2016 Vol.31(3)
Human cytomegalovirus (HCMV), a member of β human herpesvirus, can be life-threatening for immunocompromised individuals (such as patients with AIDS and organ transplant recipients) and neonates. It may cause cytomegalic inclusion disease and brain development disorders in newborns, and sensorineural hearing loss in infants who are asymptomatic at birth. HCMV can infect many types of cell, however, whether Multipotent mesenchymal stromal cells (MSCs) support HCMV replication and the infection status of HCMV in MSCs remain unclear. In this issue, Qiao et al. investigated the infection ability and status of HCMV in MSCs (isolated from Wharton’s jelly of the human umbilical cord), and found that the MSCs were fully permissive for HCMV infection. The cover shows the efficiency of HCMV genome replication in MSCs. See page 219-228 for details.
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CRISPR-Cas-like system in giant viruses: why MIMIVIRE is not likely to be an adaptive immune system
2016, 31(3): 193 doi: 10.1007/s12250-016-3801-x
Published: 13 June 2016
Giant viruses from the Mimiviridae family (Mimivirus, Megavirus, etc.) replicate inside their Acanthamoeba host by the mean of a large intracytoplasmic virion factory within which DNA transcription and replication take place using the virus encoded machineries. Members of the Mimiviridae have been isolated in association with much smaller dsDNA viruses called 'virophages' that replicate within the virion factory, behaving as parasites of the giant virus. In a recent work Levasseur et al. (2016) used a silencing approach to identify candidate genes possibly involved in the inhibition of the Zamilon virophage in a specific clade of Mimiviridae. Based on the presence of four copies of a short Zamilon sequence in one of the Mimivirus candidate gene, the authors proposed that resistance to virophages was conferred by a CRISPR-Cas-like system (called MIMIVIRE). Here we dispute this interpretation on the ground that 1) the simultaneous and co-localized replication of the virophage and Mimivirus genomes makes the acquisition of a nucleic acid-based immunity unlikely, 2) the Zamilonlike sequence allegedly acquired by Mimivirus are neither regularly spaced nor flanked by recognizable repeats, 3) the corresponding Zamilon sequence is devoid of distinct flanking sequences that may serve as Protospacer Adjacent Motifs (PAM) discriminating between the virophage and its host. We propose a simpler protein-based interaction model that explains the observed phenomena without having to extend the realm of adaptive immunity to the world of eukaryotic viruses, a revolutionary step that would require stronger experimental evidences.
Towards a coherent nomenclature of plant viruses
2016, 31(3): 197 doi: 10.1007/s12250-016-3741-5
Published: 21 March 2016
The International Committee on Taxonomy of Viruses (ICTV) has the decree to set the rules for the classification and naming of viruses. The species is the lowest level considered in the taxonomic hierarchy. In general, virus species are named according to the structure “ and the word ‘virus’”. A typical example is Tobacco mosaic virus [Genus: Tobamovirus]. With a few exceptions, this convention has been generally well accepted. As there is always room for improvement, virus nomenclature (King et al., 2011) can be managed more efficiently through several ways.
Stability of HIV-1 subtype B and C Tat is associated with variation in the carboxyl-terminal region
2016, 31(3): 199 doi: 10.1007/s12250-016-3681-0
Received: 20 November 2015
Accepted: 01 March 2016
Published: 21 March 2016
The multifunctional trans-activator Tat is an essential regulatory protein for HIV-1 replication and is characterized by high sequence diversity. Numerous experimental studies have examined Tat in HIV-1 subtype B, but research on subtype C Tat is lacking, despite the high prevalence of infections caused by subtype C worldwide. We hypothesized that amino acid differences contribute to functional differences among Tat proteins. In the present study, we found that subtype B NL4-3 Tat and subtype C isolate HIV1084i Tat exhibited differences in stability by overexpressing the fusion protein Tat-Flag. In addition, 1084i Tat can activate LTR and NF-κB more efficiently than NL4-3 Tat. In analyses of the activities of the truncated forms of Tat, we found that the carboxylterminal region of Tat regulates its stability and transactivity. According to our results, we speculated that the differences in stability between B-Tat and C-Tat result in differences in transactivation ability.
The V1 region of gp120 is preferentially selected during SIV/HIV transmission and is indispensable for envelope function and virus infection
2016, 31(3): 207 doi: 10.1007/s12250-016-3725-5
Received: 11 January 2016
Accepted: 28 March 2016
Published: 19 April 2016
A transmission bottleneck occurs during each human immunodeficiency virus (HIV) transmission event, which allows only a few viruses to establish new infection. However, the genetic characteristics of the transmitted viruses that are preferentially selected have not been fully elucidated. Here, we analyzed amino acids changes in the envelope protein during simian immunodeficiency virus (SIV)/HIV deep transmission history and current HIV evolution within the last 15–20 years. Our results confirmed that the V1V2 region of gp120 protein, particularly V1, was preferentially selected. A shorter V1 region was preferred during transmission history, while during epidemic, HIV may evolve to an expanded V1 region gradually and thus escape immune recognition. We then constructed different HIV-1 V1 mutants using different HIV-1 subtypes to elucidate the role of the V1 region in envelope function. We found that the V1 region, although highly variable, was indispensable for virus entry and infection, probably because V1 deletion mutants exhibited impaired processing of gp160 into mature gp120 and gp41. Additionally, the V1 region affected Env incorporation. These results indicated that the V1 region played a critical role in HIV transmission and infection.
Multipotent mesenchymal stromal cells are fully permissive for human cytomegalovirus infection
2016, 31(3): 219 doi: 10.1007/s12250-016-3754-0
Received: 24 February 2016
Accepted: 05 April 2016
Published: 21 April 2016
Congenital human cytomegalovirus (HCMV) infection is a leading infectious cause of birth defects. Previous studies have reported birth defects with multiple organ maldevelopment in congenital HCMV-infected neonates. Multipotent mesenchymal stromal cells (MSCs) are a group of stem/progenitor cells that are multi-potent and can self-renew, and they play a vital role in multiorgan formation. Whether MSCs are susceptible to HCMV infection is unclear. In this study, MSCs were isolated from Wharton’s jelly of the human umbilical cord and identified by their plastic adherence, surface marker pattern, and differentiation capacity. Then, the MSCs were infected with the HCMV Towne strain, and infection status was assessed via determination of viral entry, replication initiation, viral protein expression, and infectious virion release using western blotting, immunofluorescence assays, and plaque forming assays. The results indicate that the isolated MSCs were fully permissive for HCMV infection and provide a preliminary basis for understanding the pathogenesis of HCMV infection in non-nervous system diseases, including multi-organ malformation during fetal development.
Plutella xylostella granulovirus late gene promoter activity in the context of the Autographa californica multiple nucleopolyhedrovirus genome
2016, 31(3): 229 doi: 10.1007/s12250-015-3675-3
Received: 01 November 2015
Accepted: 08 April 2016
Published: 13 May 2016
Within Baculoviridae, little is known about the molecular mechanisms of replication in betabaculoviruses, despite extensive studies in alphabaculoviruses. In this study, the promoters of nine late genes of the betabaculovirus Plutella xylostella granulovirus (PlxyGV) were cloned into a transient expression vector and the alphabaculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) genome, and compared with homologous late gene promoters of AcMNPV in Sf9 cells. In transient expression assays, all PlxyGV late promoters were activated in cells transfected with the individual reporter plasmids together with an AcMNPV bacmid. In infected cells, reporter gene expression levels with the promoters of PlxyGV e18 and AcMNPV vp39 and gp41 were significantly higher than those of the corresponding AcMNPV or PlxyGV promoters, which had fewer late promoter motifs. Observed expression levels were lower for the PlxyGV p6.9, pk1, gran, p10a, and p10b promoters than for the corresponding AcMNPV promoters, despite equal numbers of late promoter motifs, indicating that species-specific elements contained in some late promoters were favored by the native viral RNA polymerases for optimal transcription. The 8-nt sequence TAAATAAG encompassing the ATAAG motif was conserved in the AcMNPV polh, p10, and pk1 promoters. The 5-nt sequence CAATT located 4 or 5 nt upstream of the T/ATAAG motif was conserved in the promoters of PlxyGV gran, p10c, and pk1. The results of this study demonstrated that PlxyGV late gene promoters could be effectively activated by the RNA polymerase from AcMNPV, implying that late gene expression systems are regulated by similar mechanisms in alphabaculoviruses and betabaculoviruses.
Characterization of the viral fibroblast growth factor homolog of Helicoverpa armigera single nucleopolyhedrovirus
2016, 31(3): 240 doi: 10.1007/s12250-016-3710-z
Received: 27 December 2015
Accepted: 07 April 2016
Published: 28 April 2016
Fibroblast growth factor (FGF) is found throughout multicellular organisms; however, fgf homologs (vfgf) have only been identified among viruses in lepidopteran baculoviruses. The function of vFGFs from Group I alphabaculoviruses, including Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Bombyx mori nucleopolyhedrovirus (BmNPV), involves accelerated killing of infected larvae by both viruses. The vFGF of Group II alphabaculovirus is structurally different from that of Group I alphabaculovirus, with a larger C-terminal region and additional N-linked glycosylation sites. In this study, we characterized the Group II alphabaculovirus vFGF of Helicoverpa armigera single nucleopolyhedrovirus (HearNPV). The transcription and expression of vfgf was detected at 3 h and 16 h post-infection in HearNPV-infected cells. To further study vFGF function, we constructed vfgf-knockout and -repaired HearNPV bacmids and investigated their affect in both cultured cells and insects. Deletion of vfgf had no effect on budded-virus production or viral DNA replication in cultured HzAM1 cells. However, bioassays showed that HearNPV vfgf deletion significantly increased the median lethal dose and delayed the median lethal time by ~12 h in the host insect when the virus was delivered orally. These results suggested that vFGF is an important virulent factor for HearNPV infection and propagation in vivo.
Differential gene expression in porcine SK6 cells infected with wild-type and SAP domain-mutant foot-and-mouth disease virus
2016, 31(3): 249 doi: 10.1007/s12250-015-3709-x
Received: 26 December 2015
Accepted: 03 March 2016
Published: 08 April 2016
Foot-and-mouth disease virus (FMDV) is the causative agent of a highly contagious disease in livestock. The viral proteinase Lpro of FMDV is involved in pathogenicity, and mutation of the Lpro SAP domain reduces FMDV pathogenicity in pigs. To determine the gene expression profiles associated with decreased pathogenicity in porcine cells, we performed transcriptome analysis using next-generation sequencing technology and compared differentially expressed genes in SK6 cells infected with FMDV containing Lpro with either a wild-type or mutated version of the SAP domain. This analysis yielded 1,853 genes that exhibited a ≥ 2-fold change in expression and was validated by real-time quantitative PCR detection of several differentially expressed genes. Many of the differentially expressed genes correlated with antiviral responses corresponded to genes associated with transcription factors, immune regulation, cytokine production, inflammatory response, and apoptosis. Alterations in gene expression profiles may be responsible for the variations in pathogenicity observed between the two FMDV variants. Our results provided genes of interest for the further study of antiviral pathways and pathogenic mechanisms related to FMDV Lpro.
Outbreak of human astrovirus 1 lineage 1d in a childcare center in China
2016, 31(3): 258 doi: 10.1007/s12250-015-3701-5
Published: 02 March 2016
Astrovirus is an enteric virus associated with sporadic diarrhea or large outbreaks of gastroenteritis (Mendez et al., 2013). Until 2008, human astroviruses (HAstVs) were classified into eight serotypes—HAstV-1 to HAstV- 8—based on the reactivity of their capsid protein with type-specific antibodies. Among these serotypes, HAstV-1 is the most prevalent globally. However, some divergent new astroviruses (MLB1/MLB2, VA1/VA2/VA3, and HMO A/B/C) have been discovered recently in stool samples of patients with and without diarrhea (De Benedictis et al., 2011).
Construction of an infectious cDNA clone of Tembusu virus isolated from breeder Peking ducks
2016, 31(3): 262 doi: 10.1007/s12250-015-3678-0
Published: 15 January 2016
Since April 2010, an outbreak of a new disease has elicited symptoms of high fever, loss of appetite, and reduction in egg production in layer ducks in eastern China; this phenomenon has now spread throughout China (Cao et al., 2011; Su et al., 2011). The causative agent of the disease was identified as Tembusu virus (TMUV), which was classified into the genus Flavivirus, family Flaviviridae. The TMUV virion is enveloped and contains a 10, 990 nt single-stranded, positive-sense RNA genome which contains a long open reading frame. The reading frame encodes a polyprotein that is possessed into three structural (Capsid, prM and E) and seven non-structural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins by viral-encoded proteases (Tang et al., 2012; Yun et al., 2012). TMUV isolated from poultry (including chicken, duck and goose), field birds, and mosquitos, can trigger neurological symptoms and even death in mice (Liu et al., 2012; Li et al., 2013a; Liu et al., 2013; Tang et al., 2013; Tang et al., 2015). To date, the elements of TMUV required for viral replication and virulence have not been definitively determined. Reverse genetics is an effective molecular biology technique to determine the function of genomic elements responsible for the replication and virulence in positivestrand RNA viruses. Infectious cDNA clones and recombinant progeny of flaviviruses including Japanese encephalitis virus, West Nile virus, Dengue virus, Yellow fever virus, Tick-borne encephalitis virus are available. There are two major strategies to construct infectious cDNA clones of animal viruses. For example, a duck TMUV infectious cDNA clone that was transcribed into RNA via in vitro transcription has been reported (Li et al., 2013b). However, no infectious cDNA clones based on a DNA-launching strategy have been constructed and produced for progeny virus.
Recombinant canarypox virus expressing the VP2 protein of infectious bursal disease virus induces protection in vaccinated SPF chickens
2016, 31(3): 266 doi: 10.1007/s12250-015-3680-6
Published: 18 March 2016
Infectious bursal disease virus (IBDV) causes infectious bursal disease, a highly contagious immunosuppressive disease that affects young chickens and causes economic losses in the poultry industry worldwide. IBDV replicates mainly in actively dividing B lymphocytes within the bursa of Fabricius (BF), leading to immunosuppression in affected flocks (Mahgoub et al., 2012). Viral protein 2 (VP2), the only structural component of the IBDV icosahedral capsid, is the major antigen responsible for inducing protective immunity in the host (Mahgoub et al., 2012).
Diagnosis and phylogenetic analysis of orf virus in Aleppo and Saanen goats from an outbreak in Turkey
2016, 31(3): 270 doi: 10.1007/s12250-015-3684-2
Published: 20 January 2016
In this study, multiplex PCR was used to amplify both the B2L gene partial coding region and a housekeeping gene. A substantial amount of research has been conducted on the B2L gene, and this presents opportunities for comparisons between different strains around the world. Field strains have been compared with human, sheep, and goat orf viruses and with other parapoxviruses such as PCPV and BPSV. Although the presence of the virus in Turkey was previously reported, its relationship with other orf viruses around the world has not yet been demonstrated, in contrast to parapoxvirus infections of cattle and humans in Turkey (Karakas et al., 2013; Oguzoglu et al., 2014). This study provides diagnostic and molecular characterization data for the economically damaging parapoxvirus infection that circulated among goat flocks in Turkey in the 2013–2014 lambing season.
Characterization of a recombinant Akabane mutant virus with knockout of a nonstructural protein NSs in a pregnant goat model
2016, 31(3): 274 doi: 10.1007/s12250-015-3704-2
Published: 06 April 2016
Akabane virus (AKAV), an orthobunyavirus, is transmitted primarily by biting midges and is widely distributed throughout the world except the Europe. AKAV was first isolated from mosquitoes in Japan (Oya et al., 1961). Although pregnant cows, ewes, and goats infected with AKAV exhibit no clinical signs of disease, in utero infections result in abortion, premature birth, stillbirth, and congenital deformities such as arthrogryposis-hydranencephaly syndrome (Kurogi et al., 1976), causing economic losses in the livestock industry. The live, attenuated vaccine strain, TS-C2, was derived from the OBE-1 strain as a temperature sensitive mutant (Kurogi et al., 1979). Although vaccination has reduced the prevalence of the disease, antigenic and pathogenic variants of AKAV have been isolated (Lee et al., 2002; Ogawa et al., 2007a); for example, a variant Iriki strain was isolated from a calf with nonsuppurative encephalitis and neurological symptoms in Japan (Miyazato et al., 1989) and it shows low antigenic cross-reactivity with the reference strain in neutralization tests (Akashi and Inaba, 1997). Therefore, it is necessary to reconsider the vaccination strategy to effectively control the disease. Here we evaluated characters of a mutant virus with knockout of a nonstructural protein NSs, which acts as type I interferon antagonist and is involved in the regulation of host protein synthesis (Weber et al., 2002), by experimentally infecting pregnant goats. The pregnant goat model might be useful for AKAV studies, as suggested by previous reports of experimental transplacental infection of caprine fetuses (Kurogi et al., 1977).
