| Popis: |
The porcme reproductive and respiratory syndrome (PRRS) IS an Important wal 1nfect1on of sw1ne that can pers1st in lymphoid organs of Infected p1gs despite the 1nduct1on of specific 1mmune responses, suggesting an immune evasion mechanism. Vaccmat1on has been shown to prevent climcal s1gns but remains ineffective aga1nst v1ral pers1stence. Our obJective was to mvestigate the immunolog1cal disorders related to vaccination and subsequent challenge by a v1rulent strain. Groups of piglets were vaccmated with RespPRRS vaccine (Boehringer-lngelheim) and challenged 4 weeks later with the virulent LHVA-93-3 strain of the PRRS v1rus. Ammals were sacnficed at various t1mes after vaccination and the lungs and lymphoid organs were collected Lymphoid cell subsets were analysed and wal persistency was determmed by RT-PCR No modifications were observed 1n the percentages of CD2+CD4+ and CD2+CD8h•gh T cells in PRRSV-vacc1nated animals, whereas these cells decreased in spleen, tons1ls and lymph nodes 1n vaccinated-challenged p1glets Similarly, spec1fic antibody secretmg-B cells were increased after vaccination, but decreased follow1ng challenge w1th the virulent v1rus. Persistent wal RNA was found in lungs, blood, tonsils, and lymph nodes up to 24 days e1ther 1n vaccmated or vaccinatedchallenged p1gs. Taken together, these results 1nd1cate that vacc1nat1on favours a decrease in CD4+ and COB cells and antibody producing-B cells 1n blood and lymphoid organs and viral pers1stency 1n animals challenged with a wulent virus, suggesting a failure in the immune processes. |
