Veterinary Research Forum

Abstract Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, an oncogenic deltaretrovirus that has emerged as a potential zoonotic infection. The BLV naturally infects cattle and causes economic losses through a slow persistent infection with various clinical symtoms following preleukosis. The main objective of this study was to determine the seroprevalence of BLV antibodies in cattle and buffaloes in the border provinces of the Eastern Anatolia region, Türkiye, using the agar gel immunodiffusion (AGID) assay and  enzyme-linked immunosorbent assay (ELISA). For this purpose, a total of 1,033 serum samples were collected from 982 cattle and 51 buffaloes from the provinces of Ağrı (n = 178), Iğdır (n = 252), Kars (n = 317), Van (n = 221), and Hakkari (n = 65) during 2021 - 2022. In AGID and ELISA tests, seropositivity for BLV-specific antibodies was not detected in cattle and buffaloes from the mentioned provinces. This study revealed that BLV was not circulating in cattle and buffaloes in the easternmost border provinces of Türkiye during the sampling period and contributed to determine the status of BLV in the mentioned region. Due to the presence of virus in other regions of Türkiye and neighboring countries, Iran and Iraq, it is recommended to control animal movements, continue efforts to combat the transmission of the virus, and maintain control measures.

Abstract The bovine leukemia virus (BLV) is an important infectious agent transmitted from cattle to humans. It is considered one of the oncogenic viruses in breast cancer, so an accurate detection of this virus is important. The study aimed to design a specific and sensitive method based on TaqMan^® real-time polymerase chain reaction (RT-PCR) for BLV detection. Probes and primers were designed using bioinformatics software for a 108 pairs region of the BLV tax gene. Criteria employed for determining analytical sensitivity were prepared using in-vitro RNA transcriptions. The National Center for Biotechnology Information (NCBI), basic local alignment search tool (BLAST) databases various viral panels and genomic samples from healthy individuals (Qom Province, Iran in 2023) were used to verify analytical specificity and clinical specificity, respectively. This method can measure a minimum of 10 copies of DNA and RNA mL^-1. Moreover, the assay is linear in the range of 10⁰ - 10⁹ copies mL^-1. By testing negative specimens, the method specificity was 100%. The reproducibility results of the reaction were examined at the intra- and inter-assay comparison. In fact, 10 technical replicates of each concentration of the control sample were analyzed in each working reaction. Due to the locally made kit, exact sensitivity and specificity, rapid analysis, and relatively low cost, as compared to commercial kits of other countries, the method introduced in the present study could be suitable for accurate detection of the BLV. Also, the TaqMan^® real-time PCR method could be detected in cattle and human and before malignant changes of breast cancer which could reduce infection and breast cancer.

Abstract Bovine Leukemia Virus (BLV) is an oncogenic retrovirus of the genus Deltaretrovirus. The genome of BLV encodes a cluster of 10 mature microRNAs (miRNAs). Considering the importance of miRNAs in regulating gene expression, it seems that each of the miRNAs of BLV plays a vital role in the process of pathogenesis and tumorigenesis of the virus. First, sequences of each of the miRNAs of BLV were selected and downloaded from the miRBase database. The sequences were then investigated using TargetScan and miRWalk to identify target genes of each of the mature miRNAs of the virus. Second, the expression levels of the two miRNAs with the highest number of target genes in B lymphocytes and lymphoid tissues were evaluated using qPCR and were compared between cattle with different forms of BLV infection: PL form was compared to ‎aleukemic (AL) form (Group 1) and BLV+ with normal lymph nodes were compared to lymphosarcoma form (Group 2). We identified a total of 1595 target genes of the micro RNAs. The miRNAs with the highest target genes included miR-B4-3p with 760 and B2-5p with 102 target genes. In the second phase, miRNA expression in BLV-infected animals was investigated. The Fold Change (FC) values for miR-B4-3p and miR-B2-5p in group 1 were 22 and 67, respectively. In the second group, the FCs for miR-B4-3p and miR-B2-5p were 47 and 133, respectively. The expression was significantly higher in persistent lymphocytosis (PL) cattle in group one and lymphosarcoma cattle in group two.

Abstract Bovine leukemiavirus (BLV) is one of the most important carcinogenic viruses genetically related to the human T-cell lymphotropic viruses (HTLV-1 and HTLV-2). The virus infects type B lymphocytes and creates lymph glands tumors. Recently, the association between the presence of this virus and breast cancer has been addressed in humans. Here, we studied the prevalence of BLV in the samples of raw milk of native Iranian and Iranian-foreign cows in traditional, semi-industrial and industrial dairy farms in rural and urban areas of Zanjan province. Raw milk samples of cows were collected manually in sterile tubes. The samples were tested by nested-PCR method. Forty samples (9.93%) out of 403 samples showed BLV contamination. In this study, nested-PCR was successfully applied to determine the level of contamination in raw milk samples from cows infected with BLV. Furthermore, a relatively high rate of BLV infection was found in dairy cows in Zanjan province, northwestern of Iran.

Abstract The purpose of this study was to determine the prevalence of bovine leukemia virus (BLV) in Khorasan Razavi and Khorasan Shomali provinces which are the main provinces located in the northeast of Iran. Total number of 429 blood samples were collected from industrial dairy herds. The samples were categorized based on province, age (2-3, 4-6, and 7-10 years old), calving (≤ 2, 3-5, and > 5) and herd size (≤ 100, 101-250, and > 250) and examined by indirect ELISA. The results of this study showed that 109 (25.4%) out of 429 serum samples were BLV seropositive. The BLV prevalence among cattle of dairy herds of Khorasan Razavi and Khorasan Shomali provinces were 29.8% and 1.5%, respectively. The results showed that the number of seropositive animals was increased significantly with the age (p < 0.05). The infection rate in animals 2-3, 4-6 and 7-10 years old were 12.1%, 26.7% and 45.6%, respectively. It was shown that BLV prevalence according to calving ≤ 2, 3-5 and > 5 was 15.5%, 33.0% and 42.9%, respectively, with a significant difference between calving ≤ 2 and > 5 (p < 0.001). The prevalence of BLV among herd size of ≤ 100, 101-250 and > 250 was 19.7%, 14.3% and 42.1%, respectively, which was significantly higher in herds with more than 250 cattle (p < 0.05). This study revealed that BLV infection in dairy herds of northeast of Iran was influenced by geographical location (province), age, calving and herd size.