Complete Genome Sequence of a Novel Variant Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Strain: Evidence for Recombination between Vaccine and Wild-Type PRRSV Strains

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of porcine reproductive and respiratory syndrome (PRRS), which can evolve continuously by random mutation or intragenic recombination. Here we report the complete genomic sequence of a PRRSV variant with nucleotide acid deletions and insertions in the nonstructural protein 2 (nsp2) gene and a possible recombination event between a modified live virus (MLV) vaccine strain and a prototype Chinese field strain. P orcine reproductive and respiratory syndrome (PRRS) outbreaks occur worldwide and cause significant economic losses in the swine industry (6, 7). Even though modified live virus (MLV) vaccines were shown to provide solid protection against PRRSV infection, there were substantial barriers to the use of MLV vaccines in the field (2, 5). Considering the extensive use of MLV vaccines for preventing and controlling PRRS in mainland China, the appearance of a natural recombination event between a vaccine strain and a field strain is noteworthy.Serum and tissue samples were collected from suspected growing pigs in Guangdong Province in 2011. Infected pigs were about 10 weeks old and displayed symptoms similar to those of original PRRS, including severe respiratory problems, diarrhea, and poor growth. In addition, this disease resulted in a ϳ2.2% mortality rate on this farm. A porcine reproductive and respiratory syndrome virus (PRRSV) field isolate, named GM2, was propagated on Marc-145 cells, and total viral RNA was extracted from the serum and infected cell culture and then used separately for the amplification of the genome. Basically, 16 primer pairs were used to generate overlapping amplicons by reverse transcription-PCR (RT-PCR) as reported previously (8), and 3=-terminal sequences of GM2 were obtained by a 3= rapid amplification of cDNA ends (RACE kit; TaKaRa). The PCR products were cloned into pMD19-T vector (TaKaRa), sequenced three times using an ABI 3730 Sanger-based genetic analyzer, and assembled using DNAStar version 7.0 to obtain the complete genome sequence. The completed sequence showed that, excluding the poly(A) tail, the genomic sequence of GM2 was 15,513 nucleotides in length. Genetic analysis demonstrated that GM2 shared 90.2% genome similarity with VR-2332, but a lower degree of genetic homology (87.7%) was observed than with the representative highly pathogenic PRRSV JXA1 strain. Compared with the VR-2332 strain, 36-amino-acid insertions and two continuous amino acid deletions in the nonstructural protein 2 (nsp2) region of GM2 were found. However, GM2 shared a very low identity with the SP strain (68.8%) and the Japanese strain EDRD-1 (70.5%), which was characterized by similar insertions within nsp2.Recombination events were detected using both Simplot version 3.5.1 (3) and the recombination detection program version 4.1.3 (RDP4) (4). The results indicated that GM2 was a potential recombinant between the MLV RespPRRS/Repro vaccine strain and a recently emerging prototype Chinese field strain, named QYYZ. P...

Recombination of Globally Circulating Varicella-Zoster Virus

“…Recombination between wild-type and attenuated vaccine strains and the putative consequences thereof have been demonstrated and/or discussed for several viruses, such as members of the Flaviviridae family (34)(35)(36), pestiviruses (37), polioviruses (38)(39)(40), avian paramyxovirus-1 (41), myxoma viruses (42), porcine reproductive and respiratory syndrome virus (43), and herpesviruses (15,22,44,45). Recombination between two live herpesvirus vaccine strains was reported for pseudorabies virus, which is an alphaherpesvirus that infects pigs (44).…”

Porcine reproductive and respiratory syndrome (PRRS).Review

“…Field research has also proven that transmitted vaccine viruses may not share the same phenotype as the paternal attenuated strain and that may revert to virulence (10) . Further, natural recombination between the vaccine virus and field virus has been reported (53) .…”

“…The dead virus vaccine used in Europe is Hipra®Suipravac-PRRS in oil emulsion o/w as an adjuvant. It has been observed that the virus of the attenuated virus vaccines is able to replicate, revert to pathogenicity, cause viremia, shed and infect healthy susceptible animals (10,53) , while the inactivated virus vaccine although it does not replicate, nor does it produce viremias, cases of null protection have been reported (24) .…”

Microbiological Identification and Analysis of Swine Lungs Collected from Carcasses in Swine Farms, China

“…Bacteriology was quantified by culture and all bacteriological work, including setup, culture, identification, and typing, was done following standard operating procedures outlined in the manual of clinical microbiology. Testing for virology were carried out according to previously reported protocols [5,7]. All animal research was conducted under the guidance of the Centers for Disease Control and Prevention (CDC)'s Institutional Animal Care and use committee in an association for assessment and accreditation of laboratory animal care International accredited facility.…”

“…Porcine circovirus type 2 is the primary causative agent of porcine circovirus-associated diseases (PCVADs) in pigs and causes significant economic losses in most pig-producing countries. More recently, an outbreak of S. suis infection causing mortality in humans was caused by an emergent, highly virulent strain of S. suis, a pathogen that persists in the lungs of clinically healthy pigs [7,8]. Most infectious diseases are caused by bacteria which proliferate within quorum sensing (QS) mediated biofilms [9,10].…”