Dynamics of perinatal bovine leukemia virus infection

BACKGROUND: Bovine leukemia virus (BLV) is highly endemic in many countries, including Argentina. As prevention of the spread from infected animals is of primary importance in breaking the cycle of BLV transmission, it is important to know the pathophysiology of BLV infection in young animals, as they are the main source of animal movement. In this work, we determined the proviral load and antibody titers of infected newborn calves from birth to first parturition (36 months). RESULTS: All calves under study were born to infected dams with high proviral load (PVL) in blood and high antibody titers and detectable provirus in the colostrum. The PVL for five out of seven calves was low at birth. All animals reached PVLs of more than 1% infected peripheral blood mononuclear cells (PBMCs), three at 3 months, one at 6 months, and one at 12 months. High PVLs persisted until the end of the study, and, in two animals, exceeded one BLV copy per cell. Two other calves maintained a high PVL from birth until the end of the study. Antibody titers were 32 or higher in the first sample from six out of seven calves. These decayed at 3–6 months to 16 or lower, and then increased again after this point. CONCLUSIONS: Calves infected during the first week of life could play an active role in early propagation of BLV to susceptible animals, since their PVL raised up during the first 12 months and persist as high for years. Early elimination could help to prevent transmission to young susceptible animals and to their own offspring. To our knowledge, this is the first study of the kinetics of BLV proviral load and antibody titers in newborn infected calves.Fil: Gutiérrez, Gerónimo. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alvarez, Irene. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Merlini, Ramiro. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Rondelli, Flavia. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias; ArgentinaFil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

The efficacy of ELISA commercial kits for the screening of equineinfectious anemia virus infection

El mejor indicador de la infección por el virus de la anemia infecciosa equina (Equine infectious anemia virus, EIAV) es la detección de anticuerpos específicos en el suero del caballo. En el presente trabajo se evaluó la capacidad de detección de anticuerpos contra EIAV de dos equipos de ELISA comerciales utilizando 302 muestras de suero equino, así como las ventajas potenciales de su uso como herramientas de screening. Ambos ensayos de ELISA presentaron 100 % de sensibilidad diagnóstica y una especificidad diagnóstica del orden de 92,3 a 94,3 %. Las muestras discordantes fueron analizadas por inmunoblot. Los resultados mostraron que las dos pruebas ELISA son muy eficientes para detectar animales infectados por EIAV, al permitir identificar un mayor número de animales positivos que la prueba de inmunodifusión en gel de agar, oficialmente aprobada en la República Argentina para la certificación de los animales. Las pruebas de ELISA constituyen herramientas muy útiles en los programas de control y de erradicación de la infección por EIAV.The most used and reliable indicator of equine infectious anemia virus (EIAV) infec-tion is the detection of its specific antibodies in horse serum. In the present study, theperformance of two commercial ELISA tests for the detection of EIAV antibodies as well asthe potential advantages of their use as an EIAV infection screening tool were evaluated in 302horse serum samples. Both ELISA assays showed 100% diagnostic sensitivity, and 92.3-94.3%diagnostic specificity. Discordant results were analyzed by immunoblot. The results showedthat both ELISA tests are very efficient at detecting EIAV infected animals, allowing to identifya higher number of positive horse cases. Thus, ELISA assays can be useful tools in EIA controland eradication.Fil: Alvarez, Irene. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias; ArgentinaFil: Cipolini Galarza, Fabiana. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias; ArgentinaFil: Wigdorovitz, Andrés. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Trono, Karina Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Barrandeguy, María Edith. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Universidad del Salvador. Escuela de Veterinaria; Argentin

Detection of Bovine Leukemia Virus RNA in Blood Samples of Naturally Infected Dairy Cattle

The viral expression in vivo, in bovine leukemia virus (BLV)-infected cattle, is considered to be restricted to extremely low levels, and the mitosis of infected B lymphocytes is regarded as the main mode of virus persistence within the infected host. In this study, the presence of BLV RNA in whole blood from seven asymptomatic cows naturally infected with BLV during one year, including a complete milking cycle and two delivery time points, was investigated by nested-PCR using the oligonucleotides complementary to the tax and pol gene. BLV RNA was detected in four cows at different time points, especially in high blood proviral load cows and around delivery time. This study describes the detection of free BLV RNA in blood from BLV-infected asymptomatic cows. The results obtained suggest the occurrence of persistent low-level expression of the tax and pol genes that could be a result of viral reactivation, within the asymptomatic period. This finding may be important in the pathogenesis of BLV infection, associated with the delivery period.Fil: Alvarez, Irene. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación En Ciencias Veterinarias y Gastronómicas. Instituto de Virología E Innovaciones Tecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Virología e Innovaciones Tecnológicas; ArgentinaFil: Porta, Natalia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación En Ciencias Veterinarias y Gastronómicas. Instituto de Virología E Innovaciones Tecnológicas. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Virología e Innovaciones Tecnológicas; Argentin

Evidence for the existence of pathogenicity determinants in the Long Terminal Repeats (LTRs) of the Bovine Leukemia Virus (BLV) genome

peer reviewedaudience: researcherEvidence for the existence of pathogenicity determinants in the Long Terminal Repeats (LTRs) of the Bovine Leukemia Virus (BLV) genome Sabrina M. Rodríguez1*, Karina Trono2, Leandro R. Jones3 1 Molecular and Cellular Epigenetics, Interdisciplinary Cluster for Applied Genoproteomics (GIGA) , University of Liège (ULg), Belgium. 2 Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria INTA-Castelar, CC 25 (1712), Castelar. 3 División de Biología Molecular, Estación de Fotobiología Playa Unión, CC 15, Rawson, Chubut 9103, Argentina. *E-mail: [email protected] The majority of BLV-infected animals are asymptomatic carriers (AL) while about 30% develop a benign persistent lymphocytosis (PL). Fatal lymphosarcoma (LS) occurs in 5% of infected animals. The genetic basis of these diverse outcomes of BLV infection is still unknown. Viral LTRs constitute a genetic determinant of pathogenesis for other retroviruses. However, this possibility has never been tested for BLV. Analyses to test correlation between clinical and genotypic traits across species must be corrected by including the group phylogeny. Otherwise, shared evolutionary history can jeopardize statistical independence. Thus, the influence of BLV LTR genetic variation on the clinical manifestation of the disease was investigated by employing Cladistic and Probabilistic, phylogenetic comparative methods. With this purpose, the 5´LTR region of 40 BLV proviruses from bovines with different clinical presentations (AL, PL, LS) was sequenced. Seven polymorphic positions showing an apparent association with the clinical presentation were identified. A provirus phylogeny was obtained using env gene sequences from 28 of the 40 provirus studied in this work. Both Cladistic and Probabilistic comparative analyses based on the empirical sequence alignment and the provirus phylogeny suggested that positions 41 and 56 might be correlated to the clinical presentation. The probabilistic analysis further indicated an association with the viral pathogenesis for positions 373, 450, 494 and 505, though the corresponding statistical supports were lower in comparison to the supports obtained for positions 41 and 56. These observations indicate that the BLV LTRs might contain pathogenicity determinants

Spontaneous virus reactivation in cattle chronically infected with bovine leukemia virus

Background: The absence of virus expression during the chronic stage of bovine leukemia virus (BLV) infection and its reactivation upon ex vivo culture has become a long-lived Dogma. During the chronic stage of BLV infection the immune response limits viral replication and the mitotic division of latently infected cells, carrying BLV provirus, allows viral expansion and disease progression towards a lymphoproliferative disorder. Several stressor factors have been associated with animal production and handling. As natural mediator of stress, glucocorticoids are strong immunosuppressive agents; moreover, they can bind long-terminal repeat region of retroviruses and induce viral expression. In the present study, we present a case report describing the spontaneous reactivation of BLV infection in naturally infected cattle. Case presentation: In order to investigate if virus reactivation occurred in vivo during the course of BLV infection, we followed up for 328 days one Holstein cow (> 3 years) chronically infected with BLV which presented high-proviral loads. This animal was neither lactating nor pregnant. Furthermore, we investigated if a stressor stimulus, in this case the administration of a synthetic glucocorticoid (dexamethasone), could impact the course of BLV infection in three additional cattle. For the first time, we observed a high level of BLV transcripts in a total of four cattle chronically infected with BLV. The detection of viral transcripts corresponding to pol gene strongly suggests virus reactivation in these animals. Interestingly, this simultaneous virus reactivation was unrelated to dexamethasone treatment. Conclusions: We reported for the first time spontaneous and high level of BLV transcriptional activation in cattle chronically infected with BLV. Although virus reactivation was unrelated to dexamethasone treatment, other stressor stimuli might have influenced this outcome. Future studies will be necessary to understand these observations, since the spontaneous virus reactivation presented here might have implications on BLV pathogenesis and transmission.Instituto de VirologíaFil: Jaworski, Juan Pablo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Tecnológicas; ArgentinaFil: Petersen, Marcos Iván. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Tecnológicas; ArgentinaFil: Carignano, Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Tecnológicas; ArgentinaFil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Tecnológicas; Argentin

Quantification of bovine leukemia virus proviral DNA using a low-cost real-time polymerase chain reaction

The detection of bovine leukemia virus (BLV) proviral DNA is an important tool to address whether an animal is infected with BLV. Compared with serological assays, real-time PCR accounts for greater sensitivity and can serve as a confirmatory test for the clarification of inconclusive or discordant serological test results. However, the high cost related to real-time PCR assays has limited their systematic inclusion in BLV surveillance and eradication programs. The aim of the present study was to validate a low-cost quantitative real-time PCR. Interestingly, by using SYBR Green detection dye, we were able to reduce the cost of a single reaction by a factor of 5 compared with most common assays based on the use of fluorogenic probes (i.e., TaqMan technology). This approach allowed a highly sensitive and specific detection and quantification of BLV proviral DNA from purified peripheral blood leukocytes and a milk matrix. Due to its simplicity and low cost, our in-house BLV SYBR quantitative real-time PCR might be used either as a screening or as a confirmatory test in BLV control programs.Fil: Petersen Cruceño, Marcos Iván. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alvarez, Irene. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jaworski, Juan Pablo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Bovine leukemia virus can be classified into seven genotypes: evidence for the existence of two novel clades.

Previous studies have classified the env sequences of bovine leukemia virus (BLV) provirus from different locations worldwide into between two and four genetic groupings. These different studies gave unique names to the identified groups and no study has yet integrated all the available sequences. Thus, we hypothesized that many of the different groups previously identified actually correspond to a limited group of genotypes that are unevenly distributed worldwide. To examine this hypothesis, we sequenced the env gene from 28 BLV field strains and compared these sequences to 46 env sequences that represent all the genetic groupings already identified. By using phylogenetic analyses, we recovered six clades, or genotypes, that we have called genotypes 1, 2, 3, 4, 5 and 6. Genotypes 1-5 have counterparts among the sequence groupings identified previously. One env sequence did not cluster with any of the others and was highly divergent when compared with the six genotypes identified here. Thus, an extra genotype, which we named 7, may exist. Similarity comparisons were highly congruent with phylogenetic analyses. Furthermore, our analyses confirmed the existence of geographical clusters

Bovine Leukemia Virus Infection in Neonatal Calves. Risk Factors and Control Measures

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (EBL). Although efficient eradication programs have been successfully implemented in most European countries and Oceania, BLV infection rates are still high worldwide. BLV naturally infects cattle, inducing a persistent infection with diverse clinical outcomes. The virus infects lymphocytes and integrates a DNA intermediate as a provirus into the genome of the cells. Therefore, exposure to biological fluids contaminated with infected lymphocytes potentially spreads the virus. Vertical transmission may occur in utero or during delivery, and about 10% of calves born to BLV-infected dams are already infected at birth. Most frequently, transmission from dams to their offspring occurs through the ingestion of infected colostrum or milk. Therefore, although EBL is not a disease specific to the neonatal period, during this period the calves are at special risk of becoming infected, especially in dairy farms, where they ingest colostrum and/or raw milk either naturally or artificially. Calves infected during the first week of life could play an active role in early propagation of BLV to susceptible animals. This review discusses the main factors that contribute to neonatal BLV infection in dairy herds, as well as different approaches and management practices that could be implemented to reduce the risk of BLV transmission during this period, aiming to decrease BLV infection in dairy herds

Diagnóstico serológico de Leucosis Enzoótica Bovina en rodeos de cría de la provincia de Tierra del Fuego

La leucosis enzoótica bovina es una enfermedad infecciosa de curso crónico, de tipo neoplásica, que afecta al ganado bovino adulto, causada por un retrovirus, virus de la leucosis bovina, del género Deltaretrovirus en la familia Retroviridae La transmisión de la enfermedad se produce por contagio vertical y horizontal directo o indirecto, siendo las prácticas de manejo uno de los factores de riesgo más importantes en la producción bovina. El curso de la enfermedad se caracteriza por presentar tres formas de desarrollo. Una fase inaparente inicial con producción de inmunidad humoral y un constante contenido de provirus en linfocitos. En un 30% de los animales infectados se produce linfocitosis persistente, que no tiene otra implicancia productiva más que la de sufrir un desorden inmunológico. En un 30% de estos animales y un porcentaje de los bovinos sin linfocitosis persistente, se presenta la enfermedad tumoral, con un cuadro de desmejoramiento generalizado que se traduce en disminución de la eficiencia productiva. Asimismo, las lesiones tumorales determinan trastornos funcionales de origen mecánico. Por otro lado, la leucosis enzoótica bovina produce un impacto en la comercialización internacional de ganado en pie, semen o embriones. En la República Argentina existe un Sistema de Certificación de Establecimientos Oficialmente Libres de Leucosis Enzoótica Bovina (Resolución-SAGPyA 128/01). En la provincia de Tierra del Fuego, no existen hasta el momento datos documentados de la presencia de la infección en los rodeos de cría. El objetivo del presente trabajo es comunicar la información generada hasta el momento en relación a la prevalencia de la enfermedad en Tierra del Fuego, durante los años 2011, 2012, 2013 y 2014, mediante diagnóstico serológico.EEA Santa CruzFil: Escribano, Cecilia Soledad. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Santa Cruz. Agencia de Extensión Río Grande; Argentina.Fil: Disalvo, Vilma. Laboratorio de Sanidad Animal “Raul Chiflett”. Río Grande, Tierra del Fuego; Argentina.Fil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina