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|Title:||Abortive Replication of Vaccinia Virus in Activated Rabbit Macrophages|
|Authors:||Niederkorn-Buchmeier, Ann Nancy|
|Keywords:||Medical Sciences;Medical Sciences|
|Abstract:||<p>Macrophages obtained from animals infected with intracellular parasites are activated with respect to their ability to inhibit the replication of the parasite. While normal rabbit macrophages support the replication of vaccinia virus at levels of 2 to 3 logs, macrophages obtained from the peritoneal cavity of rabbits infected 9 to 12 days earlier with vaccinia virus are activated and will not support virus replication. The fate of vaccinia virus in activated rabbit macrophages was studied in order to characterize the abortive infection of the virus within the activated macrophage. Vaccinia virus adsorption was measured using radioactively labelled virus and was similar with both normal and activated macrophages but was lower than, the amount of virus which adsorbed to Vero cells. Maximum adsorption took place during the first 10 minutes of incubation. A significant amount of the vaccinia virus which had adsorbed to the cells eluted from the cells during further incubation. However, the virus elution curves for activated and normal macrophages were similar. Virus uncoating was measured by infecting with ³H thymidine labelled vaccinia virus and then detecting DNase sensitive, TCA soluble counts. Vaccinia virus was able to uncoat to a similar degree in both activated and normal macrophages. Maximum virus uncoating took place one to four hours after adsorption and was approximately 55% of the virus which was adsorbed to the cells. DNA synthesis in vaccinia virus infected cells was detected by pulse labelling with ³H thymidine. A burst of DNA synthesis at 3 to 6 hours after infection took place in both activated and normal macrophages infected with vaccinia virus as well as infected Vero cells. The pattern of vaccinia virus antigen production in activated and normal macrophages was identical as detected by immunofluorescence and immunodiffusion. Autoradiographs of SDS-PAGE gels of lysates of infected cells pulsed with ³H amino acids demonstrated that most of the polypeptides formed within the infected macrophages were identical. However, at least three polypeptides present in the activated macrophages infected with vaccinia virus were absent in the infected normal macrophages and at least one polypeptide present in the virus infected normal macrophages was absent in the virus infected activated macrophages. Pulse chase experiments failed to demonstrate that the differences in polypeptide synthesis in activated and normal macrophages infected with vaccinia virus were due to differences in posttranslational cleavage. Lack of virus particle production in activated rabbit macrophages infected with vaccinia virus was the major detectable defect in the viral replicative cycle. Virus particles were defected by centrifuging on a continuous sucrose gradient cell lysates of virus infected cells labelled with radioactive thymidine or amino acids. No virus particles with the size and density of vaccinia virions were detected in lysates of activated macrophages infected with vaccinia virus. Virus particles were present in normal macrophages and Vero cells after vaccinia virus infection.</p> <p>It appears that the inhibition of production of infectious virus in activated macrophages is mediated by mechanisms other than those induced by interferon. Vaccinia virus DNA and protein were synthesized in activated macrophages. This is in contrast to numerous previous studies which have shown that no vaccinia viral DNA or protein is synthesized in interferon treated cells. Retreatment of normal rabbit macrophages with tissue culture interferon (type I) did not block the replication of vaccinia virus. Pretreatment of normal macrophages with serum from a poly (I)-poly (C) injected rabbit reduced the replication of vaccinia virus but the characteristics of the abortive infection appeared different than in activated macrophages. Therefore, it appears that interferon is not involved in the inhibition of viral replication by activated macrophages.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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