Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/4/2011
Publication Date: 2/6/2011
Citation: Faaberg, K.S., Guo, B., Lager, K.M., Brockmeier, S.L., Henningson, J.N., Schlink, S.N., Miller, L.C., Yang, H. 2011. Analysis of Chinese porcine reproductive and respiratory syndrome virus type 2 strain in United States swine [abstract]. ASM Conference on Viral Genome Replication. Poster No. 55A. p. 69. Interpretive Summary:
Technical Abstract: Novel isolates of porcine reproductive and respiratory disease virus (PRRSV) appeared in China in 2006. We imported a cDNA clone of a Chinese strain from which infectious virus was obtained (rJXwn06). Our hypothesis was that the novel PHFD strains would not result in the severe clinical disease seen in Asia when inoculated into U.S. high health swine. Under ABSL3 biocontainment, swine were infected by intranasal inoculation with either 2 ml of 10**6 TCID50/ml rJXwn06 (n=12 challenge, n=4 contact) or the Type 2 prototype strain VR-2332 (n=8), or a sham inoculum (n=8). The pigs were monitored for 13 days during which time the JXwn06 swine developed severe disease. Sham-inoculated swine and VR-2332-infected swine did not show any obvious signs of PRRSV infection. Swine were bled and weighed at selected time-points. Swine were monitored for several key disease indicators and all suggested that the Chinese strain resulted in exacerbated disease when compared to the US prototype strain, contrary to our hypothesis. All clinical results will be disclosed at the time of presentation. We compared viral load in serum and lung lavage for each PRRSV strain. We found that rJXwn06-infected swine had approximately 100 fold higher viral peak loads than VR-2332-infected swine, an indication that infection with rJXwn06 replicated with increased kinetics. In vitro growth kinetics and plaque morphology suggested similar findings. When the genomes were aligned, the key polymerase domains [nonstructural proteins (nsp) 9-12, 8757 bases] were quite conserved (95.3% nucleotide identity) whereas the nsp2 domain (3588 bases) was much less conserved (83.1% nucleotide identity). Nsp2 codes for a replicase protein that contains a N-terminal conserved papain-like protease domain, an extended region that varies between strains in sequence and length followed by a conserved transmembrane-spanning region near the C-terminus. We have shown previously that the nsp2 protein is present as various isomers in infected cells, possibly related to its apparent deubiquitinating activity, and associates with host heat shock 70kDa protein 5 (HSPA5, GRP-78, BiP).