Inhibition of Th1 responses in BLV-infected pregnant cattle.
To reveal the association of parturition with the progression of BLV
infection, in this study, we focused on the immunosuppressive function
of PGE2, which is also an important factor for the
induction of parturition in pregnant animals. To investigate whether
PGE2 is involved in immune dysfunction in pregnant
cattle, we examined the PGE2 kinetics and Th1 responses
of BLV-infected pregnant cattle (Figures 2a–2c and Supplemental Figures
1a–1c). Compared to the samples collected about 2 weeks before the
parturition (Pre, day −17–day −12), PGE2 concentrations
in sera were significantly increased on the day of parturition (day 0,
Figure 2a). In contrast, Th1 responses against Con A were significantly
suppressed on day 0 (Figure 2b). Th1 responses against BLV-antigen
tended to be suppressed on day 0 (Figure 2c). Our previous studies have
demonstrated that PGE2 suppresses the production of Th1
cytokines from bovine PBMCs, and the inhibition of PGE2production using a COX-2 inhibitor activates BLV-specific Th1 responses
[16, 17]. Taken together, these results suggest that
PGE2 induction before delivery is associated with the
inhibition of Th1 responses in pregnant cattle.