Development of a microchip electrophoresis-based, high-throughput PCR-RFLP method to type Tax 233 variants of bovine leukemia virus in Japan

Abstract

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis (EBL). We used microchip electrophoresis in combination with automatic image analysis to develop a novel high-throughput PCR-RFLP to type the gene sequences that encode BLV Tax 233. This method revealed that 233L-Tax is more prevalent than 233P-Tax in cattle in Japan. The proportion infected with BLV carrying the gene encoding 233L-Tax was significantly higher in Holstein cattle than in Japanese Black cattle. Holsteins infected with BLV encoding 233L-Tax had higher proviral loads than did Holsteins infected with BLV encoding 233P-Tax and Japanese Blacks infected with BLV encoding 233L-Tax or 233P-Tax. The novel method developed in this study will be a useful tool for identifying cattle harboring BLV with a higher risk of EBL and viral transmission.

Epidemiological evidence for early-onset of enzootic bovine leukosis by L233-Tax-carrying bovine leukemia virus in Japanese Black cattle

“…Moreover, almost all BLVs infecting Hol cattle carry L233-Tax, whereas the viruses infecting JB cattle possess both forms of Tax equally [7,17]. The purpose of this study was to investigate the characteristics of EBL among JB cattle with a focus on Tax harbored in the tumors and the relation with Hol cattle.…”

“…It was reported that most viruses detected in Hol cattle possessed L233-Tax nationwide [7,17] and that the prevalence of BLV was higher in dairy cows than in beef cattle [15]. A significant number of farms fatten JB cattle together with JB-Hol crossbred cattle and Hol beef cattle, and ET is widely conducted in Japan, especially in dairy areas.…”

“…Recently, we also reported that L233-Tax-expressing cells secrete a number of molecules that play critical roles in vesicular development and angiogenesis at greater levels than P233-Tax-expressing cells and that L233-Tax had greater tumorigenic potential than P233-Tax through a murine subcutaneous xenograft study [ 14 , 21 ]. It was also reported that the proviral load (PVL) in the blood of Hol cattle infected with L233-Tax-carrying BLV was significantly higher than that in animals infected with P233-Tax-carrying BLV [ 17 ]. Thus, amino acid position 233 in Tax is anticipated to have clinical value as a prognostic factor for BLV infection.…”

“…Embryo transfer (ET) technology is utilized to both produce highly genotypic JB beef cattle and impregnate cows in Japan through surrogate birthing by Hol dairy cows, in which the seroprevalence of BLV was higher than that in both fattening and breeding beef cattle [ 15 ]. Moreover, almost all BLVs infecting Hol cattle carry L233-Tax, whereas the viruses infecting JB cattle possess both forms of Tax equally [ 7 , 17 ]. The purpose of this study was to investigate the characteristics of EBL among JB cattle with a focus on Tax harbored in the tumors and the relation with Hol cattle.…”

“…The chi-squared test demonstrated that L233-Tax- and P233-Tax-carrying viruses more commonly infected samples derived from animals born in the Hokkaido and Tohoku regions, respectively. It was reported that most viruses detected in Hol cattle possessed L233-Tax nationwide [ 7 , 17 ] and that the prevalence of BLV was higher in dairy cows than in beef cattle [ 15 ]. A significant number of farms fatten JB cattle together with JB-Hol crossbred cattle and Hol beef cattle, and ET is widely conducted in Japan, especially in dairy areas.…”