Recent Progress in Studies of Porcine Reproductive and Respiratory Syndrome Virus 1 in China

Abstract

Due to the high incidence of PRRSV mutation and recombination, PRRSV infection is difficult to prevent and control in China and worldwide. Two species of PRRSV, Betaarterivirus suid 1 (PRRSV-1) and Betaarterivirus suid 2 (PRRSV-2), exist in China, and PRRSV-1 has always received less attention in China. However, the number of PRRSV-1 strains detected in China has increased recently. To date, PRRSV-1 has spread to more than 23 regions in China. Based on the phylogenetic analysis of ORF5 and the whole genome of PRRSV-1, Chinese PRRSV-1 can be divided into at least seven independent subgroups. Among them, BJEU06-1-like has become the mainstream subgroup in some regions of China. This subgroup of strains has a 5-aa (4 + 1) characteristic discontinuous deletion pattern at aa 357~aa 360 and aa 411 in Nsp2. Previous studies have indicated that the pathogenicity of PRRSV-1 in China is mild, but recent studies found that the pathogenicity of PRRSV-1 was enhanced in China. Therefore, the emergence of PRRSV-1 deserves attention, and the prevention and control of PRRSV-1 infection in China should be strengthened. PRRSV infection is usually prevented and controlled by a combination of virus monitoring, biosafety restrictions, herd management measures and vaccination. However, the use of PRRSV-1 vaccines is currently banned in China. Thus, we should strengthen the monitoring of PRRSV-1 and the biosafety management of pig herds in China. In this review, we summarize the prevalence of PRRSV-1 in China and clarify the genomic characteristics, pathogenicity, vaccine status, and prevention and control management system of PRRSV-1 in China. Consequently, the purpose of this review is to provide a basis for further development of prevention and control measures for PRRSV-1.

Keywords: PRRSV-1; classification and genomic characteristics; emergence and prevalence; pathogenicity; vaccines and prevention and control.

Figure 1

Map of the PRRSV genome [18].

Figure 2

Regions where PRRSV-1 had been detected in China as of March 2023 have been marked with yellow. Map was obtained from https://axhub.im/maps/ (accessed on 19 June 2023).

Figure 3

Phylogenetic analysis of the nucleotide sequences of ORF5 and the whole genome of PRRSV-1 strains were performed by using the neighbor-joining method in MEGA 7.0. with 1000 bootstrap replicates for each node. Chinese PRRSV-1 isolates belong to subtype 1 and can be divided into four subgroups (Amervac-like, BJEU06-1-like, HKEU16-like and NMEU09-1-like) and form three new subgroups. (A) Phylogenetic analysis of the nucleotide sequences of ORF5 of PRRSV-1 strains. (B) Phylogenetic analysis of the nucleotide sequences of the whole genome of PRRSV-1 strains. Chinese PRRSV-1 strains are labeled with red triangles (▲). Chinese PRRSV-1 strains isolated after 2018 are shown in red.

Figure 4

The distribution of each subgroup in China. (A) The distribution of BJEU06-1-like strains have been marked with blue. (B) The distribution of NMEU09-1-like strains have been marked with red. (C) The distribution of HKEU16-like strains has been marked with purple. (D) The distribution of Amervac-like strains have been marked with green. (E) The distribution of strains forming new subgroups have been marked with pink. Maps were obtained from https://axhub.im/maps/ (accessed on 19 June 2023).

Figure 5

Alignment of the partial Nsp2 protein aa sequences of Chinese PRRSV-1 strains. Purple indicates the characteristic BJEU06-1-like PRRSV-1 5-aa (4  +  1) discontinuous deletion. Yellow indicates the characteristic HKEU16-like PRRSV-1 4 aa continuous deletion (except HKEU16). Red indicates the characteristic SC-2020-1 2-aa (1  +  1) discontinuous deletion. Chinese PRRSV-1 is indicated with a red triangle.

Figure 6

Alignment of GP3 and GP4 protein aa sequences of Chinese PRRSV-1 strains. (A) Alignment of the partial ORF3 aa sequences of Chinese PRRSV-1 strains. (B) Alignment of the partial ORF4 aa sequences of Chinese PRRSV-1 strains. The aa deletion regions are shown in blue or yellow. Termination codons are indicated by an asterisk (*). The C-terminal truncation mutants are shaded in red. Chinese PRRSV-1 is indicated with a red triangle.