Type 1 IFNs (IFN-I) generally protect mammalian hosts from virus infections, but in some cases, IFN-I is pathogenic. Because IFN-I is protective, it is commonly used to treat virus infections for which no specific approved drug or vaccine is available. The Middle East respiratory syndrome–coronavirus (MERS-CoV) is such an infection, yet little is known about the role of IFN-I in this setting. Here, we show that IFN-I signaling is protective during MERS-CoV infection. Blocking IFN-I signaling resulted in delayed virus clearance, enhanced neutrophil infiltration, and impaired MERS-CoV–specific T cell responses. Notably, IFN-I administration within 1 day after infection (before virus titers peak) protected mice from lethal infection, despite a decrease in IFN-stimulated gene (ISG) and inflammatory cytokine gene expression. In contrast, delayed IFN-β treatment failed to effectively inhibit virus replication, increased infiltration and activation of monocytes, macrophages, and neutrophils in the lungs, and enhanced proinflammatory cytokine expression, resulting in fatal pneumonia in an otherwise sublethal infection. Together, these results suggest that the relative timing of the IFN-I response and maximal virus replication is key in determining outcomes, at least in infected mice. By extension, IFN-αβ or combination therapy may need to be used cautiously to treat viral infections in clinical settings.
Rudragouda Channappanavar, Anthony R. Fehr, Jian Zheng, Christine Wohlford-Lenane, Juan E. Abrahante, Matthias Mack, Ramakrishna Sompallae, Paul B. McCray Jr., David K. Meyerholz, Stanley Perlman
Cytosolic arginine sensor for mTORC1 subunits 1 and 2 (CASTOR1 and CASTOR2) inhibit the mammalian target of rapamycin complex 1 (mTORC1) upon arginine deprivation. mTORC1 regulates cell proliferation, survival, and metabolism and is often dysregulated in cancers, indicating that cancer cells may regulate CASTOR1 and CASTOR2 to control mTORC1 signaling and promote tumorigenesis. mTORC1 is the most effective therapeutic target of Kaposi sarcoma, which is caused by infection with the Kaposi sarcoma–associated herpesvirus (KSHV). Hence, KSHV-induced cellular transformation is a suitable model for investigating mTORC1 regulation in cancer cells. Currently, the mechanism of KSHV activation of mTORC1 in KSHV-induced cancers remains unclear. We showed that KSHV suppressed CASTOR1 and CASTOR2 expression to activate the mTORC1 pathway. CASTOR1 or CASTOR2 overexpression and mTOR inhibitors abolished cell proliferation and colony formation in soft agar of KSHV-transformed cells by attenuating mTORC1 activation. Furthermore, the KSHV-encoded miRNA miR-K4-5p, and probably miR-K1-5p, directly targeted CASTOR1 to inhibit its expression. Knockdown of miR-K1-5p and -K4-5p restored CASTOR1 expression and thereby attenuated mTORC1 activation. Overexpression of CASTOR1 or CASTOR2 and mTOR inhibitors abolished the activation of mTORC1 and growth transformation induced by pre–miR-K1 and -K4. Our results define the mechanism of KSHV activation of the mTORC1 pathway and establish the scientific basis for targeting this pathway to treat KSHV-associated cancers.
Tingting Li, Enguo Ju, Shou-Jiang Gao
Highly effective direct-acting antivirals against Hepatitis C virus (HCV) have created an opportunity to transplant organs from HCV-positive individuals into HCV-negative recipients, since de novo infection can be routinely cured. As this procedure is performed more widely, it becomes increasingly important to understand the biological underpinnings of virus transmission, especially the multiplicity of infection. Here, we used single genome sequencing of plasma virus in four genotype 1a HCV-positive organ donors and their seven organ recipients to assess the genetic bottleneck associated with HCV transmission following renal and cardiac transplantation. In all recipients, de novo infection was established by multiple genetically distinct viruses that reflect the full phylogenetic spectrum of replication-competent virus circulating in donor plasma. This was true in renal and cardiac transplantation and in recipients with peak viral loads ranging between 2.9 and 6.6 log10 IU/mL. The permissive transmission process characterized here contrasts sharply with sexual or injection-related transmission, which occurs less frequently per exposure and is generally associated with a stringent genetic bottleneck. These findings highlight the effectiveness of current anti-HCV regimens, while raising caution regarding the substantially higher multiplicity of infection seen in organ transplantation-associated HCV acquisition.
Muhammad N. Zahid, Shuyi Wang, Gerald H. Learn, Peter L. Abt, Emily A. Blumberg, Peter P. Reese, David S. Goldberg, George M. Shaw, Katharine J. Bar
Influenza A virus (IAV)-specific T cell responses are important correlates of protection during primary and subsequent infections. Generation and maintenance of robust IAV-specific T cell responses relies on T cell interactions with dendritic cells (DCs). In this study, we explore the role of nucleotide-binding domain leucine-rich repeat containing receptor family member NLRC4 in modulating the DC phenotype during IAV infection. Nlrc4-/- mice had worsened survival and increased viral titers during infection, normal innate immune cell recruitment and IAV-specific CD8 T cell responses, but severely blunted IAV-specific CD4 T cell responses compared to wild-type mice. The defect in the pulmonary IAV-specific CD4 T cell response was not a result of defective priming or migration of these cells in Nlrc4-/- mice but was instead due to an increase in FasL+ DCs, resulting in IAV-specific CD4 T cell death. Together, our data support a novel role for NLRC4 in regulating the phenotype of lung DCs during a respiratory viral infection, and thereby influencing the magnitude of protective T cell responses.
Emma E. Hornick, Jargalsaikhan Dagvadorj, Zeb R. Zacharias, Ann M. Miller, Ryan A. Langlois, Peter Chen, Kevin L. Legge, Gail A. Bishop, Fayyaz S. Sutterwala, Suzanne L. Cassel
T cell therapy is a promising means to treat chronic HBV infection and HBV-associated hepatocellular carcinoma. T cells engineered to express an HBV-specific T cell receptor (TCR) may achieve cure of HBV infection upon adoptive transfer. We investigated the therapeutic potential and safety of T cells stably expressing high affinity HBV envelope- or core-specific TCRs recognizing European and Asian HLA-A2 subtypes. Both CD8+ and CD4+ T cells from healthy donors and from chronic hepatitis B patients became polyfunctional effector cells when grafted with HBV-specific TCRs and eliminated HBV from infected HepG2-NTCP cell cultures. A single transfer of TCR-grafted T cells into HBV-infected, humanized mice controlled HBV infection and virological markers declined 4-5 log or below detection limit. When — as in a typical clinical setting — only a minority of hepatocytes were infected, engineered T cells specifically cleared infected hepatocytes without damaging non-infected cells. Cell death was compensated by hepatocyte proliferation and alanine amino transferase levels peaking at day 5 to 7 normalized again thereafter. Co-treatment with the entry inhibitor Myrcludex B ensured long-term control of HBV infection. Thus, T cells stably transduced with highly functional TCRs have the potential to mediate clearance of HBV-infected cells causing limited liver injury.
Karin Wisskirchen, Janine Kah, Antje Malo, Theresa Asen, Tassilo Volz, Lena Allweiss, Jochen M. Wettengel, Marc Lütgehetmann, Stephan Urban, Tanja Bauer, Maura Dandri, Ulrike Protzer
Cytomegalovirus (CMV) has been implicated in glioblastoma (GBM); however, a mechanistic connection in vivo has not been established. The purpose of this study is to characterize the effects of murine CMV (MCMV) on GBM growth in murine models. Syngeneic GBM models were established in mice perinatally infected with MCMV. We found that tumor growth was markedly enhanced in MCMV+ mice, with a significant reduction in overall survival compared with that of controls (P < 0.001). We observed increased angiogenesis and tumor blood flow in MCMV+ mice. MCMV reactivation was observed in intratumoral perivascular pericytes and tumor cells in mouse and human GBM specimens, and pericyte coverage of tumor vasculature was strikingly augmented in MCMV+ mice. We identified PDGF-D as a CMV-induced factor essential for pericyte recruitment, angiogenesis, and tumor growth. The antiviral drug cidofovir improved survival in MCMV+ mice, inhibiting MCMV reactivation, PDGF-D expression, pericyte recruitment, and tumor angiogenesis. These data show that MCMV potentiates GBM growth in vivo by increased pericyte recruitment and angiogenesis due to alterations in the secretome of CMV-infected cells. Our model provides evidence for a role of CMV in GBM growth and supports the application of antiviral approaches for GBM therapy.
Harald Krenzlin, Prajna Behera, Viola Lorenz, Carmela Passaro, Mykola Zdioruk, Michal O. Nowicki, Korneel Grauwet, Hong Zhang, Magdalena Skubal, Hirotaka Ito, Rachel Zane, Michael Gutknecht, Marion B. Griessl, Franz Ricklefs, Lai Ding, Sharon Peled, Arun Rooj, C. David James, Charles S. Cobbs, Charles H. Cook, E. Antonio Chiocca, Sean E. Lawler
The E3 ubiquitin ligase Pellino 1 (Peli1) is a microglia-specific mediator of autoimmune encephalomyelitis. Its role in neurotropic flavivirus infection is largely unknown. Here, we report that mice deficient in Peli1 (Peli1–/–) were more resistant to lethal West Nile virus (WNV) infection and exhibited reduced viral loads in tissues and attenuated brain inflammation. Peli1 mediates chemokine and proinflammatory cytokine production in microglia and promotes T cell and macrophage infiltration into the CNS. Unexpectedly, Peli1 was required for WNV entry and replication in mouse macrophages and mouse and human neurons and microglia. It was also highly expressed on WNV-infected neurons and adjacent inflammatory cells from postmortem patients who died of acute WNV encephalitis. WNV passaged in Peli1–/– macrophages or neurons induced a lower viral load and impaired activation in WT microglia and thereby reduced lethality in mice. Smaducin-6, which blocks interactions between Peli1 and IRAK1, RIP1, and IKKε, did not inhibit WNV-triggered microglia activation. Collectively, our findings suggest a nonimmune regulatory role for Peli1 in promoting microglia activation during WNV infection and identify a potentially novel host factor for flavivirus cell entry and replication.
Huanle Luo, Evandro R. Winkelmann, Shuang Zhu, Wenjuan Ru, Elizabeth Mays, Jesus A. Silvas, Lauren L. Vollmer, Junling Gao, Bi-Hung Peng, Nathen E. Bopp, Courtney Cromer, Chao Shan, Guorui Xie, Guangyu Li, Robert Tesh, Vsevolod L. Popov, Pei-Yong Shi, Shao-Cong Sun, Ping Wu, Robyn S. Klein, Shao-Jun Tang, Wenbo Zhang, Patricia V. Aguilar, Tian Wang
Hemagglutination inhibition (HI) titers are a major correlate of protection for influenza-related illness. The influenza virus hemagglutinin possesses antigenic sites that are the targets of HI active antibodies. Here, a panel of mutant viruses each lacking a classically defined antigenic site was created to compare the species-specific immunodominance of the antigenic sites in a clinically relevant hemagglutinin. HI active antibodies of antisera from influenza-virus infected mice targeted sites Sb and Ca2. HI active antibodies of guinea pigs were not directed against any specific antigenic site, although trends were observed towards Sb, Ca2, and Sa. HI titers of antisera from infected ferrets were significantly affected by site Sa. HI active antibodies of adult humans followed yet another immunodominance pattern, where sites Sb and Sa were immunodominant. When comparing the HI profiles between different species by antigenic cartography, animals and humans grouped separately. This study provides characterizations of the antibody-mediated immune responses against the head domain of a recent H1 hemagglutinin in animals and humans.
Sean T.H. Liu, Mohammad Amin Behzadi, Weina Sun, Alec W. Freyn, Wen-Chun Liu, Felix Broecker, Randy A. Albrecht, Nicole M. Bouvier, Viviana Simon, Raffael Nachbagauer, Florian Krammer, Peter Palese
Zika virus (ZIKV) is a teratogenic mosquito-borne flavivirus which can be sexually transmitted from man to woman. High viral loads and prolonged viral shedding in semen suggest that ZIKV replicates within the human male genital tract, but its target organs are unknown. Using ex vivo infection of organotypic cultures, we demonstrated here that ZIKV replicates in human testicular tissue and infects a broad range of cell types, including germ cells, which we also identified as infected in the semen from ZIKV-infected donors. ZIKV had no major deleterious effect on the morphology and hormonal production of the human testis explants. Infection induced a broad antiviral response but no interferon up-regulation and minimal pro-inflammatory response in testis explants, with no cytopathic effect. Finally, we studied ZIKV infection in mouse testis, and compared it to human infection. This study provides key insights into how ZIKV may persist in semen and alter semen parameters, as well as a valuable tool for testing antiviral agents.
Giulia Matusali, Laurent Houzet, Anne-Pascale Satie, Dominique Mahé, Florence Aubry, Thérèse Couderc, Julie Frouard, Salomé Bourgeau, Karim Bensalah, Sylvain Lavoué, Guillaume Joguet, Louis Bujan, André Cabié, Gleide F. Avelar, Marc Lecuit, Anna Le Tortorec, Nathalie Dejucq-Rainsford
Kaposi’s sarcoma–associated herpesvirus (KSHV) is a gammaherpesvirus that is the etiological agent of the endothelial cell cancer Kaposi’s sarcoma (KS) and 2 B cell lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD). KSHV ORF36, also known as viral protein kinase (vPK), is a viral serine/threonine kinase. We previously reported that KSHV vPK enhances cell proliferation and mimics cellular S6 kinase to phosphorylate ribosomal protein S6, a protein involved in protein synthesis. We created a mouse model to analyze the function of vPK in vivo. We believe this is the first mouse tumor model of a viral kinase encoded by a pathogenic human virus. We observed increased B cell activation in the vPK transgenic mice compared with normal mice. We also found that, over time, vPK transgenic mice developed a B cell hyperproliferative disorder and/or a high-grade B cell non-Hodgkin lymphoma at a greatly increased incidence compared with littermate controls. This mouse model shows that a viral protein kinase is capable of promoting B cell activation and proliferation as well as augmenting lymphomagenesis in vivo and may therefore contribute to the development of viral cancers.
Penny M. Anders, Nathan D. Montgomery, Stephanie A. Montgomery, Aadra P. Bhatt, Dirk P. Dittmer, Blossom Damania
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