Immunohistochemical evidence for the localization of bovine viral diarrheavirus, a single-stranded RNA virus, in ovarian oocytes in the cow

Bovine viral diarrhea virus (BVDV) is a single-stranded RNA virus responsib le for enteric disease and reproductive failure in cattle. The virus can pa ss vertically from cow to fetus, causing abortion, birth of malformed calve s, and calves born with persistent and life-long infections. In this study, we investigated the tropism of BVDV in ovarian tissue from persistently in fected animals. Three heifers persistently infected with BVDV were euthanat ized and their ovaries were recovered. A specimen of each ovary was taken ( n = 6) for virus isolation, and the remaining ovarian tissue was stored at -70 C. Cryosections (6 mu m) cut from each ovary were analyzed for the pres ence of BVDV antigens by indirect immunofluorescence. The immunofluorescent analysis employed two monoclonal antibodies, WB103 and WB162, previously r aised against the nonstructural protein NS3 and the envelop glycoprotein E2 , respectively. High titers (6.97 +/- 0.17 log(10) tissue culture infective dose(50)/ml) of BVDV were recovered from 6/6 ovarian samples; NS3 and E2 w ere widely distributed within the ovarian stroma, the cumulus cell populati on, and the oocytes maturing in primordial, primary, and secondary follicle s. Overall, 362/1,939 (18.7%) of the oocytes contained BVDV antigens, and t here was no significant (P > 0.05) difference in the proportion of BVDV-inf ected oocytes recorded within the primordial (227/1,247, 18.2%), primary (1 22/630, 19.4%), and secondary (13/62, 21.0%) follicle populations. Although the developmental potential of the infected oocytes could not be establish ed in the present study, we conclude that bovine oocyte and the cumulus cel ls are susceptible to BVDV infection.