Role of interferon regulatory factor 1 in governing Treg depletion, Th1 polarization, inflammasome activation and antitumor efficacy of cyclophosphamide.

The antitumor effectiveness of cyclophosphamide (CTX) and other chemotherapeutics was shown to rely not only on direct cytotoxicity but also on immunogenic tumor cell death and systemic immunomodulatory mechanisms, including regulatory T cell (Treg) depletion, Th1 cell polarization, type I interferon (IFN) and proinflammatory cytokine production. IFN regulatory factor (IRF)-1 is a transcriptional regulator of IFNs and IFN-inducible genes, involved in the control of Th1 and Treg differentiation and in sterile inflammation. Aim of this study was to explore the role of IRF-1 in CTX-induced antitumor effects and related immune activities. This study shows for the first time that IRF-1 is important for the antitumor efficacy of CTX in mice. Moreover, experiments in tumor-bearing C57BL/6 mice showed that Irf1 gene expression in the spleen was transiently increased following CTX administration and correlated with the induction of Th1 cell expansion and of Il12p40 gene expression, which is the main Th1-driving cytokine. At the same time, CTX administration reduced both Foxp3 expression and Treg cell percentages. These effects were abrogated in Irf1-/- mice. Further experiments showed that the gene and/or protein expression of caspase-1, iNOS, IL-1ß, IL-6 and CXCL10 and the levels of nitric oxide were modulated following CTX in an IRF-1-direct- or -indirect-dependent manner, and highlighted the importance of caspase-1 in driving the sterile inflammatory response to CTX. Our data identify IRF-1 as important for the antitumor efficacy of CTX and for the regulation of many immunomodulatory activities of CTX, such as Th1 polarization, Treg depletion and inflammation.

Leukemogenic activity of ether-extracted Rauscher leukemia virus.

After rapid multiple extractions of mouse plasma virus with ether, the aqueous solution contained viral nucleoids that were infectious when inoculated intracranially into newborn BALB/c mice. The infectivity associated with the ether extract was not neutralized by the specific antibody prepared against the whole virus. No intact virus has been seen in these preparations. Treatment with ether completely removed the virus envelope from the particle and produced an apparently homogeneous preparation of viral nucleoids. After the extractions with ether, leukemogenic activity was inactivated by exposure to ribonuclease. The leukemogenic activity of the many-passaged Rauscher virus that has been propagated in tissue culture and that has low infectivity was also retained, and, in two experiments in which material was inoculated intracranially into mice, this activity appeared to have been enhanced by multiple extractions with ether.

[The coleukemogenic action of Bordetella pertussis]. / Koleikomogennoe deistvie kokliushnogo mikroba

Injection of B. pertussis and Rauscher leukemia virus (RLV) in a dose of 4 ID50 to BALB/c mice susceptible to the above virus significantly increases the incidence of leukosis and shortens the average life duration. Injection of B. pertussis to the AKR mice, carriers of the Gross leukosis virus, induces in the first months a greater number of the mice with leukosis and its earlier development.

[Activation of cellular genes as affected by Rauscher leukemia virus]. / Aktivatsiia kletochnykh genov pod vliianiem virusa leikoza Raushera.

The methods of hybridization in solution and blot hybridization have shown that the BALB/c mice spleen cells contain "silent" genes which can amplificate and change their structure following the infection by the Rauscher leukemia virus (RLV). The product of these gene activation is nuclear 35S RNA detectable by the comparative electrophoretic analysis of heterogeneous nuclear RNA of leukemic and normal cells. The expression of complete copies of 35S RNA was observed in nuclei of RLV-infected cells, while in cytoplasm this RNA is represented by incomplete copies. The expression of the sequences homologous to this 35 S RNA in normal mice spleen cells was not detected.

Methylmercury: effect on oncogenic and nononcogenic viruses in mice.

Mice fed methylmercury chloride at dosages of 1 or 10 ppm for 84 days had significantly higher mortality rates when inoculated with encephalomyocarditis virus (nononcogenic) than did nonmethylmercury-treated mice. However, methylmercury fed to mice which were inoculated with Rauscher leukemia virus (oncogenic) did not alter the course of neoplasia. These results demonstrate that prolonged exposure to subclinical concentrations of methylmercury increased susceptibility of a host to a nononcogenic, but not to an oncogenic, virus.

[Induction of leukemia in Rauscher virus-resistant mice by mixed infection with M. arthritidis and Rauscher virus]. / Induktsiia leikoza u myshei, rezistentnykh k virusu Raushera, pri smeshannoi infektsii M. arthritidis i virusom Raushera

At 2-10 months after combined infection with Rauscher virus and M. arthritidis of mice (C57BL/6XA/He)F1 resistant to this virus 14 out of 23 animals developed leukemia morphologically identical to Rauscher leukemia induced in sensitive mice. In control groups of similar animals infected with virus alone or mycoplasma alone not a single case of leukemia developed. As a result of serial intraperitoneal passages in syngeneic mice of cells of leukemias primarily induced by mixed mycoplasma-virus infection 3 transplantable leukemia strains were obtained the cytological picture of which was similar with the original. Upon intraperitoneal and subcutaneous inoculations of leukemic cells generalized leukemia develops as well as a local transplant under the skin or in the abdominal wall at the site of needle puncture.

[Interaction of the Sindbis virus and Rauscher and Friend leukoviruses in primary cultures and subcultures of mouse fibroblasts in the early stages of persistence]. / Vzaimodeistvie virusa Sindbis i leikovirusov Raushera i Frend v pervichnykh kul'turakh i subkul'turakh myshinykh fibroblastov na rannikh étapakh persistentsii.

The interaction between Friend and Raucher leukoviruses and Sindbis togavirus was studied in primary cultures of mouse fibroblasts and subcultures passaged for 77 days. In primary cultures, two types of virus interactions were observed: neutralism and interference. In interference, the release of the infectious Sindbis virus from the cells is blocked. According to electron microscopic observations, its reproduction terminates by formation of virus nucleocapsid. The blocking of the togavirus maturation is stable in primary cultures but reversible upon subcultivation of the cells infected with oncorna- and togavirus. Rauscher and Sindbis viruses are capable of joint persistence in subcultures with a gradual decrease of the infectivity of togavirus and the leukemogenic activity of oncornavirus.

[Change in the nature of the persistence of alpha- and flaviviruses in the body of BALB/c strain mice with a mixed infection with leukovirus]. / Izmenenie kharaktera persistentsii al'fa- i flavivirusov v organizme myshei linii BALB/c pri smeshannoi infektsii s leikovirusom.

The features of pathogenesis of infection caused in adult Balb/c mice intraperitoneally infected with Sindbis virus, virulent or attenuated strains of West Nile (WN) virus, individually or in combination with Rauscher leukemia virus (RLV) were studied. The influence of the latter on the course of togavirus infections was characterized by 3 features: (a) different effects on the visceral and neural phases of the pathogenesis (increased period of viremia and virus reproduction in the viscera did not lead to stimulation of virus reproduction in the CNS); (b) changes in the time of togavirus persistence in the infectious form; (c) the dependence of the observed effect on the togavirus properties.

[Effect of Mycoplasma arthritidis and Rauscher leukosis virus on murine peritoneal macrophages in vitro and in vivo]. / Vliianie Mycoplasma arthritidis i virusa leikoza Raushera na myshinye peritoneal'nye makrofagi in vitro i in vivo.

The interaction of M. arthritidis and Rauscher leukemia virus (RLV) with mouse peritoneal macrophages was studied. When added in vitro, M. arthritidis was shown to exert cytopathic effect on macrophages obtained from normal BALB/c or CBA mice (highly sensitive to RLV) and BAF1 hybrid mice (resistant to RLV) after 4-6 hours of incubation. Macrophages obtained from BALB/c or BAF1 mice infected in vivo with M. arthritidis were functionally defective beginning from day 7. The infection of BALB/c mice with RLV also suppressed the spreading of macrophages, while the infection of RLV-resistant BAF1 mice with the virus did not reduce the spreading and phagocytic activity of peritoneal macrophages on days 1-105. The mixed infection of BALB/c or BAF1 mice with M. arthritidis and RLV markedly reduced the spreading and phagocytic activity of macrophages beginning from day 7. This data is in agreement with earlier findings on the ability of M. arthritidis to stimulate Rauscher leukemia in BAF1 mice. The possible role of M. arthritidis in the mechanism of viral leukemogenesis is discussed.