Senecavirus A (SVA) is a small, non-enveloped picornavirus that was first discovered in 2002 as a cell culture contaminant. It belongs to the family Picornaviridae, which also includes foot-and-mouth disease virus (FMDV) and swine vesicular disease virus (SVDV). As a highly contagious virus, SVA can infect a wide range of animals, including pigs, cattle, and even humans, posing a significant threat to global food security and animal welfare.
At the core of SVA is a single-stranded, positive-sense RNA genome, encapsulated within a non-enveloped, icosahedral capsid. This unique structure, comprising 60 protomeric units, serves as the virus's protective shell, shielding its genetic material from the host's immune defenses. The capsid's intricate arrangement of proteins, including the VP1, VP2, VP3, and VP4 subunits, not only dictates the virus's shape but also plays a crucial role in its ability to attach to and infect host cells.
The Senecavirus A genome, approximately 7.2 kilobases in length, is meticulously organized to facilitate efficient viral replication. The genome is divided into three distinct regions: the 5' untranslated region (UTR), the open reading frame (ORF), and the 3' UTR. The 5' UTR contains crucial regulatory elements that control the initiation of viral protein synthesis, while the ORF encodes a single polyprotein precursor that is subsequently cleaved into the various structural and non-structural proteins necessary for viral propagation. The 3' UTR, on the other hand, plays a vital role in the packaging and release of newly formed viral particles.
Figure 1. Schematic diagram of SVA structure and genome organization.
(Source: Luo, D. et al., 2022)
The genomic regions P2 and P3 of Senecavirus A (SVA) encode various nonstructural polypeptides involved in protein processing and viral replication. The P2 region consists of 2A, 2B, and 2C proteins. The 2A protein has a unique ribosome-skipping function, while the 2B protein exhibits a different primary sequence but similar secondary structures to other picornaviruses, potentially enhancing membrane permeability. The 2C protein acts as a helicase-like enzyme involved in RNA synthesis.
In the P3 region, there are 3A, 3B, 3C, and 3D polypeptides. The 3B region encodes the VPg protein, which acts as a primer for viral RNA synthesis. The 3C polypeptide functions as a proteinase, while the 3D polypeptide is the primary component of RNA-dependent RNA polymerase. The 3C and 3D sequences of SVA share conserved active-site residues and amino acid motifs with other picornaviruses.
SVA causes vesicular disease and epidemic transient neonatal losses (ETNL) in swine worldwide. The clinical signs of SVA infection are similar to other high-consequence vesicular diseases in swine, such as foot-and-mouth disease, vesicular stomatitis, swine vesicular disease, and vesicular exanthema of swine. These diseases have significant economic implications due to trade restrictions.
SVA infection in swine starts after a short incubation period of 3-5 days. Infected animals initially show mild signs like lethargy and lameness, followed by the development of vesicles on the snout and/or feet. These vesicles rupture within 2-4 days, leaving ulcerated skin lesions that heal by days 14-16. A short-term viremia is detected between days 3-10, which decreases as neutralizing antibodies and CD4+ T-cells increase. Infected animals can shed the virus in oral and nasal secretions and feces for up to 21-28 days. The disease resolves with the development of SVA-specific CD8+ T-cells.
To diagnose SVA, clinical assessment alone is not sufficient as vesicular lesions are similar to other swine vesicular diseases. Direct detection methods such as virus isolation and RNA detection, as well as indirect methods like antibody detection, are necessary.
Fluid from fresh vesicles is the preferred specimen for virus isolation and PCR in diagnosing SVA. Ruptured and dried vesicles with prolonged exposure may result in false negatives. In situ detection methods, such as immunohistochemistry (IHC) or in situ hybridization (ISH), directly identify viral antigens or genetic material. Skin biopsies from the edges of ruptured vesicles are also useful for IHC or ISH. Antibody detection methods include immunofluorescence assay (IFA), competitive enzyme-linked immunosorbent assays (cELISAs), and indirect ELISAs targeting various viral proteins. To diagnose SVA serologically, paired samples from affected animals at two-week intervals are sufficient. Single samples are not enough to assess acute exposure, but they can indicate the virus's presence on the farm.
Oncolytic viruses (OVs) selectively kill tumor cells and stimulate protective immunity, making them a promising approach for cancer immunotherapy. SVA has shown oncolytic potential and can penetrate solid tumors through the bloodstream. SVA is a suitable model due to its inability to integrate into human DNA and lack of viral oncogenes. Genetic engineering of SVA allows the creation of recombinant viruses with enhanced safety and effectiveness for therapeutic use. In addition, the combination of SVA and other treatment methods can greatly enhance the efficacy of OV, thereby beneficially regulating the immune pattern of tumors. Understanding the exact mechanism of the interaction between SVA and the host immune system will help discover better anti-tumor immune strategies.
Reference
| Target | Cat. No. | Product Name | Expression System | Tag/Conjugate | Application | |
| SVA | DAG-WT1130 | Inactivated Seneca Valley virus (SVV) | N/A | N/A | Immunoassays | Inquiry |
| FMDV | DAG-WT1347 | Recombinant FMDV Type A Antigen | E. coli | His | ELISA, LFIA | Inquiry |
| DAG-WT804 | Recombinant FMDV 3ABC Polyprotein | E. coli | TBD | Immunoassays | Inquiry | |
| DAG-WT805 | Recombinant FMDV Type O VP1 Antigen | E. coli | TBD | Immunoassays | Inquiry |
