Characterization of two novel porcine reproductive and respiratory syndrome virus isolates with deletions in the GP2 gene

Two newly emerged, porcine reproductive and respiratory syndrome virus (PRRSV) strains (Henan-A10 and A11) were isolated from the sera of aborting sows. Interestingly, both of the isolates could replicate in primary porcine alveolar macrophage (PAM) cells but not in MARC-145 cells. A phylogenetic tree based on the complete genome was constructed and the results showed that Henan-A10 and A11 were most closely related to other highly pathogenic PRRSV (HP-PRRSV) strains. However, genomic sequence analysis showed that Henan-A10 and A11 shared only 96.8-97.8% nucleotide identity with the representative HP-PRRSV strain JXA1. Notably, a 10 amino acids deletion in the GP2 endodomain was identified for the first time. A full-length, infectious cDNA clone of HuN4-F112 (attenuated strain from a HP-PRRSV) was used to construct a chimeric clone with the corresponding deletion in GP2. We found that the deletion did not affect viral growth in MARC-145 cells, indicating that the endodomain of PRRSV GP2 may be variable.