Evaluation of Vertical Transmission Potential of An Attenuated Classical Swine Fever Virus Marker Vaccine Candidate RecC-M1
To investigate the vertical transmission potential of an attenuated classical swine fever virus(CS-FV)marker vaccine candidate RecC-M1,this experiment employed a double immunization scheme by im-munizing twelve gilts,with RecC-M1 at a dose of 5.0×103.5 TCID50 via intramuscular injection in the neck muscles.Twenty randomly selected gilts from the same farm served as control animals and were immunized with the attenuated C strain vaccine at 750 RID using a conventional immunization program.The experi-mental gilts were observed for clinical symptoms,and their farrowing performance was recorded.Nasal and rectal swab samples were collected on days 3,5,7,and 14 post-primary immunization.Blood samples were collected via tail vein puncture during mid-pregnancy and on the day of farrowing.Viral viremia and shed-ding were determined by quantitative PCR(qPCR),while antibody levels against the corresponding anti-gens for BVDV1(bovine viral diarrhea virus type 1)and CSFV were assessed by indirect ELISA.On the day of parturition,two newborn piglets(a total of 24 piglets)deprived of colostrum were selected from each gilt that received RecC-M1.Post-mortem examinations were conducted to observe gross lesions.Ton-sils,lymphs nodes,spleens,and bladder were sampled for histopathological observations.Blood samples were collected for detection of CSFV antibodies and viral nucleic acids.The results showed that all gilts im-munized with RecC-M1 did not show any clinical symptoms,and were negative of viral nucleic acid in swab samples collected within two weeks post-vaccination.Antibody levels against CSFV E2 and BVDV1-Erns in the sera from gilts remained high during mid-pregnancy and farrowing.There were no significant differ-ences in litter size,stillbirths,or weak piglets between RecC-M1 vaccinated and control gilts.Post-mortem examination revealed that the newborn piglets from RecC-M1-vaccinated gilts did not have any gross path-ological changes in the tonsils,lymph nodes,spleens,kidneys,or bladders.Histological examination showed normal tissue structures in tonsils,lymph nodes,spleens and kidneys with no evidence of hemorrhagic changes.Viral nucleic acid and specific antibody conversion were not detected in the blood and tissue sam-ples from piglets.This study indicated that the attenuated CSFV marker vaccine candidate RecC-M1 is safe for both gilts and piglets,and vertical transmission did not occur,thus providing experimental foundation for its industrial development.
万方数据
维普
