Sensitivity to ultraviolet radiation of Lassa, vaccinia, and Ebola viruses dried on surfaces.

Germicidal UV (also known as UVC) provides a means to decontaminate infected environments as well as a measure of viral sensitivity to sunlight. The present study determined UVC inactivation slopes (and derived D(37) values) of viruses dried onto nonporous (glass) surfaces. The data obtained indicate that the UV resistance of Lassa virus is higher than that of Ebola virus. The UV sensitivity of vaccinia virus (a surrogate for variola virus) appeared intermediate between that of the two virulent viruses studied. In addition, the three viruses dried on surfaces showed a relatively small but significant population of virions (from 3 to 10 % of virus in the inoculum) that appeared substantially more protected by their environment from the effect of UV than the majority of virions tested. The findings reported in this study should assist in estimating the threat posed by the persistence of virus in environments contaminated during epidemics or after an accidental or intentional release.

[The production of antibody-producing hybridomas to the Lassa virus]. / Poluchenie antiteloprodutsiruiushchikh gibridom k virusu Lassa.

The work deals with obtaining hybrid cell lines producing monoclonal antibodies to Lassa arenavirus. To obtain preparations for the screening of hybridomas by indirect immunofluorescence techniques, the dynamics of the accumulation of Lassa virus antigen in cell cultures Vero and 4647 was studied. The maximum accumulation of the virus antigen in Vero cells was shown to occur on day 3 after inoculation with a dose of 1.0 PFU/ml. The influence of different doses of gamma radiation on the infectious and antigenic activity of the virus was studied. The expediency of using a dose of 20.0 kGy for the irradiation of the virus was shown. The optimum schedule for the immunization of BALB/c mice was worked out, which made it possible to obtain activated mouse spleen cells used for the construction of hybridomas. The capacity of hybrid cells, injected into syngeneic mice, for the generation of tumors was shown.

[The cultivation and physicochemical properties of the Josiah strain of the Lassa virus]. / Kul'tivirovanie i fiziko-khimicheskie svoistva virusa Lassa shtamm Dzhoziia.

Data on the stability of Lassa virus, Josia strain, isolated from man to the effect of physicochemical factors (heating at 50 degrees C, solutions of urea and formalin of various concentrations, UV irradiation) as well as on the time course of this strain reproduction in cell lines of different origins are presented. Recommendations for lowering of reactogenicity of the virus-containing material are given. The experimental results must be taken into consideration in the development and manufacture of diagnostic and therapeutic-prophylactic preparations for Lassa fever.

[Effect of immunosuppression on the development and outcome of an acute infection in mice caused by administration of the Lassa virus]. / Vliianie immunosupressii na razvitie i iskhod ostroi infektsii, vyzyvaemoi u myshei vvedeniem virusa Lassa.

In experimental infection of mice with Lassa virus, the infectious virus could be detected in all the organs and brain tissues tested. Histopathological lesions were demonstrated in cerebral and spinal cord tissues only. Roentgen irradiation in a dose of 500 R and cyclophosphamide protected mice against a lethal Lassa virus dose. Cyclosporin A in various doses exerted no effect on the outcome of the acute infection. The adoptive transfer of splenocytes from mouse donors inoculated intraperitoneally prevented the development of lethal disease symptoms and death of mice-recipients. It is suggested that immunocompetent cells are involved in the development and outcome of experimental infection of mice with Lassa virus.

[Electron microscopic study of Lassa virus]. / Elektronno-mikroskopicheskoe izuchenie virusa Lassa.

Ultrafiltration through hollow fibrous filters followed by purification in interrupted and linear urografin gradients yielded a Lassa virus suspension of high concentration. The use of gamma-irradiation for inactivation of the frozen virus suspension (-70 degrees C) caused no apparent structural changes of virions and made it possible to examine Lassa virus in electron microscope by negative staining. The observed virus particles in their morphology and sizes did not differ from previously described particles of other members of the Arenaviridae family. In ultrathin sections of Lassa virus-infected Vero cells, atypical virions were sometimes visible alongside with typical particles. Within one type of such particles no ribosome-like granules could be detected. Such "hollow" particles may possibly be defective virions. Another kind of atypical particles contained homogeneous electron-dense core and resembled mycoplasma. Of greatest interest are the particles with heterogeneous core in which "sandy" granules can be distinguished. The presence of greater amounts of uranophilic material than usually may be explained by getting into the virion in the process of its formation of a greater amount of genetic material than that present in typical virions.

Physicochemical inactivation of Lassa, Ebola, and Marburg viruses and effect on clinical laboratory analyses.

Clinical specimens from patients infected with Lassa, Ebola, or Marburg virus may present a serious biohazard to laboratory workers. We have examined the effects of heat, alteration of pH, and gamma radiation on these viruses in human blood and on the electrolytes, enzymes, and coagulation factors measured in laboratory tests that are important in the care of an infected patient. Heating serum at 60 degrees C for 1 h reduced high titers of these viruses to noninfectious levels without altering the serum levels of glucose, blood urea nitrogen, and electrolytes. Dilution of blood in 3% acetic acid, diluent for a leukocyte count, inactivated all of these viruses. All of the methods tested for viral inactivation markedly altered certain serum proteins, making these methods unsuitable for samples that are to be tested for certain enzyme levels and coagulation factors.

Inactivation of Lassa, Marburg, and Ebola viruses by gamma irradiation.

Because of the cumbersome conditions experienced in a maximum containment laboratory, methods for inactivating highly pathogenic viruses were investigated. The infectivity of Lassa, Marburg, and Ebola viruses was inactivated without altering the immunological activity after radiation with Co60 gamma rays. At 4 degrees C, Lassa virus was the most difficult to inactivate with a rate of 5.3 X 10(-6) log 50% tissue culture infective dose per rad of CO60 radiation, as compared with 6.8 X 10(-6) log 50% tissue culture infective dose per rad for Ebola virus and 8.4 X 10(-6) log 50% tissue culture infective dose per rad for Marburg virus. Experimental inactivation curves, as well as curves giving the total radiation needed to inactivate a given concentration of any of the three viruses, are presented. We found this method of inactivation to be superior to UV light or beta-propiolactone inactivation and now routinely use it for preparation of material for protein-chemistry studies or for preparation of immunological reagents.