scholarly journals Oropouche virus glycoprotein topology and cellular requirements for virus-like particle assembly

2020 ◽  
Author(s):  
Natalia S. Barbosa ◽  
Luis L. P. daSilva ◽  
Colin M. Crump ◽  
Stephen C. Graham
Keyword(s):  
Virus Infection ◽  
South America ◽  
Particle Production ◽  
Febrile Illness ◽  
Etiological Agent ◽  
Particle Assembly ◽  
Virus Surface ◽  
Virus Like Particle ◽  
Surface Glycoproteins

AbstractOropouche virus (OROV; Genus: Orthobunyavirus) is the etiological agent of Oropouche fever, a debilitating febrile illness common in South America. To facilitate studies of OROV budding and assembly, we developed a system for producing OROV virus-like particles (VLPs). Using this system we show that the OROV surface glycoproteins Gn and Gc self-assemble to form VLPs independently of the non-structural protein NSm. Mature OROV Gn has two trans-membrane domains that are crucial for glycoprotein translocation to the Golgi complex and VLP production. Inhibition of Golgi function using the drugs brefeldin A and monensin inhibit VLP secretion, with monensin treatment leading to an increase in co-localisation of OROV glycoproteins with the cis-Golgi marker protein GM130. Infection studies have previously shown that the cellular Endosomal Sorting Complexes Required for Transport (ESCRT) machinery is recruited to Golgi membranes during OROV assembly and that ESCRT activity is required for virus secretion. We demonstrate that a dominant negative form of the ESCRT-associated ATPase VPS4 significantly reduces Gn secretion in our VLP assay. Proteasome inhibition using the drug MG132 also disrupts VLPs secretion, suggesting that ubiquitylation promotes ESCRT-mediated VLP release. Additionally, we observe co-localisation between OROV glycoproteins and a specific subset of fluorescently-tagged ESCRT-III components, providing the first insights into which ESCRT-III components are required for OROV assembly. Our in vitro assay for OROV VLP production has allowed us to define molecular interactions that promote OROV release and will facilitate future studies of orthobunyavirus assembly.ImportanceOropouche virus is the etiological agent of Oropouche fever, a debilitating febrile illness common in South America. The tripartite genome of this zoonotic virus is capable of reassortment and there have been multiple epidemics of Oropouche fever in South America over the last 50 years, making Oropouche virus infection a significant threat to public health. However, the molecular characteristics of this arbovirus are poorly understood. We have developed an in vitro virus-like particle production assay for Oropouche virus, allowing us to study the assembly and release of this dangerous pathogen without high-containment biosecurity. We determined the polyprotein sites that are cleaved to yield the mature Oropouche virus surface glycoproteins and characterised the cellular machinery required for glycoprotein secretion. Our study provides important insights into the molecular biology of Oropouche virus infection, in addition to presenting a robust virus-like particle production assay that should facilitate future functional and pharmacological inhibition studies.

scholarly journals Generation of Recombinant Oropouche Viruses Lacking the Nonstructural Protein NSm or NSs

2015 ◽  
Vol 90 (5) ◽  
pp. 2616-2627 ◽  
Author(s):  
Natasha L. Tilston-Lunel ◽  
Gustavo Olszanski Acrani ◽  
Richard E. Randall ◽  
Richard M. Elliott
Keyword(s):  
South America ◽  
Virus Replication ◽  
Nonstructural Protein ◽  
Urban Expansion ◽  
Febrile Illness ◽  
Wild Type Virus ◽  
Human Pathogen ◽  
Coding Region ◽  
Successful Recovery

ABSTRACTOropouche virus (OROV) is a midge-borne human pathogen with a geographic distribution in South America. OROV was first isolated in 1955, and since then, it has been known to cause recurring outbreaks of a dengue-like illness in the Amazonian regions of Brazil. OROV, however, remains one of the most poorly understood emerging viral zoonoses. Here we describe the successful recovery of infectious OROV entirely from cDNA copies of its genome and generation of OROV mutant viruses lacking either the NSm or the NSs coding region. Characterization of the recombinant viruses carried outin vitrodemonstrated that the NSs protein of OROV is an interferon (IFN) antagonist as in other NSs-encoding bunyaviruses. Additionally, we demonstrate the importance of the nine C-terminal amino acids of OROV NSs in IFN antagonistic activity. OROV was also found to be sensitive to IFN-α when cells were pretreated; however, the virus was still capable of replicating at doses as high as 10,000 U/ml of IFN-α, in contrast to the family prototype BUNV. We found that OROV lacking the NSm protein displayed characteristics similar to those of the wild-type virus, suggesting that the NSm protein is dispensable for virus replication in the mammalian and mosquito cell lines that were tested.IMPORTANCEOropouche virus (OROV) is a public health threat in Central and South America, where it causes periodic outbreaks of dengue-like illness. In Brazil, OROV is the second most frequent cause of arboviral febrile illness after dengue virus, and with the current rates of urban expansion, more cases of this emerging viral zoonosis could occur. To better understand the molecular biology of OROV, we have successfully rescued the virus along with mutants. We have established that the C terminus of the NSs protein is important in interferon antagonism and that the NSm protein is dispensable for virus replication in cell culture. The tools described in this paper are important in terms of understanding this important yet neglected human pathogen.

scholarly journals The Conserved Tyr176/Leu177 Motif in the α-Helix 9 of the Feline Immunodeficiency Virus Capsid Protein Is Critical for Gag Particle Assembly

Viruses ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 816
Author(s):  
César A. Ovejero ◽  
Silvia A. González ◽  
José L. Affranchino
Keyword(s):  
Feline Immunodeficiency Virus ◽  
Particle Production ◽  
Equine Infectious Anemia Virus ◽  
Particle Assembly ◽  
Immunodeficiency Virus ◽  
Immature Particle ◽  
Gag Assembly ◽  
Hiv 1

The capsid domain (CA) of the lentiviral Gag polyproteins has two distinct roles during virion morphogenesis. As a domain of Gag, it mediates the Gag–Gag interactions that drive immature particle assembly, whereas as a mature protein, it self-assembles into the conical core of the mature virion. Lentiviral CA proteins are composed of an N-terminal region with seven α-helices and a C-terminal domain (CA-CTD) formed by four α-helices. Structural studies performed in HIV-1 indicate that the CA-CTD helix 9 establishes homodimeric interactions that contribute to the formation of the hexameric Gag lattice in immature virions. Interestingly, the mature CA core also shows inter-hexameric associations involving helix 9 residues W184 and M185. The CA proteins of feline immunodeficiency virus (FIV) and equine infectious anemia virus (EIAV) exhibit, at equivalent positions in helix 9, the motifs Y176/L177 and L169/F170, respectively. In this paper, we investigated the relevance of the Y176/L177 motif for FIV assembly by introducing a series of amino acid substitutions into this sequence and studying their effect on in vivo and in vitro Gag assembly, CA oligomerization, mature virion production, and viral infectivity. Our results demonstrate that the Y176/L177 motif in FIV CA helix 9 is essential for Gag assembly and CA oligomerization. Notably, mutations converting the FIV CA Y176/L177 motif into the HIV-1 WM and EIAV FL sequences allow substantial particle production and viral replication in feline cells.

scholarly journals Inositol phosphates promote HIV-1 assembly and maturation to facilitate viral spread in human CD4+ T cells

2021 ◽  
Vol 17 (1) ◽  
pp. e1009190
Author(s):  
Gregory A. Sowd ◽  
Christopher Aiken
Keyword(s):  
T Cells ◽  
Particle Production ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Virus Production ◽  
Particle Assembly ◽  
Gag Protein ◽  
Viral Spread ◽  
Hiv 1

Gag polymerization with viral RNA at the plasma membrane initiates HIV-1 assembly. Assembly processes are inefficient in vitro but are stimulated by inositol (1,3,4,5,6) pentakisphosphate (IP5) and inositol hexakisphosphate (IP6) metabolites. Previous studies have shown that depletion of these inositol phosphate species from HEK293T cells reduced HIV-1 particle production but did not alter the infectivity of the resulting progeny virions. Moreover, HIV-1 substitutions bearing Gag/CA mutations ablating IP6 binding are noninfectious with destabilized viral cores. In this study, we analyzed the effects of cellular depletion of IP5 and IP6 on HIV-1 replication in T cells in which we disrupted the genes encoding the kinases required for IP6 generation, IP5 2-kinase (IPPK) and Inositol Polyphosphate Multikinase (IPMK). Knockout (KO) of IPPK from CEM and MT-4 cells depleted cellular IP6 in both T cell lines, and IPMK disruption reduced the levels of both IP5 and IP6. In the KO lines, HIV-1 spread was delayed relative to parental wild-type (WT) cells and was rescued by complementation. Virus release was decreased in all IPPK or IPMK KO lines relative to WT cells. Infected IPMK KO cells exhibited elevated levels of intracellular Gag protein, indicative of impaired particle assembly. IPMK KO compromised virus production to a greater extent than IPPK KO suggesting that IP5 promotes HIV-1 particle assembly in IPPK KO cells. HIV-1 particles released from infected IPPK or IPMK KO cells were less infectious than those from WT cells. These viruses exhibited partially cleaved Gag proteins, decreased virion-associated p24, and higher frequencies of aberrant particles, indicative of a maturation defect. Our data demonstrate that IP6 enhances the quantity and quality of virions produced from T cells, thereby preventing defects in HIV-1 replication.

Using FRET to Measure the Time it Takes for a Cell to Destroy a Virus

2019 ◽  
Author(s):  
Candace E. Benjamin ◽  
Zhuo Chen ◽  
Olivia Brohlin ◽  
Hamilton Lee ◽  
Stefanie Boyd ◽  
...  
Keyword(s):  
Cellular Uptake ◽  
Rhodamine B ◽  
Virus Like Particle ◽  
A Cell ◽  
Viral Nanoparticles ◽  
The Stability ◽  
Open Question ◽  
Viral Surface ◽  
Fret Pair

<div><div><div><p>The emergence of viral nanotechnology over the preceding two decades has created a number of intellectually captivating possible translational applications; however, the in vitro fate of the viral nanoparticles in cells remains an open question. Herein, we investigate the stability and lifetime of virus-like particle (VLP) Qβ - a representative and popular VLP for several applications - following cellular uptake. By exploiting the available functional handles on the viral surface, we have orthogonally installed the known FRET pair, FITC and Rhodamine B, to gain insight of the particle’s behavior in vitro. Based on these data, we believe VLPs undergo aggregation in addition to the anticipated proteolysis within a few hours of cellular uptake.</p></div></div></div>

The P-MAPA immunomodulator partially prevents apoptosis induced by Zika virus infection in THP-1 cells

2020 ◽  
Vol 21 ◽  
Author(s):  
Morganna C. Lima ◽  
Elisa A. N. Azevedo ◽  
Clarice N. L. de Morais ◽  
Larissa I. O. de Sousa ◽  
Bruno M. Carvalho ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Virus Infection ◽  
Virus Replication ◽  
Zika Virus ◽  
Mammalian Cells ◽  
Caspase 3 ◽  
Neurological Complications ◽  
Zika Virus Infection

Background: Zika virus is an emerging arbovirus of global importance. ZIKV infection is associated with a range of neurological complications such as the Congenital Zika Syndrome and Guillain Barré Syndrome. Despite the magnitude of recent outbreaks, there is no specific therapy to prevent or to alleviate disease pathology. Objective: To investigate the role of P-MAPA immunomodulator in Zika-infected THP-1 cells. Methods: THP-1 cells were subjected at Zika virus infection (Multiplicity of Infection = 0.5) followed by treatment with P-MAPA for until 96 hours post-infection. After that, the cell death was analyzed by annexin+/ PI+ and caspase 3/ 7+ staining by flow cytometry. In addition, the virus replication and cell proliferation were accessed by RT-qPCR and Ki67 staining, respectively. Results: We demonstrate that P-MAPA in vitro treatment significantly reduces Zika virus-induced cell death and caspase-3/7 activation on THP-1 infected cells, albeit it has no role in virus replication and cell proliferation. Conclusions: Our study reveals that P-MAPA seems to be a satisfactory alternative to inhibits the effects of Zika virus infection in mammalian cells.

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