[Epitope specificity and protective activity of monoclonal antibodies to Venezuelan equine encephalomyelitis virus].

Epitope specificity and protective activity of 5 types of monoclonal antibodies (MAB) to strain TM-14 of Venezuelan equine encephalomyelitis (VEE) virus were studied. The competing VEE A4 and VEE B5 MAB were shown to recognize the conformation-dependent epitope of glycoprotein E2 third site and to possess an extremely high protective activity. VEE C6 MAB were active in all the studied biological tests (hemagglutination inhibition, neutralization tests, passive defence) and were directed to glycoprotein E2 site six.

[The biological and immunochemical properties of monoclonal antibodies to the Venezuelan equine encephalomyelitis virus].

Five strains of hybrid cells producing highly active monoclonal antibodies (MCA) to Venezuelan equine encephalomyelitis (VEE) virus were generated. VEEC6 MCA had high virus-neutralizing and hemagglutinating activities attesting to their direction to the "critical" site of E2 glycoprotein. MCA VEEA5 directed to the same glycoprotein did not overlap spatially with the previous one.

[Inactivation of alpha VEE virus using a high intensity laser with UV-radiation].

Inactivation of VEE virus with laser UV impulses of nano- and picosecond duration was investigated. It has been shown that in both cases there is a decrease of the inactivation cross-section with the rise of irradiation intensity. It points to the fact that the major lethal photoproduct in VEE is formed by a single-quantum mechanism.

[Ts mutants of the Eastern equine encephalomyelitis virus. Their generation, isolation and preliminary characterization].

Chick embryo fibroblast cultures of the C/O phenotype (leukemia--free) infected with eastern equine encephalomyelitis (EEE) virus were incubated in the presence of 15 micrograms/ml N-methyl-N-nitro-N-nitrosoguanidine in the culture medium. Seven (5%) temperature-sensitive mutants were isolated from cell homogenates only in those cases where cell cultures before infection had been treated with actinomycin D. The recovered ts mutants are characterized by the marked ts- phenotype and genetic stability.

[Effect of the method of passage on the biological properties of attenuated alphavirus strains].

Experiments with attenuated clones of Venezuelan equine encephalomyelitis virus and Eastern equine encephalomyelitis virus were carried out to study the regularities in changes of biological properties of virus in "undiluted" passages and in passages by subcultivation of small doses. In the latter case the biological activity of the virus remained at the initial low level but in "undiluted" passages it increased, due to accumulation in the population of clones with altered plaque phenotype and increased reproductive potential. In a number of cases this virus had a higher level of residual virulence than the original one.

[Biological and genetic properties of a polyploid-forming mutant of the Venezuelan equine encephalomyelitis virus].

Some genetic and biological properties of the multiploid -forming mutant of Venezuelan equine encephalomyelitis virus as well as of standard and multiploid virions isolated from its population were analysed. The mutant steadily retained the capacity for formation of multiploid virions comprising up to 20% of the population both in passages in CEF culture and in the progeny of multiploid and standard virions. Owing to this, the concentration of multiploid virions in the population of this mutant remains at a constant level.

[Induction of alphavirus ts-mutations by N-methyl-N-nitro-N-nitrosoguanidine added to the replicating virus].

The possibility of producing ts mutants of Sindbis and eastern equine encephalomyelitis (EEE) virus by treatment of replicating virus with N-methyl-N-nitro-N-nitrosoguanidine was studied. N-methyl-N-nitro-N-nitrosoguanidine added in a concentration of 20 micrograms/ml to chick fibroblast cultures infected with Sindbis virus for 4 hours was shown to induce ts mutations in the virus. Under similar conditions no ts mutants of EEE virus could be obtained.

[Variability of attenuated alphavirus strains in virion aggregate infection].

A natural process of infection with multiploid virions was stimulated and the genetic effects occurring in this infection were studied in experiments with homogeneous attenuated strain of Venezuelan equine encephalomyelitis virus producing the smallest plaques. The process of infection with multiploid virions was reproduced by infecting the cells with artificially obtained aggregates. Under these conditions, small- and large-plaque virus was produced which in some cases had a higher virulence than the parental strain.

[Molecular biology characteristics of an attenuated mutant of the Eastern equine encephalomyelitis virus].

The main molecular biology parameters of an attenuated mutant DMS-20/6 of eastern equine encephalomyelitis virus derived by treatment with dimethylsulphate of the wild type virus (strain No. 627) were determined. The sedimentation coefficient of sucrose density gradient purified and concentrated virus was 280 S, the buoyant density of virions in sucrose density gradient was 1.

[Comparative study of variants of the Venezuelan equine encephalomyelitis virus isolated from chronically infected cells by transfection in different cells].

Comparative data with regard to the properties of Venezuelan equine encephalomyelitis (VEE) virus isolated from HeLa carrier cultures by transfection in different cell cultures have been obtained. Introduction of DNA extracted from the carrier cultures into BHK-21 cell cultures resulted in production of an actively multiplying medium-plaque virus, and parallel addition of the same DNA preparations in chick fibroblast or monkey kidney cultures led to production of small-plaque virus with a low reproduction potential. The virus produced by transfection of BHK-21 cells differed from that produced in chick fibroblast and monkey kidney cultures in electrophoretic mobility of virion envelope proteins.

[Genetic function of the multiploid virions of alphaviruses].

The natural process of infection with multiploid virions of alphaviruses was modeled by inoculation of cells with artificially obtained aggregates. After infection with the aggregates the progeny of attenuated clones of Venezuelan equine encephalomyelitis virus was found to have some new properties. The virus produced larger plaques and had higher reproduction activity.

[Morphological study of a mixed alphavirus infection].

In combined paired cultivation of 8 Venezuelan equine encephalomyelitis virus, multiploid virions formed in 17.8% of cases. Five clones with this effect were used in mixed infections with clones of Semliki Forest and Sindbis viruses.

[Multiploid virions of the Venezuelan equine encephalomyelitis virus. Isolation and properties].

Multiploid virions present in the population of multiploid-forming mutant of Venezuelan equine encephalomyelitis (VEE) virus were isolated from preparations of purified and concentrated virus by methods of zonal centrifugation in glycerin density gradient or gel filtration through biogel A-150 m. The portion of multiploid particles in such preparations reached 70%-90%. The isolated multiploid virions retained their morphology, infectivity and hemagglutinating activity.

[Temperature-sensitive mutants of the Venezuelan equine encephalomyelitis virus studied in the complementation test].

Investigation of 15 ts mutants of Venezuelan equine encephalomyelitis (VEE) virus by complementation tests permitted to divide these mutants into 5 complementation groups and to distinguish unclassifiable mutants. Mutants of 2 groups had RNA+/- or RNA- phenotype, i. e.

[Interaction of Venezuelan equine encephalitis virus ts-mutants with cells].

An acute infection of HeLa cell cultures with a ts mutant of Venezuelan equine encephalomyelitis (VEE) virus may have different outcomes ranging from formation of a chronic virus-carrier state to complete elimination of virus from the culture. One of the possibilities is also a short-time carrier state (up to 10 passages) of the virus genome apparently existing in the form of DNA-provirus. The carrier state of virus genetic material in this case is indicated by the infectivity of cellular DNA and the presence in it of sequences homologous to those of virion RNA.

[Morphological data on the reproductive characteristics of the LEIV-108A and LEIV-3306 Uz strains of the Baku virus in chick fibroblast cell culture].

Electron microscopic examinations of chick fibroblast cells 24 hours after inoculation with LEIV-108A and LEIV-3306 Uz strains of Baku virus revealed the following: in the nuclei of the cells infected with the LEIV-108A strain fine granular matrices were found and virus particles were forming at the periphery of the nucleus; in the LEIV-3306Uz-infected cells virus particles were found budding from the plasma membrane of the cell.

[Preparation and characteristics of temperature-sensitive mutants of the Venezuelan equine encephalomyelitis virus].

Fifteen ts mutants of Venezuelan equine encephalomyelitis (VEE) virus have been produced and studied. Two of them were isolated from a virus population grown in the presence of 5-fluorouracyl and 13 from a virus suspension treated with nitrous acid. The efficiency of plating 40 degrees/35 degrees of various mutants varied from 2 X 10(-2) to 6 X 10(-6).

[Study of the morphological aspects of Okhotskiĭ virus replication in a chick fibroblast culture].

Electron microscopic studies of chick embryo fibroblast cells 24 hours after infection with Okhotsky virus revealed changes typical orbivirus infection in the cytoplasm and the nuclei of the cells. The nuclei of the infected cells contained fine-granular matrices with forming virus particles and tubular structures. The cell cytoplasm also contained tubular structures, crystal arrays, fine-granular matrices and virus particles 50-60 nm in diameter.

[Electron microscopic study of chicken fibroblasts infected with the Tyuleniy virus (author's transl)].

Uninfected and Tyuleniy virus-infected chick fibroblast cells were examined. Intracytoplasmic type A particles and immature type C particles of oncornavirus were found in uninfected cells. At 48 and 72 hours after inoculation of the cells with Tyuleniy virus a large number of mature C particles and virions of Tyuleniy virus were found in the cell cytoplasm.