[Evaluation of Ebola virus reproduction in adult ICR white mice].

The investigators studied the ability of adult ICR mice (a laboratory model that was most approximated to the wildtype populations of mice) to maintain Ebola virus (EV) reproduction in the organism. The adult ICR mice inoculated with EV during 23 passages were shown to maintain viral reproduction in the liver. The elevated levels of platelets and the early generation of fibrin and fibrinogen degradation products suggested there were hemostatic changes that did not, however, progress to severe coagulopathy. The animals were in appearance apparently, other than adynamia observed on days 5-7. Thus, the susceptibility of the adult ICR mice to EV is characterized by their ability to maintain virus reproduction in the liver without evident signs of the infection. This pattern of susceptibility in the mice shows a possible role of this rodent species in the transmissive cycle of EV.

[Hematological and immunological parameters during Ebola virus passages in guinea-pigs].

The trend in hematological and immunological parameters during Ebola virus passages in guinea-pigs indicated that pathophysiological changes occurred just during the second passage and further became stronger. The increase of some parameters and their correlation with the occurrence of fatal outcomes allowed the authors to reveal the most significant changes as increased juvenile platelets, whole blood virus appearance, higher echinocytes, a rise in the pro mil of blast cells and megakaryocytes in the bone marrow, and decreased neutrophilic phagocytic activity. Viral acquisition of the properties of lethality to guinea-pigs depends on the fine mechanisms responsible for viral interaction with host cells, which may lead to viral genetic changes during passages.

[Functional activity of peritoneal macrophages in experimental Ebola fever]. / Funktsional'naia aktivnost' peritoneal'nykh makrofagov pri éksperimental'noi likhoradke Ebola.

The phagocytic activity of peritoneal macrophages (a representative of mononuclear phagocytes) as well as the TNF-alpha were studied in animals with different susceptibility to Ebola virus (EV). The results denote the following: 1. Phagocytosis activation by peritoneal macrophages after EV is introduced into the body correlates directly with a susceptibility degree of an animal to EV. 2. The EV content in peritoneal lavage is inversely dependent on a phagocytic activity of peritoneal macrophages. The TNF-alpha activity increases, in blood serum of body susceptible to EV, 500-fold versus the unsusceptible body. Therefore, production of endogenous TNF-alpha can be interpreted as the development of body's immune protection but not as a reason for the development of vascular shock. Presumably, the nonspecific immunity factors condition the EV susceptibility.

[Strain differences related to Ebola virus reproduction in peritoneal macrophages and in aorta explants of guinea pigs]. / Shtammovye razlichiia reproduktsii virusa Ebola v peritoneal'nykh makrofagakh i éksplantatakh aorty morskikh svinok.

Reproduction of the Ebola strains (ES) virus causing lethality in guinea pigs as well as in peritoneal macrophages and aorta explants of animals was investigated in vitro and in vivo; besides, production of interferon-gamma (IFN-gamma) and of tumor necrosis factor-alpha (TNF-alpha) by macrophages and endotheliocytes of guinea pigs was also studied. The interplay "macrophage--ES" by the example of 2 models of susceptibility to ES demonstrates that the ES lethality is not unambiguously related only with a level of virus reproduction in macrophages. The interplay "endotheliocyte--ES" is indicative of that the ES lethality is inversely dependent on a level of production of the IFN-gamma and of TNF-alpha by endotheliocytes. In general, the Eboly fever lethality is not conditioned only by the ability or inability of ES to reproduce in macrophages and endotheliocytes; it also depends on a variety of pathogenetic factors, one of which could be the cytotoxic action of immune complexes shaping in the process of infection progression.

[Effect of an infections dose of the Ebola virus on survivability and immunologic indicators in guinea pigs]. / Vliianie infitsiruiushchikh doz virusa Ebola na vyzhivaemost' i immunologicheskie pokazateli u morskikh svinok.

Analysis of the time course of immunological parameters in intact guinea pigs and animals immunized with inactivated Ebola virus (EV) inoculated with high and low doses of EV strain lethal for guinea pigs showed that high doses induced a higher resistance of the lymphocytic component of immunity than low doses, but activation of the neutrophil phagocytosis was far less expressed after high doses than after low ones. This indicates a qualitative effect of the infective dose of EV on the development of immunological reactions in animals, which modifies the ratio between the lymphocytic and neutrophilic components of immunity.

[Dynamics of immunologic indicators in guinea pigs upon administering various preparations of the Ebola virus]. / Dinamika immunologicheskikh pokazatelei u morskikh svinok pri vvedenii razlichnykh preparatov virusa Ebola]

Immunological and hematological values are analyzed in guinea pigs infected with Ebola virus (EV) strain weakly pathogenic for these animals, inactivated EV, and EV strain adapted to guinea pigs and causing a lethal infection in them. The disease induced by lethal EV differed from that induced by other EV strains. Blastic wave in lymphoid organs in the absence of antibodies to EV detected by enzyme immunoassay, elimination of circulating immune complexes, and appearance of eosinophils in the blood of guinea pigs infected with lethal EV suggest the formation of aggressive immune complexes actively precipitating in tissues and contributing to the development of pathological process typical of Ebola infection.

[Immunobiological properties of vp24 protein of Ebola virus expressed by recombinant vaccinia virus]. / Izuchenie immunobiologicheskikh svoistv belka vp24 virusa Ebola v sostave rekombinantnogo virusa ospovaktsiny.

Immunological and biochemical parameters were studied in guinea pigs immunized with recombinant vaccinia virus containing full-sized gene of Ebola virus vp24 protein and then infected with virulent strain of Ebola virus. The majority of the studied parameters changed similarly in guinea pigs immunized with recombinant vaccinia virus and control guinea pigs inoculated with vaccinia virus both before and after challenge with Ebola virus. However, in animals immunized with recombinant vaccinia virus producing vp24 some biochemical parameters, the mean life span after challenge with Ebola virus, the level of antibodies to the virus, and the phagocytic activity of neutrophils indicated the development of immunological processes other than in controls, namely, the development of immune response to vp24. Although these processes did not eventually lead to the survival of animals, they prolonged the mean life span and resulted in the production of anti-Ebola antibodies, though the level thereof was low. These data demonstrate that recombinant vaccines against Ebola fever are a promising trend of research.

[Changes in certain indicators of hemostasis in rabbits upon administration of Ebola virus preparations]. / Izmeneniia nekotorykh pokazatelei gemostaza u krolikov pri vvedenii preparatov virusa Ebola.

Changes in some parameters of hemostasis in rabbits insusceptible to Ebola virus (EV) in various periods after reinoculations with live and inactivated virus are described. Challenge with both control protein and live and inactivated EV leads to imbalance in the hemostasis system, which is compensated for in the course of follow-up and does not result in clinically manifest disorders of blood clotting. However, the mechanisms of development of the hemostasis imbalance caused by the control protein and virus preparations were different. In the former case no fibrinogen degradation products were detected in the blood serum, whereas in the latter they appeared in the serum after each reinoculation of the virus. This indicates a peculiar effect of EV on hemostasis.

[Study of the phagocytic ability of blood polymorphonuclear leukocytes from rabbits and guinea pigs upon administering Ebola virus]. / Issledovanie fagotsitarnoi sposobnosti polimorfnoiadernykh leikotsitov krovi krolikov i morskikh svinok pri vvedenii virusa Ebola.

Study of the phagocytic activity of polymorphonuclear leukocytes (PMNL) of rabbits resistant to Ebola virus and guinea pigs susceptible to it, repeatedly challenged with live or inactivated Ebola virus in accordance with the immunization protocols, showed a much higher phagocytic activity in animals resistant to the virus than in those susceptible to it. Such behavior of PMNL in guinea pigs may be explained by the absence of the necessary cytokine background activating the neutrophils.