Efficacy of the Synergy Between Live-Attenuated and Inactivated PRRSV Vaccines Against a NADC30-Like Strain of Porcine Reproductive and Respiratory Syndrome Virus in 4-Week Piglets.

Chaosi Li,Shuhe Fang,Kai Chen,Chunhong Zhang,Zhi Sun,Zhicheng Liu,Jie Qian,Lv Huang,Jianfeng Zhang,Yulong Hu,Nian Huang

doi:10.3389/fvets.2022.812040

Abstract

The NADC30-like strain of porcine reproductive and respiratory syndrome virus (PRRSV) is a novel strain responsible for substantial economic losses to swine production in China. This study evaluated the cross-protective efficacy of the synergy between live-attenuated and inactivated PRRSV vaccines compared with a single vaccination with PRRS modified-live virus (MLV) vaccine against challenge with NADC30-like strain, v2016/ZJ/09-03. A total of 45 PRRSV free pigs were randomly divided into five groups: (1) strict control (SC); (2) positive control (PC); (3) single MLV dose (M1); (4) primed intramuscularly with MLV and boosted with killed vaccine 3 weeks later (MK1); and (5) intramuscular prime MLV boosted subcutaneously with killed vaccine B 3 weeks later (MK2). Serological tests in MK groups revealed no differences in both anti-N and anti-GP protein antibodies compared with M1 group, and failed to provide further protection against clinical signs, virus shedding, and gross lesions. However, the viremic titer, gross lung lesions, and average daily weight gain were significantly improved in the MLV vaccinated groups, suggesting that MLV provides substantial cross-protection against the NADC30-like virus. Thus, as a booster, the killed vaccine confers minimal additional protection in NADC30-like infected piglets.

Highlights

IntroductionPorcine reproductive and respiratory syndrome (PRRS) was first reported in North America in 1987 [1] and was subsequently identified in both Europe and Asia in the 1990s [2,3,4,5]
Porcine reproductive and respiratory syndrome (PRRS) was first reported in North America in 1987 [1] and was subsequently identified in both Europe and Asia in the 1990s [2,3,4,5].Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, single positivestranded RNA virus that belongs to the family Arteriviridae, genus Betaarterivirus, and consists of two genotypes: PRRSV-1 (European) and PRRSV-2 (North American)
Serum samples were heat-inactivated at 56◦ C for 30 min, 100-μl serially diluted serum was mixed with an equal volume of v2016/ZJ/09-03 containing 200 TCID50

Summary

Introduction

Porcine reproductive and respiratory syndrome (PRRS) was first reported in North America in 1987 [1] and was subsequently identified in both Europe and Asia in the 1990s [2,3,4,5]. Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, single positivestranded RNA virus that belongs to the family Arteriviridae, genus Betaarterivirus, and consists of two genotypes: PRRSV-1 (European) and PRRSV-2 (North American). Since 2014 in China, an increasing number of studies have attempted to identify an available PRRS vaccine that can confer sterilizing or even effective heterologous-protection against the prevalent NADC30-like strain [26, 28,29,30]. None of the commercial vaccines on the market are ideal, which may be the reason that this strain escaped host immunity, spread quickly across the mainland, and rapidly became the dominant strain in

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