Tissue culture techniques and their application to original isolation, growth, and assay of poliomyelitis and orphan viruses

Phylogenetic characteristics and recombination analysis of echovirus 5 associated with severe acute respiratory infection in China

IMPORTANCE

This study is the first report of echovirus 5 (E5) associated with severe acute respiratory infection and obtained the first E5 whole-genome sequence in China. Combined with the sequences available in the GenBank database, the first genotyping, phylogenetic characteristics, recombination, and genetic evolutionary analysis of E5 was performed in this study. Our findings providing valuable information on global E5 molecular epidemiology.

Genetic diversity of a Korean echovirus 5 isolate and response of the strain to five antiviral drugs

An outbreak of echovirus 5 (ECV 5) occurred in Korea in 2006, marking the first time this virus had been identified in the country since enterovirus surveillance began in 1993. Using a sample isolated from a young male patient with aseptic meningitis, we performed sequencing of the Korean ECV 5 strain and compared it with a prototype strain (Noyce). At the nucleotide level, the P1 region (85.3%) had the highest identity value; at the amino acid level, the P3 region (98.0%) had the highest identity value. The two strains shared all cleavage sites, with the exception of the VP1/2A site, which was TY/GA in the Noyce strain but TR/GA in the Korean ECV 5 isolate. In Vero cells infected with the Korean ECV 5 isolate, no cytotoxicity was observed in the presence of azidothymidine, acyclovir, amantadine, lamivudine, or ribavirin, when the drugs were administered at a CC₅₀ value >100 μg/mL. Of the five drugs, only amantadine (IC₅₀: 1 ± 0.42 μg/mL, TI: 100) and ribavirin (IC₅₀: 22 ± 1.36 μg/mL, TI: 4.55) had any antiviral activity against the Korean ECV 5 isolate.

Evidence for frequent recombination within species human enterovirus B based on complete genomic sequences of all thirty-seven serotypes

The species Human enterovirus B (HEV-B) in the family Picornaviridae consists of coxsackievirus A9; coxsackieviruses B1 to B6; echoviruses 1 to 7, 9, 11 to 21, 24 to 27, and 29 to 33; and enteroviruses 69 and 73. We have determined complete genome sequences for the remaining 22 HEV-B serotypes whose sequences were not represented in public databases and analyzed these in conjunction with previously available complete sequences in GenBank. Members of HEV-B were monophyletic relative to all other human enterovirus species in all regions of the genome except in the 5'-nontranslated region (NTR), where they are known to cluster with members of HEV-A. Within HEV-B, phylogenies constructed from the structural (P1) and nonstructural regions of the genome (P2 and P3) are incongruent, suggesting that recombination had occurred. Similarity plots and bootscanning analysis across the complete genome identified multiple sites at which the phylogeny of a given strain's sequence shifted, indicating potential recombination points. These points are distributed in the 5'-NTR and throughout P2 and P3, but no sites with >80% bootstrap support were identified within the capsid. Individual sequence comparisons and phylogenetic analyses suggest that members of HEV-B have recombined with one another on multiple occasions, resulting in a complex mosaic of sequences derived from multiple parental viruses in the nonstructural regions of the genome. We conclude that RNA recombination is a common mechanism for enterovirus evolution and that recombination within the nonstructural regions of the genome (P2 and P3) has been observed only among members of the same species.

Infectivity of ribonucleic acid from poliovirus in human cell monolayers

Ribonucleic acid prepared by the method of Gierer and Schramm from concentrated and partially purified types I and II polioviruses has been demonstrated to be infectious for HeLa and human amnion cells in monolayers. In areas of cytopathogenic action resulting from invasion of cells by RNA, intact poliovirus, of the type from which the RNA had been prepared, is present. The infectivity of the RNA was completely inactivated by a 2 minute exposure to purified ribonuclease or to whole normal monkey serum shown to contain measurable concentrations of this enzyme. Whole virus infectivity was not influenced by RNAase or whole normal monkey serum. Normal and polio-immune globulin, desoxyribonuclease, lysozyme, proteolytic enzymes, and bovine albumin failed to inactivate the infectivity of RNA. The degree of infectivity of isolated RNA from poliovirus for cells in monolayer was greatly influenced by the ionic strength of the environment. The experimental evidence suggests that isolated poliovirus RNA is the carrier of the biological activity responsible for infection of cells and for transmission of genetic information which controls type specificity.

Echovirus 5: infectious transcripts and complete nucleotide sequence from uncloned cDNA

Echovirus 5 (EV5) may be isolated from various neurological and exanthematic diseases. To determine the relationship of EV5 to other enteroviruses and for studies of its interactions with the target cell, the complete nucleotide sequence of EV5 was determined. Three overlapping fragments, collectively representing the complete genome, were amplified with RT-PCR and sequenced. Analysis of the EV5 sequence revealed a typical enterovirus-like organization of the genome. To verify that the cDNA generated sequence was derived from infectious viruses, complete EV5 genomes were amplified in one amplicon by long distance PCR. Transfection of in vitro transcribed RNA from these amplicons into cell cultures resulted in replicating EV5. Comparison of the overall nucleotide and amino acid sequences demonstrates that EV5 can be regarded as a coxsackievirus B-like enterovirus. Variable sequences between EV5 and the well characterized coxsackievirus B3 (CVB3) are for the most part observed for amino acid residues that correspond to exposed sequences in the CVB3 capsid. This observation indicates that the reported EV5 strain recently diverged from group B coxsackieviruses.

Pathogenicity for suckling mice of Coxsackie viruses adapted to human amnion cells

Continuous passages in primary human amnion cell cultures of Coxsackie prototype viruses A-9, A-10, A-11, A-13, A-14, A-15, A-18, B-1, B-2, B-4, and B-5 increased the titers, hastened and enhanced cytopathic effect, and in varying degrees caused loss of virulence for newborn mice. Only B-3 behaved differently in that neither adaptation to cells in vitro nor attenuation with respect to the original animal host could be observed. Types A-15, B-1, B-2, and B-5 slowly regained virulence when passed in mice after high concentration passages in amnion cells whereas all other viruses reverted to their original virulence after only 1 or 2 passages in the animal host. When these strains, however, were purified by cloning procedures, they too showed markedly increased stability. In all stages of attenuation, viruses multiplied extensively in vivo as could be shown by titration in amnion cell cultures. It is suggested that a genetic mechanism is operative leading to virus populations in which the majority of the particles is qualitatively changed.

Respiratory viruses in a residential nursery

A longitudinal survey of respiratory illness in a Sheffield residential nursery is described. Over 8 months, outbreaks of respiratory illness occurred, two of which were associated with infection by Influenza A and Parainfluenza 3 viruses. The symptomatology is described of the illnesses resulting from these infections. The incidence of adenovirus recoveries over the same period was also investigated and suggests that adenoviruses of Types 1, 2 and 5 may be components of the normal viral flora of the nasopharynx in infants.

Characterization of the RDC1 gene which encodes the canine homolog of a proposed human VIP receptor. Expression does not correlate with an increase in VIP binding sites

We have isolated a portion of the canine gene encoding the orphan receptor RDC1 [1]. The complete coding sequence is contained in a single exon, and an intron divides the 5' untranslated region of RDC1 mRNA. The RDC1 protein is 94% homologous to the gene product of GPRN1, which has been proposed to serve as a VIP receptor when expressed in CHO-K1 and COS-7 cells (Sreedharan, S.P. et al. (1991) Proc. Natl. Acad. Sci. USA 88, 4986-4990). Northern analysis indicates that CHO-K1 cells endogenously express a 2.1 kb RDC1 mRNA. However, while CHO-K1 cells possess detectable low affinity [125I]VIP binding sites, VIP binding is not altered in membranes of CHO-K1 cells expressing varying amounts of the RDC1 gene construct. Further, endogenous VIP binding is not increased by transient expression of RDC1 in COS-7 cells. Taken together, the data suggest that RDC1 is not a canine homolog of the proposed VIP receptor.

Use of serum substitutes for the growth of four cell lines commonly used for virus isolation

Four serum extenders (Opti-MEM I, BioRich, Excyte I and Excyte III) and two serum substitutes (Omni Serum and Serum Plus) were evaluated for the reduction or replacement of FBS for the growth and maintenance of four representative cell lines used for virus isolation. MRC-5, human fetal foreskin fibroblast (HF), A549 and Hep-2 cells were seeded into culture flasks containing MEM with 10% FBS or with the serum extenders or substitutes and subcultured into 16 x 125 mm glass tubes and 1-dram shell vials. Only cells cultured with Opti-MEM I and Omni Serum grew consistently in tubes and vials and these reagents were compared to FBS for viral isolation and detection. Laboratory stocks of CMV, HSV, VZV, adenovirus (Ad) and RSV were tested. In HF and MRC-5 cells, CMV was isolated in cells cultured in either Opti-MEM I or Omni Serum before CPE appeared in cultures containing FBS. Ad and VZV CPE were observed first in HF and MRC-5 cells containing Omni Serum. HSV CPE was seen at the same time in HF and MRC-5 cells with all 3 media. HSV and Ad CPE in A549 cells were also seen at the same time in all 3 media. RSV and Ad CPE in Hep-2 cells were observed first in FBS containing media. Both Opti-MEM I and Omni Serum performed well as substitutes for FBS for growth of stock viruses without loss of cell sensitivity.

Primary culture of ant venom gland cells

Venom from the ant Pseudomyrmex triplarinus reduces the symptoms and swelling of rheumatoid arthritis. The cells that produce the venom were dissected from larval and pupal ants and culture conditions studied. Cell dissociation, with minimal amount of damage, was done with 0.25% trypsin at 4 degrees C with subsequent use of soybean trypsin inhibitor. A new medium was formulated and epidermal growth factor, fibroblast growth factor, insulin, cAMP, cGMP, and isoproterenol were beneficial. The optimum osmotic pressure was a relatively high 500 mOSM. Conditioning the medium with an established insect cell line was essential for long-term cell survival. Under these culture conditions the structural and metabolic integrity of the cells were maintained for up to 12 mo.

Induction of long-term immunity to paralytic poliomyelitis by use of non-infectious vaccine

Naturally acquired immunity to paralytic poliomyelitis, which is of long duration, is associated with serum antibody, immunological memory, or both. Persistence of circulating antibody is reassuring but not essential for long-term protection. Immunological memory induced by killed poliovirus vaccine is similar to that induced by infection, which is not a prerequisite for the induction of long-term immunity. Animal studies of experimental vaccines indicate that some antigenic components of poliovirus induce immunological memory without producing detectable antibody; killed poliovirus vaccine has the same effect in man. Killed vaccine containing 40, 8, and 32 D-antigen units of poliovirus types 1, 2, and 3, respectively, protects all recipients in both one-dose and two-dose schedules. This means that either schedule can be chosen to fit in with local immunisation programmes and thus reduce costs and increase population coverage.

Vasoactive intestinal peptide causes a calcium-dependent stimulation of prolactin secretion in GH4C1 cells

We have studied the effects of vasoactive intestinal peptide (VIP) on PRL secretion in a Bio-Gel column parafusion system containing rat pituitary tumour cells (GH4C1). A dose-dependent increase in PRL release was observed with half-maximal and maximal effect (2.1-fold) at 8 X 10(-8) and 5 X 10(-6) M, respectively. The PRL-stimulatory effect of VIP was instantaneous and maintained during the parafusion experiments (up to 60 min). On a molar basis VIP was always less effective than thyroliberin (THR), and the maximum stimulation of PRL release obtained with TRH was 1.2-3.0-fold higher (n = 12) than the maximum effect seen after VIP administration. The PRL-releasing effects of VIP, THR and high extracellular K+ were almost completely abolished in the presence of two inhibitors of voltage-sensitive Ca2+ channels, CoCl2 (10(-3) M) and verapamil (10(-4) M). In Ca2+-free buffer VIP, TRH and high extracellular K+ had only negligible effects, but the responses were fully restored in the presence of normal concentrations of extracellular Ca2+. In contrast to TRH, VIP had no demonstrable effect on the Ca2+-dependent action potentials of the GH4 cells.

Evaluation of factors related to growth of Rift Valley fever virus in suspended cell cultures

The effect of several controlled variables on the peak titer and fold increase of Rift Valley fever virus grown in suspension culture on two variants of Earle's L cell, L-DR and L-MA clone 1-1, was studied. No significant amount of cell-associated virus was found at 24 hr, indicating a release of virus soon after its formation. Mild sonic treatment of the virus produced in serum-free medium increased the infective titer about 10x. This difference was not observed with virus produced in medium supplemented with serum. Peak titer was not affected by medium used during the infection period, by multiplicity of inoculum (MOI), or by initial cell concentration within the test range of 10(4) to 2 x 10(6) cell/ml. Cell strain employed influenced titer, because the L-DR cell did not produce virus efficiently at low MOI and low initial cell concentration. The time of peak titer and fold replication was dependent on MOI and initial cell concentration. Differences in virus propagation in monolayer and suspension systems are discussed.

Density gradient centrifugation of rubella virus

Rubella virus was centrifuged in sucrose density gradients. One of two densities could be ascribed to the virus, depending upon the suspending medium used. The virus was found at a density of 1.16 g/cm(3) after centrifugation for 18 hr in sucrose gradients prepared in distilled water. By contrast, when the sucrose gradients were prepared in tris(hydroxymethyl)aminomethane (Tris)buffer containing ethylenediaminetetraacetic acid (EDTA), the virus was found at a density of 1.18 g/cm(3) after 18 hr of centrifugation. The virus banded at this higher density after only 2 hr of centrifugation when pretreated by overnight incubation in the Tris-EDTA buffer. A kinetic study showed that, in sucrose gradients containing this buffer, the virus gradually migrated as a single peak of infectivity from a density of 1.16 g/cm(3) after 2 hr of centrifugation to the higher 1.18 g/cm(3) density after 18 hr. The density change was shown to be reversible; after the removal of the Tris-EDTA buffer, rebanding of virus harvested at the heavy density resulted in its banding at the lower 1.16 g/cm(3) density. The data indicate that density change could not be explained on the basis of the loss of some component from the virus or on the basis of the failure of the virus to reach equilibrium. However, it is possible that the two densities observed were a reflection of the existence of rubella virus in different hydration states in the presence and absence of Tris buffer containing EDTA.

Previously unrecognized virus from submaxillary glands of gnotobiotic and conventional rats

Ashe, Warren K. (National Institute of Dental Research, Bethesda, Md.), Henry W. Scherp, and Robert J. Fitzgerald. Previously unrecognized virus from submaxillary glands of gnotobiotic and conventional rats. J. Bacteriol. 90:1719-1729. 1965.-A serially transmissible cytopathic agent was isolated from histologically normal submaxillary glands, but not from various other tissues or specimens, from 74 of 97 gnotobiotic and conventional rats. Triturates of the glands or subsequent culture supernatant fluids induced specific cytopathic effects (CPE) in monolayer cultures of primary rabbit kidney cells (14 passages), a line of human skin cells (8 passages), and HeLa cells (17 passages). Transfer of supernatant fluids containing infected cells enhanced transmissibility. Neutralization of the CPE was demonstrated with sera of gnotobiotic and conventional rats and with homologous rabbit antiserum. A cold hemagglutinin specific for rabbit erythrocytes is associated with, but separable from, the infectious particle. Cultures of the agent induced no discernible effect on inoculation by various routes into suckling, weanling, or adult conventional mice, rats, and hamsters. Weanling and adult rabbits were also unaffected. Cultures for bacteria in gland extracts and infected cell supernatant fluids were uniformly negative. Negative cultures on PPLO media and negative arginine deiminase tests indicated that this agent is not a Mycoplasma. The data indicate that it is a virus whose biological and physical properties distinguish it from the known cytomegaloviruses. Because it has been found so far only in rat submaxillary glands, this agent is designated provisionally as RSMG virus.

Micro diffusion precipitin tests for enteroviruses and influenza B virus

Middleton, G. K., Jr. (Bowman Gray School of Medicine, Winston-Salem, N.C.), H. G. Cramblett, H. L. Moffet, J. P. Black, and H. Shulenberger. Micro diffusion precipitin tests for enteroviruses and influenza B virus. J. Bacteriol. 87:1171-1176. 1964.-A simple micro precipitin gel diffusion test has been adapted to the study of viral antigens. As far as is known from a review of recent literature, this is the first use of the ECHO viruses in precipitin tests and the first attempt to demonstrate by the gel diffusion technique precipitins in a patient's serum after natural virus infection rather than artificial immunization. The principal value of this technique in virology is the rapid identification or qualitative analysis of viral antigen preparations by use of pooled or specific hyperimmune sera. Virus concentrations of 10(7)tcid(50) per 0.1 ml are required for reliable results, but only 0.015 ml of serum is necessary for each test. Virus-serum precipitin reactions were type-specific except for reciprocal precipitation of ECHO 1 and ECHO 8 by their hyperimmune sera. No viral antigens have been found common to two or more virus types among those tested. Precipitins for viral antigens occur frequently in serum of patients after a viral infection and are readily detected by micro precipitin gel diffusion tests. However, this precipitin test remains at present a tool for virus and antigen identification and offers an approach for research appraisal of host response to infections.

THERMAL INACTIVATION OF POLIOVIRUS UNDER ANAEROBIC CONDITIONS

Wallis, Craig (Baylor University, Houston, Texas) and Joseph L. Melnick . Thermal inactivation of poliovirus under anaerobic conditions. J. Bacteriol. 84: 389–392. 1962.—Of the six strains of poliovirus tested (three antigenic types), none was stabilized at 50 C under anaerobic conditions. The previously reported stabilization of polioviruses using thioglycolate had been attributed to anaerobic conditions. However, the sparing effect attained with high concentrations of thioglycolate was achieved as readily with other organic salts (benzoate, acetate) which could not be attributed to the anaerobic state. The viruses failed to be stabilized when low oxygen tension was obtained by dilute thioglycolate, l -cysteine, and nitrogen.