Peterhans Ernst, Jungi Thomas W, Schweizer Matthias
Institute of Veterinary Virology, University of Bern, Laenggass-Strasse 122, PO Box, CH-3001 Bern, Switzerland.
Biologicals. 2003 Jun;31(2):107-12. doi: 10.1016/s1045-1056(03)00024-1.
Infection with bovine viral diarrhea virus (BVDV) is prevalent in the cattle population worldwide. The virus exists in two biotypes, cytopathic and non-cytopathic, depending on the effect of the viruses on cultured cells. BVDV may cause transient and persistent infections which differ fundamentally in the host's antiviral immune response. Transient infection may be due to both cytopathic and non-cytopathic biotypes of BVDV and leads to a specific immune response. In contrast, only non-cytopathic BVD viruses can establish persistent infection as a result of infection of the embryo early in its development. Persistent infection is characterized by immunotolerance specific for the infecting viral strain. In this paper we discuss the role of innate immune responses in the two types of infection. In general, both transient and persistent infections are associated with an increased frequency of secondary infections. Associated with the increased risk of such infections are, among others, impaired bacteria killing and decreased chemotaxis. Interestingly, non-cytopathic BVDV fails to induce interferon type I in cultured bovine macrophages whereas cytopathic biotypes readily trigger this response. Cells infected with non-cytopathic BVDV are also resistant to induction of interferon by double stranded RNA, a potent interferon inducer signalling the presence of viral replication in the cell. Thus, non-cytopathic BVDV may dispose of a mechanism suppressing a key element of the antiviral defence of the innate immune system. Since interferon is also important in the activation of the adaptive immune response, suppression of this signal may be essential for the establishment of persistent infection and immunotolerance.
牛病毒性腹泻病毒（BVDV）感染在全球牛群中普遍存在。该病毒存在两种生物型，即细胞病变型和非细胞病变型，这取决于病毒对培养细胞的影响。BVDV可引起短暂感染和持续感染，这两种感染在宿主的抗病毒免疫反应上存在根本差异。短暂感染可能由BVDV的细胞病变型和非细胞病变型引起，并导致特异性免疫反应。相比之下，只有非细胞病变型BVD病毒能够在胚胎发育早期感染后建立持续感染。持续感染的特征是对感染病毒株具有免疫耐受性。在本文中，我们讨论了先天性免疫反应在这两种感染类型中的作用。一般来说，短暂感染和持续感染都与继发感染频率增加有关。与此类感染风险增加相关的因素包括细菌杀伤受损和趋化性降低等。有趣的是，非细胞病变型BVDV在培养的牛巨噬细胞中无法诱导I型干扰素，而细胞病变型生物型则很容易引发这种反应。感染非细胞病变型BVDV的细胞对双链RNA（一种表明细胞内存在病毒复制的强效干扰素诱导剂）诱导的干扰素也具有抗性。因此，非细胞病变型BVDV可能具有一种抑制先天性免疫系统抗病毒防御关键要素的机制。由于干扰素在适应性免疫反应的激活中也很重要，抑制这种信号可能对建立持续感染和免疫耐受性至关重要。
