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PubMed1986

Organization of the thymidylate synthase gene of herpesvirus saimiri.

Herpesvirus saimiri codes, unlike most other herpesviruses, for a thymidylate synthase (TS). The TS gene of herpesvirus saimiri is unusual in structure and regulation of expression. It is transcribed into a nonspliced mRNA of 2,190 nucleotides. The single open reading frame of the viral TS gene, instructing a polypeptide of 33.5 kilodaltons, has extensive sequence homology with the corresponding TS coding sequences of human cells and of various procaryotes; the putative polypeptide derived from the nucleotide sequence of the herpesvirus saimiri TS gene is 70% identical with the human enzyme. The untranslated regions of the herpesvirus saimiri TS gene do not share homology with the other characterized eucaryotic or bacterial TS genes. The 5' untranslated sequence has 22 ATG triplets shortly followed by stop codons. The herpesvirus saimiri TS gene, which may be weakly transcribed during immediate early and early times of virus replication, is maximally expressed at the late phase. Various parameters suggest that the TS gene has been acquired in virus evolution by an ancestral herpesvirus from the cellular genome.

Amino Acid Sequence↗

PubMed1991

Antigenic stability of foot-and-mouth disease virus variants on serial passage in cell culture.

Two neutralizing monoclonal antibody (MAb)-resistant variants selected from an isolate of foot-and-mouth disease virus (FMDV) type A5 were repeatedly passaged in cell culture and monitored for susceptibility to neutralization by the selecting MAb. A variant isolated with a MAb to a conformational epitope (1-OG2) lost resistance in 20 passages, while a variant isolated with a MAb to a linear epitope (1-HA6) persisted for 30 passages. In both cases, the virus population emerging after passage was antigenically and genetically indistinguishable from the original wild-type parental virus (FMDV A5 Spain-86). Coinfection assays with the wild type and each variant, and between the variants, showed rapid conversion to a homogeneous population. Wild-type virus prevailed over the variants and for coinfection between the variants, the linear epitope variant 1-HA6. While both variants arose from a single nucleotide substitution and reversion to wild type occurred for each, it appears that the variant based on the continuous epitope (1-HA6) was more stable. We discuss the implications of these results for the antigenic diversity of FMDV and its relationship to virus evolution.

Animals↗

PubMed2000

The exceptionally large genome of Hendra virus: support for creation of a new genus within the family Paramyxoviridae.

An outbreak of acute respiratory disease in Hendra, a suburb of Brisbane, Australia, in September 1994 resulted in the deaths of 14 racing horses and a horse trainer. The causative agent was a new member of the family Paramyxoviridae. The virus was originally called Equine morbillivirus but was renamed Hendra virus (HeV) when molecular characterization highlighted differences between it and members of the genus Morbillivirus. Less than 5 years later, the closely related Nipah virus (NiV) emerged in Malaysia, spread rapidly through the pig population, and caused the deaths of over 100 people. We report the characterization of the HeV L gene and protein, the genome termini, and gene boundary sequences, thus completing the HeV genome sequence. In the highly conserved region of the L protein, the HeV sequence GDNE differs from the GDNQ found in almost all other nonsegmented negative-strand (NNS) RNA viruses. HeV has an absolutely conserved intergenic trinucleotide sequence, 3'-GAA-5', and highly conserved transcription initiation and termination sequences similar to those of respiroviruses and morbilliviruses. The large genome size (18,234 nucleotides), the unique complementary genome terminal sequences of HeV, and the limited homology with other members of the Paramyxoviridae suggest that HeV, together with NiV, should be classified in a new genus in this family. The large genome of HeV also fills a gap in the spectrum of genome sizes observed with NNS RNA virus genomes. As such, it provides a further piece in the puzzle of NNS RNA virus evolution.

Amino Acid Sequence↗

PubMed2006

Evidence of structural genomic region recombination in Hepatitis C virus.

BACKGROUND/AIM: Hepatitis C virus (HCV) has been the subject of intense research and clinical investigation as its major role in human disease has emerged. Although homologous recombination has been demonstrated in many members of the family Flaviviridae, to which HCV belongs, there have been few studies reporting recombination on natural populations of HCV. Recombination break-points have been identified in non structural proteins of the HCV genome. Given the implications that recombination has for RNA virus evolution, it is clearly important to determine the extent to which recombination plays a role in HCV evolution. In order to gain insight into these matters, we have performed a phylogenetic analysis of 89 full-length HCV strains from all types and sub-types, isolated all over the world, in order to detect possible recombination events. METHOD: Putative recombinant sequences were identified with the use of SimPlot program. Recombination events were confirmed by bootscaning, using putative recombinant sequence as a query. RESULTS: Two crossing over events were identified in the E1/E2 structural region of an intra-typic (1a/1c) recombinant strain. CONCLUSION: Only one of 89 full-length strains studied resulted to be a recombinant HCV strain, revealing that homologous recombination does not play an extensive roll in HCV evolution. Nevertheless, this mechanism can not be denied as a source for generating genetic diversity in natural populations of HCV, since a new intra-typic recombinant strain was found. Moreover, the recombination break-points were found in the structural region of the HCV genome.

Evolution, Molecular↗

PubMed2025

Phylogenetic diversity and molecular evolution of Hantaan virus harbored by Apodemus chejuensis on Jeju Island, Republic of Korea, 2022-2023.

BACKGROUND: Hantaan virus (HTNV), hosted by Apodemus spp., is a well-recognized causative agent of hemorrhagic fever with renal syndrome (HFRS) and poses a crucial global public health concern. Based on the current evidence, HTNV carried by A. chejuensis is proposed as the likely etiological agent of HFRS on Jeju Island, Republic of Korea (ROK). METHODOLOGY/PRINCIPAL FINDINGS: In this study, 50 small mammals were collected from five locations in Seogwipo-si and Jeju-si on Jeju Island, ROK, during 2022-2023. Serological and molecular analyses revealed HTNV prevalence rates of 34% (16/47) and 27.7% (13/47), respectively. Using a multiplex polymerase chain reaction-based nanopore sequencing approach, nine complete HTNV genomes were sequenced from the lung tissues of A. chejuensis, representing the first comprehensive genomic characterization of HTNV from Seogwipo-si (Hogeun-dong) and Jeju-si (Sangdae-ri). Phylodynamic analyses suggest evolutionary divergence and phylogeographic diversity, with four unique amino acid substitutions identified in HTNV genomes from Seogwipo-si. CONCLUSION/SIGNIFICANCE: This study provides important insights into the genomic surveillance, genetic diversity, and evolutionary dynamics of orthohantaviruses, which are essential for guiding effective public health strategies to control and prevent future HFRS outbreaks in the ROK.

Animals↗

PubMed1998

Molecular evolution of dengue type 2 virus in Thailand.

Dengue is a mosquito-borne viral infection that in recent years has become a major international public health concern. Dengue hemorrhagic fever (DHF), first recognized in Southeast Asia in the 1950s, is today a leading cause of childhood death in many countries. The pathogenesis of this illness is poorly understood, mainly because there are no laboratory or animal models of disease. We have studied the genetic relationships of dengue viruses of serotype 2, one of four antigenically distinct dengue virus groups, to determine if viruses obtained from cases of less severe dengue fever (DF) have distinct evolutionary origins from those obtained from DHF cases. A very large number (73) of virus samples from patients with DF or DHF in two locations in Thailand (Bangkok and Kamphaeng Phet) were compared by sequence analysis of 240 nucleotides from the envelope/nonstructural protein 1 (E/NS1) gene junction of the viral genome. Phylogenetic trees generated with these data have been shown to reflect long-term evolutionary relationships among strains. The results suggest that 1) many different virus variants may circulate simultaneously in Thailand, thus reflecting the quasispecies nature of these RNA viruses, in spite of population immunity; 2) viruses belonging to two previously distinct genotypic groups have been isolated from both DF and DHF cases, supporting the view that they arose from a common progenitor and share the potential to cause severe disease; and 3) viruses associated with the potential to cause DHF segregate into what is now one, large genotypic group and they have evolved independently in Southeast Asia for some time.

Dengue↗

PubMed1998

[Sequence analysis on HIV1 env V3 rigion from HIV1 infected intravenous drug users in Ruili city, Yunnan].

To study the molecular-epidemiologic features of HIV1 epidemic strains from intravenous drug users (IVDUs) in Yunnan, nested primers polymerase chain reaction was developed for the amplification of env gene V3 fragment of HIV1 strains. DNA sequencing and analysis were performed with these fragments. Results showed that the variation of HIV1 gp120 V3 amino acids sequences among 16 HIV1, strains was averaged 7% (0%-23%), when comparing their consensus sequence. The amino acids consensus sequences of gp120 V3 region showed that more than 90% of homology compared with that of HIV1 SF2 strain and HIV1 American-European strain. However, lower homology with that of HIV1 strains from Haiti, Japan and Africa was revealed. The results suggested that there was a close relation among these 16 HIV1 epidemic strains isolated in Yunnan Ruili in terms of virus evolution. The epidemic HIV1 strains in the area were predominately American-European, SF2 and their derivatives in this period.

Acquired Immunodeficiency Syndrome↗

PubMed1999

[Natural interspecific hybrids of transposable phages of Pseudomonas aeruginosa].

Bacterial viruses of Pseudomonas aeruginosa assigned to two groups, D3112 and B3, recombine with very low frequencies. Previous study of the genome structure of intergroup hybrids suggested the incompatibility of some genetic modules of these bacteriophages. In this work, several natural hybrid transposable phages that had the genomes largely consisting of modules of phages from group D3112 and B3, were described. The discovery of these phages suggests the continuous genetic exchange in nature of these viruses belonging to different species. This model is considered as promising from the viewpoint of monitoring virus evolution.

DNA Transposable Elements↗

PubMed2000

[Virokines and viroceptors--viral immunomodulators with clinical and therapeutic implications].

During evolution viruses have developed variety of sophisticated strategies for interactions with the immune system of the host. One of the defense strategies that counteract the immune responses of the infected organism exploits viral proteins that directly interfere with the host's cytokine system. Among such immunomodulatory molecules are classed also viral homologs of cytokines (virokines) and viral homologs of cytokine receptors (viroceptors), produced and secreted by the virus-infected cell. Virokines and viroceptors are encoded by large DNA viruses--herpesviruses and poxviruses. The respective genes have been obviously "stolen" by viruses from the host genomes and then have been modified. Detailed characterization of these viral elements, which induce or subvert the host's cytokine responses against viral infection, may contribute to a better understanding of the mechanisms which help the viruses to escape immune surveillance. Such knowledge have potential implications for viral epidemiology, treatment or prevention of viral and inflammatory diseases, and for the development of safer vaccines. Examples of viruses indicate, that "capturing" of the immunomodulatory genes may be a more general strategy used also by other types of pathogenic or parasitic organisms to evade the immune responses of their hosts. (Tab. 2, Fig. 2, Ref. 73.)

Adjuvants, Immunologic↗

PubMed2002

Origin and evolution of influenza virus hemagglutinin genes.

Influenza A, B, and C viruses are the etiological agents of influenza. Hemagglutinin (HA) is the major envelope glycoprotein of influenza A and B viruses, and hemagglutinin-esterase (HE) in influenza C viruses is a protein homologous to HA. Because influenza A virus pandemics in humans appear to occur when new subtypes of HA genes are introduced from aquatic birds that are known to be the natural reservoir of the viruses, an understanding of the origin and evolution of HA genes is of particular importance. We therefore conducted a phylogenetic analysis of HA and HE genes and showed that the influenza A and B virus HA genes diverged much earlier than the divergence between different subtypes of influenza A virus HA genes. The rate of amino acid substitution for A virus HAs from duck, a natural reservoir, was estimated to be 3.19 x 10(-4) per site per year, which was slower than that for human and swine A virus HAs but similar to that for influenza B and C virus HAs (HEs). Using this substitution rate from the duck, we estimated that the divergences between different subtypes of A virus HA genes occurred from several thousand to several hundred years ago. In particular, the earliest divergence time was estimated to be about 2,000 years ago. Also, the A virus HA gene diverged from the B virus HA gene about 4,000 years ago and from the C virus HE gene about 8,000 years ago. These time estimates are much earlier than the previous ones.

Amino Acid Sequence↗

PubMedDate not supplied

The role of viruses in the evolution of antibody diversity.

We propose an alternate concept for the creation of antibody diversity involving the role of viruses as mediators of genetic exchange. We suggest that both species specificity and the diversity of the immune response arose as a consequence of virus co-evolution with host organisms. Processes such as viral transformation, transduction, and integration provide mechanisms of nucleotide exchange with the host leading to antibody diversity. In this model the genes coding for antibodies are stabilized through a process of antigenic and natural selection. Stabilization of genes ensures vertical transmission of appropriate nucleotide sequences.

Antibody Specificity↗

PubMed2002

Rates of molecular evolution in RNA viruses: a quantitative phylogenetic analysis.

The study of rates of nucleotide substitution in RNA viruses is central to our understanding of their evolution. Herein we report a comprehensive analysis of substitution rates in 50 RNA viruses using a recently developed maximum likelihood phylogenetic method. This analysis revealed a significant relationship between genetic divergence and isolation time for an extensive array of RNA viruses, although more rate variation was usually present among lineages than would be expected under the constraints of a molecular clock. Despite the lack of a molecular clock, the range of statistically significant variation in overall substitution rates was surprisingly narrow for those viruses where a significant relationship between genetic divergence and time was found, as was the case when synonymous sites were considered alone, where the molecular clock was rejected less frequently. An analysis of the ecological and genetic factors that might explain this rate variation revealed some evidence of significantly lower substitution rates in vector-borne viruses, as well as a weak correlation between rate and genome length. Finally, a simulation study revealed that our maximum likelihood estimates of substitution rates are valid, even if the molecular clock is rejected, provided that sufficiently large data sets are analyzed.

Amino Acid Substitution↗

PubMed2005

Differential evolution of cell-associated virus in blood and genital tract of HIV-infected females undergoing HAART.

PBMC and vaginal cell (VC) viruses were studied from 5 HIV-infected females for the presence of drug-resistance and non-drug resistance associated mutations. A 1318-bp fragment of polymerase gene was amplified from PBMC and VC proviral DNA. Four of the 5 PBMC viruses exhibited drug resistance-associated mutations in reverse transcriptase and protease genes, whereas only 2 VC viruses contained drug resistance-associated mutations. However, all 5 females showed non-drug resistance-associated mutations both in PBMC and VC virus suggesting continuous evolution of the virus in these compartments. The emergence of drug resistance was slower in PBMC and VC viruses than that observed in the cell-free plasma (P) and vaginal secretion (VS) viruses. Phylogenetic analysis revealed that VC virus was closer to PBMC virus than either cell-free viruses (P and VS) suggesting comparable evolution among cell-associated viruses.

Adult↗

PubMed2004

Genotypic analysis of HIV-1 drug resistance at the limit of detection: virus production without evolution in treated adults with undetectable HIV loads.

Human immunodeficiency virus (HIV) production continues in patients receiving highly active antiretroviral therapy (HAART) with undetectable (<50 copies/mL) virus loads. Our initial cross-sectional study showed that this viremia is composed of viruses that lack new resistance mutations to the HAART regimen. Here we describe a longitudinal, clonal genotypic analysis of plasma virus loads in treated adults who had undetectable virus loads. We document a continuous production of virus in 8 HIV-1-infected adults who maintained suppression of viremia for up to 15 months. Using analytical approaches for distinguishing selected resistance mutations from nonselected mutations and polymerase chain reaction errors, we detected no evolution of resistance in the reverse-transcriptase and protease genes. Sporadic resistance mutations were detected in some viral clones that were not selected for subsequently. Thus, in some patients, HAART suppresses replication to a level that does not allow the evolution of drug resistance over a time frame of years.

Adult↗

PubMed2001

Spike gene analysis of the DE072 strain of infectious bronchitis virus: origin and evolution.

The entire S2 gene of the DE072 strain of infectious bronchitis virus (IBV) was sequenced. The nucleotide and amino acid sequence was most similar to the D1466 strain and was 84.8% and 89.9% identity, respectively. The nucleotide and amino acid sequence similarity among the DE072 strain and other IBV strains was less than 71.9% and 76.6%, respectively. Phylogenetic analysis, based on both nucleotide and amino acid sequence, showed that IBV isolates were divided into two distinct groups. The DE072 strain clustered only with the D1466 strain, and all of the other strains were distinct from those two viruses. Further the nucleotide sequence analysis of the entire spike glycoprotein gene of the DE072 strain demonstrated that most of the gene contained a D1466-like sequence, and five putative cross-over sites were identified. Based on cross-over site, phylogenetic trees were constructed for different regions of the spike gene, and a difference in topology between these trees was observed. Considering the difference in S2 gene sequence identity and tree topology, we assume that DE072 and D1466 viruses share a different origin from other isolates of IBV. Furthermore, entire spike gene analysis indicates that the DE072 strain has undergone recombination event as well as extensive antigenic variation.

Amino Acid Sequence↗

PubMed1995

Intrahost human immunodeficiency virus type 1 evolution is related to length of the immunocompetent period.

The antigenic diversity threshold theory predicts that antigenic sites of human immunodeficiency virus type 1, such as the V3 region of the external glycoprotein gp120, evolve more rapidly during the symptom-free period in individuals progressing to AIDS than in those who remain asymptomatic for a long time. To test this hypothesis, genomic RNA sequences were obtained from the sera of 44 individuals at seroconversion and 5 years later. The mean number of nonsynonymous nucleotide substitutions in the V3 region of the viruses circulating in 31 nonprogressors (1.1 x 10(-2) +/- 0.1 x 10(-2) per site per year) was higher than the corresponding value for 13 progressors (0.66 x 10(-2) +/- 0.1 x 10(-2) per site per year) (P < 0.01), while no difference between the mean numbers of synonymous substitutions in the two groups was seen (0.37 x 10(-2) +/- 0.1 x 10(-2) and 0.51 x 10(-2) +/- 0.2 x 10(-2) per site per year for nonprogressors and progressors, respectively; P > 0.1). The mean ratios of synonymous nucleotide p distance to nonsynonymous p distance were 0.35 for nonprogressors and 0.62 for progressors. The number of nonsynonymous substitutions was not associated with virus load or virus phenotype, which are established predictors of disease progression, but correlated strongly with the duration of the immunocompetent period (r2 = 0.41; P = 0.001). This indicates that there is no causative relationship between intrahost evolution and CD4+ cell decline. Our data suggest that intrahost evolution in human immunodeficiency virus type 1 infection is driven by selective forces, the strength of which is related to the duration of the immunocompetent period.

Acquired Immunodeficiency Syndrome↗

PubMed2002

Genetic constraints and the adaptive evolution of rabies virus in nature.

We used a molecular evolutionary approach to investigate the species adaptation of rabies virus in nature. A maximum likelihood analysis of selection pressures revealed that the nucleoprotein (N) and glycoprotein (G) genes of natural viral isolates were highly constrained, especially at nonsynonymous sites, in contrast to the higher rates of nonsynonymous evolution observed in viruses subject to laboratory passage. Positive selection was only found at a single amino acid site--position 183 in the ectodomain of the G gene. The low rate of nonsynonymous evolution in natural isolates of rabies virus may be due to constraints imposed by the need to replicate in multiple cell types within the host, which in turn facilitates cross-species transmission, or because viral proteins are not subject to immune selection. Using known dates in the epidemiologic history of European viral isolates, we estimated that overall rates of nucleotide substitution in rabies virus were similar to those observed in other RNA viruses. Assuming that the average rate of synonymous change does not vary among species, we estimated that the current genetic diversity in lyssavirus genotype 1 may have arisen only during the last 500 years.

Adaptation, Physiological↗

PubMed1995

Nucleotide sequence variation of the envelope protein gene identifies two distinct genotypes of yellow fever virus.

The evolution of yellow fever virus over 67 years was investigated by comparing the nucleotide sequences of the envelope (E) protein genes of 20 viruses isolated in Africa, the Caribbean, and South America. Uniformly weighted parsimony algorithm analysis defined two major evolutionary yellow fever virus lineages designated E genotypes I and II. E genotype I contained viruses isolated from East and Central Africa. E genotype II viruses were divided into two sublineages: IIA viruses from West Africa and IIB viruses from America, except for a 1979 virus isolated from Trinidad (TRINID79A). Unique signature patterns were identified at 111 nucleotide and 12 amino acid positions within the yellow fever virus E gene by signature pattern analysis. Yellow fever viruses from East and Central Africa contained unique signatures at 60 nucleotide and five amino acid positions, those from West Africa contained unique signatures at 25 nucleotide and two amino acid positions, and viruses from America contained such signatures at 30 nucleotide and five amino acid positions in the E gene. The dissemination of yellow fever viruses from Africa to the Americas is supported by the close genetic relatedness of genotype IIA and IIB viruses and genetic evidence of a possible second introduction of yellow fever virus from West Africa, as illustrated by the TRINID79A virus isolate. The E protein genes of American IIB yellow fever viruses had higher frequencies of amino acid substitutions than did genes of yellow fever viruses of genotypes I and IIA on the basis of comparisons with a consensus amino acid sequence for the yellow fever E gene. The great variation in the E proteins of American yellow fever virus probably results from positive selection imposed by virus interaction with different species of mosquitoes or nonhuman primates in the Americas.

Aedes↗