human sera (whole serum, IgG- and IgM-fraction) as well as with "monospecific" (neutralization test) rabbit antisera. Among cross reacting polypeptides VP1 was predominant with the notable exception of coxsackie B4, where VP1 (defined according to cleavage pattern) migrates in our gel system as second largest polypeptide. Antisera prepared vs VP1 had neutralizing activity as demonstrated with five different echovirus 11 strains (titers up to 2000). Antisera vs VP1 (and other VP8) exhibited cross-reactivity in the immunoblots. Antisera to the three poliovirus types (and to certain echovirus 11 strains) showed a surprisingly narrow cross-reacting spectrum which--in the case of poliovirus--could not be broadened by additional hyperimmunization of the rabbits with heated poliovirus 2. The significance of these results for a diagnostic ELISA in patients with picornavirus infections is dealt with.

Antiviral activity of an alcoholic hand disinfectant. Comparison of the in vitro suspension test with in vivo experiments on hands, and on individual fingertips

The inactivation of eleven viruses by a commercial alcoholic hand disinfectant ("Desderman') was tested by three different procedures, viz., in vitro in a standardized suspension test, in vivo on the entire surface of both hands, and in vivo on individual fingertips of a single volunteer. The test protocols were chosen such as to make results comparable. The influence of varying disinfectant/virus volume ratios, serum protein loads, and reaction temperatures was evaluated in vitro, and partly demonstrated in vivo. In some experiments, 5% formaldehyde was included as a reference disinfectant. The experiments support the prevailing concept, that enveloped viruses are considerably more susceptible to alcoholic disinfection than naked ones. Additionally, enveloped viruses were shown to be subject to more "spontaneous' decay on skin. The main result of the study appears to be that the in vitro model predicted a greater effectiveness of the disinfectant than was observed in vivo both in the "hand' test and the "finger' test, although some differences were noted between these tests. Reasons for the lesser in vivo inactivation may lie in the evaporation of the disinfectant with ensuing changes in disinfectant/virus volume ratio, effective temperature, and inactivation time, all shown to influence disinfection. Other mechanisms such as a "sheltering' effect of the skin may have also been operating. The results suggest that, at the present stand of knowledge, in vitro screening tests should be complemented by in vivo tests for the evaluation of antiviral hand disinfectants.

An application of factor analytics on antigenic drift, and chromatographic analysis on intratypic variation of enterovirus type 70

An attempt was made to reveal the antigenic determinant site of enterovirus (EV) 70 by application of Harman's factor analytics. The normalized neutralization rate constant (NK) values obtained by the kinetic-neutralization tests (NT) with 12 strains of EV70 isolated during the period from 1971 to 1976 were used in the principal factor analysis. From the analytic results, it was suggested that at least two antigenic determinant sites, composing to variable antigenic factor (VAF) and common one (CAF), might be closely related to the antigenic makeup. There were no significant differences in CAF score among the strains, and they were numerically classified into prototype-like and prime-like virus groups from the VAF scores. The drift appeared here could be explained as successive alteration of VAF scores. Chromatographic analyses were carried out on intratypic variable and common particles with two virus strains, i.e. the prototype J 670/71 and prime G-2/74. The intratypic variable and common particles were eluted in low and high ionic concentrations at neutral pH, respectively. It was concluded that the virus populations of two strains were heterogenic in the proportion of variable to common virus particles.

Antigenic analysis of acute hemorrhagic conjunctivitis viruses (enterovirus type 70)

The antigenic characteristics of enterovirus type 70 (EV 70) were investigated by means of cross and kinetic neutralization tests (NT). Twelve strains of EV 70 isolated in a period from 1971 to 1976 were analyzed using seven rabbit and one monkey hyper-immune sera. All the strains investigated were found to possess a common and prime variant antigens in varying proportions. Accordingly, EV 70 isolates were devided intratypically into three antigenic sub groups; (1) prototype-like (four strain from 1971 to 1972), (2) intermediate, G-10/72-like (two strains from 1972 to 1973), and (3) prime variant, G-2/74-like (six strains from 1974 to 1976) groups. Thus it was considered that EV 70 might represent a virus type with antigenic heterogeneity, and that antigenic drift from the prototype to the prime type may have occurred successively after 1971.

Isolation of a virus from the pancreas of a child with diabetic ketoacidosis

A healthy 10-year-old boy was admitted to the hospital in diabetic ketoacidosis within three days of onset of symptoms of a flu-like illness. He died seven days later and post-mortem examination showed lymphocytic infiltration of the islets of Langerhans and necrosis of beta cells. Inoculation of mouse, monkey and human cell cultures with homogenates from the patient's pancreas led to isolation of a virus. Serologic studies revealed a rise in the titer of neutralizing antibody to this virus from less than 4 on the second hospital day to 32 on the day of death. Neutralization data showed that the virus was related to a diabetogenic variant derived from Coxsackievirus B4. Inoculation of mice with the human isolate produced hyperglycemia, inflammatory cells in the islets of Langerhans and beta-cell necrosis. Staining of mouse pancreatic sections with fluorescein-labeled antiviral antibody revealed viral antigens in beta cells. Both the clinical picture and animal studies suggested that the patient's diabetes was virus induced.

Successful treatment of enterovirus-infected mice by 2-(alpha-hydroxybenzyl)-benzimidazole and guanidine

Echo virus 9- or Coxsackie A 9-infected newborn mice are protected from paralysis and death by combined treatment with nontoxic concentrations of HBB plus guanidine. HBB alone also protects Coxsackie A 9, but not echo virus 9-infected animals, whereas guanidine alone is ineffective in either case. Protection is due to inhibition of virus multiplication via the antiviral activity of these selective inhibitors. Treatment must be begun at the latest 48 h after virus inoculation. 3 days of treatment are sufficient if started at the time of virus inoculation. Failure of protection after treatment with one compound alone is not due to rapid development of drug-resistant virus mutants. Infected, successfully treated mice may develop a solid immunity.

Antigenic relationships among Newcastle disease virus mutants obtained from laboratory strains and from recent California isolates

The antigenic relationship between pairs of plaque mutants of Newcastle disease virus (NDV) derived from laboratory strains and from isolates from the 1971-72 California epizootic were examined by kinetic neutralization test. Comparing four sets of mutants from laboratory strains by both kinetic neutralization and hemagglutination inhibition tests, a similarity was found in the antigenic relationship expressed as an r value with both tests. However, kinetic neutralization was the more precise as well as sensitive assay. Antigenic diversity was greatest between pairs of mutants from different strains, but distinctions could also be made between mutants from the same strains such as Herts-L and Herts-S with an r value of 36%. Examination of mutants from the California epizootic isolated from separate locations and at different times showed antigenic divergence which was greatest between two red-plaque mutants with an r value of 39%. Antigenic distinctions were found between a red- and clear-plaque mutant obtained from isolates taken from brain and tracheal swabs of one infected chicken. In addition to antigenic divergence found between pairs of some mutants, two of the clear-plaque mutants reacted more avidly with antibody than did the corresponding red-plaque partner. Thus, both differences in antigenicity and avidity can be found among these NDV mutants. The antigenic variation found among these mutants is similar to that found within a serotype. This would imply that at the present NDV is a single serological type.

Isolation of a specific enhancer for echovirus 6 from uninfected permissive host cells

A specific enhancer for the m+ variant of echovirus 6 was isolated from uninfected, permissive host cells. The enhancer transferred the susceptibility to virus infection from permissive cells to less susceptible cells. Enhancer activity in cultured, human cells (WISH) was released by these cells into extracellular fluids at a linear rate. Maximal enhancer activity was recovered from cell monolayers that were extracted with buffered salt solutions (pH 6.6) for 5 h at 37 C. Crude enhancer preparations contained substances that reduced virus titers in permissive host cells and suppressed some of the enhancer activity. Viral inhibitory activity was removed from cellular extracts by either differential centrifugation or ion exchange chromatography. The enhancer, in contrast to inhibitory substances, remained in supernatant fractions after centrifugation at 110,000 x g for 4 h and adsorbed to diethylaminoethyl-Sephadex columns. Enhancer preparations that were devoid of inhibitory activity increased the virus titers in less susceptible simian cell cultures (approximately 100-fold) to the titers attained by fully permissive human cell cultures. A direct relationship between protein concentration and enhancer activity in cellular extracts was demonstrated. Partial purification of the enhancer by differential centrifugation and ammonium sulfate precipitation increased the specific activity of enhancer (units/mg of protein) by 13-fold.

Comparison of agar and agarose preparations for mengovirus plaque formation

An agarose overlay yielded mengovirus plaques earlier and in greater size and number than overlays of chemically undefined agars with or without enhancers. Marked variability in plaque-forming efficacy of commercial agarose preparations was noted.

Markers of rubella virus strains in RK13 cell culture

When tested on RK(13) cell cultures, strains of rubella virus could be differentiated by their ability to form small or large plaques. Large plaques were produced by the HPV-77 and Cendehill strains, and also by a laboratory stock strain (West Point), after only 14 passages in RK(13) culture. Five wild-type rubella viruses, isolated and passaged only a few times in African green monkey kidney tissue culture, grew well in RK(13) cell culture, but they were sensitive to agar inhibitors and, therefore, formed small plaques. On the other hand, RA27/3, an attenuated strain grown in WI-38 human fibroblast cells, developed low titers in RK(13) cells and also produced small plaques. We concluded that the morphological differences between small-plaque and large-plaque viruses depended on their sensitivity to agar inhibitors and on the pH of the medium during plaque formation.

Relationship of plaque size and virulence for chickens of 14 representative Newcastle disease virus strains

Ability of 14 Newcastle disease virus strains to produce large plaques was related to virulence for chickens. Plaque-size comparisons were made under standard conditions in chick embryo cell monolayers. All plaque-producing strains showed a range of plaque sizes modified to a degree by the overlay medium used. An increase in size was found for most strains under methyl-cellulose overlay medium. Markedly larger plaques were found under this medium for both Calif-RO and Calif-CG strains. Heterogeneity in plaque size was most pronounced in velogenic (high virulence) strains. Only populations of small plaques were found in mesogenic (intermediate virulence) strains, and plaques were rarely found in lentogenic (low virulence) strains. Statistical analysis showed that the plaque size of velogenic strains differed significantly from mesogenic strains. None of the 11 plaque-producing strains had a normal distribution of plaque sizes, owing primarily to the presence of different genotypes within the plaquing population of a strain. This was demonstrated by derivation of clones from two of the strains. The populations of the large (Herts L) and small (Herts S) clear plaque clones derived from Eng-Herts were homogenous and distinct from one another on the basis of plaque size. Herts L was more virulent than Herts S. Although Herts L became more heterogenous in respect to plaque size upon repeated passage in embryonated eggs, no decrease in virulence of the strain was observed.

Studies on plaque variants of coxsackievirus B5 by burst analyses

Propagation of coxsackievirus B5 on cell lines revealed two variants, one that yields small plaques and is stable and another that is large but variable in size. Multiple-burst studies on the large-plaque pool showed the existence of two different population sections. Analysis of a sample from a plaque belonging to the small population section showed a progeny of small plaques while a similar analysis from a plaque in the large population section produced plaques of varying size but whose mean plaque diameter resembled that of the parent culture. Repeated selection for smallness from plaques in the large population section resulted in small plaques and a shift from the large to the small population section. Analysis of the small pool virus on monkey kidney monolayers revealed the presence of a few typical monkey kidney plaques which differed from normal monkey kidney plaques by producing only small plaques on HEp-2 monolayers.

Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin

Wallis, Craig (Baylor University College of Medicine, Houston, Tex.), Fred Morales, Joycelyn Powell, and Joseph L. Melnick. Plaque enhancement of enteroviruses by magnesium chloride, cysteine, and pancreatin. J. Bacteriol. 91:1932-1935. 1966.-Plaque formation of 21 echoviruses (types 1-6, 9, 13, 15-19, 23-26, 29-32) and 8 coxsackieviruses (B1-6, A7, and A9) was enhanced by increased concentrations of MgCl(2), l-cysteine, and pancreatin in agar overlay medium. In most cases, cationic and anionic polymers (diethylaminoethyl dextran, dextran sulfate, or protamine sulfate) were ineffective. All strains of poliovirus and group B coxsackieviruses were enhanced under agar by MgCl(2). Five of the eight coxsackieviruses tested were also enhanced by cysteine or pancreatin. Certain enteroviruses, which have been difficult to assay by plaque method, can now be quantified effectively by incorporation of additives such as MgCl(2), cysteine, or pancreatin into the overlay medium.

Inhibition of enterovirus cytopathic effects by 2-(alpha-hydroxybenzyl)-benzimidazole

Bablanian, Rostom (The Rockefeller University, New York, N.Y.), Hans J. Eggers, and Igor Tamm. Inhibition of enterovirus cytopathic effects by 2-(alpha-hydroxybenzyl)-benzimidazole. J. Bacteriol. 91:1289-1294. 1966.-2-(alpha-Hydroxybenzyl)-benzimidazole (HBB), a specific inhibitor of enterovirus multiplication, markedly delayed the development of cytopathological changes induced by echovirus 12 or coxsackievirus B4 in monkey kidney cells, but did not prevent the ultimate degeneration of infected cells, even though virus multiplication was inhibited. The study of the development of viral cytopathic effects was facilitated by the use of antiviral immune serum, which restricted the infection to those cells which became infected by the inoculated virus and thereby established single-cycle conditions. With echovirus 12 and coxsackievirus B4 not all cells could be infected initially, even when cultures were inoculated at input multiplicities in excess of 100 plaque-forming units per cell.