Melissa A. Lum

Comparative Pathogenicity of Nine US Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Isolates in a Five-Week-Old Cesarean-Derived, Colostrum-Deprived Pig Model:

One hundred forty-six 5-week-old cesarean-derived, colostrum-deprived (CDCD) pigs were inoculated intranasally with 1 of 9 US porcine reproductive and respiratory syndrome virus (PRRSV) isolates. Differences were found in severity of clinical respiratory disease, rectal temperatures (P ≤0.001), gross lung lesions (P ≤ 0.001), and microscopic lung lesions (P ≤ 0.05). Gross lung lesions were generally most severe 10 days postinoculation and were distributed primarily in the cranial, middle, and accessory lobes and ventromedial portion of the caudal lung lobes. Mean gross lung lesion scores estimating the percentage of lung affected by pneumonia at 10 days postinoculation ranged from 16.7% ± 2.8% (xX ± SEM, n = 10) for isolate ISU-51 to 62.4% ± 5.7% (n = 10) for isolate ISU-28. Microscopic lung lesions were characterized by hyperplastic and hypertrophied type 2 pneumocytes, septal infiltration by mononuclear cells, and accumulation of necrotic alveolar exudate. Lymph node follicular hyperplasia and focal necrosis was seen with all 9 isolates. This CDCD pig model was useful for demonstration of significant differences in pathogenicity among US PRRSV isolates. This difference in pathogenicity may help explain the variation in severity of clinical disease observed in field outbreaks of porcine reproductive and respiratory syndrome and should provide for meaningful comparison of PRRSV genotypes.

Characterization of a High-Virulence US Isolate of Porcine Reproductive and Respiratory Syndrome Virus in a Continuous Cell Line, ATCC CRL11171:

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Electrophoretic protein transfer applied to immunoelectrophoresis.

A method for electrophoretic transfer of a crossed immunoelectrophoretic (CIE) pattern from an agarose gel onto a nitrocellulose sheet is described. The CIE pattern to be transferred was formed using Nonidet P-40 solubilized, bovine herpes virus-1 (BHV-1) induced antigens and bovine hyperimmune serum. An autoradiogram of a CIE pattern, formed using [35S]methionine-labeled NP-40 solubilized, BHV-1 induced antigens and bovine hyperimmune serum, was used as a control pattern. Both antigen and antibody were transferred to the nitrocellulose sheet. This was demonstrated by the ability of transferred antigen to react with specific antibody detected by the addition of 125I-labeled anti-species antibody and transferred antibody to react with both [35S]methionine-labeled antigen and 125I-labeled protein A. This method has application for determining the specificity of monospecific sera for individual arcs in CIE patterns.