Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/11/2001
Publication Date: 11/11/2001
Technical Abstract: Cellular immune responses induced by an attenuated porcine reproductive and respiratory syndrome virus (PRRSV) and its wild-type parent virus (strain NADC-8) were compared. Two experiments were conducted using 52, 4- to 5-week-old pigs free of PRRSV and PRRSV-specific antibody. Each experiment had a sham-inoculated control group, an attenuated virus-inoculated group, and a wild-type parent virus inoculated group. The attenuated virus was 99.4% homologous with its parent virus. In experiment 2, a 4th group was inoculated with a different wild-type PRRSV (SDSU 73). Pigs were inoculated intramuscularly with their respective virus on day 0. Blood samples were collected on days 7, -4, 0, 3, 6, 9, 13 for both experiments and on day 20 or 21 for experiment 1 and 2, respectively. A panel of monoclonal antibodies was used to analyze peripheral blood leukocytes by two-color flow cytometric analysis. Results represent the combined data from the two experiments. The percentage of CD8+ T lymphocytes was significantly increased on day 6 to 13 in wild type NADC-8 group and on days 9 to 13 in the SDSU group compared to control and attenuated virus groups. The percentage of CD 4+ T cells was increased on day 9 for SDSU virus group only. Percentages of CD3+ T cells were increased on day 9 in both wild-type virus groups. After an initial decrease, the percentage of cells expressing Class II marker increased with time. Total white blood cell counts decreased shortly after infection then increased with time. No significant changes were found in peripheral blood leukocytes of pigs inoculated with attenuated PRRSV or sham inoculum. Results indicate that the peripheral blood leukocytes response to PRRSV infection mainly involves CD8+ T cells.