Humoral immune responses and viral shedding following vaccination with modified live porcine reproductive and respiratory syndrome virus vaccines

Abstract

The antibody response and pattern of shedding of vaccine virus following vaccination with modified live genotype I or II porcine reproductive and respiratory syndrome virus (PRRSV) vaccines (MLVs) were investigated. Ninety PRRSV-free pigs were divided randomly seven, groups including the NEG, EU1, EU2, US1, US2, US3 and US4 groups. The NEG group was unvaccinated. The EU1, EU2, US1, US2, US3 and US4 groups were vaccinated with the following MLVs: AMERVAC PRRS, Porcillis PRRS, Fostera™ PRRS, Ingelvac PRRS MLV, Ingelvac PRRS ATP, and PrimePac™ PRRS+ , respectively. Sera were quantitatively assayed for viral RNA using qPCR. Antibody responses were measured using Idexx ELISA and serum neutralization (SN). Shedding of vaccine virus was investigated using sentinel pigs and by detection of viral RNA in tonsil scrapings. Antibody responses were detected by ELISA at 7-14 days post-vaccination (DPV) and persisted at high titers until 84 DPV in all MLV groups. The SN titers were delayed and isolate-specific. SN titers were higher for the homologous virus than for heterologous viruses. Age-matched sentinel pigs introduced into the EU2, US2 and US3 groups at 60 DPV seroconverted. In contrast, sentinel pigs introduced at 84 DPV remained negative in all of the MLV groups. Vaccine viral RNA was detected in tonsil scrapings from the EU2, US2 and US3 groups at 84-90 DPV. No viral RNA was detected beyond 70 DPV in the EU1, US1 and US4 groups. In conclusion, all MLV genotypes induced rapid antibody responses, which were measured using ELISA. The development of SN antibodies was delayed and isolate-specific. However, the shedding pattern was variable and depended on the by virus isolate used to manufacture the vaccine.

Dynamics and Differences in Systemic and Local Immune Responses After Vaccination With Inactivated and Live Commercial Vaccines and Subsequent Subclinical Infection With PRRS Virus

“…There are only a few papers published providing a comprehensive picture of immune response after vaccination against PRRSV (40)(41)(42)(43) because the majority of the existing studies are based mainly on the evaluation of the vaccination effectiveness by monitoring the immune responses found in the blood (5,30,33,(44)(45)(46). Our results show that antibodies after immunization and infection, and the virus after infection, can be detected in all the monitored compartments (blood, respiratory tract, intestine).…”

Efficacy and safety of simultaneous vaccination with two modified live virus vaccines against porcine reproductive and respiratory syndrome virus types 1 and 2 in pigs

“…Virus could be detected in serum of several pigs at DPC 42-56, and four (two VAC-T1 and two VAC-T2) pigs tested positive up to 62 days after vaccination. Previous studies have estimated the length of viremia after PRRSV vaccination with MLV vaccines to be 29 days on average (range 10-42 days) [12,[17][18][19][20], but PRRSV viral RNA has been detected in tonsil scrapings up to 90 days post vaccination [20]. The different studies used different methods to investigate the presence of virus in serum, which may account for the differences seen.…”

Cell-mediated immune response and protective efficacy of porcine reproductive and respiratory syndrome virus modified-live vaccines against co-challenge with PRRSV-1 and PRRSV-2

“…after PRRSV challenge. The primers specific for the ORF5 gene of either PRRSV-1 or PRRSV-2 and detection conditions were described previously 12 . In brief, total RNA was extracted using NucleoSpin RNA Virus extraction kit (Macherey-Nagel, Duren, Germany) in accordance with manufacturer's instructions.…”