Modified two-part strategy to rapidly improve target traits

OBJECTIVE Propose a modified two-part strategy by combining the benefits of population improvement and the conventional pipeline to rapidly improve target traits while reducing the risks of a full two-part transition

Modified two-part strategy to rapidly improve target traits

OBJECTIVE Propose a modified two-part strategy by combining the benefits of population improvement and the conventional pipeline to rapidly improve target traits while reducing the risks of a full two-part transition

Breaking tolerance to the natural human liver autoantigen cytochrome P450 2D6 by virus infection

Autoimmune liver diseases, such as autoimmune hepatitis (AIH) and primary biliary cirrhosis, often have severe consequences for the patient. Because of a lack of appropriate animal models, not much is known about their potential viral etiology. Infection by liver-tropic viruses is one possibility for the breakdown of self-tolerance. Therefore, we infected mice with adenovirus Ad5 expressing human cytochrome P450 2D6 (Ad-2D6). Ad-2D6–infected mice developed persistent autoimmune liver disease, apparent by cellular infiltration, hepatic fibrosis, “fused” liver lobules, and necrosis. Similar to type 2 AIH patients, Ad-2D6–infected mice generated type 1 liver kidney microsomal–like antibodies recognizing the immunodominant epitope WDPAQPPRD of cytochrome P450 2D6 (CYP2D6). Interestingly, Ad-2D6–infected wild-type FVB/N mice displayed exacerbated liver damage when compared with transgenic mice expressing the identical human CYP2D6 protein in the liver, indicating the presence of a stronger immunological tolerance in CYP2D6 mice. We demonstrate for the first time that infection with a virus expressing a natural human autoantigen breaks tolerance, resulting in a chronic form of severe, autoimmune liver damage. Our novel model system should be instrumental for studying mechanisms involved in the initiation, propagation, and precipitation of virus-induced autoimmune liver diseases

Inhibition of Different Lassa Virus Strains by Alpha and Gamma Interferons and Comparison with a Less Pathogenic Arenavirus

The high pathogenicity of Lassa virus is assumed to involve resistance to the effects of interferon (IFN). We have analyzed the effects of alpha IFN (IFN-α), IFN-γ, and tumor necrosis factor alpha (TNF-α) on replication of Lassa virus compared to the related, but less pathogenic, lymphocytic choriomeningitis virus (LCMV). Three low-passage Lassa virus strains (AV, NL, and CSF), isolated from humans with mild to fulminant Lassa fever, were tested. Lassa virus replication was inhibited by IFN-α and IFN-γ, but not TNF-α, in Huh7 and Vero cells. The degree of IFN sensitivity of a Lassa virus isolate did not correlate with disease severity in human patients. Furthermore, cytokine effects observed for Lassa virus and LCMV (strains CH-5692, Armstrong, and WE) were similar. To address the mechanisms involved in the IFN effect, we used cell lines in which overexpression of IFN-stimulated proteins promyelocytic leukemia protein (PML) and Sp100 could be induced. Both proteins reside in PML bodies, a cellular target of the LCMV and Lassa virus Z proteins. Overexpression of PML or Sp100 did not affect replication of either virus. This, together with the previous finding that PML knockout facilitates LCMV replication in vitro and in vivo (M. Djavani, J. Rodas, I. S. Lukashevich, D. Horejsh, P. P. Pandolfi, K. L. Borden, and M. S. Salvato, J. Virol. 75:6204-6208, 2001; W. V. Bonilla, D. D. Pinschewer, P. Klenerman, V. Rousson, M. Gaboli, P. P. Pandolfi, R. M. Zinkernagel, M. S. Salvato, and H. Hengartner, J. Virol. 76:3810-3818, 2002), describes PML as a mediator within the antiviral pathway rather than as a direct effector protein. In conclusion, the high pathogenicity of Lassa virus compared to LCMV is probably not due to increased resistance to the effects of IFN-α or IFN-γ. Both cytokines inhibit replication which is relevant for the design of antiviral strategies against Lassa fever with the aim of enhancing the IFN response

The Inhibitory Receptor BTLA Controls γδ T Cell Homeostasis and Inflammatory Responses

Summaryγδ T cells rapidly secrete inflammatory cytokines at barrier sites that aid in protection from pathogens, but mechanisms limiting inflammatory damage remain unclear. We found that retinoid-related orphan receptor gamma-t (RORγt) and interleukin-7 (IL-7) influence γδ T cell homeostasis and function by regulating expression of the inhibitory receptor, B and T lymphocyte attenuator (BTLA). The transcription factor RORγt, via its activating function-2 domain, repressed Btla transcription, whereas IL-7 increased BTLA levels on the cell surface. BTLA expression limited γδ T cell numbers and sustained normal γδ T cell subset frequencies by restricting IL-7 responsiveness and expansion of the CD27−RORγt+ population. BTLA also negatively regulated IL-17 and TNF production in CD27− γδ T cells. Consequently, BTLA-deficient mice exhibit enhanced disease in a γδ T cell-dependent model of dermatitis, whereas BTLA agonism reduced inflammation. Therefore, by coordinating expression of BTLA, RORγt and IL-7 balance suppressive and activation stimuli to regulate γδ T cell homeostasis and inflammatory responses

Lymphotoxin-Mediated Crosstalk between B Cells and Splenic Stroma Promotes the Initial Type I Interferon Response to Cytomegalovirus

SummaryToll-like receptor (TLR)-dependent pathways control the production of IFNαβ, a key cytokine in innate immune control of viruses including mouse cytomegalovirus (MCMV). The lymphotoxin (LT) αβ-LTβ receptor signaling pathway is also critical for defense against MCMV and thought to aid in the IFNβ response. We find that upon MCMV infection, mice deficient for lymphotoxin (LT)αβ signaling cannot mount the initial part of a biphasic IFNαβ response, but show normal levels of IFNαβ during the sustained phase of infection. Significantly, the LTαβ-dependent, IFNαβ response is independent of TLR signaling. B, but not T, cells expressing LTβ are essential for promoting the initial IFNαβ response. LTβR expression is required strictly in splenic stromal cells for initial IFNαβ production to MCMV and is dependent upon the NF-κB-inducing kinase (NIK). These results reveal a TLR-independent innate host defense strategy directed by B cells in communication with stromal cells via the LTαβ cytokine system

Cure of prediabetic mice by viral infections involves lymphocyte recruitment along an IP-10 gradient

Viruses can cause but can also prevent autoimmune disease. This dualism has certainly hampered attempts to establish a causal relationship between viral infections and type 1 diabetes (T1D). To develop a better mechanistic understanding of how viruses can influence the development of autoimmune disease, we exposed prediabetic mice to various viral infections. We used the well-established NOD and transgenic RIP-LCMV models of autoimmune diabetes. In both cases, infection with the lymphocytic choriomeningitis virus (LCMV) completely abrogated the diabetic process. Interestingly, such therapeutic viral infections resulted in a rapid recruitment of T lymphocytes from the islet infiltrate to the pancreatic draining lymph node, where increased apoptosis was occurring. In both models this was associated with a selective and extensive expression of the chemokine IP-10 (CXCL10), which predominantly attracts activated T lymphocytes, in the pancreatic draining lymph node, and in RIP-LCMV mice it depended on the viral antigenic load. In RIP-LCMV mice, blockade of TNF-α or IFN-γ in vivo abolished the prevention of T1D. Thus, virally induced proinflammatory cytokines and chemokines can influence the ongoing autoaggressive process beneficially at the preclinical stage, if produced at the correct location, time, and levels