scholarly journals A Replication-Defective Gammaherpesvirus Efficiently Establishes Long-Term Latency in Macrophages but Not in B Cells In Vivo

2008 ◽  
Vol 82 (17) ◽  
pp. 8500-8508 ◽  
Author(s):  
Haiyan Li ◽  
Kazufumi Ikuta ◽  
John W. Sixbey ◽  
Scott A. Tibbetts

ABSTRACT Murine gammaherpesvirus 68 (γHV68 or MHV68) is genetically related to the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), providing a useful system for in vivo studies of the virus-host relationship. To begin to address fundamental questions about the mechanisms of the establishment of gammaherpesvirus latency, we previously generated a replication-defective γHV68 lacking the expression of the single-stranded DNA binding protein encoded by orf6. In work presented here, we demonstrate that this mutant virus established a long-term infection in vivo that was molecularly identical to wild-type virus latency. Thus, despite the absence of an acute phase of lytic replication, the mutant virus established a chronic infection in which the viral genome (i) was maintained as an episome and (ii) expressed latency-associated, but not lytic replication-associated, genes. Macrophages purified from mice infected with the replication-defective virus harbored viral genome at a frequency that was nearly identical to that of wild-type γHV68; however, the frequency of B cells harboring viral genome was greatly reduced in the absence of lytic replication. Thus, this replication-defective gammaherpesvirus efficiently established in vivo infection in macrophages that was molecularly indistinguishable from wild-type virus latency. These data point to a critical role for lytic replication or reactivation in the establishment or maintenance of latent infection in B cells.

2006 ◽  
Vol 80 (3) ◽  
pp. 1592-1598 ◽  
Author(s):  
Janice M. Moser ◽  
Michael L. Farrell ◽  
Laurie T. Krug ◽  
Jason W. Upton ◽  
Samuel H. Speck

ABSTRACT The gammaherpesvirus immediate-early genes are critical regulators of virus replication and reactivation from latency. Rta, encoded by gene 50, serves as the major transactivator of the lytic program and is highly conserved among all the gammaherpesviruses, including Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, and murine gammaherpesvirus 68 (γHV68). Introduction of a translation stop codon in γHV68 gene 50 (gene 50.stop γHV68) demonstrated that Rta is essential for virus replication in vitro. To investigate the role that virus replication plays in the establishment and maintenance of latency, we infected mice with gene 50.stop γHV68. Notably, the gene 50.stop virus established a long-term infection in lung B cells following intranasal infection of mice but was unable to establish latency in the spleen. This complete block in the establishment of latency in the spleen was also seen when lytic virus production was inhibited by treating mice infected with wild-type virus with the antiviral drug cidofovir, implicating virus replication and not an independent function of Rta in the establishment of splenic latency. Furthermore, we showed that gene 50.stop γHV68 was unable to prime the immune system and was unable to protect against a challenge with wild-type γHV68, despite its ability to chronically infect lung B cells. These data indicate gammaherpesviruses that are unable to undergo lytic replication in vivo may not be viable vaccine candidates despite the detection of cells harboring viral genome at late times postinfection.


2000 ◽  
Vol 74 (7) ◽  
pp. 3353-3365 ◽  
Author(s):  
Chi-Long Lin ◽  
Che-Sheng Chung ◽  
Hans G. Heine ◽  
Wen Chang

ABSTRACT An immunodominant antigen, p35, is expressed on the envelope of intracellular mature virions (IMV) of vaccinia virus. p35 is encoded by the viral late gene H3L, but its role in the virus life cycle is not known. This report demonstrates that soluble H3L protein binds to heparan sulfate on the cell surface and competes with the binding of vaccinia virus, indicating a role for H3L protein in IMV adsorption to mammalian cells. A mutant virus defective in expression of H3L (H3L−) was constructed; the mutant virus has a small plaque phenotype and 10-fold lower IMV and extracellular enveloped virion titers than the wild-type virus. Virion morphogenesis is severely blocked and intermediate viral structures such as viral factories and crescents accumulate in cells infected with the H3L− mutant virus. IMV from the H3L− mutant virus are somewhat altered and less infectious than wild-type virions. However, cells infected by the mutant virus form multinucleated syncytia after low pH treatment, suggesting that H3L protein is not required for cell fusion. Mice inoculated intranasally with wild-type virus show high mortality and severe weight loss, whereas mice infected with H3L− mutant virus survive and recover faster, indicating that inactivation of the H3L gene attenuates virus virulence in vivo. In summary, these data indicate that H3L protein mediates vaccinia virus adsorption to cell surface heparan sulfate and is important for vaccinia virus infection in vitro and in vivo. In addition, H3L protein plays a role in virion assembly.


1998 ◽  
Vol 72 (7) ◽  
pp. 5351-5359 ◽  
Author(s):  
Thandavarayan Nagashunmugam ◽  
John Lubinski ◽  
Liyang Wang ◽  
Lester T. Goldstein ◽  
Benjamin S. Weeks ◽  
...  

ABSTRACT Herpes simplex virus (HSV) glycoproteins gE and gI form an immunoglobulin G (IgG) Fc receptor (FcγR) that binds the Fc domain of human anti-HSV IgG and inhibits Fc-mediated immune functions in vitro. gE or gI deletion mutant viruses are avirulent, probably because gE and gI are also involved in cell-to-cell spread. In an effort to modify FcγR activity without affecting other gE functions, we constructed a mutant virus, NS-gE339, that has four amino acids inserted into gE within the domain homologous to mammalian IgG FcγRs. NS-gE339 expresses gE and gI, is FcγR−, and does not participate in antibody bipolar bridging since it does not block activities mediated by the Fc domain of anti-HSV IgG. In vivo studies were performed with mice because the HSV-1 FcγR does not bind murine IgG; therefore, the absence of an FcγR should not affect virulence in mice. NS-gE339 causes disease at the skin inoculation site comparably to wild-type and rescued viruses, indicating that the FcγR− mutant virus is pathogenic in animals. Mice were passively immunized with human anti-HSV IgG and then infected with mutant or wild-type virus. We postulated that the HSV-1 FcγR should protect wild-type virus from antibody attack. Human anti-HSV IgG greatly reduced viral titers and disease severity in NS-gE339-infected animals while having little effect on wild-type or rescued virus. We conclude that the HSV-1 FcγR enables the virus to evade antibody attack in vivo, which likely explains why antibodies are relatively ineffective against HSV infection.


2010 ◽  
Vol 84 (18) ◽  
pp. 9427-9438 ◽  
Author(s):  
Aeron C. Hurt ◽  
Siti Sarah Nor'e ◽  
James M. McCaw ◽  
Helen R. Fryer ◽  
Jennifer Mosse ◽  
...  

ABSTRACT To determine the relative fitness of oseltamivir-resistant strains compared to susceptible wild-type viruses, we combined mathematical modeling and statistical techniques with a novel in vivo “competitive-mixtures” experimental model. Ferrets were coinfected with either pure populations (100% susceptible wild-type or 100% oseltamivir-resistant mutant virus) or mixed populations of wild-type and oseltamivir-resistant influenza viruses (80%:20%, 50%:50%, and 20%:80%) at equivalent infectivity titers, and the changes in the relative proportions of those two viruses were monitored over the course of the infection during within-host and over host-to-host transmission events in a ferret contact model. Coinfection of ferrets with mixtures of an oseltamivir-resistant R292K mutant A(H3N2) virus and a R292 oseltamivir-susceptible wild-type virus demonstrated that the R292K mutant virus was rapidly outgrown by the R292 wild-type virus in artificially infected donor ferrets and did not transmit to any of the recipient ferrets. The competitive-mixtures model was also used to investigate the fitness of the seasonal A(H1N1) oseltamivir-resistant H274Y mutant and showed that within infected ferrets the H274Y mutant virus was marginally outgrown by the wild-type strain but demonstrated equivalent transmissibility between ferrets. This novel in vivo experimental method and accompanying mathematical analysis provide greater insight into the relative fitness, both within the host and between hosts, of two different influenza virus strains compared to more traditional methods that infect ferrets with only pure populations of viruses. Our statistical inferences are essential for the development of the next generation of mathematical models of the emergence and spread of oseltamivir-resistant influenza in human populations.


2016 ◽  
Vol 90 (6) ◽  
pp. 3229-3242 ◽  
Author(s):  
Young-Eui Kim ◽  
Se Eun Oh ◽  
Ki Mun Kwon ◽  
Chan Hee Lee ◽  
Jin-Hyun Ahn

ABSTRACTHuman cytomegalovirus (HCMV) protein pUL48 is closely associated with the capsid and has a deubiquitinating protease (DUB) activity in its N-terminal region. Although this DUB activity moderately increases virus replication in cultured fibroblast cells, the requirements of the N-terminal region of pUL48 in the viral replication cycle are not fully understood. In this study, we characterized the recombinant viruses encoding UL48(ΔDUB/NLS), which lacks the DUB domain and the adjacent nuclear localization signal (NLS), UL48(ΔDUB), which lacks only the DUB, and UL48(Δ360–1200), which lacks the internal region (amino acids 360 to 1200) downstream of the DUB/NLS. While ΔDUB/NLS and Δ360–1200 mutant viruses did not grow in fibroblasts, the ΔDUB virus replicated to titers 100-fold lower than those for wild-type virus and showed substantially reduced viral gene expression at low multiplicities of infection. The DUB domain contained ubiquitination sites, and DUB activity reduced its own proteasomal degradation intrans. Deletion of the DUB domain did not affect the nuclear and cytoplasmic localization of pUL48, whereas the internal region (360–1200) was necessary for cytoplasmic distribution. In coimmunoprecipitation assays, pUL48 interacted with three tegument proteins (pUL47, pUL45, and pUL88) and two capsid proteins (pUL77 and pUL85) but the DUB domain contributed to only pUL85 binding. Furthermore, we found that the ΔDUB virus showed reduced virion stability and less efficiently delivered its genome into the cell than the wild-type virus. Collectively, our results demonstrate that the N-terminal DUB domain of pUL48 contributes to efficient viral growth by regulating its own stability and promoting virion stabilization and virus entry.IMPORTANCEHCMV pUL48 and its herpesvirus homologs play key roles in virus entry, regulation of immune signaling pathways, and virion assembly. The N terminus of pUL48 contains the DUB domain, which is well conserved among all herpesviruses. Although studies using the active-site mutant viruses revealed that the DUB activity promotes viral growth, the exact role of this region in the viral life cycle is not fully understood. In this study, using the mutant virus lacking the entire DUB domain, we demonstrate that the DUB domain of pUL48 contributes to viral growth by regulating its own stability via autodeubiquitination and promoting virion stability and virus entry. This report is the first to demonstrate the characteristics of the mutant virus with the entire DUB domain deleted, which, along with information on the functions of this region, is useful in dissecting the functions associated with pUL48.


2015 ◽  
Vol 90 (3) ◽  
pp. 1169-1177 ◽  
Author(s):  
Jason Porta ◽  
Vidya Mangala Prasad ◽  
Cheng-I Wang ◽  
Wataru Akahata ◽  
Lisa F. P. Ng ◽  
...  

ABSTRACTChikungunya virus is a positive-stranded RNA alphavirus. Structures of chikungunya virus-like particles in complex with strongly neutralizing antibody Fab fragments (8B10 and 5F10) were determined using cryo-electron microscopy and X-ray crystallography. By fitting the crystallographically determined structures of these Fab fragments into the cryo-electron density maps, we show that Fab fragments of antibody 8B10 extend radially from the viral surface and block receptor binding on the E2 glycoprotein. In contrast, Fab fragments of antibody 5F10 bind the tip of the E2 B domain and lie tangentially on the viral surface. Fab 5F10 fixes the B domain rigidly to the surface of the virus, blocking exposure of the fusion loop on glycoprotein E1 and therefore preventing the virus from becoming fusogenic. Although Fab 5F10 can neutralize the wild-type virus, it can also bind to a mutant virus without inhibiting fusion or attachment. Although the mutant virus is no longer able to propagate by extracellular budding, it can, however, enter the next cell by traveling through junctional complexes without being intercepted by a neutralizing antibody to the wild-type virus, thus clarifying how cell-to-cell transmission can occur.IMPORTANCEAlphaviral infections are transmitted mainly by mosquitoes. Chikungunya virus (CHIKV), which belongs to theAlphavirusgenus, has a wide distribution in the Old World that has expanded in recent years into the Americas. There are currently no vaccines or drugs against alphaviral infections. Therefore, a better understanding of CHIKV and its associated neutralizing antibodies will aid in the development of effective treatments.


2006 ◽  
Vol 80 (1) ◽  
pp. 440-450 ◽  
Author(s):  
John W. Balliet ◽  
Priscilla A. Schaffer

ABSTRACT In vitro studies of herpes simplex virus type 1 (HSV-1) viruses containing mutations in core sequences of the viral origins of DNA replication, oriL and oriS, that eliminate the ability of these origins to initiate viral-DNA synthesis have demonstrated little or no effect on viral replication in cultured cells, leading to the conclusion that the two types of origins are functionally redundant. It remains unclear, therefore, why origins that appear to be redundant are maintained evolutionarily in HSV-1 and other neurotropic alphaherpesviruses. To test the hypothesis that oriL and oriS have distinct functions in the HSV-1 life cycle in vivo, we determined the in vivo phenotypes of two mutant viruses, DoriL-ILR and DoriS-I, containing point mutations in oriL and oriS site I, respectively, that eliminate origin DNA initiation function. Following corneal inoculation of mice, tear film titers of DoriS-I were reduced relative to wild-type virus. In all other tests, however, DoriS-I behaved like wild-type virus. In contrast, titers of DoriL-ILR in tear film, trigeminal ganglia (TG), and hindbrain were reduced and mice infected with DoriL-ILR exhibited greatly reduced mortality relative to wild-type virus. In the TG explant and TG cell culture models of reactivation, DoriL-ILR reactivated with delayed kinetics and, in the latter model, with reduced efficiency relative to wild-type virus. Rescuant viruses DoriL-ILR-R and DoriS-I-R behaved like wild-type virus in all tests. These findings demonstrate that functional differences exist between oriL and oriS and reveal a prominent role for oriL in HSV-1 pathogenesis.


2019 ◽  
Vol 93 (22) ◽  
Author(s):  
Tomokazu Tamura ◽  
Manabu Igarashi ◽  
Bazarragchaa Enkhbold ◽  
Tatsuya Suzuki ◽  
Masatoshi Okamatsu ◽  
...  

ABSTRACT Recombinant viruses possessing reporter proteins have been generated for virus research. In the case of the family Flaviviridae, we recently generated recombinant viruses, including the hepatitis C virus of the genus Hepacivirus, Japanese encephalitis virus (JEV) of the genus Flavivirus, and bovine viral diarrhea virus of the genus Pestivirus; all three viruses possess an 11-amino-acid subunit derived from NanoLuc luciferase (HiBiT). Here, we further developed the recombinant viruses and investigated their utility in vivo. Recombinant viruses harboring HiBiT in the E, NS1, or NS3 protein constructed based on the predicted secondary structure, solvent-accessible surface area, and root mean square fluctuation of the proteins exhibited comparable replication to that of the wild-type virus in vitro. The recombinant JEV carrying HiBiT in the NS1 protein exhibited propagation in mice comparable to that of the parental virus, and propagation of the recombinant was monitored by the luciferase activity. In addition, the recombinants of classical swine fever virus (CSFV) possessing HiBiT in the Erns or E2 protein also showed propagation comparable to that of the wild-type virus. The recombinant CSFV carrying HiBiT in Erns exhibited similar replication to the parental CSFV in pigs, and detection of viral propagation of this recombinant by luciferase activity was higher than that by quantitative PCR (qPCR). Taken together, these results demonstrated that the reporter Flaviviridae viruses generated herein are powerful tools for elucidating the viral life cycle and pathogeneses and provide a robust platform for the development of novel antivirals. IMPORTANCE In vivo applications of reporter viruses are necessary to understand viral pathogenesis and provide a robust platform for antiviral development. In developing such applications, determination of an ideal locus to accommodate foreign genes is important, because insertion of foreign genes into irrelevant loci can disrupt the protein functions required for viral replication. Here, we investigated the criteria to determine ideal insertion sites of foreign genes from the protein structure of viral proteins. The recombinant viruses generated by our criteria exhibited propagation comparable to that of parental viruses in vivo. Our proteomic approach based on the flexibility profile of viral proteins may provide a useful tool for constructing reporter viruses, including Flaviviridae viruses.


Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 44
Author(s):  
Autumn T. LaPointe ◽  
Kevin J Sokoloski

Alphaviruses are positive-sense RNA arthropod-borne viruses that represent a significant threat to public health. During alphaviral replication, significant quantities of viral genomic RNAs that lack a canonical 5’ cap structure are produced and packaged into viral particles, despite the fact that the noncapped genomes cannot be translated and are essentially noninfectious. Previously, we have reported that the capping efficiency of nsP1, the alphaviral capping enzyme, of Sindbis virus (SINV) could be modulated via point mutation. It was found that increasing RNA capping efficiency led to decreased viral growth kinetics via decreased particle production, despite increased innate immune evasion, whereas decreasing capping efficiency led to wild-type growth kinetics and particle production. This led to the conclusion that the noncapped viral RNAs meaningfully contribute to the biology of alphaviral infections at the molecular level. To determine the importance of the noncapped viral RNAs in vivo, we characterized the impact of altered capping efficiency in a murine model of infection utilizing a neurovirulent strain of SINV. Mice infected with the nsP1 mutant with decreased capping exhibited wild-type rates of mortality, weight loss, and neurological symptoms. Conversely, the mice infected with the increased capping nsP1 mutant showed significantly reduced mortality and morbidity compared to mice infected with the wild-type virus. Interestingly, viral titers in the ankle, serum, and brain were equivalent between the wild-type virus and the two mutant viruses. Importantly, examination of the brain tissue revealed that mice infected with the increased capping mutant had significantly reduced immune cell infiltration and expression of proinflammatory cytokines compared to the decreased capping mutant and wild-type virus. Collectively, these data indicate that the noncapped viral RNAs have important roles during the early and late stages of alphaviral infection and suggest a novel mechanism by which noncapped viral RNA aids in viral pathogenesis.


2004 ◽  
Vol 78 (16) ◽  
pp. 8582-8592 ◽  
Author(s):  
Audrey Esclatine ◽  
Brunella Taddeo ◽  
Bernard Roizman

ABSTRACT Herpes simplex virus 1 causes a shutoff of cellular protein synthesis through the degradation of RNA that is mediated by the virion host shutoff (Vhs) protein encoded by the UL41 gene. We reported elsewhere that the Vhs-dependent degradation of RNA is selective, and we identified RNAs containing AU-rich elements (AREs) that were upregulated after infection but degraded by deadenylation and progressive 3′-to-5′ degradation. We also identified upregulated RNAs that were not subject to Vhs-dependent degradation (A. Esclatine, B. Taddeo, L. Evans, and B. Roizman, Proc. Natl. Acad. Sci. USA 101:3603-3608, 2004). Among the latter was the RNA encoding tristetraprolin, a protein that binds AREs and is known to be associated with the degradation of RNAs containing AREs. Prompted by this observation, we examined the status of the ARE binding proteins tristetraprolin and TIA-1/TIAR in infected cells. We report that tristetraprolin was made and accumulated in the cytoplasm of wild-type virus-infected human foreskin fibroblasts as early as 2 h and in HEp-2 cells as early as 6 h after infection. The amounts of tristetraprolin that accumulated in the cytoplasm of cells infected with a mutant virus lacking UL41 were significantly lower than those in wild-type virus-infected cells. The localization of tristetraprolin was not modified in cells infected with a mutant lacking the gene encoding infected cell protein 4 (ICP4). TIA-1 and TIAR are two other proteins that are associated with the regulation of ARE-containing RNAs and that normally reside in nuclei. In infected cells, they started to accumulate in the cytoplasm after 6 h of infection. In cells infected with the mutant virus lacking UL41, TIA-1/TIAR accumulated in the cytoplasm in granular structures reminiscent of stress granules in a significant percentage of the cells. In addition, an antibody to tristetraprolin coprecipitated the Vhs protein from lysates of cells late in infection. The results indicate that the Vhs-dependent degradation of ARE-containing RNAs correlates with the transactivation, cytoplasmic accumulation, and persistence of tristetraprolin in infected cells.


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