Untangling lineage introductions, persistence and transmission drivers of HP-PRRSV sublineage 8.7

Host-similar fragments in the African swine fever virus genome: distribution, functions, and evolution

African swine fever virus (ASFV) predominantly infects Argasidae and suids, resulting in high morbidity and mortality in pigs. Despite the crucial role that viral sequences resembling those of the host play in the virus's survival, there are limited comprehensive studies on the genomic similarities between ASFV and its hosts. Consequently, this study employs homology analysis to construct a similarity network between ASFV and its hosts (Argasidae and suids), investigating the distribution, function, evolution, and origins of these similar sequences in ASFV. Our findings indicate that the host-similar fragments are mainly distributed between positions 70000 and 180000 of the ASFV genome, primarily within non-coding regions. Notably, these non-coding fragments are often associated with promoter functions. Furthermore, the analysis of suid proteins that share similarities with ASFV proteins reveals that they predominantly exhibit RNA polymerase activity and are involved in metabolic processes. Evolutionary analysis indicates that pan-similar sequences of ASFV exist in an open state, highlighting the diversity of these analogous sequences. Additionally, a positive correlation was identified between the occurrence of recombination breakpoints and similar sequences, indicating that homologous recombination may serve as a crucial mechanism driving the formation of these analogous sequences.

Ten years after introduction of NADC30-like strain in China: a novel chimeric porcine reproductive and respiratory syndrome vaccine candidate

Introduction

Porcine reproductive and respiratory syndrome (PRRS), caused by the PRRS virus (PRRSV), is an economically significant swine disease with extensive strain variation and limited heterologous protection. Modified live virus (MLV) vaccines developed by serially passaging the virus in monkey kidney cell lines have been widely used for more than 20 years. Lineage 1 virus, such as NADC30-like in China and L1C 1-4-4 strains in the United States, have gradually become the predominant strain or the dominant recombination isolate donor strain in recent years. MLVs licensed for use in the market supply low efficacy of heterologous protection ability against the NADC30-like strain, and a vaccine with improved safety and efficacy is therefore required. The method of virulence attenuation used for classical strains may not be applicable to the development of a vaccine against NADC30-like strains due to their low fidelity of replication.

Methods

Chimeric RvBJ-4-(ORF2-4)SX, RvBJ-4-(ORF5-6)SX, and RvBJ-4-(ORF2-6)SX were constructed by substituting minor structural proteins (GP2, GP3, and GP4), major structural proteins (GP5 and M) or both in NADC30-like CHsx1401 to classical strain backbone BJ-4. RvBJ-4-(ORF2-6)SX. Animal trials were conducted to assess the pathogenicity and protection of chimeric viruses.

Results and Discussion

Chimeric virus RvBJ-4-(ORF2-6)SX demonstrates a favorable balance between safety and efficacy, with limited pathogenicity and providing faster viremia clearance as well as reduced lung lesions in vaccinated/challenged pigs. A novel strategy for providing safe and effective immunological protection against NADC30-like strains has been introduced, with the potential for implementation in the field.

Antiviral effects and mechanism of Ma-Xing-Shi-Gan-San on porcine reproductive and respiratory syndrome virus

Background

Currently, vaccination has consistently posed challenges in preventing the Porcine reproductive and respiratory syndrome virus (PRRSV), so there is an urgent need for effective controlling strategies. Ma-Xing-Shi-Gan-San (MXSGS), a traditional Chinese medicine (TCM) formula used for pulmonary diseases and respiratory disorders, has proven effective in treating H1N1 and COVID-19. Herein, we evaluated whether MXSGS exhibits potent antiviral activity against PRRSV.

Methods

First, a PRRSV-infected Marc-145 cell model was established. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and the tissue culture infective dose (TCID₅₀) assay were performed to assess the inhibitory effects of MXSGS on PRRSV during different administration stages. Network pharmacology was then employed to identify key active ingredients and core potential targets of MXSGS against PRRSV. In addition, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted to elucidate the antiviral signaling pathways modulated by MXSGS. Lastly, candidate ingredients and targets were validated by molecular docking analysis.

Results

MXSGS significantly inhibited PRRSV through prophylactic and therapeutic administration and suppressed multiple phases of the viral life cycle, including attachment, internalization, replication, and release. In network pharmacology results, 82 active ingredients and 118 therapeutic targets related to MXSGS and PRRSV were identified. Among them, Calycosin, Odoratin, Glyzaglabrin, 7,2',4'-trihydroxy-5-methoxy-3-arylcoumarin, and Eriodictyol were selected as key active ingredients. ALB, PPARG, CASP3, STAT3, TGFB1, JAK2, TLR4, PRKACA, and PRKACB were screened as potential core targets. Furthermore, pathway and functional enrichment analysis revealed that the impact of MXSGS on PRRSV mainly involved Toll-like receptor signaling pathway, typical NF-κB signaling, positive regulation of interleukin-6 production, Th17 cell differentiation, inflammatory response, and viral defense response. Lastly, molecular docking analysis indicated an excellent binding affinity between the core potential targets and key active ingredients, with all binding energies < -6.0 kcal/mol.

Conclusion

In vitro experiments indicated that MXSGS exhibited considerable anti-PRRSV activity. Using network pharmacology and molecular docking approaches, five key active ingredients and six core potential targets were identified, underscoring MXSGS as a promising pharmaceutical agent for controlling PRRSV.

Genome and Pathogenicity Analysis of an NADC30-like PRRSV Strain in China's Xinjiang Province

The porcine reproductive and respiratory syndrome virus (PRRSV) possesses an inherent ability to adapt to environmental transformations and undergo evolutionary changes, which has imposed significant economic pressure on the global pig industry. Given the potential for recombination among PRRSV genomes and variations in pathogenicity, newly emerging PRRSV isolates are of considerable clinical importance. In this study, we successfully isolated a novel strain named XJ-Z5 from PRRSV-positive samples collected in Xinjiang province in 2022. Through comprehensive genomic sequencing, phylogenetic analysis, and recombination analysis, we confirmed that this strain belongs to the NADC30-like recombinant PRRSV. During pathogenicity tests in piglets, this strain exhibited moderate virulence, causing symptoms such as reduced appetite, persistent fever, and weight loss; however, no mortality cases were observed. Tests conducted at various time points detected the presence of PRRSV nucleic acid in nasal swabs, rectal swabs, tissue samples, and blood, with the highest viral loads found in lung tissue and blood. Serum biochemical tests indicated significant impairment of liver and kidney function. PRRSV antibodies began to appear gradually after 10 days post infection. Hematoxylin and eosin staining revealed substantial pathological changes in lung tissue and lymph nodes. This study enhances our understanding of the epidemiology of PRRSV and underscores the importance of ongoing monitoring and research in light of the challenges posed by the continuous evolution of viral strains. Furthermore, the research emphasizes the urgency of the rapid genomic analysis of emerging viral strains. Through these comprehensive research and monitoring strategies, we aimed to curb the spread of PRRSV more effectively and thus reduce the huge economic losses it caused to the pig industry.

Development of SYBR green I-based real-time qPCR differential diagnosis assays for porcine reproductive and respiratory syndrome virus typing in Guangdong province

Introduction

Porcine Reproductive and Respiratory Syndrome (PRRS) is a highly contagious disease that causes reproductive disorders in sows and respiratory problems in pigs of different ages. It first appeared in the late 20th century in the United States and Europe before spreading globally, leading to significant economic losses in the swine industry. Porcine Reproductive and Respiratory Syndrome virus (PRRSV) has a high rate of genetic recombination, resulting in considerable genetic diversity within the virus. The lack of cross-protection between different lineages often leads to unsuccessful vaccination attempts.

Methods

To accurately distinguish PRRSV lineages and develop effective vaccination strategies for pigs, we have developed a fluorescence quantitative PCR (qPCR) method by designing specific primers and SYBR green dye. This method allows for the simultaneous identification of different PRRSV genotypes.

Results

Our experimental results show that these methods have good specificity and do not react with other common viral pathogens in pigs. This method also demonstrates good sensitivity, with the ability to detect low levels of the virus. The detection limits of these assay were 102 copies/μL for PRRSV-1 (European-type PRRS) and 101 copies/μL for PRRSV-2 (American-type PRRSV), HP-PRRSV (Highly Pathogenic PRRSV), and NL-PRRSV (NADC30-like PRRSV), respectively. Furthermore, the reproducibility of this method is commendable, with intra- and inter-assay coefficients of variation remaining below 3%. In the subsequent study, a total of 316 clinical samples of porcine with respiratory and reproductive failure symptoms were collected from 14 cities in Guangdong. The results showed that among these samples, 22.78% (72 out of 316) tested positive for PRRSV-2, 15.51% (49 out of 316) tested positive for HP-PRRSV, and 0.95% (3 out of 316) tested positive for NL-PRRSV. However, PRRSV-1 was not detected in any of the samples.

Discussion

Our method provides a quick way to identify PRRSV genotypes in pig herds in Guangdong, which has certain significance for developing effective vaccination strategies against PRRS.

Recombination and pathogenicity analysis of NADC30-like and QYYZ-like PRRSV strains in South China

Since 2010, the Lineage 1 (NADC30-like) and Lineage 3 (QYYZ-like) strains of PRRSV-2 have become widespread in China, undergoing recombination and resulting in varying virulent and immune-evading mutants that have severely impacted the pig farming industry. In this study, we isolated one NADC30-like strain (GXHX20211106) and one QYYZ-like strain (GXGG202007) from pig serum samples collected in southern China. Comparative genomic analysis revealed that GXHX20211106 shares 90 % identity with NADC30, while GXGG202007 shows 91.4 % similarity to QYYZ. Both strains exhibit characteristic amino acids deletions or insertions in the Nsp2 region. Phylogenetic analyses further classified GXHX20211106 within Lineage 1.8 (NADC30-like) and GXGG202007 in Lineage 3 (QYYZ-like). Recombination analysis demonstrated that GXHX20211106 resulted from recombination between NADC30-like and HP-PRRSV-like strains, while GXGG202007 originated from recombination events involving QYYZ-like, VR-2332-like, and HP-PRRSV-like strains. Pathogenicity studies in piglets indicated that both isolates caused moderate clinical signs, with GXHX20211106 showing higher virulence compared to GXGG202007. No deaths were recorded in the infected piglets. These findings highlight the critical role of recombination in shaping PRRSV virulence and underscore the need for ongoing surveillance and control measures to mitigate the impact of recombinant PRRSV strains in southern China.