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Phylogenetic analysis of the Arenaviridae: patterns of virus evolution and evidence for cospeciation between arenaviruses and their rodent hosts.

Viruses of the Arenaviridae cause hemorrhagic fevers and neurologic disease in humans. Historically, the arenaviruses have been divided into two complexes (LASV-LCMV, Tacaribe) through the use of antigenic typing. The phylogeny of the Arenaviridae as a whole has not been estimated previously due to a lack of sequence data for all members of the family. In this study, nucleocapsid protein gene sequence data were obtained for all currently known arenaviruses and used to estimate, for the first time, a phylogeny of the entire virus family. The LCMV-LASV complex arenaviruses are monophyletic and comprise three distinct lineages. The Tacaribe complex viruses also are monophyletic and occupy three distinct lineages. Comparisons of arenavirus phylogeny with rodent host phylogeny and taxonomic relationships provide several examples in which virus-host cospeciation is potentially occurring. The pathogenic arenaviruses do not appear to be monophyletic, suggesting that the pathogenic phenotype has arisen in multiple independent events during virus evolution.

Animals↗

[Neutralization test for lymphocytic choriomeningitis virus for distinguishing between two arenavirus infections in Argentina].

The active coexistence of two pathogenic arenaviruses, Junin (JUNV) and lymphocytic choriomeningitis (LCMV), in the same region of Argentina, has been known since the early 70's, and records of clinical and subclinical human infections by one and/or the other agent have been continuously produced for the last 25 years. Anti-LCMV antibody is currently searched only by indirect immunofluorescence, a test that shows cross reactions among a number of arenaviruses yielding, in the cases of LCMV and JUNV consecutive infections, a concomitant seroconversion for both viruses, as an inconclusive diagnostic result. In contrast, neutralization (NT) tests reveal arenavirus antibodies directed to unique epitopes on these virus envelopes, thus allowing to disclose the sequence in the cases of consecutive infections. In this paper, the characteristics of neutralization (NT) test for LCMV in cell cultures are described, as well as its performance in the field diagnosis of LCMV human infections. The native LCMV strain Cba An 13065 was inoculated on L-929 cell (ATCC CCL 1), and procedures were followed to perform a constant virus-variable serum NT test. Final points of sera titrations were expressed as the maximal serum dilution that yielded 75% of pfu inhibition. This NT test was assayed on paired serum samples of 36 patients with confirmed Argentine hemorrhagic fever (AHF) (a disease caused by JUNV), who had had a known previous contact with LCMV through IFI. The use of this one test led to confusing diagnosis of the disease due to concomitant seroconversion for JUNV and LCMV. By using NT test, it was shown that: some of them were possibly not infected by LCMV, and that 30/36 cases (83.3%) had a pre-existing level of LCMV antibody, with titers in the range of 5 to 640, remaining unchanged 60 days after the clinical AHF. This shows that NT antibodies to LCMV are not influenced by the outcome of the immune response to JUNV, thus confirming the efficiency of NT test as identificator among arenaviruses. To assess the performance of this NT test in individuals having only IFI antibodies to LCMV, 126 serum samples obtained through serological surveillance in a rural area of Argentina, were used. It was found that NT had improved coincidence with IFI as IFI titers increased. Interpretations were based on the pan-arenavirus antibody response obtained by using IFI as the only test. Results presented herein prove that the described NT test is a valuable tool for the detection of LCMV infections, particularly when a previous infection with LCMV has to be demonstrated during the acute phase of Argentine hemorrhagic fever.

Acute Disease↗

Arenavirus diversity and evolution: quasispecies in vivo.

Arenaviruses exist as viral quasispecies due to the high mutation rates of the low-fidelity viral RNA-dependent RNA polymerase (RdRp). This genomic heterogeneity is advantageous to the population, allowing for adaptation to rapidly changing environments that present varying types and degrees of selective pressure. The significant variation in biological properties observed among lymphocytic choriomeningitis virus (LCMV) strains, the prototypic arenavirus, indicates to what extent a quasis-pecies dynamics may play a role in arenavirus adaptability and pathogenesis. Several aspects of arenavirus variability and its contribution to pathogenesis will be discussed.

Animals↗

Response of cells persistently infected with arenaviruses to superinfection with homotypic and heterotypic viruses.

Vero cell cultures persistently infected with the arenaviruses Junin, Pichinde, Tacaribe, and Tamiami were established and designated Vero-Jun, Vero-Pic, Vero-Tac, and Vero-Tam, respectively. Two types of carrier cultures could be easily distinguished: Vero-Jun and Vero-Tac systems were characterized by a lack of infectious virus production after a few cell transfers, whereas a more productive state with continuous release of virus was observed in Vero-Pic and Vero-Tam cultures. These differences appeared to be related to resistance of the culture to viral superinfection. In fact, Vero-Jun and Vero-Tac cultures totally excluded only the replication of the serologically more closely related arenaviruses Amapari, Junin, or Tacaribe, while the refractoriness of Vero-Pic and Vero-Tam cultures was extended to most of the virus group members. The resistance of Vero-Jun cells to superinfection by Junin or Tacaribe virus could be ascribed to the production of specific uv-resistant Junin interfering particles, which showed a specific range of interference against Junin and Tacaribe viruses. Interfering particles against homotypic and heterotypic arenaviruses were isolated from Vero-Pic cultures. However, the degree of interference developed by these Pic-interfering particles was not enough to fully explain reinfecting virus exclusion from Vero-Pic cultures. Viral susceptibility of persistent cultures is proposed as a useful tool to examine relationships of members of the arenavirus group.

Animals↗

Establishment of conventional and fluorescence resonance energy transfer-based real-time PCR assays for detection of pathogenic New World arenaviruses.

BACKGROUND: Five of the known arenaviruses cause viral hemorrhagic fever in humans and are classified as biosafety level 4 pathogens. Four of the viruses, namely Junin, Guanarito, Machupo, and Sabia, belong to clade B of New World arenaviruses that also comprises the nonpathogenic viruses Tacaribe, Cupixi, and Amapari. OBJECTIVES: To establish real-time reverse transcription (RT)-PCR assays for Junin and Guanarito virus based on fluorescence resonance energy transfer (FRET) probes, and a universal RT-PCR assay for all known clade B viruses with conventional read-out. RESULTS: Conserved sequences in the nucleoprotein gene were chosen as target sites for primers and FRET probes. A common set of primers was designed for all three assays. The assays were based on one-step RT-PCR reagents and were optimised with respect to analytical sensitivity using synthetic RNA templates. The real-time PCR assays detected about 0.5 and 5TCID(50) of cell culture-derived Junin and Guanarito virus, respectively. The universal clade B PCR amplified cell culture-derived RNA of Junin, Guanarito, Machupo, and Sabia virus (5-500TCID(50) per reaction), as well as RNA of Tacaribe, Cupixi, and Amapari virus. CONCLUSIONS: The PCR assays may be used as complementary diagnostic tests for pathogenic New World arenaviruses. The universal PCR assay could also be suitable for the detection of novel clade B arenaviruses in patients as well as in animal reservoirs.

Animals↗

The small RING finger protein Z drives arenavirus budding: implications for antiviral strategies.

By using a reverse genetics system that is based on the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV), we have identified the arenavirus small RING finger Z protein as the main driving force of virus budding. Both LCMV and Lassa fever virus (LFV) Z proteins exhibited self-budding activity, and both substituted efficiently for the late domain that is present in the Gag protein of Rous sarcoma virus. LCMV and LFV Z proteins contain proline-rich motifs that are characteristic of late domains. Mutations in the PPPY motif of LCMV Z severely impaired the formation of virus-like particles. LFV Z contains two different proline-rich motifs, PPPY and PTAP, which are separated by eight amino acids. Mutational analysis revealed that both motifs are required for efficient LFV Z-mediated budding. Both LCMV and LFV Z proteins recruited to the plasma membrane Tsg101, which is a component of the class E vacuolar protein sorting machinery that has been implicated in budding of HIV and Ebola virus. Targeting of Tsg101 by RNA interference caused a strong reduction in Z-mediated budding. These results indicate that Z is the arenavirus functional counterpart of the matrix proteins found in other negative strand enveloped RNA viruses. Moreover, members of the vacuolar protein sorting pathway appear to play an important role in arena-virus budding. These findings open possibilities for antiviral strategies to combat LFV and other hemorrhagic fever arenaviruses.

Amino Acid Sequence↗

Isolation and characterization of pirital virus, a newly discovered South American arenavirus.

Specific rodent species are principal hosts for each of the well-characterized members of the virus family Arenaviridae. Guanarito virus (Arenaviridae) is the etiologic agent of Venezuelan hemorrhagic fever. A previous study on the epidemiology of Venezuelan hemorrhagic fever revealed extensive arenavirus infection (presumed to be caused by Guanarito virus) in two rodent species. Sigmodon alstoni and Zygodontomys brevicauda, collected from the region of Venezuela in which the disease is endemic. In the present study, four arenavirus isolates recovered from the Municipality of Guanarito (two isolates each from S. alstoni and Z. brevicauda) were characterized to learn more about the natural rodent host relationships of Guanarito virus. Serologic tests and analyses of nucleocapsid protein gene sequence data indicated that the two isolates from Z. brevicauda are strains of Guanarito virus and that the two isolates from S. alstoni are representatives of a novel New World arenavirus (proposed name Pirital) that is antigenically and phylogenetically distinct from all known New World arenaviruses. The results of the present study provide further evidence that the cane mouse Z. brevicauda is a natural host of Guanarito virus and suggest that the cotton rat S. alstoni is the natural reservoir host of Pirital but not Guanarito virus.

Animals↗

Effect of actinomycin D on arenavirus growth and estimation of the generation time for a virus particle.

In an attempt to define the involvement of host transcription in arenavirus growth, a study was made of the effect of actinomycin D (AMD) on the yields of infectious Pichinde, Tacaribe and Junin viruses. The drug was added either immediately after virus adsorption or later after infection, at the stationary phase of virus growth. The time of exposure of the infected cells to the inhibitor was so chosen that the generation and release of virus into the medium took place in the presence of AMD. A double label technique was used to estimate the generation time of an arenavirus particle. This was found to be 6 h or less for all of the arenaviruses examined. The results indicated that treatment of the host cells with AMD, either immediately after virus adsorption or later after infection, does not affect the yield of infectious Pichinde, Tacaribe or Junin viruses, thus implying that continuous host transcription is not required for the replication cycle of these arenaviruses.

Arenaviridae↗

Monoclonal antibodies to lymphocytic choriomeningitis virus react with pathogenic arenaviruses.

Certain arenaviruses have become widely recognized as important human pathogens, the most notable among these being Lassa virus, the causative agent of Lassa fever. Two other members of the group, Junin and Machupo virus, are the aetiological agents of Argentine and Bolivian haemorrhagic fevers, respectively. All these agents share both morphological features and to varying degrees serological cross-reactivity with other non-pathogenic arenaviruses. Despite the evident clinical importance of these viruses, work to define their physiochemical structure and to develop rapid and precise diagnostic techniques has been slow. Consequently, the definitive relationships among West African Lassa strains, strains of a related agent from Mozambique and of an Old World arenavirus, lymphocytic choriomeningitis (LCM), have not been established. This problem is of more than simple taxonomic importance in view of the fact that a Mozambique virus strain produced subclinical infection in experimental monkeys which were then resistant to challenge with monkey and human virulent Lassa virus from Sierra Leone. We have explored the use of monoclonal hybridoma antibodies generated against relatively less hazardous arenaviruses to define antigens cross-reactive with the important human pathogens of the group. Here we describe the use of monoclonal antibodies directed against LCM, virus to define antigenic specificities shared among LCM, Lassa and Mozambique viruses.

Antibodies, Viral↗

Antigenic relatedness between arenaviruses defined at the epitope level by monoclonal antibodies.

Monoclonal antibodies (MAbs) were produced against two African arenaviruses, Lassa virus and Mopeia virus. Competitive binding analysis of MAbs identified four antigenic sites on the nucleoprotein (NP), two on glycoprotein 1 (GP1) and six on glycoprotein 2 (GP2) of the Josiah strain of Lassa virus. 64 virus isolates from western, central and southern Africa were all consistently distinguishable by MAbs to certain epitopic sites on GP1, GP2 and NP viral proteins. Furthermore, MAbs to Lassa virus GP1 and NP uniformly distinguished viruses from the West African countries of Sierra Leone, Liberia and Guinea from those of Nigeria. GP2-directed MAbs to two African arenaviruses reacted broadly with South American arenaviruses demonstrating that an epitopic site on GP2 may be the most highly conserved antigen in the arenavirus group.

Africa↗

Myristoylation of the RING finger Z protein is essential for arenavirus budding.

The arenavirus small RING finger Z protein is the main driving force of arenavirus budding. The primary structure of Z is devoid of hydrophobic transmembrane domains, but both lymphocytic choriomeningitis virus (LCMV) and Lassa fever virus Z proteins accumulate near the inner surface of the plasma membrane and are strongly membrane associated. All known arenavirus Z proteins contain a glycine (G) at position 2, which is a potential acceptor site for a myristoyl moiety. Metabolic labeling showed incorporation of [(3)H]myristic acid by wild-type Z protein but not by the G2A mutant. The mutation G2A eliminated Z-mediated budding. Likewise, treatment with the myristoylation inhibitor 2-hydroxymyristic acid inhibited Z-mediated budding, eliminated formation of virus-like particles, and caused a dramatic reduction in virus production in LCMV-infected cells. Budding activity was restored in G2A mutant Z proteins by the addition of the myristoylation domain of the tyrosine protein kinase Src to their N termini. These findings indicate N-terminal myristoylation of Z plays a key role in arenavirus budding.

Carrier Proteins↗

Cells expressing the RING finger Z protein are resistant to arenavirus infection.

Arenaviruses include Lassa fever virus (LFV) and the South American hemorrhagic fever viruses. These viruses cause severe human disease, and they pose a threat as agents of bioterrorism. Arenaviruses are enveloped viruses with a bisegmented negative-strand RNA genome whose proteomic capability is limited to four polypeptides: nucleoprotein (NP); surface glycoprotein (GP), which is proteolytically processed into GP1 and GP2; polymerase (L); and a small (11-kDa) RING finger protein (Z). Our investigators have previously shown that Z has a strong inhibitory activity on RNA synthesis mediated by the polymerase of the prototypic arenavirus, lymphocytic choriomeningitis virus (LCMV). In this report we show that cells transduced with a replication-deficient recombinant adenovirus expressing Z (rAd-Z) are resistant to LCMV and LFV infection. Virus cell entry mediated by LCMV or LFV GP was not affected in rAd-Z-transduced cells, but both virus transcription and replication were strongly and specifically inhibited, which resulted in a dramatic reduction in production of infectious virus. These findings open new avenues for developing antiviral strategies to combat the highly pathogenic human arenaviruses, including LFV.

Adenoviridae↗

Posttranslational modification of alpha-dystroglycan, the cellular receptor for arenaviruses, by the glycosyltransferase LARGE is critical for virus binding.

The receptor for lymphocytic choriomeningitis virus (LCMV), the human pathogenic Lassa fever virus (LFV), and clade C New World arenaviruses is alpha-dystroglycan (alpha-DG), a cell surface receptor for proteins of the extracellular matrix (ECM). Specific posttranslational modification of alpha-DG by the glycosyltransferase LARGE is critical for its function as an ECM receptor. In the present study, we show that LARGE-dependent modification is also crucial for alpha-DG's function as a cellular receptor for arenaviruses. Virus binding involves the mucin-type domain of alpha-DG and depends on modification by LARGE. A crucial role of the LARGE-dependent glycosylation of alpha-DG for virus binding is found for several isolates of LCMV, LFV, and the arenaviruses Mobala and Oliveros. Since the posttranslational modification by LARGE is crucial for alpha-DG recognition by both arenaviruses and the host-derived ligand laminin, it also influences competition between virus and laminin for alpha-DG. Hence, LARGE-dependent glycosylation of alpha-DG has important implications for the virus-host cell interaction and the pathogenesis of LFV in humans.

Animals↗

Oliveros virus: a novel arenavirus from Argentina.

During the past few decades several newly recognized rodent-borne arenaviruses have been shown to be associated with severe hemorrhagic fever cases in South America. Changes in ecology and farming practices throughout the region have increased the concern over the potential public health threat posed by such emerging virus diseases. Oliveros (OLV) virus is a recently discovered arenavirus of the rodent Bolomys obscurus in Argentina. Genetic analysis of the small genomic RNA segment, which encodes the nucleocapsid protein and the envelope glycoproteins, shows that Oliveros is a novel, phylogenetically distinct member of the Arenaviridae family which differs in nucleotide sequence from the previously characterized members by approximately 35% or more. Despite this level of diversity, OLV virus possesses the same ambisense genome structure and many overall RNA and protein features in common with other arenaviruses. These data represent an important first step in the development of specific immunological and PCR diagnostic reagents to allow assessment of the prevalence and disease potential of this virus.

Animals↗

Identification and characterization of potent small molecule inhibitor of hemorrhagic fever New World arenaviruses.

Category A arenaviruses as defined by the National Institute of Allergy and Infectious Diseases (NIAID) are human pathogens that could be weaponized by bioterrorists. Many of these deadly viruses require biosafety level-4 (BSL-4) containment for all laboratory work, which limits traditional laboratory high-throughput screening (HTS) for identification of small molecule inhibitors. For those reasons, a related BSL-2 New World arenavirus, Tacaribe virus, 67-78% identical to Junín virus at the amino acid level, was used in a HTS campaign where approximately 400,000 small molecule compounds were screened in a Tacaribe virus-induced cytopathic effect (CPE) assay. Compounds identified in this screen showed antiviral activity and specificity against not only Tacaribe virus, but also the Category A New World arenaviruses (Junín, Machupo, and Guanarito). Drug resistant variants were isolated, suggesting that these compounds act through inhibition of a viral protein, the viral glycoprotein (GP2), and not through cellular toxicity mechanisms. A lead compound, ST-294, has been chosen for drug development. This potent and selective compound, with good bioavailability, demonstrated protective anti-viral efficacy in a Tacaribe mouse challenge model. This series of compounds represent a new class of inhibitors that may warrant further development for potential inclusion in a strategic stockpile.

Amino Acid Sequence↗

Differential inhibitory action of two azoic compounds against arenaviruses.

The action of five azo-based compounds against the arenaviruses Junin (JUNV) and Tacaribe (TCRV) was evaluated in vitro by a virus yield inhibition assay in Vero cells and a cell-free virion inactivation assay. The compound 2-azo-(1'-(2'-nitroso)naphthyl)-benzoate (ANNB) was the most effective inhibitor of arenavirus production in Vero cells with EC(50) (effective concentration 50%) values in the range 6.5-26.2 microM and without inactivating properties. By contrast, the azodicarbonamide (ADA) was very effective in inactivating both arenaviruses with IC(50) (inactivating concentration 50%) values of 7.6 and 5.3 microM against JUNV and TCRV, respectively. The virucidal activity of ADA was time- and temperature-dependent. ANNB had no inhibitory action on virus binding or penetration of target cells and did not affect the synthesis of viral proteins. The most likely event susceptible to ANNB would be the process of intracellular virion assembly.

Animals↗

Arenavirus phylogeny: a new insight.

Arenaviridae is a worldwide distributed family, of enveloped, single stranded, RNA viruses. The arenaviruses were divided in two major groups (Old World and New World), based on serological properties and genetic data, as well as the geographic distribution. In this study the phylogenetic relationship among the members of the Arenaviridae was examined, using the reported genomic sequences. The comparison of the aligned nucleotide sequences of the S RNA and the predicted amino acid sequences of the GPC and N proteins, together with the phylogenetic analysis, strongly suggest a possible kinship of Pichindé and Oliveros viruses, with the Old World arenavirus group. This analysis points at the evolutive relationships between the arenaviruses of the Americas and can be used to evaluate the different hypotheses about their origin.

Arenavirus↗

Complementarity in the supramolecular design of arenaviruses and retroviruses revealed by electron cryomicroscopy and image analysis.

Arenaviruses are rodent-borne agents of diseases, including potentially lethal human hemorrhagic fevers. These enveloped viruses encapsidate a bisegmented ambisense single-stranded RNA genome that can be packaged in variable copy number. Electron cryomicroscopy and image analysis of New World Pichinde and Tacaribe arenaviruses and Old World lymphocytic choriomeningitis virus revealed pleomorphic enveloped particles ranging in diameter from approximately 400 to approximately 2,000 A. The surface spikes were spaced approximately 100 A apart and extended approximately 90 A from the maximum phospholipid headgroup density of the outer bilayer leaflet. Distinctive stalk and head regions extended radially approximately 30 and approximately 60 A from the outer bilayer leaflet, respectively. Two interior layers of density apposed to the inner leaflet of the viral lipid bilayer were assigned as protein Z and nucleoprotein (NP) molecules on the basis of their appearance, spacing, and projected volume. Analysis of en face views of virions lacking the GP-C spikes showed reflections consistent with paracrystalline packing of the NP molecules in a lattice with edges of approximately 57 and approximately 74 A. The structural proteins of retroviruses and arenaviruses assemble with similar radial density distributions, using common cellular components.

Animals↗