27 results on '"Valas S"'
Search Results
2. Serosurvey of Schmallenberg Virus Infection in the Highest Goat-Specialized Region of France
- Author
-
Valas, S., Baudry, C., Ehrhardt, N., LeVen, A., Thirion, M., Aubert, C., and Vialard, J.
- Published
- 2015
- Full Text
- View/download PDF
3. Advanced RF front end technology
- Author
-
Herman, M, Valas, S, and Katehi, L
- Published
- 2001
4. Advanced RF front end technology
- Author
-
Katehi, L, Valas, S, and Herman, M
- Abstract
The ability to achieve low-mass low-cost micro/nano-spacecraft for deep space exploration requires extensive miniaturization of all subsystems.
- Published
- 2001
5. Advanced RF Front End Technology
- Author
-
Herman, M. I, Valas, S, and Katehi, L. P. B
- Subjects
Lunar And Planetary Science And Exploration - Abstract
The ability to achieve low-mass low-cost micro/nanospacecraft for Deep Space exploration requires extensive miniaturization of all subsystems. The front end of the Telecommunication subsystem is an area in which major mass (factor of 10) and volume (factor of 100) reduction can be achieved via the development of new silicon based micromachined technology and devices. Major components that make up the front end include single-pole and double-throw switches, diplexer, and solid state power amplifier. JPL's Center For Space Microsystems - System On A Chip (SOAC) Program has addressed the challenges of front end miniaturization (switches and diplexers). Our objectives were to develop the main components that comprise a communication front end and enable integration in a single module that we refer to as a 'cube'. In this paper we will provide the latest status of our Microelectromechanical System (MEMS) switches and surface micromachined filter development. Based on the significant progress achieved we can begin to provide guidelines of the proper system insertion for these emerging technologies. Additional information is contained in the original extended abstract.
- Published
- 2001
6. DS1 Ka-band Solid State Power Amplifier
- Author
-
Herman, M, Amaro, L, Chen, C, Gaughen, G, Hatch, W, Howard, J, Makovsky, A, Perderson, K, Petree, S, Scaramastra, R, Taylor, F, Vacchione, J, and Valas, S
- Published
- 2000
7. Ka-band Solid State Power Amplifier (KAPA)
- Author
-
Herman, N, Amaro, L, Chen, C-C, Gaughen, G, Hatch, W, Howard, J, Makovsky, A, Pederson, K, Petree, S, Scaramastra, R, Taylor, F, Vacchione, J, and Valas, S
- Published
- 2000
8. Caprine arthritis-encephalitis virus in semen of naturally infected bucks
- Author
-
Travassos, C.E, Benoı̂t, C, Valas, S, da Silva, A.G, and Perrin, G
- Published
- 1999
- Full Text
- View/download PDF
9. Investigation of passive bandpass filters using MMIC technology.
- Author
-
Herman, M.I., Valas, S., McNay, D.M., Knust-Graichen, R., and Chen, J.C.
- Published
- 1992
- Full Text
- View/download PDF
10. Characterization of a new 5' splice site within the caprine arthritis encephalitis virus genome: evidence for a novel auxiliary protein
- Author
-
Perrin Cécile, Rolland Morgane, Valas Stephen, Perrin Gérard, and Mamoun Robert Z
- Subjects
Immunologic diseases. Allergy ,RC581-607 - Abstract
Abstract Background Lentiviral genomes encode multiple structural and regulatory proteins. Expression of the full complement of viral proteins is accomplished in part by alternative splicing of the genomic RNA. Caprine arthritis encephalitis virus (CAEV) and maedi-visna virus (MVV) are two highly related small-ruminant lentiviruses (SRLVs) that infect goats and sheep. Their genome seems to be less complex than those of primate lentiviruses since SRLVs encode only three auxiliary proteins, namely, Tat, Rev, and Vif, in addition to the products of gag, pol, and env genes common to all retroviruses. Here, we investigated the central part of the SRLV genome to identify new splice elements and their relevance in viral mRNA and protein expression. Results We demonstrated the existence of a new 5' splice (SD) site located within the central part of CAEV genome, 17 nucleotides downstream from the SD site used for the rev mRNA synthesis, and perfectly conserved among SRLV strains. This new SD site was found to be functional in both transfected and infected cells, leading to the production of a transcript containing an open reading frame generated by the splice junction with the 3' splice site used for the rev mRNA synthesis. This open reading frame encodes two major protein isoforms of 18- and 17-kDa, named Rtm, in which the N-terminal domain shared by the Env precursor and Rev proteins is fused to the entire cytoplasmic tail of the transmembrane glycoprotein. Immunoprecipitations using monospecific antibodies provided evidence for the expression of the Rtm isoforms in infected cells. The Rtm protein interacts specifically with the cytoplasmic domain of the transmembrane glycoprotein in vitro, and its expression impairs the fusion activity of the Env protein. Conclusion The characterization of a novel CAEV protein, named Rtm, which is produced by an additional multiply-spliced mRNA, indicated that the splicing pattern of CAEV genome is more complex than previously reported, generating greater protein diversity. The high conservation of the SD site used for the rtm mRNA synthesis among CAEV and MVV strains strongly suggests that the Rtm protein plays a role in SRLV propagation in vivo, likely by competing with Env protein functions.
- Published
- 2008
- Full Text
- View/download PDF
11. Isolation in three-dimensional integrated circuits.
- Author
-
Margomenos, A., Valas, S., Herman, M.I., and Katehi, L.P.B.
- Published
- 2000
- Full Text
- View/download PDF
12. North American and French Caprine Arthritis-Encephalitis Viruses Emerge from Ovine Maedi-Visna Viruses
- Author
-
Valas, S., Benoit, C., Guionaud, C., Perrin, G., and Mamoun, R.Z.
- Published
- 1997
- Full Text
- View/download PDF
13. Genetic and antigenic characterization of Brazilian SRLV strains: Natural small ruminant interspecies transmission from mixed herds.
- Author
-
Braz, G.F., Heinemann, M.B., Reis, J.K.P., Teixeira, B.M., Cruz, J.C.M., Rajão, D.S., Oliveira, F.G., Alves, F., Castro, R.S., Leite, R.C., and Valas, S.
- Subjects
- *
ANIMAL herds , *MIXED infections , *GOATS , *SPECIES diversity , *RUMINANTS , *SHEEP , *HERDING - Abstract
Cross-species transmission events and mixed infection of small ruminant lentiviruses (SRLVs) were studied in seven goats and two sheep from three small ruminant mixed flocks from Northeast and Southeast Brazil. Genetic and antigenic analyses with gag/env genes and ELISA multiepitope SU1/SU5 recombinant antigens were carried out, respectively. The genetic analysis of gag and env sequences showed high viral diversity in both species, MVV-like (subtype A1) and CAEV-like B1 in goats, and CAEV-like (subtype B1) in sheep, revealing SRLV interspecies transmission from sheep to goats and vice versa in Brazilian farms. Two Brazilian caprine lentiviruses were segregated in two new genetic clades based on gag analyses, which suggests a new classification into heterogenic genotype A. Furthermore, goat isolates were grouped into subtype A1 and B1 clusters. Cross-reactive antibodies were detected in goats using ELISA with a recombinant antigen carrying SU1 and SU5 immunodominant epitopes; the results showed anti-CAEV and MVV antibodies in goats and anti-CAEV antibodies in sheep. This result can be associated with the high divergence in the V4 region due to SRLV variability. All results confirm cross-species infection of SRLV in Brazilian mixed herds. • Goat from mixed farm was dually infected with arthritis-encephalitis virus (CAEV) and visna-maedi virus (MVV) –like. • Brazilian SRLV goat sequences were identified as visna-maedi virus-like, divergent subtype in A groupe. • Brazilian SRLV sheep sequences were related to CAEV viruses, subtype B1. • Cross-species infection of SRLV in Brazilian mixed herds. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
14. Inter-laboratory comparison of eleven quantitative or digital PCR assays for detection of proviral bovine leukemia virus in blood samples.
- Author
-
Pluta A, Jaworski JP, Droscha C, VanderWeele S, Taxis TM, Valas S, Brnić D, Jungić A, Ruano MJ, Sánchez A, Murakami K, Nakamura K, Puentes R, De Brun M, Ruiz V, Gómez MEL, Lendez P, Dolcini G, Camargos MF, Fonseca A, Barua S, Wang C, Giza A, and Kuźmak J
- Subjects
- Animals, Cattle, Polymerase Chain Reaction veterinary, Polymerase Chain Reaction methods, Sensitivity and Specificity, Real-Time Polymerase Chain Reaction veterinary, Real-Time Polymerase Chain Reaction methods, DNA, Viral blood, Leukemia Virus, Bovine isolation & purification, Leukemia Virus, Bovine genetics, Enzootic Bovine Leukosis diagnosis, Enzootic Bovine Leukosis virology, Enzootic Bovine Leukosis blood, Proviruses genetics, Proviruses isolation & purification
- Abstract
Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis and causes a persistent infection that can leave cattle with no symptoms. Many countries have been able to successfully eradicate BLV through improved detection and management methods. However, with the increasing novel molecular detection methods there have been few efforts to standardize these results at global scale. This study aimed to determine the interlaboratory accuracy and agreement of 11 molecular tests in detecting BLV. Each qPCR/ddPCR method varied by target gene, primer design, DNA input and chemistries. DNA samples were extracted from blood of BLV-seropositive cattle and lyophilized to grant a better preservation during shipping to all participants around the globe. Twenty nine out of 44 samples were correctly identified by the 11 labs and all methods exhibited a diagnostic sensitivity between 74 and 100%. Agreement amongst different assays was linked to BLV copy numbers present in samples and the characteristics of each assay (i.e., BLV target sequence). Finally, the mean correlation value for all assays was within the range of strong correlation. This study highlights the importance of continuous need for standardization and harmonization amongst assays and the different participants. The results underscore the need of an international calibrator to estimate the efficiency (standard curve) of the different assays and improve quantitation accuracy. Additionally, this will inform future participants about the variability associated with emerging chemistries, methods, and technologies used to study BLV. Altogether, by improving tests performance worldwide it will positively aid in the eradication efforts., (© 2024. The Author(s).)
- Published
- 2024
- Full Text
- View/download PDF
15. A retrospective evaluation of pooled serum ELISA testing in the frame of the French eradication program for infectious bovine rhinotracheitis.
- Author
-
Valas S, Ngwa-Mbot D, Stourm S, Mémeteau S, and Tabouret M
- Subjects
- Cattle, Animals, Retrospective Studies, Antibodies, Viral, Milk chemistry, Enzyme-Linked Immunosorbent Assay veterinary, Enzyme-Linked Immunosorbent Assay methods, Sensitivity and Specificity, Infectious Bovine Rhinotracheitis diagnosis, Infectious Bovine Rhinotracheitis epidemiology, Infectious Bovine Rhinotracheitis prevention & control, Herpesvirus 1, Bovine, Cattle Diseases diagnosis, Cattle Diseases epidemiology, Cattle Diseases prevention & control
- Abstract
Pooled serum testing using whole-virus indirect ELISA has been recently recognized as an official method for surveillance of bovine herpesvirus 1 (BoHV1) in cattle herds in Europe. In this study, a retrospective analysis of data from the French BoHV1 surveillance campaign 2018-2019, including 7434 BoHV1-free certified herds and 157 infected herds, was performed in order to evaluate the diagnostic specificity and sensitivity of two pooled serum indirect ELISAs (from IDEXX and IDVet), in comparison with individual testing by blocking ELISAs targeting the gB and gE proteins. Pooled serum testing showed a relative specificity higher than 97.5% and a detection rate of 100% since all gB+/gE+ samples were found in positive pools. At the herd level, no more than one false positive pool was observed in most of BoHV1-free certified herds, leading to a herd relative specificity of 85.1% and 86.0% for the IDEXX and IDVet pooled serum ELISAs, respectively. Among infected herds tested by pool sizes up to 10 sera (n = 122), 46% of herds were detected through pools of size 10 containing a single positive sample, 23% through pools of size 10 containing at least two positive samples, and 31% through pools of smaller sizes. A complementary study based on manually constituted pools revealed that at least one positive sample in 100% and 93.4% of herds could be detected individually by pools of size 10 with the IDEXX and IDVet ELISAs, respectively. However, pooled serum ELISAs were influenced by the level of individual reactivity, since pools composed of either one weak-positive sample or one gB+/gE- sample could yield negative results. Altogether, these results provided the first evidence that pooled serum testing (pool size up to 10) is a suitable strategy for surveillance of BoHV1-free cattle farms., Competing Interests: Conflict of interest statement All authors deny any financial and personal relationships with other people or organizations that could inappropriately influence this work., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)
- Published
- 2023
- Full Text
- View/download PDF
16. Improvement of eradication program for infectious bovine rhinotracheitis in France inferred by serological monitoring of singleton reactors in certified BoHV1-free herds.
- Author
-
Valas S, Brémaud I, Stourm S, Croisé B, Mémeteau S, Ngwa-Mbot D, and Tabouret M
- Subjects
- Animals, Cattle, Enzyme-Linked Immunosorbent Assay veterinary, France epidemiology, Infectious Bovine Rhinotracheitis prevention & control, Public Health Surveillance methods, ROC Curve, Sensitivity and Specificity, Antibodies, Viral blood, Herpesvirus 1, Bovine isolation & purification, Infectious Bovine Rhinotracheitis blood, Infectious Bovine Rhinotracheitis epidemiology
- Abstract
Within the framework of the national voluntary eradication program for Bovine alphaherpesvirus 1 (BoHV1) in France, the proportion of certified-free herds which experienced no more than two positive animals (termed singleton reactors) steadily increased to reach up to 95% in 2015. The aim of this study was to collate and evaluate serological data to gain insight into these epidemiological questionable BoHV1 seropositive animals. Preliminary evaluation of the performances of BoHV1 ELISA kits using a collection of 997 field sera with well-defined status revealed a relatively low specificity of the two gB blocking ELISAs most used in France for confirmatory testing (93.2% and 97.5% for gB-IDVet and gB-Idexx, respectively). In both ELISAs, the suboptimal specificity was associated with the presence of antibodies against BoHV2. Reassessment of the cut-offs led to a specificity and a sensitivity higher than 99.3%. Consequently, a comprehensive analysis of gB-positive sera from 2551 singleton reactors was performed by using gB ELISAs with optimized cut-offs, combined with viral neutralization test (campaign 2014-2015) or gE ELISA (campaign 2015-2016). Fifty percent of the 728 sera collected in 2014-2015 reacted below the optimized cut-offs in both gB ELISAs. Analysis of new blood samples collected at a minimum 6-week interval showed that these weak-positive reactions did not increase with time and could not be confirmed by confirmatory tests. Among the 1823 sera collected in 2015-2016, only 84 samples tested positive by gE ELISA, most of them corresponding to sera with reactivity above the optimized cut-offs in gB ELISAs. Screening for BoHV2 antibodies revealed a significantly increased prevalence among herds with singleton reactors, compared with the between-herd prevalence in French cattle herds. Altogether, these results provided suitable analytical strategies to limit the occurrence of false-positive BoHV1 reactions and inappropriate withdrawal of the BoHV1-free status, without alteration of diagnostic costs and reliability of eradication programs., (Copyright © 2019 Elsevier B.V. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
17. Epidemiological survey in single-species flocks from Poland reveals expanded genetic and antigenic diversity of small ruminant lentiviruses.
- Author
-
Olech M, Valas S, and Kuźmak J
- Subjects
- Animals, Epidemiologic Studies, Gene Products, gag genetics, Goat Diseases virology, Goats virology, Phylogeny, Poland, Sequence Analysis, DNA methods, Sheep virology, Sheep Diseases virology, Surveys and Questionnaires, Viral Envelope Proteins genetics, Antigenic Variation genetics, Genetic Variation genetics, Lentivirus genetics, Lentivirus Infections virology, Ruminants virology
- Abstract
Small ruminant lentivirus (SRLV) infections are widespread in Poland and circulation of subtypes A1, A12, A13, B1 and B2 was detected. The present work aimed at extending previous study based on the analysis of a larger number of animals from single-species flocks. Animals were selected for genetic analysis based on serological reactivity towards a range of recombinant antigens derived from Gag and Env viral proteins. Phylogenetic analysis revealed the existence of subtypes B2 and A12 in both goats and sheep and subtypes A1 and B1 in goats only. In addition, two novel subtypes, A16 and A17, were found in goats. Co-infections with strains belonging to different subtypes within A and B groups were detected in 1 sheep and 4 goats originating from four flocks. Although the reactivity of serum samples towards the recombinant antigens confirmed immunological relatedness between Gag epitopes of different subtypes and the cross-reactive nature of Gag antibodies, eleven serum samples failed to react with antigens representing all subtypes detected up-to-date in Poland, highlighting the limitations of the serological diagnosis. These data showed the complex nature of SRLV subtypes circulating in sheep and goats in Poland and the need for improving SRLV-related diagnostic capacity.
- Published
- 2018
- Full Text
- View/download PDF
18. Schmallenberg virus-two years of experiences.
- Author
-
Wernike K, Conraths F, Zanella G, Granzow H, Gache K, Schirrmeier H, Valas S, Staubach C, Marianneau P, Kraatz F, Höreth-Böntgen D, Reimann I, Zientara S, and Beer M
- Subjects
- Animal Diseases diagnosis, Animal Diseases prevention & control, Animal Diseases transmission, Animals, Bunyaviridae Infections diagnosis, Bunyaviridae Infections epidemiology, Bunyaviridae Infections prevention & control, Bunyaviridae Infections transmission, Ceratopogonidae virology, Congenital Abnormalities veterinary, Congenital Abnormalities virology, Europe epidemiology, Insect Vectors virology, Real-Time Polymerase Chain Reaction, Ruminants virology, Seroepidemiologic Studies, Animal Diseases epidemiology, Animal Diseases virology, Bunyaviridae Infections veterinary, Orthobunyavirus genetics, Orthobunyavirus pathogenicity
- Abstract
In autumn 2011, a novel species of the genus Orthobunyavirus of the Simbu serogroup was discovered close to the German/Dutch border and named Schmallenberg virus (SBV). Since then, SBV has caused a large epidemic in European livestock. Like other viruses of the Simbu serogroup, SBV is transmitted by insect vectors. Adult ruminants may show a mild transient disease, while an infection during a critical period of pregnancy can lead to severe congenital malformation, premature birth or stillbirth. The current knowledge about the virus, its diagnosis, the spread of the epidemic, the impact and the possibilities for preventing infections with SBV is described and discussed., (Copyright © 2014 Elsevier B.V. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
19. Diverse host-virus interactions following caprine arthritis-encephalitis virus infection in sheep and goats.
- Author
-
Rachid A, Croisé B, Russo P, Vignoni M, Lacerenza D, Rosati S, Kuźmak J, and Valas S
- Subjects
- Amino Acid Sequence, Animals, Antibodies, Viral, B-Lymphocytes physiology, Enzyme-Linked Immunosorbent Assay veterinary, Gene Expression Regulation, Viral physiology, Goat Diseases blood, Goats, Immunity, Humoral, Immunodominant Epitopes, Lentivirus Infections virology, Molecular Sequence Data, Sheep, Sheep Diseases blood, Species Specificity, Time Factors, Viral Load, Viral Structural Proteins genetics, Viral Structural Proteins immunology, Viral Structural Proteins metabolism, Arthritis-Encephalitis Virus, Caprine physiology, Goat Diseases virology, Lentivirus Infections veterinary, Sheep Diseases virology
- Abstract
Interspecies transmissions substantially contribute to the epidemiology of small ruminant lentiviruses (SRLVs), including caprine arthritis encephalitis virus (CAEV) and visna-maëdi virus. However, comprehensive studies of host-virus interactions during SRLV adaptation to the new host are lacking. In this study, virological and serological features were analysed over a 6 month period in five sheep and three goats experimentally infected with a CAEV strain. Provirus load at the early stage of infection was significantly higher in sheep than in goats. A broad antibody reactivity against the matrix and capsid proteins was detected in goats, whereas the response to these antigens was mostly type-specific in sheep. The humoral response to the major immunodominant domain of the surface unit glycoprotein was type-specific, regardless of the host species. These species-specific immune responses were then confirmed in naturally infected sheep and goats using sera from mixed flocks in which interspecies transmissions were reported. Taken together, these results provide evidence that SRLV infections evolve in a host-dependent manner, with distinct host-virus interactions in sheep and goats, and highlight the need to consider both SRLV genotypes in diagnosis, particularly in sheep.
- Published
- 2013
- Full Text
- View/download PDF
20. Genetic and antigenic characterization of small ruminant lentiviruses circulating in Poland.
- Author
-
Olech M, Rachid A, Croisé B, Kuźmak J, and Valas S
- Subjects
- Animals, Arthritis-Encephalitis Virus, Caprine, Cluster Analysis, Enzyme-Linked Immunosorbent Assay, Gene Products, env genetics, Gene Products, gag genetics, Heteroduplex Analysis, Lentivirus genetics, Lentivirus immunology, Molecular Sequence Data, Phylogeny, Poland, Sequence Analysis, DNA, Antigenic Variation, Genetic Variation, Goats virology, Lentivirus classification, Lentivirus isolation & purification, Sheep virology
- Abstract
Small ruminant lentivirus (SRLV) infections are widespread in Poland, but the genetic features of sheep viruses are still lacking and limited to partial gag sequences for goat viruses. In this study, segments from the gag and env genes of Polish SRLV strains screened by heteroduplex mobility assay were subjected to genetic analyses. Subtype A1 was found in both sheep and goats, while subtypes B1 and B2 were found in goats and sheep, respectively. In addition, two novel subtypes (named A12 and A13) were found in sheep. Their close phylogenetic relatedness with SRLV strains previously isolated from Polish goats indicated that these new subtypes are predominant and circulate in both species. The antigenic relationships of subtypes A12 and A13 with other SRLV subtypes were tested in an ELISA assay based on recombinant antigens carrying the immunodominant domains of structural proteins (MA, CA and SU). Antigenic cross-reactivity in the Gag epitopes was evident among genotype A subtypes and, to a lower extent, between genotypes A and B. In contrast, a subtype-specific immunoresponse was detected in the SU epitopes. These results emphasize the broad genetic and antigenic diversity of SRLV strains circulating in Europe and confirmed the need to consider all viral genotypes to choose the antigens in serological tests in order to avoid misdiagnosis in control and eradication programs., (Copyright © 2011 Elsevier B.V. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
21. Interference of vaccination against bluetongue virus serotypes 1 and 8 with serological diagnosis of small-ruminant lentivirus infection.
- Author
-
Valas S, Le Ven A, Croise B, Maquigneau M, and Perrin C
- Subjects
- Animals, False Positive Reactions, Goats, Lentivirus Infections diagnosis, Reproducibility of Results, Time Factors, Bluetongue virus immunology, Enzyme-Linked Immunosorbent Assay methods, Goat Diseases diagnosis, Goat Diseases virology, Lentivirus isolation & purification, Lentivirus Infections veterinary, Viral Vaccines immunology
- Abstract
The effects of the recent vaccinations against bluetongue virus serotype 1 (BTV-1) and BTV-8 in Europe on the reliability of enzyme-linked immunosorbent assays (ELISAs) currently used for diagnosis of small-ruminant lentivirus (SRLV) infection were examined. Primary vaccination against BTV-8 in goats induced an increase in reactivity that did not exceed 3 months in a whole-virus indirect ELISA and a competitive ELISA based on the gp135 glycoprotein. Subsequent BTV-1/8 vaccination extended the time scale of false-positive reactivity for up to 6 months. These results are of relevance for SRLV-monitoring programs.
- Published
- 2011
- Full Text
- View/download PDF
22. Field evaluation of a gag/env heteroduplex mobility assay for genetic subtyping of small-ruminant lentiviruses.
- Author
-
Germain K, Croise B, and Valas S
- Subjects
- Amino Acid Sequence, Animals, Genetic Variation, Goats, Lentivirus genetics, Lentivirus Infections virology, Molecular Sequence Data, Nucleocapsid chemistry, Nucleocapsid genetics, Phylogeny, Recombination, Genetic, Sequence Analysis, DNA, Sheep, Gene Products, env chemistry, Gene Products, env genetics, Gene Products, gag chemistry, Gene Products, gag genetics, Goat Diseases virology, Heteroduplex Analysis methods, Lentivirus classification, Lentivirus Infections veterinary, Sheep Diseases virology
- Abstract
Small-ruminant lentiviruses (SRLVs) display a high genetic diversity and are currently classified into five genotypes and an increasing number of subtypes. The co-circulation of subtypes in restricted geographical regions, combined with the occurrence of cross-species infection, suggests the need for development of a large-scale screening methodology for rapid monitoring of the prevalence of the various genetic subtypes and their genetic evolution. Here, a heteroduplex mobility assay (HMA) was developed for the rapid identification of group B subtypes. The assay was validated for both the p14 nucleocapsid-coding region of the gag gene and the V1-V2 region of the env gene using a panel of reference standards and was applied to the genetic subtyping of SRLV field isolates from five mixed flocks in France. Subtyping of 75 blood samples using the env HMA revealed a preferential distribution of subtypes B1 and B2 in sheep and goats, despite direct evidence for interspecies transmission of both subtypes. Adding the gag HMA to the env HMA provided evidence for dual infection and putative recombination between subtypes B1 and B2 in five goats, and between groups A and B in one sheep. Phylogenetic analysis revealed that 100 % (23/23) and 96.7 % (30/31) of samples were correctly classified using the gag and env HMAs, respectively. These results indicate that dual infection and recombination may be a significant source of new variation in SRLV and provide a useful tool for the rapid genetic subtyping of SRLV isolates, which could be relevant for the development of more accurate diagnosis of prevalent SRLV strains in different countries.
- Published
- 2008
- Full Text
- View/download PDF
23. Characterization of a new 5' splice site within the caprine arthritis encephalitis virus genome: evidence for a novel auxiliary protein.
- Author
-
Valas S, Rolland M, Perrin C, Perrin G, and Mamoun RZ
- Subjects
- Amino Acid Sequence, Animals, Arthritis-Encephalitis Virus, Caprine genetics, Base Sequence, Cells, Cultured, Cloning, Molecular, Goats, Humans, Membrane Glycoproteins metabolism, Molecular Sequence Data, Molecular Weight, Open Reading Frames genetics, Protein Isoforms chemistry, Protein Isoforms genetics, Protein Isoforms metabolism, RNA Splice Sites genetics, Viral Envelope Proteins physiology, Viral Proteins chemistry, Viral Proteins metabolism, Arthritis-Encephalitis Virus, Caprine physiology, Genome, Viral, Viral Proteins genetics
- Abstract
Background: Lentiviral genomes encode multiple structural and regulatory proteins. Expression of the full complement of viral proteins is accomplished in part by alternative splicing of the genomic RNA. Caprine arthritis encephalitis virus (CAEV) and maedi-visna virus (MVV) are two highly related small-ruminant lentiviruses (SRLVs) that infect goats and sheep. Their genome seems to be less complex than those of primate lentiviruses since SRLVs encode only three auxiliary proteins, namely, Tat, Rev, and Vif, in addition to the products of gag, pol, and env genes common to all retroviruses. Here, we investigated the central part of the SRLV genome to identify new splice elements and their relevance in viral mRNA and protein expression., Results: We demonstrated the existence of a new 5' splice (SD) site located within the central part of CAEV genome, 17 nucleotides downstream from the SD site used for the rev mRNA synthesis, and perfectly conserved among SRLV strains. This new SD site was found to be functional in both transfected and infected cells, leading to the production of a transcript containing an open reading frame generated by the splice junction with the 3' splice site used for the rev mRNA synthesis. This open reading frame encodes two major protein isoforms of 18- and 17-kDa, named Rtm, in which the N-terminal domain shared by the Env precursor and Rev proteins is fused to the entire cytoplasmic tail of the transmembrane glycoprotein. Immunoprecipitations using monospecific antibodies provided evidence for the expression of the Rtm isoforms in infected cells. The Rtm protein interacts specifically with the cytoplasmic domain of the transmembrane glycoprotein in vitro, and its expression impairs the fusion activity of the Env protein., Conclusion: The characterization of a novel CAEV protein, named Rtm, which is produced by an additional multiply-spliced mRNA, indicated that the splicing pattern of CAEV genome is more complex than previously reported, generating greater protein diversity. The high conservation of the SD site used for the rtm mRNA synthesis among CAEV and MVV strains strongly suggests that the Rtm protein plays a role in SRLV propagation in vivo, likely by competing with Env protein functions.
- Published
- 2008
- Full Text
- View/download PDF
24. Distribution and heterogeneity of small ruminant lentivirus envelope subtypes in naturally infected French sheep.
- Author
-
Germain K and Valas S
- Subjects
- Animals, France epidemiology, Genetic Variation, Heteroduplex Analysis, Lentivirus classification, Lentivirus Infections epidemiology, Molecular Sequence Data, Phylogeny, Sheep, Species Specificity, Glycoproteins genetics, Lentivirus genetics, Lentivirus Infections veterinary, Sheep Diseases epidemiology, Viral Envelope Proteins genetics
- Abstract
Small ruminants lentiviruses (SRLV) nucleotide sequences spanning the V1V2 variable regions of the env gene were amplified by nested-PCR from 38 blood samples collected from 16 naturally infected sheep flocks in France. For the rapid SRLV group determination of field isolates, the PCR-amplified fragments were subjected to a SRLV-adapted heteroduplex mobility assay (HMA). All viral sequences were clearly assignable to the SRLV group B by HMA analysis. Twenty-seven SRLV isolates were selected for DNA sequence analysis. In each case, nucleotide comparison and phylogenetic analyses confirmed the genetic relationships inferred by HMA. Six SRLV isolates belonged to subtype B1, and 21 pertained to subtype B2, one flock being infected with both subtypes. Subtypes B1 and B2 were found with different frequencies and geographic spread, but exhibited similar genetic diversities. These results give a more complete picture of the distribution and heterogeneity of SRLV env subtypes in sheep and confirmed that multiple interspecies transmission occurred in the past. Furthermore, HMA appeared to be a rapid and reliable method to differentiate caprine arthritis encephalitis virus from maedi-visna virus.
- Published
- 2006
- Full Text
- View/download PDF
25. Establishment and characterization of a goat synovial membrane cell line susceptible to small ruminant lentivirus infection.
- Author
-
Rolland M, Chauvineau C, Valas S, Mamoun RZ, and Perrin G
- Subjects
- Animals, Cell Division, Cell Line, Humans, T-Lymphocytes physiology, Telomerase genetics, Transfection, Virology methods, Arthritis-Encephalitis Virus, Caprine physiology, Goats, Synovial Membrane virology, Visna-maedi virus physiology
- Abstract
Primary goat synovial membrane (GSM) cells are widely used to study small ruminant lentiviruses (SRLV), i.e. maedi visna virus (MVV) and caprine arthritis-encephalitis virus (CAEV), but their limited life-span of 15-20 passages in vitro is problematic. Here, we report that ectopic expression of the catalytic subunit of human telomerase (hTERT) was sufficient to immortalize primary GSM cells. Cultures of hTERT-transfected GSM cells have been passaged for 2 years without showing any phenotypic difference from the original primary GSM cells. The hTERT-transfected cells continued to grow beyond a population doubling number of 250, while no net telomere lengthening was observed for these cells. Moreover, the immortalized GSM cells were susceptible to infection by both CAEV and MVV and were able to propagate theses viruses. Such cell line provides a useful source of standard and robust cells for both research and veterinary purposes.
- Published
- 2004
- Full Text
- View/download PDF
26. Characterisation of an Irish caprine lentivirus strain--SRLV phylogeny revisited.
- Author
-
Rolland M, Mooney J, Valas S, Perrin G, and Mamoun RZ
- Subjects
- Animals, Genes, env, Genes, gag, Genes, pol, Genetic Heterogeneity, Goats virology, Ireland, Lentiviruses, Ovine-Caprine genetics, Lentiviruses, Ovine-Caprine isolation & purification, Phylogeny, Lentiviruses, Ovine-Caprine classification
- Abstract
Small ruminant lentiviruses (SRLV), i.e. caprine arthritis-encephalitis virus (CAEV) (which infects goats) and maedi-visna virus (MVV) (which infects sheep) are two closely related lentiviruses but the relationship between goat and sheep lentiviruses has not been clearly established. To better understand their genetic relationship, we reinvestigated the phylogeny of SRLV using new sequences from an Irish and a Norwegian strain together with sequences available from databases. The phylogenetic analyses were carried out on the gag, pol and env fragments using four methods: neighbor-joining (NJ), Fitch and Margoliash (Fitch), Fitch and Wagner parsimony (Pars) and maximum likelihood (ML). The tree topologies were consistent whether derived from any of the four methods or any of the gene fragments, but the phylogenetic analyses in the pol and env regions were more informative than in the gag region. The Tamura-Nei model with variable rates across sites (described by a gamma distribution) provides a more accurate description of SRLV evolution than simple methods. The newly described Irish lentivirus strain, which was isolated from a goat, was closely related to the lentivirus that infects sheep: MVV. The novel Norwegian CAEV strain belonged to a cluster specific to the CAEV strains from Norway. Together, both data confirm the previously reported subdivision of the different SRLV strains into six clades. The caprine and ovine lentivirus sequences are interspersed in phylogenetic trees, supporting the existence of cross-species transmission. Nevertheless, the transmission of an ovine lentivirus to a goat could trigger the emergence of some goat-adapted phylums. Our new sequences confirm the complex situation in SRLV phylogeny but more sequences are needed to elucidate more precisely the relationship between SRLV.
- Published
- 2002
- Full Text
- View/download PDF
27. Variability and immunogenicity of caprine arthritis-encephalitis virus surface glycoprotein.
- Author
-
Valas S, Benoit C, Baudry C, Perrin G, and Mamoun RZ
- Subjects
- Amino Acid Sequence, Animals, Arthritis-Encephalitis Virus, Caprine classification, Arthritis-Encephalitis Virus, Caprine immunology, Arthritis-Encephalitis Virus, Caprine isolation & purification, Base Sequence, DNA, Viral, Epitope Mapping, Epitopes, B-Lymphocyte immunology, Goats, Membrane Glycoproteins immunology, Molecular Sequence Data, Sequence Homology, Amino Acid, Viral Envelope Proteins immunology, Arthritis-Encephalitis Virus, Caprine genetics, Epitopes, B-Lymphocyte genetics, Genetic Variation, Membrane Glycoproteins genetics, Viral Envelope Proteins genetics
- Abstract
The complete surface glycoprotein (SU) nucleotide sequences of three French isolates of caprine arthritis-encephalitis virus (CAEV) were determined and compared with those of previously described isolates: three American isolates and one French isolate. Phylogenetic analyses revealed the existence of four distinct and roughly equidistant evolutionary CAEV subtypes. Four conserved and five variable domains were identified in the SU. The fine specificities of antibodies produced against these domains during natural infection were examined using a pepscan analysis. Nine immunogenic segments were delineated throughout the conserved and variable domains of SU, two of them corresponding to conserved immunodominant epitopes. Antigenic determinants which may be involved in the immunopathogenic process induced by CAEV were identified. These results also provide sensitive and specific antigen peptides for the serological detection and differentiation of CAEV and visna/maedi virus infections.
- Published
- 2000
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.