Neoplastic Transformation of T Lymphocytes through Transgenic Expression of a Virus Host Modification Protein

Abstract

Virus host evasion genes are ready-made tools for gene manipulation and therapy. In this work we have assessed the impact in vivo of the evasion gene A238L of the African Swine Fever Virus, a gene which inhibits transcription mediated by both NF-κB and NFAT. The A238L gene has been selectively expressed in mouse T lymphocytes using tissue specific promoter, enhancer and locus control region sequences for CD2. The resulting two independently derived transgenic mice expressed the transgene and developed a metastasic, angiogenic and transplantable CD4+CD8+CD69– lymphoma. The CD4+CD8+CD69– cells also grew vigorously in vitro. The absence of CD69 from the tumour cells suggests that they were derived from T cells at a stage prior to positive selection. In contrast, transgenic mice similarly expressing a mutant A238L, solely inhibiting transcription mediated by NF-κB, were indistinguishable from wild type mice. Expression of Rag1, Rag2, TCRβ-V8.2, CD25, FoxP3, Bcl3, Bcl2 l14, Myc, IL-2, NFAT1 and Itk, by purified CD4+CD8+CD69– thymocytes from A238L transgenic mice was consistent with the phenotype. Similarly evaluated expression profiles of CD4+CD8+ CD69– thymocytes from the mutant A238L transgenic mice were comparable to those of wild type mice. These features, together with the demonstration of (mono-)oligoclonality, suggest a transgene-NFAT-dependent transformation yielding a lymphoma with a phenotype reminiscent of some acute lymphoblastic lymphomas.

African Swine Fever Virus F317L Protein Inhibits NF-κB Activation To Evade Host Immune Response and Promote Viral Replication

“…ASFV DP96R inhibits TBK1 phosphorylation to block type I IFN production and NF-κB activation ( 30 ). ASFV A238L contains ankyrin repeats homologous to the ankyrin repeats of IκB, and it interacts with p65 of the NF-κB complex, thereby inhibiting NF-κB activation ( 17 , 18 , 31 ). Many other viruses have also evolved complex countermeasures to subvert the innate immune response; for example, vaccinia virus protein B14 binds to IKKβ to prevent IKKβ autophosphorylation and activation, thereby inhibiting NF-κB signaling ( 32 ).…”

BCL2L14 (BCL2-like 14 (apoptosis facilitator))

“…BCL2L14 expression is markedly up-regulated in CD4 + T-cells from patients with the autoimmune disorder, systemic lupus erythematosus (SLE) and several lines of evidence implicate this dysregulation in pathogenesis (Luo et al, 2009). Dysregulated expression of BCL2L14 in mammalian cells has also been noted in response to infection with a variety of pathogens (Flori et al, 2008;Mehra et al, 2010;Balas et al, 2011;Singh et al, 2011;Taubert et al, 2010;Almeida et al, 2012;Wang et al, 2012), indicative of a role in innate immunity.…”

“…BCL2L14 may also be implicated in the host response to viral evasion mechanisms per se. For example, selective expression of the African Swine Fever Virus evasion gene, A238L, in mouse Tlymphocytes results in the production of an aggressive lymphoma (Almeida et al, 2012). Transgenic animals exhibit massively enlarged thymuses characterized, inter alia, by enhanced BCL2L14 expression and apoptosis (Almeida et al, 2012).…”

“…For example, selective expression of the African Swine Fever Virus evasion gene, A238L, in mouse Tlymphocytes results in the production of an aggressive lymphoma (Almeida et al, 2012). Transgenic animals exhibit massively enlarged thymuses characterized, inter alia, by enhanced BCL2L14 expression and apoptosis (Almeida et al, 2012). While attendant changes in host cell interferon signalling may account for many of the above changes in BCL2L14 expression, it should be noted that Bcl-G can directly interact with a component of the Flavivirus replication complex (Le Breton et al, 2011).…”