Ectromelia virus: A species of ORTHOPOXVIRUS infecting mice and causing a disease that involves internal organs and produces characteristic skin lesions.Ectromelia, Infectious: A viral infection of mice, causing edema and necrosis followed by limb loss.Poxviridae Infections: Virus diseases caused by the POXVIRIDAE.Orthopoxvirus: A genus of the family POXVIRIDAE, subfamily CHORDOPOXVIRINAE, comprising many species infecting mammals. Viruses of this genus cause generalized infections and a rash in some hosts. The type species is VACCINIA VIRUS.Cowpox virus: A species of ORTHOPOXVIRUS that is the etiologic agent of COWPOX. It is closely related to but antigenically different from VACCINIA VIRUS.Poxviridae: A family of double-stranded DNA viruses infecting mammals (including humans), birds and insects. There are two subfamilies: CHORDOPOXVIRINAE, poxviruses of vertebrates, and ENTOMOPOXVIRINAE, poxviruses of insects.Variola virus: A species of ORTHOPOXVIRUS causing infections in humans. No infections have been reported since 1977 and the virus is now believed to be virtually extinct.Ectromelia: Gross hypo- or aplasia of one or more long bones of one or more limbs. The concept includes amelia, hemimelia, phocomelia, and sirenomelia.Vaccinia virus: The type species of ORTHOPOXVIRUS, related to COWPOX VIRUS, but whose true origin is unknown. It has been used as a live vaccine against SMALLPOX. It is also used as a vector for inserting foreign DNA into animals. Rabbitpox virus is a subspecies of VACCINIA VIRUS.Complement Inactivating Agents: Compounds that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host.Vaccinia: The cutaneous and occasional systemic reactions associated with vaccination using smallpox (variola) vaccine.Inclusion Bodies, Viral: An area showing altered staining behavior in the nucleus or cytoplasm of a virus-infected cell. Some inclusion bodies represent "virus factories" in which viral nucleic acid or protein is being synthesized; others are merely artifacts of fixation and staining. One example, Negri bodies, are found in the cytoplasm or processes of nerve cells in animals that have died from rabies.Viral Proteins: Proteins found in any species of virus.Spleen: An encapsulated lymphatic organ through which venous blood filters.
EctromeliaTanapox: (ILDS B08.830) |OrthopoxvirusBrighton Sailing ClubAlastrimPhocomeliaGeneralized vaccinia: Generalized vaccinia is a cutaneous condition that occurs 6-9 days after vaccination, characterized by a generalized eruption of skin lesions, and caused by the vaccinia virus.Progressive vaccinia: Progressive vaccinia (also known as "Vaccinia gangrenosum," and "Vaccinia necrosum") is a rare cutaneous condition caused by the vaccinia virus, characterized by painless, but progressive, necrosis and ulceration.Periarteriolar lymphoid sheaths: Periarteriolar lymphoid sheaths (or periarterial lymphatic sheaths, or PALS) are a portion of the white pulp of the spleen. They are populated largely by T cells and surround central arteries within the spleen; the PALS T-cells are presented with blood borne antigens via myeloid dendritic cells.
(1/85) Granzymes are the essential downstream effector molecules for the control of primary virus infections by cytolytic leukocytes.
Analysis of perforin-deficient mice has identified the cytolytic pathway and perforin as the preeminent effector molecule in T cell-mediated control of virus infections. In this paper, we show that mice lacking both granzyme A (gzmA) and granzyme B (gzmB), which are, beside perforin, key constituents of cytolytic vesicles, are as incapable as are perforin-deficient mice of controlling primary infections by the natural mouse pathogen ectromelia, a poxvirus. Death of gzmAxgzmB double knockout mice occurred in a dose-dependent manner, despite the expression of functionally active perforin and the absence of an intrinsic defect to generate splenic cytolytic T cells. These results establish that both gzmA and gzmB are indispensable effector molecules acting in concert with perforin in granule exocytosis-mediated host defense against natural viral pathogens. (+info)
(2/85) Expression of mouse interleukin-4 by a recombinant ectromelia virus suppresses cytolytic lymphocyte responses and overcomes genetic resistance to mousepox.
Genetic resistance to clinical mousepox (ectromelia virus) varies among inbred laboratory mice and is characterized by an effective natural killer (NK) response and the early onset of a strong CD8(+) cytotoxic T-lymphocyte (CTL) response in resistant mice. We have investigated the influence of virus-expressed mouse interleukin-4 (IL-4) on the cell-mediated response during infection. It was observed that expression of IL-4 by a thymidine kinase-positive ectromelia virus suppressed cytolytic responses of NK and CTL and the expression of gamma interferon by the latter. Genetically resistant mice infected with the IL-4-expressing virus developed symptoms of acute mousepox accompanied by high mortality, similar to the disease seen when genetically sensitive mice are infected with the virulent Moscow strain. Strikingly, infection of recently immunized genetically resistant mice with the virus expressing IL-4 also resulted in significant mortality due to fulminant mousepox. These data therefore suggest that virus-encoded IL-4 not only suppresses primary antiviral cell-mediated immune responses but also can inhibit the expression of immune memory responses. (+info)
(3/85) Enhanced resistance in STAT6-deficient mice to infection with ectromelia virus.
We inoculated BALB/c mice deficient in STAT6 (STAT6(-/-)) and their wild-type (wt) littermates (STAT6(+/+)) with the natural mouse pathogen, ectromelia virus (EV). STAT6(-/-) mice exhibited increased resistance to generalized infection with EV when compared with STAT6(+/+) mice. In the spleens and lymph nodes of STAT6(-/-) mice, T helper 1 (Th1) cytokines were induced at earlier time points and at higher levels postinfection when compared with those in STAT6(+/+) mice. Elevated levels of NO were evident in plasma and splenocyte cultures of EV-infected STAT6(-/-) mice in comparison with STAT6(+/+) mice. The induction of high levels of Th1 cytokines in the mutant mice correlated with a strong natural killer cell response. We demonstrate in genetically susceptible BALB/c mice that the STAT6 locus is critical for progression of EV infection. Furthermore, in the absence of this transcription factor, the immune system defaults toward a protective Th1-like response, conferring pronounced resistance to EV infection and disease progression. (+info)
(4/85) Serial backcross analysis of genetic resistance to mousepox, using marker loci for Rmp-2 and Rmp-3.
At least three genes from C57BL/6 mice that mediate dominant resistance to lethal mousepox were isolated and transferred onto a susceptible DBA/2 background. Three [(C57BL/6 x DBA/2)F1 x DBA/2] male mice that survived infection were selected as founders on the basis of different complements of marker loci for two resistance genes, Rmp-2r (Hc1) and Rmp-3r (H-2Db). They were crossed with DBA/2 mice, male progeny were infected with ectromelia virus, and the cycle was repeated with surviving male progeny through seven backcross generations. Two founders carried a marker locus for Rmp-2r or Rmp-3r, and the third carried neither marker locus. Resistance pedigrees were analyzed for passage of marker loci. From the three founders, resistance was passaged through multiple generations, producing backcross lines with intermediate-male-resistance phenotypes (20% resistant). Females of backcross lines with intermediate male resistance had high resistance (> 50%). High-resistance backcross lines (40% male resistance) also developed from the founders that carried marker loci for Rmp-2r and Rmp-3r, and marker loci were passaged through all generations of high resistance but not intermediate-resistance lines. About one-third of all resistant mice in high-resistance lines sired by mice that carried marker loci for Rmp-2r and Rmp-3r did not carry the respective marker locus. In lines that carried Rmp-2r, this was apparently not the result of recombination between Rmp-2r and Hc1, because Rmp-2 was not in the predicted location on chromosome 2 and because mice that did not inherit Hc1 transmitted significantly less male resistance than Hc1-positive mice, although female resistance remained high. These results confirmed that C57BL/6 mice have redundant resistance mechanisms, two of which are controlled at least in part by Rmp-2r and Rmp-3r, and provided evidence for a fourth resistance gene, herein presumptively named Rmp-4, which protects females more than males and which may be epistatic to Rmp-2. (+info)
(5/85) The genomic sequence of ectromelia virus, the causative agent of mousepox.
Ectromelia virus is the causative agent of mousepox, an acute exanthematous disease of mouse colonies in Europe, Japan, China, and the U.S. The Moscow, Hampstead, and NIH79 strains are the most thoroughly studied with the Moscow strain being the most infectious and virulent for the mouse. In the late 1940s mousepox was proposed as a model for the study of the pathogenesis of smallpox and generalized vaccinia in humans. Studies in the last five decades from a succession of investigators have resulted in a detailed description of the virologic and pathologic disease course in genetically susceptible and resistant inbred and out-bred mice. We report the DNA sequence of the left-hand end, the predicted right-hand terminal repeat, and central regions of the genome of the Moscow strain of ectromelia virus (approximately 177,500 bp), which together with the previously sequenced right-hand end, yields a genome of 209,771 bp. We identified 175 potential genes specifying proteins of between 53 and 1924 amino acids, and 29 regions containing sequences related to genes predicted in other poxviruses, but unlikely to encode for functional proteins in ectromelia virus. The translated protein sequences were compared with the protein database for structure/function relationships, and these analyses were used to investigate poxvirus evolution and to attempt to explain at the cellular and molecular level the well-characterized features of the ectromelia virus natural life cycle. (+info)
(6/85) Efficacy of oral active ether lipid analogs of cidofovir in a lethal mousepox model.
Cidofovir (CDV) is a highly effective inhibitor of orthopoxvirus replication and may be used intravenously to treat smallpox or complications arising from the smallpox vaccine under an investigational new drug application (IND). However, CDV is absorbed poorly following oral administration and is inactive orally. To improve the bioavailability of CDV, others synthesized alkoxyalkanol esters of CDV and observed >100-fold more activity than unmodified CDV against cowpox, vaccinia, and variola virus (VARV) replication. These ether lipid analogs of CDV have high oral bioavailability in mice. In this study, we compared the oral activity of CDV with the hexadecyloxypropyl (HDP)-, octadecyloxyethyl-, oleyloxypropyl-, and oleyloxyethyl-esters of CDV in a lethal, aerosol ectromelia virus (ECTV) challenge model in A/NCR mice. Octadecyloxyethyl-CDV appeared to be the most potent CDV analog as a dose regimen of 5 mg/kg started 4 h following challenge completely blocked virus replication in spleen and liver, and protected 100% of A/NCR mice, although oral, unmodified CDV was inactive. These results suggest that this family of compounds deserves further evaluation as poxvirus antiviral. (+info)
(7/85) Protective effect of exogenous recombinant mouse interferon-gamma and tumour necrosis factor-alpha on ectromelia virus infection in susceptible BALB/c mice.
The resistance to mousepox is correlated with the production of type I cytokines: interleukin (IL)-2, IL-12, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha. We intend to describe the modulation of generalized ectromelia virus (EV) infection with exogenous administration of mrIFN-gamma and mrTNF-alpha separately and in combination using susceptible BALB/c mice. The treatment schemes presented resulted in the localization of the generalized EV infection and its development into non-fatal sloughing of the infected limb. This was accompanied by low virus titres in the treated mice due to control of systemic virus replication and virus clearance. The balance of type I versus type II cytokines was dominated by a type I response in the treated groups. The group treated with the combination of IFN-gamma and TNF-alpha exhibited the best survival with Th1-dominant (IFN-gamma and IL-12) cytokine profiles, whereas the TNF-alpha-treated group of mice was less successful in clearance of virus and demonstrated the lowest survival rate. The successful cytokine treatment schemes in this orthopoxvirus model system may have important implications in the treatment of viral diseases in humans and, in particular, of variola virus infection. (+info)
(8/85) Polarized type 1 cytokine response and cell-mediated immunity determine genetic resistance to mousepox.
Ectromelia virus (ECTV), a natural mouse pathogen and an orthopoxvirus, has been used to investigate the correlation between polarized type 1 or type 2 immune responses and resistance to disease in poxvirus infections by using well defined resistant and susceptible mouse strains. Our data show that distinct differences exist in the cytokine profiles expressed in resistant and susceptible mice infected with ECTV. Resistant C57BL/6 mice generate a type 1 cytokine response [IFN-gamma, IL-2, and tumor necrosis factor (TNF)], within the first few days of infection, which is associated with strong cytotoxic T lymphocyte response (CTL) and recovery from ECTV infection. Susceptible strains of mice (BALB/c and A/J) on the other hand generate a type 2 cytokine response (IL-4 but little or no IFN-gamma and IL-2), which is associated with a weak or an absent CTL response, resulting in uncontrolled virus replication and death. Although deletion of IL-4 function alone did not change the outcome of infection in susceptible mice, the loss of IFN-gamma function in resistant mice abrogated natural killer (NK) cell and CTL effector functions resulting in fulminant disease and 100% mortality. Therefore, a clear link exists between the early production of specific type 1 cytokines, in particular, IFN-gamma, the nature of the cellular immune response, and disease outcome in this virus model. This finding in the mousepox model raises the possibility that inappropriate cytokine responses may result in increased susceptibility to smallpox in humans. (+info)