H5N6 highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4 not only exhibits unprecedented intercontinental spread in poultry, but can also cause serious infection in humans, posing a public health threat. Phylogenetic analyses show that 40% (8/20) of H5N6 viruses that infected humans carried H9N2 virus-derived internal genes. However, the precise contribution of H9N2 virus-derived internal genes to H5N6 virus infection in humans is unclear. Here, we report on the functional contribution of the H9N2 virus-derived matrix protein 1 (M1) to enhanced H5N6 virus replication capacity in mammalian cells. Unlike H5N1 virus-derived M1 protein, H9N2 virus-derived M1 protein showed high binding affinity for H5N6 hemagglutinin (HA) protein and increased viral progeny particle release in different mammalian cell lines. Human host factor, G protein subunit beta 1 (GNB1), exhibited strong binding to H9N2 virus-derived M1 protein to facilitate M1 transport to budding sites at the cell membrane. GNB1 knockdown inhibited the interaction between H9N2 virus-derived M1 and HA protein, and reduced influenza virus-like particles (VLPs) release. Our findings indicate that H9N2 virus-derived M1 protein promotes avian H5N6 influenza virus release from mammalian, in particular human cells, which could be a major viral factor for H5N6 virus cross-species infection.

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.

Classical swine fever (CSF) is a highly contagious and lethal disease caused by classical swine fever virus (CSFV), and it is also a notifiable disease according to the World Organization for Animal Health. Owing to the continuous growth of the international trade in pigs and pig products, pig farming has become the pillar industry of the global livestock industry and is the most important source of animal protein for mankind. As a single-stranded RNA virus, CSFV can avoid being recognized and cleared by the host immune system through a variety of immune evasion strategies so that it persists in the host body and causes multisystemic pathology. CSF has also become one of the most serious infectious diseases affecting the pig industry, resulting in considerable economic losses to the pig industry. Therefore, understanding the main immune evasion mechanism of CSFV is very important for the prevention and control of CSF infection. This article reviews the main immune evasion mechanisms of CSFV, including the suppression of nonspecific immune responses; evasion of adaptive immune responses; and the regulation of host cell apoptosis and cell autophagy. CSFV affects type I interferon regulatory signals; the JAK-STAT signaling pathway; the RIG-I and NF-κB signaling pathways; immune cell function; the mitochondrial apoptosis pathway; and the endoplasmic reticulum stress apoptosis pathway; the PI3K-Akt signaling mediated AMPK-mTOR macroautophagy pathway through its structural proteins E^rns and E1 and E2; and the nonstructural proteins N^pro, NS4B, and NS5A to achieve immune evasion. As our understanding of CSFV immune strategies continues to deepen, we believe that this understanding will provide new strategies for the development of new vaccines and novel diagnostic methods in the future.

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.

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 injure the pork product 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 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, NF-κB, JAK/STAT, apoptosis, and other modulation. The aim is to summarize the dynamic process during the ASFV infection and entry into host cell, provide a rational insight into development of vaccine and a better clear knowledge of how ASFV impacts host.

Classical swine fever (CSF), caused by the classical swine fever virus (CSFV), is an acute, febrile, and highly contagious disease that has led to significant economic losses in the global swine industry. Although the attenuated lapinized CSF vaccine (C-strain) has effectively controlled CSF outbreaks in China since the 1950s, it remains challenging to serologically differentiate infected from vaccinated animals (DIVA). Currently, the application of E2 subunit vaccines allows for DIVA by detecting antibodies against the E^rns protein. Therefore, this study aimed to develop a blocking ELISA for CSFV E^rns antibody detection using porcine monoclonal antibodies (mAbs) derived from single B cell technology. Peripheral blood mononuclear cells (PBMCs) were isolated from immunized pigs, and single CD21⁺IgM⁻E^rns-His tag⁺ B cells were sorted via flow cytometry. Using one-step PCR, full-length genes of porcine IgG heavy and light chains were amplified separately, yielding 11 porcine mAbs against the CSFV E^rns protein. Among these, three mAbs (E0S3, E0S5, and E0S10) exhibited broad reactivity, while two (E0S1, E0S4) showed no cross-reaction with bovine viral diarrhea virus (BVDV). Using mAb E0S4 as the blocking antibody, a blocking ELISA was established and optimized. The assay demonstrated a detection limit of 1:128, no cross-reactivity with other swine viruses or BVDV, and intra- and inter-assay coefficients of variation below 10%. ROC curve analysis determined an optimal cut-off value of 48.4%, with high sensitivity and specificity. In conclusion, the developed blocking ELISA provides a reliable tool for high-throughput serological surveillance, facilitating the DIVA strategy and contributing to CSF eradication programs.