Attenuation and Immunogenicity of a Live High Pathogenic PRRSV Vaccine Candidate with a 32-Amino Acid Deletion in the nsp2 Protein

Abstract

A porcine reproductive and respiratory syndrome virus (PRRSV) QY1 was serially passed on Marc-145 cells. Virulence of different intermediate derivatives of QY1 (P5, P60, P80, and P100) were determined. The study found that QY1 had been gradually attenuated during the in vitro process. Pathogenicity study showed that pigs inoculated with QY1 P100 and P80 did not develop any significant PRRS clinic symptoms. However, mild-to-moderate clinical signs and acute HP-PRRSV symptoms of infection were observed in pigs inoculated with QY1 P60 and P5, respectively. Furthermore, we determined the whole genome sequences of these four intermediate viruses. The results showed that after 100 passages, compared to QY1 P5, a total of 32 amino acid mutations were found. Moreover, there were one nucleotide deletion and a unique 34-amino acid deletion found at 5′UTR and in nsp2 gene during the attenuation process, respectively. Such deletions were genetically stable in vivo. Following PRRSV experimental challenge, pigs inoculated with a single dose of QY1 P100 developed no significant clinic symptoms and well tolerated lethal challenge, while QY1 P80 group still developed mild fever in the clinic trial after challenge. Thus, we concluded that QY1 P100 was a promising and highly attenuated PRRSV vaccine candidate.

Activation of pro- and anti-inflammatory responses in lung tissue injury during the acute phase of PRRSV-1 infection with the virulent strain Lena

“…response in vivo (Brockmeier et al, 2012;Lu et al, 2014) Although Lena virulent strain elicited a quite higher viraemia than the low virulent strain, no differences were observed in the antibody response in the early phase of infection. Similar results have been previously reported by others when comparing Lena with low virulent strains (Renson et al, 2017;Weesendorp et al, 2013), and confirm that PRRSV-1 virulence and specific non-neutralizing antibodies are not associated in the acute phase of infection.…”

Whole Genome Analysis of Two Novel Type 2 Porcine Reproductive and Respiratory Syndrome Viruses with Complex Genome Recombination between Lineage 8, 3, and 1 Strains Identified in Southwestern China

“…Sequence alignment of the 3′-UTR of SCya17 with other strains showed that SCya17 has a novel continuous 5-nt deletion in its 3′-UTR at positions 12 to 16 ( Figure 1 c), which is reported here for the first time. Previous studies indicated that the sequences of 5′-UTR and 3′-UTR are involved in viral virulence [ 40 , 41 , 42 ]. Whether the deletion in 3′-UTR of SCya17 is associated with its virulence requires further study.…”

Pathogenicity and genetic characteristics associated with cell adaptation of a virulent porcine reproductive and respiratory syndrome virus nsp2 DEL strain CA-2

“…Here, the discontinuous 111-1-19 DEL pattern was fully retained throughout the cell adaption process, suggesting that this genetic footprint alone may be irrelevant to virus attenuation. However, several previous studies have shown that additional 32 aa, 88 aa and 120 aa deletions were independently found downstream or upstream of the 30 aa nsp2 deletion in cell-adapted attenuated derivates of various HP-PRRSV strains, which indicates that the spontaneous deletion may be responsible for the attenuation of HP-PRRSV in vivo (Leng et al, 2012b;Lu et al, 2014;Wang et al, 2013). These results were inconsistent with the present study, which found that no extra deletion emerged in the nsp2 region or even at the whole genome after continuous passaging of the CA-2 virus in MARC-145 cells.…”