Topic:Equine Infectious Anemia
Equine Infectious Anemia (EIA) is a viral disease affecting horses, caused by the Equine Infectious Anemia Virus (EIAV), a member of the Lentivirus genus. The disease is characterized by intermittent fever, anemia, edema, and weight loss, though some horses may remain asymptomatic carriers. Transmission occurs primarily through blood-feeding insects such as horseflies and deerflies, or through contaminated instruments. EIA is diagnosed using serological tests, with the Coggins test being a commonly used method for detection. There is no vaccine or cure for EIA, and management primarily focuses on prevention and control measures to limit transmission. This page assembles peer-reviewed studies and scholarly articles that explore the pathogenesis, epidemiology, diagnostic methods, and management strategies related to Equine Infectious Anemia.
Equine infectious anemia virus envelope evolution in vivo during persistent infection progressively increases resistance to in vitro serum antibody neutralization as a dominant phenotype. Equine infectious anemia virus (EIAV) infection of horses is characterized by well-defined waves of viremia associated with the sequential evolution of distinct viral populations displaying extensive envelope gp90 variation; however, a correlation of in vivo envelope evolution with in vitro serum neutralization phenotype remains undefined. Therefore, the goal of the present study was to utilize a previously defined panel of natural variant EIAV envelope isolates from sequential febrile episodes to characterize the effects of envelope variation during persistent infection on viral neutralizatio...
Development of a multiplex real-time reverse transcriptase-polymerase chain reaction for equine infectious anemia virus (EIAV). A single-tube reverse transcriptase-polymerase chain reaction (RT-PCR) using a fluorogenic real-time PCR detection method is described for the quantitation of equine infectious anemia virus (EIAV) RNA in the plasma of equids. To compensate for variations inherent in sample preparation a multiplex real-time RT-PCR system was developed that permitted the simultaneous calculation of the nucleic acid recovery rate along with the copy number of viral RNA molecules. Detection of EIAV RNA was linear from 10(9) to 10(1) molecules with intra- and inter-assay variability of less than 1% at 10(8), 10(6),...
Multiple RNA splicing and the presence of cryptic RNA splice donor and acceptor sites may contribute to low expression levels and poor immunogenicity of potential DNA vaccines containing the env gene of equine infectious anemia virus (EIAV). The env gene is an excellent candidate for inclusion in any DNA-based vaccine approach against equine infectious anemia virus (EIAV). Unfortunately, this gene is subjected to mutational pressure in E. coli resulting in the introduction of stop codons at the 5' terminus unless it is molecularly cloned using very-low-copy-number plasmid vectors. To overcome this problem, a mammalian expression vector was constructed based on the low-copy-number pLG338-30 plasmid. This permitted the production of full-length EIAV env gene clones (plcnCMVenv) from which low-level expression of the viral surface un...
Transient immune suppression of inapparent carriers infected with a principal neutralizing domain-deficient equine infectious anaemia virus induces neutralizing antibodies and lowers steady-state virus replication. The genetic variation of equine infectious anaemia virus (EIAV) clearly affects the antigenic properties of the viral envelope; however, effects on immunogenicity remain undefined, although widely assumed. Here, the immunogenicity is reported of a novel, neutralization-resistant, pony-isolate envelope EIAV(PV564DeltaPND) that contains a 14-residue deletion in the designated principal neutralizing domain (PND) of the gp90 protein. Two ponies inoculated with a chimeric virus, EIAV(DeltaPND), containing the EIAV(PV564DeltaPND) envelope in a reference provirus strain, remained asymptomatic through...
Seroprevalence of antibodies against Neospora caninum in diagnostic equine serum samples and their possible association with fetal loss. A case-control study of the association between the presence of serum antibodies against Neospora spp. and fetal loss was performed on serum samples submitted to a veterinary diagnostic laboratory in northwestern United States. Control sera were randomly selected from those submitted from healthy horses for routine equine infectious anemia testing required for regulatory health certification. Case sera were randomly selected from those submitted from aborting mares for diagnostic workup. Based on a 1:50 or greater titer on the indirect fluorescent antibody test, 8% of the 160 control sera and ...
Identification of broadly recognized, T helper 1 lymphocyte epitopes in an equine lentivirus. Equine infectious anaemia virus (EIAV) is a horse lentivirus causing lifelong, persistent infection. During acute infection, CD8(+) cytotoxic T lymphocytes (CTL) are probably involved in terminating plasma viraemia. However, only a few EIAV CTL epitopes, restricted to fewer horse major histocompatibility complex (MHC) class I alleles, are known. As interferon-gamma (IFN-gamma)-secreting CD4(+), T helper 1 (Th1) lymphocytes promote CTL activity and help maintain memory CTL, identifying broadly recognized EIAV Th1 epitopes would contribute significantly to vaccine strategies seeking to promote s...
Lipopeptide stimulation of MHC class I-restricted memory cytotoxic T lymphocytes from equine infectious anemia virus-infected horses. The immunogenicity of equine infectious anemia virus (EIAV) Gag and Env equine leukocyte alloantigen (ELA)-A5.1, -A9, and -A1 restricted cytotoxic T lymphocyte (CTL) epitopes synthesized on multiple antigenic peptide (MAP) system coupled to tripalmitoyl-S-glycerylcysteine (P3C) was evaluated in vitro. P3C-MAP-peptide-stimulated peripheral blood mononuclear cells (PBMCs) from horses, chronically infected with EIAV, had memory CTL (CTLm) similar to that of PBMCs stimulated with either the minimal CTL epitopes, longer peptides containing the CTL epitopes, or EIAV. The stimulated CTL lysed EIAV-in...
Equine infectious anemia virus and the ubiquitin-proteasome system. Some retroviruses contain monoubiquitinated Gag and do not bud efficiently from cells treated with proteasome inhibitors, suggesting an interaction between the ubiquitin-proteasome system and retrovirus assembly. We examined equine infectious anemia virus (EIAV) particles and found that approximately 2% of the p9(Gag) proteins are monoubiquitinated, demonstrating that this Gag protein interacts with an ubiquitinating activity. Different types of proteasome inhibitors were used to determine if proteasome inactivation affects EIAV release from chronically infected cells. Pulse-chase immunoprecip...
Budding of equine infectious anemia virus is insensitive to proteasome inhibitors. The only retrovirus protein required for the budding of virus-like particles is the Gag protein; however, recent studies of Rous sarcoma virus (RSV) and human immunodeficiency virus have suggested that modification of Gag with ubiquitin (Ub) is also required. As a consequence, the release of these viruses is reduced in the presence of proteasome inhibitors, which indirectly reduce the levels of free Ub within the cell. Here we show that the budding of equine infectious anemia virus (EIAV) from infected equine cells is largely unaffected by these drugs, although use of one inhibitor (MG-132) re...
Structure of equine infectious anemia virus matrix protein. The Gag polyprotein is key to the budding of retroviruses from host cells and is cleaved upon virion maturation, the N-terminal membrane-binding domain forming the matrix protein (MA). The 2.8-A resolution crystal structure of MA of equine infectious anemia virus (EIAV), a lentivirus, reveals that, despite showing no sequence similarity, more than half of the molecule can be superimposed on the MAs of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV). However, unlike the structures formed by HIV-1 and SIV MAs, the oligomerization state observed is not trimeric...
Comparison of gene transfer efficiencies and gene expression levels achieved with equine infectious anemia virus- and human immunodeficiency virus type 1-derived lentivirus vectors. This report compares gene transfer efficiencies as well as durations and levels of gene expression for human immunodeficiency virus (HIV) and equine infectious anemia virus (EIAV) lentiviral vectors in a variety of human cell types in vitro. EIAV and HIV vectors transduced equivalent numbers of proliferating and G1/S- and G2/M-arrested cells, and both had very low efficiencies of transduction into G0-arrested cells. Analysis of the levels of both the enhanced green fluorescent protein (EGFP) and mRNA demonstrated that the HIV-transduced cells expressed greater levels of EGFP protein and RNA th...
The role of international transport of equine semen on disease transmission. Despite the numerous benefits of having the capability to transport semen internationally, there are serious potential ramifications if that semen is contaminated with a communicable disease. Bacteria: Many commensal bacteria colonize the exterior of the stallion penis and are not regarded as pathogenic. They may be cultured from an ejaculate. Alterations of the normal bacterial flora on the exterior genitalia may cause the growth of opportunistic bacteria such as Klebsiella pneumonia, Pseudomonas aeruginosa, Streptococcus zooepidemicus, which, if inseminated, may cause infertility in suscepti...
Immune reconstitution prevents continuous equine infectious anemia virus replication in an Arabian foal with severe combined immunodeficiency: lessons for control of lentiviruses. Acute infection with equine infectious anemia virus (EIAV), a lentivirus of horses, results in a persistent high-level viremia in Arabian foals affected with severe combined immunodeficiency (SCID). This observation argues against the idea that the transient nature of acute lentiviral viremia is solely a function of viral population dynamics. To extend these studies, EIAV-specific immune reconstitution was attempted prior to EIAV challenge in two SCID foals, using adoptively transferred virus-stimulated lymphocytes derived from persistently EIAV-infected half sibling donors. Following transfer...
DH82 cells: a macrophage cell line for the replication and study of equine infectious anemia virus. In vivo, tissue macrophages have been implicated as an important cell for the replication of equine infectious anemia virus (EIAV). Laboratory investigations of EIAV/macrophage interactions, however, have been hampered by the laborious blood monocyte isolation procedures. In addition, adherent equine macrophage cultures generally have poor long-term viability and are resistant to transfection. This report describes an adherent canine macrophage-like cell line, DH82, that supports the replication of EIAV. This cell line was easily transfectable and supported EIAV Tat transactivation of the LTR....
Detection of horses infected naturally with equine infectious anemia virus by nested polymerase chain reaction. A nested polymerase chain reaction (PCR) amplifying a region of the gag gene of equine infectious anemia virus (EIAV) was developed for the rapid and direct detection of proviral DNA from the peripheral blood of naturally infected horses and was compared with the Coggins test. DNA prepared from white blood cells of 122 field horses from 15 stables with reported cases of EIAV and one seronegative stable were analysed. Amplifications of expected size fragments were obtained by nested PCR for 88 horses using two different sets of primers targeting the gag region. The specificity of the amplified ...
Equine infectious anemia virus genomic evolution in progressor and nonprogressor ponies. 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 ex...
Cross reaction of recombinant equine infectious anemia virus antigen to heterologous strains and application for serological survey among horses in the field. Cross reactivity of equine infectious anemia virus (EIAV) antigen prepared using a recombinant baculovirus containing the p26 gene of strain P337-V70 was examined by the agar gel immunodiffusion (AGID) test and enzyme-linked immunosorbent assay (ELISA). Serum samples serially collected from 13 horses experimentally infected with six different EIAV strains (two or three horses per strain) were subjected to the test. Positive reactions were observed in the AGID test and ELISA before or soon after the first feverish period and continued persistently in most of the horses. The results with recombi...
Design and validation of an ELISA for equine infectious anemia (EIA) diagnosis using synthetic peptides. Three peptides derived from the equine infectious anemia virus (EIAV) surface proteins were synthesized to design and validate an ELISA for EIA diagnosis. Peptides identified as gp90-I and gp90-II correspond to the N- and C-terminal part of the surface glycoprotein gp90. Peptide gp45-1 overlaps the immunodominant epitope CIERTHVFC of the transmembrane glycoprotein gp45, and includes a hydrophilic chain close to the N-terminal end of this nonapeptide loop. Serum samples from 140 naturally infected horses with EIAV and a panel of 167 non-immune equine sera obtained from non-infected animals were...
Differential responses of Equus caballus and Equus asinus to infection with two pathogenic strains of equine infectious anemia virus. Most in vivo studies with equine infectious anemia virus (EIAV) have been performed in horses and ponies (Equus caballus) with little published information available detailing the clinical responses of donkeys (Equus asinus) to infection with this virus. Consequently, donkeys were inoculated with two strains of EIAV (EIAV(PV) and EIAV(WY)) which have been documented to produce disease in E. caballus. Four ponies, 561, 562, 564 and 567 and two donkeys, 3 and 5 were infected with EIAV(PV) and one horse (94-10) and one donkey (4) were infected with EIAV(WY). Although the horse and ponies all expe...
Genetic and biological variation in equine infectious anemia virus Rev correlates with variable stages of clinical disease in an experimentally infected pony. Genetic and biological variation in the regulatory protein Rev of equine infectious anemia virus (EIAV) were examined throughout a clinically dynamic disease course of an experimentally infected pony. Following infection with the virulent EIAV(Wyo), the pony underwent a variable disease course, including an acute fever episode at 12 days postinfection (DPI), multiple recurrent fever episodes until 135 DPI, a prolonged subclinical period, and two late fever episodes. Viral RNA was isolated from the inoculum and sequential sera samples, and the rev exon 2/gp45 overlapping ORFs were amplified, cl...
Equine infectious anaemia virus proteins with epitopes most frequently recognized by cytotoxic T lymphocytes from infected horses. Efficacious lentiviral vaccines designed to induce cytotoxic T lymphocytes (CTL) in outbred populations with a diverse repertoire of MHC class I molecules should contain or express multiple viral proteins. To determine the equine infectious anaemia virus (EIAV) proteins with epitopes most frequently recognized by CTL from seven horses infected for 0.5 to 7 years, retroviral vector-transduced target cells expressing viral proteins were used in CTL assays. Gag p15 was recognized by CTL from 100% of these infected horses. p26 was recognized by CTL from 86%, SU and the middle third of Pol protein ...
Mutations occurring during serial passage of Japanese equine infectious anemia virus in primary horse macrophages. An attenuated equine infectious anemia virus (EIAV), named V26, was previously obtained after 50 passages of the Japanese virulent strain V70 in primary macrophage culture. To clarify the differences between both viruses, their full-length sequences were determined. There were higher mutations in S2 (6.15% amino acid difference) and LTR (10.7% nucleotide difference). The presumed initiation codon of the S2 gene was absent from the sequence of V26. There was a large insertion within the long-terminal repeat (LTR) U3 hypervariable region of V26. In addition, there were minor mutations in gag (1....
Immune responses and viral replication in long-term inapparent carrier ponies inoculated with equine infectious anemia virus. Persistent infection of equids by equine infectious anemia virus (EIAV) is typically characterized by a progression during the first year postinfection from chronic disease with recurring disease cycles to a long-term asymptomatic infection that is maintained indefinitely. The goal of the current study was to perform a comprehensive longitudinal analysis of the course of virus infection and development of host immunity in experimentally infected horses as they progressed from chronic disease to long-term inapparent carriage. We previously described the evolution of EIAV genomic quasispecies (C...
Development of a fluorescence polarization-based diagnostic assay for equine infectious anemia virus. The control of equine infectious anemia virus (EIAV) infections of horses has been over the past 20 years based primarily on the identification and elimination of seropositive horses, predominantly by a standardized agar gel immunodiffusion (AGID) assay in centralized reference laboratories. This screening for EIAV-seropositive horses has been to date hindered by the lack of a rapid diagnostic format that can be easily employed in the field. We describe here the development of a rapid solution-phase assay for the presence of serum antibodies to EIAV based on fluorescence polarization (FP) (pat...
Binding of equine infectious anemia virus rev to an exon splicing enhancer mediates alternative splicing and nuclear export of viral mRNAs. In addition to facilitating the nuclear export of incompletely spliced viral mRNAs, equine infectious anemia virus (EIAV) Rev regulates alternative splicing of the third exon of the tat/rev mRNA. In the presence of Rev, this exon of the bicistronic RNA is skipped in a fraction of the spliced mRNAs. In this report, the cis-acting requirements for exon 3 usage were correlated with sequences necessary for Rev binding and transport of incompletely spliced RNA. The presence of a purine-rich exon splicing enhancer (ESE) was required for exon 3 recognition, and the addition of Rev inhibited exon 3 sp...
Binding of equine infectious anemia virus matrix protein to membrane bilayers involves multiple interactions. Human immunodeficiency virus (HIV) and equine infectious anemia virus (EIAV) are closely related lentiviruses that infect immune cells, but their pathogenesis differ. Localization to the cytosolic leaflet of the plasma membrane is critical for replication of both viruses. This localization is accomplished through the matrix (MA) domain of the Gag precursor protein. In HIV-1, association of MA to anionic membranes appears to be primarily driven by a linear cluster of basic residues in the MA domain and an N-myristoylation signal. Interestingly, the MA protein of EIAV does not contain either of ...
Tissue sites of persistent infection and active replication of equine infectious anemia virus during acute disease and asymptomatic infection in experimentally infected equids. 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 ...
Interactions between equine cyclin T1, Tat, and TAR are disrupted by a leucine-to-valine substitution found in human cyclin T1. Transcriptional transactivators (Tat) from human immunodeficiency and equine infectious anemia viruses (HIV and EIAV) interact with their transactivation response elements (TAR) to increase the rates of viral transcription. Whereas the human cyclin T1 is required for the binding of Tat to TAR from HIV, it is unknown how Tat from EIAV interacts with its TAR. Furthermore, Tat from EIAV functions in equine and canine cells but not in human cells. In this study, we present sequences of cyclins T1 from horse and dog and demonstrate that their N-terminal 300 residues rescue the transactivation of Ta...
Replication ability in vitro and in vivo of equine infectious anemia virus avirulent Japanese strain. An attenuated equine infectious anemia virus (EIAV), V26, was previously prepared by 50 passages of the Japanese virulent strain V70 in primary horse macrophage culture. The horses inoculated with this V26 virus were shown to raise neutralizing antibodies against V70 without any viremia. Here, we investigated the in vitro and in vivo replication ability of V26. Comparison of the long-terminal repeat (LTR) sequences between V26 and V70 revealed a large insertion within the LTR U3 hypervariable region of V26. V26 with the mutation in the LTR showed much higher promoter activity in vitro than V70...
The S2 gene of equine infectious anemia virus is a highly conserved determinant of viral replication and virulence properties in experimentally infected ponies. Equine infectious anemia virus (EIAV) is genetically one of the simplest lentiviruses in that the viral genome encodes only three accessory genes, tat, rev, and S2. Although serological analyses demonstrate the expression of the S2 protein in persistently infected horses, the role of this viral gene remains undefined. We recently reported that the S2 gene is not essential for EIAV replication in primary equine macrophages, as EIAV mutants lacking the S2 gene replicate to levels similar to those of the parental virus (F. Li, B. A. Puffer, and R. C. Montelaro, J. Virol. 72:8344-8348, 1998). We n...