Diagnosis of naturally occurring bovine viral diarrhea virus infections in ruminants using monoclonal antibody-based immunohistochemistry.

Formalin-fixed paraffin-embedded tissues from 50 spontaneous cases (39 bovine, nine ovine, two caprine) of bovine viral diarrhea virus (BVDV) infection diagnosed by virus isolation were retrospectively examined for BVDV antigen by immunohistochemistry using anti-BVDV gp-43 monoclonal antibody (Mab 15C5). The cases were separated into enteric disease syndrome, respiratory disease syndrome, and abortion/weak calf syndrome based upon clinical disease. The purposes of the study were to 1) compare routine virus isolation with immunohistochemistry in determining BVDV infection and 2) define tissue and cellular distribution of BVDV in various clinical manifestations of infection. In bovids, there was 100% concordance of virus isolation and immunohistochemistry using Mab 15C5 in cases of enteric disease (mucosal disease, acute and chronic diarrhea, neonatal diarrhea), respiratory disease, and abortion. When laboratory tests were restricted to gastrointestinal tissue and/or feces, virus isolation detected BVDV in only 65% of cattle, whereas immunohistochemistry detected BVDV antigen in 100% of cattle. Immunohistochemical detection of pestivirus was poor in cases of ovine abortion, ovine hairy shaker syndrome, and caprine abortion. The tissue distribution of BVDV antigen was widespread in individual cattle with all clinical forms of BVDV infection. Viral antigen accumulation was spatially correlated with tissue lesions (in the absence of other pathogens) only in the gastrointestinal tract, lymphoid tissue, lung, placenta, and eye. This study demonstrates the utility of immunohistochemistry using Mab 15C5 to diagnose BVDV infections in cattle with a broad spectrum of clinical disease.

Passive transfer of antibody to Ehrlichia risticii protects mice from ehrlichiosis.

Mice that recovered from Ehrlichia risticii infection were immune to a challenge dose of 100 50% lethal doses. Immune or normal mouse serum was passively transferred to mice challenged with E. risticii. Clinical signs of ehrlichiosis were completely prevented in 22 of 24 recipients of immune serum, and the onset of signs of illness was delayed in the remaining two mice compared with the onset of illness in 24 of 24 recipients of nonimmune serum. Purified immunoglobulin G (IgG) was used to passively protect mice from infection with E. risticii. All 15 mice that received IgG from normal serum but none of the 15 mice that received IgG from immune serum developed clinical signs of illness. Antibodies in immune mouse serum immunoprecipitated [35S]methionine metabolically labeled E. risticii proteins with apparent molecular masses ranging from 14 to 90 kDa. The major antigens recognized by dilute immune serum in immunoblot analysis had molecular masses of 62, 53, 40, 33, 27, and 25 kDa, and the 62- and 27-kDa antigens were prominent in immunoprecipitations with dilute antibody. Antigens with molecular masses of 62, 53, 40, 33, and 27 kDa are likely surface exposed, as determined by immunoprecipitation of 125I-labeled organisms with immune mouse serum.