Efficacy of the classical swine fever (CSF) marker vaccine Porcilis (R) Pesti in pregnant sows

The efficacy of the classical swine fever (CSF) subunit marker vaccine Porc ilis(R) Pesti based on baculovirus expressed envelope glycoprotein E2 of CS F virus (CSFV) was evaluated in pregnant sows. Ten gilts were vaccinated wi th one dose of marker vaccine, followed by a second dose 4 weeks later. Fou r gilts remained unvaccinated and received a placebo at the same times. Thi rty-three days after the second vaccination all animals were artificially i nseminated. Neither local or systemic reactions nor an increase of body tem perature were observed after vaccinations. All gilts showed a normal course of pregnancy. Thirty-five days after first vaccination all animals develop ed E2 specific neutralising antibodies with titres in the range of 5.0 and 7.5 log(2). No antibodies to CSFV-E-rns were found in ELISA. On day 65 of gestation (126 days after the first immunisation) all sows wer e infected intranasally using 2 mi (10(6.6) TCID50/ml) of the low virulent CSFV strain "Glentorf". After challenge in two of the unvaccinated control sows a slight transient increase of body temperature was observed, whereas leukopenia was demonstrated in all control animals. In addition all control s became viraemic. Vaccinations with the CSFV subunit vaccine protected the animals from clinical symptoms of CSF In two sows a moderate decrease of l eukocyte counts was detected on day 5 post infection. In contrast to the un vaccinated control sows in none of the vaccinated animals virus was isolate d from the nasal swabs or the blood. Approximately 40 days after challenge all sows were killed and necropsy was done. The sows and their offspring were examined for the presence of CSFV in blood, bone marrow and different organs. No virus was found in any of th e sows. In contrast, in all litters of the control sows CSFV was found in t he blood as well as in the organ samples. Nine out of 10 litters of the vac cinated sows were protected from CSFV infection. Blood samples, lymphatic o rgans and bone marrow of these animals were all virologically negative. Whe n sera were tested for CSFV-antibodies all sows had developed E-rns-specifi c antibodies but no CSFV-specific antibodies were found in any of the proge ny. It was concluded that vaccination with CSF subunit marker vaccine Porcilis( R) Pesti protected 90% of the litters from viral infection when sows were c hallenged mid-gestation using the CSFV-strain "Glentorf". (C) 2000 Elsevier Science B.V. All rights reserved.