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Biomedical subjects

V Vonka

Publications and source records attributed to V Vonka.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1976

Pathogenicity, immunogenicity and genetic stability in mice and ferrets of a cold inhibitor-resistant mutant of influenza H3N2 virus.

A cold inhibitor-resistant mutant was derived from MRC-2 virus by means of serial passages in the presence of rabbit serum and at gradually decreasing temperatures. This virus, denoted MRC-2 IRc, grew well at both 26 and 37 degree C. The pathogenicity and immunogenicity of the virus was examined in mice and ferrets. No clinical reactions were detected in either species. Both mice and ferrets developed high levels of hemagglutination inhibition and neuraminidase inhibition antibodies. The virus was reisolated from the lungs of intranasally inoculated mice; in ferrets it was recovered from nasal washing and trachea but not from lungs. The properties of the isolated viruses were examined. The viruses reisolated from mice lost their reproductive capacity at 26 degree C and were less resistant to inhibitors than the original virus. The virus isolated from the ferret nose was identical with the original virus, however the tracheal isolate exhibited a certain degree of reversion in both the markers tested.

Animals↗
PubMed1976

Ts mutant of NWS influenza virus: behaviour in vitro and in vivo.

After passaging the NWS influenza virus at increasing temperatures in the hamster embryo fibroblast (HEF) cell line, a temperature-resistant (tr) mutant which grew well at 39 degrees C was isolated. Attempts were made to isolate temperature-sensitive (ts) mutants from the tr virus. After growth in the presence of 5-fluorouracil, 233 virus clones were isolated. Among these only one was incapable of replicating at 39 degrees C. The physiological studies, the shift-up experiment and the electron microscopic investigation suggested that the genetic defect responsible for its ts character influenced a late function of the virus genome. In the lungs of intranasally infected mice, the ts mutant replicated to a lesser extent than the tr virus. During its growth in vivo, the ts virus exhibited a high degree of genetic stability.

Animals↗
PubMed1975

The nature of adenovirus persistence in human adenoid vegetations.

Ninety-seven adenoid vegetations (AV) originating from children aged 2 to 11 years were examined for the presence of adenoviruses. No infectious virus was detected in cell-free homogenates. However, adenovirus was recovered in 30 instances from either fragment or trypsinized cell cultures, or both, of the same tissues. The viruses belonged to types 1, 2, 5 and 6. It was determined by the infectious center assay that the frequency of virus-producing cells in different AV varied between 1 of every 10(5) cells to 1 of every 10(7) cells. Cells reactive with hamster sera containing antibody against the adenovirus early ("T") antigen and with rabbit sera containing antibody against the virus structural antigens were detected in cell smears from trypsinized virus-positive AV. The frequency of positive cells was very low. Nearly 80 per cent of extracts from virus-positive AV contained substances neutralizing the homotypic viruses. Adenovirus-neutralizing substances were only rarely detected in extracts from virus-negative AV. The neutralizing substances could be removed from the extracts by absorbtion with concentrates of the homotypic viruses. Most of the subjects from whom AV containing neutralizing substances were obtained, possessed high levels of homotypic serum antibodies.

Adenoids↗
PubMed1975

Sero-epidemiology of the Epstein-Barr virus: preliminary analysis of an international study - a review.

Samples of Chinese, Indian, African and Caucasian populations, randomly selected in Hong Kong, Singapore, the West Nile District of Uganda, and Nancy, France, were titrated for antibodies to EBV, viral capsid (VCA) and complement-fixing soluble (CF/S) antigens. The age-specific prevalence of infection (as reflected by the proportion of VCA-positive individuals) varied greatly up to the age of 10 years in the four populations studied, the West Nile District of Uganda being outstanding in having an early and massive infection rate. Differences were also observed between ethnic groups in Singapore, where the Chinese appeared to have a delayed infection rate compared to the Indians. Immune response, as measured by the prevalence of CF/S antibodies and by the geometric mean titres (GMT) of VCA and CF/S antibodies, differed significantly between ethnic groups, Ugandan infants (1-3-year age-groups) having a humoral response to VCA and CF/S antigens as high as or higher than that of Burkitt's lymphoma patients, decreasing thereafter to levels lower than those of any other ethnic group observed. Indians in Singapore, known to be at no risk for NPC and BL, exhibited a higher and steadier immune response to VCA in going from young to old age-groups than did the Chinese.

Adolescent↗
PubMedDate not supplied

Small-scale field trial with neuraminidase vaccine.

An inactivated whole-virus vaccine was prepared from the influenza virus recombinant H0N2 and administered to two groups of subjects. A total of 1,200 subjects were vaccinated; comparable groups of subjects served as controls. From a portion of the vaccinees sera were obtained prior to vaccination and three to four weeks afterwards. Serological tests revealed development of or increase in the antibody against H0 in a great majority of the vaccinated subjects and against N2 in slightly more than half of them. Antibody response to H3 antigen was only rarely encountered. Approximately three months after vaccination an influenza epidemic caused by Victoria-like (H3N2) viruses broke out in Czechoslovakia. Numerous influenza cases occurred in the two populations followed. Morbidity was significantly lower among the vaccinated than among the control subjects, indicating a protective effect of the neuraminidase vaccine under field conditions.

Adolescent↗
PubMedDate not supplied

Antibody response in humans after administration of whole-virion and split vaccine prepared from two different influenza A/swine viruses.

Previous findings with sera of several different animal species had indicated a close antigenic similarity between the X53 recombinant (possessing both surface antigens of A/Swine/New Jersey/76 virus) and the A/Swine/Ann Arbor/31 (AA) virus (1). Since the latter virus grows much better in chick embryos than the former, we examined the possibility of using the Ann Arbor virus instead of X53 for inactivated vaccine production. The present paper describes our findings in sera of subjects immunized with either whole-virus or split vaccine prepared from AA virus.

Adolescent↗