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Bulletin No. 16 - Fall 2003
Fourth International Symposium on Emerging and Re-emerging Pig diseasesPorcine Reproductive and Respiratory Syndrome (PRRS)
XIAO Z, MURTAUGH MP, JONHSON CR, BATISTA L, DEE SA
Immunity to porcine reproductive and respiratory syndrome virus (PRRSV) : systemic and local responses in acute and persistent infection.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 45-46
Humoral and cell-mediated immune responses to PRRSV were assessed in peripheral blood and lymphoid tissues during acute and persistent infection. In a first experiment, 120 gilts of four months of age were inoculated with a PRRSV strain while in a second experiment 33 pigs of 5-6 weeks of age were inoculated with Ingelvac? PRRS ATP vaccine strain. The increase of antibodies to GP5 appeared to be associated with clearance of virus from the circulation. The proportion of interferon gamma secreting T cells was determined and provided a scale to measure cell-mediated immune response to PRRSV. The results show great individual variations in the ability to develop immunity to PRRSV infection as well as a lack of stimulation of cell-mediated immune response which both probably facilitate the establishment of persistent infections. The significantly increased levels of CD8+ cells suggest that these lymphocytes are likely to play a great role in immunity to PRRSV. Tonsils showed high levels of virus and particularly low levels of activated lymphocytes, they are thus assumed to be somehow involved in PRRSV infection. The results also indicate that stimulating the initial immune response, known to be inefficient to PRRSV, may be a way of improving humoral and cell-mediated immune response to PRRSV.
