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In enzootic bovine leukosis (EBL), a B-cell lymphoma caused by bovine leukemia virus (BLV) infection, immune remodeling within tumor-affected lymph nodes is currently poorly understood. Here, we analyzed chemokine production and macrophage phenotypes in tumor-affected lymph nodes in EBL, focusing on CCL4. Intracellular cytokine staining revealed that, compared with healthy lymph nodes, EBL tumor-affected lymph nodes showed increased proportions of CCL4 expressing cells, particularly among CD4 + T cells and B cells. Functional migration assays showed that recombinant CCL4 induced robust monocyte migration, with a comparatively modest T-cell migration. To identify lymph node macrophages, we characterized CD11b hi CD172a + cells and confirmed their macrophage identity based on high expression levels of CD11c, CD14, CD16, and CD68. Using this definition, we found that the CD11b hi CD172a + population was markedly increased in tumor-affected lymph nodes. Phenotypic analysis revealed an increased proportion of CD163 + and CD163 + PD-L1 + macrophages, consistent with the acquisition of an immunosuppressive phenotype. In parallel, macrophages in tumor-affected lymph nodes showed a shift from MHC class I/II hi to MHC I/II lo subsets and reduced co-expression of MHC molecules with CD80 and CD86, indicating impaired antigen-presenting features. Collectively, these findings suggest that elevated CCL4 production in tumor lesions induced by EBL is associated with monocyte recruitment and the accumulation of phenotypically altered macrophages, highlighting a chemokine-driven remodeling of the tumor immune microenvironment.

Coinfections can alter the adaptive immune responses to bovine tuberculosis (bTB) and hinder accurate diagnosis; however, their effect on host immunity to Mycobacterium bovis and disease progression is not well understood. In this study, we assessed the impact of natural coinfection with bovine leukemia virus (BLV) on immune responses to M. bovis . Among 108 cattle examined, those coinfected with BLV showed a significantly higher intragranulomatous mycobacterial burden and more severe pathological lesions compared to animals infected with M. bovis alone. Additionally, coinfected animals demonstrated a granulomatous response characterized by reduced lymphocyte populations, increased neutrophil infiltration, and diminished granuloma encapsulation, suggesting a compromised antimycobacterial immune response. Supporting this hypothesis, BLV-infected cattle exposed to mycobacterial antigens displayed impaired delayed-type hypersensitivity (type IV hypersensitivity) to a purified protein derivative of M. bovis as well as reduced antibody response. These findings indicate that BLV coinfection influences the immunopathogenesis of bTB, exacerbates disease progression in cattle naturally infected with M. bovis , and may reduce the predictive reliability of diagnostic methods used in bTB control programs.

In this study, we compared the effects of different bovine leukemia virus (BLV) strains and bovine lymphocyte antigen (BoLA)-DRB3 alleles in cattle with enzootic bovine leukosis (EBL) aged either <3 years or ≥3 years. The frequency of infection with BLV belonging to group A or B-1 in cattle aged <3 years with EBL was significantly higher than that in cattle aged ≥3 years, regardless of which BoLA-DRB3 allele was present. This suggests that infection with group A or B-1 BLV contributes more strongly to the development of EBL in young cattle than the presence of early-EBL-onset susceptibility BoLA-DRB3 alleles.

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis. It causes significant economic losses associated with losses due to slaughter and eradication of infected animal from infected area and other indirect economic losses such as restriction on importation of animals and semen from infected area. The main objective of this study was to determine the seroprevalence of BLV antibodies in cattle, buffaloes, and camels in Egypt using ELISA test. Serum samples were collected from 350 cattle, 100 buffaloes, and 100 camels during 2018. The seropositivity for BLV-specific antibody was 20.8%, 9%, and 0% in cattle, buffaloes, and camels, respectively. The result revealed significant association (p < 0.05) between age and seroprevalence of BLV infection in cattle > 4 years (24%) compared with those < 4 years (13%). We found no significant association between pregnancy and herd size and seroprevalence of BLV infection in this study (p > 0.05). Furthermore, the age, pregnancy state, and herd size had significant effect on seroprevalence of BLV infection in buffaloes. This study contributes that BLV is detected in cattle and buffaloes in Egypt and confirms that the camels has resistance against BLV infection. Hence, the control measures are very necessary to combat the transmission of the disease and reduce its economic impact.

Bovine leukemia virus (BLV) remains a major concern for cattle industries worldwide due to its persistent nature, economic impact, and challenges in control. In this study, we conducted a comprehensive nationwide survey of BLV in Kazakhstan between 2014 and 2024, utilizing serological diagnostics to assess prevalence and characterize viral genotypes (2024). A total of 433,537 serum samples were screened by agar gel immunodiffusion (AGID), revealing an overall seroprevalence of 5.87%, with the highest rates observed in the North Kazakhstan, Kostanay, and East Kazakhstan regions. In 2024, a targeted analysis of 3736 serum and 536 whole blood samples across 17 regions was performed using AGID, ELISA, real-time PCR, and nested PCR. ELISA demonstrated higher sensitivity than AGID (10.4% vs. 8.2%), confirmed by statistical correlation (r = 0.97, p < 0.001) and a Wilcoxon signed-rank test (p = 0.026). Real-time PCR detected BLV DNA in 4.7% of samples, with the highest positivity in the East Kazakhstan and Abai regions, confirming active viral circulation. Validation of a domestically developed AGID diagnostic kit showed full concordance with commercial assays (IDEXX, IDvet), supporting its use in national surveillance programs. These findings highlight the endemic status of BLV in Kazakhstan. Molecular analysis of sequenced isolates revealed the presence of genotype G-7, consistent with strains circulating in neighboring countries. Together, these results underscore the importance of integrated serological and molecular approaches for effective monitoring and control.

Abstract Background Bovine leukemia virus (BLV) infection in beef cattle has received less attention than in dairy herds, despite its potential impact on the beef industry. Objectives To compare six different supervised machine-learning (SML) algorithms used to identify the most important risk factors for predicting BLV seropositivity in beef cattle in Florida. Animals Retrospective study. We used a dataset of 1511 blood sample records from the Bronson Animal Disease Diagnostic Laboratory, Florida Department of Agriculture & Consumer Services, submitted for BLV antibody testing from 2012 to 2022. Methods Logistic regression (LR), decision tree (DT), gradient boosting (GB), random forest (RF), neural network (NN), and support vector machine (SVM) were used. Results Of the submitted samples, 11.6% were positive for BLV. The RF model best predicted BLV infection with an area under the receiver operating characteristic curve (AUROC) of 0.98, with a misclassification rate of 0.06. The DT model showed comparable performance to RF (AUROC, 0.94; misclassification rate, 0.06). However, the NN model had the poorest performance. The RF model showed that BLV seropositivity can be best predicted by testing beef cows during the dry season, which mostly coincides with the pre-calving processing and calving seasons, particularly for cattle raised in southern Florida. Conclusions The RF model shows promise for predicting BLV seropositivity in beef cattle. Key predictive risk factors include the dry season months coinciding with pre-calving and calving seasons and geographic location. These findings could help develop predictive tools for effective screening for BLV infection and targeted interventions.

The Bovine Leukemia Virus (BLV) Envelope (Env) glycoprotein complex is instrumental in viral infectivity and shapes the host’s immune response. This study presents the production and characterization of a soluble furin-mutated BLV Env ectodomain (sBLV-EnvFm) expressed in a stable S2 insect cell line. We purified a 63 kDa soluble protein, corresponding to the monomeric sBLV-EnvFm, which predominantly presented oligomannose and paucimannose N- glycans, with a high content of core fucose structures. Our results demonstrate that our recombinant protein can be recognized from specific antibodies in BLV infected cattle, suggesting its potential as a powerful diagnostic tool. Moreover, the robust humoral immune response it elicited in mice shows its potential contribution to the development of subunit-based vaccines against BLV.

Abstract Enzootic Bovine Leukosis (EBL), is infectious disease affecting especially older animals, although animals of all ages can be infected with the Bovine Leukemia Virus (BLV). Crioula Lageana is a locally adapted, rustic and long-lived bovine breed, important as a genetic resource. However, little is known about its health status, making it difficult to preserve the breed. In this sense, this study aims to assess the prevalence of EBL/BLV in different animal categories of Crioula Lageana cattle. Then, blood samples were collected from 308 animals from different categories: bulls, cows, heifers and male and female calves, whereby these animals were derived from six farms located in nuclei of in situ conservation for the Crioula Lageana breed in Planalto Serrano de Santa Catarina, Brazil and the blood samples were analyzed with hemogram, ELISA and PCR tests. There was a prevalence of 6.82% (21/308) for the ELISA test and 36.69% (113/308) for the PCR technique. There was no association between categories and natural infection or BLV positivity in PCR by the Chi-square test (P<0.05). Leukocytosis with lymphocytosis was observed in 11% (18/113) of PCR-positive animals. None of the evaluated animals presented bovine lymphosarcoma. We conclude that the BLV is present in all animal categories of the Crioula Lageana cattle, requiring the establishment of prevention and control measures to avoid the spread of the disease within herds. Resumo A Leucose Enzoótica Bovina (LEB), é uma doença infecciosa que afeta especialmente animais mais velhos, embora animais de todas as idades possam ser infectados com o Vírus da Leucemia Bovina (BLV). A Crioula Lageana é uma raça bovina adaptada localmente, rústica e longeva, importante como recurso genético. No entanto, pouco se sabe sobre seu estado de saúde, dificultando a preservação da raça. Nesse sentido, este estudo tem como objetivo avaliar a prevalência de EBL/BLV em diferentes categorias animais do gado Crioula Lageana. Foram coletadas amostras de sangue de 308 animais de diferentes categorias: touros, vacas, novilhas e bezerros machos e fêmeas, sendo estes animais provenientes de seis fazendas localizadas em núcleos de conservação in situ para a raça Crioula Lageana no Planalto Serrano de Santa Catarina, Brasil e as amostras de sangue foram analisadas por hemograma, ELISA e PCR. Houve prevalência de 6,82% (21/308) para o teste ELISA e 36,69% (113/308) para a técnica PCR. Não houve associação entre as categorias e infecção natural ou positividade do BLV na PCR pelo teste Qui-quadrado (P<0,05). Leucocitose com linfocitose foi observada em 11% (18/113) dos animais PCR-positivos. Nenhum animal avaliado apresentou linfossarcoma bovino. Concluímos que o BLV está presente em bovinos Crioula Lageana de todas as categorias animais avaliadas, sendo necessária a instituição de medidas de prevenção e controle para evitar a disseminação da doença dentro dos rebanhos.

Bovine leukemia virus (BLV) and human T-lymphotropic virus type 1 (HTLV-1) are closely related d-retroviruses that induce hematological diseases. HTLV-1 infects about 15 million people worldwide, mainly in subtropical areas. HTLV-1 induces a wide spectrum of diseases (e.g., HTLV-associated myelopathy/tropical spastic paraparesis) and leukemia/lymphoma (adult T-cell leukemia). Bovine leukemia virus is a major pathogen of cattle, causing important economic losses due to a reduction in production, export limitations and lymphoma-associated death. In the absence of satisfactory treatment for these diseases and besides the prevention of transmission, the best option to reduce the prevalence of d-retroviruses is vaccination. Here, we provide an overview of the different vaccination strategies in the BLV model and outline key parameters required for vaccine efficacy.

Bovine leukemia virus (BLV) causes enzootic bovine leukosis, the most common neoplastic disease in cattle. We previously reported the development and protocol of the luminescence syncytium induction assay (LuSIA), a method for evaluating BLV infectivity based on CC81-GREMG cells. These cells form syncytia expressing enhanced green fluorescent protein when co-cultured with BLV-infected cells. Recently, we confirmed CAT1/SLC7A1 functions as a receptor of BLV. Here, we focused on CAT1/SLC7A1 to increase the sensitivity of LuSIA. We constructed a bovine CAT1-expressing plasmid and established a new CC81-GREMG-derived reporter cell line highly expressing bovine CAT1 (CC81-GREMG-CAT1). The new LuSIA protocol using CC81-GREMG-CAT1 cells measures cell-to-cell infectivity and cell-free infectivity of BLV faster and with greater sensitivity than the previous protocol using CC81-GREMG. The new LuSIA protocol is quantitative and more sensitive than the previous assay based on CC81-GREMG cells and will facilitate the development of several new BLV assays.