RESUMO
Orf virus causes pustular skin lesions (orf) in sheep, goats and humans. The virus encodes an interleukin-10 (orfvIL-10) that is identical in amino acid composition to ovine IL-10 (ovIL-10) over the C terminal two-thirds of the polypeptide, but not in the N terminal third. The immuno-suppressive and immuno-stimulatory activities of orfvIL-10 and ovIL-10 were compared. Both orfvIL-10 and ovIL-10 inhibited TNF-alpha and IL-8 cytokine production from stimulated ovine macrophages and keratinocytes and IFN-gamma and GM-CSF production from peripheral blood lymphocytes. OrfvIL-10 and ovIL-10 co-stimulated both ovine and murine mast cell proliferation in conjunction with IL-3 (ovine) or IL-4 (murine). Isoleucine at position 87 (Ile(87)) of the mature human IL-10 (huIL-10) has been reported as essential for the immuno-stimulatory activity of huIL-10. In spite of the differences in amino acids within the N-terminal third of orfvIL-10 compared with ovIL-10 and substitution of Ile(87) with Ala(87) in ovIL-10, these variants of ovIL-10 and orfvIL-10 all co-stimulated mast cell proliferation and inhibited macrophage IL-8 production. As ovIL-10 and orfvIL-10 have a similar structure to huIL-10 and conserved receptor-binding residues, it was concluded that Ile(87) is not essential for IL-10 immuno-stimulatory activity. Finally, ovine keratinocytes do not express ovIL-10. This might explain why orf virus has evolved a viral IL-10.
Assuntos
Inflamação/imunologia , Interleucina-10/imunologia , Vírus do Orf/imunologia , Ovinos/imunologia , Sequência de Aminoácidos , Animais , Linhagem Celular , Células Cultivadas , Citocinas/metabolismo , Humanos , Interleucina-10/química , Interleucina-10/genética , Interleucina-10/metabolismo , Queratinócitos/imunologia , Queratinócitos/virologia , Macrófagos Alveolares/imunologia , Macrófagos Alveolares/virologia , Mastócitos/imunologia , Mastócitos/virologia , Camundongos , Dados de Sequência Molecular , Vírus do Orf/genética , Vírus do Orf/patogenicidadeRESUMO
Chlamydophila abortus (C. abortus) is the aetiological agent of ovine enzootic abortion (OEA). The highly elevated expression of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNFalpha) and low-level expression of interferon-gamma (IFNgamma) that are detected in C. abortus-infected placentas have been implicated in the pathogenesis of OEA. Late-term abortions similar to those occurring in sheep have also been observed in mouse models of C. abortus infection. Since mouse studies have contributed significantly to our understanding of the immunological responses to chlamydial infections and serve as a good model for rapidly assessing candidate vaccines for OEA, we investigated local expression of TNFalpha and IFNgamma in infected mice. At various time points over the course of infection mice were sacrificed, serum samples obtained for serum antibody and cytokine analyses, and livers and placental tissues were removed and fixed to determine C. abortus colonisation and cytokine expression. Immunostaining for C. abortus was significantly greater in placenta compared to liver (P<0.001), whereas local IFNgamma expression was lower and TNFalpha expression was absent in the placenta compared with the liver across all time points. Serum concentrations of both IFNgamma and TNFalpha increased throughout pregnancy in infected mice. These data suggest that a protective systemic inflammatory immune response controls maternal C. abortus infection but not placental/fetal infection in mice. In contrast to sheep, murine placental TNFalpha expression does not correlate with C. abortus infection, suggesting that the immunopathogenesis of chlamydial abortion differs in these species.
Assuntos
Infecções por Chlamydophila/metabolismo , Chlamydophila/classificação , Citocinas/metabolismo , Regulação da Expressão Gênica/fisiologia , Animais , Antígenos de Bactérias , Citocinas/genética , Feminino , Interferon gama/genética , Interferon gama/metabolismo , Fígado/microbiologia , Camundongos , Placenta/microbiologia , Gravidez , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Distribuição Tecidual , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Orf virus is the prototype parapoxvirus that causes the contagious skin disease orf. It encodes an orthologue of the cytokine interleukin (IL)-10. Recombinant orf viruses were constructed in which the viral interleukin-10 (vorfIL-10) was disabled (vorfIL-10ko) and reinserted (vorfrevIL-10) at the same locus and compared to wild-type virus for their ability to induce skin lesions in sheep. After either primary infection or reinfection, smaller less severe lesions were recorded in the vorfIL-10ko-infected animals compared with either of the vorfIL-10-intact virus-infected animals. Thus, the vorfIL-10ko virus was attenuated compared with the vorfIL-10 intact viruses, demonstrating that orf virus IL-10 is a virulence factor. The virus IL-10 is one of several virulence or immuno-modulatory factors expressed by orf virus. Removal of any one of these genes would be expected to have only a partial effect on virulence, which is what was observed in this study with vorfIL-10.