Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is the etiologic agent of porcine pleuropneumonia, a severe respiratory disease characterized by hemorrhagic, necrotizing lung lesions that cause significant economic losses on the global swine industry. However, the molecular mechanisms underlying the lung pathogenicity of A. pleuropneumoniae remain unclear. Here we demonstrate that A. pleuropneumoniae infection induces lung injury through activating the NLRP3-mediated inflammatory response mediated by the YadA-like head region (Adh) of Apa1, a bacterial adhesin that mediates attachment to host cells. Importantly, we show that Adh triggers the NLRP3-mediated inflammatory response by engaging olfactory receptor family 5 subfamily M member 11 (OR5M11), a host receptor previously shown to interact with Adh. Furthermore, OR5M11 contributes to the Adh-activated inflammatory response by promoting mitochondrial DNA release. Taken together, our results provide new insights into the pathogenesis of A. pleuropneumoniae, particularly regarding NLRP3-mediated inflammatory pathology.

Mycoplasma hyopneumoniae (Mhp) is the primary etiological agent of porcine enzootic pneumonia and establishes infection through close association with the respiratory ciliated epithelium. Classical models of Mhp colonization have focused mainly on specific interactions between adhesins, particularly P97, and ciliary receptors. Although this framework has provided important insights into ciliary attachment, increasing evidence indicates that Mhp adhesion involves multiple surface proteins and host ligands, including sulfated glycosaminoglycans (GAGs), fibronectin, plasminogen (Plg) and extracellular actin. In this review, we synthesize current evidence and propose a glycocalyx-mediated infectious niche framework for early Mhp colonization. Within this framework, sulfated glycans within the respiratory glycocalyx may contribute to bacterial positioning at the airway interface, while multiligand adhesin interactions may contribute to attachment and Plg-binding surface proteins may facilitate host-factor recruitment. Among these interactions, plasminogen recruitment provides a potential link between adhesion and local interface modification, including possible extracellular matrix remodeling and epithelial injury. Other processes, including potential GAG-mediated local retention, host glycan-dependent variation in attachment and glycocalyx remodeling, remain hypotheses requiring further validation. By distinguishing experimentally supported interactions from mechanistic inferences, this review presents Mhp colonization as a dynamic host-pathogen interface process rather than a simple adhesin-receptor event. This framework provides a basis for future investigation of early colonization mechanisms and anti-adhesion strategies in porcine enzootic pneumonia.

Glässer's disease, caused by Glaesserella parasuis (GPS), causes substantial economic losses in the swine industry worldwide. This situation is largely attributable to the poor cross-protective efficacy of currently available vaccines. In this study, a multi-antigen cocktail subunit vaccine against GPS infection was developed. In silico antigenicity analysis, the immunoprotective efficacy, and antibody titers of 14 GPS antigens were assessed in a murine model. Finally, VacJ, PtsG, and GAPDH were identified as the component of the cocktail vaccine, with Gel-01 as the optimal adjuvant. Immunization of the cocktail vaccine induced robust humoral and cellular immune responses. The vaccine conferred effective cross-protection against lethal-dose GPS4 and GPS5 infections in mice. As supported by a pilot study, it also demonstrated favorable immunoprotective efficacy against GPS infection in piglets. Furthermore, immune sera from vaccinated mice significantly inhibited the growth of GPS4 and GPS5. Overall, these results suggested that the subunit cocktail vaccine established in this study exhibits great potential for preventing GPS infection under experimental conditions, and further large‑scale pig trials are still required to validate its practical applicability in field production.

Brucella is a successful intracellular bacteria, regulating various physiological activities within host cells by secreting multiple virulence factors. However, the specific molecular mechanisms underlying these processes remain unclear. Through interactions with host proteins, Brucella can influence cellular physiological processes to evade immune responses and enhance the bacteria survival and reproductive abilities. The type IV secretion system (T4SS) of Brucella plays a significant role in the process of Brucella infecting cells. This study revealed the interaction between BtpB and YWHAZ (14-3-3ζ) by analyzing the interaction network of 112 host proteins interacting with Brucella effector protein BtpB. Furthermore, we discovered that BtpB regulates the expression of YWHAZ protein and the deletion of its TIR domain abolishes this interaction as well as the effect on YWHAZ protein expression. Moreover, BtpB activates pro-apoptotic markers leading to apoptosis induction in cells. Our results provide mechanistic evidence that BtpB-dependent apoptosis regulation is contingent upon interaction with YWHAZ, and further characterize YWHAZ as a host factor governing Brucella's intracellular survival capacity. This study provides valuable understanding of the immune response mechanism against intracellular bacterial infections in hosts and offers a theoretical basis for future prevention and treatment strategies for Brucellosis.

Pathological changes and viral presence in the bursa of Fabricius (BF) have been reported, but the immunosuppression of infectious bronchitis virus (IBV) remains poorly characterized. Here, we systematically evaluated the pathogenicity of two GI-19 lineage IBV isolates, CK/CH/FJ-B3/2023 (bursal origin) and CK/CH/FJ-T5/2023 (tracheal origin), in 7-day-old specific pathogen-free (SPF) chicks, including further assessments of serum cytokines and the bursal apoptosis. We further assessed the impacts of these two IBV isolates on the Newcastle disease virus (NDV) inactivated vaccine-induced hemagglutination inhibition (HI) antibody response. This study reveals that both GI-19 lineage IBV isolates, which originated from the recombination of the 4/91 vaccine strain, exhibit bursa-tropism, inducing bursal pathological atrophy, prolonged viral detection [up to 35 days post-infection (dpi)] and delayed seroconversion until 14 dpi. Notably, IBV infection induces humoral immunosuppression in SPF chickens, evidenced by a ≥ 1log2 reduction in NDV-HI antibody titers at 14 and 28 dpi, with antibody production recovering to normal levels by 35 dpi. This is accompanied by a sustained systemic proinflammatory response characterized by persistent upregulation of tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), IL-6, and interferon-gamma (IFN-γ) in the serum of infected chicks up to 28 dpi. Early-onset bursal apoptosis was detected as early as 1 dpi, with the bursal apoptosis index significantly higher than that of the negative control throughout the observation period. These findings highlight the humoral immunosuppression induced by IBV variants. Further characterization of IBV types is warranted to elucidate IBV immunosuppressive mechanisms.

Japanese encephalitis virus (JEV), a zoonotic mosquito-transmitted flavivirus, induces human encephalitis and swine reproductive diseases. No antiviral drugs or treatments exist for flavivirus infections, which cause severe symptoms. Even though some host proteins can suppress flavivirus proliferation, the virus can inhibit this antiviral effect. This study identified a host protein SAMSN1 (SAM domain, SH3 domain, and nuclear localization signal 1; also referred to as HACS1, SLY2, and NASH1) having antiviral activity during JEV replication. SAMSN1 was upregulated during JEV infection. The expression of SAMSN1 inhibits JEV replication by binding and degrading JEV-encoded nonstructural proteins (NS1, NS5) through the proteasome and the SAMSN1-TRIM21-p62 autophagy protein degradation pathways. SAMSN1 induced expression of type I interferon through the RIG-I/MyD88-TBK1-IRF3 axis in the JEV infection process. Current findings reveal a novel role of SAMSN1 in inhibiting JEV replication and proliferation, through viral protein degradation and interferon pathway upregulation.

Bovine viral diarrhea virus (BVDV), one of the most important viral pathogens in cattle, causes serious economic losses due to immunosuppression and persistent infections. Previous studies have shown a tight connection between virus infection and lipid metabolism, particularly in the formation and degradation of lipid droplets (LDs). However, the pathogenic mechanism of BVDV infection and the molecular mechanisms by which viral proteins reprogram lipid metabolism remain unclear. We found that BVDV increased cellular LD accumulation by enhancing the production of new lipids, accelerating exogenous fatty acid uptake, and elevating diacylglycerol acyltransferase (DGAT)-dependent esterification of fatty acids (FAs). The generated LDs subsequently release free fatty acids (FFAs) via adipose triglyceride lipase/hormone-sensitive lipase (ATGL/HSL)-dependent lipolysis. This lipolysis-dependent release of FFAs is accelerated and transferred to mitochondria for oxidation by increasing contact between LDs and mitochondria, thereby promoting viral replication. Furthermore, BVDV core protein targets the surface of LDs, increasing and recruiting fatty acid synthase (FASN) and ATGL to promote LD mobilization. Meanwhile, the core protein interacts with mitochondria, linking mitochondria to LDs and facilitating the release of FAs for efficient fatty acid oxidation. Collectively, this study demonstrates that the BVDV core protein regulates cellular lipid metabolism to support BVDV replication, contributing to understanding the pathogenetic mechanisms by which BVDV interacts with host cells.

Epizootic hemorrhagic disease virus (EHDV) is an important Orbivirus transmitted by culicoides midges. EHDV poses a significant threat to ruminant production worldwide. The VP7 protein is a highly conserved, group-specific antigen of EHDV, which serves as a key target for serological diagnosis. In this study, the recombinant VP7 (r-VP7) protein of EHDV-1 was expressed in an Escherichia coli expression system and used to immunize BALB/c mice. Four hybridoma cell lines secreting monoclonal antibodies (mAbs) against VP7 were successfully generated by the hybridoma technique, and named 5D1, 6A7, 7B11, and 7C4. Indirect ELISA, western blot analysis, and immunofluorescence assays demonstrated that all four mAbs specifically recognized both the r-VP7 protein and the native VP7 protein in EHDV-1-infected BHK-21 cells, with favorable reactivity and specificity. The VP7 protein was progressively truncated and expressed as a series of GST fusion proteins, and the linear B-cell epitopes recognized by these mAbs were precisely identified by western blotting. The results showed that 5D1 and 7B11 recognized the epitope [83]DYIQNLATIGVLATPEI[99], 7C4 recognized [121]PDRQPFGYFL[130], and 6A7 recognized [229]APVNVNNPGQ[238]. Sequence alignment and cross-reactivity assays revealed that the three epitopes were highly conserved among EHDV serotypes and showed no cross-reactivity with the VP7 proteins of African horse sickness virus (AHSV) or bluetongue virus (BTV). Three-dimensional structural analysis indicated that all three epitopes were exposed on the surface of the VP7 trimer and were located in distinct structural domains. In summary, this study successfully generated four specific mAbs against the EHDV VP7 protein and identified three novel linear B-cell epitopes, providing a foundation for the development of specific EHDV serological diagnostic methods and epitope-based vaccines.

Animal coronaviruses are associated with serious diseases in livestock and poultry, resulting in substantial economic losses worldwide. Antibody-dependent enhancement (ADE) is a phenomenon whereby pre‑existing pathogen specific antibodies may paradoxically exacerbate viral infections. In this review, we synthesize current classifications of ADE mechanisms, presenting a unified framework comprising two major categories subdivided into five distinct mechanistic subsets. Given the limited research on ADE in animal coronaviruses, we use SARS‑CoV‑2 as a case study to explore five potential ADE mechanisms associated with coronavirus infection. This review aims to provide a valuable reference for elucidating ADE mechanisms in animal coronaviruses.

The intestinal epithelium is crucial for nutrient absorption, immune defense, and barrier function in farmed fish. However, the molecular mechanisms underlying its development and maturation in salmonids remain poorly characterized, hindering our ability to address pervasive gut health challenges in aquaculture. In this study, we use the RTgutGC cell line to implement an epithelial maturation model with the aim of characterizing the global transcriptional program in rainbow trout (Oncorhynchus mykiss). We evaluated in vitro culture conditions to generate a polarized epithelial barrier with high transepithelial electrical resistance (TEER = 75.8 Ω × cm2), low permeability (6.2 × 10-6 cm/s), and well-defined apical specializations, including microvilli-like structures and clusters of these structures (brush border). Comparative transcriptomic profiling between immature (7 days post-seeding, dps) and mature (28 dps) epithelia revealed 3,817 differentially expressed genes (DEGs). Functional enrichment analysis showed that maturation was characterized by the downregulation of proliferative and ribosomal pathways and the concerted upregulation of processes critical for barrier function, including transmembrane transport, proteolysis, cell adhesion, extracellular matrix organization, and tight junction assembly. We identified a core set of 60 genes indicators of epithelial maturation, encompassing solute transporters (slc26a6, slc43a2), tight junction proteins (tjp1, cldn1, cldn3, cldn5, cldn18, among others), and structural components essential for microvilli formation and polarization (cdhr5b, pard6a). By integrating ultrastructural, functional, and transcriptomic data, this study established a framework for future mechanistic investigations into gut development and maturation in vitro. This set of mature epithelium indicators has diverse applications, such as the design of nutritional and pharmacological interventions to improve gut health and resilience in farmed fish.

Pseudorabies virus (PRV) causes Aujeszky's disease, posing an emerging threat to the livestock industry and raising concern for human health. Host cells employ a wide range of intrinsic factors to combat viral infections; however, the host factors involved in restricting PRV entry remain poorly understood. In this study, using both human and porcine cell models, we identified a potent antiviral role of LY6E (lymphocyte antigen 6, family member E) in suppressing PRV infection. Overexpression of LY6E resulted in a significant reduction in PRV infection, whereas depletion of LY6E increased infection, supporting a promising antiviral role against PRV. Structure-function analyses identified that the proper structure of LY6E is indispensable for its full antiviral activity. Transcriptomic analysis revealed that LY6E modulates specific host signaling pathways during PRV infection without triggering global transcriptional alterations. Furthermore, LY6E was found to interact with PRV envelope glycoproteins, implying its role in regulating viral entry. Subsequent investigations revealed that LY6E does not interfere with the initial attachment of PRV to host cells but specifically impairs viral internalization. Collectively, this study identifies LY6E as a previously unrecognized host restriction factor for PRV and highlights the role of surface proteins in controling viral entry. Additionally, it broadens the antiviral spectrum of LY6E to DNA viruses, beyond its previously reported host-viral interaction in RNA viruses.

Brucella is a Gram-negative facultative intracellular pathogen that causes widespread zoonotic infections. Macrophages are crucial immune and antigen-presenting cells that differentiate into proinflammatory M1-type or anti-inflammatory M2-type cells in different microenvironments. The BtpB protein of Brucella is a type IV secretion system effector protein that modulates host inflammatory responses by inhibiting Toll-like receptor signaling and controlling dendritic cell activation. A high expression of intracellular proinflammatory factors is induced in B. suis deficient in BtpB (B. suis mutant strain ΔbtpB). However, the role of BtpB in macrophage polarization triggered by Brucella infection is uncertain. In this study, RAW264.7 macrophages were utilized as a model to investigate the impact of BtpB on macrophage polarization. The cells were infected with wild-type B. suis strain S2, B. suis mutant strain ΔbtpB, or the B. suis complemented strain C-ΔbtpB followed by flow cytometry, reverse transcription quantitative PCR (RT-qPCR), western blotting, immunohistochemistry, and metabolic detection analyses. The expression of BtpB suppressed M1 polarization and promoted M2 macrophage polarization. Moreover, BtpB upregulated the expression of signal transducer and activator of transcription 3 (STAT3) in host cells. Inhibition of STAT3 promoted the expression of nitric oxide synthase (NOS2) in cells infected with either B. suis or C-ΔbtpB, with no observable differences compared to cells infected with ΔbtpB. Conversely, STAT3 overexpression resulted in a downregulation of NOS2 levels in both wild-type and mutant cells. These findings were corroborated by messenger RNA (mRNA) assay and enzyme-linked immunosorbent assay (ELISA) that confirmed the regulatory role of STAT3 in modulating NOS2 expression. Additionally, intracellular proliferation assays under STAT3-modulated conditions indicated that STAT3 suppresses replication of Brucella. In conclusion, the results demonstrate that BtpB inhibits M1 polarization in macrophages by regulating STAT3 expression which provides a strong foundation for improved understanding of Brucella infection mechanisms.

Porcine genital chlamydiosis is considered a potential cause of reproductive failure, with Chlamydia (C.) suis being the most prevalent chlamydial species. To assess its pathogenic relevance, 50 Austrian piglet-producing farms were investigated: 40 farms with reproductive disorders (20 with tetracycline-treatment (tet), 20 without (no-tet)) and 10 clinically unaffected control farms. Samples from 770 sows (tet: n = 333, no-tet: n = 337, control: n =100) including blood, cervical and rectal swabs, dust samples and one pooled nursery fecal sample per farm were analyzed. Thirty-seven reproductive-tracts and six abortion cases were examined. Species-specific real-time PCR detected cervical C. suis shedding in 2.1% of sows (tet: n =5, no-tet: n = 10, control: n = 1). Rectal shedding was found on 45 farms and in 39.7% of sows overall (tet: n = 37.8%, no-tet: n = 39.2%, control: n = 48%). C. pecorum DNA was identified in one cervical and seven rectal swabs. Chlamydiaceae-specific antibodies were detected by complement fixation test on all farms and in 49.8% of sows overall, without association between study group and shedding or serological status. C. suis DNA was detected in 28% of dust and 96% of nursery fecal samples, whereas reproductive tract and abortion material were largely PCR-negative. Analyzing 42 C. suis isolates high rates of tetracycline resistance were found in all study groups via tetA(C) PCR (tet: n = 93.75%, no-tet: n = 78.3%, control: n = 100%) and in vitro susceptibility testing (tet: n = 75%, no-tet: n = 60.8%, control: n = 100%). Parity had negative effects on clinical signs, rectal shedding and antibody expression. C. suis appears to play a limited role in reproductive failure, while routine tetracycline treatment should be critically reconsidered due to frequent resistance.

Streptococcus suis is a major zoonotic pathogen, and strains originating from clinically healthy pigs pose an increasingly serious threat to human health. This study investigated 315 S. suis isolates collected from clinically healthy pigs in Guangdong and Guangxi provinces between 2024 and 2025. Among these isolates, 34 capsular polysaccharide (cps) types were identified, with 40.63% belonging to cps types associated with human infections. The isolates exhibited high genetic diversity, distributed across 80 sequence types (STs), 13 clonal complexes (CCs), and five minimum core genomes (MCGs). Animal infection models demonstrated that a considerable proportion of healthy-pig-derived strains displayed high virulence in zebrafish and mouse models. Cytotoxicity assays confirmed that isolates belonging to CC1, CC7, CC17, CC94, and CC108 caused significant cytotoxicity toward A549 and hBMEC cells. Alarmingly, 96.82% of the isolates were multidrug-resistant, and notably, 29.84% showed resistance to penicillin. Furthermore, various integrative and conjugative elements (ICEs) and prophages were identified in these strains. Homology analysis revealed that ICEs carried by highly virulent healthy-pig-derived strains shared high similarity with those from highly virulent human-derived strains and even human-derived Streptococcus agalactiae, raising concerns about the possible dissemination of virulence-associated determinants via ICEs. This study highlights the emergence of multidrug-resistant and highly virulent S. suis strains in healthy pig populations. The dual threat of pathogenicity and antimicrobial resistance, coupled with the horizontal gene transfer capacity of ICEs and prophages, constitutes a serious public health risk, underscoring the urgent need for enhanced surveillance.

The first epidemic of lumpy skin disease (LSD) in France was detected in June 2025, with a total of 117 outbreaks recorded by the end of the year. This fast-spreading vector-borne disease of cattle prompted the implementation of strict control measures, including total depopulation of affected herds, resulting in the culling of more than 3500 cattle. Over the course of the epidemic, this measure became increasingly unacceptable, leading to major protests. To contribute to this veterinary public health debate, we present a mathematical model, accounting for both cattle and vector populations, that compares within-herd transmission dynamics under selective or total depopulation strategies, and different vector control scenarios. The selective depopulation strategies are modelled based on a bi-daily test-and-cull approach implemented upon detection of the first clinical case in an unvaccinated herd, with imperfect diagnostic tests capable of detecting infection in asymptomatic cattle under different assumptions of test sensitivity and of time from infection to detectability. Our model shows that the selective culling strategy is insufficient to control the spread of the disease in the absence of vector population control, with the entire herd eventually becoming infected. In the best-case scenario with highly sensitive and timely diagnostic tests and an 80% reduction of the vector population, still 75% (95% simulation interval: 26, 100) of the herd becomes infected. Assuming more realistic diagnostic tests (30% sensitivity for detecting subclinical animals within 2-3 days before the onset of infectiousness), the model predicts that 94% of the herd (95% simulation interval: 44, 100) eventually becomes infected, representing only a marginal improvement over a total depopulation strategy.