Foot-and-mouth disease (FMD) is highly contagious and affects the economy of many countries worldwide. Serotype O is the most prevalent and is present in many regions of Asia. Lineages O/SEA/Mya-98, O/Middle East-South Asia (ME-SA)/PanAsia, O/Cathay and O/ME-SA/Ind-2001 have been circulating in Asian countries. Low antigenic matching between O/Cathay strains and current vaccine strains makes the disease difficult to control, therefore, analyzing the molecular evolution, diversity, and host tropisms of FMDV Serotype O in Asia may be helpful. Our results indicate that Cathay, ME-SA, and SEA are the predominant topotypes of FMDV serotype O circulating in Asia in recent years. Cathay topotype FMDV evolves at a higher rate compared with ME-SA and SEA topotypes. From 2011 onwards, the genetic diversity of the Cathay topotype has increased substantially, while large reductions were found in the genetic diversity of both ME-SA and SEA topotypes, suggesting a trend that infections sustained by the Cathay topotype were becoming a more severe epidemic in recent years. Analyzing the distributions of host species through time in the dataset, we found that the O/Cathay topotype was characterized by a highly swine-adapted tropism in contrast with a distinct host preference for O/ME-SA. The O/SEA topotype strains identified in Asia were isolated mainly from cattle until 2010. It is worth noting that there may be a fine-tuned tropism of the SEA topotype viruses for host species. To further explore the potential molecular mechanism of host tropism divergence, we analyzed the distribution of structure variations on the whole genome. Our findings suggest that deletions in the PK region may reflect a common pattern of altering the host range of serotype O FMDVs. In addition, the divergence of host tropism may be due to accumulated structural variations across the viral genome, rather than a single indel mutation.

African swine fever virus (ASFV), a highly contagious pathogen characterized by a complex structure and a variety of immunosuppression proteins, causes hemorrhagic, acute, and aggressive infectious disease that severely injures the pork products and industry. However, there is no effective vaccine or treatment. The main reasons are not only the complex mechanisms that lead to immunosuppression but also the unknown functions of various proteins. This review summarizes the interaction between ASFV and the host immune system, along with the involvement of virulence-related genes and proteins, as well as the corresponding molecular mechanism of immunosuppression of ASFV, encompassing pathways such as cGAS-STING, nuclear factor kappa–light-chain-enhancer of activated B cells (NF-κB), Janus Kinase (JAK) and JAK Signal Transducers and Activators of Transcription (STAT), apoptosis, and other modulation. The aim is to summarize the dynamic process during ASFV infection and entry into the host cell, provide a rational insight into development of a vaccine, and provide a better clear knowledge of how ASFV impacts the host.

Single B-cell antibody generation technology is an advanced method that offers several advantages, including rapid production, high efficiency, and high yield. The antibodies generated via this technique retain their natural conformation and are well suited for applications in pathogen diagnosis, disease treatment, and investigations of virus cross-species transmission mechanisms. Our study aimed to establish a platform for generating single B-cell antibodies specifically targeting the foot-and-mouth disease virus (FMDV) 146S antigen in mice. Female BALB/c mice were immunized with inactivated O-type FMDV 146S antigen, and spleen cells were collected for further analysis. Flow cytometric sorting was performed using a biotin-labeled O-type FMDV 146S antigen as a decoy to identify and select CD19 + /CD21/35 + /CD43-/IgM-/Biotin + antigen-specific individual B cells. The gene sequences encoding the variable regions of the heavy and light chains of the murine IgG antibodies were obtained via single-cell nested PCR amplification. Separate constructs were created for the heavy and light chain plasmids to ensure the proper expression of intact IgG antibodies. These plasmids were cotransfected into human embryonic kidney 293T (HEK293T) cells, leading to the successful production and purification of 15 specific monoclonal antibodies (mAbs), 10 which exhibited activity in ELISA tests, and six antibodies that displayed activity in IFA tests. These findings highlight the successful development of a method for generating mouse-derived single B-cell antibodies that target FMDV. This achievement provides a solid foundation for diagnostic techniques and the analysis of antigenic structural variations.

(1) Background: Contagious ecthyma, also known as orf, is an epitheliotropic zoonotic disease caused by the orf virus (ORFV), primarily affecting the skin and mucous membranes of ruminants such as goats and sheep, leading to the formation of papules and pustules. Vaccination is the most effective way to prevent this disease in susceptible animals; however, traditional attenuated vaccines carry the potential risk of reversion to virulence. Therefore, there is an urgent need to develop safe and effective vaccines for the prevention and control of orf. (2) Methods: In this study, building upon the previously constructed ORFV three-gene deletion strain rGS14-TrypMut, we employed homologous recombination to knock out the VIL-10 gene and successfully constructed a four-gene deletion strain, rGS14-QuadMut. We evaluated its in vitro growth characteristics, safety, and protective efficacy in a challenge model. (3) Results: The in vitro results show that rGS14-QuadMut had a replication ability similar to that of other two-gene deletion strains, with good genetic stability. In in vivo experiments, compared to rGS14-TrypMut, rGS14-QuadMut caused only mild redness and swelling at the inoculation site, with a faster healing rate, indicating better safety. Additionally, rGS14-QuadMut induced strong differentiation of CD4⁺ and CD8⁺ T cells, increased the CD4⁺/CD8⁺ ratio, and primarily stimulated a Th1-type immune response, with significant changes in cytokine levels, including IL-8, IFN-γ, and IL-2. In the challenge protection experiment, both rGS14-QuadMut and rGS14-TrypMut provided 100% protective efficacy. In conclusion, rGS14-QuadMut demonstrated enhanced safety without compromising immune protection efficacy and is a promising candidate for an orf live vaccine strain.

African swine fever (ASF) is a highly pathogenic and hemorrhagic swine infectious disease caused by the African swine fever virus (ASFV). It encodes over 150 proteins, among which the CD2v protein plays multiple roles throughout the infection process. Single B-cell antibody technology is a cutting-edge method for preparing monoclonal antibodies (mAbs), which has the advantages of rapid, efficient, and high yield in antibody production, while possessing natural conformations. In this study, by cloning and expressing antibody genes in vitro, 14 murine-derived mAbs were prepared using recombinant CD2v proteins as immunogenic sources, which brings sufficient enrichment and selectivity for the development of antibodies based on the single B-cell antibody technique. All 14 mAbs demonstrated reactivity with CD2v protein by indirect ELISA, whereas 8 mAbs successfully detected CD2v in ASFV-infected PAM cells by IFA, indicating the tested mAbs can effectively recognize and bind to ASFV CD2v. Finally, a blocking ELISA method for detecting CD2v antibodies using CD2v mAb C89 was established, which holds significant potential for broad application in the serological diagnosis of ASFV with determination of the CD2v-blocking ELISA specificity, sensitivity, reproducibility, and compliance rate. It could be used for the rapid clinical detection of ASFV CD2v protein to provide a powerful tool for the monitoring of epidemics.

Background/Objectives: African swine fever (ASF) causes massive global swine industry losses with no effective vaccine available. This study constructed T7 phages displaying key ASFV proteins to evaluate their potential as an ASF vaccine by assessing viral shedding and immune responses in pigs. Methods: Five ASFV proteins were displayed on T7 phages to form VLPs (ASFV-SC-T7 group), with soluble proteins (ASFV-SC group) and PBS as controls; 9 piglets were immunized, boosted at 28 days, challenged with virulent ASFV, and assessed via ELISA, flow cytometry, and real-time PCR. Results: ASFV-SC-T7 induced more high-titer antibodies and elevated monocytes/CD8⁺ T cells, but all groups developed ASF lesions, with ASFV-SC-T7 having higher lung/mesenteric lymph node viral loads and no survival improvement (only delayed fever). Conclusions: T7 phage-displayed ASFV proteins activate strong immunity, confirming T7 phages as a viable delivery platform, but failed to protect against virulent ASFV, requiring future optimization of antigens and regimens.