Animals and blood collection
The blood samples of BLV-infected and BLV-uninfected cattle, which were
used in this study, were obtained from several farmers and veterinarians
in Japan. BLV infection was confirmed by detection of the provirus using
nested polymerase chain reaction (PCR) that targets the viral LTR and by
detection of the anti-BLV antibody using a commercial ELISA kit (JNC,
Tokyo, Japan), as described previously [19]. The blood samples of
BLV-infected pregnant cattle (animals #1–#5, Table 1) were collected
at two points before delivery, on the day of delivery (day 0), and on
three points after delivery (days 1, 7, and 14). Blood collection on day
0 was performed before parturition.
For estradiol administration to BLV-infected cattle, 5 BLV-infected
cattle (animals #6–#10, Table 1) were kept in an animal facility at
the Faculty of Veterinary Medicine, Hokkaido University (Sapporo,
Hokkaido, Japan, animals #6 and #7), and a biosafety level I animal
facility at the Animal Research Center, Agricultural Research
Department, Hokkaido Research Organization (Shintoku, Hokkaido, Japan,
animals #8–#10). These animal experiments were approved by the Ethics
Committee of the Faculty of Veterinary Medicine, Hokkaido University,
and the Ethics Committee of the Animal Research Center, Agricultural
Research Department, Hokkaido Research Organization.
Blood samples were shipped immediately after collection and stored at
4°C until the experiment. After 24 hours from collection, blood samples
were used for the following analyses.