Abstract
BackgroundPorcine reproductive and respiratory syndrome virus (PRRSV) is mainly responsible for the significant economic losses in pig industry in the world. The adaptive immune responses of the host act as an important source of selective pressure in the evolutionary process of the virus. In the previous study, we confirmed that the amino acid (aa) residues at 102 and 104 sites in GP5 played an important role in escaping from the neutralizing antibodies (NAbs) against highly pathogenic PRRSV (HP-PRRSV). In this study, we further analyzed the aa mutants affecting neutralization susceptibility of NAbs in other structure proteins in NAbs resistant variants.MethodsBased on the different aa residues of the structural proteins between the resistant virus BB20s and the parent virus BB, 12 recombinant PRRSV strains containing these aa residue substitutions were constructed using reverse genetic techniques. The neutralizing antibody (NA) titers of the recombinant strains were tested on MARC-145 and porcine alveolar macrophages (PAMs). And the NAbs binding abilities of parent and rescued viruses were tested by using ELISA method.ResultsBy using the neutralization assay, it was revealed that the NA titer of N4 serum with rBB/Ms was significantly lower than that with rBB. Meanwhile, NA titer of the serum with rBB20s/M was significantly higher than that with rBB20s. The ELISA binding results showed that rBB/Ms had higher binding inability to N4 than did rBB. And alignment of M protein revealed that the variant aa residue lysine (K) at 70 was also existed in field type 2 and vaccine PRRSV strains.ConclusionsThe aa residue at 70 in M protein of PRRSV played an important role in regulating neutralization susceptibility to the porcine serum NAbs. It may be helpful for monitoring the antigen variant strains in the field and developing new vaccine against PRRSV in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0505-7) contains supplementary material, which is available to authorized users.
Highlights
Porcine reproductive and respiratory syndrome virus (PRRSV) is mainly responsible for the significant economic losses in pig industry in the world
In 2006, a HP-PRRSV strain with discontinuous 30 aa residues deletion in nsp2 protein associated with porcine high fever syndrome was reported in China, and overwhelmed swine industries in China and Vietnam [6,7,8]
Our results indicated that aa 198 within GP2 of the type 2 PRRSV strain BB was one antibody binding site, as determined using the recombinant virus rBB/ GP2s
Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) is mainly responsible for the significant economic losses in pig industry in the world. Since described in USA in 1987, porcine reproductive and respiratory syndrome (PRRS) has become one of the most important diseases in pigs, leading to significant economic losses in swine industry worldwide [1,2,3]. The causative agent, porcine reproductive and respiratory syndrome virus (PRRSV), was identified in 1991 in the Netherlands [4] and 1992 in the United States [5]. In 2006, a HP-PRRSV strain with discontinuous 30 aa residues deletion in nsp protein associated with porcine high fever syndrome was reported in China, and overwhelmed swine industries in China and Vietnam [6,7,8]. Anti-M mAbs have been described, but the neutralizing epitopes in M gene have not yet been identified [23, 31]
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