The inflammatory an immune response to mousepox (infectious ectromelia) virus

The ectromelia virus(EV) has been recognized as the etiological agent of a relatively common infection in laboratory mouse colonies around the world, i.e. Europe (including Poland), U.S.A. and Asia. Due to widespread use of mice in biomedical research, it is important to study the biology of strains characteristic for a given country. This is particularly significant for the diagnosis, prevention and control ectromelia. In severe epizootics, approximately 90% morbidity is observed within colonies and mortality rate exceeding 70% is observed within 4 to 20 days from the appearance of clinical symptoms. The resistance to lethal infection is mouse strain-dependent. Several inbred strains of mice, including C57BL/6 and AKR are resistant to the lethal effects of EV infection, while others, such as A and BALB/c are susceptible. Recent studies indicate that (1) T lymphocytes, natural killer cells and interferon (IFN)-dependent host defenses must operate for the expression of resistance, (2) virus-specific T-cell precursors appear earlier in regional lymph nodes of resistant than susceptible mice, and (3) resistance mechanism are expressed during early stages of infection. Over the past several years, (1) induction of anti-EV cytotoxic CD8+ T lymphocytes responses in vivo in the absence of CD4+ (T helper) cells, (2) importance of some cytokines e.g., IFN-gamma in EV clearance at all stages of infection, and (3) induction of nitric oxide synthase, which is necessary for a substantial antiviral activity of IFN-gamma, have been demonstrated. The effector mechanism by which EV-specific immune cells (T lymphocytes) execute their and inflammatory functions are thought to involve the release of soluble mediators that attract, focus and active cells at the infected sites. It is possible that the skin is the most relevant organ for studying the biology of an EV infection in vivo, yet very little is known concerning EV replication there and the importance of the skin;s innate and immune response for recovery from viral infection. (author)