Study shows PRRS vaccine can provide protection against challenge with HP-PRRSV

Immune response, IL-10 and protective efficacy against a single HP-PRRSV challenge or in conjunction with PRRSV1 of pigs intradermally and intramuscularly vaccinated with modified live PRRSV1.

Introduction

Co-existence of PRRSV1 and PRRSV2 has been increasingly reported in several Asian countries, including China, Korea, Vietnam and Thailand1. In the presence of co-infection with both PRRSV genotypes, clinical diseases are more severe compared to a single infection with either genotype. The study was conducted to test the efficacy of UNISTRAIN® PRRS when administered intramuscularly or intradermally in pigs against a challenge with a PRRSV2 and a challenge with co-infection with PRRSV2 and PRRSV1.

Materials and Methods

Forty-two PRRSV free pigs at 3 weeks of age were randomly allocated into 7 groups of 6 pigs each. Groups VacIM/PRRS2 and VacIM/PRRS1+2 were intramuscularly vaccinated with UNISTRAIN® PRRS. Groups VacID/PRRS2 and VacID/PRRS1+2 were intradermally vaccinated with UNISTRAIN® PRRS. Group NV/PRRS2, NV/PRRS1+2 and NV/Unch were vaccinated with PLACEBO. At 35 days post vaccination, groups VacIM/PRRS2, VacID/PRRS2 and NV/PRRS2 were intranasally challenged with FDT10US23 isolate (HP-PRRSV) and groups VacIM/PRRS1+2, VacID/PRRS1+2 and NV/PRRS1+2 were intranasally challenged with a co-infection of AN06EU4204 and FDT10US23 isolates (PRRSV1 and HP-PRRSV, respectively), at 1 ml of each isolate/nostril. Group NV/Unch was kept as non-vaccinated/non-challenge control. Following vaccination and challenge, pigs were monitored for PRRSV quantification by RT-qPCR, safety of the vaccine by IL-10, immune response including ELISA and IFN-γ-PC and macroscopic lung lesions.

Results

Following vaccination, ID vaccinated pigs had shorter viraemic phase and lower RNA level compared to IM vaccinated pigs. ID vaccinated pigs had significantly lower IL-10 level than IM vaccinated pigs (Figure1), but IFN-γ-PC were significantly higher (Figure2). There was no difference in antibody response.

No macroscopic lung lesions were observed in pigs of the NV/Unch group throughout the experiment. In contrast, pigs in the NV/PRRS2 and NV/PRRS1+2 groups had significantly higher scores compared to that of the vaccinated challenged groups at 7 DPC. The NV/PRRS1+2 groups had the significantly highest score. Macroscopic lung lesions in the VacID/PRRS2 and VacID/PRRS1+2 groups were significantly lower compared to that of the VacIM/PRRS2 and VacIM/PRRS1+2 groups.

Figure 1
Figure 1

Porcine interleukin-10 (IL-10) concentration in cell culture supernatants of stimulated PBMC with vaccine virus. Values are expressed as mean±SEM. Different letters indicate statistical (P<0.05) differences among groups.

Figure 2
Figure 2

PRRSV-specific IFN-γ-producing cells (IFN-γ-PC) in stimulated PBMC with: (A) homologous virus; (B) heterologous type 1 PRRSV (AN06EU4204); and (C) heterologous type 2 PRRSV (FDT10US23). Values are expressed as mean±SEM. Different letters indicate statistical (P<0.05) differences among groups.

DISCUSSION In conclusion, the results of the study suggested UNISTRAIN® PRRS administered, either by ID or IM, can provided protection against challenge with HP-PRRSV, either alone or in conjunction with PRRSV1 as demonstrated by reduced lung lesion and viremia. ID route might represent an alternative to improve vaccine efficacy as it provided lower IL-10 and higher IFN-γ-PC.

References
References
1. Nilubol et al.
(2013) . Arch Virol 158(5):943-53

Madapong, A.

Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand

Saeng-Chuto, K.

HIPRA, Amer (Girona), Spain

Joel Miranda

HIPRA, Amer (Girona), Spain

Tantituvanont, A.

Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok, Thailand

Nilubol, D.

Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand
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