| Summary: | 碩士 === 國立中興大學 === 獸醫病理學研究所 === 90 === Classical swine fever (CSF) E2 subunit marker vaccine is new developed vaccine and can stimulate pigs developing good immune response against CSF virus infection. This study was aimed to evaluate the protective efficacy and control CSF virus infection in a virus contaminated pig farm using E2 subunit marker vaccine in Taiwan. Therefore, a massive vaccination program including all sows and pigs aged over 6-week-old were all vaccinated with E2 subunit marker vaccine in a CSF virus contaminated pig farm. Thereafter, piglets were regularly vaccinated with E2 subunit marker vaccine at 4- and 8-week-old. To evaluate the immune response of pigs stimulated with E2 subunit marker vaccine, several different vaccination programs including pigs receiving single vaccination at 4-week-old or double vaccinations at 2- and 6-week-old in some ear-tagged pigs were evaluated. CSF antibody were assayed by ELISA kits (CeditestO CSF E2 Ab ELISA) and SN method. Those results display that pigs after double vaccinations with E2 subunit marker vaccine, either at 2- and 6-week-old or 4- and 8-week-old, can develop strong immune responses and those antibodies can maintain as high ELISA titer with narrow derivation (PI value =103.53-104.86% or SN= 7.57-8.1 log2 ) to marketing. In contrast, pigs with single vaccination at 4-week-old developed moderate immune response compared those with double vaccinations. However, those induced antibodies also persisted to marketing (PI value =88.44%±15.58 or average SN = 6.22±1.2 log2). Moreover, the induction of immune response by E2 subunit marker vaccine was not interfered by maternal antibody, even though 2- week-old piglets with high maternal antibody (PI value =97.97%±10.54 , average SN = 7.25±1.13 log2) were shot with E2 subunit marker vaccine once. To evaluate the efficiency of the E2 subunit marker vaccine in the control of CSF virus persistence, surveillance by pathology, antigen ELISA, RT-PCR and discriminated Erns antibody on sick growers or healthy finishers were regularly monitored. Before the application of E2 subunit vaccine in the trial farm, low frequency of Erns antigen and moderate levels of Erns antibody could be persistently detected in sick growers. However, there was no more evidence of CSF virus infection in the trial farm after E2 subunit marker vaccine applied. Moreover, an experiment of protective efficiency of E2 subunit marker vaccine on vaccinated pigs following with high virulent CSF virus challenge was conducted. The results display that pigs 2 weeks post vaccination (WPV) have developed protective immunity against virulent virus challenge, but still show mild transit clinical signs. There was no clinical signs, leukopenia, virus shedding, viremia, and pathological lesions in those pigs challenged with high virulence CSF virus 3 WPV or boosted with E2 subunit marker vaccine 4 weeks later. Taken those results together, CSF E 2 subunit maker vaccine can efficiently induce high levels of E2 antibody and protect pigs from CSF virus infection that may be helpful in control virus persistent infection in virus contaminated pig farm and promotion of CSF eradication program in Taiwan.
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