A method for the preparation of purified antigens of coxsackievirus B3 from a large volume of cell culture supernatant

A simple procedure was used for the concentration and partial purification of coxsackievirus B3 (Nancy strain). For a large-scale production of virus. Vero cells grown in roller bottles were used. Virus concentrate from a large volume of cell culture supernatant was prepared by precipitation with 6% (w/w) polyethylene glycol. This crude antigen was further purified by banding in cesium chloride gradient using ultracentrifugation. The infectivity and haemagglutination activity of virus were checked up during the whole procedure and the final recovery of infections virus was about 60%.

Role of phospholipids in BK virus infection and haemagglutination

The role of phospholipids in BK virus infection and haemagglutination was studied by competition binding experiments and by treatment of susceptible cells with phospholipases. Phospholipids extracted from Vero cells and some commercial phospholipids showed an inhibiting activity on both BK virus infectivity and haemagglutination. The treatment of Vero cells with phospholipases affected the binding of BK virus, but the addition of phospholipids to enzyme-treated cells restored their susceptibility to both viral infectivity and haemagglutination.

[The inhibitory effects of catechin derivatives on the activities of human immunodeficiency virus reverse transcriptase and DNA polymerases]

Catechin derivatives including (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC) and green tea extract (GTE) were found to inhibit the activities of cloned human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT), duck hepatitis B virus replication complexes reverse transcriptase (DHBV RCs RT), herpes simplex virus 1 DNA polymerase (HSV-1 DNAP) and cow thymus DNA polymerase alpha (CT DNAP alpha). EGCG and ECG were shown to be very potent inhibitors of HIV-1 RT. According to the IC50 values for HIV-1 RT, these compounds can be ordered as EGCG 0.0066 mumol/L > ECG 0.084 mumol/L > GTE 0.1 microgram/ml > EGC 7.2 mumol/L. DHBV RCs RT was the least sensitive to these compounds. Kinetic study showed that EGCG exerts a mixed inhibition with respect to external template inducer poly (rA).oligo (dT) 12-18 and a noncompetitive inhibition with respect to substrate dTTP for HIV-1 RT. Bovine serum albumin significantly reduced the inhibitory effects of catechin analogues and GTE on HIV-1 RT. In tissue culture GTE inhibited the cytopathic effect of coxsackie B3 virus, but did not inhibit the cytopathic effects of HSV-1, HSV-2, influenza A or influenza B viruses.

Comparison of eight different procedures for harvesting avian reoviruses grown in Vero cells

14 avian reovirus isolates adapted to replicate in an African green monkey (Vero) cell line were studied for the nature of their replication. The growth curves of 5 viruses showed them to be highly cell-associated in Vero cells. Different procedures were examined for releasing the cell-associated virus following propagation in Vero cells, including several freeze-thaw cycles, treatment with sterile distilled deionized water (ddH2O), freon extraction, and trypsin treatment. Treatment of virus infected cultures with ddH2O was the most effective, and trypsin treatment was the least effective procedure for dissociation of virus from cells. Treatment of virus infected cultures with ddH2O is a simple and effective procedure which can be used where large amounts of virus are required for experimental purposes.

Improved isolation of rinderpest virus in transformed bovine T lymphoblast cell lines

Bovine T lymphoblast cell lines transformed by the protozoan Theileria parva were compared with bovine kidney (BK) and Vero cells for their ability to isolate various strains of rinderpest virus from tissues and infected secretions. All of the strains of rinderpest virus that were tested, including attenuated cell-culture, caprinised and lapinised vaccines, and both mild and virulent pathogenic strains, readily induced syncytial cytopathic effect (cpe) in T lymphoblasts. The cpe could often be detected within one day of inoculation of lymphoblasts, whereas it took three to 14 days to appear in Vero and BK cells. Using lymphoblasts it was possible to reisolate rinderpest virus from nine of 42 swabs collected from three cattle experimentally infected with an isolate from a recent outbreak of mild disease whereas the same swabs yielded only one reisolate on BK cells. It was also possible using the lymphoblasts to detect infectious virus in the ocular, nasal and oral secretions of goats and rabbits infected with caprinised and lapinised virus, respectively. Peste des petits ruminants virus appeared to grow as rapidly as rinderpest virus in the lymphoblasts whereas canine distemper virus readily induced cpe on first passage but less readily on subsequent passage. Measles virus induced relatively little cpe when inoculated into lymphoblasts and did not appear to passage in these cells. The lymphoblasts are easy to maintain in culture and since they rapidly recovered 11 isolates from 37 diagnostic samples could prove useful in laboratories carrying out rinderpest diagnosis.

Adaptation of the herpetic virus on human diploid and monkey kidney cells

Viral suspensions of herpetic virus were inoculated on different cell cultures: human diploid cells (HDC) and monkey kidney cells--primary culture and cell line--for adapting the virus on these cells and obtaining several high constant titers. The human diploid cells and the monkey kidney cell line have proved to be the most suitable cells for the virus growth; thus an optimum development of the virus with a high constant titer was obtained starting with the 4th passage (10(5.7)-10(6)CPD/50/ml). The optimum conditions provided for the herpetic virus culture have allowed to obtain a herpetic virus stock used as control preparation for testing the efficacy of the "OFTALMOHERPIN" biological preparation for current use in the prophylaxis and therapy of ocular herpes.

Direct sequence analysis of amplified dengue virus genomic RNA from cultured cells, mosquitoes and mouse brain

A method is described for direct sequence analysis of selected regions of dengue virus genomic RNA in infected tissues. Using specific primers, total high-molecular-weight infected-cell RNA is reverse transcribed to single-stranded (ss) complementary DNA, amplified using the polymerase chain reaction (PCR) and sequenced using ssDNA obtained after lambda exonuclease digestion of one strand of the PCR product (R.G. Higuchi and H. Ochman, Nucleic Acids Research, 17, 5865, 1989). Sequence data for the envelope protein gene of two dengue-3 virus isolates were obtained using RNA from small numbers (10(5)) of cultured mosquito or monkey kidney cells, from one mg of infected mouse brain and from 1/300th of an infected Toxorhynchites amboinensis mosquito. Independent determinations showed that errors occurring during reverse transcription or PCR were not represented to a significant degree in the sequence of the amplified DNA. The method does not depend on extensive passaging of virus or large-scale growth to generate material for sequencing and therefore provides a means of obtaining sequence data for unadapted dengue virus isolates.

[Study of the cultured human endothelial cells infected by epidemic hemorrhagic fever virus]

Virus antigen could be detected in the cytoplasm of infected human endothelial cells (HEC) by immunofluorescent assay (IFA) 2 to 10 days after the inoculation of epidemic hemorrhagic fever virus (EHFV), but no apparent histologic changes could be found by phase contrast light microscopy, as well as no mature virus particles could be detected under the transmission electron microscope. Reinoculation of the freeze-melt supernatant of HEC 8 days after the inoculation of EHFV to EHFV susceptible Vero E-6 cells, viral antigen could be detected in most of these cells and mature EHFV particles or viral inclusion bodies could also be obtained in the cytoplasm under transmission electron microscope. The results show that HEC is a susceptible target cell to EHFV and infection by this virus may not give apparent cytopathogenic effect in HEC.

[Ebola virus reproduction in cell cultures]

Ebola-Zaire virus production in Vero and BGM cells was studied. The CPE developed in both cell cultures. The cell monolayer destruction by 80-90% was seen at a low multiplicity of infection in 7-8 days after virus inoculation. An overlay composition was developed for virus titration using plaque assay. The plaque production was shown to be directly proportional to the virus dose. The curve of Ebola virus production in Vero cell culture fluid was determined. At a multiplicity of infection of 0.01 PFU/cell, the maximum virus titer of 10(6.4) PFU/ml was reached in 7 days postinfection. Specific antisera were generated by inoculation of guinea pigs. Indirect immunofluorescent assay was used for testing of virus-specific antigen and antibody.

Virucidal levels of ozone induce hemolysis and hemoglobin degradation

The animal virus, vesicular stomatitis virus (VSV), and the bacterial virus, phi 6, were inactivated by greater than 4 log10 in response to incubation with 13 to 14 mL of 1.4 mmol per L (65 micrograms/mL) to 1.6 mmol per L (75 micrograms/mL) of overlaid ozone in virus-spiked, dilute, red cell suspensions. Virus inactivation was greatly inhibited when ozone was overlaid in the presence of high-hematocrit red cells or, to a lesser degree, high levels of plasma. At hematocrits at which 5 to 6 log10 of VSV were inactivated, ozone caused 30-percent hemolysis, as measured by the loss of total cellular hemoglobin. Unexpectedly, this level of hemolysis could not be observed in supernatants because of the ozone-induced destruction (bleaching) of extracellular hemoglobin. These results suggest that ozone may have little biological specificity for damaging viruses over red cells.

A 269-amino-acid segment with a pseudo-leucine zipper and a helix-turn-helix motif codes for the sequence-specific DNA-binding domain of herpes simplex virus type 1 origin-binding protein

The UL9 gene of herpes simplex virus (HSV) codes for a DNA-binding protein (OBP) that interacts sequence specifically with the origin of replication. This protein is essential for HSV DNA replication in cultured cells. The UL9 gene was cloned into a plasmid vector downstream of the SP6 RNA polymerase promoter. By using in vitro transcription and translation systems, a full-length OBP was synthesized. This synthetic protein is recognized by an antiserum generated against the C-terminal decapeptide of OBP and is functionally active in binding to OriS sequence specifically. The in vitro-synthesized protein has sequence specificity for binding similar to that found for the in vivo-generated OBP. A total of 14 in-frame deletion and insertion mutants of the UL9 gene were generated and expressed in vitro. Using these deletion mutants, we determined that the 269-amino-acid stretch defined by amino acids 564 to 832 localizes the OriS-specific DNA-binding domain. The N-terminal boundary is between amino acids 565 and 596, while the C terminus lies between amino acids 833 and 805. This segment contains a helix-turn-helix moiety and a pseudo-leucine zipper, neither of which alone can support DNA binding. The other leucine zipper from amino acids 150 to 173 is not required for the in vitro sequence-specific DNA-binding activity of OBP.

Fc receptors do not mediate African swine fever virus replication in macrophages

Titration experiments in swine macrophages have shown that African swine fever virus infectivity was not enhanced in the presence of antiviral antibodies. The early viral protein synthesis and the viral DNA replication in swine macrophages infected with virus-antibody complexes were inhibited in the presence of high doses of uv-inactivated virus, which saturated specific virus receptors, but not when Fc receptors were saturated with antibodies. These results indicate that African swine fever virus does not infect swine macrophages through Fc receptors and that the normal entry pathway through virus receptors is not bypassed by the virus-antibody complexes.

The 5' noncoding region of the type 2 poliovirus vaccine strain contains determinants of attenuation and temperature sensitivity

Intratypic recombinants of P2/Sabin and P2/117, a neurovirulent vaccine revertant, have been generated in vitro using infectious cDNA clones and used to demonstrate that strong determinants of the attenuation and temperature-sensitive phenotypes of P2/Sabin reside in the 5' 492 nucleotides. In this region of the genome the viruses differ only at nucleotides 437 and 481. The ts phenotype associated with the 5' noncoding region is expressed at different temperatures in different cell lines, suggesting an involvement of cellular factors which may be species specific. Suppression of both the ts and attenuation phenotypes correlates with an A-G mutation at nucleotide 481, although other changes are also involved.

Rapid vascular clearance of two strains of Junin virus in Calomys musculinus: selective macrophage clearance

Clearance of Junin (JUN) virus strains with different virulence for Calomys musculinus (Cm) was followed using the Candid #1 virulent and CbaFHA 5069 attenuated strains. In addition, virulent virus albino mice (AM) were included as control host and Venezuelan equine encephalitis (VEE-VI) virus as control virus. The virus inoculum (Vo) and the blood samples (Vt) obtained at different times post-inoculation (p.i.) were titrated on Vero cells and the cleared plaque forming-units (PFU) were calculated as the log Vt/Vo. In Cm both JUN virus strains were cleared rapidly (within 5 min the Candid #1 strain and within 10 min the CbaFHA 5069 strain); meanwhile, VEE-VI virus could be recovered from blood until 30 min p. i. Furthermore, JUN and VEE-VI viruses showed the same behaviour in Am as in Cm. We conclude that the JUN virus strains of different virulence for Cm did not show differences in their clearance from the blood of these animals. Moreover, the rapid clearance observed was independent of the animal host and viral dose.

The expression of the major shed Trypanosoma cruzi antigen results from the developmentally-regulated transcription of a small gene family

To better understand the mechanisms involved in the developmental expression of Trypanosoma cruzi antigens we examined the gene structure and transcription properties of the major shed trypomastigote antigen (SAPA). We report in this paper that SAPA is encoded by a small family of at lest 6 genes which differ mainly in the length of a repeat region made up of tandemly arranged 36-bp repeat units. SAPA genes are located distant from chromosomal telomeres as inferred from their insensitivity to Bal31 nuclease treatment. Furthermore, Northern blot and S1 protection analyses strongly support the fact that most (or all) SAPA genes are transcribed in the infective form of the parasite.

The effect of HSV multiplication rate on antiviral drug efficacy in vitro

HSV-1 multiplication rates have been shown to vary in different tissues and the rate of multiplication may correlate with susceptibility to antiviral chemotherapy. Herpetic stromal keratitis is a necrotizing condition refractive to antiviral therapy and this lack of antiviral efficacy in stromal disease may be the result of very low rates of viral replication in the corneal stromal keratocytes. In this study, we investigated the efficacy of antiviral drugs in an in vitro system in which the virus multiplication rate is slow. In this system, the reduced rate of virus multiplication is achieved by a reduction in the incubation temperature. Vero cells were infected at one of several multiplicities of infection with McKrae strain HSV-1 and incubated for 24, 48, or 72 h at 26 or 36.5 degrees C in the presence or absence of trifluridine (50 micrograms/ml) or acyclovir (20 micrograms/ml). Both drugs suppressed viral replication at 36.5 degrees C. However, under some specific sets of conditions, trifluridine was not effective in suppressing viral replication in cells incubated at 26 degrees C. At this temperature, viral replication and cell metabolism are slowed to a pace which may be similar to that which occurs in corneal stromal keratocytes in vivo. Acyclovir significantly reduced HSV-1 replication under all conditions at 26 degrees C, indicating that the antiviral activity of this compound is effective in cells whose metabolic rate is slow and in which viral replication is taking place slowly.

Evaluation of combined commercial enzyme-linked immunosorbent assay for detection of rota and adenoviruses for automation

219 stools were examined by direct electron microscopy (EM), culture and 'combined' commercial enzyme-linked immunosorbent assay kits (CELISA). The specificity of the combined ELISA for rotavirus was 100% as compared with EM, and 100% for adenovirus when both culture in addition to EM were carried out. ELISA appeared to be more sensitive than EM for both viruses. There was no cross-reaction between the 2 'combined' antisera. This technique may be useful for automation of viral diagnosis with ELISA using a 'panel' of selected viruses for a variety of specimens.

Enterotoxin and cytotoxin production by enteroinvasive Escherichia coli

It has long been suspected that besides their ability to invade enterocytes, enteroinvasive Escherichia coli (EIEC) strains have the ability to elaborate an enterotoxin. We tested 35 EIEC strains for cytotoxins and 9 (1 per serogroup) for enterotoxins. All 35 strains exhibited low levels of Vero cell cytotoxins that are immunologically and genetically distinct from Shiga-like toxin I or II of enterohemorrhagic E. coli. Sterile supernatants and cell lysates of two EIEC strains were tested in rabbit ileal loops, and both stimulated moderate fluid accumulation (circa 0.5 ml/cm) without tissue damage; secretory activity was confirmed in Ussing chambers, where these two strains and the seven others tested significantly increased short circuit current without altering tissue conductance. Curing the 140-MDa invasiveness plasmid from an EIEC strain did not diminish enterotoxin production. Culture in minimal Fe2+ medium is necessary to detect expression of the enterotoxin which is circa 68 to 80 kDa in size and is distinct from the EIEC cytotoxin.

Antiviral potencies of BV-araU and related nucleoside analogues against varicella-zoster virus in different cell lines

1-beta-D-Arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU) and nine other antiherpesviral nucleoside analogues were compared for their potencies against four strains of varicella-zoster virus (VZV) on three different cell lines: HEL cells, Vero cells, and MS cells established from a human malignant schwannoma. In contrast to the activity against herpes simplex virus type 1 previously reported, BV-araU showed extremely marked antiviral activity against VZV even on Vero cells. ED50, 50% plaque reduction dose, of BV-araU for VZV was 0.20-3.1 and 0.14-0.63 ng/ml on Vero cells and on HEL cells, respectively. Potency of BV-araU on MS cells was similar to that on these cell lines. There was not significant variation in anti-VZV activities of other nucleoside analogues on these three different cell lines except a few combinations of VZV strain and test compound.

Inhibitory effect of selected antiviral compounds on arenavirus replication in vitro

Several compounds, belonging to different classes of nucleoside analogues and sulfated polysaccharides, were evaluated for their inhibitory effects on the replication of the arenaviruses Junin and Tacaribe in VERO cells. S-Adenosylhomocysteine (AdoHcy) hydrolase inhibitors [i.e. adenosine dialdehyde, carbocyclic 3-deazaadenosine (C-c3 Ado), neplanocin A, 3-deazaneplanocin A, 9-(2,3-dihydroxypropyl)adenine [(S)-DHPA], (RS)-3-adenin-9-yl-hydroxypropanoic acid isobutyl ester [(RS)-AHPA], the 2',3'-dihydroxycyclopentenyl derivatives of adenine (DHCA) and 3-deazaadenine (DHCDA)] inhibited arenavirus replication within the concentration range of 1-10 micrograms/ml, while not being toxic for cell morphology or cellular DNA synthesis at a concentration of 100-400 micrograms/ml. Based on the ratio of the concentrations required to inhibit cell proliferation and virus replication, only (S)-DHPA, DHCA, C-c3 Ado and adenosine dialdehyde could be considered as truly selective inhibitors. Tubercidin, cyclopentenyl cytosine, pyrazofurin and ribavirin also inhibited viral cytopathogenicity at concentrations that were well below the cytotoxic threshold. Carbodine (cyclopentyl cytosine) also proved to be a potent inhibitor of arenavirus replication, but it was not as selective as cyclopentenyl cytosine. Very potent and selective inhibitors were the sulfated polysaccharides dextran sulfate, lambda-carrageenan, fucoidan, heparin and pentosan polysulfate: they inhibited virus replication at a concentration of 0.1-2.8 micrograms/ml, whereas the compounds were not inhibitory to cell growth even at a concentration of 200 micrograms/ml.

Studies of Clostridium perfringens enterotoxin action at different temperatures demonstrate a correlation between complex formation and cytotoxicity

The cytotoxicity of Clostridium perfringens enterotoxin (CPE) was completely blocked in Vero cells continuously CPE treated at 4 degrees C. [125I]CPE-specific binding to either Vero cells or isolated rabbit intestinal brush border membranes (BBMs) was lower at 4 degrees C than at 24 or 37 degrees C, but reduced enterotoxin binding could not totally explain the loss of cytotoxicity at low temperature. Insertion of enterotoxin into Vero cell membranes or BBMs was temperature independent. However, CPE complex formation (A. P. Wnek and B. A. McClane, Infect. Immun. 57:574-581, 1989) in BBMs and Vero cells was blocked at 4 degrees C. When Vero cells were CPE treated at 4 degrees C, washed to remove unbound toxin, and then shifted to 37 degrees C, complex formation and cytotoxicity were rapidly detected. When CPE binding and complex formation were permitted for 2 min at 37 degrees C, and the Vero cells were then shifted to 4 degrees C, cytotoxicity was detectable at 4 degrees C. These results are consistent with complex formation, rather than complex activity, being the temperature-sensitive step in CPE action which is blocked at 4 degrees C. These studies demonstrate a strong correlation between complex formation and cytotoxicity and are consistent with complex involvement in CPE cytotoxicity. These studies also strongly suggest that CPE insertion precedes both complex formation and induction of small-molecule permeability changes.

Entry and intracellular localization of Brucella spp. in Vero cells: fluorescence and electron microscopy

Vero cells were inoculated with the six species of Brucella (B. abortus, B. melitensis, B. suis, B. neotomae, B. canis, and B. ovis) and examined by fluorescence and electron microscopy. All Brucella spp. were internalized by Vero cells. In all cells except those inoculated with B. canis, the numbers of intracellular brucellae increased with time after inoculation. Intracellular brucellae were first seen within phagosomes and phagolysosomes. Subsequent localization within cisternae of the rough endoplasmic reticulum was seen with all species of Brucella, except B. canis, which was restricted to phagolysosomes. Although rough brucellae were more adherent and entered a greater number of Vero cells, intracellular replication occurred in a larger percentage of cells with smooth rather than with rough brucellae. These results suggest that phagocytosed Brucella spp. are transferred 1) to cisternae of the rough endoplasmic reticulum, where unrestricted bacterial replication takes place; or 2) to phagolysosomes in which Brucella spp. fail to replicate. The various strains of Brucella spp. differ in their ability to induce their own transfer to the rough endoplasmic reticulum.

Different sensitivities of Vero cells from two sources to avian reoviruses

Four strains of avian reovirus were each titrated in two batches of Vero cells (A and B) from different sources and different media recommended for each batch. For each strain, variations in titre were observed under the different cultural conditions. In one case the discrepancy between the titre in A cells with medium recommended for B cells, and B cells with A medium was 2.1 log10. Attention is drawn to the possibility that important differences in sensitivity may exist between batches of Vero cells from different sources and these may be exaggerated by the use of different media.

Persistent measles virus infection in vero and McCoy cell lines

Persistent measles virus infection was established in two cell lines: Vero and McCoy. Vero cells were infected with a virus that had been propagated five times from an undiluted inoculum. Measles virus infection of McCoy cells caused no cytopathic lesions but led to the establishment of persistent infection. Haemadsorption (HA) and immunofluorescence (IF) results indicated that the majority of Vero and McCoy cells carried measles virus antigen localized in the cell membranes. Both cell lines released infectious virus into the medium. In Vero cells, the virus yield diminished with the number of cell passages. Our results suggest that the presence of defective interfering particles in Vero cells and an antiviral factor in the supernatant of McCoy cells contributed to the maintenance of persistent infection.

[Lysosomotropic agents inhibit the penetration of arenaviruses into a culture of BHK-21 and Vero cells]

Lysosomotropic agents (NH4Cl, amantadine, chloroquine, monensin) which prevent acidification of intracellular vacuoles, when introduced into the culture medium before or during inoculation of cells (BHK-21, Vero) with arenaviruses inhibit reproduction of these viruses completely or significantly. Mozambique virus proved to be 10 times more sensitive to the effect of lysosomotropic agents than Pichinde and Lassa viruses. Thus, arenaviruses have a pH-dependent stage at the beginning of the reproduction cycle which is indirectly indicative of their penetration into cells by receptor endocytosis.

Vero cell assay for rapid detection of Clostridium perfringens enterotoxin

A rapid assay which measured the biological activity of Clostridium perfringens enterotoxin was developed. The method involved the rapid killing of Vero cells by enterotoxin produced by C. perfringens grown in Duncan and Strong sporulation medium. Serial dilutions of toxin were added to Vero cells either in suspension or grown as monolayers in wells of a 96-well cell tissue culture cluster plate. Vital staining of Vero cells with neutral red, followed by extraction of the dye, allowed toxin levels to be determined either visually or by optical density measurements with a micro-ELISA M580 computer program. The toxin produced was confirmed as different from the Vero toxin of Escherichia coli and the alpha and theta toxins of C. perfringens.

The entry of African swine fever virus into Vero cells

The entry of African swine fever virus into Vero cells has been investigated by both biochemical and morphological techniques. A quantitative electron microscopy analysis of the early steps of the infection has shown that African swine fever virus enters Vero cells by a receptor-mediated endocytosis mechanism. The internalization of virus particles is a temperature- and energy-dependent process, since it did not take place at 4 degrees or in the presence of NaF and 2,4-dinitrophenol. To determine the involvement of acidic intracellular vacuoles in the virus entry pathway we have tested the effect of lysosomotropic agents in the infection. Chloroquine, dansylcadaverine, amantadine, methylamine, and ammonium chloride inhibited African swine fever virus production in Vero cells. Dansylcadaverine and chloroquine did not inhibit virus adsorption and internalization; however, in the presence of these drugs, virus particles were retained in cytoplasmic vacuoles and early viral RNA and protein synthesis were not detected, indicating that these compounds inhibit an early step in the infectious cycle, probably the uncoating of the virus particle.

Characterization of simian virus 40 receptor moieties on the surfaces of Vero C1008 cells

The nature of the simian virus 40 (SV40) receptor on the surfaces of Vero C1008 cells was investigated by a virus binding assay. The optimum pH for SV40 binding to cell surfaces was found to be at 6.5; however, there was little difference in SV40 binding in the range between pH 4.5 and 7.3. The treatment of cell surfaces with several proteases or with an enzyme specific for O-linked carbohydrates significantly reduced virus binding, suggesting that the receptor for SV40 contains protein and O-linked carbohydrates. Treatment of cell monolayers with octyl glucoside removed virus-binding activity from cell surfaces. Recovery of virus-binding activity by octyl glucoside-treated cells took 2.5 h and was inhibited by cycloheximide or tunicamycin. Four polypeptides with molecular weights of 90,000, 58,000, 54,000, and 30,000 were immunoprecipitated from virus-protein complexes derived from octyl glucoside extract solutions and therefore may be components of the SV40 receptor. Competition experiments between SV40 and polyomavirus revealed that these two viruses do not share the same receptor on Vero C1008 cells.

Naturally occurring canine distemper virus encephalitis: distribution and expression of viral polypeptides in nervous tissues

Formalin-fixed brain tissues from 16 dogs with naturally occurring canine distemper virus (CDV) infection were investigated immunohistochemically by a panel of eight monoclonal antibodies (mAb) directed against four structural CDV proteins. Three mAb recognizing different epitopes of the polymerase (P-1, P-2, P-3) protein, two clones identifying different epitopes on each, the nucleocapsid (NP-1, NP-2) and fusion (F-2, F-3) protein, and one mAb directed against the hemagglutinin (H-2) protein were used. The immunoreactivity of the clones was tested on formalin-fixed, paraffin-embedded Vero cells, which were lytically infected with the neurotropic R252 (R252-CDV) or the Onderstepoort (CDV/Ond) strain of CDV. Clones directed against the H-2 and F-3 epitope recognized CDV/Ond but not R252-CDV. The remaining six clones showed positive immunoreaction with both CDV strains. In vivo expression and distribution of the individual proteins and their epitopes varied substantially between animals and within lesions from the same animal. The NP-2 epitope showed positive immunostaining in all 16 cases. The P-2 epitope was demonstrated in 13, the NP-1 epitope in 12, the P-3 epitope in 9, and the P-1 epitope in 3 brains, but staining was severely reduced compared with the NP-2 epitope and restricted to areas with strong NP-2 expression. Immunostaining was prominent in early and subacute and reduced in chronic demyelinating lesions. mAb directed against the H and F protein showed no immunoreaction in diseased brains.

Characterization of Vero cells

A cell line used in the production of biologicals should be free of infectious agents, and 'described with respect to cytogenetic characteristics and tumorigenicity'. Vero, a continuous cell line derived from a normal African green monkey kidney, was examined for the presence of retroviruses and for tumorigenic potential. We were unable to detect the presence of retroviruses by reverse transcriptase assay, electron microscopy or hybridization of cellular genomic DNA with Mason-Pfizer monkey virus DNA probes. In addition, passage 156 Vero cells did not form progressively growing tumors in nude mice or grow with high efficiency in soft agarose.

Effect of interferon on Vero cells persistently infected with Sendai virus compared to Vero cells persistently infected with SSPE virus

Persistent infections with Sendai and SSPE virus were established in Vero cells. Sequential passages of these cells were monitored by immunofluorescence and for their sensitivity to the antiviral and antiproliferative effects of interferon (IFN). The cells rapidly developed resistance to the antiviral effect of IFN as judged by the inability of IFN to inhibit the replication of exogenous Sindbis virus. This decrease was accompanied by a reduction in the induction of the 2'-5' oligo A synthetase. Both cell lines were resistant to the antiproliferative effect of IFN. A decrease or absence of IFN receptors on the surface of the cells was not found to be the cause of their resistance to IFN.

Construction and characterization of complementary DNA libraries from Vero cells infected with measles virus

Several cDNA libraries have been generated from poly(A)RNA from Vero cells infected for 24 hours with measles virus. Different protocols for cDNA library construction were compared and some critical steps were evaluated. From these libraries, a measles virus specific sequence corresponding to 885 of 1600 nucleotides of the measles virus phosphoprotein gene has been cloned. The phosphoprotein gene accounts for 1% of the total cDNA library after 24 hours of infection at 37 degrees C. The technique of differential colony hybridization was used to analyze the distribution and change of the poly(A)-RNA expression in uninfected Vero cells and in cells infected with measles virus for 24 hours.

HSV-specific IgA from tears blocks virus attachment to the cell membrane

The results of this investigation demonstrate that the IgA antibody in tears inhibits the attachment of herpes simplex virus (HSV) to cells and implicate immunoglobulin A (IgA) isotype antibody in the protection of the ocular surface. Tears were collected from the eyes of infected and uninfected rabbits and tested for the presence of infectious virus, for viral neutralization titer, and in an enzyme-linked immunoassay (ELISA) for antibody to HSV. Neither the tears from the uninfected rabbits nor the tears from the infected rabbits produced viral cytopathic effects on indicator cells in vitro. Tears from uninfected rabbits had no virus neutralization capacity while the tears from infected rabbits had titers of 1:10 to 1:40. Tears collected from HSV-1 infected rabbits, but not uninfected rabbits, had anti-HSV antibody titers as determined by the enzyme-linked immunosorbent assay. Lectin affinity column enrichment of IgA from the tears of uninfected and infected rabbits was examined for the capacity to block viral adsorption to cells using 32P-labeled virus. It was found that exposure of the radio-actively-labeled virus to the purified IgA fraction of tears from infected rabbits reduced the amount of virus binding to Vero cells, whereas the purified IgA obtained from uninfected tears had minimal activity. These results may imply a role for the IgA-containing fraction of tears from HSV-infected animals in preventing viral attachment to cells and suggest that antibody of this isotype plays a protective role at the ocular surface.

Time course of virus-specific macromolecular synthesis during rubella virus infection in Vero cells

Virus specific macromolecular synthesis was studied in Vero cells infected with plaque-purified rubella virus under one-step multiplication conditions. Under these conditions, the rate of virus production was found to increase rapidly until 24 hr postinfection after which time the rate of virus production rose more slowly, reaching a peak level at 48 hr postinfection. This peak rate of virus production was maintained through 72 hr postinfection. A majority of the cells remained alive through 96 hr postinfection, although a 20 to 30% decrease in the number of living cells occurred between 24 and 48 hr postinfection, the time period at which cytopathic effect was first observed. The virus structural proteins were first detected intracellularly at 16 hr postinfection. The rate of synthesis of these proteins was already maximal at 16 hr postinfection and remained constant through 48 hr postinfection. By immunofluorescence, cells expressing virus proteins were first observed at 12 hr postinfection. At 24 hr postinfection, 35 to 50% of the cells in the infected culture were exhibiting immunofluorescence, at 36 hr postinfection, 65 to 90% of the cells were exhibiting immunofluorescence, and at 48 hr postinfection, all of the cells were exhibiting immunofluorescence. The virus genomic and subgenomic RNA species were first detectable by 12 hr postinfection. The rate of synthesis of both of these species peaked at 26 hr postinfection. Rubella virus infection was found to have no effect on total cell RNA synthesis. However, a modest inhibition of total cell protein synthesis which reached 40% by 48 hr postinfection was observed. When Northern analysis of RNA extracted from infected cells was performed, a negative-polarity, virus-specific RNA probe hybridized only to the virus genomic and subgenomic RNA species. A positive-polarity, virus-specific RNA probe hybridized predominantly to a negative-polarity RNA of genome length indicating that both the genomic and subgenomic RNAs are synthesized from a genome-length negative-polarity template. Defective interfering (DI) RNAs were not detected in infected cells through 96 hr postinfection or in cells onto which virus released through 96 hr postinfection was passaged. Thus, the generation of DI particles by rubella virus appears to play no role in the slow, noncytopathic replication of this virus or in the ability of rubella virus-infected cells to survive for extended periods of time.

Maintenance of Toscana virus in Phlebotomus perniciosus by vertical transmission

Toscana virus was maintained in a laboratory colony of Phlebotomus perniciosus by vertical (transovarial) transmission for 13 consecutive generations over a 23-month period. No significant biological changes were noted in the virus after prolonged vertical passage in the sand flies, and transovarially infected females were able to transmit the agent by bite to susceptible animals. Chronic infection of Ph. perniciosus with Toscana virus had no apparent effect on the insects' rate of eclosion. In the absence of selection and with random matings, the virus infection rates in each subsequent generation of the colony decreased, suggesting that Toscana virus cannot be maintained in Ph. perniciosus by transovarial transmission alone. Alternative mechanisms for virus maintenance are discussed.

2'-nor-cGMP, a new cyclic derivative of 2'NDG, inhibits HSV-1 replication in vitro and in the mouse keratitis model

The present study examined the antiherpetic effect of 2'-nor-cGMP, a new cyclic phosphate derivative of 2'NDG, in vitro and in the mouse keratitis model. The 50% inhibitory dose (ID50) was determined with HSV-1 RE strain in Vero cell monolayers for 2'-nor-cGMP (6.9 mcg./ml), 2'NDG (.06 mcg/ml), and trifluridine (F3T) (.72 mcg/ml). Balb C mice underwent bilateral ocular inoculation with HSV-1 RE strain, and then were treated with different therapeutic regimens. The antiviral efficacy of each drug was evaluated by ocular virus titers, clinical grading of epithelial keratitis, and histological evaluation of stromal keratitis. 2'-nor-cGMP was the most effective drug (P = .0001) in reducing ocular viral titers. Both 2'-nor-cGMP and 2'NDG were significantly more effective (P = .0001) than F3T in reducing epithelial keratitis, and as effective as F3T in reducing stromal keratitis.

The antiherpesvirus activity and cytotoxicity of sangivamycin

Sangivamycin, 4-amino-5-carboxamido-7-(beta-D-ribofuranosyl)-pyrrolo[2,3-d]-pyrimidine is a structural analog of adenosine belonging to a group of nucleosides classified as pyrrolopyrimidines. Sangivamycin, an adenosine deaminase resistant analog, was found to inhibit the replication of three strains of herpes simplex virus type 1 (HSV-1) by 50% (ED50) at a concentration approximately equal to the concentration which inhibits cell growth by 50% (LD50). Both Vero cells and rabbit corneal stromal cells in exponential growth were about 10-fold more sensitive to the drug than quiescent cells. The selectivity indices of sangivamycin indicated that the drug was not a highly selective antiviral agent and, therefore, would offer no advantage over drugs currently available for the treatment of herpetic keratitis.

A newly recognized vesiculovirus, Calchaqui virus, and subtypes of Melao and Maguari viruses from Argentina, with serologic evidence for infections of humans and horses

In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesiculovirus as a newly recognized agent for which the name Calchaqui virus is proposed. A limited serosurvey of horses and humans in Santa Fe Province and horses from the adjacent Santiago del Estero Province was performed to determine the prevalence of neutralizing antibody to the subtypes of Melao and Maguari viruses and to Calchaqui virus. The high prevalence of antibodies to these three agents indicates the need for further studies of their disease potential in horses, because they are closely related to several other viruses that are known equine pathogens.

Persistent infection of Vero cells by paramyxoviruses. A morphological and immunoelectron microscopic investigation

Two Vero cell lines persistently infected with canine distemper virus (CDV) or with both CDV and canine parainfluenza (CPI) viruses were investigated. Cells in the CPI-CDV cell line were 90-100% positive for CPI antigen and exhibited 10-80% CPI hemadsorption. Cytoplasmic CDV antigen expressed in both singly and dually infected monolayers varied weekly from 1 to 100%. Numerous cytolytic crises were observed in both cell lines. Cell replication was severely depressed in both cell lines when compared with uninfected Vero cells. Infrequent interfering activity against lytic CPI virus was present in the CPI-CDV cell line but not between lytic CDV and progeny virus from the CDV or the CPI-CDV cell line. Ultrastructurally, Vero cells persistently infected with both paramyxoviruses contained two types of viral nucleocapsids (NC). By immunoelectron microscopy, smooth NC were identified as CPI virus and rough NC were of CDV origin. The viral NC never intermingled but rather were restricted to discrete cytoplasmic areas containing either one type of NC or the other.

The susceptibility of Vero cell cultures for human adenoviruses

Human adenoviruses 1 to 28 were shown to produce a cytopathic effect in Vero cell cultures. Viruses of subgroups III and IV (Ad 1, 2, 5, 6, 12, and 18) were readily passaged in Vero cell cultures and were produced in high amounts. This was also found for Ad 11, 16, and 21, while Ad 3, 4, and 7 showed a lower degree of multiplication and Ad 14 could not be passed serially. For Ad 8, 26, 27, 20, 25, and 28, a multiplication in Vero cells could not be proved, while the remaining serotypes of subgroup II showed a moderate degree of multiplication. The sensitivity of Vero cells to small amounts of virus was lower than that of HeLa cells. No adaption of adenoviruses to Vero cells after 5 Vero passages was observed. Attempts to enhance virus multiplication by coinfection with SV40 failed.