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Biomedical subjects

V Vonka

Publications and source records attributed to V Vonka.

At least 145 records · Page 8Linked to original sources
PubMed1979

A vesicular stomatitis virus (cytomegalovirus) pseudotype and its use in neutralization tests.

Infection with vesicular stomatitis virus (VSV) of human diploid cells preinfected with the AD-169 strain of human cytomegalovirus (CMV) resulted in the formation of a VSV (CMV) pseudotype. Its formation was favored by increasing the bicarbonate content in doubly-infected cultures. The pseudotype was capable of infecting not only human but also rabbit cells. Pseudotype particles formed after infection with the tl 17 mutant of VSV, which carries a thermolabile lesion in its neutralization antigen, were more stable at 45 degrees than the original tl 17 virus. The pseudotype was used in the neutralization test with human sera. All sera positive for CMV antibody in the complement-fixation (CF) test were also reactive in the neutralization test. In addition, numerous sera negative for CMV antibody in the CF test neutralized the pseudotype.

Adult↗
PubMed1979

Effects of cytosine arabinoside on the incorporation of pyrimidine nucleosides into hamster cells transformed by herpes simplex type 1 and type 2 viruses and by human cytomegalovirus.

The incorporation of 3H-thymidine and 3H-deoxycytidine into acidoprecipitable fraction of hamster cells transformed by herpes simplex viruses type 1 and type 2 and of 3H-thymidine into hamster cells transformed by human cytomegalovirus was found to be resistant to the action of cytosine arabinoside. More 3H-thymidine was incorporated into these cells in the presence than in the absence of the drug. Similar stimulaton of 3H-thymidine uptake could be achieved by using unlabelled deoxycytidine instead of cytosine arabinoside. Incorporation of both nucleosides into spontaneously and SV40 transformed cells was efficiently inhibited by the drug.

Animals↗
PubMed1978

Study of Epstein-Barr virus-determined nuclear antigen (EBNA) by chromatography on fixed cell nuclei.

Low ionic strength (50 to 100 mM NaCl) and pH 6.0 were found to be optimal conditions for in vitro conversion of Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA)-negative nuclei to EBNA-positive nuclei by addition of the complement-fixing (CF) antigen extracted from Raji cells. In vitro conversion of nuclei to EBNA-positively was sensitive to DNase but not to RNase treatment. This suggests that nuclear DNA is a specific target substance to which EBV-CF antigen binds. If nuclei were fixed with methanol/acetic acid and subsequently treated with 0.6 M NaCl, EBNA could be eluted from in vitro-converted Ramos nuclei with 0.3 and 0.4 M NaCl. The same conditions were also found to be optimal for the adsorption and elution of EBV-CF antigen in DNA-cellulose chromatography. This indicates that the DNA-binding properties of EBNA antigen can be studied by "chromatography" on fixed nuclei followed by the ACIF test. The obvious advantages of this method over chromatography on DNA-cellulose are its simplicity, the possibility of testing many samples in one experiment and, especially, the use of minimal amounts of material. Significant differences in elution patterns for EBNA were found when nuclei derived from different cell lines (Ramos, Raji, and P3HR-1) were converted in vitro to EBNA-positivity. EBNA is eluted from in vitro-converted nuclei of EBV genome-positive P3HR-1 cells at an almost 0.1 M higher concentration of NaCl than is necesssary for a similar degree of elution from nuclei of EBV genome-negative Ramos cells.

Acetates↗
PubMed1978

Determination of virus-specific antigens in extracts from herpes simplex virus-infected cells by a Cr release inhibition test.

A 51cr release inhibition test (CRIT) was developed for determining herpes simplex virus type 1 antigens in infected cell extracts. Among the factors studied were the optimal concentrations of complement, antibody, and infected target cells. Under standardized conditions, the relationship between antigen content and inhibition of chromium release was linear in a semilogarithmic plot, indicating that the antigen content can be determined from testing two dilutions of a given preparation. Other tests showed that infected cells cryopreserved at -70 degrees C for periods exceeding 3 months can be used in CRIT. Five different batches of infected cell extracts were tested in both CRIT and blocking neutralization tests with comparable results being obtained, suggesting that both tests measure the same activity.

Animals↗
PubMed1978

UV-inactivation of Epstein-Barr virus: differences in early antigen expression in two different non-productive cell lines and influence of caffeine.

Two non-productive Epstein-Barr (EB) virus genome-carrying lymphoblastoid cell lines, namely Raji and NC37, were used for studying the effect of UV irradiation on the ability of P3HR-1 EB virus to induce early antigen (EA) formation. In NC37 cells infected with UV-irradiated virus the formation of EA was delayed; thus the slope of inactivation curve based on the early (24 hr) reading was steeper than that based on the late (72 hr) reading. This was not observed in Raji cells. Caffeine did not influence the percentage of EA positive cells in cultures infected with untreated virus; however, the drug exhibited a marked inhibitory effect on EA production after infection with UV-irradiated virus. The sensitivity to caffeine effect decreased more rapidly with time after infection of Raji than of NC37 cells, suggesting a higher degree of readiness of the host cell repair system in the former than in the latter cells. The caffeine effect was merely directed against the synthesis of R (restricted) component of EA; its influence on the D (diffuse) component formation was negligible.

Antigens, Viral↗
PubMed1977

Epstein-Barr virus antibodies in tonsillar carcinoma patients;.

Sera from 18 tonsillar carcinoma patients and from 18 matched control subjects were examined for the presence of antibodies to viral capsid antigen (VCA), early antigen (EA) and nuclear antigen (EBNA) of EB virus. Antibodies to all three antigens were found more frequently and in significantly higher titres in the tonsillar carcinoma patients than in control subjects.

Aged↗
PubMed1977

Differential expression of D and R components of Epstein-Barr virus early antigen after superinfection and after induction with 5-iododeoxyuridine.

Three non-productive human lymphoblastoid cell lines, NC-37, RAJI and L-1, either superinfected with Epstein-Barr (EB) virus from P3HR-1 cells or treated with 5-iododexyuridine (IUDR), were studied for the development of early antigen (EA) of EB virus. In all three superinfected cell lines, both the restricted (R) and diffuse (D) componets of EA were synthesized, with R-component formation preceding D-component synthesis. After IUDR treatment both components of EA were only formed in RAJI cells, while in NC37 and L-1 cells only the R-component was synthesized.

Antigens, Viral↗
PubMed1977

Production and some properties of neutralizing antigens of herpes simplex virus.

Human diploid cells (LEP) infected with herpes simplex virus (HSV) type 1 were extracted by treatment with Nonidet P-40. The content of antigens reactive with neutralizing antibody in the clarified extract was measured by the blocking test. Influence of various factors on the production of the blocking antigens (BA) was tested. Highest BA titres in LEP cells were achieved at a multiplicity of infection (m.o.i.) of 0.5 TCD50/cell, medium 199 and 22 to 29 hours incubation at 37 degrees C. The use of resting cultures or the presence of cytosine arabinoside in medium reduced the BA production. The activity of BA was reduced by repeated freezing and thawing. The antigen was stable at -20 and -70 degrees C. One hour heating at 60 degrees C resulted in a marked decrease of the antigen titre. BA was resistant to formalin; formalin treatment did not influence its thermosensitivity.

Antigens, Viral↗
PubMed1976

Replication of cytomegalovirus in human epitheloid diploid cell line.

Human diploid BAMB cells with epitheloid morphology, which had been derived from amniotic fluid cells, were capable of supporting the replication of human cytomegalovirus (CMV), without prior treatment of the cells with halogenated pyrimidines. The growth of this virus in BAMB cells and in human diploid fibroblastoid (LEP) cells was compared in parallel tests. Virus replication was slower and less efficient in the former than in the latter system. The most characteristic morphological feature of the CMV-infected BAMB cells was the formation of multinucleated giant cells which frequently contained more than a hundred nuclei; such cells were not seen in LEP cultures. The development of ultrastructural changes was slower in BAMB cells than in LEP cells. The additional most marked differences concerned the place of viral envelopment and the production of cytoplasmic dense bodies. While in LEP cells most nucleocapsids were enveloped from the inner leaflet of the nuclear membrane, in the other system a great majority of the particles acquired their envelopes by budding into vacuoles. Cytoplasmic dense bodies were rare in infected LEP cells but very frequent in BAMB cells. Budding of these structures into vacuoles was also observed.

Cell Line↗
PubMed1976

Thymidine-kinase in cytomegalovirus infected cells.

In human diploid fibroblast LEP cells infected with AD169 strain of human cytomegalovirus (CMV) a sharp increase of cytosol thymidine kinase activity was observed. The properties of the cytosol enzymes from infected and non-infected cells were compared. No significant differences between the enzymes from infected and control cells were observed in substrate specificity, pH dependence, thermostability and relative electrophoretic mobility. Human sera containing high titres of CMV complement-fixing antibodies did not neutralize the enzyme from infected cells. It is concluded from these results that the increase of cytosol thymidinekinase activity in CMV-infected cells was due to an enhancement of cellular thymidine kinase.

Antibodies, Viral↗
PubMed1976

Inhibitory effect of herpes simplex virus type 1 on type 2 virus replication.

Simultaneous infection with herpes simplex type I and type 2 viruses of chick embryo fibroblasts (CEF), which are only permissive for type 2 virus, or rabbit embryo fibroblasts (REF), which are permissive for both virus types, resulted in a marked reduction of type 2 virus production. This effect was dependent on the m.o.i. of type I, being expressed at a high rather than a low m.o.i. The rate of interference decreased with the prolongation of the interval between infection with type 2 and type I viruses. No evidence suggestive of interferon involvement was obtained. Partial inactivation of type 2 virus by ultraviolet irradiation enhanced the inhibitory effect of type I virus. On the other hand, u.v. irradiation of type I virus resulted in a progressive loss of inhibitory activity. The results of the present experiments suggest that a type I genome function is responsible for the interfering effect, and that an early step in the growth of type 2 virus is sensitive to the particular type I virus product involved.

Animals↗
PubMed1976

Ability of temperature-sensitive mutants of the recombinant influenza S/N (H2N1) virus to induce immunity to parental (H0N1 and H2N2) viruses.

The behavior in mice of two thermosensitive (ts) mutants (denoted ts217 and ts700) of the recombinant influenza virus S/N (H2N1) was studied. The parental thermoresistant (tr) virus and both of the mutants were capable of inducing protection against pneumotropic A/Singapore (H2N2) and A/WS (H0N1) challenge viruses. Immunity against the Singapore virus, with which the S/N virus shared the hemagglutinin, developed earlier than against the WS virus, with which the S/N virus shared the neuraminidase. The tr and ts217 viruses were immunologically more active than the ts700 virus. The first two viruses grew markedly better in mouse lungs than did the latter. In the course of ts217 virus replication in vivo, revertants capable of growing at 39 degrees C appeared readily. On the other hand, the ts700 virus proved to be genetically stable. These data seem to provide evidence of a linkage between the stability of the ts phenotype, reproductive capacity in mouse lungs, and immunogenicity in the viruses examined.

Antibodies, Viral↗
PubMed1976

Replicating DNA of herpes simplex virus type 1.

Newly synthesized herpes simplex virus type 1 DNA yielded a heterogeneous sedimentation profile in neutral sucrose gradients, with the main peak occurring at approximately 40S. Components sedimenting slower than virion DNA and a rapidly sedimenting intracellular HSV DNA were also observed. Both the low-molecular weight and the rapidly sedimenting components seemed to be precursors of virion DNA: they almost completely disappeared after a 60-min chase of a 3-min pulse of 3H-thymidine, and were converted into DNA which cosedimented with virion 32P-labeled DNA. However, sedimentation analysis in alkaline sucrose gradients showed that a 60-min period was insufficient for completing the maturation of HSV DNA. Cleavage of parental DNA molecules was observed in neutral sucrose gradients after infection with 3H-thymidine-labeled virions. No evidence for the formation of covalently closed circles during the replication process was obtained. The presence of single-stranded regions in the replicative form of HSV DNA was revealed. Some of the short-pulse (30 sec) labeled HSV DNA (26.1%) was eluted from hydroxylapatite columns with the properties of single-stranded DNA, and 22% of its trichloroacetic acid precipitability was susceptible to single-strand specific S1 nuclease treatment. Pulse-chase experiments indicated that the life-time of this single-stranded component in nascent DNA was probably not longer than 3 min. A small proportion of single-stranded regions, however, survived for longer periods. Almost all of the newly synthesized short-pulse-labeled HSV DNA exhibited an affinity for nitrocellulose filters. This affinity, which was S1 nuclease-sensitive, gradually decreased with prolongation of the time of the chase. After chasing the pulse for 1 h, the attachment of newly synthesized DNA was comparable with virion DNA.

Cell Line↗