IMMUNOHISTOCHEMICAL STUDIES ON ORGAN TROP ISM OF DIFFERENT BIOTYPES OF BVD VIRUS IN EXPERIMENTALLY INFECTED SHEEP FETUSES

Paraffin sections from various organs of sheep fetuses following trans placental infection with noncytopathogenic (ncp) bovine viral diarrhoe a virus (BVDV) or cytopathogenic (cp) BVDV were stained immunohistoche mically with BVDV-specific monoclonal antibodies. Comparison of the di stribution of viral antigen in sections from fetuses of experiment A r evealed that in organs such as parotid, thyroid, thymus, lung, spleen, kidney, liver and skin from 20 days post inoculation (p. i.) onwards numerous antigen-containing cells were present. In organs of fetuses i nfected with cp BVDV, however, antigen-positive cells were only detect able until days 10 and 14 p. i. These findings suggest that the ncp BV DV used in experiment A replicated considerably faster and more effici ent than the cp BVDV used in experiment B and that the two virus bioty pes differ considerably concerning their tropism for fetal ovine organ s.