Submitted to: Archives of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/1997
Publication Date: N/A
Citation: Interpretive Summary: Porcine reproductive and respiratory syndrome (PRRS) is characterized by reproductive failure in sows and gilts, pneumonia in nursery and young growing pigs, and an increase in preweaning mortality. The causative agent of this disease is the PRRS virus. A modified live PRRS vaccine (Boehringer Ingelheim Animal Health) has been used extensively in the United States to control the disease in recent years. To elucidate changes associated with the attenuated virulence in the modified live PRRS vaccine, a nucleotide sequence from the vaccine virus was determined. Comparisons showed 98 changes between the vaccine virus and its parental virus. Most of these changes were also present in 17 known virulent PRRS virus isolates from North America. However, there were seven unique changes in the vaccine virus which may be responsible for the attenuated virulence in the vaccine virus.
Technical Abstract: To elucidate changes associated with the attenuated virulence in a modified live porcine reproductive and respiratory syndrome (PRRS) vaccine (Boehringer Ingelheim Animal Health, St. Joseph, MO), derived from an American prototype virus ATCC VR-2332, nucleotide sequence of 3' genome covering open reading frames (ORFs) 2 to 7 coding regions from the vaccine virus was determined by RT-PCR with two overlapping fragments. Comparison showed 98 base changes (94 substitutions, 3 deletions, and 1 addition) out of 3318 nucleotides between the vaccine virus and its parental virus. There were 15, 26, 17, 29, 9 and 6 base substitutions in ORFs 2, 3, 4, 5, 6 and 7, respectively, resulting in 5, 13, 8, 13, 2 and 3 amino acid (a.a.) substitutions in their deduced proteins, respectively. Most of these a.a. substitutions were also present in 17 known virulent/wild type PRRS virus isolates from North America. However, there were 1, 4, 1 and 1 unique a.a. .substitutions in the vaccine virus ORFs 2, 3, 4 and 5 deduced proteins, respectively. These unique amino substitutions may be responsible for the attenuated virulence in the vaccine virus.