Identification of new protein kinase-related genes in three herpesviruses, herpes simplex virus, varicella-zoster virus, and Epstein-Barr virus.

By using amino acid sequence patterns (motifs) diagnostic of conserved regions within the catalytic domains of protein kinases, homologous open reading frames of three herpesviruses were identified as protein kinase-related genes. The three sequences, herpes simplex virus gene UL13, varicella-zoster virus gene 47, and Epstein-Barr virus gene BGLF4, resemble serine/threonine kinases rather than tyrosine kinases.     

Sialylatin of glycoproteins of murine mammary tumor virus, murine leukemia virus, and Mason-Pfizer monkey virus.

Neuraminidase treatment of mouse mammary tumor virus, Rauscher murine leukemia virus, and Mason-Pfizer monkey virus resulted in loss of their capacity to inhibit hemagglutination of influenza virus. Hemagglutination-inhibition activity of these RNA tumor viruses could be restored by in vitro resialylation catalyzed by sialyl transferase. The major glycoprotein in the intact envelope of desialylated and, to some extent, native virions could be specificallly labeled in vitro with CMP-(14C) sialic acid. These studies further characterize the individual glycoproteins of mouse mammary tumor virus, Rauscher murine leukemia virus, and Mason-Pfizer monkey virus.     

Cucumber mosaic virus, a model for RNA virus evolution

Taxonomic relationships: Cucumber mosaic virus (CMV) is the type member of the Cucumovirus genus, in the family Bromoviridae . Additional members of the genus are Peanut stunt virus (PSV) and Tomato aspermy virus (TAV). The RNAs 3 of all members of the genus can be exchanged and still yield a viable virus, while the RNAs 1 and 2 can only be exchanged within a species.
Physical properties: The virus particles are about 29 nm in diameter, and are composed of 180 subunits (T = 3 icosahedral symmetry). The particles sediment with an s value of approximately 98. The virions contain 18% RNA, and are highly labile, relying on RNA–protein interactions for their integrity. The three genomic RNAs, designated RNA 1 (3.3 kb in length), RNA 2 (3.0 kb) and RNA 3 (2.2 kb) are packaged in individual particles; a subgenomic RNA, RNA 4 (1.0 kb), is packaged with the genomic RNA 3, making all the particles roughly equivalent in composition. In some strains an additional subgenomic RNA, RNA 4A is also encapsidated at low levels. The genomic RNAs are single stranded, plus sense RNAs with 5' cap structures, and 3' conserved regions that can be folded into tRNA-like structures.
Satellite RNAs: CMV can harbour molecular parasites known as satellite RNAs (satRNAs) that can dramatically alter the symptom phenotype induced by the virus. The CMV satRNAs do not encode any proteins but rely on the RNA for their biological activity.
Hosts: CMV infects over 1000 species of hosts, including members of 85 plant families, making it the broadest host range virus known. The virus is transmitted from host to host by aphid vectors, in a nonpersistent manner.
Useful web sites: http://mmtsb.scripps.edu/viper/1f15.html (structure); http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/10040001.htm (general information)     

Detection,distribution and control of Potato mop-top virus,a soil-borne virus,in northern Europe

Potato mop-top virus (PMTV; genus Pomovirus; family Virgaviridae) is transmitted by the soil-borne Spongospora subterranea f.sp. subterranea, a protoctist that causes powdery scab on potato. PMTV is distributed widely in the potato growing areas in South and North America, Japan and northwestern Europe. This article reviews the current knowledge on detection, distribution and control of PMTV with focus on the Baltic Sea region. Since the 1980s, PMTV has caused great economic losses to potato production in the Nordic countries (Norway, Sweden, Denmark and Finland), but its occurrence in other countries of the Baltic Sea region remained unknown. To fill this knowledge gap, harmonised sampling and virus detection procedures including bioassays and serological and molecular methods were employed by 21 research institutions to detect PMTV in potato tubers and soil samples in 2005–2008. Potato growing areas were widely contaminated with PMTV in the Nordic countries. Only the main seed potato production area in northern Sweden and the High Grade seed potato production zone in Finland were negative for PMTV. Intensive and systematic surveys in Poland in 2004–2008 found no evidence of PMTV, except a single PMTV-infected tuber detected in 2008. Surveys in the Baltic countries (Lithuania, Latvia and Estonia) and northwestern Russia (Leningrad province) were negative for PMTV, except infection of minitubers in a screenhouse in Latvia in 2005. Varying percentages of tubers expressing spraing symptoms in Sweden, Norway, Denmark and Poland were infected with Tobacco rattle virus, and bioassays indicated similar results for Russia. Incidence of symptomless infections with PMTV was high in tubers of many potato cultivars. Here, we discuss the contrasting patterns of distribution of PMTV in the Baltic Sea region, factors playing a role in dispersal and establishment of PMTV in new fields and means for controlling PMTV and its spread to new areas. We emphasise the use of the current virus-specific methods for the detection of PMTV in symptomless potato tubers and the high risks of disseminating PMTV to new fields and areas in viruliferous resting spores of S. subterranea in the soil adhering to seed tubers. PMTV-resistant potato cultivars will provide the only sustainable means for preventing yield losses in the infested fields and the prospects of resistance breeding are summarised.     

Polypeptide composition of spleen necrosis virus, a reticuloendotheliosis virus.

The polypeptide composition of virions of spleen necrosis virus, a reticuloendotheliosis virus, was determined using electrophoresis on sodium dodecyl sulfate-containing, 10 percent polyacrylamide gels. Ten polypeptides were resolved. Four of these were present in minor and somewhat variable amounts. Two proteins, gp71 and gp22, contained D-glucosamine and were located on the outer surface of the lipid envelope, as demonstrated by lactoperoxidase-catalyzed iodination and by bromelain digestion. The results suggest that two of the minor proteins, p36 and p26, were also located on the outer surface, although they lacked D-glucosamine. Treatment of the virus with 0.25 percent Nonidet P-40 and 1 percent dithiothreitol produced a subparticle with a buoyant density of approximately 1.31 g/cm-3. This particle was relatively enriched with polypeptides p77, p62, and p50 and contained small amounts of three other polypeptides.     

Tobacco mosaic virus, not just a single component virus anymore

Taxonomy: Tobacco mosaic virus (TMV) is the type species of the Tobamovirus genus and a member of the alphavirus-like supergroup. Historically, many tobamoviruses are incorrectly called strains of TMV, although they can differ considerably in sequence similarities and host range from each other and from TMV. Physical properties: TMV virions are 300 × 18 nm rods with a central hollow cavity ( Fig. 1 ) and are composed of 95% capsid protein (CP), and 5% RNA. Each CP subunit interacts with 3-nts in a helical arrangement around the RNA. Virions are stable for decades; infectivity in sap survives heating to 90 °C.

Figure 1 Open in figure viewer PowerPoint Electron micrograph of TMV virions stained with uranyl acetate. Courtesy of Dr J.N. Culver, University of Maryland Biotechnology Institute.     

The entry into host cells of Sindbis virus, vesicular stomatitis virus and Sendai virus.

We have compared the mechanisms of entry into host cells of three enveloped viruses: Sendai virus, vesicular stomatitis virus (VSV) and Sindbis virus. Virus entry by membrane fusion should antigenically modify the surface of a newly infected cell in such a way that it will be killed by anti-viral antibody and complement. On the other hand, virus entry by a mechanism involving uptake by the cell of the whole virion should not make cells sensitive to antibody and complement. As expected, cells newly infected with Sendai virus were readily and completely lysed by anti-Sendai antibody and complement. In marked contrast, however, cells newly infected with either Sindbis virus or VSV were killed by anti-viral antibody and complement only when infected at an extremely high multiplicity of infection, in excess of 1000 plaque-forming units per cell. We favor the following explanation for these results with Sindbis virus and VSV: a very large majority of the Sindbis and VSV virions entered the infected cells by some means other than membrane fusion, presumably engulfment of the whole particle. Efficient entry by way of membrane fusion may therefore not be a general characteristic of enveloped viruses.     

Insect virus polyhedra, infectious protein crystals that contain virus particles

High-resolution atomic structures have been reported recently for two types of viral polyhedra, intracellular protein crystals produced by ubiquitous insect viruses. Polyhedra contain embedded virus particles and function as the main infectious form for baculoviruses and cypoviruses, two distinct classes of viruses that infect mainly Lepitoptera species (butterflies and moths). Polyhedra are extremely stable and protect the virus particles once released in the environment. The extensive crystal contacts observed in the structures explain the remarkable stability of viral polyhedra and provide hints about how these crystals dissolve in the alkaline midgut, releasing embedded virus particles to infect feeding larvae. The stage is now set to answer intriguing questions about the in vivo crystallization of polyhedra, how virus particles are incorporated into polyhedra, and what determines the size and shape of the crystals. Large quantities of polyhedra can be obtained from infected larvae and polyhedra can also be produced using insect cell expression systems. Modified polyhedra encapsulating other entities in place of virus particles have potential applications as a means to stabilize proteins such as enzymes or growth factors, and the extremely stable polyhedrin lattice may provide a framework for future engineered micro-crystal devices.     

Ourmia melon virus, a virus from Iran with novel properties

A virus associated with a mosaic disease in melons in the Ourmia district in northern Iran was mechanically transmissible to a wide range of test plants but was not transmitted using aphids, the whitefly Trialeurodes vaporariorum or the mite Tetranychus urticae. Its rather stable particles somewhat resembled those of both geminiviruses and alfalfa mosaic virus; they were 18·5 nm in mean width, parallel-sided, and of several discrete lengths, 30 nm and 37 nm being the shortest and commonest lengths. Both ends of all particles were sharply triangular in profile. The particles contained linear single-stranded RNA of three sizes, estimated as 0·91,0·35 and 0·32, all × 10⁶ molecular weight, and two coat proteins of 26·3 and 23·3 × 10³ estimated molecular weight. The virus, named Ourmia melon virus, appears to be the first described representative of a new virus group.     

A complex interplay among virus, dendritic cells, T cells, and cytokines in dengue virus infections

Severe dengue virus (DV) infections can cause the life-threatening condition dengue hemorrhagic fever, which is characterized by a severe plasma leak, thrombocytopenia, hemorrhage, and, in severe cases, circulatory collapse and death. There is now much evidence that pre-existing immunity to DV can enhance disease when an individual becomes infected on a second or sequential occasion. It has been shown that in contrast to infected dendritic cells (DC), noninfected bystander DC underwent maturation in dengue infection. In this study, we show that TNF-alpha and type I IFN contribute to the maturation of bystander DC, whereas the inhibition of DV-infected DC maturation can be overcome by activated T cells. Furthermore, IFN-gamma-inducible chemokines, CXCL9, 10, and 11 produced by infected DC are greatly amplified in the presence of DV-specific T cells. The chemokine secretion is also enhanced in coculture of HUVEC with either DV-infected DC or activated T cells. Finally, we found a close correlation between the serum level of these three chemokines and disease severity.     

Measles virus, immune control, and persistence

Measles remains one of the most important causes of child morbidity and mortality worldwide with the greatest burden in the youngest children. Most acute measles deaths are owing to secondary infections that result from a poorly understood measles-induced suppression of immune responses. Young children are also vulnerable to late development of subacute sclerosing panencephalitis, a progressive, uniformly fatal neurologic disease caused by persistent measles virus (MeV) infection. During acute infection, the rash marks the appearance of the adaptive immune response and CD8(+) T cell-mediated clearance of infectious virus. However, after clearance of infectious virus, MeV RNA persists and can be detected in blood, respiratory secretions, urine, and lymphoid tissue for many weeks to months. This prolonged period of virus clearance may help to explain measles immunosuppression and the development of lifelong immunity to re-infection, as well as occasional infection of the nervous system. Once MeV infects neurons, the virus can spread trans-synaptically and the envelope proteins needed to form infectious virus are unnecessary, accumulate mutations, and can establish persistent infection. Identification of the immune mechanisms required for the clearance of MeV RNA from multiple sites will enlighten our understanding of the development of disease owing to persistent infection.     

Incidence of antibodies against human immunodeficiency virus, human T-cell lymphotropic virus type 1, hepatitis B virus, hemorrhagic fever with renal syndrome virus and Chlamydia in Tonga and western Samoa

Among the populations of Tonga and Western Samoa, serum antibodies against human immunodeficiency virus or hemorrhagic fever with renal syndrome virus were not detected (0/904 and 0/192). No serum samples were considered to be positive for antibody against human T-cell lymphotropic virus type 1 (0/527). Hepatitis B antigen and antibody were found in 4% (8/192) and 47% (90/192), respectively. Chlamydia trachomatis IgG and C. psittaci IgG antibodies were detected in 39% (75/192) and 47% (91/192), respectively. The possibilities of the spread of human immunodeficiency virus and hemorrhagic fever with renal syndrome virus on the islands when the viruses invade from abroad were discussed.     

Antigenic and structural relationships of the surface antigens of hepatitis B virus, ground squirrel hepatitis virus, and woodchuck hepatitis virus.

The surface antigens of human hepatitis B (HBsAg), ground squirrel hepatitis (GSHsAg), and woodchuck hepatitis (WHsAg) viruses were compared serologically, and their major polypeptides were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tryptic peptide mapping. Results showed that both GSHsAg and WHsAg are antigenically cross-reactive, that their major pairs of polypeptides have identical mobilities on sodium dodecyl sulfate gels, and that the major polypeptides of GSHsAg and WHsAg migrate faster in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than do the corresponding bands of HBsAg. The peptide maps of the major (P-22) surface antigen polypeptides of GSHsAg and WHsAg showed that they shared over half of their spots. Peptide mapping of HBsAg subtypes indicated a close relationship between the major polypeptides (P-24) of adw and adr and a more distal relationship to ayw. Only about 25% of the spots shared by the combined HBsAg subtypes were also found in the peptide maps of GSHsAg and WHsAg, indicating at least some structural homology among the major polypeptides of the human and animal virus surface antigen particles. This is also reflected in the serological cross-reactivity among HBsAg, GSHsAg, and WHsAg. Further, the detection of ground squirrel and woodchuck antigens by Ausria II radioimmunoassay, combined with peptide mapping data indicating the common origin of these viruses, suggests that the common a determinant is shared by each and is restricted to approximately 25% of the sequences in their major polypeptides.     

GRB2 interaction with the ecotropic murine leukemia virus receptor, mCAT-1, controls virus entry and is stimulated by virus binding

For retroviruses such as HIV-1 and murine leukemia virus (MLV), active receptor recruitment and trafficking occur during viral entry. However, the underlying mechanisms and cellular factors involved in the process are largely uncharacterized. The viral receptor for ecotropic MLV (eMLV), a classical model for retrovirus infection mechanisms and pathogenesis, is mouse cationic amino acid transporter 1 (mCAT-1). Growth factor receptor-bound protein 2 (GRB2) is an adaptor protein that has been shown to couple cell surface receptors, such as epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor, to intracellular signaling events. Here we examined if GRB2 could also play a role in controlling infection by retroviruses by affecting receptor function. The GRB2 RNA interference (RNAi)-mediated suppression of endogenous GRB2 resulted in a consistent and significant reduction of virus binding and membrane fusion. The binding between eMLV and cells promoted increased GRB2-mCAT-1 interactions, as detected by immunoprecipitation. Consistently, the increased colocalization of GRB2 and mCAT-1 signals was detected by confocal microscopy. This association was time dependent and paralleled the kinetics of cell-virus membrane fusion. Interestingly, unlike the canonical binding pattern seen for GRB2 and growth factor receptors, GRB2-mCAT-1 binding does not depend on the GRB2-SH2 domain-mediated recognition of tyrosine phosphorylation on the receptor. The inhibition of endogenous GRB2 led to a reduction in surface levels of mCAT-1, which was detected by immunoprecipitation and by a direct binding assay using a recombinant MLV envelope protein receptor binding domain (RBD). Consistent with this observation, the expression of a dominant negative GRB2 mutant (R86K) resulted in the sequestration of mCAT-1 from the cell surface into intracellular vesicles. Taken together, these findings suggest a novel role for GRB2 in ecotropic MLV entry and infection by facilitating mCAT-1 trafficking.