Porcine reproductive and respiratory syndrome virus 2 (PRRSV-2) genetic diversity and occurrence of wild type and vaccine-like strains in the United States swine industry

Abstract

Porcine reproductive and respiratory syndrome virus genotype 2 (PRRSV-2) genetic diversity in the U.S. was assessed using a database comprising 10 years’ worth of sequence data obtained from swine production systems routine monitoring and outbreak investigations. A total of 26,831 ORF5 PRRSV-2 sequences from 34 production systems were included in this analysis. Within group mean genetic distance (i.e. mean proportion of nucleotide differences within ORF5) per year according to herd type was calculated for all PRRSV-2 sequences. The percent nucleotide difference between each sequence and the ORF5 sequences from four commercially available PRRSV-2 vaccines (Ingelvac PRRS MLV, Ingelvac PRRS ATP, Fostera PRRS, and Prevacent PRRS) within the same lineage over time was used to classify sequences in wild-type or vaccine-like. The mean ORF5 genetic distance fluctuated from 0.09 to 0.13, being generally smaller in years in which there was a relative higher frequency of dominant lineage. Vaccine-like sequences comprised about one fourth of sequences obtained through routine monitoring of PRRS. We found that lineage 5 sequences were mostly Ingelvac PRRS MLV-like. Lineage 8 sequences up to 2011 were 62.9% Ingelvac PRRS ATP-like while the remaining were wild-type viruses. From 2012 onwards, 51.9% of lineage 8 sequences were Ingelvac PRRS ATP-like, 45.0% were Fostera PRRS-like, and only 3.2% were wild-type. For lineage 1 sequences, 0.1% and 1.7% of the sequences were Prevacent PRRS-like in 2009–2018 and 2019, respectively. These results suggest that repeated introductions of vaccine-like viruses through use of modified live vaccines might decrease within-lineage viral diversity as vaccine-like strains become more prevalent. Overall, this compilation of private data from routine monitoring provides valuable information on PRRSV viral diversity.

Combined Subcutaneous-Intranasal Immunization With Epitope-Based Antigens Elicits Binding and Neutralizing Antibody Responses in Serum and Mucosae Against PRRSV-2 and SARS-CoV-2

“…Most licensed mucosal vaccines are currently based on live-attenuated whole-microorganisms, as those are the most immunogenic formulations to prevent infectious diseases ( 18 , 90 – 93 ). Nevertheless, antigenically variable and highly transmissible pathogens such as PRRSV-2 and SARS-CoV-2 are not entirely suitable to be targeted by these immunogens, as a reversion to virulence may occur ( 94 , 95 ). To avoid this problem, cutting-edge platforms and antigen-discovery approaches developed for parenteral vaccines might be tried for mucosal immunization, including computational epitope-based immunogen design ( 96 , 97 ).…”

“…Mucosal immunization against PRRSV-2 and SARS-CoV-2 has already been reported utilizing different platforms ( 14 , 89 , 102 ). For PRRSV-2, intranasal and parenteral live-attenuated vaccines have been evaluated, with the risk of mucosal shedding and reversion to virulence ( 95 , 103 , 104 ). Besides, experimental mucosal immunogens based on recombinant proteins, VLPs, or viral vectors have targeted PRRSV-2 surface glycoproteins, with the disadvantage of including decoy epitopes and glycan shields ( 30 , 32 ).…”

A novel amino acid site of N protein could affect the PRRSV-2 replication by regulating the viral RNA transcription

“…PRRSV is a positive-sense RNA virus and belongs to the Arterivirus family; the genome is approximately 15 kb [ 3 ]. Based on their genetic diversity, PRRSVs can be divided into PRRSV-1 (European strains) and PRRSV-2 (North American strains) [ 4 ]. Due to the high variability of the PRRSV nucleotide sequences, PRRSVs can be further classified into nine lineages [ 5 ].…”

“…However, the mechanism of its diminished virulence has not been elucidated. Many studies have suggested that this method of reducing virulence is unstable and carries some risks [ 4 , 11 ]. Due to the highly mutable nature of the PRRSVs, improving safety is one of the primary goals of PRRSV vaccines [ 10 ].…”

Molecular Evolution of Porcine Reproductive and Respiratory Syndrome Virus Field Strains from Two Swine Production Systems in the Midwestern United States from 2001 to 2020

“…Additionally, a greater degree of genetic variation exists within each species ( 9 ). So far, PRRSV-2 has been classified into nine distinct lineages based on a comprehensive study of ORF5 sequences, and most of them were identified among swine herds in the United States ( 10 – 13 ). PRRSV-2 genome contains 10 open reading frames (ORF): 1a, 1b, 2a, 2b, 3, 4, 5, 5a, 6, and 7 ( 14 – 16 ).…”