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At least 1,225 records · Page 68Linked to original sources
PubMed1992

The genetic evolution of the envelope gene of simian immunodeficiency virus in cynomolgus macaques infected with a complex virus pool.

Two cynomolgus macaques were infected with a complex, but characterized, challenge stock of simian immunodeficiency virus (SIVmac251 32H). The polymerase chain reaction was applied in a temporal sequence analysis to determine the sequences of the gp120 region of the SIV env gene, which were present in the blood of both macaques at 1, 6, and 15 months postinfection (p.i.). At 1 month p.i. selected sequences, which had been present in the original virus challenge stock, were reisolated. At later times, new sequences emerged, which had not been detected in the original virus challenge stock. Changes in sequence were restricted to specific regions of gp120, notably those equivalent to V1, V2, V4, and V5 of HIV-1, but not V3. The diversity and the rate of appearance of new sequences in the V1 region suggest that genetic evolution occurs by mechanisms in addition to nucleotide substitutions. These results are discussed in relation to the role of the envelope protein in the generation of protective immunity against infection with immunodeficiency viruses.

Amino Acid Sequence↗
PubMedDate not supplied

Bats as a continuing source of emerging infections in humans.

Amongst the 60 viral species reported to be associated with bats, 59 are RNA viruses, which are potentially important in the generation of emerging and re-emerging infections in humans. The prime examples of these are the lyssaviruses and Henipavirus. The transmission of Nipah, Hendra and perhaps SARS coronavirus and Ebola virus to humans may involve intermediate amplification hosts such as pigs, horses, civets and primates, respectively. Understanding of the natural reservoir or introductory host, the amplifying host, the epidemic centre and at-risk human populations are crucial in the control of emerging zoonosis. The association between the bat coronaviruses and certain lyssaviruses with particular bat species implies co-evolution between specific viruses and bat hosts. Cross-infection between the huge number of bat species may generate new viruses which are able to jump the trans-mammalian species barrier more efficiently. The currently known viruses that have been found in bats are reviewed and the risks of transmission to humans are highlighted. Certain families of bats including the Pteropodidae, Molossidae, Phyllostomidae, and Vespertilionidae are most frequently associated with known human pathogens. A systematic survey of bats is warranted to better understand the ecology of these viruses.

Animals↗
PubMed2002

[The threat of smallpox].

Smallpox is a highly contagious disease mainly transmitted by aerosols with a high case-fatality. The smallpox virus has evolved from a long adaptation to humans during Evolution, explaining that the virus is highly specific for humans and nonpathogenic for animals. Smallpox was eradicated in 1977 and vaccination was abandoned in the 1980's. This virus is a dreadful potential biological weapon since the reemergence of smallpox on the planet might be expected to be devastating, due to its high 'contagiosity', which would rapidly spread in naive populations, especially those living in urban areas, and worldwide through air travels. There is no anti-viral treatment and vaccine is active in the first four days post-exposure. Today, the stocks of smallpox virus constitute one of the most dangerous threats for humanity. There is a need for improving the safety of the vaccine and to reconsider the preventive strategy to face a possible attack by smallpox virus.

Bioterrorism↗
PubMed2025

Dating the origin of a viral domestication event in parasitoid wasps attacking Diptera.

Over the course of evolution, hymenopteran parasitoids have developed a close relationship with heritable viruses, sometimes integrating viral genes into their chromosomes. For example, in Drosophila parasitoids belonging to the Leptopilina genus, 13 viral genes from the Filamentoviridae family have been domesticated to deliver immunosuppressive factors to host immune cells, thereby protecting parasitoid offspring from the host immune response. The present study aims to comprehensively characterize this domestication event in terms of the viral genes involved, the wasp diversity affected by this event and its chronology. Our genomic analysis of 41 Cynipoidea wasps from six subfamilies revealed 18 viral genes that were endogenized during the early radiation of the Eucoilini/Trichoplastini clade around 75 million years ago. Wasps from this highly diverse clade develop not only from Drosophila but also from a variety of Schizophora. This event coincides with the radiation of Schizophora, a highly speciose Diptera clade, suggesting that viral domestication facilitated wasp diversification in response to host diversification. Additionally, in one of the species, at least one viral gene was replaced by another gene derived from a related filamentovirus. This study highlights the impact of viral domestication on the diversification of parasitoid wasps.

Animals↗
PubMed2004

Immune reconstitution in HIV-1 infected children with discordant response to antiretroviral therapies: patterns of HIV-1 env gene evolution driven by restoration of thymic function.

The evolution of human immunodeficiency virus type 1 (HIV-1) env gp120 region was addressed in HIV-1 infected children showing virological failure to antiretroviral therapy (ART). Sequence analysis of the replicating plasma virus at baseline and after one year of therapy documented evolution of gp120 in all subjects but one. Analysis of the host's selective pressure showed that the values of Ka/Ks ratios were higher in the V3 sequence than in the whole C2-V5 region in 4 of 5 children with improvement of thymic output. Moreover, in 2 of the 4 chidren, the V3 evolution paralleled with a reverse shift of the viral phenotype (from CXCR4-tropic to CCR5-tropic). These results suggest that, under ART, the V3 evolution towards less pathogenic viral variants may be driven by the host's increased selective pressure following restoration of thymic function and immune reconstitution.

Amino Acid Sequence↗
PubMed2005

Studies on antigenic and genomic properties of Brazilian rabies virus isolates.

Despite the recognized stability of rabies virus, differences among isolates from different species have been found. This work was carried out with the aim to identify antigenic and genomic differences in Brazilian rabies virus isolates and to verify whether such alterations would bear any relationship with the different hosts for the virus in nature. For that, 79 Brazilian rabies viruses isolated from different host species and from distinct regions within Brazil were submitted to antigenic characterization with a panel of 11 monoclonal antibodies (Mabs) directed to lyssavirus antigens and to genomic analyses by the reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of the N gene followed by restriction endonuclease analysis (REA). In addition, the nucleotide sequences of part of the N gene (225 bp) of seven isolates, taken as representative of the majority of the viruses under study, were determined. The analyses with the Mabs and RT-PCR/REA allowed the identification of two major groups of variants, the first formed by most isolates of cattle and bats and the second formed by viruses of dog origin. Partial sequencing of the N gene confirmed the similarity among isolates from cattle origin and those of vampire bats. However, viruses from non-haematophagous bats exhibited consistent differences from those of vampire bat isolates. Such findings suggest that the variants have evolved fairly stable modifications, which are not altered after passage in a dead-end host of a distinct species. No association could be established between antigenic or genomic alterations and geographic distribution of the isolates, which suggests that evolution of the virus has been directed to adaptation to the host species.

Amino Acid Sequence↗
PubMed1988

Antiviral agents targeted to interact with viral capsid proteins and a possible application to human immunodeficiency virus.

The tertiary structure of most icosahedral viral capsid proteins consists of an eight-stranded antiparallel beta-barrel with a hydrophobic interior. In a group of picornaviruses, this hydrophobic pocket can be filled by suitable organic molecules, which thereby stop viral uncoating after attachment and penetration into the host cell. The antiviral activity of these agents is probably due to increased rigidity of the capsid protein, which inhibits disassembly. The hydrophobic pocket may be an essential functional component of the protein and, therefore, may have been conserved in the evolution of many viruses from a common precursor. Since eight-stranded anti-parallel beta-barrels, with a topology as in viral capsid proteins, are not generally found for other proteins involved in cell metabolism, this class of antiviral agents is likely to be more virus-specific and less cytotoxic. Furthermore, the greatest conservation of viral capsid proteins occurs within this pocket, whereas the least conserved part is the antigenic exterior. Thus, compounds that bind to such a pocket are likely to be effective against a broader group of serologically distinct viruses. Discovery of antiviral agents of this type will, therefore, depend on designing compounds that can enter and fit snugly into the hydrophobic pocket of a particular viral capsid protein. The major capsid protein, p24, of human immunodeficiency virus would be a likely suitable target.

Antiviral Agents↗
PubMed2005

[Evolution of Sjögren syndrome associated with hepatitis C virus when chronic hepatitis C is treated by interferon or the association of interferon and ribavirin].

UNLABELLED: Hepatitis C virus is one of the most likely candidates as a potential pathogenic agent causing Sjogren's syndrome (SS) in a subset of patients. Nobody has until now described the evolution of SS associated with HCV when chronic hepatitis C is treated with antiviral therapy, interferon being an auto-immunity inductor. This is the purpose of our study. METHODS: Prospective study of 12 patients with a HCV-associated SS defined as certain according to the first european criteria and treated with interferon or interferon/ribavirin for their chronic hepatitis C. RESULTS: More than fifty percent of these patients developed a severe immunological complication especially when they were treated with interferon alone. Ribavirin may have had a protective role on interferon-mediated immunological complications. These complications went on after cessation of therapy. Sicca syndrome was improved only in the patients treated with the association (in 50% of the cases), but these patients also had a sustained virological response. It is difficult to tell if this improvement was due to the hepatitis C virus eradication or ribavirin treatment. CONCLUSION: Hepatitis C virus is implicated in the development of SS in a specific subset of patients for which we can propose the term SS "secondary to HCV" and this disease is not utterly benign especially after the introduction of interferon therapy. Ribavirin when associated with interferon gives a significative sustained virological response and could lower the incidence of immunological interferon-mediated complications with a favorable outcome of sicca syndrome.

Adult↗
PubMed1996

Characterization of a novel influenza hemagglutinin, H15: criteria for determination of influenza A subtypes.

Two viruses with a novel hemagglutinin (HA), A/duck/Australia/341/83 and A/shearwater/West Australia/2576/79, have been isolated from a duck and a shorebird in Australia. Hemagglutination inhibition and double immunodiffusion assays failed to reveal cross-reactivity with any of the known subtypes (H1 to H14). We therefore propose that these viruses constitute a new HA subtype, H15. Sequence analysis of the HA genes confirmed the serologic findings. When compared at the amino acid level, the HA1 region of the H15 subtype differs from those of the other subtypes by 30% and more. This degree of heterogeneity is also found among HA genes of other subtypes. Thus we propose that amino acid sequence data should be evaluated when determining the HA subtypes of influenza A viruses. Sequence comparison and phylogenetic analysis suggested that the HA subtype H15 is most closely related to the H7. Compared to the H7 HA, the H15 acquired a 30-nucleotide insertion within HA1 at position 253 which is located in the globular head of the molecule. This finding suggests that RNA recombination, although a rare event in nature, may play an important role in the evolution of influenza viruses.

Amino Acid Sequence↗
PubMed1992

A measles virus isolate from a child with Kawasaki disease: sequence comparison with contemporaneous isolates from 'classical' cases.

We examined the relationship between a measles virus isolate from a child with Kawasaki disease and two contemporaneous wild-type isolates from children with 'classical' measles and the Schwarz vaccine strain. Sequence analysis of 3118 bp from the nucleoprotein, matrix, fusion and haemagglutinin genes of each virus revealed that the isolate from the child with Kawasaki disease was not related to measles vaccine strains and did not contain any of the marked abnormalities previously found in subacute sclerosing panencephalitis isolates, but was more akin to wild-type isolates currently circulating in the U.K. A comparison of our sequences with those obtained from earlier wild-type U.K. isolates suggests significant evolution of measles virus in the U.K. over the last decade.

Amino Acid Sequence↗
PubMed1981

Establishment of persistent infection in mouse cells by Sindbis virus and its temperature-sensitive mutants.

The ability of wild-type (wt) Sindbis virus and six temperature-sensitive (ts) mutants to establish persistent infection in mouse L cells and a line of mouse embryo (ME) cells was determined. The wt established persistent infection in both ME cells and L cells at 39 degrees C. At 30 degrees C the wt established persistent infection in L cells but not ME cells, which did not recover from the initial infection. For the ts mutants, both cell lines survived the initial infection at 39 degrees C (the restrictive temperature) but the virus was eventually eliminated. At 30 degrees C (the permissive temperature) in L cells all mutants established persistent infection. In ME cells at 30 degrees C, RNA- mutants (unable to synthesize virus-specified RNA at 39 degrees C) established persistent infection whereas the cells did not recover from infection with RNA+ mutants (able to synthesize virus-specified RNA at 39 degrees C). The wt virus was less cytopathic in L cells than in BHK or ME cells. Interferon was produced by both L and ME cells at 30 degrees C and 39 degrees C, but its activity could not be detected in either cell line at 30 degrees C. It is proposed that establishment of persistent infection is dependent on reduced cytopathogenicity in the early stage of infection, and that further evolution of the virus then occurs to a less cytopathic form. Elimination of the virus at 39 degrees C is probably due to the action of interferon.

Animals↗
PubMed2002

The origin of modern plant virology.

Plant virology, born with Mayer's work, saw a first (embryonic) phase of development during two decades (1900-1920) with outstanding contributions from Dimitri Ivanovski, Martinus Beijerinck, Erwin Baur and Harry Allard. Between 1920 and 1930 a second phase saw the elaboration of surprising hypotheses concerning the enigmatic nature of viruses and experimental evidence of great stress was obtained. Revolutionary renewal began from the mid-1930s on the basis of a body of knowledge which was organically assembled into the first textbook of plant virology published by Kenneth Smith in 1933. In 1922, the geneticist Hermann Muller put forward the hypothesis that considered viruses as possible genes. The theory was resumed in an apparently independent way by Benjamin Duggar and Joanne Karrer Armstrong in 1923, who considered TMV a biocolloidal self-reproducing protein, like genes appeared to be. This hypothesis, even if neglected by virologists, anticipated by some decades the functional nature of viruses and represented the first conceptual response to virus enigma. Considerable experimental results were obtained by James Johnson, who showed that plants could be infected by different viruses and who introduced a first rational system of plant virus classification. Harold McKinney showed that TMV could mutate. Harold Storey, Kenneth Smith and Harry Severin demonstrated that several viruses could be transmitted by insects and supplied the first interpretation of the relationship between virus and insect. Mayme Dvorak and Helen Purdy obtained the first experimental evidence of the antigenic power of plant viruses. Virus purification, first tentatively accomplished with physical methods, was brilliantly performed by chemical means. Finally, Francis Holmes elaborated the first suitable test to estimate virus infectivity. The evolution of plant virology from an empirical discipline to a biological science took place thanks to the work of one group of American and English scientists who must be regarded as the fathers of modern plant virology.

History, 20th Century↗
PubMed1999

[Strain differentiation of the Newcastle disease virus by reverse transcriptase-polymerase chain reaction and sequencing population exchange].

A system for detection and strain differentiation of Newcastle disease virus (NDV) by reverse transcription of polymerase chain reaction (RT-PCR) (isolation of RNA, choice of primers for nested PCR, and purification of PCR products) and sequencing is developed and optimized. A nucleotide sequence of gene F site, coding for the F2/F1 cleavage site of F0 fusion protein and including several hypervariable regions, is determined for 10 Russian strains and vaccine strains. The data indicate a replacement of NDV populations in Russia and a rapid evolution of the virus. The origin of pathogenic NDV strains which have been circulating up to the present time is still unknown.

Base Sequence↗
PubMed2005

Identification and visualization of the dimerization initiation site of the prototype lentivirus, maedi visna virus: a potential GACG tetraloop displays structural homology with the alpha- and gamma-retroviruses.

Dimerization of retroviral genomic RNA is essential for efficient viral replication and is mediated by structural interactions between identical RNA motifs in the viral leader region. We have visualized, by electron microscopy, RNA dimers formed from the leader region of the prototype lentivirus, maedi visna virus. Characterization by in vitro assays of the domains responsible for this interaction has identified a 20 nucleotide sequence that functions as the core dimerization initiation site. This region is predicted to form a GACG tetraloop and therefore differs significantly from the kissing loop palindromes utilized to initiate dimerization in primate lentiviruses. The motif is strongly conserved across the ovine and caprine lentiviruses, implying a critical functional role. Furthermore, the proposed GACG tetraloop exhibits marked structural homology with similar structural motifs present in the leader regions of the alpha- and gamma-retroviruses, and the maedi visna virus dimer linkage region is capable of forming heterodimeric species with the Moloney murine leukemia virus Psi domain. This may be indicative of commonality of origin of the two viruses or convergent evolution.

Animals↗
PubMed1996

A longitudinal study of feline immunodeficiency virus-specific cytotoxic T lymphocytes in experimentally infected cats, using antigen-specific induction.

The evolution of the virus-specific cytotoxic T-lymphocyte response in two cats experimentally infected with feline immunodeficiency virus (FIV) was monitored. Effector cells were derived from peripheral blood lymphocytes during the acute and chronic phases of infection (0 to 21 and 62 to 127 weeks, respectively) and from the spleen and lymph nodes at 127 weeks after infection. Lymphocytes were restimulated in vitro with paraformaldehyde-fixed, autologous lymphoblasts which had been infected with recombinant vaccinia viruses expressing FIV GAG or ENV proteins. Unstimulated lymphocytes were also used as effectors in some assays. 51Cr-labelled autologous skin fibroblasts infected with recombinant vaccinia viruses were used as targets. FIV GAG-specific cytotoxic precursors were detected in restimulated circulating lymphocytes during acute infection in both cats. The onset of this activity was as early as 2 weeks postinfection (p.i.) in one cat. From 62 weeks p.i. neither FIV GAG- nor ENV-specific precursors could be detected in the peripheral blood. However, at 127 weeks p.i., GAG- and ENV-specific cytotoxic precursors were detected in lymphocytes isolated from lymph nodes. The FIV-specific cytotoxic cells were predominantly major histocompatibility complex class I restricted. No cytotoxic activity was detected from unstimulated lymphocytes. These studies demonstrate the use of an assay system for dissecting the FIV-specific cytotoxic cell response and show that precursor cells appear in the circulation very early after infection and prior to a detectable antibody response. Our results also suggest that the persistent high-level circulating antiviral cytotoxic T-lymphocyte responses seen in human immunodeficiency virus-infected humans may not be a feature of FIV infections in cats.

Animals↗
PubMed2026

Megamimivirus double-stranded DNA linear genomes flanked by highly diverse terminal inverted repeats.

UNLABELLED: Giant viruses have fundamentally expanded our understanding of virology by challenging the conventional boundaries of both virion size and genome complexity. However, the scarcity of isolates has left many of their unique biological features unexplored. Here, we report the isolation and characterization of four new giant virus species belonging to the subfamily Megamimivirinae, sampled from distinct environments across China. Among these, Megavirus daqingense is the first giant virus isolated from an oil reservoir; it exhibits virion stability under high salinity, chloroform exposure, and elevated temperatures, suggesting fitness adaptations to subsurface conditions. Using a hybrid sequencing approach that integrates short- and long-read technologies, we assembled complete linear genomes for all four isolates, each flanked by long terminal inverted repeats (TIRs). Comparative genomic and synteny analyses identified 29 distinct TIRs from 46 megamimivirus genomes. Gene content within these TIRs was highly diverse, with no orthologous proteins conserved across all repeats. Furthermore, TIR genes experienced weaker purifying selection than those in non-TIR regions (i.e., the genomic regions excluding the TIRs), consistent with their role as drivers of genome plasticity. Notably, we discovered for the first time that identical tRNA genes are shared between TIRs and non-TIR regions of eukaryotic viruses. Collectively, our work provides insights into the structural and evolutionary complexity of megamimiviruses, revealing TIRs as reservoirs of genetic diversity and hotspots for gene transfer, thereby playing a pivotal role in shaping the dynamic architecture of giant virus genomes. IMPORTANCE: Terminal inverted repeats (TIRs) are critical structural elements at the termini of linear genomes essential for fundamental processes such as recombination, replication, and integration across diverse organisms. However, the inherent limitations of short-read sequencing technologies have left the complete structure, diversity, and evolutionary significance of long TIRs in giant viruses unexplored. In this study, we leverage hybrid sequencing and comparative genomic analyses to unveil the complexity of TIRs across the subfamily Megamimivirinae. We demonstrate that TIRs are dynamic genomic hotspots characterized by remarkable gene diversity and unexpected conservation of specific tRNA genes. These findings establish TIRs as key drivers of genome plasticity, serving as hotspots for horizontal gene transfer and genetic innovation. By resolving the long-hidden terminal structures of megamimivirus genomes, this work provides a foundational framework for understanding how TIRs shape the evolution of giant viruses and, more broadly, advances our understanding of genome architecture in large DNA viruses.

Megavirus↗
PubMed2004

Neutralization sensitivity of a simian-human immunodeficiency virus (SHIV-HXBc2P 3.2N) isolated from an infected rhesus macaque with neurological disease.

Simian-human immunodeficiency virus (SHIV) chimerae, after in vivo passage in monkeys, can induce acquired immunodeficiency syndrome (AIDS)-like illness and death. A monkey infected with the molecularly cloned, pathogenic SHIV-HXBc2P 3.2 exhibited multifocal granulomatous pneumonia as well as progressive neurological impairment characterized by tremors and pelvic limb weakness. SHIV-HXBc2P 3.2N was isolated from brain tissue explants and characterized. Viruses with the envelope glycoproteins of SHIV-HXBc2P 3.2N exhibited increased sensitivity to soluble CD4 and several neutralizing antibodies compared with viruses with the parental SHIV-HXBc2P 3.2 envelope glycoproteins. By contrast, viruses with SHIV-HXBc2P 3.2 and SHIV-HXBc2P 3.2N envelope glycoproteins were neutralized equivalently by 2G12 and 2F5 antibodies, which are rarely elicited in HIV-1-infected humans. A constellation of changes involving both gp120 and gp41 envelope glycoproteins was responsible for the difference in susceptibility to neutralization by most antibodies. Surprisingly, the gain of an N-linked glycosylation site in the gp41 ectodomain contributed greatly to neutralization sensitivity. Thus, the environment of the central nervous system, particularly in the context of immunodeficiency, allows the evolution of immunodeficiency viruses with greater susceptibility to neutralization by antibodies.

Amino Acid Sequence↗