scholarly journals Equine Infectious Anemia Virus Genomic Evolution in Progressor and Nonprogressor Ponies

2001 ◽  
Vol 75 (10) ◽  
pp. 4570-4583 ◽  
Author(s):  
Caroline Leroux ◽  
Jodi K. Craigo ◽  
Charles J. Issel ◽  
Ronald C. Montelaro
Keyword(s):  
Steady State ◽  
Viral Replication ◽  
Virus Replication ◽  
Equine Infectious Anemia Virus ◽  
Genomic Rna ◽  
Equine Infectious Anemia ◽  
Steady State Levels ◽  
Anemia Virus ◽  
First Time

ABSTRACT A primary mechanism of lentivirus persistence is the ability of these viruses to evolve in response to biological and immunological selective pressures with a remarkable array of genetic and antigenic variations that constitute a perpetual natural experiment in genetic engineering. A widely accepted paradigm of lentivirus evolution is that the rate of genetic variation is correlated directly with the levels of virus replication: the greater the viral replication, the more opportunities that exist for genetic modifications and selection of viral variants. To test this hypothesis directly, we examined the patterns of equine infectious anemia virus (EIAV) envelope variation during a 2.5-year period in experimentally infected ponies that differed markedly in clinical progression and in steady-state levels of viral replication as indicated by plasma virus genomic RNA assays. The results of these comprehensive studies revealed for the first time similar extents of envelope gp90 variation in persistently infected ponies regardless of the number of disease cycles (one to six) and viremia during chronic disease. The extent of envelope variation was also independent of the apparent steady-state levels of virus replication during long-term asymptomatic infection, varying from undetectable to 105 genomic RNA copies per ml of plasma. In addition, the data confirmed the evolution of distinct virus populations (genomic quasispecies) associated with sequential febrile episodes during acute and chronic EIA and demonstrated for the first time ongoing envelope variation during long-term asymptomatic infections. Finally, comparison of the rates of evolution of the previously defined EIAV gp90 variable domains demonstrated distinct differences in the rates of nucleotide and amino acid sequence variation, presumably reflecting differences in the ability of different envelope domains to respond to immune or other biological selection pressures. Thus, these data suggest that EIAV variation can be associated predominantly with ongoing low levels of virus replication and selection in target tissues, even in the absence of substantial levels of plasma viremia, and that envelope variation continues during all stages of persistent infection as the virus successfully avoids clearance by host defense mechanisms.

scholarly journals Tissue Sites of Persistent Infection and Active Replication of Equine Infectious Anemia Virus during Acute Disease and Asymptomatic Infection in Experimentally Infected Equids

2000 ◽  
Vol 74 (7) ◽  
pp. 3112-3121 ◽  
Author(s):  
Sharon M. Harrold ◽  
Sheila J. Cook ◽  
R. Frank Cook ◽  
Keith E. Rushlow ◽  
Charles J. Issel ◽  
...  
Keyword(s):  
Viral Infection ◽  
Virus Replication ◽  
Equine Infectious Anemia Virus ◽  
Clinical Symptoms ◽  
Acute Disease ◽  
Viral Dna ◽  
Dna And Rna ◽  
Equine Infectious Anemia ◽  
Anemia Virus

ABSTRACT Equine infectious anemia virus (EIAV) infection of horses is characterized by recurring cycles of disease and viremia that typically progress to an inapparent infection in which clinical symptoms are absent as host immune responses maintain control of virus replication indefinitely. The dynamics of EIAV viremia and its association with disease cycles have been well characterized, but there has been to date no comprehensive quantitative analyses of the specific tissue sites of EIAV infection and replication in experimentally infected equids during acute disease episodes and during asymptomatic infections in long-term inapparent carriers. To characterize the in vivo site(s) of viral infection and replication, we developed a quantitative competitive PCR assay capable of detecting 10 copies of viral DNA and a quantitative competitive reverse transcription-PCR assay with a sensitivity of about 30 copies of viral singly spliced mRNA. Animals were experimentally infected with one of two reference viruses: the animal-passaged field isolate designated EIAVWyo and the virulent cell-adapted strain designated EIAVPV. Tissues and blood cells were isolated during the initial acute disease or from asymptomatic animals and analyzed for viral DNA and RNA levels by the respective quantitative assays. The results of these experiments demonstrated that the appearance of clinical symptoms in experimentally infected equids coincided with rapid widespread seeding of viral infection and replication in a variety of tissues. During acute disease, the predominant cellular site of viral infection and replication was the spleen, which typically accounted for over 90% of the cellular viral burden. In asymptomatic animals, viral DNA and RNA persisted in virtually all tissues tested, but at extremely low levels, a finding indicative of tight but incomplete immune control of EIAV replication. During all disease states, peripheral blood mononuclear cells (PBMC) were found to harbor less than 1% of the cellular viral burden. These quantitative studies demonstrate that tissues, rather than PBMC, constitute the predominant sites of virus replication during acute disease in infected equids and serve as resilient reservoirs of virus infection, even in the presence of highly effective immune responses that maintain a stringent control of virus replication in long-term inapparent carriers. Thus, these observations with EIAV, a predominantly macrophage-tropic lentivirus, highlight the role of tissues in sequestering lentiviral infections from host immune surveillance.

scholarly journals Equine Infectious Anemia Virus Gag p9 Function in Early Steps of Virus Infection and Provirus Production

2005 ◽  
Vol 79 (14) ◽  
pp. 8793-8801 ◽  
Author(s):  
Sha Jin ◽  
Chaoping Chen ◽  
Ronald C. Montelaro
Keyword(s):  
Amino Acids ◽  
Equine Infectious Anemia Virus ◽  
Critical Role ◽  
Productive Infection ◽  
Viral Dna ◽  
Virus Particles ◽  
Viral Budding ◽  
Equine Infectious Anemia ◽  
Anemia Virus ◽  
First Time

ABSTRACT We have previously reported that serial truncation of the Gag p9 protein of equine infectious anemia virus (EIAV) revealed a progressive loss in replication phenotypes in transfected cells, such that a proviral mutant (E32) expressing the N-terminal 31 amino acids of p9 produced infectious virus particles similarly to parental provirus, while a proviral mutant (K30) with two fewer amino acids produced replication-defective virus particles, despite containing apparently normal levels of processed Gag and Pol proteins (C. Chen, F. Li, and R. C. Montelaro, J. Virol. 75:9762-9760, 2001). Based on these observations, we sought in the current study to identify the precise defect in K30 virion infection of permissive equine dermal (ED) cells. The results of these experiments clearly demonstrated that K30 virions entered target ED cells and produced early (minus-strand strong-stop) and late (Gag) viral DNA products as efficiently as did the replication-competent E32 mutant and parental EIAVUK viruses. However, in contrast to the replication-competent E32 mutant and parental viruses, infection with K30 mutant virus failed to produce detectable two-long-terminal-repeat DNA circles, stable integrated provirus, virus-specific Gag mRNA expression, or intracellular viral protein expression. Taken together, these data demonstrate that the K30 mutant is defective in the ability to produce sufficient nuclear viral DNA to establish a productive infection in ED cells. Thus, these observations indicate for the first time that the EIAV Gag p9 protein performs a critical role in viral DNA production and processing to provirus during EIAV infection, in addition to its previously defined role in viral budding mediated by the p9 L domain.

scholarly journals Effects of Long Terminal Repeat Sequence Variation on Equine Infectious Anemia Virus Replication in Vitro and in Vivo

Virology ◽  
1999 ◽  
Vol 263 (2) ◽  
pp. 408-417 ◽  
Author(s):  
Drew L. Lichtenstein ◽  
Jodi K. Craigo ◽  
Caroline Leroux ◽  
Keith E. Rushlow ◽  
R.Frank Cook ◽  
...  
Keyword(s):  
Long Terminal Repeat ◽  
Virus Replication ◽  
Sequence Variation ◽  
Equine Infectious Anemia Virus ◽  
Repeat Sequence ◽  
Equine Infectious Anemia ◽  
Anemia Virus ◽  
Terminal Repeat Sequence

scholarly journals The S2 Gene of Equine Infectious Anemia Virus Is Dispensable for Viral Replication In Vitro

1998 ◽  
Vol 72 (10) ◽  
pp. 8344-8348 ◽  
Author(s):  
Feng Li ◽  
Bridget A. Puffer ◽  
Ronald C. Montelaro
Keyword(s):  
Equine Infectious Anemia Virus ◽  
Parental Virus ◽  
Target Cells ◽  
Monocyte Differentiation ◽  
Cell Culture Systems ◽  
Equine Infectious Anemia ◽  
Anemia Virus ◽  
First Time

ABSTRACT Equine infectious anemia virus (EIAV) contains the simplest genome among lentiviruses in that it encodes only three putative regulatory genes (S1, S2, S3) in addition to the canonical gag, pol, and envgenes, presumably reflecting its limited tropism to cells of monocyte/macrophage lineage. Tat and Rev functions have been assigned to S1 and S3, respectively, but the specific function for the S2 gene has yet to be determined. Thus, the function of S2 in virus replication in vitro was investigated by using an infectious molecular viral clone, EIAVUK. Various EIAVUK mutants lackingS2 were constructed, and their replication kinetics were examined in several equine cell culture systems, including the natural in vivo target equine macrophage cells. The EIAV S2 mutants showed replication kinetics similar to those of the parental virus in all of the tested primary and transformed equine cell cultures, without any detectable reversion of mutant genomes. The EIAVUKmutants also showed replication kinetics similar to those of the parental virus in an equine blood monocyte differentiation-maturation system. These results demonstrate for the first time that the EIAVS2 gene is not essential and does not appear to affect virus infection and replication properties in target cells in vitro.

scholarly journals Gag Protein Epitopes Recognized by ELA-A-Restricted Cytotoxic T Lymphocytes from Horses with Long-Term Equine Infectious Anemia Virus Infection

1998 ◽  
Vol 72 (12) ◽  
pp. 9612-9620 ◽  
Author(s):  
Wei Zhang ◽  
Scott M. Lonning ◽  
Travis C. McGuire
Keyword(s):  
T Lymphocytes ◽  
Cytotoxic T Lymphocytes ◽  
Equine Infectious Anemia Virus ◽  
Class I ◽  
Target Cells ◽  
Ctl Epitopes ◽  
Peptide Epitopes ◽  
Equine Infectious Anemia ◽  
Anemia Virus

ABSTRACT Most equine infectious anemia virus (EIAV)-infected horses have acute clinical disease, but they eventually control the disease and become lifelong carriers. Cytotoxic T lymphocytes (CTL) are considered an important immune component in the control of infections with lentiviruses including EIAV, but definitive evidence for CTL in the control of disease in carrier horses is lacking. By using retroviral vector-transduced target cells expressing different Gag proteins and overlapping synthetic peptides of 16 to 25 amino acids, peptides containing at least 12 Gag CTL epitopes recognized by virus-stimulated PBMC from six long-term EIAV-infected horses were identified. All identified peptides were located within Gag matrix (p15) and capsid (p26) proteins, as no killing of target cells expressing p11 and p9 occurred. Each of the six horses had CTL recognizing at least one Gag epitope, while CTL from one horse recognized at least eight different Gag epitopes. None of the identified peptides were recognized by CTL from all six horses. Two nonamer peptide epitopes were defined from Gag p26; one (18a) was likely restricted by class I equine leukocyte alloantigen A5.1 (ELA-A5.1) molecules, and the other (28b-1) was likely restricted by ELA-A9 molecules. Sensitization of equine kidney target cells for CTLm killing required 10 nM peptide 18a and 1 nM 28b-1. The results demonstrated that diverse CTL responses against Gag epitopes were generated in long-term EIAV-infected horses and indicated that ELA-A class I molecules were responsible for the diversity of CTL epitopes recognized. This information indicates that multiple epitopes or whole proteins will be needed to induce CTL in horses with different ELA-A alleles in order to evaluate their role in controlling EIAV.

scholarly journals High Genomic Variability in Equine Infectious Anemia Virus Obtained from Naturally Infected Horses in Pantanal, Brazil: An Endemic Region Case

Viruses ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 207 ◽  
Author(s):  
Camila Dantas Malossi ◽  
Eduardo Gorzoni Fioratti ◽  
Jedson Ferreira Cardoso ◽  
Angelo Jose Magro ◽  
Erna Geessien Kroon ◽  
...  
Keyword(s):  
Amino Acid ◽  
Equine Infectious Anemia Virus ◽  
Genomic Sequences ◽  
Endemic Region ◽  
Viral Genomes ◽  
Equine Infectious Anemia ◽  
Anemia Virus ◽  
Next Generation Sequencing Ngs ◽  
First Time ◽  
Generation Sequencing

Equine infectious anemia virus (EIAV) is a persistent lentivirus that causes equine infectious anemia (EIA). In Brazil, EIAV is endemic in the Pantanal region, and euthanasia is not mandatory in this area. All of the complete genomic sequences from field viruses are from North America, Asia, and Europe, and only proviral genomic sequences are available. Sequences from Brazilian EIAV are currently available only for gag and LTR regions. Thus, the present study aimed for the first time to sequence the entire EIAV genomic RNA in naturally infected horses from an endemic area in Brazil. RNA in plasma from naturally infected horses was used for next-generation sequencing (NGS), and gaps were filled using Sanger sequencing methodology. Complete viral genomes of EIAV from two horses were obtained and annotated (Access Number: MN560970 and MN560971). Putative genes were analyzed and compared with previously described genes, showing conservation in gag and pol genes and high variations in LTR and env sequences. Amino acid changes were identified in the p26 protein, one of the most common targets used for diagnosis, and p26 molecular modelling showed surface amino acid alterations in some epitopes. Brazilian genome sequences presented 88.6% nucleotide identity with one another and 75.8 to 77.3% with main field strains, such as EIAV Liaoning, Wyoming, Ireland, and Italy isolates. Furthermore, phylogenetic analysis suggested that this Brazilian strain comprises a separate monophyletic group. These results may help to better characterize EIAV and to overcome the challenges of diagnosing and controlling EIA in endemic regions.

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