Virus Targeting of the Tumor Necrosis Factor Superfamily

AbstractHerpesviruses appear to peacefully coexist with their natural hosts, with infection typically manifested as a benign, but lifelong process. However, coexistence depends on active resistance by innate and specific immune defenses as revealed in the striking virulence of herpesviruses when immunity fails. This pattern of infection is characteristic of a viral pathogen, such as cytomegalovirus, that has evolved efficient strategies targeted at host defense systems. Targeting members of the tumor necrosis factor (TNF)/lymphotoxin (LT) superfamily of cytokines is a strategy found in all herpesviruses, which suggests the existence of an intimate evolutionary link in their host–parasite relationship. Here we examine some of the strategies used by herpesvirus that target members of the TNF superfamily and discuss a recent study that revealed a novel mechanism that links LT-related ligands and interferons (IFN) to the establishment of coexistence between herpesvirus and its host cell

Cytomegalovirus exploits IL-10–mediated immune regulation in the salivary glands

The salivary glands represent a major site of cytomegalovirus replication and transmission to other hosts. Despite control of viral infection by strong T cell responses in visceral organs cytomegalovirus replication continues in the salivary glands of mice, suggesting that the virus exploits the mucosal microenvironment. Here, we show that T cell immunity in the salivary glands is limited by the induction of CD4 T cells expressing the regulatory cytokine interleukin (IL)-10. Blockade of IL-10 receptor (IL-10R) with an antagonist antibody dramatically reduced viral load in the salivary glands, but not in the spleen. The mucosa-specific protection afforded by IL-10R blockade was associated with an increased accumulation of CD4 T cells expressing interferon γ, suggesting that IL-10R signaling limits effector T cell differentiation. Consistent with this, an agonist antibody targeting the tumor necrosis factor receptor superfamily member OX40 (TNFRSF4) enhanced effector T cell differentiation and increased the number of interferon γ–producing T cells, thus limiting virus replication in the salivary glands. Collectively, the results indicate that modulating effector T cell differentiation can counteract pathogen exploitation of the mucosa, thus limiting persistent virus replication and transmission

Deletion of P2Y2 receptor reveals a role for lymphotoxin-α in fatty streak formation

Background Lymphotoxin alpha (LTα) is expressed in human atherosclerotic lesions and genetic variations in the LTα pathway have been linked to myocardial infarction. Activation of the P2Y2 nucleotide receptor (P2Y2R) regulates the production of LTα. in vitro. We aimed to uncover a potential pathway linking purinergic receptor to LTα-mediated inflammatory processes pivotal to the early stages of atherosclerosis in apolipoprotein E (ApoE−/−) deficient mice. Methods and results En face immunostaining revealed that P2Y2R and VCAM-1 are preferentially expressed in the atherosclerosis prone site of the mouse aortic sinus. Deletion of the P2Y2R gene suppresses VCAM-1 expression. Compared with ApoE−/− mice, ApoE−/− mice lacking the P2Y2R gene (ApoE−/−/P2Y2R−/−) did not develop fatty streak lesions when fed a standard chow diet for 15 weeks. Systemic and CD4+ T cell production of the pro-inflammatory cytokine lymphotoxin-alpha (LTα) were specifically inhibited in ApoE−/−/P2Y2R−/−mice. Anti-LTα preventive treatment was initiated in ApoE−/− mice with intraperitoneal administration of recombinant human tumor necrosis factor receptor 1 fusion protein (TNFR1-Fc) on 5 consecutive days before the disease onset. Remarkably, none of the TNFR1:Fc-treated ApoE−/− mice exhibited atherosclerotic lesions at any developmental stage. Significance ApoE−/− mice deficient in P2Y2R exhibit low endothelial cell VCAM-1 levels, decreased production of LTα and delayed onset of atherosclerosis. These data suggest that targeting this nucleotide receptor could be an effective therapeutic approach in atherosclerosis

A crucial role for HVEM and BTLA in preventing intestinal inflammation

The interaction between the tumor necrosis factor (TNF) family member LIGHT and the TNF family receptor herpes virus entry mediator (HVEM) co-stimulates T cells and promotes inflammation. However, HVEM also triggers inhibitory signals by acting as a ligand that binds to B and T lymphocyte attenuator (BTLA), an immunoglobulin super family member. The contribution of HVEM interacting with these two binding partners in inflammatory processes remains unknown. In this study, we investigated the role of HVEM in the development of colitis induced by the transfer of CD4(+)CD45RB(high) T cells into recombination activating gene (Rag)(-/-) mice. Although the absence of HVEM on the donor T cells led to a slight decrease in pathogenesis, surprisingly, the absence of HVEM in the Rag(-/-) recipients led to the opposite effect, a dramatic acceleration of intestinal inflammation. Furthermore, the critical role of HVEM in preventing colitis acceleration mainly involved HVEM expression by radioresistant cells in the Rag(-/-) recipients interacting with BTLA. Our experiments emphasize the antiinflammatory role of HVEM and the importance of HVEM expression by innate immune cells in preventing runaway inflammation in the intestine

LIGHT as regulator of bone homeostasis during osteolytic bone metastasis formation in non-small cell lung cancer patients

Tumor necrosis factor superfamily member 14 (TNFSF14), LIGHT is one of the cytokines produced by tumor and immune cells, which promotes homeostasis of lymphoid organs, liver and bone. Nonsmall cell lung cancer (NSCLC) commonly metastasizes bone, altering bone homeostasis and causing osteolysis. Here we investigated the role of LIGHT in NSCLC-induced osteolytic bone disease. The LIGHT expression in monocytes was higher in patients with metastatic bone lesions than in non-bone metastatic ones (66.5 ± 24.5 vs 43.3 ± 25.2 mean ± SD, p = 0.001), in healthy donors (66.5 ± 24.5 vs 8.5 ± 4.6 p = 0.0002), and in non-bone metastatic patients than in healthy donors (43.3 ± 25.2 vs 8.5 ± 4.6, p = 0.0001). Serum LIGHT levels were also significantly higher in bone metastatic patients than in non-bone metastatic ones (186.8 ± 191.2 pg/ml vs 115.8 ± 73 pg/ml, p = 0.04) and in healthy donors (186.8 ± 191.2 pg/ml vs 85.7 ± 38.4 pg/ml, p = 0.04). A neutralizing mAb anti-LIGHT added to osteoclast (OC) cultures of both bone and non-bone metastases inhibited osteoclastogenesis, but the decrease was statistically significant only for bone metastatic patients (272 ± 98 vs 132 ± 74, p = 0.01). To investigate the role of LIGHT in NSCLC- induced bone lesion in vivo, we performed an intratibial injection of a mouse lung cancer cell line LLC-1, in wild-type (WT) and LIGHT KO mice. The WT-injected mice displayed a significant reduction of about 20% for BV/TV, Tb.N, Tb.Th, and Tb.Sp compared to the WT-vehicle mice (pb 0.01). These parameters did not show significant variation for KO-injected mice vs vehicle or for WT-injected mice vs KO-injected mice. These data indicate LIGHT as a regulator of bone homeostasis during NSCLC metastatic invasion, thus it may be a novel therapeutic target in osteolytic bone metastases

Analysis of the human cytomegalovirus genomic region from UL146 through UL147A reveals sequence hypervariability, genotypic stability, and overlapping transcripts

BACKGROUND: Although the sequence of the human cytomegalovirus (HCMV) genome is generally conserved among unrelated clinical strains, some open reading frames (ORFs) are highly variable. UL146 and UL147, which encode CXC chemokine homologues are among these variable ORFs. RESULTS: The region of the HCMV genome from UL146 through UL147A was analyzed in clinical strains for sequence variability, genotypic stability, and transcriptional expression. The UL146 sequences in clinical strains from two geographically distant sites were assigned to 12 sequence groups that differ by over 60% at the amino acid level. The same groups were generated by sequences from the UL146-UL147 intergenic region and the UL147 ORF. In contrast to the high level of sequence variability among unrelated clinical strains, the sequences of UL146 through UL147A from isolates of the same strain were highly stable after repeated passage both in vitro and in vivo. Riboprobes homologous to these ORFs detected multiple overlapping transcripts differing in temporal expression. UL146 sequences are present only on the largest transcript, which also contains all of the downstream ORFs including UL148 and UL132. The sizes and hybridization patterns of the transcripts are consistent with a common 3'-terminus downstream of the UL132 ORF. Early-late expression of the transcripts associated with UL146 and UL147 is compatible with the potential role of CXC chemokines in pathogenesis associated with viral replication. CONCLUSION: Clinical isolates from two different geographic sites cluster in the same groups based on the hypervariability of the UL146, UL147, or the intergenic sequences, which provides strong evidence for linkage and no evidence for interstrain recombination within this region. The sequence of individual strains was absolutely stable in vitro and in vivo, which indicates that sequence drift is not a mechanism for the observed sequence hypervariability. There is also no evidence of transcriptional splicing, although multiple overlapping transcripts extending into the adjacent UL148 and UL132 open reading frames were detected using gene-specific probes

Act1, a Negative Regulator in CD40- and BAFF-Mediated B Cell Survival

AbstractTNF receptor (TNFR) superfamily members, CD40, and BAFFR play critical roles in B cell survival and differentiation. Genetic deficiency in a novel adaptor molecule, Act1, for CD40 and BAFF results in a dramatic increase in peripheral B cells, which culminates in lymphadenopathy and splenomegaly, hypergammaglobulinemia, and autoantibodies. While the B cell-specific Act1 knockout mice displayed a similar phenotype with less severity, the pathology of the Act1-deficient mice was mostly blocked in CD40-Act1 and BAFF-Act1 double knockout mice. CD40- and BAFF-mediated survival is significantly increased in Act1-deficent B cells, with stronger IκB phosphorylation, processing of NF-κB2 (p100/p52), and activation of JNK, ERK, and p38 pathways, indicating that Act1 negatively regulates CD40- and BAFF-mediated signaling events. These findings demonstrate that Act1 plays an important role in the homeostasis of B cells by attenuating CD40 and BAFFR signaling