Caspase-3-like proteases are activated by infection but are not required for replication of vesicular stomatitis virus

Infection with vesicular stomatitis virus (VSV), the prototype rhabdovirus, causes apoptotic DNA fragmentation, but the role of apoptosis in the VSV-host interaction remains unclear. Apoptosis is the gene-regulated mechanism triggered by a wide variety of stimuli that lead to cell death in a choreographed manner. In the present study, infection of the Jurkat T cell line with VSV led to activation of caspase-3 and caspase-7, with subsequent apoptotic events involving poly (ADP ribose) polymerase (PARP) cleavage, DNA fragmentation, and membrane damage. Caspase activation was correlated with viral protein expression suggesting a link between viral replication and apoptosis. We hypothesized that VSV replication might depend on apoptosis and that the inhibition of apoptosis would lead to significant decreases in viral titers. When various inhibitors of apoptosis in VSV-infected cells were used, PARP cleavage and DNA fragmentation were inhibited but the production of infectious progeny was not affected. In addition, we demonstrated that the activation of caspase-3-like proteases is required for VSV-induced apoptosis but not in vitro viral replication. Apoptosis following VSV infection is likely to be either a host-cell attempt to control viral replication or may be a ploy used by the virus to facilitate its in vivo replication and spread.     

Individual expression of poliovirus 2Apro and 3Cpro induces activation of caspase-3 and PARP cleavage in HeLa cells

The expression of individual viral genes enables the study of their effects on cellular functions. Our group previously generated stable HeLa cell lines that efficiently express poliovirus proteases 2A (clone 2A7d) and 3C (clone 3C7) under the control of tetracycline [Virology 266 (2000a) 352; J. Virol. 74 (2000b) 2383]. Upon induction of these proteases, the cells undergo drastic morphological alterations and eventually die. The present paper characterizes, in detail, the cellular and molecular events that lead to cell death in these lines. Several signs of apoptosis were observed in both 2A7d- and 3C7-induced cells, such as nuclear fragmentation, DNA breakdown (as determined by TUNEL), and phosphatidylserine translocation. Protease 2A induces the cleavage of poly-ADP-ribose-polymerase (PARP). This is blocked by the caspase-3 inhibitor DEVD in both 2A7d-On and 3C7-On cells suggesting that this enzyme might account for PARP cleavage in both cell lines. The results indicate that both poliovirus proteases induce apoptosis by mechanisms involving caspase activation, although the kinetics of apoptosis differs.     

Interaction with XIAP prevents full caspase-3/-7 activation in proliferating human T lymphocytes

Caspases are essential mediators of cytokine release and apoptosis. Additionally, caspase activity is required for the proliferation of naive T lymphocytes. It remained unclear how proliferating cells are able to cope with the pro-apoptotic activity especially of effector caspases-3 and -7. Possible reasons might include limited subcellular localization of active caspases or inhibition by endogenous caspase inhibitors. Here, we compared the activation of various caspases in proliferating human T cells with that in apoptotic cells. We show that cleaved caspases-3/-7 appear to be widely distributed in apoptotic cells while they are largely confined to the cytoplasm in proliferating cells. Additionally, in proliferating T cells caspase-3 remains incompletely cleaved, while in apoptotic cells fully mature caspase-3 is generated. We provide evidence that during T cell proliferation the intracellular caspase inhibitor X-linked inhibitor-of-apoptosis protein (XIAP) interacts with caspases-3/-7, thereby blocking their full activation, substrate cleavage, and cell death. The lack of substrate cleavage might also lead to the observed limited subcellular distribution of caspases-3/-7. After induction of apoptosis, second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with low isoelectric point (Smac/DIABLO) is released from mitochondria, resulting in the abrogation of the inhibitory effect of XIAP, full activation of caspases-3/-7, and apoptosis.     

Vesicular stomatitis virus induces apoptosis at early stages in the viral cycle and does not depend on virus replication

We detected apoptosis induction in the vesicular stomatitis virus (VSV) infected mammalian cell lines Vero-76, Cos-7, and BHK-21. Cell lines were analyzed by chromosomal DNA fragmentation and nuclear morphology. In order to determine the step in the viral cycle at which apoptosis of infected cells is triggered, chemical and physical agents were used to block viral infection at different times and then the apoptotic response of infected cells was examined. The treatment of Vero-76 infected cells with a lysosomotrophic agent, such as NH4Cl, was shown to abrogate virus apoptosis induction. On the other hand, VSV-induced apoptosis was not blocked by the presence of cycloheximide, suggesting that the de novo viral protein synthesis is not required for this process. UV-inactivated viruses were also capable of inducing apoptosis in Vero-76 cells, indicating that the activation of a programmed cell death process by VSV does not require viral replication. We conclude from these findings that VSV induces apoptosis at early stages of infection.     

Host cell killing by the West Nile Virus NS2B-NS3 proteolytic complex: NS3 alone is sufficient to recruit caspase-8-based apoptotic pathway

The West Nile Virus (WNV) non-structural proteins 2B and 3 (NS2B-NS3) constitute the proteolytic complex that mediates the cleavage and processing of the viral polyprotein. NS3 recruits NS2B and NS5 proteins to direct protease and replication activities. In an effort to investigate the biology of the viral protease, we cloned cDNA encoding the NS2B-NS3 proteolytic complex from brain tissue of a WNV-infected dead crow, collected from the Lower Merion area (Merion strain). Expression of the NS2B-NS3 gene cassette induced apoptosis within 48 h of transfection. Electron microscopic analysis of NS2B-NS3-transfected cells revealed ultra-structural changes that are typical of apoptotic cells including membrane blebbing, nuclear disintegration and cytoplasmic vacuolations. The role of NS3 or NS2B in contributing to host cell apoptosis was examined. NS3 alone triggers the apoptotic pathways involving caspases-8 and -3. Experimental results from the use of caspase-specific inhibitors and caspase-8 siRNA demonstrated that the activation of caspase-8 was essential to initiate apoptotic signaling in NS3-expressing cells. Downstream of caspase-3 activation, we observed nuclear membrane ruptures and cleavage of the DNA-repair enzyme, PARP in NS3-expressing cells. Nuclear herniations due to NS3 expression were absent in the cells treated with a caspase-3 inhibitor. Expression of protease and helicase domains themselves was sufficient to trigger apoptosis generating insight into the apoptotic pathways triggered by NS3 from WNV.     

Cleavage of FLICE (caspase-8) by granzyme B during cytotoxic T lymphocyte-induced apoptosis

Cytotoxic T lymphocytes induce apoptosis in target cells through the CD95(APO-1/Fas) and the perforin/granzyme B (GrB) pathway. The exact substrate of GrB in vivo is still unknown, but to induce apoptosis GrB requires the activity of caspases in target cells. We show here that in HeLa target cells induction of apoptosis through the perforin/GrB pathway resulted in minor direct cleavage of CPP32 (caspase-3) by GrB. Most caspase-3 cleavage resulted from activation of an upstream caspase. Moreover, target cells derived from caspase-3^?/? mice displayed GrB-induced poly(ADP-ribose) polymerase (PARP) cleavage with only partially reduced efficiency compared to wild-type target cells. This indicates that other PARP-cleaving caspases can be activated during perforin/GrB-induced cell death. In contrast to caspase-3, FLICE (caspase-8) was directly cleaved by GrB in HeLa cells. We therefore conclude that FLICE not only plays a central role in CD95(APO-1/Fas)-induced apoptosis but can also be directly activated during perforin/GrB-induced apoptosis.     

半胱氨酸蛋白酶-3抑制剂对大鼠缺血再灌流脑区神经元凋亡的影响

目的探讨半胱氨酸蛋白酶3(caspase3)抑制剂z DEVD fmk对大脑皮层缺血再灌流区神经元凋亡的影响。方法制备大脑中动脉栓塞再灌流大鼠模型,于再灌流前向治疗组缺血侧脑室注射z DEVD fmk(7μg/kg)。采用Western印迹分析、TUNEL和免疫组织化学染色(SPAB法)等方法,检测各组颞顶叶皮层缺血再灌流区caspase3表达和活化、多(ADP核糖)聚合酶(PARP)表达和切割灭活及神经元凋亡。结果未治疗组(A组)、二甲基亚砜对照组(B组)、z DEVD fmk治疗组(C组),再灌流1h及24h缺血脑区的caspase3前体含量分别为16.7±3.0、11.5±3.0、47.5±3.5及76.1±3.5、71.3±6.4、88.2±5.5;12000caspase3切割片段含量分别为8.2±2.3、9.4±1.2、4.3±1.6及59.0±6.3、60.5±7.2、17.3±2.8;PARP含量分别为12.6±3.0、13.9±2.0、53.7±4.1及67.5±8.6、61.1±6.6、93.6±4.1;24000PARP切割片段含量分别为6.0±0.7、6.6±1.2、3.6±1.1及27.4±2.6、25.8±3.2、12.1±2.8(相对灰度值);凋亡神经元密度分别为83.3±7.5、84.3±5.7、45.7±4.0及197.4±11.8、185.2±11.2、99.1±5.8(个/0.1mm2,x±s)。3组各自再灌流不同时间点缺血脑区以上5种指标的差异均有统计学意义(P<0.05～0.001);C组再灌流各时间点缺血脑区以上5种指标与A组及B组对应时间点比较,差异也均有统计学意义(P<0.05～0.001),但A、B两组间比较差异无统计学意义(P>0.05);各组再灌流不同时间点这5种指标的变化彼此间均呈正相关(r=0.630～0.942,P<0.01)。各组缺血再灌流脑区表达PARP的细胞主要是神经元,但3组间比较其密度差别不大。结论再灌流激发的caspase3表达和活化异常增加使PARP过度切割灭活,是再灌流导致缺血脑区受损神经元凋亡的重要分子机制;z DEVD fmk可通过抑制caspase3活性和自活化,减少PARP切割灭活,阻止受损神经元凋亡。     

Apoptosis and necrosis in vaccinia virus-infected HeLa G and BSC-40 cells

In most cells, vaccinia virus (VACV) infection is considered to cause a lytic cell death, an equivalent of necrosis. However, upon infection of the epithelial cell lines HeLa G and BSC-40 with VACV strain Western Reserve (WR), we have previously observed an increased activation of and activity attributable to caspases, a typical sign of apoptosis. In this paper, we have further analyzed the type of cell death in VACV-infected cells HeLa G and BSC-40. In a cell-based flow cytometric assay, we showed a specific activation of caspase-2 and 4 in HeLa G and BSC-40 cells infected with VACV, strain WR, while we did not find any effects of inhibitors of calpain and cathepsin D and E. The actual activity of the two caspases, but also of caspase-3, was then confirmed in lysates of infected HeLa G, but not in BSC-40 cells. Accordingly, poly(ADP)-ribose polymerase (PARP) cleavage was found increased only in infected HeLa G cells. Consequently, we have determined morphological features of apoptosis and/or activity of the executioner caspase-3 in infected HeLa G cells in situ, while only a background apoptosis was observed in infected BSC-40 cells. Finally, vaccination strains Dryvax and Praha were found to induce apoptosis in both HeLa G and BSC-40 cells, as characterized morphologically and by PARP cleavage. These findings may be important for understanding the differences in VACV-host interactions and post-vaccination complications in different individuals.     

Influence of caspase activity on micronuclei detection: a possible role for caspase-3 in micronucleation

Aneugenic and clastogenic agents are good inducers of both micronuclei and apoptosis. In its turn, apoptosis may modify the threshold values for the induction of micronuclei. This is of major concern for accurate assessment of hazard related to exposure to mutagens. In the present work we studied the influence of caspases, the key regulators of the apoptotic process, on the induction of micronuclei in the cytokinesis block micronucleus assay. For this, we applied a combined approach in which both human peripheral blood mononucleated cells (PBMC) and the paired human breast carcinoma cell lines MCF-7, which is caspase-3 deficient, and the caspase-3 transfected MCF-7 (MCF-7casp-3) were used to study the influence of caspase activity on micronuclei. When nocodazole induced apoptosis was inhibited by the use of inhibitors of the two main apical caspases-8 and -9 in PBMC, the frequencies of micronucleated binucleates (MNCB) increased with inhibition of these caspases confirming that apoptosis can eliminate micronucleated cells. On the contrary when caspase-3 was inhibited, the frequencies of MNCB was lower, suggesting a role of caspase-3, also in micronuclei formation. To verify this hypothesis, we compared the induction of apoptosis and micronuclei by the aneugen nocodazole, the clastogen methyl methane sulfonate (MMS) and the non-mutagenic apoptogen staurosporin in MCF-7 and MCF-7casp-3 cells. The results showed that when caspase-3 activity was impaired, in the parental MCF-7 cell line or in the MCF-7casp-3 cells in the presence of the caspase-3 inhibitor, the frequencies of nocodazole or MMS induced micronuclei decreased. These results suggest that caspase-3, besides its function as an effector caspase in the apoptotic pathway, is also involved in the formation of micronuclei.     

多聚(ADP-核糖)聚合酶和半胱天冬蛋白酶-3在过氧亚硝基阴离子致气道上皮细胞损伤中的作用

目的:探讨过氧亚硝基阴离子(ONOO^-)介导气道上皮细胞损伤的作用机制。方法: 在培养的大鼠气道上皮细胞(RTE), 观察应用多聚(ADP-核糖)聚合酶(PARP)抑制剂3-氨基苯甲酰胺(3-AB)和半胱天冬氨酸蛋白酶-3(caspase-3)抑制剂Ac-DEVD-CHO后, 外源性给予ONOO^-对RTE细胞乳酸脱氢酶(LDH)释放、凋亡百分率的影响, 用Westernblot分析PARP裂解片段。结果:3-AB不能完全抑制ONOO^-引起的RTE细胞LDH释放率的增高。3-AB对ONOO^-引起的RTE细胞凋亡无明显影响。Ac-DEVD-CHO呈剂量依赖性抑制ONOO^-诱导的RTE细胞凋亡。ONOO^-致RTE细胞凋亡过程中有PARP的裂解。结论:PARP活化是ONOO^-介导RTE细胞损伤的途径之一, 过度的PARP活化参与了ONOO^-所致的RTE细胞坏死;caspase-3活化裂解PARP在ONOO^-致RTE细胞凋亡过程中起重要作用。     

Nitric oxide protects cultured rheumatoid synovial cells from Fas-induced apoptosis by inhibiting caspase-3

Nitric oxide (NO) is elevated in the synovial fluids and sera of patients with rheumatoid arthritis (RA) and is thought to be an important proinflammatory mediator in the rheumatoid synovium. To test the hypothesis that NO might modulate the apoptosis-inducing signal pathway, we investigated the effects of NO on rheumatoid synovial-cell apoptosis induced by Fas ligation with anti-Fas antibody. Pretreatment of synovial cells with the NO donor S-nitro-N-acetylpenicillamine (SNAP) prevented the Fas-mediated induction of apoptosis. The activation of caspase-3 was required to mediate Fas-induced synovial cell apoptosis. The NO donor SNAP inhibited Fas-induced caspase-3 activation in rheumatoid synovial cells. However, NO did not interrupt Fas-induced caspase-8 cleavage or subsequent cytochrome c release into the cytosol in rheumatoid synovial cells. These data indicate that NO prevents apoptosis in rheumatoid synovial cells by directly inhibiting caspase-3 activation. Thus, we propose that NO interferes with cell death signal transduction and may contribute to rheumatoid synovial cell proliferation by inhibiting induction of apoptosis.     

Feline calicivirus replication induces apoptosis in cultured cells

Infection of Crandell-Rees feline kidney (CRFK) cells by feline calicivirus (FCV) causes rapid cytopathic effects followed by cell death. In this study, we observed that FCV replication in cells results in the induction of changes characteristic of apoptosis, including translocation of phosphatidyl serine to the cell outer membrane, chromatin condensation, and oligonucleosomal DNA fragmentation. FCV infection was associated with increases in the activities of caspase-3, -8, and -9, with the level of activation of caspase-3 higher than those of caspases-8 and -9. Caspase activation in CRFK cells was not observed when cells were inoculated with UV-inactivated FCV or when cycloheximide was present during virus infection, indicating that FCV replication and de novo synthesis of virus proteins are critical for induction of apoptosis.     

Ectopic expression of Bcl-2 and Bcl-xL inhibits apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL) through suppression of caspases-8, 7, and 3 and BID cleavage in human acute myelogenous leukemia cell line HL-60.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is one of the latest members of the TNF superfamily known to induce apoptosis in a wide variety of tumor cells. Some cell types, however, are quite resistant to TRAIL. We investigated the effect of ectopic expression of Bcl-2 and Bcl-xL on TRAIL-induced apoptosis in human acute myelogenous leukemia HL-60 cells. We found that HL-60 cells, which express TRAIL receptors (also called death receptor, DR) DR4, DR5, and Dc (decoy) R2, are highly sensitive to TRAIL-induced cytotoxicity. Greater than 90% killing occurred within 24 h of TRAIL treatment. The expression of Bcl-2 and Bcl-xL, however, completely abolished the TRAIL-induced cytotoxic effects. Treatment of HL-60 cells with TRAIL induced caspase-8 activation within 2-4 h, but no activation could be seen in Bcl-2-expressing or Bcl-xL-expressing cells. TRAIL also induced cleavage of BID, which was also abolished by Bcl-2 and Bcl-xL. Similarly, TRAIL activated caspase-3 and caspase-7 in control cells but not in cells expressing Bcl-2 or Bcl-xL. Cleavage of the caspase-3 substrate poly(ADP-ribose) polymerase (PARP), was abrogated by ectopic expression of Bcl-2 and Bcl-xL. Inhibition of caspases by the pan-caspase inhibitor, benzyloxycarbonyl-valine-alanine-aspartate-fluoromethylketone (zVAD-fmk) abolished the TRAIL-induced apoptosis. Overall, these results indicate that TRAIL-induced apoptosis involves activation of caspase-8, caspase-7, caspase-3, and BID cleavage, and Bcl-2 and Bcl-xL prevents TRAIL-induced apoptosis by abrogating caspase activation and BID cleavage.     

Photodynamic therapy induced Fas-mediated apoptosis in human carcinoma cells

Photodynamic therapy (PDT) is a clinical approach that utilizes light-activated drugs for the treatment of a variety of pathologic conditions. Human poorly (CNE2) and moderately differentiated (TW0-1) human nasopharyngeal carcinoma (NPC) cells undergo rapid apoptosis when treated with PDT sensitized with Hypocrellin A (HA) and Hypocrellin B (HB). It has been shown that these compounds have a strong photodynamic effect on tumors and viruses. The initiating events of PDT sensitized HA and HB-induced apoptosis are poorly defined. In the current study, we sought to determine whether Fas/FasL upregulation and involvement of mitochondrial events are an early event in HA and HB-treated PDT induced apoptosis. Loss of mitochondrial transmembrane potential, release of cytochrome c, involvement of caspases-8 and -3 and the status caspase-3 specific substrate PARP, were evaluated in PDT treated tumor cells. Photoactivation of HA and HB enhanced both CD95/CD95L expression and induced CD95-signaling dependent cell death in all tumor cell lines studied. CD95/ CD95L expression appeared within 2 h following light activation and appeared to be a primary event in PDT induced apoptosis. Furthermore, these results indicate that release of mitochondrial cytochrome c into the cytoplasm is a secondary event following the activation of initiator caspase-8 preceding caspase-3 activation, cleavage of PARP and DNA fragmentation. Cytochrome c appeared in the cytosol within 2-3 h post PDT. Cleavage of PARP was observed at 3-4 h following PDT and caspase-3 specific inhibitor DEVD-CHO and broad-spectrum caspases inhibitor z-VAD-fmk blocked caspase-3 activation and PARP cleavage suggesting that caspase-3 plays an important role in HA and HB-induced apoptosis.     

Rabies virus-induced apoptosis involves caspase-dependent and caspase-independent pathways

Previously, it has been shown that the laboratory attenuated rabies virus CVS-B2C, but not the wild-type virus SHBRV, induces apoptosis in mice and the induction of apoptosis is mediated by viral glycoprotein. Induction of apoptosis by CVS-B2C limits the spread of the virus in the CNS. In the present study, we characterized the pathways by which CVS-B2C induces apoptosis. BSR cells were infected with CVS-B2C or SHBRV and harvested at different time points for detection of apoptosis by immunofluorescence and flow cytometry. Apoptosis was detected only in cells infected with CVS-B2C, but not SHBRV. Caspase activity and expression of several apoptotic proteins were analyzed by fluorometric assay and Western blotting. Activation of caspase-8 and -3, but not of caspase-9, was observed in CVS-B2C-infected cells. In addition, the level of expression of Apaf-1 did not change. Furthermore, PARP was cleaved confirming activation of downstream caspases. All these data suggest that CVS-B2C infection activates the extrinsic, but not the intrinsic, apoptotic pathway. In addition, AIF, a caspase-independent apoptotic protein was up-regulated and translocated from the cytoplasm to the nucleus post-infection, suggesting that apoptosis induced by CVS-B2C also involves the activation of a caspase-independent pathway.     

Matrix protein mutations contribute to inefficient induction of apoptosis leading to persistent infection of human neural cells by vesicular stomatitis virus

In a model system to study factors involved in the establishment of a persistent viral infection that may lead to neurodegenerative diseases, Indiana and New Jersey variants of vesicular stomatitis virus (VSV) with different capacities to infect and persist in human neural cells were studied. Indiana matrix (M) protein mutants and the wild-type New Jersey strain persisted in the human neural cell line H4 for at least 120 days. The Indiana wild-type virus (HR) and a non-M mutant (TP6), both unable to persist, induced apoptosis more strongly than all the other variants tested, as indicated by higher levels of DNA fragmentation and caspase-3-like activity. Transfection of H4 cells with mRNA coding for the VSV M protein confirmed the importance of this protein in the induction of apoptosis. Furthermore, the pan-caspase inhibitor ZVAD-fmk maintained cell survival to about 80%, whereas inhibition of caspase-8, caspase-9, or both only partially protected the cells against death, consistent with the fact that anti-apoptotic molecules from the Bcl-2 family also protect cells from death only partially. These results suggest that VSV activates many pathways of cell death and that an inefficient induction of caspase-3-related apoptosis participates in the establishment of a persistent infection of human neural cells by less virulent VSV variants.     

Cytochrome c-dependent activation of caspase-3 by tumor necrosis factor requires induction of the mitochondrial permeability transition

The killing of L929 mouse fibroblasts by tumor necrosis factor-alpha (TNF-alpha) in the presence of 0.5 microg/ml actinomycin D (Act D) is prevented by inhibition of the mitochondrial permeability transition (MPT) with cyclosporin A (CyA) in combination with the phospholipase A(2) inhibitor aristolochic acid (ArA). The MPT is accompanied by the release of cytochrome c from the mitochondria, caspase-8 and caspase-3 activation in the cytosol, cleavage of the nuclear enzyme poly(ADP-ribose)polymerase (PARP), and DNA fragmentation, all of which were inhibited by CyA plus ArA. The caspase-3 inhibitor z-Asp-Glu-Val-aspartic acid fluoromethyl-ketone (Z-DEVD-FMK) did not prevent the loss of viability or the redistribution of cytochrome c, but it did prevent caspase-3 activation, PARP cleavage, and DNA fragmentation. Inhibition of the MPT reduced the activation of caspase-8 to the level occurring with TNF-alpha alone (no ActD). The caspase-8 inhibitor z-Ile-Glu(OMe)-Thr-Asp(OMe) fluoromethylketone (Z-IETD-FMK) did not prevent the cell killing and decreased only slightly the translocation of Bid to the mitochondria. These data indicate that induction of the MTP by TNF-alpha causes a release of cytochrome c, caspase-3 activation with PARP cleavage and DNA fragmentation. The loss of viability is dependent on the MPT but independent of the activation of caspase-3. The activation of caspase-8 is not dependent on the MPT. There is no evidence linking this enzyme to the loss of viability. Thus, the killing of L929 fibroblasts by TNF-alpha can occur in the absence of either caspase-3 or caspase-8 activity. Alternatively, cell death can be prevented despite an activation of caspase-8.     

A laboratory-attenuated vesicular stomatitis virus induces apoptosis and alters the cellular microRNA expression profile in BHK cells

In the present study, we characterized the pathways by which a laboratory-attenuated vesicular stomatitis virus (La-VSV) induces apoptosis in BHK cells. It was found that La-VSV induced a loss of mitochondrial membrane potential (ΔΨm) and activated caspase-9 and -3, but not caspase-8, indicating that the induction of apoptosis by La-VSV may involve an intrinsic apoptotic pathway. Although aberrant expression of microRNAs (miRNAs) has been linked to viral infection, little is known about changes in the cellular miRNA expression profile following VSV infection. Here, we attempted to identify miRNA expression profiles in VSV-infected BHK cells using miRNA microarray. Data analysis revealed that 28 miRNAs consistently responded to VSV-infection, 12 of which were down-regulated and 16 of which were up-regulated. miR-146a of these miRNAs has been found to be up-regulated in LPS-stimulated monocytes and VSV-infected macrophages, suggesting that VSV-induced miR-146a expression occurs not only in immune cells but also in other host cells. We further found that miR-706 inhibited VSV-induced apoptosis by decreasing caspase-3 and -9 activation, suggesting that induction of miR-706 expression may be a novel strategy for survival of VSV, allowing it to escape the apoptosis response of the host. In summary, our results indicate that miRNAs might play important roles in VSV infection and that their aberrant expression could be involved in VSV pathogenesis.