Interleukin-27 treated human macrophages induce the expression of novel microRNAs which may mediate anti-viral properties

IL-27 expression regulation and its effects on adaptive immunity against viruses

IL-27, a member of the IL-6/IL-12 cytokine superfamily, is primarily secreted by antigen presenting cells, specifically by dendric cells, macrophages and B cells. IL-27 has antiviral activities and modulates both innate and adaptive immune responses against viruses. The role of IL-27 in the setting of viral infections is not well defined and both pro-inflammatory and anti-inflammatory functions have been described. Here, we discuss the latest advancements in the role of IL-27 in several viral infection models of human disease. We highlight important aspects of IL-27 expression regulation, the critical cell sources at different stages of the infection and their impact in cell mediated immunity. Lastly, we discuss the need to better define the antiviral and modulatory (pro-inflammatory vs anti-inflammatory) properties of IL-27 in the context of human chronic viral infections.

Interleukin-27-induced HIV-resistant dendritic cells suppress reveres transcription following virus entry in an SPTBN1, autophagy, and YB-1 independent manner

Interleukin (IL)-27, a member of the IL-12 family of cytokines, induces human immunodeficiency virus (HIV)-resistant monocyte-derived macrophages and T cells. This resistance is mediated via the downregulation of spectrin beta, non-erythrocytic 1 (SPTBN1), induction of autophagy, or suppression of the acetylation of Y-box binding protein-1 (YB-1); however, the role of IL-27 administration during the induction of immature monocyte-derived dendritic cells (iDC) is poorly investigated. In the current study, we investigated the function of IL-27-induced iDC (27DC) on HIV infection. 27DC inhibited HIV infection by 95 ± 3% without significant changes in the expression of CD4, CCR5, and SPTBN1 expression, autophagy induction and acetylation of YB-1 compared to iDC. An HIV proviral DNA copy number assay displayed that 27DC suppressed reverse transcriptase (RT) reaction without influencing the virus entry. A DNA microarray analysis was performed to identify the differentially expressed genes between 27DC and iDC. Compared to iDC, 51 genes were differentially expressed in 27DC, with more than 3-fold changes in four independent donors. Cross-reference analysis with the reported 2,214 HIV regulatory host genes identified nine genes as potential interests: Ankyrin repeat domain 22, Guanylate binding protein (GBP)-1, -2, -4, -5, Stabilin 1, Serpin family G member 1 (SERPING1), Interferon alpha inducible protein 6, and Interferon-induced protein with tetratricopeptide repeats 3. A knock-down study using si-RNA failed to determine a key factor associated with the anti-HIV activity due to the induction of robust amounts of off-target effects. Overexpression of each protein in cells had no impact on HIV infection. Thus, we could not define the mechanism of the anti-HIV effect in 27DC. However, our findings indicated that IL-27 differentiates monocytes into HIV-resistant DC, and the inhibitory mechanism differs from IL-27-induced HIV-resistant macrophages and T cells.

Interleukin-27-induced HIV-resistant dendritic cells suppress reveres transcription following virus entry in an SPTBN1, Autophagy, and YB-1 independent manner

Interleukin (IL)-27, a member of the IL-12 family of cytokines, induces human immunodeficiency virus (HIV)-resistant monocyte-derived macrophages and T cells. This resistance is mediated via the downregulation of spectrin beta, non-erythrocytic 1 (SPTBN1), induction of autophagy, or suppression of the acetylation of Y-box binding protein-1 (YB-1); however, the role of IL-27 administration during the induction of immature monocyte-derived dendritic cells (iDC) is poorly investigated. In the current study, we investigated the function of IL-27-induced iDC (27DC) on HIV infection. 27DC inhibited HIV infection by 95 ± 3 % without significant changes in the expression of CD4, CCR5, and SPTBN1 expression, autophagy induction and acetylation of YB-1 compared to iDC. An HIV proviral DNA copy number assay displayed that 27DC suppressed reverse transcriptase (RT) reaction without influencing the virus entry. A DNA microarray analysis was performed to identify the differentially expressed genes between 27DC and iDC. Compared to iDC, 51 genes were differentially expressed in 27DC, with more than 3-fold changes in four independent donors. Cross-reference analysis with the reported 2,214 HIV regulatory host genes identified nine genes as potential interests: Ankyrin repeat domain 22, Guanylate binding protein (GBP)-1, -2, -4, -5, Stabilin 1, Serpin family G member 1 (SERPING1), Interferon alpha inducible protein 6, and Interferon-induced protein with tetratricopeptide repeats 3. A knock-down study using si-RNA failed to determine a key factor associated with the anti-HIV activity due to the induction of robust amounts of off-target effects. Overexpression of each protein in cells had no impact on HIV infection. Thus, we could not define the mechanism of the anti-HIV effect in 27DC. However, our findings indicated that IL-27 differentiates monocytes into HIV-resistant DC, and the inhibitory mechanism differs from IL-27-induced HIV-resistant macrophages and T cells.

Interleukin-27 Promotes Divergent Effects on HIV-1 Infection in Peripheral Blood Mononuclear Cells through BST-2/Tetherin

Interleukin-27 (IL-27) is able to inhibit HIV-1 replication in peripheral blood mononuclear cells (PBMCs), macrophages, and dendritic cells. Here, we identify that IL-27 can produce opposing effects on HIV-1 replication in PBMCs and that the HIV-1 restriction factor BST-2/Tetherin is involved in both inhibitory and enhancing effects on HIV-1 infection induced by IL-27. IL-27 inhibited HIV-1 replication when added to cells 2 h after infection, promoting the prototypical BST-2/Tetherin-induced virion accumulation at the cell membrane of HIV-1-infected PBMCs. BST-2/Tetherin gene expression was significantly upregulated in the IL-27-treated PBMCs, with a simultaneous increase in the number of BST-2/Tetherin⁺ cells. The silencing of BST-2/Tetherin diminished the anti-HIV-1 effect of IL-27. In contrast, IL-27 increased HIV-1 production when added to infected cells 4 days after infection. This enhancing effect was prevented by BST-2/Tetherin gene knockdown, which also permitted IL-27 to function again as an HIV-1 inhibitory factor. These contrasting roles of IL-27 were associated with the dynamic of viral production, since the IL-27-mediated enhancement of virus replication was prevented by antiretroviral treatment of infected cells, as well as by keeping cells under agitation to avoid cell-to-cell contact. Likewise, inhibition of CD11a, an integrin associated with HIV-1 cell-to-cell transmission, abrogated the IL-27 enhancement of HIV-1 production. Our findings illustrate the complexity of the HIV-1-host interactions and may impact the potential therapeutic use of IL-27 and other soluble mediators that induce BST-2/Tetherin expression for HIV-1 infection. IMPORTANCE Here, we describe new findings related to the ability of the cytokine IL-27 to regulate the growth of HIV-1 in CD4⁺ T lymphocytes. IL-27 has long been considered a potent inhibitor of HIV-1 replication, a notion based on several reports showing that this cytokine controls HIV-1 infection in peripheral blood mononuclear cells (PBMCs), monocyte-derived macrophages, and dendritic cells. However, our present results are contrary to the current knowledge that IL-27 acts only as a powerful downregulator of HIV-1 replication. We observed that IL-27 can either prevent or enhance viral growth in PBMCs, an outcome dependent on when this cytokine is added to the infected cells. We detected that the increase of HIV-1 dissemination is due to enhanced cell-to-cell transmission with the involvement of the interferon-induced HIV-1 restriction factor BST-2/Tetherin and CD11a (LFA-1), an integrin that participates in formation of virological synapse.

Antiviral Activities of Interleukin-27: A Partner for Interferons?

Emergence of new, pandemic-level viral threats has brought to the forefront the importance of viral immunology and continued improvement of antiviral therapies. Interleukin-27 (IL-27) is a pleiotropic cytokine that regulates both innate and adaptive immune responses. Accumulating evidence has revealed potent antiviral activities of IL-27 against numerous viruses, including HIV, influenza, HBV and more. IL-27 contributes to the immune response against viruses indirectly by increasing production of interferons (IFNs) which have various antiviral effects. Additionally, IL-27 can directly interfere with viral infection both by acting similarly to an IFN itself and by modulating the differentiation and function of various immune cells. This review discusses the IFN-dependent and IFN-independent antiviral mechanisms of IL-27 and highlights the potential of IL-27 as a therapeutic cytokine for viral infection.

IL-27 induces IFN/STAT1-dependent genes and enhances function of TIGIT+ HIVGag-specific T cells

HIV-specific T cells have diminished effector function and fail to control/eliminate the virus. IL-27, a member of the IL-6/IL-12 cytokine superfamily has been shown to inhibit HIV replication. However, whether or not IL-27 can enhance HIV-specific T cell function is largely unknown. In the present manuscript, we investigated the role of IL-27 signaling in human T cells by evaluating the global transcriptional changes related to the function of HIV-specific T cells. We found that T cells from people living with HIV (PLWH), expressed higher levels of STAT1 leading to enhanced STAT1 activation upon IL-27 stimulation. Observed IL-27 induced transcriptional changes were associated with IFN/STAT1-dependent pathways in CD4 and CD8 T cells. Importantly, IL-27 dependent modulation of T-bet expression promoted IFNγ secretion by TIGIT+HIVGag-specific T cells. This new immunomodulatory effect of IL-27 on HIV-specific T cell function suggests its potential therapeutic use in cure strategies.

Profiles of MicroRNAs in Interleukin-27-Induced HIV-Resistant T Cells: Identification of a Novel Antiviral MicroRNA

OBJECTIVES

Interleukin-27 (IL-27) is known as an anti-HIV cytokine. We have recently demonstrated that IL-27-pretreatment promotes phytohemagglutinin-stimulated CD4(+) T cells into HIV-1-resistant cells by inhibiting an uncoating step.

PURPOSE

To further characterize the function of the HIV resistant T cells, we investigated profiles of microRNA in the cells using microRNA sequencing (miRNA-seq) and assessed anti-HIV effect of the microRNAs.

METHODS

Phytohemagglutinin-stimulated CD4(+) T cells were treated with or without IL-27 for 3 days. MicroRNA profiles were analyzed using miRNA-seq. To assess anti-HIV effect, T cells or macrophages were transfected with synthesized microRNA mimics and then infected with HIVNL4.3 or HIVAD8. Anti-HIV effect was monitored by a p24 antigen enzyme-linked immunosorbent assay kit. interferon (IFN)-α, IFN-β, or IFN-λ production was quantified using each subtype-specific enzyme-linked immunosorbent assay kit.

RESULTS

A comparative analysis of microRNA profiles indicated that expression of known miRNAs was not significantly changed in IL-27-treated cells compared with untreated T cells; however, a total of 15 novel microRNAs (miRTC1 ∼ miRTC15) were identified. Anti-HIV assay using overexpression of each novel microRNA revealed that 10 nM miRTC14 (GenBank accession number: MF281439) remarkably suppressed HIV infection by (99.3 ± 0.27%, n = 9) in macrophages but not in T cells. The inhibition was associated through induction of >1000 pg/mL of IFN-αs and IFN-λ1.

CONCLUSION

We discovered a total of 15 novel microRNAs in T cells and characterized that miRTC14, one of the novel microRNAs, was a potent IFN-inducing anti-HIV miRNA, implicating that regulation of the expression of miRTC14 may be a potent therapeutic tool for not only HIV but also other virus infection.

MicroRNA Profiles in Monocyte-Derived Macrophages Generated by Interleukin-27 and Human Serum: Identification of a Novel HIV-Inhibiting and Autophagy-Inducing MicroRNA

Interleukin-27 (IL-27) is a pleiotropic cytokine that influences the innate and adaptive immune systems. It inhibits viral infection and regulates the expression of microRNAs (miRNAs). We recently reported that macrophages differentiated from human primary monocytes in the presence of IL-27 and human AB serum resisted human immunodeficiency virus (HIV) infection and showed significant autophagy induction. In the current study, the miRNA profiles in these cells were investigated, especially focusing on the identification of novel miRNAs regulated by IL-27-treatment. The miRNA sequencing analysis detected 38 novel miRNAs. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis confirmed that IL-27 differentially regulated the expression of 16 of the 38 miRNAs. Overexpression of the synthesized miRNA mimics by transfection revealed that miRAB40 had potent HIV-inhibiting and autophagy-inducing properties. B18R, an interferon (IFN)-neutralization protein, partially suppressed both activities, indicating that the two functions were induced via IFN-dependent and -independent pathways. Although the target mRNA(s) of miRAB40 involving in the induction of both functions was unable to identify in this study, the discovery of miRAB40, a potential HIV-inhibiting and autophagy inducing miRNA, may provide novel insights into the miRNA (small none-coding RNA)-mediated regulation of HIV inhibition and autophagy induction as an innate immune response.

IL-27, a pleiotropic cytokine for fine-tuning the immune response in cancer

Interleukin (IL)-27, a member of the IL-6/IL-12 family, has an important role in modulating inflammation in partnership with innate and adaptive immune cells. IL-27 binding to IL-27R starts downstream signaling based on the target cells. It can instigate inflammation by inducing CD4⁺ T cell proliferation, Th1 polarization, cytotoxic T cell activation, generation of the natural killer cell, and macrophage and dendritic cell activation. However, by inducing programmed cell death and suppression of effector cells, IL-27 can suppress inflammation and return the immune response to hemostasis. Altogether, IL-27 displays multifaceted dual functions, which may result in either pro- or anti-inflammatory effects. Recent investigations indicated the antitumor activity of IL-27 via inducing Th1, and CTL responses and generating NK cells. On the other hand, IL-27 also can promote tumor cells' proliferation, survival, and angiogenesis. In the present review, we'll discuss recent advances concerning the role of IL-27 in inflammatory diseases such as infections, autoimmune diseases with a focus on cancer.

Association between IL-27 Gene Polymorphisms and Cancer Susceptibility in Asian Population: A Meta-Analysis

BACKGROUND

Interleukin 27 (IL-27) has potent antitumor activity. Several epidemiological studies have designated that genetic variants of the IL-27 gene may contribute to various cancer susceptibility, but the data were inconclusive.  Objective: The current meta-analysis aimed to address the association between IL-27 rs153109, rs17855750, and rs181206 polymorphisms and the risk of cancer.

DATA SOURCES

Our team has selected eligible studies up to May 1, 2020, from several electronic databases, including Web of Science, PubMed, Scopus, and Google Scholar databases.

RESULTS

Our meta-analysis revealed that the carriers rs153109 A>G polymorphism in the IL-27 gene have higher risks of diseases in the heterozygous (OR=1.26, 95%CI=1.06-1.49, P=0.007, AG vs AA), homozygous (OR=1.18, 95%CI=1.01-1.37, p=0.33, GG vs AA), dominant (OR=1.25, 95%CI=1.07-1.47, P=0.006, AG+GG vs AA), and allele (OR=1.15, 95%CI=1.04-1.27, P=0.008, G vs A) genetic models. Stratified analysis by cancer type indicated that this variant was significantly associated with gastrointestinal cancer, colorectal cancer and breast cancer. The findings did not support an association between rs17855750 T>G, rs181206 T>C polymorphisms of IL-27 and cancer risk.

CONCLUSION

the current study findings suggest that IL-27 rs153109 polymorphism significantly increased the risk of cancer susceptibility. Well-designed replication in a larger independent genetic association study with larger sample sizes in diverse ethnicities is required to verify the findings. <br /><br />.

IL-27 regulation of innate immunity and control of microbial growth

IL-27 is a pleiotropic cytokine capable of influencing both innate and adaptive immune responses. With anti- and pro-inflammatory activity, IL-27 exerts its opposing effects in a cell-dependent and infectious context-specific manner. Upon pathogenic stimuli, IL-27 regulates innate immune cells, such as monocytes, dendritic cells, macrophages and neutrophils. Immune responses involving these innate cells that are negatively regulated by IL-27 signaling include inflammatory cytokine production, phagolysosomal acidification following phagocytosis, oxidative burst and autophagy. IL-27 signaling is crucial in maintaining the subtle balance between Th1 and Th2 immunity, in which protective inflammation is upregulated within the early stages of infection and subsequently downregulated once microbial growth is controlled. The immunomodulatory effects of IL-27 provide promising therapeutic targets for multiple disease types.

A primary role of IL-27 is to communicate between various immune cells to initiate different immune responses. Among these responses are those involved with destroying and eliminating microbial pathogens and then turning off inflammatory responses when the infectious threat has been resolved. IL-27 possesses both anti- and pro-inflammatory activity that varies with context, immune cell and pathogen stimulus. Depending on the precise formula of these details, there are important implications for IL-27 in disease outcomes. As such, harnessing or opposing IL-27 activity may have the potential to treat a variety of infectious diseases.

Small RNA sequences derived from pre-microRNAs in the supraspliceosome

MicroRNAs (miRNAs) are short non-coding RNAs that negatively regulate the expression and translation of genes in healthy and diseased tissues. Herein, we characterize short RNAs from human HeLa cells found in the supraspliceosome, a nuclear dynamic machine in which pre-mRNA processing occurs. We sequenced small RNAs (<200 nt) extracted from the supraspliceosome, and identified sequences that are derived from 200 miRNAs genes. About three quarters of them are mature miRNAs, whereas the rest account for various defined regions of the pre-miRNA, and its hairpin-loop precursor. Out of these aligned sequences, 53 were undetected in cellular extract, and the abundance of additional 48 strongly differed from that in cellular extract. Notably, we describe seven abundant miRNA-derived sequences that overlap non-coding exons of their host gene. The rich collection of sequences identical to pre-miRNAs at the supraspliceosome suggests overlooked nuclear functions. Specifically, the abundant hsa-mir-99b may affect splicing of LINC01129 primary transcript through base-pairing with its exon-intron junction. Using suppression and overexpression experiments, we show that hsa-mir-7704 negatively regulates the level of the lncRNA HAGLR. We claim that in cases of extended base-pairing complementarity, such supraspliceosomal pre-miRNA sequences might have a role in transcription attenuation, maturation and processing.

Inhibition of herpes simplex virus type 1 replication by novel hsa-miR-7704 in vitro

Herpes simplex virus type 1 (HSV-1) infections are one of the most common diseases in human population. HSV-1 causes subclinical, mild to severe diseases, especially in immunocompromised patients. Acyclovir has been used to reduce manifestations of HSV-1 infections. The extensive use of this drug has led to the development of resistant strains. Thus, designing a novel anti-herpes drug with different mechanisms of action is urgently needed. Cellular microRNAs (miRNAs) have direct antiviral effects in addition to their regulatory functions. In this study we used a novel miRNA (hsa-miR-7704), expressed in macrophages, to inhibit HSV-1 lytic infection in HeLa cells. Synthesized hsa-miR-7704 mimics were transfected into HSV-1 infected HeLa cell. The inhibitory effects of the miRNA were evaluated by plaque assay, real time polymerase chain reaction and the viral titers were measured by the 50% tissue culture infective dose (TCID50). The viral titer and cell cytopathic effect were dramatically decreased in HeLa cells transfected with hsa-miR-7704 (50 and 100 nM), compared with HSV-1 infected cells alone or transfected with the mock miRNA control. These results suggest that hsa-miR-7704 inhibits HSV-1 replication efficiently in vitro. This may provide an alternative mechanism to prevent HSV-1 infections.

Association of interleukin-27 gene polymorphisms with susceptibility to HIV infection and disease progression

Interleukin‐27 (IL‐27) gene polymorphisms are linked to infectious disease susceptibility and IL‐27 plasma level is associated with HIV infection. Therefore, we aimed to investigate the association between IL‐27 polymorphisms and susceptibility to HIV infection and disease progression. A total of 300 patients with HIV infection (48 long‐term nonprogressors and 252 typical progressors) and 300 healthy controls were genotyped for three IL‐27 polymorphisms, rs17855750, rs181206, rs40837 which were performed by using multiple single nucleotide primer extension technique. Significant association was found between IL‐27 rs40837 polymorphisms with susceptibility to HIV infection (AG vs AA: adjusted OR = 1.60, 95% CI, 1.11‐2.30, P = 0.012; AG+GG vs AA: adjusted OR = 1.44, 95% CI, 1.02‐2.03, P = 0.038) and disease progression (LTNP: AG vs AA: adjusted OR = 2.33, 95% CI, 1.13‐4.80, P = 0.021; TP: AG vs AA: adjusted OR = 1.50, 95% CI, 1.04‐2.24, P = 0.030). Serum IL‐27 levels were significantly lower in cases compared to controls (P < 0.001). There were lower serum IL‐27 levels in TPs than in LTNPs (P < 0.001). We further found that LTNPs with rs40837 AG or GG genotype had lower serum IL‐27 levels than with AA genotype (P < 0.05). The CD4⁺T counts in cases were significantly lower than controls (P < 0.001). In contrast, individuals with rs40837 AG genotype had lower CD4⁺T counts than with AA genotype in cases (P < 0.05). In addition, CD4⁺T counts in TPs were significantly lower than LTNPs (P < 0.001). IL‐27 rs40837 polymorphism might influence the susceptibility to HIV infection and disease progression probably by regulating the level of serum IL‐27 or the quantity of CD4⁺T.

MicroRNA-451a in extracellular, blood-resident vesicles attenuates macrophage and dendritic cell responses to influenza whole-virus vaccine

The innate immune system is important for the efficacy of vaccines, but excessive innate immune responses can cause adverse reactions after vaccination. Extracellular vesicles (EVs) are enriched in the blood and can deliver functional RNAs, such as microRNAs (miRNAs), to recipient cells, thereby mediating intercellular communication. However, the role of EVs in controlling the innate immune responses to vaccines has not been fully elucidated. Here, we found that miR-451a is abundant in human serum EVs and that its presence in blood-circulating EVs affects the innate immune responses of macrophages and dendritic cells to inactivated whole-virus vaccines (WV) against influenza. miR-451a in human serum EVs was stable for a week in healthy subjects, and its levels gradually fluctuated over several months. miR-451a within serum EVs was internalized into serum-cultured macrophages and dendritic cells and reduced endogenous 14-3-3ζ protein levels and decreased the expression of type I IFN and interleukin 6 in response to WV stimulation. miR-451a levels in blood-circulating EVs were positively correlated with intracellular miR-451a levels in mouse splenic CD11c⁺ cells and inversely correlated with the innate immune response to inactivated WV in vivo These findings suggest that miR-451a in circulating EVs is internalized into recipient cells in vivo and that this internalization results in an attenuation of the innate immune response to WV. Moreover, a microarray analysis identified several other miRNAs that affect the macrophage response to inactivated WV. Our results reveal that miRNAs in circulating EVs significantly modify the responses of macrophages and dendritic cells to inactivated WV.

Species-specific function of microRNA-7702 in human colorectal cancer cells via targeting TADA1

Colorectal cancer (CRC) is highly invasive, and an increasing number of studies report that microRNAs (miRNAs) are involved in CRC cell invasion and metastasis. However, these studies focus on miRNAs with clear functional targets, often overlooking obscure miRNAs. Using TCGA data analysis, we compared differentially expressed miRNAs in colon and rectal adenocarcinoma (stages N0 and N1/N2) to identify miRNAs involved in invasion and metastasis; one identified candidate miRNA was miR-7702. Bioinformatics analysis identified TADA1 as a possible target gene of miR-7702. The relationship between TADA1 and miR-7702 was analyzed using the Oncomine database, CRC tissues at different stages, and CRC cell lines with different metastatic properties. We used a dual luciferase-reporter assay to verify the interaction between miR-7702 and TADA1. We altered miR-7702 and TADA1 expression levels using transfection, and measured cell migration and invasion abilities. The results revealed a negative correlation between miR-7702 and TADA1 in CRC. miR-7702 was significantly downregulated in human CRC cell lines with high invasion capacity. Its overexpression suppressed human CRC cell migration and invasion by directly inhibiting TADA1. This regulatory effect of miR-7702 on TADA1 was observed in human CRC cells but not in mouse cells. These findings indicate that miR-7702 acts as a tumor suppressor in CRC by inhibiting cell migration and invasion, possibly through direct TADA1 inhibition. Our results demonstrate for the first time that miR-7702 and TADA1 are biologically functional in human CRC cells and reveal that the presence and function of miR-7702 may be species-specific.

Infection of Epstein⁻Barr Virus in Type III Latency Modulates Biogenesis of Exosomes and the Expression Profile of Exosomal miRNAs in the Burkitt Lymphoma Mutu Cell Lines

Infection of Epstein–Barr virus (EBV), a ubiquitous human gamma herpesvirus, is associated with various malignancies in B lymphocytes and epithelial cells. EBV encodes 49 microRNAs in two separated regions, termed the BART and BHRF1 loci. Although accumulating evidence demonstrates that EBV infection regulates the profile of microRNAs in the cells, little is known about the microRNAs in exosomes released from infected cells. Here, we characterized the expression profile of intracellular and exosomal microRNAs in EBV-negative, and two related EBV-infected Burkitt lymphoma cell lines having type I and type III latency by next-generation sequencing. We found that the biogenesis of exosomes is upregulated in type III latently infected cells compared with EBV-negative and type I latently infected cells. We also observed that viral and several specific host microRNAs were predominantly incorporated in the exosomes released from the cells in type III latency. We confirmed that multiple viral microRNAs were transferred to the epithelial cells cocultured with EBV-infected B cells. Our findings indicate that EBV infection, in particular in type III latency, modulates the biogenesis of exosomes and the profile of exosomal microRNAs, potentially contributing to phenotypic changes in cells receiving these exosomes.

Interleukin-27R Signaling Mediates Early Viral Containment and Impacts Innate and Adaptive Immunity after Chronic Lymphocytic Choriomeningitis Virus Infection

Chronic viral infections represent a major challenge to the host immune response, and a unique network of immunological elements, including cytokines, are required for their containment. By using a model persistent infection with the natural murine pathogen lymphocytic choriomeningitis virus clone 13 (LCMV Cl13) we investigated the role of one such cytokine, interleukin-27 (IL-27), in the control of chronic infection. We found that IL-27 receptor (IL-27R) signaling promoted control of LCMV Cl13 as early as days 1 and 5 after infection and that il27p28 transcripts were rapidly elevated in multiple subsets of dendritic cells (DCs) and myeloid cells. In particular, plasmacytoid DCs (pDCs), the most potent type 1 interferon (IFN-I)-producing cells, significantly increased il27p28 in a Toll-like receptor 7 (TLR7)-dependent fashion. Notably, mice deficient in an IL-27-specific receptor, WSX-1, exhibited a pleiotropy of innate and adaptive immune alterations after chronic lymphocytic choriomeningitis virus (LCMV) infection, including compromised NK cell cytotoxicity and antibody responses. While, the majority of these immune alterations appeared to be cell extrinsic, cell-intrinsic IL-27R was necessary to maintain early pDC numbers, which, alongside lower IFN-I transcription in CD11b⁺ DCs and myeloid cells, may explain the compromised IFN-I elevation that we observed early after LCMV Cl13 infection in IL-27R-deficient mice. Together, these data highlight the critical role of IL-27 in enabling optimal antiviral immunity early and late after infection with a systemic persistent virus and suggest that a previously unrecognized positive-feedback loop mediated by IL-27 in pDCs might be involved in this process.

IMPORTANCE Persistently replicating pathogens, such as human immunodeficiency virus, hepatitis B virus, and hepatitis C virus, represent major health problems worldwide. These infections impose a long-term challenge on the host immune system, which must be heavily and continuously regulated to keep pathogen replication in check without causing fatal immunopathology. Using a persistently replicating rodent pathogen, LCMV, in its natural host, we identified the cellular sources and effects of one important regulatory pathway, interleukin-27 receptor WSX-1 signaling, that is required for both very early and late restriction of chronic (but not acute) infection. We found that WSX-1 was necessary to promote innate immunity and the development of aberrant adaptive immune responses. This not only highlights the role of IL-27 receptor signaling in regulating distinct host responses that are known to be necessary to control chronic infections, but also positions IL-27 as a potential therapeutic target for their modulation.

A novel microRNA, hsa-miR-6852 differentially regulated by Interleukin-27 induces necrosis in cervical cancer cells by downregulating the FoxM1 expression

We have previously demonstrated that Interleukin-27 differentially regulates the expression of seven novel microRNAs. Here we elucidate the functional significance of these novel microRNAs. Of the seven microRNAs, over expression of miRNA-6852 (miR-SX4) mimic induces cell cycle arrest at G2/M phase and induces necrosis in HEK293 and panel of cervical cancer cells (Human Papilloma Virus (HPV) infected cell lines; HeLa, CaSki and SiHa cells). To define the mechanism of the miR-SX4-mediated G2/M arrest, a microarray gene chip array and western blot analysis were performed. FoxM1, a transcription factor is identified as a key protein down-regulated by miR-SX4, even though the miR-SX4 does not target 3’UTR of FoxM1. Knock down of FoxM1 using si-RNA demonstrate that FoxM1 silenced cell induces G2/M cell cycle arrest and necrosis. Our data demonstrated for the first time that miR-SX4 could be a potent anti-cancer microRNA.

Interferons and beyond: Induction of antiretroviral restriction factors

Antiviral restriction factors are structurally and functionally diverse cellular proteins that play a key role in the first line of defense against viral pathogens. Although many cell types constitutively express restriction factors at low levels, their induction in response to viral exposure and replication is often required for potent control and repulse of the invading pathogens. It is well established that type I IFNs efficiently induce antiviral restriction factors. Accumulating evidence suggests that other types of IFN, as well as specific cytokines, such as IL-27, and other activators of the cell are also capable of enhancing the expression of restriction factors and hence to establish an antiviral cellular state. Agents that efficiently induce restriction factors, increase their activity, and/or render them resistant against viral antagonists without causing general inflammation and significant side effects hold some promise for novel therapeutic or preventive strategies. In the present review, we summarize some of the current knowledge on the induction of antiretroviral restriction factors and perspectives for therapeutic application.

HIV and HIV-Tat inhibit LPS-induced IL-27 production in human macrophages by distinct intracellular signaling pathways

Monocyte-derived Mϕs (MDMs) from HIV-infected patients and MDM infected in vitro with HIV exhibit a reduced ability to secrete various cytokines, including IL-12. Recently, IL-27, an IL-12 family cytokine, was shown to inhibit HIV replication in Mϕ. Whether HIV infection or HIV accessory protein(s) impact IL-27 production in Mϕs remains unknown. Herein, we show that in vitro HIV infection, as well as intracellular HIV-Tat (Tat) and Tat peptides, inhibit LPS-induced IL-27 production in human MDMs, suggesting impairment of the TLR4 signaling pathway. To understand the signaling pathways governing HIV or Tat-mediated inhibition of LPS-induced IL-27 production, we first demonstrated that p38 MAPK, PI3K, Src-homology region 2 domain-containing tyrosine phosphatase 1 (SHP-1), and Src kinases regulate LPS-induced IL-27 production in MDMs. Tat caused down-regulation of TNFR-associated factor (TRAF)-6 and inhibitor of apoptosis 1 (cIAP-1) and subsequently decreased phosphorylation of downstream PI3K and p38 MAPKs, which were implicated in LPS-induced IL-27 production. Whereas SHP-1 and Src kinases regulated LPS-induced IL-27 production, Tat did not inhibit these kinases, suggesting that they were not involved in Tat-mediated inhibition of LPS-induced IL-27 production. In contrast to Tat, in vitro HIV infection of MDM inhibited LPS-induced IL-27 production via inhibition of p38 MAPK activation. Overall, HIV and Tat inhibit LPS-induced IL-27 production in human macrophages via distinct mechanisms: Tat through the inhibition of cIAP-1-TRAF-6 and subsequent inhibition of PI3K and p38 MAPKs, whereas HIV through the inhibition of p38 MAPK activation.

Genome-Wide Analyses of MicroRNA Profiling in Interleukin-27 Treated Monocyte-Derived Human Dendritic Cells Using Deep Sequencing: A Pilot Study

MicroRNAs (miRNAs) regulate gene expression and thereby influence cell fate and function. Recent studies suggest that an abundant class of miRNAs play important roles in immune cells, such as T cells, natural killer (NK) cells, B cells, and dendritic cells (DCs). Interleukin (IL)-27 is a member of the IL-12 family of cytokines with broad anti-viral effects. It is a potent inhibitor of HIV-1 infection in CD4+ T cells and macrophages, as well as monocyte-derived immature dendritic cells (iDCs). This pilot study compared miRNA profiles between iDCs and IL-27-treated iDCs (27DCs) using deep sequencing methods and identified 46 known miRNAs that were significantly differentially expressed in 27DCs: 36 were upregulated and 10 downregulated by IL-27. Many of the potential target genes of these miRNAs are involved in IL-27 associated pathways, such as JAK/STAT, MAPKs, and PI3K and several were also previously reported to be involved in the regulation of human DC function. This study found that these miRNAs also potentially target several viral genomes and therefore may have antiviral effects. Four of these differential miRNAs (miR-99a-5p, miR-222-3p, miR-138-5p, and miR-125b-5p) were validated using quantitative reverse transcription PCR (RT-qPCR). Twenty-two novel miRNAs were discovered from deep sequencing and confirmed using RT-qPCR. This study furthers the understanding of the role of IL-27 in immunity and lays a foundation for future characterization of the role of specific miRNAs in DCs.

A comprehensive joint analysis of the long and short RNA transcriptomes of human erythrocytes

Background

Human erythrocytes are terminally differentiated, anucleate cells long thought to lack RNAs. However, previous studies have shown the persistence of many small-sized RNAs in erythrocytes. To comprehensively define the erythrocyte transcriptome, we used high-throughput sequencing to identify both short (18–24 nt) and long (>200 nt) RNAs in mature erythrocytes.

Results

Analysis of the short RNA transcriptome with miRDeep identified 287 known and 72 putative novel microRNAs. Unexpectedly, we also uncover an extensive repertoire of long erythrocyte RNAs that encode many proteins critical for erythrocyte differentiation and function. Additionally, the erythrocyte long RNA transcriptome is significantly enriched in the erythroid progenitor transcriptome. Joint analysis of both short and long RNAs identified several loci with co-expression of both microRNAs and long RNAs spanning microRNA precursor regions. Within the miR-144/451 locus previously implicated in erythroid development, we observed unique co-expression of several primate-specific noncoding RNAs, including a lncRNA, and miR-4732-5p/-3p. We show that miR-4732-3p targets both SMAD2 and SMAD4, two critical components of the TGF-β pathway implicated in erythropoiesis. Furthermore, miR-4732-3p represses SMAD2/4-dependent TGF-β signaling, thereby promoting cell proliferation during erythroid differentiation.

Conclusions

Our study presents the most extensive profiling of erythrocyte RNAs to date, and describes primate-specific interactions between the key modulator miR-4732-3p and TGF-β signaling during human erythropoiesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2156-2) contains supplementary material, which is available to authorized users.

Dynamic Expression of Novel MiRNA Candidates and MiRNA-34 Family Members in Early- to Mid-Gestational Fetal Keratinocytes Contributes to Scarless Wound Healing by Targeting the TGF-β Pathway

Background

Early- to mid-gestational fetal mammalian skin wounds heal rapidly and without scarring. Keratinocytes (KCs) have been found to exert important effects on the regulation of fibroblasts. There may be significant differences of gestational fetal KCs at different ages. The advantages in early- to mid-gestational fetal KCs could lead to fetal scarless wound healing.

Methods

KCs from six human fetal skin samples were divided into two groups: a mid-gestation group (less than 28 weeks of gestational age) and a late-gestation group (more than 28 weeks of gestational age). RNA extracted from KCs was used to prepare a library of small RNAs for next-generation sequencing (NGS). To uncover potential novel microRNA (miRNAs), the mirTools 2.0 web server was used to identify candidate novel human miRNAs from the NGS data. Other bioinformatical analyses were used to further validate the novel miRNAs. The expression levels of the miRNAs were further confirmed by real-time quantitative RT-PCR.

Results

A total of 61.59 million reads were mapped to 1,170 known human miRNAs in miRBase. Among a total of 202 potential novel miRNAs uncovered, 106 candidates have a higher probability of being novel human miRNAs. A total of 110 miRNAs, including 22 novel miRNA candidates, were significantly differently expressed between mid- and late-gestational fetal KCs. Thirty-three differentially expressed miRNAs and miR-34 family members are correlated with the transforming growth factor-β (TGF-β) pathway.

Conclusions

Taken together, our results provide compelling evidence supporting the existence of 106 novel miRNAs and the dynamic expression of miRNAs that extensively targets the TGF-β pathway at different gestational ages in fetal KCs. MiRNAs showing altered expression at different gestational ages in fetal KCs may contribute to scarless wound healing in early- to mid-gestational fetal KCs, and thus may be new targets for potential scar prevention and reduction therapies.

Potent therapeutic target of inflammation, virus and tumor: focus on interleukin-27

Interleukin (IL)-27 is an important pleiotropic immunological regulator for having dual effects on the immune responses. Several distinct findings have been highlighted that in certain conditions, neutralizing IL-27 or its subunit IL-27p28 might be a useful strategy to limit inflammation. Recently more insights have revealed that IL-27 could also exert potent inhibitory functions in some other immune circumstances including virus infection and tumor immunity. In this review, we describe IL-27 receptor subunits and the mechanisms of individual IL-27, and summarize the advances of their preclinical application trials. In addition, the potential role of IL-27 as a clinical therapeutic target will also be discussed.

Chronic administration of Δ9-tetrahydrocannabinol induces intestinal anti-inflammatory microRNA expression during acute simian immunodeficiency virus infection of rhesus macaques

Recreational and medical use of cannabis among human immunodeficiency virus (HIV)-infected individuals has increased in recent years. In simian immunodeficiency virus (SIV)-infected macaques, chronic administration of Δ9-tetrahydrocannabinol (Δ9-THC) inhibited viral replication and intestinal inflammation and slowed disease progression. Persistent gastrointestinal disease/inflammation has been proposed to facilitate microbial translocation and systemic immune activation and promote disease progression. Cannabinoids including Δ9-THC attenuated intestinal inflammation in mouse colitis models and SIV-infected rhesus macaques. To determine if the anti-inflammatory effects of Δ9-THC involved differential microRNA (miRNA) modulation, we profiled miRNA expression at 14, 30, and 60 days postinfection (days p.i.) in the intestine of uninfected macaques receiving Δ9-THC (n=3) and SIV-infected macaques administered either vehicle (VEH/SIV; n=4) or THC (THC/SIV; n=4). Chronic Δ9-THC administration to uninfected macaques significantly and positively modulated intestinal miRNA expression by increasing the total number of differentially expressed miRNAs from 14 to 60 days p.i. At 60 days p.i., ∼28% of miRNAs showed decreased expression in the VEH/SIV group compared to none showing decrease in the THC/SIV group. Furthermore, compared to the VEH/SIV group, THC selectively upregulated the expression of miR-10a, miR-24, miR-99b, miR-145, miR-149, and miR-187, previously been shown to target proinflammatory molecules. NOX4, a potent reactive oxygen species generator, was confirmed as a direct miR-99b target. A significant increase in NOX4+ crypt epithelial cells was detected in VEH/SIV macaques compared to the THC/SIV group. We speculate that miR-99b-mediated NOX4 downregulation may protect the intestinal epithelium from oxidative stress-induced damage. These results support a role for differential miRNA induction in THC-mediated suppression of intestinal inflammation. Whether similar miRNA modulation occurs in other tissues requires further investigation.

IMPORTANCE

Gastrointestinal (GI) tract disease/inflammation is a hallmark of HIV/SIV infection. Previously, we showed that chronic treatment of SIV-infected macaques with Δ9-tetrahydrocannabinol (Δ9-THC) increased survival and decreased viral replication and infection-induced gastrointestinal inflammation. Here, we show that chronic THC administration to SIV-infected macaques induced an anti-inflammatory microRNA expression profile in the intestine at 60 days p.i. These included several miRNAs bioinformatically predicted to directly target CXCL12, a chemokine known to regulate lymphocyte and macrophage trafficking into the intestine. Specifically, miR-99b was significantly upregulated in THC-treated SIV-infected macaques and confirmed to directly target NADPH oxidase 4 (NOX4), a reactive oxygen species generator known to damage intestinal epithelial cells. Elevated miR-99b expression was associated with a significantly decreased number of NOX4+ epithelial cells in the intestines of THC-treated SIV-infected macaques. Overall, our results show that selective upregulation of anti-inflammatory miRNA expression contributes to THC-mediated suppression of gastrointestinal inflammation and maintenance of intestinal homeostasis.

miR-27a suppresses EV71 replication by directly targeting EGFR

Enterovirus 71 (EV71), a major causative agent of hand, foot, and mouth disease, has broken out several times and was accompanied by neurological disease. microRNAs, a class of small non-coding RNAs that are approximately 20 nucleotides long, play important roles in the regulation of various biological processes, including antiviral defense. However, the roles of miRNAs in EV71 replication and pathogenesis are not well understood. In this study, we found that the expression of miR-27a was significantly decreased in EV71-infected cells. Interestingly, the over-expression of miR-27a could inhibit EV71 replication, as measured by virus titration, qPCR, and Western blotting. We identified EGFR mRNA is a bona fide target of miR-27a by computational analysis and luciferase reporter assays. Furthermore, miR-27a could decrease EGFR expression, as measured by qPCR and Western blotting. Moreover, the inhibition of EGFR expression by miR-27a decreased the phosphorylation of Akt and ERK, which facilitate EV71 replication. These results suggest that miR-27a may have antiviral activity against EV71 by inhibiting EGFR.

miR-190b is markedly upregulated in the intestine in response to simian immunodeficiency virus replication and partly regulates myotubularin-related protein-6 expression

HIV replication and the cellular micro-RNA (miRNA) machinery interconnect at several posttranscriptional levels. To understand their regulatory role in the intestine, a major site of HIV/SIV replication, dissemination, and CD4(+) T cell depletion, we profiled miRNA expression in colon following SIV infection (10 acute SIV, 5 uninfected). Nine (four up and five down) miRNAs showed statistically significant differential expression. Most notably, miR-190b expression showed high statistical significance (adjusted p = 0.0032), the greatest fold change, and was markedly elevated in colon and jejunum throughout SIV infection. In addition, miR-190b upregulation was detected before peak viral replication and the nadir of CD4(+) T cell depletion predominantly in lamina propria leukocytes. Interestingly non-SIV-infected macaques with diarrhea and colitis failed to upregulate miR-190b, suggesting that its upregulation was neither inflammation nor immune-activation driven. SIV infection of in vitro-cultured CD4(+) T cells and primary intestinal macrophages conclusively identified miR-190b upregulation to be driven in response to viral replication. Further miR-190b expression levels in colon and jejunum positively correlated with tissue viral loads. In contrast, mRNA expression of myotubularin-related protein 6 (MTMR6), a negative regulator of CD4(+) T cell activation/proliferation, significantly decreased in SIV-infected macrophages. Luciferase reporter assays confirmed MTMR6 as a direct miR-190b target. To our knowledge, this is the first report, which describes dysregulated miRNA expression in the intestine, that identifies a potentially significant role for miR-190b in HIV/SIV pathogenesis. More importantly, miR-190b-mediated MTMR6 downregulation suggests an important mechanism that could keep infected cells in an activated state, thereby promoting viral replication. In the future, the mechanisms driving miR-190b upregulation including other cellular processes it regulates in SIV-infected cells need determination.

Prophylactic and therapeutic modulation of innate and adaptive immunity against mucosal infection of herpes simplex virus

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) are the most common cause of genital ulceration in humans worldwide. Typically, HSV-1 and 2 infections via mucosal route result in a lifelong latent infection after peripheral replication in mucosal tissues, thereby providing potential transmission to neighbor hosts in response to reactivation. To break the transmission cycle, immunoprophylactics and therapeutic strategies must be focused on prevention of infection or reduction of infectivity at mucosal sites. Currently, our understanding of the immune responses against mucosal infection of HSV remains intricate and involves a balance between innate signaling pathways and the adaptive immune responses. Numerous studies have demonstrated that HSV mucosal infection induces type I interferons (IFN) via recognition of Toll-like receptors (TLRs) and activates multiple immune cell populations, including NK cells, conventional dendritic cells (DCs), and plasmacytoid DCs. This innate immune response is required not only for the early control of viral replication at mucosal sites, but also for establishing adaptive immune responses against HSV antigens. Although the contribution of humoral immune response is controversial, CD4(+) Th1 T cells producing IFN-γ are believed to play an important role in eradicating virus from the hosts. In addition, the recent experimental successes of immunoprophylactic and therapeutic compounds that enhance resistance and/or reduce viral burden at mucosal sites have accumulated. This review focuses on attempts to modulate innate and adaptive immunity against HSV mucosal infection for the development of prophylactic and therapeutic strategies. Notably, cells involved in innate immune regulations appear to shape adaptive immune responses. Thus, we summarized the current evidence of various immune mediators in response to mucosal HSV infection, focusing on the importance of innate immune responses.

HIV-associated neuropathogenesis: a systems biology perspective for modeling and therapy

Despite the development of powerful antiretroviral drugs, HIV-1 associated neurological disorders (HAND) will affect approximately half of those infected with HIV-1. Combined anti-retroviral therapy (cART) targets viral replication and increases T-cell counts, but it does not always control macrophage polarization, brain infection or inflammation. Moreover, it remains difficult to identify those at risk for HAND. New therapies that focus on modulating host immune response by making use of biological pathways could prove to be more effective than cART for the treatment of neuroAIDS. Additionally, while numerous HAND biomarkers have been suggested, they are of little use without methods for appropriate data integration and a systems-level interpretation. Machine learning, could be used to develop multifactorial computational models that provide clinicians and researchers with the ability to identify which factors (in what combination and relative importance) are considered important to outcome.

The M1 and M2 paradigm of macrophage activation: time for reassessment

Macrophages are endowed with a variety of receptors for lineage-determining growth factors, T helper (Th) cell cytokines, and B cell, host, and microbial products. In tissues, macrophages mature and are activated in a dynamic response to combinations of these stimuli to acquire specialized functional phenotypes. As for the lymphocyte system, a dichotomy has been proposed for macrophage activation: classic vs. alternative, also M1 and M2, respectively. In view of recent research about macrophage functions and the increasing number of immune-relevant ligands, a revision of the model is needed. Here, we assess how cytokines and pathogen signals influence their functional phenotypes and the evidence for M1 and M2 functions and revisit a paradigm initially based on the role of a restricted set of selected ligands in the immune response.

Evaluating the potential of IL-27 as a novel therapeutic agent in HIV-1 infection

Interleukin 27 (IL-27) is an immunomodulatory cytokine with important roles in both the innate and adaptive immune systems. In the last five years, the addition of exogenous IL-27 to primary cell cultures has been demonstrated to decrease HIV-1 replication in a number of cell types including peripheral blood mononuclear cells (PBMCs), CD4+ T cells, macrophages and dendritic cells. These in vitro findings suggest that IL-27 may have therapeutic value in the setting of HIV-1 infection. In this review, we describe the current knowledge of the biology of IL-27, its effects primarily on HIV-1 replication but also in other viral infections and explore its potential role as a therapeutic cytokine for the treatment of patients with HIV-1 infection.

Modulation of inflammation by interleukin-27

A growing body of evidence suggests an essential role of the heterodimeric cytokine, IL-27, for regulating immunity. IL-27 is composed of two subunits (p28 and EBI3) and is classified as a member of the IL-12 family of cytokines. APCs have been recognized as a major cellular source of IL-27 following activation with microbial products or IFNs (types I and II). In this review, we describe the current knowledge of the implications of IL-27 during the pathogenesis of infectious and autoimmune diseases. Experimental studies have used genetically targeted IL-27RA-/- mice, EBI3-/- mice, and p28-/- mice or involved study designs with administration of bioengineered IL-27/IL-27RA homologs. Whereas many reports have described that IL-27 suppresses inflammation, we also review the current literature, suggesting promotion of inflammation by IL-27 in some settings. Recent advances have also been made in understanding the cross-talk of cleavage products of the complement system with IL-27-mediated immune responses. Additional data on IL-27 have been obtained recently by observational studies in human patients with acute and chronic inflammatory diseases. Collectively, the findings from the past decade identify IL-27 as a critical immunoregulatory cytokine, especially for T cells, whereas some controversy is fueled by results challenging the view of IL-27 as a classical silencer of inflammation.

Interleukin-2 inhibits HIV-1 replication in some human T cell lymphotrophic virus-1-infected cell lines via the induction and incorporation of APOBEC3G into the virion

IL-2 has been used in culture of primary T cells to maintain cell proliferation. We have previously reported that IL-27 inhibits HIV-1 replication in primary T cells in the presence of IL-2. To gain a better understanding of the mechanisms involved in this inhibitory effect, we attempted to investigate in detail the effects of IL-27 and IL-2 using several cell lines. Unexpectedly, IL-27 did not inhibit HIV-1 in T cell lines, whereas IL-2 inhibited HIV-1 replication in the human T cell lymphotrophic virus (HTLV)-1-transformed T cell lines, MT-2, MT-4, SLB-1, and ATL-2. No effects were seen in HTLV-1-negative cell lines. Utilizing MT-2 cells, we demonstrated that IL-2 treatment inhibited HIV-1 syncytia-inducing ability and dose-dependently decreased supernatant p24 antigen levels by >90%. Using real time PCR and Western blot analysis, we observed that IL-2 treatment induced the host restriction factor, APOBEC3G with accumulation into the lower molecular mass active form as characterized by FPLC. Further analysis revealed that the virus recovered from IL-2-treated MT-2 cells had impaired replication competency. This was found to be due to incorporation of APOBEC3G into the virion despite the presence of Vif. These findings demonstrate a novel role for IL-2 in regulating production of infectious HIV-1 virions in HTLV-1-infected cells through the induction of APOBEC3G.